NASDAQ: SLS

In December 2020, we entered into an exclusive license agreement, or the 3D Medicines Agreement, with 3D Medicines Inc., or 3D Medicines, a China-based biopharmaceutical company developing next-generation immuno-oncology drugs, for the development and commercialization of GPS, as well as the Company’s next generation heptavalent immunotherapeutic GPS+, which is at preclinical stage, across all therapeutic and diagnostic uses in mainland China, Hong Kong, Macau and Taiwan, which we refer to as Greater China. We have retained sole rights to GPS and GPS+ outside of Greater China. In November 2022, we announced that we had agreed with 3D Medicines for 3D Medicines to participate in the REGAL study through the inclusion of approximately 20 patients from mainland China. In December 2022, we entered into a Side Letter Agreement with 3D Medicines, or Side Letter, which together with the 3D Medicines Agreement, details the terms and conditions of 3D Medicines' participation in the REGAL study. Although the REGAL study has completed enrollment as announced in March 2024, in accordance with the predetermined statistical analysis plan, 3D Medicines may still enroll patients in mainland China. The timing of such participation and patient enrollment by 3D Medicines, if at all, cannot be predicted with certainty. As of December 31, 2025, we have received an aggregate of $10.5 million in upfront and milestone payments under our license agreement with 3D Medicines, or the 3D Medicines Agreement, and a total of $191.5 million in potential future development, regulatory and sales milestones, not including future royalties, remains under the license agreement, which milestones are variable in nature and not under our control. In December 2023, we announced that we had commenced a binding arbitration proceeding against 3D Medicines to

4

Table of Contents

resolve a dispute regarding, among other things, the trigger and payment of relevant milestone payments due to us under the 3D Medicines Agreement. See Item 3. Legal Proceedings.

GPS was granted Orphan Drug Designations, or ODD, from the FDA, as well as orphan medicines designations from the European Medicines Agency, or EMA, in AML, malignant pleural mesothelioma, or MPM, and multiple myeloma, or MM, as well as Fast Track designations for AML, MPM, and MM from the FDA. In October 2024, the FDA granted Rare Pediatric Disease, or RPD, designation to GPS for the treatment of pediatric AML.

SLS009: Highly Selective Next Generation CDK9 Inhibitor

On March 31, 2022, we entered into an exclusive license agreement, or the GenFleet Agreement, with GenFleet Therapeutics (Shanghai), Inc., or GenFleet, a clinical-stage biotechnology company developing cutting-edge therapeutics in oncology and immunology, that grants rights to us for the development and commercialization of SLS009, a highly selective small molecule CDK9 inhibitor, across all therapeutic and diagnostic uses worldwide, except for Greater China.

CDK9 activity has been shown to correlate negatively with OS in a number of cancer types, including hematologic cancers, such as AML and lymphomas, as well as solid cancers, such as osteosarcoma, pediatric soft tissue sarcomas, melanoma, endometrial, lung, prostate, breast and ovarian. As demonstrated in preclinical and clinical data, to date, SLS009’s high selectivity has the potential to reduce toxicity as compared to older CDK9 inhibitors and other next-generation CDK9 inhibitors currently in clinical development and to potentially be more efficacious.

We completed a Phase 1 dose-escalating clinical trial in the United States and China for SLS009 in mid-2023 and reported positive safety and efficacy data for both patient cohorts, that is relapsed and/or refractory AML and refractory lymphoma. We also established in the trial a recommended Phase 2 dose, or RP2D, of 60 mg once weekly or 30 mg twice weekly for AML and 100 mg once weekly for lymphomas.

In the second quarter of 2023, we commenced an open label, single arm, multi-center Phase 2a clinical trial with SLS009 in combination with venetoclax and azacitidine, or aza/ven, in patients with AML who failed or did not respond to treatment with venetoclax-based therapies. The trial evaluated safety, tolerability, and efficacy at two dose levels of SLS009, 45 mg once weekly, and 60 mg once weekly or 30 mg twice a week, in combination with aza/ven. In December 2024, we announced positive data from the first 3 cohorts in the Phase 2a trial.

In July 2025, we announced that the Phase 2 trial of SLS009 in r/r AML met all primary endpoints and received FDA guidance to advance into a first-line therapy study. The overall response rate, or ORR, in 54 evaluable patients was 33% across all cohorts and dose levels, 40% for the 30 mg BIW dose level, and 44% in the 30 mg BIW dose among patients with myelodysplasia-related molecular mutations, or AML MR, all exceeding the pre-specified ORR threshold of 20%. The highest efficacy was observed among patients with ASXL1 mutations, with an ORR of 50% (9/18) at 30 mg BIW dose levels, and AML MR with Myelomonocytic/Myelomonoblastic markers, or M4/M5 per FAB classification, patients with an ORR of 50% (6/12). The median overall survival, or mOS, reached 8.9 months in patients with AML MR and 8.8 months in patients r/r to venetoclax-based regimens at a 30 mg BIW dose level, surpassing the historical benchmark of ~2.4 months. SLS009 was well-tolerated with no new safety signals observed. No dose-limiting toxicities were observed across all dose levels.

Following a productive end of Phase 2 meeting, the FDA recommended that we proceed into a clinical trial to include newly diagnosed, first-line AML patients eligible for aza/ven therapy, where the FDA noted clinical benefit might be greatest. The randomized 80-patient Phase 2 clinical trial is currently ongoing and began enrollment in the first quarter of 2026. The clinical trial will include two groups: predictive biomarker cohort (newly diagnosed patients unlikely to benefit from standard aza/ven therapy based on molecular profiling) and early venetoclax resistance cohort (patients who initiate treatment with aza/ven, but demonstrate confirmed lack of any response after two treatment cycles).

In January 2026, we announced that we entered into an agreement with IMPACT-AML, a European collaborative initiative dedicated to advancing innovative treatments for patients with AML. Under the agreement, the IMPACT-AML network will conduct a clinical study evaluating SLS009, enabling access to multiple European clinical sites and patients. IMPACT-AML is a pan-European project and builds an inclusive clinical network (STREAM platform)

5

Table of Contents

that connects patients, clinicians, and researchers to test novel AML therapies and improve patient outcomes. It is part of the prestigious EU Mission Cancer program and a top-tier scientific cluster. The IMPACT-AML project is led by a consortium of major research and clinical institutions in Europe, including IRST (IRCCS Istituto Romagnolo per lo Studio dei Tumori “Dino Amadori”), the University of Bologna, IIS LA FE (Health Research Institute Hospital La Fe), several European AML collaborative groups, and supranational organizations under the umbrella of the European Leukemia Net (ELN), as well as various university hospitals across Europe. By leveraging IMPACT-AML’s existing infrastructure and expertise, we expect to expand European patient access to SLS009 in a highly cost-efficient manner while supporting broader participation across the clinical program.

In November 2024, we announced data from preclinical studies identifying ASXL1 mutation as key predictor of SLS009 in response to solid cancers.

In May 2025, we announced data for pediatric acute lymphoblastic leukemia, or ALL, patients derived xenografts, or PDX. The experiment conducted and funded by the National Institute of Health, or NIH, through the NCI Pediatric Prelinical in Vivo Testing, or PIVOT, program, included 27 patient-derived ALL tumors from pediatric patients. Tumors were xenografted in mice in two groups, vehicle control arm and SLS009 arm. Mice were treated with a fractionated dose once per week for six consecutive weeks. Treatment was well tolerated. For all models, median survival was approximately tripled in the SLS009 arm, compared to vehicle control arm. SLS009 demonstrated delayed progression in 25/27 (93%) models and more than two times longer time to progression in 15/27 (56%) of ALL models. In addition, there were complete responses, or CR, in two models and in one of the two models CR was maintained after the treatment had been completed until the end of the study (four months). Among seven KMT2A rearranged models, time to progression was extended in all seven models, and in six out of seven (86%) time to progression was more than doubled.

For SLS009, the FDA granted Orphan Drug Product designations in AML and peripheral T-cell lymphoma, or PTCL, and Fast Track designations for r/r AML and r/r PTCL. The FDA granted RPD designation to SLS009 for the treatment of pediatric acute lymphoblastic leukemia, or ALL, in June 2024 and the FDA granted RPD designation to SLS009 for the treatment of pediatric AML in July 2024. Also, the European Medicines Agency granted Orphan Drug Designation for SLS009 in AML and in PTCL in June 2024 and July 2024, respectively.

The chart below summarizes the current status of our clinical development pipeline:

6

Table of Contents

Our Strategy

Our overall goal is to develop multiple oncology product candidates in order to achieve marketing authorization in the United States and the rest of the world. We are particularly focused on developing better treatments for AML, the lead indication for both GPS and SLS009, which will allow us to leverage our clinical development expertise in hematology/oncology and to build a single streamlined commercial infrastructure sufficient for both of our current product candidates.

Products/Pipeline

Galinpepimut-S (GPS): Innovative WT1 Targeting Immunotherapy

Overview

GPS is a WT1-targeting peptide-based cancer immunotherapeutic being developed as a monotherapy and in combination with other therapeutic agents to treat different types of cancers that result from uninhibited tumor cell growth. GPS targets malignancies and tumors characterized by an overexpression of the WT1 protein. The WT1 protein is one of the most widely expressed cancer proteins in multiple malignancies. A previous pilot project regarding the prioritization of cancer antigens (substances that evoke an immune response) conducted by the National Cancer Institute, or NCI, a division of the National Institutes of Health, or NIH, ranked the WT1 protein as a top priority for immunotherapy.

WT1 is a protein that resides in the cell’s nucleus and participates in the process of cancer formation and progression. As such, WT1 is classified as an “oncogene.” WT1 plays a key role in the development of the kidneys in fetal life, but then almost disappears from normal organs and tissues. In approximately 20 cancer types, WT1 becomes detectable again in at least 50% of tumor pathology specimens in the cells of these cancers. WT1 appears in large amounts (i.e., becomes “overexpressed”) in numerous hematological malignancies, including AML, MM and chronic myeloid leukemia, as well as in many solid malignancies such as MPM, gastrointestinal cancers (such as colorectal cancer), glioblastoma multiforme, triple negative breast cancer, or TNBC, ovarian cancer and small cell lung cancer, or SCLC.

Mechanism of Action in Immune System

GPS is a multi-peptide product that has been modified to enhance the degree and duration of the immune response against the WT1 protein. Two of the four peptides in the peptide mixture comprising GPS are deliberately mutated in a single amino acid residue. These mutated peptides are recognized by the immune system as non-self entities and are therefore less likely to induce immune tolerance. These mutated peptides are designed using artificial intelligence, or AI, by researchers at MSK, to elicit strong T-cell response against both mutated peptides and naturally occurring peptides in cancer cells. This concept is called the heteroclitic principle.

We believe that GPS has a mechanism of action that involves direct activation of the patient’s immune system specifically against the WT1 protein. Although the immune system is designed to identify foreign or abnormal proteins expressed on tumor cells, this process is often defective in cancer patients. Typically, patients harboring WT1-positive malignancies have very few or no T-cells specifically reactive or responsive to, and therefore activated by, WT1. T-cells are involved in both sensing and killing abnormal cells, in addition to coordinating the activation of other cells in an immune response. T-cells can be classified into two major subsets, CD4 cells and CD8 cells. CD8 cells, often called cytotoxic T-cells, are characterized by the expression of the CD8 protein on their cell surface. Once activated, cytotoxic T-cells recognize, bind and kill cancer cells marked by abnormal proteins. CD4 cells, known as helper T-cells, are critical to providing the signals necessary for sustained CD8 cell responses and are also capable of exerting direct anti-tumor activity. GPS is designed to elicit both CD4 and CD8 cell immune responses. We believe that the activation of CD8 cells by GPS could lead to direct cancer cell killing, or cytotoxicity, and the eventual establishment of immunologic memory against a WT1-expressing cancer. This occurs by two mechanisms: (i) conversion of some of the activated CD8 cells to memory CD8 cells, and (ii) activation of CD4 cells and the eventual creation of CD4 terminal effector memory cells.

7

Table of Contents

GPS' proposed mechanism of action is based on the induction and stimulation of T-lymphocytes, both cytotoxic CD8 cells – which are attacking the tumor directly – and CD4 cells, which are very important for immunologic memory, maintenance, and helper function of the cellular immune response. Two of the peptides within the GPS mixture are native, meaning that they contain the exact same amino acid (AA) sequences as the fragments of the wild type (unmutated) WT1 protein they originated from. The remaining two peptides are by design modified by a single point AA mutation. In that sense, the heteroclitic WT1 peptide carries a mutation and is presented to the native CD8+ cell through the host’s antigen-presenting cells - macrophages, dendritic cells or B cells. The CD8+ cell is reprogrammed and activated, thus becoming a cytotoxic T-cell specifically against the target antigen, and now may recognize not only the mutated version of the WT1 peptide (against which the host was immunized, and which does not get expressed naturally), but also the corresponding native WT1 fragment. The native fragment could get expressed and presented on the membrane of cancer cells in an MHC Class I context. Similar events occur in CD4+ cells after cross-presentation of the WT1 heteroclitic fragment and eventual activation of the CD4+ cells into effector and memory cells. The heteroclitic technology mitigates against the emergence of tolerance, as the mutated peptides are classified as ‘non-self’ antigens.

GPS is given under the skin, or subcutaneously, after mixing with Montanide™ an adjuvant, which creates a reservoir of GPS in a water in oil emulsion. Additionally, prior to the administration of GPS, patients receive another immune adjuvant, granulocyte-macrophage colony-stimulating factor, or GM-CSF, to non-specifically stimulate and activate antigen-presenting cells, or APCs, in the vicinity of the subcutaneously injected GPS.

As mentioned earlier, after subcutaneous injection, the WT1 peptides are ingested by APCs at the local injection sites. Antigen presenting cells migrate to lymph nodes where the ingested peptide fragments are then presented on the surface of APCs to CD8 and CD4 T-cells though major histocompatibility complex class II, (MHCII), where they can bind to T-cell receptor, (TCR). This process activates the CD4 and CD8 cells and sensitizes them to the key 25 epitopes of WT1, thus initiating the process of short- and long-term T-cell-mediated immunity against WT1.

8

Table of Contents

Key Features

The following table summarizes the key features of GPS:

Key features of an Optimal Cancer

Active Immunizer Therapeutic
GPS Properties and Clinical Strategy

Selecting the right target antigen and

epitopes within that antigen
Four peptides and 25 epitopes selected optimally with the objective of ensuring:

- optimal MHC complex presentation;

- specificity across different HLA types;

- activation of both CD4 and CD8 T-cells; and

- enhancing immune response and overcoming tolerance (the heteroclitic principle).

Optimal T-cell engagement leading to

cancer cell destruction
Immune response data from the final analysis of the Phase 1 clinical study of GPS in MM in 12 evaluable patients that were presented at the 44th Annual Meeting of the European Society for Blood and Marrow Transplantation, or EBMT, in 2018 (Dr. Kohne et al.) showed 75% frequency of either CD8+ or CD4+ responses to an all-pool mixture of WT1-derived antigens after completion of the 12 vaccinations per the study protocol. This evidence of multi-epitope, broad cross-reactivity along the full-length of the WT1 protein is suggestive of epitope spreading, as it emerged across epitopes against which the patients were not specifically immunized. These data corroborate the results of an earlier analysis in mid-2017 and strongly suggest stimulation of T-cells towards intracellular antigen fragments from GPS-induced destruction of tumor cells, which effect is a hallmark of an effective vaccine, e.g., that it is targeting the right epitopes chosen by design.

Overcoming the barriers of an

adverse/immunosuppressive tumor

micro-environment, or TME
The GPS monotherapy clinical studies are in the setting of complete remission, or CR, and minimal residual disease, or MRD, whereby no bulky or measurable tumor deposits exist. This is typically seen after successful frontline therapy in select cancer types for which such debulking standard therapies exist (e.g., AML or MPM). In these settings, the tumor micro-environment, or TME, is substantially absent. We are also pursuing combination therapy with checkpoint inhibitors in tumor settings whereby measurable disease exists, as contemporaneous checkpoint inhibition would abrogate the immunosuppressive effects of the TME.

Overcoming or mitigating immune

toleranceHeteroclitic peptides are those in which mutations have been deliberately introduced in the amino acid sequence. The use of heteroclitic peptide in an active immunizer, such as GPS, increases immunogenicity without changes in the antigenicity profile, as well as strengthens MHC binding of the peptide to produce cytotoxic CD8 cells that continue to recognize the corresponding native peptide sequence. This is believed to be a key factor differentiating GPS from essentially all previously developed peptide vaccines, and applies a highly innovative technology platform, peptide heteroclicity, in a clinical late-stage cancer immunotherapeutic candidate product.

Addressing the broadest possible

candidate patient populationGPS has activity across multiple HLA types that could allow treatment of a vast majority of global patient populations harboring WT1-positive malignancies.

9

Table of Contents

Potential Key Differentiators

GPS’ potential key differentiators as compared to other active immunization or vaccine-type approaches, as well as compared to immunotherapy approaches more generally, are as follows:

•heteroclitic peptides may offer increased immune response and less potential for tolerance;

•multivalent oligopeptide mixture potentially drives differentiated immunotherapeutic efficacy, targeting 25 key epitopes of WT1;

•potentially applicable to 20 or more cancer types worldwide and the vast majority of HLA types;

•CR or MRD status (after initial tumor debulking with preceding standard therapy) is the preferred setting for GPS monotherapy;

•not directly competitive with current clinical standard of care therapies, but rather believed to complement them in the maintenance setting;

•potential for combination approaches with other cancer immunotherapies, due to tolerable adverse event profile;

•anticipated cost-effective manufacturing; allogeneic, “off-the-shelf,” vialed subcutaneously administered drug that is not patient-specific; and

•positive Phase 2 clinical data on effectiveness (based on OS in AML and PFS in MM) with good tolerability and a favorable safety profile.

10

Table of Contents

Development Program for GPS

GPS has the potential as a monotherapy or in combination with other immunotherapeutic agents to address a broad spectrum of hematologic, or blood, cancers and solid tumor indications. We are currently exploring the potential role for GPS in both monotherapy and in combination therapy with checkpoint inhibitors such as PD-1 inhibitors as set forth in the table below:

ProgramStatus

GPS Monotherapy

•Registrational Phase 3 REGAL open-label randomized clinical trial in AML patients who have achieved hematologic complete remission, with or without thrombocytopenia (CR2/CRp2), after second-line antileukemic therapy and who are deemed ineligible for, or unable to undergo, allogeneic stem-cell transplantation
Ongoing

•Phase 1 clinical trial of 3D189 (GPS) in China (our licensee, 3D Medicines is the sponsor)
Completed; final data report pending

•Phase 1 clinical trial in patients with hematologic and thoracic malignancies with no demonstrable residual/recurrent disease after debulking therapy
Completed; final data reported

•Phase 2 clinical trial in patients with AML with first complete remission (CR1) patients
Completed; final data reported

•Phase 2 clinical trial in patients with high-risk MDS or AML patients with ≥2 lines of prior therapy (CR2)
Completed; final data reported

•Phase 2 clinical trial in MM patients
Completed; final data reported

•Phase 2 randomized, double-blind, placebo-controlled clinical trial in MPM patients
Completed; final data reported

GPS Combination Therapy

•Phase 1/2 clinical trial of GPS in combination with the anti-PD-1 therapy pembrolizumab (Keytruda) in ovarian cancer (second or third line) in collaboration with a Merck & Co., Inc., Kenilworth, N.J., U.S. subsidiary (known as MSD outside the United States and Canada), or Merck
Completed; final data reported

•Phase 1 open-label investigator-sponsored clinical trial of GPS, in combination with Bristol-Myers Squibb’s anti-PD-1 therapy, nivolumab (Opdivo), in patients with MPM who harbor relapsed or refractory disease after having received frontline standard of care multimodality therapy
Completed; final data reported

•Phase 1/pilot open-label, non-randomized clinical trial of GPS in combination with nivolumab in patients with WT1-expressing, or WT1+, recurrent ovarian, fallopian tube or primary peritoneal cancer who were in second or greater clinical remission (after their successful first or subsequent “salvage” therapy)
Completed; final data reported

11

Table of Contents

Current AML Treatment Therapies

AML is an aggressive and potentially lethal blood cancer characterized by the rapid growth of abnormal white blood cells that build up in the bone marrow and interfere with the production of normal blood cells. Its symptoms include fatigue, shortness of breath, bruising and bleeding, and increased risk of infection. The cause of AML is unknown, and the disease is typically fatal within weeks or months if untreated. AML most commonly affects adults, and its incidence increases with age.

A June 2021 report from Delvelnsight estimates a global market size for AML of $5.09 billion by the end of 2030, with a compound annual growth rate, or CAGR, of 21.85% from 2018 to 2030. The total number of newly diagnosed patients with AML per year in the United States is approximately 20,050 (2022 epidemiological data: American Cancer Society). According to PharmaIntelligence (Informa, April 2022) as AML patients progress through their individual journeys and experience disease progression, the number of patients that ultimately receive a second-line treatment of any kind in the U.S. is roughly 36% (about 7,500 patients) of the stated incident population. The corresponding numbers of second-line treated patients in the key markets of the European Union (Germany, France, Italy and Spain) is approximately 6,520 and of Japan is approximately 3,482. According to CD DiNardo (N Engl J Med 2018; 378:2386-2398) and D Verma (Leuk Lymphoma 2010 May;51(5):778-82), about 50% of patients in second-line achieve complete remission, or CR2 (our Phase 3 REGAL patient population). These figures would substantiate a total of approximately 8,750 clinically appropriate patients for GPS in the referenced key markets.

Until recently, the overall treatment landscape for AML had remained static for decades, as numerous targeted and antiproliferative agents were unsuccessful in providing meaningful long-term clinical benefits, including increments in survival. In recent years, additional drugs have been approved and current standard treatments include chemotherapy (including the fixed molar ratio combination chemotherapy Vyxeos), hypomethylating agents, or HMAs, drugs that target mutations of the isocitrate dehydrogenase type-1 and -2 and the FMS-like tyrosine-protein kinase, FLT3, in patients whose disease harbors these genetic aberrations, the B-cell lymphoma 2 inhibitor venetoclax (in combination with chemotherapy or HMAs), the CD33-targeting antibody-drug conjugate gemtuzumab ozogamicin, and the sonic hedgehog signaling inhibitor glasdegib. Select patients could also undergo an allogeneic hematopoietic, or blood-forming, stem cell transplant, referred to as allo-HSCT. One of the fundamental goals of therapy for AML, both in the upfront and salvage settings, is for the patient to achieve a state of complete remission. Complete remission is defined per consensus criteria by the European Leukemia Net, or ELN, whereby the hematologic and clinical features of the disease are no longer detected. In the first line setting, AML patients who achieve a status of first complete remission, or CR1, have two options for a meaningful long-term benefit: allo-HSCT and maintenance therapy with the oral form of the HMA azacitidine, which the FDA approved for use in the second half of 2020. In the second line setting, i.e., in AML patients who have relapsed and are receiving salvage antileukemic therapy, we are not aware of any therapies, other than allo-HSCT, that have shown through rigorous blinded, randomized, controlled clinical trials to offer a meaningful long-term benefit (either relapse-free or OS) when used as maintenance after patients achieve a status of CR2. Once the disease relapses after second-line therapy, patients have limited options which currently include off-label administration of HMAs, venetoclax in combination with either HMAs or low-dose cytarabine or investigational agents in the context of a Phase 1/2 clinical trial.

