NASDAQ: STRO

The Phase 1 open-label, multicenter trial of STRO-004 is designed to evaluate the safety, pharmacokinetics, and preliminary anti-tumor activity of STRO-004 in patients with advanced TF-expressing solid tumors, including non-small cell lung cancer, head and neck squamous cell carcinoma, cervical cancer, colorectal cancer, pancreatic ductal adenocarcinoma, endometrial cancer, and bladder cancer. The dose-escalation phase includes multiple cohorts with ascending dose levels, supported by strong tolerability in non-human primates at up to 50 mg/kg. We finished dosing of patients in dose level 2 in February 2026 and began dosing patients in the dose level 3 cohort in February of 2026. We expect to report initial data from this trial in mid-2026.

Our preclinical assets include STRO-227 and STRO-006. STRO-006 is an ADC targeting integrin alpha v beta 6, or ITGß6. We believe STRO-006 has the potential to be a best-in-class ADC targeting ITGß6 based on preclinical studies that have demonstrated potent antitumor activity and the potential for a differentiated safety profile. IND enabling activities are underway for STRO-006 that could potentially support an IND filing in connection with this program in 2026.

STRO-227 is our first wholly-owned dual-payload ADC, a dual-payload ADC targeting Protein Tyrosine Kinase 7, or PTK7. This approach incorporates two distinct cytotoxic payloads, one that is designed to inhibit tubulin and another that is designed to inhibit topoisomerase. We have initiated certain chemistry, manufacturing and controls, or CMC, related activities for the PTK7-targeting dual-payload ADC and anticipate filing an IND in connection with this program in late 2026 or early 2027.

Enabled through our proprietary XpressCF® and XpressCF+® platforms, we have entered into multitarget, product-focused collaborations with leading pharmaceutical and biotechnology companies in the field of oncology, including an immunostimulatory ADCs collaboration with Astellas Pharma Inc., or Astellas; a cytokine derivatives collaboration with Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, or Merck; a B Cell Maturation Antigen, or BCMA, ADC collaboration with Celgene Corporation, or Celgene, a wholly owned subsidiary of Bristol Myers Squibb Company, New York, NY, or BMS; a MUC1-EGFR ADC collaboration with Merck KGaA, Darmstadt Germany (operating in the United States and Canada under the name “EMD Serono”), or EMD Serono, and we may enter into additional such collaborations in the future. In addition to potential research and development collaborations, we may partner or out-license one or more of our wholly-owned preclinical or clinical development programs depending on resource and capital availability.

Our XpressCF® and XpressCF+® platforms have also supported Vaxcyte, Inc., or Vaxcyte, focused on discovery and development of vaccines for the treatment and prophylaxis of infectious disease. We believe our XpressCF® platform is the first and only current Good Manufacturing Practices, or cGMP, compliant and scalable

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cell-free protein synthesis technology that has resulted in multiple product candidates in clinical development. We believe key advantages of our cell-free protein synthesis platform over conventional biologic drug discovery and development include:

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ability to rapidly produce a wide variety of protein structures in-house;

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ability to incorporate multiple, different non-natural amino acids in a single protein;

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faster cycle time, with the ability to generate protein in less than 24 hours compared to conventional 30-40 days;

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efficient drug discovery and early pharmacology and safety assessment; and

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rapid and predictable scalability.

We plan to leverage these capabilities to accelerate the discovery and development of potential first-in-class and best-in-class molecules.

The benefits of our XpressCF® and XpressCF+® platforms have resulted in multiple research and/or development collaborations with leaders in the field of oncology, including Ipsen, Astellas, Merck, BMS and EMD Serono. In 2024, we entered into an Exclusive License Agreement with Ipsen granting Ipsen worldwide rights to develop and commercialize STRO-003. This License Agreement was terminated in 2025. In 2022, we entered into a License and Collaboration Agreement with Astellas for the development of iADCs for up to three biological targets. In 2024, Astellas notified us that it would not be nominating a third target program. The first iADC in the Astellas collaboration entered clinical development in the first quarter of 2026; preclinical development of the iADC directed to the second of two targets remains ongoing.

Our research collaborations with Merck, BMS, and EMD Serono all resulted in development candidate molecules that entered clinical development. As part of our partners’ strategic portfolio review processes, each elected to terminate further clinical development of the candidate molecules following Phase 1 clinical studies. Through December 31, 2025, we have received an aggregate of approximately $1.016 billion in payments from all of our collaborations, which includes approximately $79 million in investments in our stock. We intend to selectively enter into additional collaborations with partners who are seeking efficient and effective drug discovery, preclinical development and manufacturing capabilities for the creation of novel therapeutics.