AML as lead indication for GPS Program

We chose AML, for which we have been granted Fast Track and ODD by the FDA, as our lead indication for GPS for the reasons outlined below:

•AML presents a clinical setting in which complete remission status (specifically CR1 and/or CR2) can be achieved with standard antileukemic therapy;

•the high degree of unmet medical need in recurrent/relapsed AML and the absence of an effective maintenance therapy over the decades after salvage re-induction until and immediately after achievement of CR2 status, especially considering that most patients in this clinical scenario are older than 60 years of age;

12

Table of Contents

•the almost universal expression of WT1 in leukemic blasts, which are AML’s replicating malignant cells, as well as leukemic stem cells, or LSCs, cells that are or become extremely resistant to standard chemotherapy or targeted agent approaches and which can be realistically eradicated only with immunotherapy methods (including allo-HSCT). LSCs have been shown to be susceptible to targeting by cytotoxic T-cells (CD8 and CD4 cells) stimulated against leukemia-associated antigens and we believe this will be the case for GPS;

•the fact that WT1 has been associated with the actual development of leukemia;

•the positive correlation between the level of expression of WT1 and the prognosis in AML;

•the fact that the level of expression of WT1 can be followed over time in patients during and after therapy, including immunotherapy, as a method of monitoring for MRD;

•early evidence from mouse models that vaccination with peptides against select WT1 antigenic epitopes leads to detection of immune response;

•early evidence that human immunocytes sensitized ex-vivo to peptides contained in GPS were able to recognize naturally presented WT1 peptides on the surface of several leukemia cell lines;

•early anecdotal (at the time) clinical data showing antileukemic activity of WT1 monovalent vaccines in the CR1 maintenance setting in the Japanese population (albeit restricted to HLA-A*2401 type), as well as a dendritic cell vaccine in the Netherlands (independent of HLA haplotype) in the same setting;

•a predictive assumption of very low to negligible degree of clinical toxicity with a WT1-targeted immunotherapy such as GPS, due to the fact that WT1 in normal, non-cancerous, tissues is both expressed at extremely low levels and limited in number of organs and tissues, but also due to the fact that WT1 fragments, or peptide epitopes, in normal cells are presented to host APCs in a different manner than are WT1 fragments produced in cancer cells; of note, WT1 expression in normal tissues of adults is limited to the podocyte layer of the glomerulus (kidney), Sertoli cells (testis), granulosa cells (ovary), decidual cells (uterus), mesothelial cells (peritoneum, pleura), mammary duct and lobule (breast), and blood-forming (hematopoietic) progenitor cells (CD34+ cells in the bone marrow);

•the advent of modern immunotherapeutics in cancer and the promise of an innovative, off-the-shelf potentially effective, low adverse event burden immunotherapy to prevent or delay relapse in patients once they achieve complete remission status in AML, a disease that has historically been associated with dearth of deep and sustained responses to checkpoint inhibitors; and

•evidence from our completed Phase 1 and Phase 2 clinical trials that administration of GPS can lead to extended relapse free survival and OS especially in patients who demonstrated clear WT1 specific CD4 and/or CD8 immune response to GPS administration.

Furthermore, we believe that there is a significant unmet medical need for a clinically safe and effective therapy as maintenance after AML patients achieve CR1 and/or CR2 status following successful first-line or second-line (salvage) therapies, as a significant percentage of these patients are ineligible for, or unable to undergo, allo-HSCT. No third-line therapies have shown demonstrable clinical impact to date in AML patients after their second relapse and eventually AML patients in second relapse generally succumb to AML or complications associated therewith.

Our Clinical Data in AML CR1 and CR2 Patients

In an initial pilot clinical trial in AML, a total of nine adult patients of all ages with de novo AML were treated with upfront standard chemotherapy and were able to achieve CR1. Administration of GPS resulted in a median OS that was at least 35 months from the time of GPS administration. In this study, specifically for patients who were 60 years and older (n=5), median OS was at least 33 months from the time of GPS administration or approximately 43 months from the time of initial AML diagnosis. The mean time of follow-up was 30 months from the time of diagnosis

13

Table of Contents

at the time of this analysis for all patients. Of the eight patients tested for immunologic response, seven, or 87.5%, demonstrated a WT1-specific immune response.

In a subsequent Phase 2 clinical trial in AML, a total of 22 adult patients of all ages with de novo AML were treated with upfront standard chemotherapy and were able to achieve CR1. Most patients also received one to four cycles of “consolidation” chemotherapy per standard AML treatment guidelines. GPS was then administered within three months from the completion of the consolidation chemotherapy regimen in up to 12 total doses: six initial doses (priming immunization) followed by six additional “booster” immunizations over a total period of up to 15 months to qualifying patients (i.e., patients who were clinically stable and did not show disease recurrence after the first six injections). This Phase 2 clinical trial met its primary endpoint of an actual OS rate of at least 34%, measured three years into the clinical trial (i.e., percentage of patients alive after three years of follow-up). An actual OS rate of 47.4% was demonstrated at three years post-GPS treatment, exceeding historical published data of OS of 20% to 25% by 2.4- to 1.9-fold (or 240% to 190%), respectively.

GPS administration was also shown to improve OS in comparison to historical data in patients in CR1. Administration of GPS resulted in a median OS that was poised to exceed 67.6 months from the time of initial AML diagnosis in patients of all ages, which represents a substantial improvement compared to best standard therapy. Only five of the 22 patients underwent allo-HSCT and an ad hoc statistical analysis failed to show a significant effect of the transplant upon OS (either in median survival times or survival rates at specific landmark time-points). In this study, the patients’ median age was 64 years old. Importantly, a preplanned subgroup analysis for the cohort of 13 patients within the clinical trial who were 60 years of age or older demonstrated a median OS of 35.3 months from time of initial diagnosis. Comparable historical populations have a median OS ranging from 9.5 to 16.8 months from initial diagnosis, which represents a 2.25 to 3.75-fold improvement in OS associated with GPS therapy in the CR1 maintenance setting as contrasted to these historical cohorts of broadly comparable patients.

The most frequent toxicities were mild to moderate local skin reactions and inflammation, as well as fatigue, which were self-limited and responded to local supportive measures and analgesics. None of the patients developed significant serious or high grade systemic adverse reactions (including anaphylaxis) attributable to GPS. GPS elicited WT1-specific immune responses in 88% of patients, including CD4 and CD8 T-cell responses. Further, the heteroclitic principle was confirmed, in that immune responses were seen against the native version of the two mutated WT1 peptides within the GPS mixture. The results showed a trend in improved clinical outcomes in patients who mounted an immune response with GPS compared to those patients who did not.

An additional Phase 2 clinical trial of GPS was performed at the H. Lee Moffitt Cancer Center & Research Institute, or Moffitt. This Phase 2 trial included 10 AML patients who had received first-line therapy for their disease, who then experienced relapse and were subsequently treated with second-line chemotherapy and achieved a CR2. This group of patients had a more advanced disease in comparison to those treated in the Phase 2 clinical trial in CR1 patients discussed above and typically demonstrated a historical OS of less than ~8 months, even with post-CR2 allo-HSCT. In the Moffitt trial, the efficacy of GPS (measured as median OS, from the time of achievement of CR2 until death from any cause) was compared with that of “watchful waiting” in a cohort of 15 contemporaneously treated (but not matched by randomization) broadly comparable patients treated by the same clinical team at Moffitt. Initial data, at a median follow-up of 19.3 months, showed that GPS administration resulted in a median OS of 16.3 months (495 days) compared to 5.4 months (165 days) from the time of achievement of CR2. This was a statistically significant difference (p=0.0175). Two of 14 AML patients demonstrated relapse-free survival of more than one year. Both of these patients were in CR2 at time of GPS administration, with duration of their second remission exceeding duration of their CR1, strongly suggesting a potential benefit based on immune response mechanisms.

Final data, at a median follow-up of 30.8 months, showed a median OS of 21.0 months in patients receiving GPS therapy compared to 5.4 months in the AML CR2 patients treated with best standard care resulting in a statistically significant difference (p-value < 0.02). GPS was well-tolerated in this clinical trial.

Phase 3 REGAL Clinical Trial

Building on the Phase 2 study in AML CR2 patients, which showed a median OS of 21.0 months, at a median follow-up of 30.8 months, in patients receiving GPS compared to 5.4 months in contemporaneously treated patients

14

Table of Contents

with best standard therapy, we currently have an ongoing Phase 3 pivotal registration-enabling study for GPS in AML patients in CR2, including those in complete remission with incomplete platelet recovery. This study, which we refer to as the REGAL study, is a 1:1 randomized, open-label study comparing GPS in the maintenance setting to investigators’ choice of best available treatment, or BAT, in adult AML patients (age >18 years) who have achieved their second or later hematologic (morphological) complete remission, with or without thrombocytopenia, after second-line antileukemic therapy and who are deemed ineligible for, or unable to undergo, allo-HSCT. The primary endpoint is OS and secondary endpoints include leukemia-free survival, or LFS, landmark OS and LFS rates, and achievement of MRD negativity. Exploratory endpoints include antigen-specific T-cell immune response dynamics over time. We expect this study will be used as the basis for a BLA submission, subject to a statistically significant and clinically meaningful trial outcome and agreement with the FDA.

The REGAL study was expected to enroll approximately 125 to 140 patients (not including potentially 20-25 patients from mainland China) at approximately 95 clinical sites in North America, Europe and Asia. In March 2024, we announced the completion of enrollment.

The protocol specifies that the study will have a planned interim safety, efficacy and futility analysis after 60 events (deaths). In addition, the charter for the Independent Data Monitoring Committee, or IDMC, for the REGAL study provides that the IDMC may conduct risk-benefit assessments at earlier points in the clinical trial. The IDMC has met several times to perform these prespecified risk-benefit assessments of unblinded data from the study and have recommended in each instance that the trial continue without modifications. In December 2024, we announced that the pre-specified threshold of 60 events (deaths) per the protocol had been reached, triggering the interim analysis to be conducted by the Independent Data Monitoring Committee, or IDMC. In January 2025, we announced that following this interim analysis, the IDMC recommended that the trial continue without modifications. The interim futility, efficacy, and safety analysis is designed to assess whether the therapy is safe, demonstrates potential efficacy, and merits continuation. The IDMC’s review of the interim data supports the continuation of the study according to its original protocol. Based on this positive evaluation, the trial is to advance toward completion. The next and final analysis will be conducted once 80 events (deaths) are reached, further determining the potential of GPS in addressing the needs of AML patients. In December 2025, we announced that our contract research organization informed us that the pooled number of events was 72 as of December 26, 2025. Because the final analysis is event driven, it is difficult to predict with any certainty and it may occur at a different time than currently expected. We will announce the 80th event when it occurs.

We have agreed with our partner in China, 3D Medicines, for 3D Medicines to participate in the REGAL study through the inclusion of approximately 20-25 patients from mainland China. Although the REGAL study has completed enrollment as announced in March 2024, in accordance with the predetermined statistical analysis plan, 3D Medicines may still enroll patients in mainland China. The timing of such participation and patient enrollment by 3D Medicines, if at all, cannot be predicted with certainty. In December 2023, we announced that we had commenced a binding arbitration proceeding administered by the Hong Kong International Arbitration Centre, which proceeding will be governed by New York law as per the terms of the 3D Medicines Agreement. We commenced the proceeding after having exhausted the dispute resolution provisions in the 3D Medicines Agreement to resolve a dispute regarding, among other things, the trigger and payment of relevant milestone payments due to us under the 3D Medicines Agreement as well as 3D Medicines' failure to use commercially reasonable best efforts to develop GPS in accordance with the terms of the agreement. See Item 3. Legal Proceedings.

15

Table of Contents

The key features and schema of this study are shown in the following graphic:

Phase 1 clinical trial of 3D189 in China

In January 2022, 3D Medicines submitted an Investigational New Drug, or IND, application to initiate the first clinical trial in China for 3D189, also known as GPS. The IND for the Phase 1 clinical trial, which is investigating safety, was accepted by China’s National Medical Products Administration, or NMPA, and the trial commenced in mid-2022. 3D Medicines is responsible for all expenses related to executing the trial in China. In the second quarter of 2022, we received a $1.0 million milestone payment which was triggered by the NMPA’s approval of the IND. The study has been completed and the final data report is pending.

Expanded Access Program

At the request of several investigators, in 2022 we instituted an Expanded Access Program for GPS that allows qualified physicians to treat patients who do not meet currently required study entry criteria for the ongoing REGAL trial with GPS. This access is provided on a case-by-case basis to patients in the United States. Patients treated under the Expanded Access Program are not considered participants in the REGAL study. Currently, our Expanded Access Program is available for GPS only.

GPS Combination Therapy with Checkpoint Inhibitors

Phase 1/2 Clinical Trial of GPS in Combination with Pembrolizumab

Given the potential immunobiologic and pharmacodynamic synergy between GPS and an immune check-point inhibitor (e.g., PD-1 inhibitor), we entered into a Clinical Trial Collaboration and Supply Agreement with Merck (known as MSD outside the United States and Canada), to assess the efficacy and safety of GPS in combination with Merck’s anti-PD-1 therapy pembrolizumab with exploratory long-term follow-up for OS and safety. In December 2018, we, in collaboration with Merck, initiated a Phase 1/2 open-label, non-comparative, multicenter, multi-arm clinical trial of GPS in combination with pembrolizumab in patients with WT1-positive advanced cancers, including both hematologic malignancies and solid tumors. We, together with Merck, determined to focus on 2nd or 3rd line WT1+ relapsed or refractory ovarian metastatic cancer as the primary indication for the study.

Ovarian cancer represents an intriguing opportunity to study both the clinical and immunologic effects of GPS in this solid tumor. Additionally, therapeutic targeting of WT1 through immune pathways has largely not been pursued by others to date for this indication and ovarian cancer remains “incurable” once it advances and becomes disseminated, even in the face of significant advances in the field. Ovarian cancer was chosen as a target indication for the following reasons:

•ovarian cancer presents a clinical setting whereby MRD status can be achieved with standard upfront therapy both immediately after first line therapy, but also after effective debulking of the “first relapse.” The

16

Table of Contents

latter subgroup of patients (after successful second line treatment/first salvage, lacking demonstrable macroscopic residual disease) would be optimal candidates for GPS therapy, as no standard maintenance therapy exists for such patients and the subsequent relapse patterns and metrics are known and predictable;

•the high levels of expression of WT1 in ovarian cancer cells. In fact, WT1 expression is so frequent that pathologists routinely use immunohistochemical stains for WT1 (with a standardized convention for describing expression and determining as “positive” or “negative”) to help distinguish epithelial ovarian cancers from other tumors;

•preliminary evidence, in a previous study of GPS with nivolumab in ovarian cancer, that WT1 expression may be linked to prognosis in ovarian cancer and that it may play an anti-apoptotic role in ovarian cancer cell lines;

•the high degree of unmet medical need in ovarian cancer patients after first (or subsequent) successful “salvage” debulking therapy and the absence of effective therapies for such patients; and

•a predictive assumption of very low to negligible degree of clinical toxicity with a WT1-targeted immunotherapy such as GPS due to the fact that WT1 in normal, non-cancerous tissues is both expressed at extremely low levels and limited in number of organs and tissues, but also due to the fact that WT1 fragments, or peptide epitopes, in normal cells are presented to host APCs in a different manner than are WT1 fragments produced in cancer cells.

Epithelial cancer of the ovary, or ovarian cancer, is a relatively common gynecologic cancer that develops insidiously, and hence is associated with vague or no symptoms that would urge patients to seek medical attention. Not surprisingly, most women with ovarian cancer present with advanced (at least locally or regionally, and often systemically spread) disease. Ovarian cancer is managed with initial surgical resection followed by platinum-based chemotherapy. During the past decade, incremental advances in chemotherapy, and the introduction of targeted therapies (such as poly-ADP-ribose polymerase inhibitors and several others) and specially formulated compounds (such as liposomal anthracyclines) have resulted in improved survival and in more effective treatment of relapsed disease. In addition, a better understanding of genetic risk factors, along with aggressive screening, has permitted a tailored approach to preventive strategies, such as bilateral salpingo-oophorectomy in selected women along in specific patient populations genetically predisposed to this cancer (such as those harboring genetic alterations of the BRCA gene family). Although a complete clinical remission following initial chemotherapy can be anticipated for many patients, a review of “second-look” laparotomy, when it was often performed as a matter of routine care, indicates that less than 50% of patients are actually free of disease. Furthermore, nearly half of patients with a negative “second-look” procedure relapse and require additional treatment. Many patients will achieve a CR2 clinical response with additional chemotherapy. However, almost all patients will relapse after a short remission interval of nine to 11 months, with median OS of nine to 12 months. Effective strategies, such as introduction of novel immunotherapies, to prolong remission or to prevent relapse are required, as subsequent remissions are of progressively shorter duration until chemotherapy resistance broadly develops, leading to eventual disease-related demise.

The purpose of the study was to determine if the administration of GPS in combination with pembrolizumab has the potential to demonstrate clinical activity in the presence of macroscopic disease, where monotherapy with either agent would have a more limited effect. This study was the first clinical trial of GPS in a patient population harboring overt bulky disease. The negative influence of TME factors on the immune response is predicted to be mitigated by PD1 inhibition (by pembrolizumab), thus allowing the patient's own immune cells to invade and destroy cancerous growth deposits specifically sensitized against WT1 (by concomitantly-administered GPS). The endpoints of the study were safety, immunobiological response, overall response rate (as measured by “response evaluation criteria in solid tumors”, or RECIST), progression free survival and OS and other analyses of interest. GPS has been designed as maintenance therapy in order to provide an OS benefit after patients reach MRD status or complete remission. The final topline data from this study demonstrated that the combination of GPS and pembrolizumab could halt or slow down the progression in highly active disease refractory to other therapies.

On February 1, 2022, we announced the completion of enrollment in the study.

17

Table of Contents

On November 10, 2022, we reported the following confirmatory topline data from 17 evaluable patients in the study.

•Median OS was 18.4 months compared to 13.8 months with pembrolizumab alone in a checkpoint inhibitor single agent study in a similar patient population treated with checkpoint inhibitor alone.

•Median progression-free survival, or PFS, was 12 weeks compared to 8 weeks in a checkpoint inhibitor single agent study in a similar patient population treated with checkpoint inhibitor alone.

•The overall response rate of the trial was 6.3 percent with a DCR of 50.1 percent at a median follow-up of 14.4 months. In a checkpoint inhibitor single agent study in a similar platinum-resistant ovarian cancer patient population treated with a checkpoint inhibitor alone, the observed DCR was 37.2 percent, consistent with a DCR rate increase of approximately 45 percent in the GPS combination with pembrolizumab over that seen for checkpoint inhibitors alone.

•Survival and disease control benefits were observed in patients harboring tumors with any level of detectable PD-L1 expression, i.e., those with Combined Positive Score, or CPS, of 1 or higher. The DCR is 63.6% in patients with a CPS of 1 or higher. Patients with a CPS score of less than 1 showed a median OS of 3.2 months vs. patients with a CPS greater than or equal to 1 who had a median OS of 18.4 months and, as it relates to time to progression, patients with a CPS score of less than 1 had a median PFS of 1.9 months and patients with a CPS score of greater than or equal than 1 showed a median PFS of 3.8 months.

•In 16 evaluable patients in whom serial peripheral blood samples were available, a correlation was observed between PFS and OS and WT1-specific immune response after GPS vaccination across more than 1 channel with intracellular cytokine flow-cytometry assays in peripheral blood lymphocytes assaying reactivity against the four pooled WT1 antigens comprising GPS. The data were consistent with those seen in previous studies of GPS.

•The safety profile of GPS in combination with pembrolizumab was similar to pembrolizumab alone, with only the addition of low-grade rapidly resolving local reactions at the GPS injection site, consistent with observations from other GPS clinical studies.

In November 2023, additional immunobiological and clinical data from the study for 16 safety and efficacy evaluable patients who had follow-up cross-sectional imaging (CT/MRI) were presented at the International Gynecologic Cancer Society 2023 Annual Global Meeting:

•WT1-specific T-cell (CD8 and CD4) immune response data showed a positive trend over time post-baseline with highest consistency and potential biomarkers for consistency being IFNγ and MIP1β.

•GPS in combination with pembrolizumab was strongly immunogenic, as evidenced by the positive T-cell responses seen post-vaccination.

◦42.8% of patients (6/14) achieved CD8 T-cell immune response.

◦85.7% of patients (12/14) achieved CD4 T-cell immune response.

•A correlation between WT1 specific T-cell immune responses (CD8 or CD4) and PFS was observed in a subset of analyzed patients with 41% longer PFS in patients with recorded immune response vs without (p=0.025).

GPS Combination Therapy with Nivolumab for MPM

A single-center, open-label, single-arm, non-randomized investigator-sponsored Phase 1 trial of concomitant administration of GPS in combination with Bristol-Myers Squibb’s anti-PD-1 therapy, nivolumab (Opdivo) was initiated in February 2020 at MSK in patients with MPM who have previously received treatment with pemetrexed-based chemotherapy and have measurable disease on imaging, either due to residual disease after prior treatment or recurrent disease. We provided GPS and Bristol-Myers Squibb provided nivolumab for this study.

18

Table of Contents

The principal investigator for the study was Dr. Marjorie G. Zauderer, MD, Co-Director, Mesothelioma Program and Associate Attending Physician in the Thoracic Oncology Service, Department of Medicine at MSK. The purpose of the trial was to determine if the administration of GPS in combination with nivolumab has the potential to demonstrate antitumor immune responses and meaningful clinical activity in the presence of macroscopic disease in MPM patients. The study also investigated the tolerability of the combination, evaluated the immunogenicity of the two agents administered together, by CD4+ and CD8+ T-lymphocytes (both peripherally and at the tumor site), and gauged the degree of clinical benefit by assessment of the overall response rate with the combination in comparison with that reported with nivolumab alone in historical comparable patient populations.

With approximately 3,300 cases in the United States each year, accompanied by a rising incidence in developing countries, MPM is notoriously difficult to treat and can lead to poor clinical outcomes with respect to both OS and progression-free survival, especially for those patients with the sarcomatoid variant who show a median OS of approximately 4.0 to 5.0 months. In relapsed and refractory patients who progressed after the first line standard of care pemetrexed, a similar patient population to that in the GPS nivolumab combination trial, the common treatment regimen is vinorelbine and OS in those patients is reported to be between 4.5 and 6.2 months. In patients treated with other chemotherapy regimens, such as carboplatin and irinotecan, median OS is reported to be approximately 7.0 months.

In a randomized, controlled, blinded Phase 2 clinical trial in MPM patients completed in 2017, GPS monotherapy given as maintenance after first line tumor-debulking multimodality treatment demonstrated meaningful clinical activity with median survival of 22.8 months vs. 18.3 months in the control group (n=41) and with associated sustained immune responses (both CD4+ and CD8+) against the WT1 antigen while adverse events were mainly comprised of low grade reactions at the site of the injection. See GPS Monotherapy: Completed Clinical Trials in Other Indications.

Study enrollment (target total n=10) was completed at the end of 2022. In June 2023, we reported positive topline safety and efficacy data from the study:

•Nine of the 10 patients enrolled received at least three doses of GPS, with the third GPS dose given in combination with nivolumab.

•All enrolled patients had either received and progressed with or were refractory to frontline pemetrexed-based chemotherapy.

•Median OS in patients who received the combination therapy (9/10 patients) was 70.3 weeks (17.6 months) and 54.1 weeks (13.5 months) for all 10 patients (nine patients with combination therapy and one GPS only patient). Median OS for patients who entered the study as Stage IV patients was 62.3 weeks (15.6 months). OS was calculated as the time from cessation of the most recent previous therapy until confirmed death or most recent data update for patients who still alive.

•Median PFS for all patients was 11.9 weeks.

•DCR was 30% with three patients achieving stable disease per RECIST criteria with the tumor volume decrease of up to 17%.

•As expected in this high-risk advanced cancer population, all patients experienced adverse events, unrelated and related. Seven out of 10 patients (70%) had treatment related toxicities and six (60%) had nivolumab related toxicities. Grade 3, or G3, and higher toxicities were observed in three patients (30%). None of the G3 and higher toxicities were related to GPS. GPS related toxicities were observed in three patients (30%), all were Grade 1, or G1, and included G1 skin induration at the site of injection/injection site reaction and/or fatigue in two patients and G1 dizziness and non-cardiac chest pain, each in one patient.

•Of the 10 evaluable patients, eight were male and two were female, with a median age of 69 years. Sixty percent entered the study as Stage III or IV patients. Initial tumor stages were I (one patient), II (three patients), III (two patients) and IV (four patients).

19

Table of Contents

•All patients had MPM epithelioid and/or sarcomatoid variant, a tumor which universally expresses WT1.

In December 2023, we reported positive follow-up immune response and survival data:

•The median OS among patients who did not have an immune response to GPS was 9.0 months; the median OS for patients who had an immune response to GPS was 27.8 months, which was more than three times longer (208.3% increase) than for those patients without an immune response. Among the nine evaluable patients, four patients had a CD4+ immune response (44.4%) and three patients had a CD8+ immune response (33.3%) to GPS. Three patients had both CD4+ and CD8+ immune responses (33.3%).

•Among patients who had a full immune response (both CD4+ and CD8+) to GPS, two patients achieved an objective response (66.7%), while among the patients who did not have an immune response to GPS one patient achieved an objective response (14.3%).

GPS Monotherapy: Completed Clinical Trials in Other Indications

MPM

MPM is an asbestos-related cancer that forms on the protective tissues that cover many of the internal organs. The most common area affected is the lining of the lungs and abdomen, though it can also form around the lining of the heart. Most cases are traced to job-related exposures to asbestos and it can take approximately 40 years between exposure and cancer formation. Symptoms may include shortness of breath, a swollen abdomen, chest wall pain, cough, feeling tired, and weight loss. MPM is generally resistant to radiation and chemotherapy, and long-term survival is rare, even in cases where aggressive upfront debulking multimodality therapy (i.e., extirpative surgery, chemotherapy and in some cases radiotherapy, often described as “trimodality therapy” when used to treat MPM) are used.

A randomized, double-blind, placebo-controlled Phase 2 clinical trial in MPM patients enrolled a total of 41 patients at MSK and MDACC. Data from this Phase 2 clinical trial was presented in 2016. Based on an initial analysis of 40 patients who were eligible at the time with a median follow-up of 16.3 months, a median OS of 24.8 months was seen for GPS-treated MPM patients, compared to a median OS of 16.6 months for patients in the control arm. For patients with a basic reproductive ratio tumor resection and subsequent treatment with GPS, a significant survival benefit was observed compared to those who received a placebo, with a median OS of 39.3 months compared to 24.8 months (HR: 0.415) in favor of GPS. In a subsequent analysis for the entire cohort (n=41) in August 2016, with a median follow-up of 17.2 months, a median OS of 22.8 months was observed for GPS-treated MPM patients, compared to a median OS of 18.3 months for patients in the control arm. In the datasets from both of these analyses, GPS was shown to induce WT1-specific CD8 and CD4 T-cell activation. There were no clinically significant severe adverse events in this study.

Multiple Myeloma (MM)

MM is a cancer formed by malignant plasma cells, and its cause is unknown. The overgrowth of plasma cells in the bone marrow crowds out normal blood-forming cells, causing low blood counts and anemia (a shortage of red blood cells). MM can also cause a shortage of platelets (cells responsible for normal blood clotting) and lead to increased bleeding and bruising, along with problems fighting infections due to low white cell counts and/or lower levels of infection-fighting antibodies. MM causes a host of organ problems and symptoms, including fatigue, bone pain, fractures, circulatory problems (in small vessels of the brain, eye retina, heart, bowel, etc.) and kidney failure. Treatment for MM includes chemotherapy, glucocorticoids, drugs that modulate the immune system (immunomodulatory drugs, or IMiDs), proteasome inhibitors, histone deacetylase inhibitors, targeted monoclonal antibodies, radiation and autologous stem cell transplants, or ASCTs. The prognosis in MM is highly variable and depends on numerous risk factors, some related to the biology of the disease, others to the host (e.g., age and functional status). Consequently, median survival can vary from up to at least 15 years in non-high-risk patients who achieve complete remission, as defined by the International Myeloma Working Group, or IMWG, criteria, to approximately three years (from time of initial treatment) in patients with MM who achieve less than partial response, or PR, after ASCT. There are patients with MM who fare even more poorly than described above. For example, those in the immediately aforementioned group who also have high-risk cytogenetics at baseline may

20

Table of Contents

survive on average less than three years. Similarly, patients who are ineligible for ASCT and are managed only with chemotherapy and long-term IMiD maintenance (with up to nine cycles of lenalidomide) who also achieve less than complete remission and remain MRD-positive demonstrate a three-year OS rate of only about 55%; these landmark three-year OS rates decrease by approximately 40 to 50% in patients who also have high-risk cytogenetics at baseline. Despite significant therapeutic advances in the management of MM, the prognosis of patients with high-risk cytogenetics at the time of diagnosis remains quite poor, even when they successfully complete an ASCT, particularly if such patients continue to have evidence of MRD.

We have reported comprehensive final data from a Phase 2 study for GPS in 19 patients with MM. All non-progression events were confirmed and remained ongoing as of the time of the latest presentation (median follow-up at 20 months for survivors). The data indicate promising clinical activity among MM patients with high-risk cytogenetics at initial diagnosis who also remain MRD(+) after successful frontline therapy (induction regimen followed by ASCT). This subgroup of MM patients, when serially assessed per IMWG criteria, typically relapse/progress within 12 to 14 months after ASCT, even when they receive maintenance therapy with IMiDs such as thalidomide or proteasome inhibitors such as bortezomib - 18 of the 19 patients received lenalidomide maintenance starting after the first three GPS administrations following ASCT; the remaining single patient received bortezomib under the same schedule. All patients had evidence of at least MRD (MRD+) after ASCT, while 15 of the 19 also had high-risk cytogenetics at diagnosis. Combined, these characteristics typically result in low PFS rates that do not exceed 12 to 14 months following ASCT, even while on maintenance therapy with IMiDs or proteasome inhibitors, which are the current standards of care. At June 2017, median PFS with GPS was 23.6 months, while median OS had not been reached. Our results compare favorably with an unmatched cohort of broadly comparable MM patients with high-risk cytogenetics published by the Spanish PETHEMA group from the PETHEMA Network No. 2005-001110-41 trial. Our GPS therapy demonstrated a 1.87-fold increase in median PFS, as well as a 1.34-fold increase in the PFS rate at 18 months compared to the aforementioned historical cohort, which included MM patients with high-risk cytogenetics and MRD(+) post-ASCT and on continuous intensive maintenance with thalidomide +/- bortezomib. The safety profile was devoid of grade 3/4/5 treatment-related adverse events. Immune response data showed that up to 91% of patients had successfully developed T-cell (CD8 or CD4) reactivity to any of the four peptides within the GPS mixture, while up to 64% of patients demonstrated immune response positivity (CD4/CD8) against more than one WT1 peptide (multivalent responses). Moreover, multifunctional cross-epitope T-cell reactivity was observed in 75% of patients to antigenic epitopes against which hosts were not specifically immunized, in a pattern akin to epitope spreading. Further, a distinctive link was shown between the evolution of immune responses and changes in clinical response status (achievement of CR/very good partial response clinical status per IMWG criteria) over time following treatment with GPS, with each patient being used as his or her own control for each longitudinal comparison. This association has not been previously described for a peptide vaccine in MM. We believe that these results offer mechanistic underpinnings for immune activation against WT1 in patients with aggressive, high-risk MM, and support the potential antimyeloma activity of GPS.

GPS Combination Therapy: Completed Clinical Trial in Ovarian Cancer

GPS was studied in combination with nivolumab in an open-label, non-randomized Phase 1/pilot clinical trial, which was independently sponsored by MSK. The aim of the study was to evaluate the safety and efficacy of this combination in patients with WT1+ recurrent ovarian, fallopian tube or primary peritoneal cancer who were in second or greater clinical remission (after their successful first or subsequent “salvage” therapy). Eligible patients were devoid of macroscopic residual or recurrent disease, i.e., were free of locally or distantly metastatic deposits detectable by imaging modalities (CT, MRI and/or PET scan). This Phase 1/pilot clinical trial enrolled 11 patients with recurrent ovarian cancer who were in second or greater clinical remission at MSK, of whom 10 were evaluable. Patients enrolled in the clinical trial received the combination therapy during a 14-week treatment period. Individuals who had not progressed by the end of this period also received a maintenance course of GPS. In this study, treatment was continued until disease progression or toxicity. Information on the primary endpoint of this clinical trial, which was the safety of repeated GPS administrations, for a total of six doses, in combination with seven infusions of nivolumab was presented at the American Society of Clinical Oncology, or ASCO, 2018 annual meeting (O’Cearbhaill RE, et al). The secondary endpoint of the study was immune response, and the exploratory endpoints included landmark one-year PFS rate compared to historical controls and correlative analyses between clinical and immune responses. Exploratory efficacy interim data from this pilot trial showed that GPS, when combined with a PD-1 inhibitor, in this case nivolumab, demonstrated PFS of 64% at one year in an intent to treat the group of 11 evaluable patients with WT1+ ovarian cancer in second or greater remission. Among patients who received at least

21

Table of Contents

three doses of GPS in combination with nivolumab, PFS at one year was 70% (7/10). The historical rates with best standard treatment do not exceed 50% in this disease setting. The most common adverse events were Grade 1 or 2, including fatigue and injection site reactions. Dose limiting toxicity was observed in one patient, following the second dose of the combination. No additional adverse event burden was observed for the combination as compared to nivolumab monotherapy. The combination induced a high frequency of T- and B-cell immune responses.

Follow-up data now show that three of the 11 patients enrolled in the study have continued to show no signs of disease progression. The mean PFS for these three patients is 35.4 months from the initiation of salvage chemotherapy, or mean PFS of 30.1 months from the first administration of GPS plus nivolumab. Based on this follow-up information, the estimated two-year PFS rate for this study is now 27.3% for the intent-to-treat, or ITT, patients (n=11) and approximately 30% for patients who received greater than two doses of GPS and nivolumab (n=10), as compared to a historical 3% to 10% PFS rate for patients receiving only salvage chemotherapy. No new serious adverse events were noted during the longer follow-up period.

SLS009 (Tambiciclib): Highly Selective Next Generation CDK9 Inhibitor

Overview

SLS009, or tambiciclib, is a next generation highly selective CDK9 inhibitor which we in-licensed from GenFleet in March 2022. We have worldwide development and commercialization rights, except for Greater China. See Strategic Collaborations and License Agreements - Exclusive License Agreement with GenFleet Therapeutics (Shanghai), Inc. CDK9 activity has been shown to correlate negatively with OS in several cancer types, including hematologic cancers, such as AML and lymphomas, as well as solid cancers, such as osteosarcoma, pediatric soft tissue sarcomas, melanoma, endometrial, lung, prostate, breast and ovarian cancer.

Mechanism of Action

CDK9 is a major cancer target. CDK9, together with cyclin T1, forms positive transcription elongation factor b, or P-TEFb, which plays an important role in allowing long RNA strands to be quickly transcribed. P-TEFb is crucial for the synthesis of some of the key proteins necessary for survival of cancer cells, including short-lived proteins such as MCL-1, which is a key anti-apoptotic (preventing programmed cell death) protein, and oncogenes such as c-MYC. These proteins must be constantly replenished for cancer cells to survive. Inhibition of CDK9 can decrease the levels of MCL-1 and c-MYC which can result in apoptosis and cell cycle arrest. Cyclin-dependent kinases, or CDKs, play a role not only in cancer cells but also healthy cells. Drug candidates that broadly target CDKs, i.e., those with lower specificity, can have issues with toxicity because healthy cells as well as cancer cells are targeted. The first generation of CDK9 inhibitors worked across many CDK targets in addition to CDK9. These first-generation drug candidates showed some clinical activity but had significant toxicity due to low specificity. Next generation CDK9 inhibitors, including SLS009, have potential for higher specificity for CDK9 and lack of binding to other CDKs, potentially resulting in less toxicity and more consistent clinical activity.

Key Attributes

Higher selectivity: In preclinical studies, SLS009 has demonstrated higher selectivity for CDK9 than other members of the human kinome when compared to other non-oral CDK9 inhibitors in clinical development in the United States for hematological cancers, including AZD-4573 being developed by AstraZeneca and enitociclib (VIP152) being developed by Vincerx Pharma. The human kinome is a set of all 538 kinases, which are enzymes that play essential functions by catalyzing protein phosphorylation. SLS009 has been shown to block activity of fewer kinases, other than CDK9, than these competing development candidates which, as demonstrated in clinical trials, has resulted in a better safety profile with fewer treatment related adverse events.

Higher anti-cancer activity: The preclinical data below is a comparison of SLS009 and an exact molecular copy of enitociclib (VIP152) (shown in the graphs as GFC002). The top table shows the maximal inhibitory concentration, which is the amount of drug that is needed to inhibit survival of cancer cells, across different cell lines of cancer in vitro. Across multiple cancer cell line histologies, a smaller concentration of SLS009 is needed to achieve the same inhibitory effect as compared to the exact molecular copy of enitociclib (VIP152). In a mouse AML xenograft model,

22

Table of Contents

the lowest tumor growth and the highest AML cell killing was achieved by SLS009. In this mouse model, there was significantly more toxicity, including weight loss, observed with enitociclib (VIP152) treated mice.

Cell lines

SLS009 IC50 (72h)

VIP152 IC50 (72h)

AML

4.8 ~33 nM

15.9 ~136 nM

Lymphoma

10.6~77.9 nM

16.6 ~138 nM

MM

33.6 ~151 nM

51.4 ~397 nM

ALL

13.4~35.7 nM

42.3 ~68.6 nM

CLL

25 nM

40.7 nM

23

Table of Contents

Pharmacokinetic, or PK, Data: PK data observed from the completed Phase 1 trial are shown below. PK data show the relationship between the dosing regimen and the body’s exposure to a drug as indicated by the concentration time curve. An important component of the mechanism of CDK9 inhibition in cancer is to achieve very high concentration immediately which then shuts down the cancer cell and leads to apoptosis, while quickly ramping down so that there is not apoptosis of neutrophils. PK analyses were made for both twice a week dosing regimen (BIW cohorts) and once a week dosing regimen (QW cohorts).

BIW cohorts: The PK analysis result showed that after intravenous infusion of 2.5 mg (N=1), 4.5 mg (N=5), 9 mg (N=8), 15 mg (N=11), 22.5 mg (N=7), 30 mg (N=8), and 40 mg (N=3) of SLS009 twice a week (BIW, administered on the first and second days of each week for one hour), the plasma concentration reached peak at the end of the infusion. The exposure parameters (Cmax and AUC) of SLS009 increased in an approximately proportional manner in the dose range 2.5 mg to 40 mg. The PK profiles in single and repeated administration were comparable.

QW cohorts: After intravenous infusion of 30 mg (N=7), 45 mg (N=8), and 60 mg (N=9) of SLS009 once a week (QW, administered on the first day of each week for four hours), the plasma concentration-time profiles were comparable to those of BIW administration, indicating a similar characterization of distribution and metabolism. The plasma concentration reached peak at the end of the infusion. The exposure parameters (Cmax and AUC) of SLS009 increased in an approximately proportional manner with the dose range 30 mg~60 mg. After QW administration, there was no obvious accumulation of SLS009.

Comparison of pharmacokinetics results in twice a week and once a week dosing regimens at different dose levels is shown below.

24

Table of Contents

Pharmacodynamic, or PD, Data: The graphs below show certain correlative pharmacodynamic data from the completed Phase 1 study. At higher dose levels, a pattern of drug induced decreases in two biomarkers commonly used for assessing pharmacodynamics of CDK9 inhibitors, MCL1 and MYC, is seen. These data are important in that we believe they demonstrate that SLS009 is translating CDK9 inhibition into a meaningful suppression of cancer associated proteins. MCL1 is a key antiapoptotic protein. It is postulated that CDK9 inhibitors can indirectly inhibit MCL1. We believe that these PD data demonstrate that SLS009 does inhibit MCL1. MYC is a key driver in many cancers, both hematological and solid tumors. We believe that the data presented below demonstrate meaningful MYC suppression.

25

Table of Contents

Efficacy in venetoclax resistant disease: Venetoclax, in combination with hypomethylating agents, is a key component of treatment for AML across all patient categories, especially older patients, who are the vast majority of AML patients. We believe that SLS009 has potential as a treatment option for AML patients who are refractory to or relapsed after treatment with venetoclax. We observed in the Phase 1 study that a r/r AML patient achieved a complete response and four additional r/r AML patients achieved greater than or equal to 50% decrease in bone marrow blasts which includes patients who had prior treatment with venetoclax. To our knowledge, as of March 1, 2026, SLS009 is the only CDK9 inhibitor for which a complete response as monotherapy in r/r AML has been reported. See Phase 1 Clinical Trial.

Phase 1 Clinical Trial

The Phase 1 dose-escalating clinical trial in the United States and China for SLS009 was completed in 2023. The study evaluated both twice-a-week and once-a-week dosing and the indications were r/r AML, chronic lymphocytic leukemia, or CLL, small lymphocytic leukemia, or SLL, and lymphoma. The primary goal of the trial was to establish the RP2D which was established at 60 mg for AML and 100mg for lymphomas.

Two dosing regimens were tested in incremental SLS009 dose levels from 2.5 mg to 100 mg, either twice a week, or BIW, dosing regimen or once a week, or QW, dosing regimen. A total of 34 patients were treated in the AML cohort and 52 patients in the r/r lymphoma cohort. Among the 52 r/r lymphoma patients, 15 were diagnosed with PTCL.

For the cohort of patients with AML and with lymphomas, all key study objectives regarding PK, PD, safety and clinical activity data were met:

26

Table of Contents

Efficacy:

AML cohort:

•Anti-tumor activity and clinical responses across groups and dose levels were observed, indicating a broad therapeutic index. Meaningful cell killing activity was defined as ≥50% reduction in blasts in the bone marrow.

◦AML cohort: cell killing activity observed at the following dose levels:

▪9 mg BIW: 50.0% bone marrow blast (BMB) reduction;

▪15 mg BIW: 53.8% BMB reduction;

▪30 mg QW: 57.1% BMB reduction;

▪45 mg QW: 61.3% BMB reduction;

▪60 mg QW: 77.3% BMB reduction.

◦Durable complete remission (CR) with no MRD in one patient with AML who had failed prior aza/ven therapy was achieved. The duration of the CR was eight months. Historically, best available therapy median OS for patients relapsed after aza/ven is estimated at 2.5 months.

Lymphomas cohort:

•Among 34 evaluable r/r lymphoma patients, five (14.7%) achieved a clinical response with a reduction in tumor burden of up to 62%.

•An additional seven patients (20.6%) achieved stable disease, or SD, resulting in an overall DCR of 35.3%.

•In the subgroup of PTCL patients, four out of 11 (36.4%) evaluable patients achieved a clinical response.

Safety:

AML cohort:

•No dose limiting toxicities and no higher grade non-hematologic toxicities of any kind were observed.

•Some hematologic toxicities were difficult to determine in patients with hematologic cancers but were short in duration and reversible.

Lymphomas cohort:

•There were no drug-related fatalities at any dose level, and the drug was well tolerated.

•In patients treated with BIW dosing regimen, no significant safety events appeared to be dose-dependent.

•In patients receiving the QW dosing regimen, ≥ G3 treatment-related adverse events, or TRAEs, occurred, primarily hematologic events, at higher dose levels.

•Non-hematologic toxicities were rare across all dose levels with five out of 52 patients (9.6%) experiencing higher grade toxicities, including hypokalemia (3/52 patients, 5.8%), upper respiratory tract infection (1/52 patients, 1.9%) and increase in bilirubin (1/52 patients, 1.9%).

•Maximum Tolerated Dose, or MTD, was not reached with only 1/5 patients at the highest dose level studied (100 mg) experiencing a dose-limiting toxicity, or DLT.

•No DLTs were observed at any other dose level, and there were no unexpected toxicities across the study.

27

Table of Contents

PK Data:

AML cohort:

•Achieved desired 24 hours > IC90 peripheral blood concentrations after the first infusion, with IC90 concentrations resulting in up to 97% cancer cells killed.

Lymphomas cohort:

•Exposure parameters (maximum concentration, or Cmax, and area under curve, or AUC) increased in an approximately proportional manner with the dose range of 30 mg~60 mg QW. The exposure of 100 mg was the highest, and the mean plasma concentration remained above IC90 for the longest time period (nearly 50 hours).

PD Data:

AML cohort:

•Achieved desired levels of MCL1 and MYC suppression in peripheral blood with decrease in MCL1 or MYC observed in 97% (66/68) of analyzed patients. A trend of proportionally increased maximum inhibition of MCL1 and MYC observed among higher doses (22.5 mg to 60 mg) in both AML and lymphoma patients, which is more prominent in QW cohorts compared to BIW cohorts. QW regimen was able to induce longer sustained inhibition (at least 6 hours) of MCL1 and MYC than BIW treatment, allowing longer period for CDK9 inhibition to induce cancer cell apoptosis.

Lymphomas cohort:

•Desired levels of suppression in peripheral blood were achieved, leading to a decrease in MCL1 or MYC biomarkers in all (100%) studied patients. Biomarker suppression was dose-dependent in patients receiving QW dosing. The biomarkers studied included MYC and MCL1 with SLS009 administration resulted in biomarkers suppression across dose levels in both administration regimens (BIW and QW) and a dose-dependent decrease in QW groups. 100mg QW dose level resulted in the longest sustained inhibition of both MCL1 and MYC.