From 2018 through February 2025, we had been developing luveltamab tazevibulin, or STRO-002 or luvelta. In March 2025, we conducted a strategic review of our product portfolio. Following this review, we made the strategic decision to deprioritize additional investment into luvelta development, and development has since been terminated.

In December 2021, we entered into the Tasly License Agreement, as amended in April 2022, to develop and commercialize luvelta in the Greater China territory.

Beyond these programs and collaborations, we are developing a broader pipeline of next-generation protein therapeutics using our XpressCF® and XpressCF+® platforms. Our protein engineering and chemistry efforts are focused on maximizing therapeutic indices, and our technology allows us to rapidly test our therapeutic hypothesis in significantly more product candidates than conventional protein synthesis allows, with the goal of identifying the best molecule to advance to the clinic. We are also actively pursuing the discovery and development of other novel ADCs and next-generation ADC modalities, including iADCs, bispecific ADCs, and dpADCs.

Our Strategy

Our goal is to use our proprietary XpressCF® platform to create product candidates primarily against clinically validated targets. Key elements of our strategy are to:

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Advance STRO-004 through clinical development. We initiated clinical development of STRO-004 in the fourth quarter of 2025. We intend to develop STRO-004 for the treatment of solid tumors, potentially including cervical cancer, head and neck cancer, non-small cell lung cancer, bladder cancer, colorectal

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cancer, and pancreatic cancer. Given that TF is a clinically validated target for cervical cancer, along with STRO-004’s homogeneous design and preclinical anti-tumor activity and toxicity data, we believe it has the potential to be a best-in-class TF-targeted ADC and provide benefit to a broader patient population than approved TF-targeting agents, as well as potentially greater activity, stability and/or safety as compared to other investigational agents in development.

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Pursue strategic partnerships to maximize the potential value of our pipeline. We have assembled a management team with extensive experience in the biopharmaceutical industry, including drug discovery and development through commercialization, and our plan is to independently, or through partnerships, pursue the development and commercialization of our product candidates, to the extent possible. As we continue to advance our product candidates, we may opportunistically pursue additional strategic partnerships that maximize the value of our pipeline, including relationships, when possible, to potentially co-develop and co-commercialize one or more of our product candidates.

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Develop a diverse pipeline of novel product candidates with optimized therapeutic profiles. We intend to continue to build a broad pipeline of optimally designed, next-generation protein therapeutics, initially for cancer, using our XpressCF® and XpressCF® platforms. Our cell-free-based protein synthesis system enables the rapid and systematic evaluation of protein structure-activity relationships, which we believe will accelerate the discovery and development of molecules. We aim to take advantage of the most potent modalities, focusing primarily on ADCs, iADCs, bispecific ADCs and dpADCs, to create drugs that are directed primarily against clinically validated targets where the current standard of care is suboptimal.

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Strategically pursue additional collaborations to broaden the reach of our XpressCF® and XpressCF+® platforms. To maximize the value of our XpressCF® and XpressCF+® platform technology, we have historically entered into multitarget, product-focused collaborations with leaders in the field of oncology, including our iADC collaboration with Astellas. We intend to selectively enter into additional research collaborations with partners who are seeking efficient and effective drug discovery and manufacturing capabilities for the development of novel therapeutics. We intend to retain, to the extent possible, certain development and commercial rights to maximize the future potential value of product candidates discovered and developed using our XpressCF® platform.

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Strategically position our XpressCF® platform as a preferred alternative to conventional methods for manufacturing proteins for both research and clinical use. To further enhance the value of our XpressCF® platform, we are exploring granting nonexclusive access to our technology platform to potential licensees who are seeking access to efficient and effective drug discovery and manufacturing solutions, particularly those that can benefit from our XpressCF+® conjugation technology.

Cancers Remain a Major Unmet Medical Need

Cancers are the second leading cause of mortality in the United States and the leading cause of death for those under 65 years of age. The American Cancer Society estimated that there would be greater than 2 million new cases of cancer diagnosed and approximately 626,000 people would die of cancer in the United States in 2026.

Traditional Cancer Therapeutics

Cancer treatment has traditionally included chemotherapy, radiation, surgery, or a combination of these approaches. Chemotherapy agents and other small molecule targeted therapies can be effective in certain types of cancer, but they can also cause toxicities that may lead to life-threatening consequences, lower quality of life or early termination of treatment. Furthermore, these agents offer limited efficacy in many types of cancer.