Phase 2 Development Program

Phase 2a clinical trial in AML patients

In the second quarter of 2023, we commenced an open label, single arm, multi-center Phase 2a clinical trial of SLS009 in combination with aza/ven in AML patients who failed or did not respond to treatment with venetoclax-based therapies. The trial was designed to evaluate safety, tolerability, and efficacy at two dose levels of SLS009, 45 mg QW, and 60 mg QW or 30 mg BIW, in combination with aza/ven. In addition to safety and tolerability of SLS009 in combination with aza/ven, the primary endpoints were overall response rate and duration of response. Additional endpoints included event free survival, OS, and PK assessments. The trial included several sites in the United States and was designed to enroll a minimum of 20 patients.

Patients with AML that fail venetoclax-based therapies have limited treatment options and a poor prognosis with a median OS of approximately 2.5 months. See Current AML Treatment Therapies for more information on the AML treatment landscape.

In July 2025, we announced that all primary endpoints were met in the Phase 2 clinical trial of SLS009 in r/r AML. 54 evaluable r/r AML patients who previously failed venetoclax-based therapies were enrolled and treated with SLS009, and venetoclax/azacitidine. Among the 54 treated patients, 47 had AML MR (87%) and 23 had ASXL1 mutations (43%). Among the AML MR patients, 17 had myelomonocytic/myelomonoblastic subtype of AML (M4 and M5), representing 31% of all patients.

Efficacy:

28

Table of Contents

•The results exceeded the pre-specified ORR threshold of 20%, demonstrating robust clinical activity and supporting advancement into late-stage development.

•The ORR in all evaluable patients was 33% across all cohorts and dose levels and 40% for the 30mg BIW dose level.

•At the 30 mg BIW dose, among AML MR patients, the ORR was 44%.

•The highest efficacy was observed among patients with ASXL1 mutations, with an ORR of 50% (9/18) at 30 mg BIW dose levels and M4/M5 patients with 50% (6/12) ORR.

•The mOS surpassed the historical benchmark of best available therapy of 2.4 months for patients who received one prior line of therapy and 1.8 months for those who received more than one prior line of therapy.

•The mOS for patients treated with 30mg BIW, with a median of 1 prior line of therapy, was 8.8 months, while the mOS in AML MR patients reached 8.9 months vs. 2.4 months with best available therapy.

•The mOS for cohorts with a median of 2 prior lines of therapies was 4.1 months vs.1.8 months with best available therapy.

Safety: The addition of SLS009 to the venetoclax/azacitidine regimen was well tolerated and did not result in increased toxicities compared to ven/aza alone. No DLTs were observed across all dose levels.

In addition, following a productive end of Phase 2 meeting, the FDA recommended that we proceed into a trial to include newly diagnosed, first-line AML patients eligible for aza/ven therapy, where the FDA noted clinical benefit might be greatest. The randomized 80-patient trial is currently ongoing and began enrollment in the first quarter of 2026. The trial will include two groups: predictive biomarker cohort (newly diagnosed patients unlikely to benefit from standard aza/ven therapy based on molecular profiling) and early venetoclax resistance cohort (patients who initiate treatment with aza/ven, but demonstrate confirmed lack of any response after two treatment cycles).

Preclinical Studies

In August 2022, we announced results from preclinical in vitro studies for SLS009 in AML cell lines. The in vitro studies were conducted at an independent third-party contract research organization, and utilized the following cell lines based on their unique characteristics in combination with SLS009’s mechanism of action: RH30, a pediatric soft tissue sarcoma cell line that is a model for studying high-risk pediatric rhabdomyosarcoma, NCI-H209, a small cell lung cancer cell line characterized by the loss of function of two major tumor suppressor genes, RB1 and TP53, and which also expresses MCL-1, a major target of CDK9 inhibition, SKOV-3, an ovarian cancer cell line containing the wild type BRCA1 gene and highly expresses CDK9, and OCI-AML-2, an AML cell line that develops resistance to venetoclax. The data showed that SLS009 demonstrated significant anti-tumor effects in all four selected cell lines. In three out of the four cell lines, SLS009 inhibited cancer cell growth by 90 to 100 percent.

In August 2022, we announced results from a new preclinical in vitro study for SLS009 in neuroendocrine prostate cancer, or NEPC. The data shows that SLS009 demonstrated significant anti-tumor effects in the selected cell line at nanomolar concentrations and, in certain samples, complete growth inhibition with no viable cancer cells. Additionally, in December 2022, we announced results from a preclinical in vivo study for SLS009 that demonstrated robust inhibition of tumor growth in a mouse xenograft model of SCLC. SLS009 was tested against NCI-H209 SCLC xenografts in athymic nude mice in four treatment groups of eight mice each (n=32) consisting of SLS009 alone, olaparib (a PARP inhibitor) alone, a combined regimen of SLS009 and olaparib, and a vehicle control. Treatments were initiated after tumor xenograft volumes exceeded 120 mm3 in each animal group and mice were subsequently sacrificed after mean tumor volume exceeded 1,500 mm3 in the control group. SLS009 treated mice exhibited a 40.4% decrease in mean tumor growth compared to the control group in this very aggressive cancer model which had a tenfold increase in average tumor volume over 20 days. Strongest effects were observed with SLS009 in combination with olaparib, with mean tumor growth decreased by 72.3%. Treatment with olaparib alone resulted in a 30.2% mean decrease in tumor growth. No significant toxicity or safety concerns were observed in any of the treatment groups.

In November 2024, we announced data from preclinical studies identifying ASXL1 mutation as key predictor of SLS009 in response to solid cancers. We performed experiments in patient derived cell lines (PDCs), exposing them to SLS009 at various concentrations and determining the inhibitory concentration (IC50) for each cell line. All cell lines were analyzed for presence of ASXL1 mutations and other genetic markers. High efficacy was prespecified as IC50 < 100 nM, significantly lower than the standard threshold definition for an effective compound

29

Table of Contents

(IC50 < 1,000 nM). This threshold was chosen based on the observed long-lasting concentrations of SLS009 observed in patients, which were ~400 nM.

Negative controls consisted of untreated cell lines, while active negative control varying concentrations of revumenib (drug used in hematologic malignancies). Positive controls involved cell lines treated with staurosporine at different concentrations (staurosporine is a standard control compound for kinase inhibitors due to its high broad-spectrum potency in inhibiting most protein kinases at sub-micromolar concentrations).

The results were as follows:

•In CRC MSI-H, ASXL1 mutations were observed in 7/12 (58%) of PDCs, aligning with predicted frequency of ~55%

•In NSCLC, ASXL1 mutations occurred in 2/6 (33%) studied cell lines, higher than predicted 2.6%

•Overall, in 18 studied solid cancer cell lines, ASXL1 mutations were recorded in nine cell lines and no ASXL1 mutations were recorded in 9 cell lines which were designated as control

•In ASXL1 mutated cell lines, high SLS009 efficacy (IC50 <100 nM) was observed in 6/9 (67%) solid cancer cell lines and in non-ASXL1 mutated cancer high SLS009 efficacy was observed in 0/9 (0%) of studied solid cancer cell lines

◦In CRC MSI-H, high efficacy (IC50 <100 nM) was observed in 4/7 (57%) of ASXL1 mutated cell lines and in 0/5 (0%) of non-ASXL1 mutated cell lines

◦In NSCLC, high efficacy (IC50 <100 nM) was observed in 2/2 (100%) of ASXL1 mutated cell lines and in 0/4 (0%) of non-ASXL1 mutated cell lines

•No activity was observed in any of the studied cell lines with revumenib (negative control) at any concentration

•Staurosporine activity was confirmed, but interestingly and importantly, SLS009 outperformed positive control staurosporine in 5/9 cell lines

PIVOT Program

In December 2022, we announced that SLS009 will be evaluated in pediatric solid tumors and leukemia models through the NCI Pediatric Preclinical in Vivo Testing, or PIVOT, program. SLS009 testing through the program involves a three-phase research plan for PK, tolerability, and efficacy in pediatric tumors. In the first phase, PIVOT principal investigators will conduct PK experiments to confirm the appropriate dose and route administration for SLS009. In the second phase, tolerability of the dose and route of administration selected from the PK phase will be determined. In the last phase, monotherapy in vivo efficacy testing for SLS009 will be performed by PIVOT investigators. Studies will be supported through cooperative agreement grants from the NCI to the seven PIVOT research programs performing the testing and a centralized coordinating center.

The PIVOT program is a comprehensive program to systematically evaluate novel agents against genomically characterized pediatric solid tumor and leukemia models at eight participating research institutions. By supporting a more reliable agent prioritization process, the PIVOT program contributes to the goal of accelerating discovery of more effective treatments for children with cancer.

Each PIVOT principal investigator has expertise in preclinical testing of childhood cancer in vivo models. These models utilize patient derived xenografts, many of which are refractory to current standard of care treatments, from high-risk childhood cancers and have undergone comprehensive genomic characterization to demonstrate close resemblance to genetic alterations seen in the respective human cancers. Research strategies are based on a substantial body of data showing that preclinical testing in the appropriate pediatric cancer models, combined with expertise on relative drug exposures tolerated in mice and humans, provides powerful insights into likely clinical utility of investigational agents.

PIVOT Program participating institutions and relevant pediatric cancer models are as follows:

•Jackson Laboratory which serves as PIVOT Coordinating Center

•St. Jude Children’s Research Hospital for soft tissue sarcomas including rhabdomyosarcoma

30

Table of Contents

•MD Anderson Cancer Center for osteosarcoma

•University of Texas Health Science Center San Antonio for Ewing sarcoma rhabdomyosarcoma, kidney, and liver cancers

•Memorial Sloan Kettering Cancer Center for pediatric sarcomas and other solid tumors

•Children's Hospital of Chicago for orthotopic CNS tumors

•Children’s Cancer Inst Australia for acute lymphoblastic leukemia

•Children’s Hospital of Philadelphia for neuroblastoma

The first and second phases of the program, pharmacokinetics and tolerability, respectively, have been successfully completed and dosing regimens have been developed.

In May 2025, we announced data from this PIVOT program, which included 27 patient-derived ALL tumors

from pediatric patients. Tumors were xenografted in mice in two groups, vehicle control arm and SLS009 arm. Mice were treated with a fractionated dose once per week for six consecutive weeks. Treatment was well tolerated. For all models, median survival was approximately tripled in the SLS009 arm, compared to vehicle control arm. SLS009 demonstrated delayed progression in 25/27 (93%) models and more than two times longer time to progression in 15/27 (56%) of ALL models. In addition, there were complete responses, or CR, in two models and in one of the two models CR was maintained after the treatment had been completed until the end of the study (four months). Among seven KMT2A rearranged models, time to progression was extended in all seven models, and in six out of seven (86%) time to progression was more than doubled.

Strategic Collaborations and License Agreements

Exclusive License Agreement-Memorial Sloan Kettering Cancer Center

In September 2014, we entered into a license agreement with MSK under which we were granted an exclusive license to develop and commercialize MSK’s WT1 peptide vaccine technology. The MSK original license agreement was first amended in October 2015, further amended in August 2016, amended and restated in May 2017 and again amended and restated in October 2017. In connection with the entry of the original license agreement and its amendments, MSK was issued or assigned an aggregate of 4,846 ordinary shares of the privately held Bermuda exempted company, Sellas Life Sciences Group Ltd., or Private SELLAS, common stock for the year ended December 31, 2017. These common stock shares were converted into our common stock shares upon the business combination with Private SELLAS on December 29, 2017.

Under the terms of the current amended and restated MSK license agreement, we agreed to pay minimum royalty payments in the amount of $0.1 million each year commencing in 2015 and research funding costs of $0.2 million in each year and for three years commencing in January 2016. We also agreed to pay MSK a mid-six digit amount over a one year period in exchange for MSK’s agreement to further amend and restate the MSK license agreement in October 2017. In addition, to the extent certain development and commercial milestones are achieved, we also agreed to pay MSK up to $17.4 million in aggregate milestone payments for each licensed product, and for each additional patent licensed product, up to $2.8 million in additional milestone payments. We also agreed to pay MSK a tiered royalty in the mid-single digits in the event of commercial sales of any licensed products and agreed to raise $25.0 million in gross proceeds no later than December 31, 2018. We raised this amount from the proceeds received from the sale of our Series A Convertible Preferred stock in March 2018 and our underwritten public offering of shares of common stock, pre-funded warrants to purchase shares of common-stock, and warrants to purchase shares of common stock in July 2018. Under the terms of the agreement, we achieved a clinical development milestone at the end of the fourth quarter of 2018, triggering a $0.5 million payment in the first quarter of 2019.

31

Table of Contents

Unless terminated earlier in accordance with its terms, the MSK license agreement as amended and restated, will continue on a country-by-country and licensed product-by-licensed product basis, until the later, of: (a) expiration of the last valid claim embracing such licensed product; (b) expiration of any market exclusivity period granted by law with respect to such licensed product; or (c) ten years from the first commercial sale in such country.

Merck & Co., Inc. Clinical Trial Collaboration and Supply Agreement

In September 2017, we entered into a clinical trial collaboration and supply agreement through a Merck subsidiary, whereby we agreed with the Merck subsidiary to collaborate on a clinical program to evaluate GPS as it is administered in combination with their PD-1 inhibitor pembrolizumab in a Phase 1/2 clinical trial enrolling patients in up to five cancer indications, including both hematologic malignancies and solid tumors.

The Phase 1/2 clinical trial was designed to explore the combination of GPS plus pembrolizumab in patients with WT1+ relapsed or refractory tumors in both solid tumor and hematological cancer indications and to assess the efficacy and safety of the combination, comparing overall response rates and immune response markers achieved with the combination compared to prespecified rates based on those seen with pembrolizumab alone in comparable patient populations. This trial was initiated in December 2018. In 2020, we, together with Merck determined to focus on ovarian cancer (second or third line). We reported updated clinical and initial immune response data from this study in June 2021. In February 2022 we reported that we had completed enrollment of 17 evaluable patients in this study. In November 2022, we reported topline clinical and initial immune response data from this study, which showed that treatment with the combination of GPS and pembrolizumab compared favorably to treatment with anti-PD-1 therapy alone in a similar patient population and presented final data from this study at the International Gynecologic Cancer Society 2023 Annual Global Meeting in November 2023.

Exclusive License Agreement with 3D Medicines Inc.

In December 2020, we, together with our wholly-owned subsidiary, SLSG Limited, LLC, entered into an Exclusive License Agreement (the “3D Medicines Agreement”) with 3D Medicines pursuant to which we granted 3D Medicines a sublicensable, royalty-bearing license, under certain intellectual property owned or controlled by us, to develop, manufacture and have manufactured, and commercialize GPS and heptavalent GPS, or GPS-Plus, product candidates, or the GPS Licensed Products, for all therapeutic and other diagnostic uses in Greater China, or the 3DMed Territory. The license is exclusive, except with respect to certain know-how that has been non-exclusively licensed to us and is sublicensed to 3D Medicines on a non-exclusive basis. We have retained development, manufacturing and commercialization rights with respect to the GPS Licensed Products in the rest of the world.

In partial consideration for the rights granted by us, 3D Medicines agreed to pay us (i) a one-time upfront cash payment of $7.5 million in order to reimburse us for certain expenses incurred with respect to the development of the GPS Licensed Products prior to execution of the 3D Medicines Agreement, and (ii) milestone payments totaling up to $194.5 million in the aggregate upon the achievement of certain technology transfer, development and regulatory milestones, as well as certain net sales thresholds of GPS Licensed Products in the 3DMed Territory in a given calendar year.

3D Medicines also agreed to pay tiered royalties based upon a percentage of annual net sales of GPS Licensed Products in the 3DMed Territory ranging from the high single digits to the low double digits. The royalties are payable on a GPS Licensed Product-by- GPS Licensed Product and region-by-region basis commencing on the first commercial sale of a GPS Licensed Product in a region and continuing until the latest of (i) the date that is 15 years from the receipt of marketing authorization for such GPS Licensed Product in such region and (ii) the date that is 10 years from the expiration of the last valid claim of a licensed patent covering or claiming such GPS Licensed Product in such region. The royalty rate is subject to reduction under certain circumstances, including when generic competition for a GPS Licensed Product exists in a particular region.

3D Medicines is responsible for all costs related to developing, obtaining regulatory approval of and commercializing the GPS Licensed Products in the 3DMed Territory. 3D Medicines is required to use commercially reasonable best efforts to develop and obtain regulatory approval for, and upon receipt of regulatory approval, commercialize the GPS Licensed Products in the 3DMed Territory. A joint development committee has been established between 3D Medicines and us to coordinate and review the development, manufacturing and commercialization plans with respect to the GPS Licensed Products in the 3DMed Territory. We and 3D Medicines also agreed to negotiate in

32

Table of Contents

good faith the terms and conditions of a clinical supply agreement, a commercial supply agreement, and related quality agreements pursuant to which we will manufacture or have manufactured and supply 3D Medicines with all quantities of the GPS Licensed Product necessary for 3D Medicines to develop and commercialize the GPS Licensed Products in the 3DMed Territory until 3D Medicines has received all approvals required for 3D Medicines or its designated contract manufacturing organization to manufacture the GPS Licensed Products in the 3DMed Territory.

The 3D Medicines Agreement will expire on a GPS Licensed Product-by-GPS Licensed Product and region-by-region basis on the date of the expiration of all of 3D Medicines’ payment obligations to us. Upon expiration of the 3D Medicines Agreement, the license granted to 3D Medicines will become fully paid-up, perpetual and irrevocable. Either party may terminate the 3D Medicines Agreement for the other party’s material breach following a cure period or upon certain insolvency events. We may terminate the 3D Medicines Agreement if 3D Medicines or its affiliates or sublicensees challenge the validity or enforceability of the licensed patents. At any time following the two-year anniversary of the effective date, 3D Medicines has the right to terminate the 3D Medicines Agreement for convenience, subject to certain requirements. 3D Medicines may terminate the 3D Medicines Agreement upon prior notice to us if the grant of the license to 3D Medicines is prohibited or delayed for a period of time due to a change of U.S. export laws and regulations.

The 3D Medicines Agreement includes customary representations and warranties, covenants and indemnification obligations for a transaction of this nature.

Under the 3D Medicines Agreement, we achieved regulatory milestones relating to agreement upon and completion of a technology transfer plan in March 2021 and June 2021, respectively, for $1.0 million each and upon approval by the NMPA in March 2022 of an IND for a Phase 1 study, which triggered a $1.0 million milestone payment to us. A total of $191.5 million in potential future development, regulatory and sales milestones, not including future royalties, remains under the 3D Medicines Agreement.

We entered into a Side Letter Agreement with 3D Medicines, dated December 5, 2022, or Side Letter, arising from our agreement with 3D Medicines for 3D Medicines to participate in the REGAL study through the inclusion of approximately 20 patients from mainland China. The Side Letter, together with the 3D Medicines Agreement, details the terms and conditions of 3D Medicines' participation in the REGAL study.

In December 2023, we announced that we had commenced a binding arbitration proceeding against 3D Medicines regarding, among other things, the trigger and payment of relevant milestone payments due to us as well as 3D Medicines' failure to use commercially reasonable best efforts to develop GPS in accordance with the terms of the agreement. See Item 3. Legal Proceedings.

Exclusive License Agreement with GenFleet Therapeutics (Shanghai), Inc.

On March 31, 2022, or the GenFleet Agreement Effective Date, we entered into a License Agreement, or the GenFleet Agreement, with GenFleet pursuant to which GenFleet granted to us a sublicensable, royalty-bearing license, under certain of its intellectual property, to develop, manufacture and have manufactured, and commercialize a small molecule CDK9 inhibitor, or the CDK9 Licensed Product, for the treatment, diagnosis or prevention of disease in humans and animals in all territories other than Greater China, or the SLS009 Territory. The CDK9 inhibitor, known as SLS009, is currently in a Phase 1 clinical trial in the United States and China.

In consideration for these rights, we agreed to pay to GenFleet (i) an initial payment of $10.0 million as an upfront license fee and for a technology transfer, $4.5 million of which was paid within 30 days of the GenFleet Agreement Effective Date and $5.5 million of which is due upon the first day of the 15th calendar month following the GenFleet Agreement Effective Date, (ii) development and regulatory milestone payments for up to three indications totaling up to $48.0 million in the aggregate, and (iii) milestone payments totaling up to $92.0 million in the aggregate upon the achievement of certain net sales thresholds of CDK9 Licensed Products in the SLS009 Territory in a given calendar year.

We also agreed to pay GenFleet tiered royalties based upon a percentage of annual net sales of CDK9 Licensed Products in the SLS009 Territory ranging from the low to high single digits. The royalties are payable on a CDK9 Licensed Product-by-CDK9 Licensed Product and region-by-region basis commencing on the first commercial sale

33

Table of Contents

of a CDK9 Licensed Product in a region and continuing until the later of (i) the date that is 10 years following the date of first commercial sale for such CDK9 Licensed Product in such region and (ii) the date of the expiration of the last valid claim of a licensed patent covering or claiming such CDK9 Licensed Product in such region. The royalty rate is subject to reduction under certain circumstances, including when generic competition for a CDK9 Licensed Product exists in a particular region.

We are responsible for all costs related to developing, obtaining regulatory approval of and commercializing the CDK9 Licensed Products in the SLS009 Territory and we are required to use commercially reasonable efforts to develop and obtain regulatory approval for, and upon receipt of regulatory approval, commercialize the CDK9 Licensed Products in the SLS009 Territory. We and GenFleet have established a joint steering committee to coordinate and review the development, manufacturing and commercialization plans with respect to the CDK9 Licensed Products in the SLS009 Territory. We and GenFleet also have entered into a supply agreement and related quality agreement pursuant to which GenFleet is manufacturing, or having manufactured, and supplying us with all quantities of the CDK9 Licensed Product necessary for us to develop and commercialize the CDK9 Licensed Products in the SLS009 Territory.

The GenFleet Agreement will expire on a CDK9 Licensed Product-by-CDK9 Licensed Product and region-by-region basis on the date of the expiration of all of our payment obligations to GenFleet. Upon expiration of the GenFleet Agreement, the license granted to us will become fully paid-up, perpetual and irrevocable. Either party may terminate the GenFleet Agreement for the other party’s material breach following a cure period or upon certain insolvency events. During the period from the first anniversary of the GenFleet Agreement Effective Date until the first regulatory approval of a CDK9 Licensed Product in any country within the SLS009 Territory, we will have the right to terminate the GenFleet Agreement upon 180 days’ prior written notice to GenFleet if a clinical failure, as described in the GenFleet Agreement, occurs. If we terminate the GenFleet Agreement before the first day of the 15th calendar month following the GenFleet Agreement Effective Date, then we will be required to pay to GenFleet the remainder of the $10 million initial payment upon the first day of the 15th calendar month following the GenFleet Agreement Effective Date. Upon receipt of the first regulatory approval of a CDK9 Licensed Product and continuing throughout the term of the GenFleet Agreement, we will have the right to terminate the GenFleet Agreement upon one year’s prior written notice to GenFleet. In addition, we may terminate the GenFleet Agreement upon 90 days’ notice to GenFleet upon the occurrence of certain safety events described in the GenFleet Agreement.

GenFleet may terminate the GenFleet Agreement upon notice to us if we become in arrears in any payments due pursuant to the GenFleet Agreement and we fail to make the required payment within 60 days after the delivery of written notice from GenFleet. In addition, if we fail to meet the deadline for a diligence milestone event (as described in the GenFleet Agreement), GenFleet may treat such failure as a material breach which has not been cured and GenFleet will be entitled to terminate the GenFleet Agreement if such material breach is not cured within 90 days of receiving notice of such material breach.

At GenFleet’s request within 30 days of termination of the GenFleet Agreement, other than termination by us for GenFleet’s material breach following a cure period, we will grant GenFleet an option to enter into negotiations with us with respect to a license agreement pursuant to which we would grant GenFleet a non-exclusive, royalty-bearing, worldwide license for certain of our intellectual property that is necessary and used to develop, commercialize and manufacture the terminated products.

Manufacturing

We do not own or operate manufacturing facilities for the production of our product candidates, nor do we have plans to develop our own manufacturing operations in the foreseeable future. We currently depend on third-party contract manufacturers for all of our required raw materials, active pharmaceutical ingredients, and finished product candidate for our clinical trials. We do not have any current contractual arrangements for the manufacture of commercial supplies of any product candidates. We currently employ internal resources and third-party consultants to manage our manufacturing contractors.

GPS

34

Table of Contents

Our sole CMO for GPS drug substance peptides is Polypeptide Group. Our sole CMO for GPS drug product is Lyophilization Services of New England, Inc. (PCI Pharma Services). Our CMOs comply with cGMP requirements and manufacture product batches used in ongoing clinical trials. We anticipate the same CMOs to manufacture commercial batches. All batches for clinical trials meet release criteria and are monitored for long-term and accelerated stability.

We have significantly advanced the chemistry, manufacturing, and controls, or CMC, objectives in support of the GPS clinical development program and for licensure, including:

•Manufacturing lyophilized clinical GMP batches;

•Qualifying processes;

•Validating analytical methods; and

•Monitoring the stability program.

In the third quarter of 2023, based upon this work, we concluded a Type C meeting with the FDA regarding the CMC sections in a potential BLA for GPS. We had submitted a briefing package to FDA which provided an up-to-date overview of the extensive work we have completed for the GPS CMC program, including commercial manufacturing and regulatory plans. Following review of the package and accompanying questions to FDA, the FDA responded with positive guidance, including agreement on our proposed potency assay and manufacturing processes validation and our stability data generation plan for the commercial presentation of GPS. The current storage condition of GPS drug product is -20°C and we are collecting stability data to allow GPS to be stored in 2-8°C (36° – 46°F), which would be more optimal for supply chain logistics and would make it more accessible for end-users.

SLS009

In October 2022, we entered into a Clinical Supply Agreement with GenFleet pursuant to which GenFleet will manufacture and/or have manufactured through third parties (with which GenFleet entered into agreements and to which we have access, as necessary), and supply SLS009 and any back-up molecule or intermediary related to SLS009 (including all methods, forms, presentations, dosage strengths, dosage forms, and formulations), for our use in all research and development activities necessary to obtain, maintain or expand regulatory approval worldwide, except Greater China.

Sales and Marketing

The infrastructure required to commercialize oncology products is market and product dependent. For a rare disease, such as AML, a relatively focused infrastructure may be sufficient which would make it cost-effective for us to internally develop a marketing, access and reimbursement function, and field-based sales force. We will potentially build the infrastructure to commercialize our product candidates in North America and, possibly, Europe, if GPS or our other product candidates are approved by the FDA and other regulatory authorities. However, we will remain opportunistic in seeking strategic partnerships in these and other markets when advantageous and increase shareholder value.

The commercial infrastructure of specialty oncology products typically consists of a targeted, specialty sales force that calls on a limited and focused group of physicians supported by sales management, internal sales support, an internal marketing group, and distribution support. As GPS and our other product candidates may initially be developed for orphan indications with a relatively small number of treating physicians, we anticipate that a reduced infrastructure, including a small, targeted sales force, will be sufficient to support our sales and marketing objectives. We continue to assess the infrastructure and resources needed to establish our commercial operations and support other relevant commercial matters, such as pricing and market access.

We may elect in the future to utilize strategic partners, distributors, or contract sales forces and clinical nurse educators to assist in the commercialization of our products.

35

Table of Contents

In December 2020, we entered into the 3D Medicines Agreement for the development and commercialization of GPS, as well as the Company’s next generation heptavalent immunotherapeutic GPS+, which is at preclinical stage, across all therapeutic and diagnostic uses in Greater China. We have retained sole rights to GPS and GPS+ outside of Greater China. See Strategic Collaborations and License Agreements.

Intellectual Property

Our commercial success depends in part on our ability to avoid infringing the proprietary rights of third parties, our ability to obtain and maintain proprietary protection for our product candidates, technologies and know-how, and our ability to prevent others from infringing our proprietary rights. We seek to protect our proprietary position by, among other methods, evaluating relevant patents, establishing defensive positions, monitoring post grant proceedings in the US and foreign jurisdictions and pending intellectual property rights, preparing litigation strategies in view of the U.S. legislative framework, filing U.S. and international patent applications on technologies, inventions and improvements that are important to our business and maintaining our issued patents. We also include restrictions regarding use and disclosure of our proprietary information in our contracts with third parties, and utilize customary confidentiality and invention assignment agreements with our employees, consultants, clinical investigators, and scientific advisors to protect our confidential information and know-how. Together with our licensors, we also rely on trade secrets to protect our combined technology especially where we do not believe patent protection is appropriate or obtainable. It is our policy to operate without knowingly infringing on, or misappropriating, the proprietary rights of others.

The term of individual patents depends upon the legal term of the patents in countries in which they are obtained. In most countries, including the United States, the patent term is generally 20 years from the earliest date of filing a non-provisional patent application in the applicable country. In the United States, a patent’s term may, in certain cases, be lengthened by patent term adjustment, which compensates a patentee for administrative delays by the U.S. Patent and Trademark Office in examining and granting a patent or may be shortened if a patent is terminally disclaimed over a commonly owned patent or a patent naming a common inventor and having an earlier expiration date.

The patent term of a patent that covers an FDA-approved drug may also be eligible for patent term extension, which permits patent term restoration as compensation for the patent term lost during the FDA regulatory review process. The Drug Price Competition and Patent Term Restoration Act of 1984, or the Hatch-Waxman Act, permits a patent term extension of up to five years beyond the expiration of the patent. The length of the patent term extension is related to the length of time the drug is under regulatory review. Patent term extension cannot extend the remaining term of a patent beyond a total of 14 years from the date of product approval, and only one patent applicable to an approved drug may be extended. Similar provisions are available in Europe and certain other foreign jurisdictions to extend the term of a patent that covers an approved drug. In the future, if and when our product candidates receive approval by the FDA or foreign regulatory authorities, we expect to apply for patent term extensions on issued patents covering those products, depending upon the length of the clinical trials for each drug and other factors.

Our patent portfolio includes the following:

Patents and patent applications covering GPS and WT1-targeting peptides:

•Patents and patent applications co-owned by us and MSK:

◦Patent applications covering a heptavalent (7-peptide) immunotherapy composition and methods of use for treating, reducing the incidence of, or inducing an immune response against a WT1-expressing cancer pending in the United States, Australia, Canada, China, European Patent Office (or EPO), Hong Kong, India, Japan, South Korea, and Mexico, which, if granted, are expected to expire in 2040.

◦Patents covering a heptavalent (7-peptide) immunotherapy composition and uses thereof for treating, reducing the incidence of, or inducing an immune response against a WT1-expressing cancer in Israel and Russia, which are expected to expire in 2040.

36

Table of Contents

•Patents and patent applications in-licensed from MSK:

◦Composition-of-matter patents covering certain WT1-targeting peptides and methods of use in the United States, which are expected to expire in 2034; and a composition-of-matter patent covering additional WT1-targeting peptides and methods of use in the United States, which is expected to expire in 2035;

◦Composition-of-matter patents covering certain WT1-targeting peptides and methods of use in Australia, Canada, China, Hong Kong, several countries in Europe, and Japan, which are expected to expire in 2034;

◦Patent applications covering certain WT1-targeting peptides and methods of use pending in the United States, Australia, the EPO, Canada, China, and Hong Kong, which, if granted, are expected to expire in 2034;

◦Patents covering methods for treating, reducing the incidence of, or inducing an immune response against a WT1-expressing cancer, using the peptides of GPS in combination with anti-PD-1 antibody checkpoint inhibitors in the United States, Australia, China, Hong Kong, several countries in Europe, South Korea, and Japan, which are expected to expire in 2037 (United States) and 2036 (Australia, China, Hong Kong, Europe and Japan);

◦Patent applications covering methods for treating, reducing the incidence of, or inducing an immune response against a WT1-expressing cancer, using the peptides of GPS in combination with immune checkpoint inhibitors pending in the United States, Australia, Canada, China, Hong Kong, the EPO, South Korea, and Japan, which, if granted, are expected to expire in 2036;

◦Composition-of-matter patents covering the WT1-A1 peptide of GPS in the United States, which are expected to expire in 2026;

◦Composition-of-matter patent covering the WT1-427 long and WT1-331 long peptides of GPS issued in the United States, which is expected to expire in 2031, and patents covering the methods of use in the United States, which are expected to expire in 2026; a patent covering nucleic acids encoding the WT1-427 long and WT1-331 long peptides of GPS and methods of use thereof in the United States, which are expected to expire in 2026; a patent covering peptide conjugates of the WT1-427 long peptide or WT1-331 long peptide in the United States, which is expected to expire in 2027; a patent covering nucleic acids encoding peptide conjugates of the WT1-427 long peptide or WT1-331 long peptide and methods of use thereof in the United States, which is expected to expire in 2029; and a patent application covering peptide conjugates of the WT1-427 long peptide or WT1-331 long peptide pending in the United States, which, if granted, is expected to expire in 2026;

◦Composition-of-matter patents covering the WT1-427 long peptide of GPS and WT1-331 long peptide of GPS, and methods of use, in Australia, Canada, several countries in Europe, and Hong Kong, which are expected to expire in 2026;

◦Composition-of-matter patent covering a WT1-specific peptide in the United States, which is expected to expire in 2026;

◦Composition-of-matter patent covering the WT1-122A1 long peptide of GPS in the United States which is expected to expire in 2033; patent covering methods of using the WT1-122A1 long peptide of GPS in the United States, which is expected to expire in 2029; and patent application covering the WT1-122A1 long peptide of GPS and methods of use thereof pending in the United States, which, if granted, is expected to expire in 2027; and

◦Composition-of-matter patent covering the WT1-122A1 long peptide of GPS and methods of use in several countries in Europe, which is expected to expire in 2027, and patent applications covering the WT1-122A1 long peptide of GPS and methods of use pending in the EPO and Canada, which, if granted, are expected to expire in 2027.

37

Table of Contents

Patents and patent applications covering SLS009:

•Patents and patent applications in-licensed from GenFleet:

◦Composition-of-matter patents covering SLS009 and use thereof in the treatment or amelioration of cancer in the United States, Australia, Brazil, Canada, Japan, Russia, South Korea, and several countries in Europe, which are expected to expire in 2038; and

◦Patents covering maleate and fumarate polymorphs of SLS009 and uses thereof in prevention or treatment of CDK9-related diseases, including cancer, in the United States, Australia, Canada, Eurasian Patent Office, South Korea, and Japan, which are expected to expire in 2042 (United States) and 2040 (Australia, Canada, Eurasian Patent Office, South Korea, and Japan); patent applications covering maleate and fumarate salt forms and polymorphs of SLS009, syntheses thereof, and use thereof in prevention or treatment of CDK9-related diseases, including cancer, pending in the United States, Brazil, the EPO, and the Eurasian Patent Office, which, if granted, are expected to expire in 2040.

•Patents and patent applications owned by us:

◦Patent applications covering methods of treating cancer in a subject having an ASXL1 mutation using CDK9 inhibitors in the Patent Cooperation Treaty (PCT) and Taiwan, which, if granted, are expected to expire in 2045.

Competition

Oncology in general, and specifically, cancer immunotherapy, is a significant growth area for the biopharmaceutical industry, attracting large pharmaceutical companies as well as small niche players. While we believe that our scientific knowledge, assets, development experience and ability to attract experienced commercial professionals provide us with competitive advantages, we face potential competition from many different sources, including major pharmaceutical, specialty pharmaceutical and biotechnology companies, which either alone or together with their collaborative partners, have substantially greater resources than we have.

Generally, our competitors in the oncology therapeutic market are large and mid-sized companies with approved oncology therapeutic products and companies currently engaged in clinical development of such products. Any product candidates that we successfully develop and commercialize may compete with these existing therapies and new therapies that may become available in the future.

Companies developing novel products with similar indications to those we are pursuing and may pursue are expected to influence our ability to penetrate and maintain market share. Principal competitors for AML broadly include companies with currently marketed products, such as AbbVie/Genentech (Venclexta), Pfizer (Mylotarg), Daiichi-Sankyo (Vanflyta), Rigel Pharmaceuticals (Rezlidhia), Syndax Pharmaceuticals (Revumenib) and Bristol Myers Squibb (Vidaza and Onureg), among others. There are also companies developing therapies to treat AML in the r/r setting, which are in earlier stages of clinical development, including emavusertib, which is in a Phase 1/2 trial in AML and being developed by Curis, and later-stage clinical development candidates which may enter the market before our potential products, such as Delta-Fly Pharma (DFP-10917) and AROG Pharmaceuticals (crenolanib).

With respect to WT1-targeting therapies, we do not believe GPS has direct competition in AML in the maintenance setting after CR2 at this time. While there are companies engaged in the clinical development of WT-1 targeting therapies, they are not currently focused on AML or have since discontinued or paused their development of WT-1 targeting therapies.

With respect to SLS009, we anticipate competition from companies who have been engaged in the clinical development of selective CKD9-targeting therapies. There are other companies which are in early development stages for their CDK9 inhibitors and targeting other hematologic malignancies or solid tumors, including Sumitomo Dainippon Pharma (TP-1287), Cothera Bioscience (zotiraciclib), and Prelude Therapeutics (PRT2527).

38

Table of Contents

With regard to both GPS and SLS009, many of our competitors, either alone or with their strategic partners, may have substantially greater resources and expertise in research and development, manufacturing, preclinical testing, obtaining regulatory approvals, and marketing approved products than we have. Mergers and acquisitions in the biotechnology, pharmaceutical and diagnostics industries may result in even more resources being concentrated among a smaller number of our competitors. These competitors also compete with us in recruiting and retaining qualified scientific and management personnel, the ability to work with specific clinical contract organizations due to conflict of interest, and also the conduct of trials in the ability to recruit clinical trial sites and subjects for our clinical trials. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. These activities may lead to consolidated efforts that allow for more rapid development of cancer immunotherapy product candidates.

We expect the key competitive factors that could affect the success of any products that we develop and commercialize are likely to be efficacy, safety, price, level of generic competition, placement (or lack thereof) in clinical treatment guidelines and the availability of reimbursement from government and other third-party payors. Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize products that are viewed as safer, more convenient or less expensive than any products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for our current product candidates or any other future product candidate, which could result in our competitors establishing a strong market position before we are able to enter the market. In addition, our ability to complete may be affected by insurers or other third-party payors seeking to encourage the use of generic or biosimilar products. If our therapeutic product candidates are approved, we believe that they would be priced at a premium over competitive generic products.

Employees and Human Capital

We have assembled a management team of biopharmaceutical experts with extensive experience in building and operating organizations that develop and deliver innovative medicines to patients with cancer. Our management team has broad expertise and successful track records in clinical development and approval of cancer therapies.

As of March 1, 2026, we had 13 full-time employees. In addition to our full-time employees, we engage various independent consultants and advisors to support key areas of our business. None of our employees are represented by a labor union or covered by collective bargaining agreements. We believe our relationship with our employees is good.

Our employees have various backgrounds, experience, and perspectives. For example, as of March 1, 2026, of our 13 employees, 54% are women, 31% are racial or ethnic minorities, and 54% have advanced degrees. In addition, two of our six Board of Director members are women. We believe we have built and continue to build a strong diverse and inclusive culture of cooperation, respect and acceptance.

We are committed to identifying, retaining, and incentivizing highly skilled employees, and we are able to recruit talented individuals through our competitive benefits, compensation packages and health and wellness initiatives, which are based on peer company benchmarks.

Government Regulation

The FDA and other regulatory authorities at federal, state, and local levels, as well as in foreign countries, extensively regulate, among other things, the research, development, testing, manufacture, quality control, import, export, safety, effectiveness, labeling, packaging, storage, distribution, record keeping, approval, advertising, promotion, marketing, post-approval monitoring, and post-approval reporting of drugs and biologics such as those we are developing. Along with our third-party contractors, we will be required to navigate the various preclinical, clinical and commercial approval requirements of the governing regulatory agencies of the countries in which we wish to conduct studies or seek approval or licensure of its current or future product candidates. The process of obtaining regulatory approvals and the subsequent compliance with appropriate federal, state, local, and foreign statutes and regulations require the expenditure of substantial time and financial resources. A company can make only those claims relating to safety and efficacy, purity and potency that are approved by the FDA and in accordance with the provisions of the approved label.

39

Table of Contents

A biologic candidate is licensed by the FDA through approval of a biologics license application, or BLA. Assuming we receive positive data from our REGAL clinical trial of GPS in patients with AML, we will submit a BLA to the FDA. A drug candidate must be approved by the FDA through a new drug application, or NDA. For SLS009, we will seek marketing approval through the submission of an NDA to the FDA. The process required by the FDA before drug or biological product candidates may be marketed in the United States generally involves the following:

•completion of extensive nonclinical laboratory tests and animal studies performed in accordance with the FDA’s current good laboratory practice, or GLP, regulations and other applicable regulations;

•submission to the FDA of an IND application, which must become effective before clinical trials may begin and must be updated annually or when significant changes are made;

•approval by an institutional review board, or IRB, or ethics committee at each clinical site before the trial is initiated at such sites;

•performance of adequate and well-controlled human clinical trials in accordance with good clinical practice, or GCP, and other clinical-trial related regulations to establish the safety and efficacy of the investigational product candidate for its proposed indication;

•preparation of and submission to the FDA of an NDA or BLA, after completion of all pivotal clinical trials;

•a determination by the FDA within 60 days of its receipt of an NDA or BLA to file the application for review;

•satisfactory completion of an FDA pre-approval inspection of the manufacturing facility or facilities at which the proposed product is produced to assess compliance with current good manufacturing practice, or cGMP, regulations and to assure that the facilities, methods and controls are adequate to preserve the product’s continued identity, strength, quality and purity for a drug and safety, purity and potency for a biologic;

•potential audit of selected clinical trial sites to assess compliance with GCP and the integrity of the clinical data submitted in support of the NDA or BLA; and

•satisfactory completion of an FDA Advisory Committee review, if applicable;

•FDA review and approval of the NDA or BLA to permit commercial marketing of the product for particular indications for use in the United States.

The testing and approval process requires substantial time, effort and financial resources, and we cannot be certain that any approvals for our current or future product candidates will be granted on a timely basis, if at all.

Preclinical testing

Before testing any drug or biological product candidate, including our product candidates, in humans, the product candidate must undergo rigorous preclinical testing. Nonclinical studies during the preclinical development stage include laboratory evaluation of product chemistry and formulation and typically include in vitro and animal studies to assess the potential for adverse events and in some cases to establish a rationale for therapeutic use. The Consolidated Appropriations Act for 2023, signed into law on December 29, 2022, (P.L. 117-328) amended the Food, Drug, and Cosmetic Act, or the FDCA, and the Public Health Service Act to specify that nonclinical testing for drugs and biologics may, but is not required to, include in vivo animal testing. According to the amended language,

40

Table of Contents

a sponsor may fulfill nonclinical testing requirements by completing various in vitro assays (e.g., cell-based assays, organ chips, or microphysiological systems), in silico studies (i.e., computer modeling), other human or nonhuman biology-based tests (e.g., bioprinting), or in vivo animal tests. The conduct of preclinical studies is subject to federal regulations and requirements, including GLP regulations for safety/toxicology studies. Some long-term preclinical testing, such as animal tests of reproductive adverse events and carcinogenicity, may continue after an IND for an investigational drug or biologic candidate is submitted to the FDA and human clinical trials have been initiated.

Prior to beginning the first clinical trial with a product candidate, we must submit an IND to the FDA. An IND is a request for authorization from the FDA to administer an investigational new drug product to humans. The central focus of an IND submission is on the general investigational plan and the protocol(s) for clinical studies. The IND also includes the results of the nonclinical studies of the product candidate, together with manufacturing information, analytical data, any available clinical data or literature. An IND must become effective before human clinical trials may begin. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, issues a notice expressly authorizing the proposed trial to proceed or raises safety concerns or questions about the proposed clinical trial. If the FDA raises concerns or places the trial on clinical hold, the IND may be placed on clinical hold and the IND sponsor and the agency must resolve any outstanding concerns or questions before the proposed trial can begin. Submission of an IND therefore may or may not result in FDA authorization to begin a clinical trial.

Human clinical trials in support of an NDA or BLA

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCP and other trial-related regulations, which include, among other things, the requirement that all research subjects provide their informed consent for their participation in any clinical trial. Clinical trials are conducted under protocols detailing, among other things, the objectives of the clinical trial, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. A separate submission to the existing IND must be made for each successive clinical trial conducted during product development and for any subsequent protocol amendments. Furthermore, an IRB for each site proposing to conduct the clinical trial must review and approve the plan for any clinical trial and its informed consent form before the clinical trial begins at that site and must monitor the clinical trial until completed. Regulatory authorities, the IRB or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the subjects are being exposed to an unacceptable health risk or that the trial is unlikely to meet its stated objectives. Some studies also include oversight by an independent data safety monitoring board, or DSMB, organized by the clinical trial sponsor, which at designated check points based on access to certain data from the clinical trial may recommend that the sponsor halt the trial if the DSMB determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy.

Information about certain clinical trials, including details of the protocol and eventually study results, also must be submitted within specific timeframes to the NIH for public dissemination on the ClinicalTrials.gov data registry. Information related to the product, patient population, phase of investigation, study site locations and other aspects of the clinical trial is made public as part of the registration of the clinical trial. Sponsors are also obligated to disclose the results of their clinical trials after completion. Disclosure of the results of these trials can be delayed in some cases for up to two years after the date of completion of the trial. Competitors may use this publicly available information to gain knowledge regarding the progress of development programs. Failure to timely register a covered clinical trial or to submit study results as provided for in the law can give rise to civil monetary penalties and also prevent the non-compliant party from receiving future grant funds from the federal government. The NIH Final Rule on ClinicalTrials.gov registration and reporting requirements became effective in 2017, and both NIH and FDA have brought enforcement actions against non-compliant clinical trial sponsors.

For purposes of NDA or BLA approval, human clinical trials are typically conducted in three sequential phases that may overlap.

•Phase 1-The investigational product is initially introduced into healthy human subjects or patients with the target disease or condition. These studies are designed to test the safety, dosage tolerance, absorption, metabolism, distribution, and excretion of the investigational product in humans, the side effects associated with increasing doses, and, if possible, to gain early evidence on effectiveness.

41

Table of Contents

•Phase 2-The investigational product is administered to a limited patient population with a specified disease or condition to evaluate the preliminary efficacy, optimal dosages and dosing schedule and to identify possible adverse side effects and safety risks. Multiple Phase 2 clinical trials may be conducted to obtain information prior to beginning larger and more expensive Phase 3 clinical trials.

•Phase 3-The investigational product is administered to an expanded patient population to further evaluate dosage, to provide statistically significant evidence of clinical efficacy and to further test for safety, generally at multiple geographically dispersed clinical trial sites. These clinical trials are intended to establish the overall risk/benefit ratio of the investigational product and to provide an adequate basis for product approval and labeling. These trials may include comparisons with placebo and/or other comparator treatments. The duration of treatment is often extended to mimic the actual use of a product during marketing.

•Phase 4-In some cases, the FDA may require, or companies may voluntarily pursue, additional clinical trials after a product is approved to gain additional information and experience from the treatment of patients in the intended therapeutic indication, particularly for long-term safety follow up. These so-called Phase 4 studies may be made a condition to approval of the BLA or NDA.

In the Consolidated Appropriations Act for 2023, Congress amended the FDCA to require sponsors of a Phase 3 clinical trial, or other “pivotal study” of a new drug to support marketing authorization, to submit a diversity action plan for such clinical trial. The action plan must include the sponsor’s diversity goals for enrollment, as well as a rationale for the goals and a description of how the sponsor will meet them. A sponsor must submit a diversity action plan to FDA by the time the sponsor submits the trial protocol to the agency for review. The FDA may grant a waiver for some or all of the requirements for a diversity action plan. To grant a waiver, FDA must determine that the prevalence or incidence of the disease or condition being studied makes it impracticable to conduct a clinical trial in accordance with a diversity action plan, or that a waiver is necessary to protect public health during a public health emergency. Our Phase 3 REGAL trial of GPS for AML patients who have achieved CR2 was initiated before this requirement became effective, but for any future Phase 3 trials we plan to conduct, we must submit a diversity action plan to the FDA by the time we submit plans for such Phase 3, or pivotal study, protocol to the agency for review as part of an IND, unless we are able to obtain a waiver for some or all of the requirements for a diversity action plan. If FDA objects to a sponsor’s diversity action plan and requires the sponsor to amend the plan or take other actions, it may delay trial initiation.

Phase 1, Phase 2 and Phase 3 testing may not be completed successfully within a specified period, if at all, and there can be no assurance that the data collected will support FDA approval or licensure of the product.

Progress reports detailing the progress of and safety data from the clinical trials must be submitted at least annually to the FDA and more frequently if unexpected serious adverse events, or SAEs, occur. The FDA or the sponsor may suspend or terminate a clinical trial at any time on various grounds, including a finding that the research subjects or patients are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the clinical protocol, GCP regulations, or other IRB requirements or if the drug has been associated with unexpected serious harm to patients.

Concurrent with clinical trials, companies may complete additional nonclinical studies and develop additional information about the biological characteristics of the product candidate and must finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements. The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, must incorporate methods for testing the identity, strength, quality and purity of the final product, or for biologics, the safety, purity and potency. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life.

Marketing Application Submission and Review by the FDA

42

Table of Contents

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, the results of product development, preclinical studies and clinical trials are submitted to the FDA as part of an NDA or BLA requesting approval to market the product for one or more indications. The NDA or BLA must contain proof of the product candidate’s safety and substantial evidence of effectiveness for its proposed indication or indications in the form of relevant data available from pertinent preclinical and clinical studies, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls, and proposed labeling, among other things. In particular, a marketing application must demonstrate that the manufacturing methods and quality controls used to produce the drug or biological product are adequate to preserve the drug’s identity, strength, quality, and purity for an NDA or a biologic’s safety, purity, and potency for a BLA. Data can come from company-sponsored clinical studies intended to test the safety and effectiveness of a use of the product, or from a number of alternative sources, including studies initiated by investigators. FDA approval of an NDA or BLA must be obtained before the corresponding drug or biologic may be marketed in the United States.

Under federal law, the fee for the submission of an NDA or BLA for which clinical data is submitted and analyzed is substantial, and the sponsor of an approved NDA or BLA is also subject to an annual program fee. These fees are typically increased annually, but exemptions and waivers may be available under certain circumstances (such as a waiver for the first human drug application submitted by a qualifying small business and exemptions for orphan products).

The FDA reviews all submitted NDAs and BLAs to determine if they are substantially complete before it accepts them for filing and may request additional information rather than accepting a submission for filing. The FDA must make a decision on accepting an NDA or BLA for filing within 60 days of receipt and must inform the sponsor by the 74th day after the FDA’s receipt of the submission whether the application is sufficiently complete to permit substantive review. The FDA may refuse to file any submission that it deems incomplete or not properly reviewable at the time of submission and may request additional information. In this event, the marketing application must be resubmitted with the additional information requested by the agency. The resubmitted application is also subject to review before the FDA accepts it for filing.

Once an NDA or BLA is accepted for filing, the FDA’s goal is to review the application within 10 months after it accepts the application for filing, or, if the application meets the criteria for “priority review”, within six months after the FDA accepts the application for filing. The review process is often significantly extended by FDA requests for additional information or clarification after the NDA or BLA has been accepted for filing. The review process may be extended by the FDA for three additional months to consider new information or in the case of a clarification provided by the applicant to address an outstanding deficiency identified by the FDA following the original submission.

During the review process, the FDA reviews the NDA or BLA to determine, among other things, whether the product is safe, effective, pure and potent and whether the facility in which it is manufactured, processed, packed, or held meets standards designed to assure the product’s continued safety, quality, purity and potency. The FDA may refer any NDA or BLA, including applications for novel drug or biologic candidates which present difficult questions of safety or efficacy, to an advisory committee to provide clinical insight on application review questions. Typically, an advisory committee is a panel of independent experts, including clinicians and other scientific experts, that reviews, evaluates and provides a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendation of an advisory committee, but it considers such recommendations carefully when making final decisions on approval.

Before approving an NDA or BLA, the FDA will typically inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMP requirements and adequate to assure consistent production of the product within required specifications. Additionally, before approving an NDA or BLA, the FDA will typically inspect one or more clinical trial sites to assure compliance with GCP and integrity of the trial data. If the FDA determines that the application, manufacturing process or manufacturing facilities are not acceptable, it will outline the deficiencies as part of the review process and often will request additional testing or information. Notwithstanding the submission of

43

Table of Contents

any requested additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval.

Under the Pediatric Research Equity Act, or PREA, amendments to the FDCA, an NDA or BLA or supplement to such applications must contain data that are adequate to assess the safety and efficacy of the product candidate for the claimed indications in all relevant pediatric populations and to support dosing and administration for each pediatric population for which the product is safe and effective. The FDA may grant deferrals for submission of pediatric data or full or partial waivers. The PREA requires a sponsor that is planning to submit a marketing application for a product that includes a new active ingredient, new indication, new dosage form, new dosing regimen or new route of administration to submit an initial Pediatric Study Plan, or PSP, within 60 days of an end of-Phase 2 meeting or, if there is no such meeting, as early as practicable before the initiation of the Phase 3 or Phase 2/3 clinical trial. The initial PSP must include an outline of the pediatric study or studies that the sponsor plans to conduct, including trial objectives and design, age groups, relevant endpoints and statistical approach, or a justification for not including such detailed information, and any request for a deferral of pediatric assessments or a full or partial waiver of the requirement to provide data from pediatric studies along with supporting information. The FDA and the sponsor must reach an agreement on the PSP. A sponsor can submit amendments to an agreed upon initial PSP at any time if changes to the pediatric plan need to be considered based on data collected from preclinical studies, early-phase clinical trials or other clinical development programs.

The testing and approval process requires substantial time, effort and financial resources, and each may take several years to complete. The FDA may not grant approval on a timely basis, or at all, and we may encounter difficulties or unanticipated costs in our efforts to secure necessary governmental approvals, which could delay or preclude us from marketing our products. After the FDA evaluates an NDA or BLA and conducts inspections of the manufacturing facilities where the investigational product and/or its drug substance will be produced, the FDA may issue an approval letter or a Complete Response Letter, or CRL. An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A CRL indicates that the review cycle of the application is complete and the application will not be approved in its present form. A CRL generally outlines the deficiencies in the submission and may require substantial additional testing, information or clarification for FDA to reconsider the application. The FDA may delay or refuse approval of an NDA or BLA if applicable regulatory criteria are not satisfied, require additional testing or information and/or require post-marketing testing and surveillance to monitor safety or efficacy of a product. In September 2025, the FDA began publishing CRLs soon after issuing them to the respective sponsors, breaking with long standing agency tradition of publishing CRLs with approval documentation after the product is approved. If a CRL is issued, the applicant may either resubmit the NDA or BLA, addressing all of the deficiencies identified in the letter, or withdraw the application. If and when the deficiencies have been addressed to the FDA’s satisfaction in a resubmission of the marketing application, the FDA will issue an approval letter. The FDA has committed to reviewing such resubmissions in response to an issued CRL in either two or six months depending on the type of information included. Even if such data and information are submitted, the FDA may ultimately decide that the NDA or BLA does not satisfy the criteria for approval.

If regulatory approval of a product is granted, such approval is limited to the conditions of use (e.g., patient population, indication) described in the application and may entail further limitations on the indicated uses for which such product may be marketed. For example, the FDA may approve the NDA or BLA with a Risk Evaluation and Mitigation Strategy, or REMS, plan to mitigate risks, which could include medication guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. The FDA determines the requirement for a REMS, as well as the specific REMS provisions, on a case-by-case basis. If the FDA concludes a REMS plan is needed, the sponsor of the NDA or BLA must submit a proposed REMS. The FDA will not approve an NDA or BLA without a REMS, if one is required. The FDA also may condition approval on, among other things, changes to proposed labeling (e.g., adding contraindications, warnings or precautions) or the development of adequate controls and specifications. Once approved, the FDA may withdraw the product approval if compliance with pre- and post-marketing regulatory standards is not maintained or if problems occur after the product reaches the marketplace. The FDA may require one or more Phase 4 post-market studies and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization and may limit further marketing of the product based on the results of these post-marketing studies. After approval, some types of changes to the approved product, such as adding new indications, manufacturing changes and additional labeling claims, are subject to further testing requirements and FDA review and approval. In addition, new government requirements, including those resulting from new legislation,

44

Table of Contents

may be established, or the FDA’s policies may change, which could delay or prevent regulatory approval of our products under development.

Fast Track, Priority Review, and Breakthrough Therapy Designations

A sponsor may seek approval of its product candidate under programs designed to accelerate FDA’s review and approval of new drugs and biological products that meet certain criteria. Specifically, new drugs and biological products are eligible for Fast Track designation if they are intended to treat a serious or life-threatening condition and demonstrate the potential to address unmet medical needs for the condition. Fast Track designation provides increased opportunities for sponsor interactions with the FDA during preclinical and clinical development, in addition to the potential for rolling review once a marketing application is filed, meaning that the FDA may consider for review sections of the NDA or BLA on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the NDA or BLA, the FDA agrees to accept sections of the marketing application and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the application. A Fast Track designated product candidate may also qualify for accelerated approval (described below) or priority review, under which the FDA sets the target date for FDA action on the NDA or BLA at six months after the FDA accepts the application for filing. We have obtained Fast Track designation for GPS in AML, MPM and MM, and for SLS009 in r/r AML and r/r PTCL.

Priority review is granted when there is evidence that the proposed product would be a significant improvement in the safety or effectiveness of the treatment, diagnosis, or prevention of a serious condition. Significant improvement may be illustrated by evidence of increased effectiveness in the treatment of a condition, elimination or substantial reduction of a treatment-limiting drug reaction, documented enhancement of patient compliance that may lead to improvement in serious outcomes, or evidence of safety and effectiveness in a new subpopulation. If criteria are not met for priority review, the application is subject to the standard FDA review period of ten months after FDA accepts the application for filing.

A sponsor may seek FDA designation of its product candidate as a Breakthrough Therapy, if the product candidate is intended, alone or in combination with one or more other drugs or biologics, to treat a serious or life-threatening disease or condition and preliminary clinical evidence indicates that the therapy may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. Breakthrough Therapy designation provides all the features of Fast Track designation in addition to intensive guidance on an efficient development program beginning as early as Phase 1, and FDA organizational commitment to expedited development, including involvement of senior managers and experienced review and regulatory staff in a proactive, collaborative, cross-disciplinary review, where appropriate. A drug designated as Breakthrough Therapy is also eligible for accelerated approval if the relevant criteria are met.

In 2025, the FDA created a new voucher program called the Commissioner’s National Priority Voucher (“CNPV”) with the goal of radically expediting the drug and biological product review and approval process. The agency may award a CNPV to a company or a specific product candidate that demonstrates alignment with certain national health priorities. The FDA aims to take action on a marketing application for which a CNPV is used within one to two months after the filing date.

Even if a product qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened. None of these programs changes the scientific or medical standards for approval or the quality of evidence necessary to support approval but may expedite the development or approval process.

Accelerated Approval

In addition, products studied for their safety and effectiveness in treating serious or life-threatening illnesses and that provide meaningful therapeutic benefit over existing treatments may receive accelerated approval from the FDA and may be approved on the basis of adequate and well-controlled clinical trials establishing that the drug product has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit. The FDA may also grant

45

Table of Contents

accelerated approval for such a drug or biologic when it has an effect on an intermediate clinical endpoint that can be measured earlier than an effect on irreversible morbidity or mortality, or IMM, and that is reasonably likely to predict an effect on IMM or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments. As a condition of approval, the FDA may require that a sponsor of a drug or biologic receiving accelerated approval perform post-marketing clinical trials to verify and describe the predicted effect on IMM or other clinical endpoint, and the product may be subject to expedited withdrawal procedures. Drugs and biologics granted accelerated approval must meet the same statutory standards for safety and effectiveness as those granted traditional approval.

For the purposes of accelerated approval, a surrogate endpoint is a marker, such as a laboratory measurement, radiographic image, physical sign, or other measure that is thought to predict clinical benefit but is not itself a measure of clinical benefit. Surrogate endpoints can often be measured more easily or more rapidly than clinical endpoints. An intermediate clinical endpoint is a measurement of a therapeutic effect that is considered reasonably likely to predict the clinical benefit of a drug or biologic, such as an effect on IMM. The FDA has limited experience with accelerated approvals based on intermediate clinical endpoints but has indicated that such endpoints generally may support accelerated approval when the therapeutic effect measured by the endpoint is not itself a clinical benefit and basis for traditional approval, if there is a basis for concluding that the therapeutic effect is reasonably likely to predict the ultimate long-term clinical benefit of a drug or biologic.

The accelerated approval pathway is most often used in settings in which the course of a disease is long and an extended period of time is required to measure the intended clinical benefit of a drug, even if the effect on the surrogate or intermediate clinical endpoint occurs rapidly. For example, accelerated approval has been used extensively in the development and approval of drugs and biologics for treatment of a variety of cancers in which the goal of therapy is generally to improve survival or decrease morbidity and the duration of the typical disease course requires lengthy and sometimes large clinical trials to demonstrate a clinical or survival benefit.

The accelerated approval pathway is usually contingent on a sponsor’s agreement to conduct, in a diligent manner, additional post-approval confirmatory studies to verify and describe the product candidate’s clinical benefit. As a result, a product candidate approved on this basis is subject to rigorous post-marketing compliance requirements, including the completion of Phase 4 or post-approval clinical trials to confirm the effect on the clinical endpoint. Failure to conduct required post-approval studies, or to confirm the predicted clinical benefit of the product during post-marketing studies, would allow the FDA to withdraw approval of the product. As part of the Consolidated

Appropriations Act for 2023, Congress provided the FDA additional statutory authority to mitigate potential risks to

patients from continued marketing of ineffective drugs or biologics previously granted accelerated approval. Under

the act’s amendments to the FDCA, the FDA may require the sponsor of a product being considered for accelerated approval to have a confirmatory trial underway prior to approval. The sponsor must also submit progress reports on a confirmatory trial every six months until the trial is complete, and such reports are published on the FDA’s website. The amendments also give the FDA the option of using expedited procedures to withdraw product approval if the sponsor’s confirmatory trial fails to verify the claimed clinical benefits of the product.

All promotional materials for product candidates being considered and approved under the accelerated approval program are subject to prior review by the FDA.

Orphan Drugs

Under the Orphan Drug Act, the FDA may grant Orphan Drug Product Designation to a drug or biologic intended to treat a rare disease or condition, defined as a disease or condition with a patient population of fewer than 200,000 individuals in the United States, or a patient population greater than 200,000 individuals in the United States and when there is no reasonable expectation that the cost of developing and making available the drug or biologic in the United States will be recovered from sales in the United States for that drug or biologic. Orphan Drug Product Designation must be requested before submitting an NDA or BLA. After the FDA grants Orphan Drug Product Designation, the generic identity of the therapeutic agent and its potential orphan use are disclosed publicly by the FDA.

46

Table of Contents

If a drug or biologic product that has Orphan Drug Product Designation subsequently receives the first FDA approval for a particular active ingredient for the disease for which it has such designation, the product is entitled to orphan product exclusivity, which means that the FDA may not approve any other applications, including a full NDA or BLA, to market the same drug or biologic for the same indication for seven years, except in limited circumstances, such as a showing of clinical superiority to the product with orphan product exclusivity or if FDA finds that the holder of the orphan product exclusivity has not shown that it can assure the availability of sufficient quantities of the orphan product to meet the needs of patients with the disease or condition for which the drug or biologic was designated. Orphan product exclusivity does not prevent the FDA from approving a different drug or biologic for the same disease or condition, or the same drug or biologic for a different disease or condition. Among the other benefits of Orphan Drug Product Designation are tax credits for certain research and a waiver of NDA or the BLA application user fee.

A drug or biologic with Orphan Drug Product Designation may not receive orphan product exclusivity if it is approved for a use that is broader than the indication for which it received Orphan Drug Product Designation. In addition, orphan product exclusive marketing rights in the United States may be lost if the FDA later determines that the request for designation was materially defective or if the manufacturer is unable to assure sufficient quantities of the product to meet the needs of patients with the rare disease or condition.

Court cases have challenged FDA’s approach to determining the scope of orphan drug exclusivity; however, at this time the agency continues to apply its long-standing interpretation of the governing regulations and has stated that it does not plan to change any orphan drug implementing regulations.

We have obtained Orphan Drug Product Designation in the United States for GPS in AML, MPM and MM and for SLS009 for AML and PTCL.

Pediatric exclusivity

Pediatric exclusivity is a type of non-patent marketing exclusivity available in the United States and, if granted, it provides for the attachment of an additional six months of marketing protection to the term of any existing regulatory exclusivity or listed patents. This six-month exclusivity may be granted if an NDA or BLA sponsor submits pediatric data that fairly respond to a written request from the FDA for such data. The data do not need to show the product to be effective in the pediatric population studied; rather, if the clinical trial is deemed to fairly respond to the FDA’s request, the additional protection is granted. If reports of requested pediatric studies are submitted to and accepted by the FDA within the statutory time limits, whatever statutory or regulatory periods of exclusivity or patent protection cover the product are extended by six months. This is not a patent term extension, but it effectively extends the regulatory period during which the FDA cannot approve another application. The issuance of a written request does not require the sponsor to undertake the described studies.

Patent term restoration

Depending upon the timing, duration and specifics of FDA approval of the use of our product candidates, some of our United States patents may be eligible for limited patent term extension under the Hatch-Waxman Act. The Hatch-Waxman Act permits a patent restoration term of up to five years as compensation for patent term lost during product development and the FDA regulatory review process. However, patent term restoration cannot extend the remaining term of a patent beyond a total of 14 years from the product candidate’s approval date. The patent term restoration period is generally one half of the time between the effective date of an IND and the submission date of an NDA or BLA, plus the time between the submission date of the NDA or BLA and the approval of that application, except that the review period is reduced by any time during which the applicant failed to exercise due diligence. Only one patent applicable to an approved product candidate is eligible for the extension and the application for extension must be made prior to expiration of the patent. The USPTO, in consultation with the FDA, reviews and approves the application for any patent term extension or restoration. In the future, we intend to apply for restorations of patent term for some of our currently owned or licensed patents to add patent life beyond their current expiration date, depending on the expected length of clinical trials and other factors involved in the submission of the relevant NDA or BLA.

Abbreviated new drug applications for generic drugs

47

Table of Contents

In 1984, with passage of the Drug Price Competition and Patent Term Restoration Act, or Hatch-Waxman Act, which established an abbreviated regulatory scheme authorizing the FDA to approve generic drugs based on an innovator or “reference” product, Congress also enacted Section 505(b)(2) of the FDCA, which provides a hybrid pathway combining features of a traditional NDA and a generic drug application. To obtain approval of a generic drug, an applicant must submit an abbreviated new drug application, or ANDA, to the agency. ANDAs are “abbreviated” because they do not include preclinical and clinical data to demonstrate safety and effectiveness.

Instead, in support of such applications, a generic manufacturer may rely on the preclinical and clinical testing previously conducted for a drug product previously approved under an NDA, known as the reference-listed drug, or RLD.

Specifically, in order for an ANDA to be approved, the FDA must find that the generic version is identical to the RLD with respect to the active ingredients, the route of administration, the dosage form, and the strength of the drug. At the same time, the FDA must also determine that the generic drug is “bioequivalent” to the innovator drug. Under the statute, a generic drug is bioequivalent to an RLD if “the rate and extent of absorption of the drug do not show a significant difference from the rate and extent of absorption of the listed drug.”

Upon approval of an ANDA, the FDA indicates whether the generic product is “therapeutically equivalent” to the RLD in its publication Approved Drug Products with Therapeutic Equivalence Evaluations, also referred to as the Orange Book. Clinicians and pharmacists consider a therapeutic equivalent generic drug to be fully substitutable for the RLD. In addition, by operation of certain state laws and numerous health insurance programs, the FDA’s designation of therapeutic equivalence often results in substitution of the generic drug without the knowledge or consent of either the prescribing clinicians or patient.

In contrast, Section 505(b)(2) permits the filing of an NDA where at least some of the information required for approval comes from studies not conducted by or for the applicant and for which the applicant has not obtained a right of reference. A Section 505(b)(2) applicant may eliminate the need to conduct certain preclinical or clinical studies, if it can establish that reliance on studies conducted for a previously approved product is scientifically appropriate. Unlike the ANDA pathway used by developers of bioequivalent versions of innovator drugs, the 505(b)(2) regulatory pathway does not preclude the possibility that a follow-on applicant would need to conduct additional clinical trials or nonclinical studies; for example, they may be seeking approval to market a previously approved drug for new indications or for a new patient population that would require new clinical data to demonstrate safety or effectiveness.

In addition, under the Hatch-Waxman Act, the FDA might not approve an ANDA or 505(b)(2) NDA until any applicable period of non-patent exclusivity for the RLD has expired. These market exclusivity provisions under the FDCA also can delay the submission or the approval of certain applications. The FDCA provides a period of five years of non-patent data exclusivity for a new drug containing a new chemical entity. For the purposes of this provision, a new chemical entity, or NCE, is a drug that contains no active moiety that has previously been approved by the FDA in any other NDA. An active moiety is the molecule or ion responsible for the physiological or pharmacological action of the drug substance. In cases where such NCE exclusivity has been granted, an ANDA or 505(b)(2) NDA may not be filed with the FDA until the expiration of five years unless the submission is accompanied by a Paragraph IV certification (described below), in which case the applicant may submit its application four years following the original product approval.

The FDCA also provides for a period of three years of exclusivity for an NDA, 505(b)(2) NDA or supplement thereto if one or more new clinical investigations, other than bioavailability or bioequivalence studies, that were conducted by or for the applicant are deemed by the FDA to be essential to the approval of the application. This three-year exclusivity period often protects changes to a previously approved drug product, such as a new dosage form, route of administration, combination or indication. The three-year exclusivity covers only the conditions of use associated with the new clinical investigations and does not prohibit the FDA from approving follow-on applications for drugs containing the original active agent. Five-year and three-year exclusivity also will not delay the submission or approval of a traditional NDA filed under Section 505(b)(1) of the FDCA. However, an applicant submitting a traditional NDA would be required to either conduct or obtain a right of reference to all of the preclinical studies and

adequate and well-controlled clinical trials necessary to demonstrate safety and effectiveness.

48

Table of Contents

Hatch-Waxman patent certification and the 30-month stay

Upon approval of an NDA or a supplement thereto, NDA sponsors are required to list with the FDA each patent with claims that cover the applicant’s product or an approved method of using the product. Each of the patents listed by the NDA sponsor is published in the Orange Book. When an ANDA applicant files its application with the FDA, the applicant is required to certify to the FDA concerning any patents listed for the reference product in the Orange Book, except for patents covering methods of use for which the ANDA applicant is not seeking approval. To the extent that the Section 505(b)(2) NDA applicant is relying on studies conducted for an already approved product, the applicant is required to certify to the FDA concerning any patents listed for the approved product in the Orange Book to the same extent that an ANDA applicant would.

Specifically, the applicant must certify with respect to each patent that:

I.the required patent information has not been filed by the original applicant;

II.the listed patent has expired;

III.the listed patent has not expired, but will expire on a particular date and approval is sought after patent expiration; or

IV.the listed patent is invalid, unenforceable or will not be infringed by the manufacture, use or sale of the new product.

If a Paragraph I or II certification is filed, the FDA may make approval of the application effective immediately upon completion of its review. If a Paragraph III certification is filed, the approval may be made effective on the patent expiration date specified in the application, although a tentative approval may be issued before that time. If an application contains a Paragraph IV certification, a series of events will be triggered, the outcome of which will determine the effective date of approval of the ANDA or 505(b)(2) application.

If the follow-on applicant has provided a Paragraph IV certification to the FDA, the applicant must also send notice of the Paragraph IV certification to the NDA and patent holders once the follow-on application in question has been accepted for filing by the FDA. The NDA and patent holders may then initiate a patent infringement lawsuit in response to the notice of the Paragraph IV certification. The filing of a patent infringement lawsuit within 45 days after the receipt of a Paragraph IV certification automatically prevents the FDA from approving the ANDA or 505(b)(2) NDA until the earlier of 30 months after the receipt of the Paragraph IV notice, expiration of the patent, or a decision in the infringement case that is favorable to the ANDA or 505(b)(2) applicant. Alternatively, if the listed patent holder does not file a patent infringement lawsuit within the required 45-day period, the follow-on applicant’s ANDA or 505(b)(2) NDA will not be subject to the 30-month stay.

Reference a product exclusivity for biological products

The Biologics Price Competition and Innovation Act of 2009, or BPCIA, amended the PHSA to authorize the FDA to approve similar versions of innovative biologics such as ours, which are also known as “reference biological products.” The new pathway authorized under the BPCIA allows FDA to approve, under an abbreviated application, a biological product that are demonstrated to be “biosimilar” or “interchangeable” with an FDA-licensed reference biological product. Biosimilarity to an approved reference product requires that there be no differences in mechanism of action for the conditions of use, route of administration, dosage form, and strength, and no clinically meaningful differences between the follow-on biological product and the reference product in terms of safety, purity, and potency. Biosimilarity is demonstrated in steps beginning with rigorous analytical studies or “fingerprinting,” in vitro studies, in vivo animal studies, and for some biosimilar products, at least one clinical study, absent a waiver from the FDA. The biosimilarity exercise tests the hypothesis that the investigational product and the reference product are the same. If at any point in the stepwise biosimilarity process a significant difference is observed, then the products are not biosimilar, and the development of a standalone BLA for the follow-on biological product is necessary. In order to meet the higher hurdle of interchangeability, a sponsor must demonstrate that the biosimilar product can be expected to produce the same clinical result as the reference product, and for a product that is administered more than once, that the risk of switching between the reference product and biosimilar product is not greater than the risk of maintaining the patient on the reference product. Complexities associated with the larger,

49

Table of Contents

and often more complex, structures of biological products, as well as the process by which such products are manufactured, pose significant hurdles to implementation that are still being evaluated by the FDA.

Under the BPCIA, a reference biological product is granted 12 years of data exclusivity from the date of first licensure of the product, which means that the FDA is barred from approving biosimilar applications for 12 years after the reference biological product receives initial marketing approval. The first approved interchangeable biological product will be granted an exclusivity period of up to one year after it is first commercially marketed, and as part of the Consolidated Appropriations Act for 2023, Congress amended the PHSA in order to permit multiple interchangeable products approved on the same day to receive and benefit from this one-year exclusivity period. In addition, the FDA will not accept an application for a biosimilar or interchangeable product based on the reference biological product until four years after the date of first licensure of the reference product. “First licensure” typically means the initial date the particular product at issue was licensed in the United States. Date of first licensure does not include the date of licensure of (and a new period of exclusivity is not available for) a supplement for the reference product for a subsequent application filed by the same sponsor or manufacturer of the reference product (or licensor, predecessor in interest or other related entity) for a change (not including a modification to the structure of the biological product) that results in a new indication, route of administration, dosing schedule, dosage form, delivery system, delivery device or strength or for a modification to the structure of the biological product that does not result in a change in safety, purity or potency. Therefore, one must determine whether a new product includes a modification to the structure of a previously licensed product that results in a change in safety, purity or potency to assess whether the licensure of the new product is a first licensure that triggers its own period of exclusivity. Whether a subsequent application, if approved, warrants exclusivity as the “first licensure” of a biological product is determined on a case-by-case basis with data submitted by the sponsor.

The BPCIA is complex and continues to be interpreted and implemented by the FDA. In addition, some government proposals have sought to reduce the 12-year reference product exclusivity period. Other aspects of the BPCIA, some of which may impact the BPCIA exclusivity provisions, have also been the subject of recent litigation. As a result, the ultimate impact, implementation and meaning of the BPCIA continues to be subject to significant uncertainty.

Post-approval requirements

Following approval of a new product, the manufacturer and the approved product are subject to pervasive and continuing regulation by the FDA, including, among other things, monitoring and recordkeeping activities, reporting of adverse experiences with the product, product sampling and distribution restrictions, complying with promotion and advertising requirements, which include restrictions on promoting drugs for unapproved uses or patient populations (i.e., “off-label use”) and limitations on industry-sponsored scientific and educational activities. The manufacturer and its products are also subject to similar post-approval requirements by regulatory authorities comparable to FDA in jurisdictions outside of the United States where the products are approved. Although physicians may prescribe legally available products for off-label uses, manufacturers may not market or promote such uses. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses, and a company that is found to have improperly promoted off-label uses may be subject to significant liability. If there are any modifications to the product, including changes in indications, labeling or manufacturing processes or facilities, the applicant may be required to submit and obtain FDA approval of a new NDA or BLA or a supplement thereto, which may require the applicant to develop additional data or conduct additional preclinical studies and clinical trials. The FDA may also place other conditions on approvals including the requirement for a REMS to assure the safe use of the product. A REMS could include medication guides, physician communication plans or elements to assure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. Any of these limitations on approval or marketing could restrict the commercial promotion, distribution, prescription or dispensing of products. Product approvals may be withdrawn for non-compliance with regulatory standards or if problems occur following initial marketing.

FDA regulations require that products be manufactured in specific approved facilities and in accordance with cGMP. The cGMP regulations include requirements relating to organization of personnel, buildings and facilities, equipment, control of components and drug product containers and closures, production and process controls, packaging and labeling controls, holding and distribution, laboratory controls, records and reports and returned or salvaged products. The manufacturing facilities for our product candidates must meet applicable cGMP

50

Table of Contents

requirements to the FDA’s or comparable foreign regulatory authorities’ satisfaction before any product is approved and our commercial products can be manufactured. We rely, and expect to continue to rely, on third parties for the production of clinical and commercial quantities of our products in accordance with cGMP regulations. These manufacturers must comply with cGMP regulations that require, among other things, quality control and quality assurance, the maintenance of records and documentation and the obligation to investigate and correct any deviations from cGMP. Manufacturers and other entities involved in the manufacture and distribution of approved drugs or biologics are required to register their establishments with the FDA and certain state agencies and are subject to periodic prescheduled or unannounced inspections by the FDA and certain state agencies for compliance with cGMP and other laws. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain cGMP compliance. Future inspections by the FDA and other regulatory agencies may identify compliance issues at the facilities of our CMOs that may disrupt production or distribution or require substantial resources to correct. In addition, the discovery of conditions that violate these rules, including failure to conform to cGMP, could result in enforcement actions, and the discovery of problems with a product after approval may result in restrictions on a product, manufacturer or holder of an approved BLA, including voluntary recall and regulatory sanctions as described below.

Once an approval of a drug or biologic is granted, the FDA may withdraw the approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in mandatory revisions to the approved labeling to add new safety information; imposition of post-market or clinical trials to assess new safety risks; or imposition of distribution or other restrictions under a REMS program. Other potential consequences include, among other things:

•restrictions on the marketing or manufacturing of the product, complete withdrawal of the product from the market or product recalls;

•fines, warning letters or other enforcement-related letters or clinical holds on post-approval clinical trials;

•refusal of the FDA to approve pending NDAs or BLAs or supplements to approved marketing authorizations, or suspension or revocation of product approvals;

•product seizure or detention, or refusal to permit the import or export of products;

•injunctions or the imposition of civil or criminal penalties; and

•consent decrees, corporate integrity agreements, debarment, or exclusion from federal health care programs; or mandated modification of promotional materials and labeling and the issuance of corrective information.

In addition, the distribution of prescription pharmaceutical products is subject to the Prescription Drug Marketing Act, or PDMA, which regulates the distribution of drugs and drug samples at the federal level and sets minimum standards for the registration and regulation of drug distributors by the states. Both the PDMA and state laws limit the distribution of prescription pharmaceutical product samples and impose requirements to ensure accountability in distribution. Furthermore, the Drug Supply Chain Security Act, or DSCSA, was enacted with the aim of building an electronic system to identify and trace certain prescription drugs distributed in the United States, including most biological products. The DSCSA mandates resource-intensive obligations for pharmaceutical manufacturers, wholesale distributors, and dispensers. From time to time, new legislation and regulations may be implemented that could significantly change the statutory provisions governing the approval, manufacturing and marketing of products regulated by the FDA. It is impossible to predict whether further legislative or regulatory changes will be enacted, whether FDA regulations, guidance or interpretations will be changed or what the impact of such changes, if any, may be.

Other Health Care Laws and Compliance Requirements

51

Table of Contents

Our sales, promotion, medical education and other activities following product approval will be subject to regulation by numerous regulatory and law enforcement authorities in the United States in addition to FDA, including potentially the Federal Trade Commission, or FTC, the Department of Justice, or DOJ, the Centers for Medicare and Medicaid Services, or CMS, other divisions of the Department of Health and Human Services, or DHHS, and state and local governments. Our promotional and scientific/educational programs must comply with the federal Anti-Kickback Statute, the Foreign Corrupt Practices Act, the False Claims Act, or FCA, the Veterans Health Care Act, physician payment transparency laws, privacy laws, security laws, and additional state laws similar to the foregoing.

The federal Anti-Kickback Statute prohibits, among other things, persons from knowingly and willfully soliciting, offering, receiving, or paying remuneration, directly or indirectly, in cash or in kind, in exchange for or to induce or reward either the referral of patients for, or the purchase, order or recommendation of, any good or service that may be paid for in whole or part by Medicare, Medicaid or other federal health care programs. Remuneration has been broadly defined to include anything of value, including cash, improper discounts, and free or reduced-price items and services. The government has enforced the Anti-Kickback Statute to reach large settlements with health care companies based on sham research or consulting and other financial arrangements with physicians. Further, a person or entity does not need to have actual knowledge of the statute or specific intent to violate it to have committed a violation. In addition, the government may assert that a claim including items or services resulting from a violation of the federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the FCA. Many states have similar laws that apply to their state health care programs as well as private payors.

The FCA imposes liability on persons who, among other things, (i) knowingly present or cause to be presented false or fraudulent claims for payment or approval by a federal health care program, (ii) knowingly make, use, or cause to be made or used a false record or statement material to a false or fraudulent claim to the federal government, or (iii) avoid, decrease, or conceal an obligation to pay money to the federal government. The FCA has been used to prosecute persons submitting claims for payment that are inaccurate or fraudulent, that are for services not provided as claimed, or for services that are not medically necessary. Actions under the FCA may be brought by the U.S. Attorney General or as a qui tam action by a private individual in the name of the government. Violations of the FCA can result in significant monetary penalties and treble damages. The federal government is using the FCA, and the accompanying threat of significant liability, in its investigation and prosecution of pharmaceutical and biotechnology companies throughout the country, for example, in connection with the promotion of products for unapproved uses and other sales and marketing practices. The government has obtained multi-million and multi-billion dollar settlements under the FCA in addition to individual criminal convictions under applicable criminal statutes. Conviction or civil judgment for violating the FCA may result in exclusion from federal health care programs, and suspension and debarment from government contracts, and refusal of orders under existing government contracts. In addition, companies have been forced to implement extensive corrective action plans and have often become subject to consent decrees or corporate integrity agreements, restricting the manner in which they conduct their business. The federal Health Insurance Portability and Accountability Act of 1996, or HIPAA, also created federal criminal statutes that prohibit, among other things, knowingly and willfully executing a scheme to defraud any health care benefit program, including private third-party payors and knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false, fictitious or fraudulent statement in connection with the delivery of or payment for health care benefits, items or services. Given the significant size of actual and potential settlements, it is expected that the government will continue to devote substantial resources to investigating health care providers’ and manufacturers’ compliance with applicable fraud and abuse laws.

In addition, there has been a recent trend of increased federal and state regulation of payments made to physicians and other health care providers. The federal Physician Payments Sunshine Act, enacted as part of the Patient Protection and Affordable Care Act of 2010, or the ACA, requires manufacturers of FDA-approved drugs, devices, biologics and medical supplies covered by Medicare, Medicaid or the Children’s Health Insurance Program to report, on an annual basis, to CMS information related to payments or other transfers of value made by them to U.S.-licensed physicians (defined to include doctors, dentists, optometrists, podiatrists and chiropractors), certain advanced non-physician health care practitioners and teaching hospitals, as well as ownership and investment interests held by physicians and their immediate family members. Failure to submit required information may result in civil monetary penalties. Certain states also mandate implementation of commercial compliance programs, impose restrictions on drug manufacturer marketing practices and/or require the tracking and reporting of gifts, compensation and other remuneration to physicians and other health care professionals.

52

Table of Contents

The federal criminal statutes enacted under HIPAA impose criminal liability for knowingly and willfully executing, or attempting to execute, a scheme to defraud any health care benefit program, including private third-party payors, or obtain, by means of false or fraudulent pretenses, representations, or promises, any of the money or property owned by, or under the custody or control of, any health care benefit program; knowingly and willfully embezzling or stealing from a health care benefit program; willfully preventing, obstructing, misleading, or delaying a criminal investigation of a health care offense; and knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false statements in connection with the delivery of or payment for health care benefits, items or services. Similar to the federal Anti-Kickback Statute, a person or entity need not have actual knowledge of the statute or specific intent to violate it in order to have committed a violation.

We may also be subject to data privacy and security regulation by both the federal government and the states in which it conducts its business. HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act, or HITECH, and their respective implementing regulations impose specific requirements on covered entities relating to the privacy, security and transmission of individually identifiable health information, known as protected health information. Among other things, HITECH makes HIPAA’s privacy and security standards directly applicable to “business associates,” defined as independent contractors or agents of covered entities that create, receive, maintain or transmit protected health information in connection with providing a service for or on behalf of a covered entity for a function or activity regulated by HIPAA. HITECH also increased the civil and criminal penalties that may be imposed against covered entities, business associates and possibly other persons, and gave state attorneys general new authority to file civil actions for damages or injunctions in federal courts to enforce the federal HIPAA laws and seek attorney’s fees and costs associated with pursuing federal civil actions. We are not a covered entity or a business associate under HIPAA; however, we are indirectly affected by HIPAA because the protected health information held by investigators conducting our clinical trials is subject to HIPAA and can only be used for our clinical research consistent with HIPAA requirements imposed on those investigators. In addition, state laws, such as the California Consumer Privacy Act, or the CCPA, govern the privacy and security of the personal information of individuals residing in such states, and may in certain circumstances, apply to health information. In addition to California, other states have implemented laws protecting identifiable health and personal information, and many of these laws differ from each other in significant ways and may not be preempted by HIPAA, thus complicating compliance efforts.

We may also be subject to analogous state and foreign laws and regulations, such as state anti-kickback and false claims laws, which may apply to sales or marketing arrangements and claims involving health care items or services reimbursed by non-governmental third-party payors, including private insurers, and may be broader in scope than their federal equivalents. The laws of some U.S. states and foreign jurisdictions require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government or otherwise restrict payments that may be made to health care providers. In addition, certain state and foreign laws and regulations require disclosures to regulatory agencies and/or commercial purchasers with respect to certain price increases that exceed a certain level as identified in the relevant statutes, require drug manufacturers to report information related to payments and other transfers of value to physicians and other health care providers, and restrict marketing practices or require disclosure of marketing expenditures and pricing information. Some U.S. states also require registration of pharmaceutical sales representatives.

If our operations are found to be in violation of any of such laws or any other governmental regulations that apply to it, we may be subject to penalties, including, without limitation, civil and criminal penalties, damages, fines, the curtailment or restructuring of our operations, exclusion from participation in federal and state health care programs and imprisonment, any of which could adversely affect our ability to operate our business and our financial results. Also, the U.S. Foreign Corrupt Practices Act and similar worldwide anti-bribery laws generally prohibit companies and their intermediaries from making improper payments to foreign officials for the purpose of obtaining or retaining business. We cannot assure you that our internal control policies and procedures will protect us from reckless or negligent acts committed by our employees, future distributors, partners, collaborators or agents. Violations of these laws, or allegations of such violations, could result in fines, penalties or prosecution and have a negative impact on our business, results of operations and reputation.

General Data Protection Regulation

53

Table of Contents

The collection, use, disclosure, transfer, or other processing of personal data regarding individuals in the EU, including personal health data, is subject to the EU’s General Data Protection Regulation, or GDPR, which became effective on May 25, 2018. The GDPR is wide-ranging in scope and imposes numerous requirements on companies that process personal data, including requirements relating to processing health and other sensitive data, obtaining consent of the individuals to whom the personal data relates, providing information to individuals regarding data processing activities, implementing safeguards to protect the security and confidentiality of personal data, providing notification of data breaches, and taking certain measures when engaging third-party processors. The GDPR also imposes strict rules on the transfer of personal data to countries outside the EU, including the U.S., and permits data protection authorities to impose large penalties for violations of the GDPR, including potential fines of up to €20 million or 4% of annual global turnover, whichever is greater. The GDPR also confers a private right of action on data subjects and consumer associations to lodge complaints with supervisory authorities, seek judicial remedies, and obtain compensation for damages resulting from violations of the GDPR. The Company must comply with the GDPR in the performance of its clinical trials in the EU and relies on its CROs to implement appropriate safeguards and procedures relating to informed consent in order to ensure that trials are conducted in a manner consistent with the GDPR.

In July 2023, the European Commission adopted an adequacy decision for a new mechanism for transferring personal data from the EU to the United States – the EU-U.S. Data Privacy Framework, which provides EU individuals with several new rights, including the right to obtain access to their data, or obtain correction or deletion of incorrect or unlawfully handled data. In addition, the EU-U.S. Data Privacy Framework offers additional redress avenues for violations, including free of charge independent dispute resolution mechanisms and an arbitration panel. The adequacy decision followed the U.S.' signing of an executive order introducing new binding safeguards to address the points raised by the Court of Justice of the EU in its decision on a case known as Schrems II, which invalidated the previous EU-U.S. Privacy Shield. Notably, the new obligations were geared to ensure that data can be accessed by U.S. intelligence agencies only to the extent necessary and proportionate and to establish an independent and impartial redress mechanism to handle complaints from Europeans concerning the collection of their data for national security purposes. The European Commission will continually review developments in the United States along with its adequacy decision. Adequacy decisions can be adapted or even withdrawn in the event of developments affecting the level of protection in the applicable jurisdiction. Future actions of EU data protection authorities are difficult to predict. Some customers or other service providers may respond to these evolving laws and regulations by asking us to make certain privacy or data-related contractual commitments that we are unable or unwilling to make. This could lead to the loss of current or prospective customers or other business relationships.

Coverage and Reimbursement

Sales of our products approved for marketing by the FDA and foreign regulatory authorities will depend, in part, on the extent to which our products will be covered by third-party payors, such as government health programs, commercial or private insurance and managed care organizations. The process for determining whether a payor will provide coverage for a drug or biological product may be separate from the process for setting the price or reimbursement rate that the payor will pay for the drug or biological product. Third-party payors may limit coverage to specific drug or biological products on an approved list, or formulary, which might not include all of the FDA-approved drug or biological products for a particular indication. Third-party payors are increasingly challenging drug prices and examining the medical necessity and cost-effectiveness of medical products and services, in addition to their safety and efficacy.

In order to secure coverage and reimbursement for any product that might be approved for sale, a company may need to conduct expensive pharmacoeconomic studies in order to demonstrate the medical necessity and cost-effectiveness of the product, in addition to the costs required to obtain FDA or other comparable regulatory approvals. Our drug or biological candidates may or may not be considered medically necessary or cost-effective or may require prior authorizations before use. A payor’s decision to provide coverage for a product does not imply that an adequate reimbursement rate will be approved. Moreover, eligibility for reimbursement may not be available at a rate that covers our costs, including research, development, manufacture, sale and distribution. Interim payments for new products, if applicable, may also not be sufficient to cover our costs and may not be made permanent. Reimbursement rates may vary according to the use of the product and the clinical setting in which it is used, may be based on reimbursement levels already set for lower cost products and may be incorporated into existing payments for other services. Net prices for products may be reduced by mandatory discounts or rebates

54

Table of Contents

required by third-party payors and by any future relaxation of laws that presently restrict imports of products from countries where they may be sold at lower prices than in the United States. In the United States, third-party payors often rely upon CMS coverage policy and payment limitations in setting their own reimbursement policies, but they also have their own methods and approval processes apart from CMS coverage and reimbursement determinations. Accordingly, one third-party payor’s determination to provide coverage for a product does not assure that other payors will also provide coverage for the product.

The coverage determination process is often a time-consuming and costly process that will require us to provide scientific and clinical support for the use of our products to each payor separately, with no assurance that coverage and adequate reimbursement will be applied consistently or granted at all. The process for determining whether a payor will cover and provide reimbursement for a product may be separate from the process of seeking approval for or setting the price of the product. Even if reimbursement is provided, market acceptance of our products may be adversely affected if the amount of payment for our products proves to be unprofitable for health care providers or less profitable than alternative treatments or if administrative burdens make our products less desirable to use.

Additionally, the United States government, state legislatures and foreign governments have shown significant interest in implementing cost containment programs to limit the growth of government-paid health care costs, including price controls, restrictions on reimbursement and requirements for substitution of generic products for branded prescription drugs. For example, the ACA contains provisions that may reduce the profitability of drug products through increased rebates for drugs reimbursed by Medicaid programs, extension of Medicaid rebates to Medicaid managed care plans, mandatory discounts for certain Medicare Part D beneficiaries and annual fees based on biopharmaceutical companies’ share of sales to federal health care programs. Adoption of general controls and measures, coupled with the tightening of restrictive policies in jurisdictions with existing controls and measures, could limit payments for drugs and biologics. The Medicaid Drug Rebate Program requires biopharmaceutical manufacturers to enter into and have in effect a national rebate agreement with the Secretary of the DHHS as a condition for states to receive federal matching funds for the manufacturer’s outpatient therapeutic products furnished to Medicaid patients. The ACA made several changes to the Medicaid Drug Rebate Program, including increasing biopharmaceutical manufacturers’ rebate liability by raising the minimum basic Medicaid rebate on most branded prescription drugs from 15.1% of average manufacturer price, or AMP, to 23.1% of AMP and adding a new rebate calculation for “line extensions” (i.e., new formulations, such as extended release formulations) of solid oral dosage forms of branded products, as well as potentially impacting their rebate liability by modifying the statutory definition of AMP. The ACA also expanded the universe of Medicaid utilization subject to drug rebates by requiring biopharmaceutical manufacturers to pay rebates on Medicaid managed care utilization and by enlarging the population potentially eligible for Medicaid drug benefits. As another example, the 2021 Consolidated Appropriations Act, signed into law on December 27, 2020, incorporated extensive health care provisions and amendments to existing laws, including a requirement that all manufacturers of drugs and biological products covered under Medicare Part B report the product’s average sales price, or ASP, to the DHHS beginning on January 1, 2022, subject to enforcement via civil money penalties.

Under currently applicable U.S. law, certain products that are not self-administered by the patient (including injectable drugs) may be eligible for coverage under Medicare through Medicare Part B. Medicare Part B is administered by Medicare Administrative Contractors, which generally have the responsibility of making coverage decisions. Subject to certain payment adjustments and limits, Medicare generally pays for a Part B-covered drug or biologic based on a percentage of manufacturer-reported Average Sales Price, which is regularly updated. For a drug or biological product to receive federal reimbursement under the Medicaid or Medicare Part B programs or to be sold directly to U.S. government agencies, the manufacturer must extend discounts to entities eligible to participate in the 340B Drug Pricing Program. The maximum amount that a manufacturer may charge a 340B covered entity for a given product is the AMP reduced by the rebate amount paid by the manufacturer to Medicaid for each unit of that product. As 340B drug pricing is determined based on AMP and Medicaid rebate data, the revisions to the Medicaid rebate formula and AMP definition described above could cause the required 340B discount to increase.

There has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement

55

Table of Contents

methodologies for drug products. For example, the 2021 Consolidated Appropriations Act signed into law on December 27, 2020 incorporated extensive health care provisions and amendments to existing laws, including new requirements for (1) all manufacturers of drugs and biological products covered under Medicare Part B to report the product’s ASP, to the DHHS beginning on January 1, 2022, subject to enforcement via civil money penalties, (2) certain Medicare plans to develop tools to display Medicare Part D prescription drug benefit information in real time, and (3) for group and health insurance issuers to report information on pharmacy benefit and drug costs to the Secretaries of the DHHS, the Department of Labor and the Department of the Treasury.

More recently, in August 2022 the Inflation Reduction Act of 2022, or the IRA, was signed into law. Among other things, the IRA has multiple provisions that may impact the prices of drug products that are both sold into the Medicare program and throughout the United States. For example, a manufacturer of a drug or biological product covered by Medicare Parts B or D must pay a rebate to the federal government if the drug product’s price increases faster than the rate of inflation. This calculation is made on a product-by-product basis and the amount of the rebate owed to the federal government is directly dependent on the volume of a drug product that is paid for by Medicare Parts B or D. Additionally, CMS will negotiate drug prices annually for a select number of single-source Part D drugs without generic or biosimilar competition. CMS will also negotiate drug prices for a select number of Part B drugs starting for payment year 2028. If a drug product is selected by CMS for negotiation, it is expected that the revenue generated from such drug will decrease. CMS has begun to implement these new authorities, announcing the first round of negotiated prices for the first 10 drug products in August 2024, which will become applicable for payment year 2026. The second round of negotiated prices for 15 drug products was announced in November 2025. However, the IRA’s impact on the pharmaceutical industry in the United States remains uncertain, in part because multiple large pharmaceutical companies and other stakeholders (e.g., the U.S. Chamber of Commerce) have initiated federal lawsuits against CMS arguing the program is unconstitutional for a variety of reasons, among other complaints. Those lawsuits are currently ongoing.

Separately, the Trump Administration announced the creation of a government website called TrumpRx, which will allow consumers to purchase certain drugs at reduced prices as negotiated between the drug manufacturers and the administration. As of December 2025, the Trump Administration secured deals with five major drug manufacturers to offer certain drugs at most-favored-nation prices.

At the state level, legislatures have increasingly passed legislation and implemented regulations designed to control drug and biological product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing. For example, in recent years, several states have formed prescription drug affordability boards, or PDABs. Much like the IRA’s drug price negotiation program, these PDABs have attempted to implement upper payment limits, or UPLs, on drugs sold in their respective states in both public and commercial health plans. For example, in August 2023, Colorado’s PDAB announced a list of five prescription drugs that would undergo an affordability review. The effects of these efforts remain uncertain pending the outcomes of several federal lawsuits challenging state authority to regulate prescription drug payment limits. We expect that federal, state and local governments in the United States will continue to consider legislation directed at lowering the total cost of health care.

In December 2020, the U.S. Supreme Court held unanimously that federal law does not preempt the states’ ability to regulate pharmacy benefit managers, or PBMs, and other members of the health care and pharmaceutical supply chain, an important decision that may lead to further and more aggressive efforts by states in this area. The FTC in mid-2022 also launched sweeping investigations in the practices of the PBM industry that could lead to additional federal and state legislative or regulatory proposals targeting such entities’ operations, pharmacy networks, or financial arrangements. Significant efforts to change the PBM industry as it currently exists in the United States may affect the entire pharmaceutical supply chain and the business of other stakeholders, including biopharmaceutical developers like us.

As noted above, the marketability of any products for which we receive regulatory approval for commercial sale may suffer if the government and third-party payors fail to provide adequate coverage and reimbursement. An increasing emphasis on cost containment measures in the United States has increased and we expect will continue to increase the pressure on drug or biological product pricing. Coverage policies and third-party reimbursement rates may change at any time. Even if favorable coverage and reimbursement status is attained for one or more products

56

Table of Contents

for which we receive regulatory approval, less favorable coverage policies and reimbursement rates may be implemented in the future.

In some foreign countries, proposed pricing for drug and biological products must be approved before the product may be lawfully marketed. The requirements governing drug pricing vary widely from country to country. Some countries provide that drug and biological products may be marketed only after agreement on a reimbursement price has been reached. Some countries may require additional studies that compare the cost-effectiveness of our product candidate to currently available therapies (so called health technology assessment, or HTA) in order to obtain reimbursement or pricing approval. For example, the EU provides options for its member states to restrict the range of medicinal products for which their national health insurance systems provide reimbursement and to control the prices of medicines. A member state may approve a specific price for the product or it may instead adopt a system of direct or indirect controls on the profitability of the company placing the product on the market. Other member states allow companies to fix their own drug prices but monitor and control prescription volumes and issue guidance to physicians to limit prescriptions. There can be no assurance that any country that has price controls or reimbursement limitations for drug and biological products will allow favorable reimbursement and pricing arrangements for any of our products. Historically, products launched in the EU do not follow price structures of the United States and generally tend to be priced significantly lower.

Foreign Regulation

In addition to regulations in the United States, we are and will be subject, either directly or through our distribution partners, to a variety of regulations in other jurisdictions governing, among other things, clinical trials and commercial sales and distribution of our products, if approved in such jurisdiction.

Whether or not we obtain FDA approval for a product, we must obtain the requisite approvals from regulatory authorities in non-U.S. countries prior to the commencement of clinical trials or marketing of the product in those countries. The time required to obtain approval in other countries and jurisdictions might differ from and be longer than that required to obtain FDA approval. Regulatory approval in one country or jurisdiction does not ensure regulatory approval in another, but a failure or delay in obtaining regulatory approval in one country or jurisdiction may negatively impact the regulatory process in others.

Similar to the United States, the various phases of non-clinical and clinical research that takes place in other countries are subject to significant regulatory controls. For example, the EU’s Clinical Trials Regulation, which took effect in January 2022, was enacted to simplify and streamline the approval of clinical trials in the region. The main characteristics of the regulation include: a streamlined application procedure via a single entry point, the “EU portal” or Clinical Trial Information System; a single set of documents to be prepared and submitted for the application as well as simplified reporting procedures for clinical trial sponsors; and a harmonized procedure for the assessment of applications for clinical trials, which is divided in two parts. Part I, which contains scientific and medicinal product documentation, is assessed by the competent authorities of all EU member states in which an application for authorization of a clinical trial has been submitted. Part II, which contains the national and patient-level documentation, will be assessed individually by each such EU member state. Any substantial changes to the trial protocol or other information submitted with the CTA must be notified to or approved by the relevant competent authorities and ethics committees. Medicines used in clinical trials must be manufactured in accordance with applicable cGMP requirements. Other national and EU-wide regulatory requirements may also apply.

The requirements and processes governing the conduct of clinical trials, product licensing, pricing and reimbursement in Europe vary from country to country, even though there is already some degree of legal harmonization in the EU member states resulting from the national implementation of underlying EU legislation. In all cases, the clinical trials must be conducted in accordance with GCP and other applicable regulatory requirements. To obtain regulatory approval of a new drug or medicinal product in the EU, a sponsor must obtain approval of a marketing authorization application. The way in which a medicinal product can be approved in the EU depends on the nature of the medicinal product.

The centralized procedure results in a single marketing authorization granted by the European Commission that is valid across the EU, as well as in Iceland, Liechtenstein and Norway, or the European Economic Area, or EEA. The centralized procedure is compulsory for human medicines that are: (i) derived from biotechnology processes, such

57

Table of Contents

as genetic engineering, (ii) contain a new active substance indicated for the treatment of certain diseases, such as HIV/AIDS, cancer, diabetes, neurodegenerative diseases, autoimmune and other immune dysfunctions and viral diseases, (iii) officially designated as orphan medicinal product and (iv) advanced-therapy medicines, such as gene-therapy, somatic cell-therapy or tissue-engineered medicines. The centralized procedure may at the request of the applicant also be used for human medicines which do not fall within the above mentioned categories if the medicinal product contains a new active substance which has not been previously authorized in the EEA, the product constitutes a significant therapeutic, scientific or technical innovation, or where the granting of authorization in the centralized procedure is in the interests of public health in the EEA.

Under the centralized procedure in the EU, the maximum timeframe for the evaluation of a marketing authorization application by the EMA is 210 days (excluding clock stops, when additional written or oral information is to be provided by the applicant in response to questions asked by the Committee for Medicinal Products for Human Use, or CHMP, with adoption of the actual marketing authorization by the European Commission thereafter. Accelerated evaluation might be granted by the CHMP in exceptional cases, when a medicinal product is expected to be of a major public health interest from the point of view of therapeutic innovation, defined by three cumulative criteria: the seriousness of the disease to be treated; the absence of an appropriate alternative therapeutic approach, and anticipation of exceptional high therapeutic benefit. In this circumstance, EMA ensures that the evaluation for the opinion of the CHMP is completed within 150 days, excluding clock stops, and the opinion issued thereafter.

There are also two other possible routes to authorize medicinal products in several EU countries, which are available for investigational medicinal products for which the centralized procedure is not obligatory: the decentralized procedure and the mutual recognition procedure, or MRP. Using the decentralized procedure, an applicant may apply for simultaneous authorization in more than one EU country of a medicinal product that has not yet been authorized in any EU country and that does not fall within the mandatory scope of the centralized procedure.

The MRP is applicable to the majority of conventional medicinal products and is based on the principle of recognition of an already existing national marketing authorization by one or more member states. In the MRP process, a marketing authorization for a drug already exists in one or more member states of the EU and subsequently marketing authorization applications are made in other EU member states by referring to the initial marketing authorization. The member state in which the marketing authorization was first granted will then act as the reference member state. The member states where the marketing authorization is subsequently applied for act as concerned member states. After the reference state completes its medicinal product assessment, copies of the report are sent to all member states, together with the approved summary of product characteristics, labeling and package leaflet. The concerned member states then have 90 days to recognize the decision of the reference member state and the summary of product characteristics, labeling and package leaflet. National marketing authorizations shall be granted within 30 days after acknowledgement of the agreement.

Should any EU member state refuse to recognize the marketing authorization by the reference member state, on the grounds of potential serious risk to public health, the issue will be referred to a coordination group. Within a timeframe of 60 days, member states shall, within the coordination group, make all efforts to reach a consensus. If this fails, the procedure is submitted to an EMA scientific committee for arbitration. The opinion of this EMA Committee is then forwarded to the European Commission, for the start of the decision-making process. As in the centralized procedure, this process entails consulting various European Commission Directorates General and the EU member states Standing Committee on Human Medicinal Products.

Only products for which marketing authorizations have been granted may be sold in the EU. A marketing authorization is valid for five years in principle and the marketing authorization may be renewed after the initial five-year period on the basis of a re-evaluation of the risk-benefit balance by the EMA or by the competent authority of the authorizing member state. To this end, the marketing authorization holder must provide the EMA, or the applicable competent authority, with a consolidated version of the file in respect of quality, safety and efficacy, including all variations introduced since the marketing authorization was granted, at least six months before the marketing authorization ceases to be valid. Once renewed, the marketing authorization is valid for an unlimited period, unless the European Commission, or the applicable competent authority, decides, on justified grounds relating to pharmacovigilance, to proceed with one additional five-year renewal. Any marketing authorization which is not followed by the actual placing of the drug on the market in the EU (in case of centralized procedure) or on the

58

Table of Contents

market in the authorizing member state within three years after authorization ceases to be valid (the so-called sunset clause).

In the EU, new chemical entities, sometimes referred to as new active substances, qualify for eight years of data exclusivity upon marketing authorization and an additional two years of market exclusivity. The data exclusivity, if granted, prevents regulatory authorities in the EU from referencing the innovator’s data to assess a generic or biosimilar application for eight years, after which generic marketing authorization can be submitted, and the innovator’s data may be referenced, but not approved for two years. The overall ten-year period can be extended to a maximum of 11 years if, during the first eight years of those ten years, the marketing authorization holder obtains an authorization for one or more new therapeutic indications which, during the scientific evaluation prior to their authorization, are determined to bring a significant clinical benefit in comparison with currently approved therapies.

The criteria for designating an orphan medicinal product in the EU are similar in principle to those in the United States. Under Article 3 of Regulation (EC) 141/2000, a medicinal product may be designated as orphan if (1) it is intended for the diagnosis, prevention or treatment of a life-threatening or chronically debilitating condition; (2) either (a) such condition affects no more than five in 10,000 persons in the EU when the application is made, or (b) the product, without the benefits derived from orphan status, would not generate sufficient return in the EU to justify investment; and (3) there exists no satisfactory method of diagnosis, prevention or treatment of such condition authorized for marketing in the EU, or if such a method exists, the product will be of significant benefit to those affected by the condition, as defined in Regulation (EC) 847/2000. Orphan medicinal products are eligible for financial incentives such as reduction of fees or fee waivers and are, upon grant of a marketing authorization, entitled to ten years of market exclusivity for the approved therapeutic indication. The application for orphan designation must be submitted before the application for marketing authorization. The applicant will receive a fee reduction for the marketing authorization application if the orphan designation has been granted, but not if the designation is still pending at the time the marketing authorization is submitted. Orphan designation does not convey any advantage in, or shorten the duration of, the regulatory review and approval process.

The 10-year market exclusivity for orphan products in the EU may be reduced to six years if, at the end of the fifth year, it is established that the product no longer meets the criteria for orphan designation, for example, if the product is sufficiently profitable not to justify maintenance of market exclusivity. Additionally, marketing authorization may be granted to a similar product for the same indication at any time if:

•the second applicant can establish that its product, although similar, is safer, more effective or otherwise clinically superior;

•the applicant consents to a second orphan medicinal product application; or

•the applicant cannot supply enough orphan medicinal product.

We have obtained Orphan Medicinal Product Designations from the EMA for GPS in AML, MPM and MM.

In April 2023, the European Commission issued a proposal to revise and replace the existing general pharmaceutical legislation. As of January 2026, the three EU institutions, the European Commission, the European Parliament and the Council of the EU are in the process of negotiating the final content of the new Directive and Regulation. Once negotiations are complete, the European Parliament and the Council of the EU will vote on whether to approve the Directive and Regulation. If adopted and implemented as currently proposed, these revisions will significantly change several aspects of drug development and approval in the EU.

For other countries outside of the United States and the EU, such as countries in Eastern Europe, Latin America or Asia, the requirements governing the conduct of clinical trials, product licensing, pricing and reimbursement vary from country to country. In all cases, again, the clinical trials are conducted in accordance with GCP and the other applicable regulatory requirements.

If we fail to comply with applicable foreign regulatory requirements, we may be subject to, among other things, fines, suspension of clinical trials, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

Health Care Reform in the U.S. and Potential Changes to Health Care Laws

59

Table of Contents

In the United States and some foreign jurisdictions, there have been, and continue to be, several legislative and regulatory changes and proposed changes regarding the health care system that could prevent or delay marketing approval of product and therapeutic candidates, restrict or regulate post-approval activities, and affect the ability to profitably sell product and therapeutic candidates that obtain marketing approval. The FDA’s and other regulatory authorities’ policies may change and additional government regulations may be enacted that could prevent, limit or delay regulatory approval of our product and therapeutic candidates. In addition, future legislative and regulatory proposals may materially impact the ability of the FDA and other regulatory agencies to operate as they have historically operated. We cannot be sure whether additional legislative changes will be enacted, or whether any of the FDA’s regulations, guidances or interpretations will be changed, or what the impact of such changes on the agency and its scientific review staff, if any, may be. For example, negotiations on the next FDA user fee reauthorization package began in mid-2025, and the resulting agreement is expected to be sent to Congress in early 2027 for purposes of initiating the legislative process. Reauthorization of the prescription drug user fee program must be finalized by Congress by the end of September 2027 in order to avoid a disruption in FDA’s review goals for NDAs and other activities supported by user fees assessed against industry.

As previously mentioned, the primary trend in the US health care industry and elsewhere is cost containment. Government authorities and other third-party payors have attempted to control costs by limiting coverage and the amount of reimbursement for particular medical products and services, implementing reductions in Medicare and other health care funding and applying new payment methodologies. In addition to the sweeping reforms contained in the ACA (summarized above in the section entitled “Coverage and Reimbursement”), other legislative changes have been proposed and adopted in the United States that may affect health care expenditures. For example, the 2020 Further Consolidated Appropriations Act (P.L. 116-94) included a piece of bipartisan legislation called the Creating and Restoring Equal Access to Equivalent Samples Act of 2019, or the CREATES Act. The CREATES Act was enacted to address the concern articulated by both the FDA and industry stakeholders that some brand manufacturers improperly restrict the distribution of their products, including by invoking the existence of a REMS for certain products, to deny generic and biosimilar product developers access to samples of the brand products. Because generic and biosimilar product developers need samples to conduct certain comparative testing required by the FDA, some attributed the inability to timely obtain samples as a cause of delay in the entry of generic and biosimilar products. To remedy this concern, the CREATES Act established a private cause of action that permits a generic or biosimilar product developer to sue the brand manufacturer to compel it to furnish the necessary samples on “commercially reasonable, market-based terms.” Although lawsuits have been filed under the CREATES Act since its enactment, those lawsuits have settled privately; therefore, to date no federal court has reviewed or opined on the statutory language and there continues to be uncertainty regarding the scope and application of the law. The Consolidated Appropriations Act of 2021 also includes, among other things, a new requirement for patent information to be submitted to the FDA and published in a “Purple Book” that contains detailed information about each FDA-licensed biological product, analogous to the Orange Book that provides information about approved small-molecule drug products and their patent and exclusivity information under the Hatch-Waxman Act.

In the EU, many member states have increased the amount of discounts required on pharmaceuticals and these efforts could continue as countries attempt to manage health care expenditures, especially in light of the severe fiscal and debt crises experienced by many countries in the EU. The downward pressure on health care costs in general, particularly prescription products, has become intense. As a result, increasingly high barriers are being erected to the entry of new medicinal products. Political, economic and regulatory developments may further complicate pricing negotiations, and pricing negotiations may continue after reimbursement has been obtained. Reference pricing used by various EU member states, and parallel trade, i.e., arbitrage between low-priced and high-priced member states, can further reduce prices. There can be no assurance that any country that has price controls or reimbursement limitations for medicinal products will allow favorable reimbursement and pricing arrangements for any products, if approved in those countries.

We cannot predict the likelihood, nature or extent of government regulation that may arise from future legislation or administrative or executive action, either in the United States or abroad. We expect that additional state and federal health care reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for health care products and services. Moreover, if we are slow or unable to adapt to changes in existing requirements or the adoption of new requirements or policies, or if we are not able to maintain regulatory compliance, our therapeutic candidates may lose any marketing approval that may have been obtained and we may not achieve or sustain profitability, which would adversely affect our business, prospects, financial condition and results of operations.

60

Table of Contents

Corporate Information

Our principal executive offices are located at 7 Times Square, Suite 2503, New York, NY 10036, and our phone number is (646) 200-5278. Our website address is www.sellaslifesciences.com. We do not incorporate the information on our website into this Annual Report on Form 10-K, and you should not consider such information part of this Annual Report on Form 10-K.

We were incorporated on April 3, 2006 in Delaware as Argonaut Pharmaceuticals, Inc. On November 28, 2006, we changed our name to RXi Pharmaceuticals Corporation and began operations January 2007. On September 26, 2011, we changed our name to Galena Biopharma, Inc., or Galena. In December 2017, we completed a business combination, or the Merger, with SELLAS Life Sciences Group, Ltd., a privately held Bermuda exempted company, or Private SELLAS, and changed our name to “SELLAS Life Sciences Group, Inc.”

A copy of our Corporate Governance Guidelines, Code of Business Conduct and Ethics and the charters of the Audit Committee, Compensation Committee and Nominating and Corporate Governance Committee are posted on our website, www.sellaslifesciences.com, under “Investors – Corporate Governance.”