Over the last twenty years, new paradigms of cancer research and treatment have emerged to address the limitations of existing treatments. Some of the most promising new approaches involve biologic therapies, including ADCs. ADCs have shown promise over the last decade with fourteen currently marketed products in the United States and hundreds of ADC candidates investigated in the clinic. ADCs use the foundation of monoclonal antibodies and small molecule drugs by targeting the delivery of chemotherapeutics to the tumor. They have shown clinical benefit in hematological and solid tumors and often have a better safety profile than systemically

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delivered chemotherapeutics. We believe our XpressCF® platform will provide enhanced therapeutic approaches for treating cancer to address these unmet needs and are exploring next generation biologics, including ADCs, iADCs, and dpADCs. The expectation is that multiple therapeutic modalities will be used in novel combinations to treat patients and provide the most potent anti-cancer effect.

Antibody-Drug Conjugates (ADCs)

ADCs are a highly potent improvement to monoclonal antibody oncology therapies. The key components of ADCs include an antibody, a stable linker, and a cytotoxic agent (warhead). The antibody is used to target and deliver cytotoxic agents to tumor cells. ADCs can be mono, bispecific, or multi-specific. The intended result of this powerful and targeted approach is greater tumor cell death and less systemic tolerability issues as compared to traditional chemotherapy. The following diagram shows the component parts of an ADC.

Kadcyla and Adcetris were the first of the new generation of ADCs to be approved for the treatment of specific subsets of breast cancer and lymphoma, respectively. Several more ADCs are currently on the market in the U.S.: Besponsa, Mylotarg, Polivy, and Zynlonta were approved for the treatment of specific subsets of leukemia and lymphoma; Padcev was approved for the treatment of bladder and urinary tract cancers; Enhertu and Trodelvy were approved for the treatment of breast cancer as well as gastric and urinary tract cancers respectively; Tivdak was approved for the treatment of cervical cancer; Elahere was approved for the treatment of ovarian cancer; and Datroway was approved for the treatment of a subset of breast cancer in January 2025. Several of these drugs, such as Enhertu and Datroway, have gained label expansions subsequent to their initial approvals. In the meantime, Emrelis was approved in May 2025 for treating high c-Met-expressing non-small cell lung cancer, and Blenrep was re-approved for multiple myeloma in October 2025 after being withdrawn in 2022. These approved therapies demonstrate that ADCs have an emerging role in the armamentarium of cancer therapeutics.

Limitations to Current ADC Approaches

Despite the approvals of these ADCs and hundreds more being investigated in clinical development, there have been challenges in achieving the full clinical potential of this modality. We believe these challenges are directly related to the following:

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Heterogeneity as a Result of Imprecise and Variable Conjugation. Many ADCs, both those approved and those in development, use imprecise technologies that opportunistically attach the cytotoxic payload to naturally occurring amino acids within the antibody and result in a heterogeneous mixture. In these mixtures, the number and site location of the linker-warhead can vary significantly from antibody to antibody within the single ADC product. These many different forms in the final product are likely to perform differently, with some forms carrying insufficient cytotoxin to kill the tumor, and some forms carrying too high a load resulting in unintended toxicities. The overall performance of the heterogeneous ADC is therefore the average activity of the different species within the ADC mixture, which may limit both efficacy and tolerability. For these reasons, we believe this current class of ADCs, which are heterogeneous mixtures, are suboptimal for effective cancer treatment. The figure below compares homogeneous and heterogeneous ADCs.

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Suboptimal Linker-Warhead Positioning. Conventional ADC technologies use conjugation chemistry to attach linker-warheads to naturally occurring amino acids within an antibody; therefore, the position is dictated by the pre-existing amino acid sequence. Published research studies have demonstrated that linker-warhead positioning along an antibody can have significant effect on the ability of an ADC to kill tumor cells, with some positions resulting in suboptimal killing. This position effect also contributes to the challenge of a heterogeneous ADC mixture. We believe that superior ADCs can be developed using technologies that allow linker-warhead positioning to be fine-tuned to empirically determined sites for maximal therapeutic benefit.

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Lack of Tumor Specificity Due to Linker Design. One of the major challenges in ADC technology has been to develop linking chemistries that ensure that warheads are only released from the antibody within the tumor microenvironment, and not released within the blood or healthy tissue as the ADC is delivered systemically and travels through the body. We believe that safer ADCs can be developed by utilizing non-natural amino acids that enable state-of-the-art chemistries to ensure that the warhead is not prematurely released. In addition, linker chemistries that rely on proteinases preferentially expressed in the tumor such as cathepsin and β-Glucuronidase, can provide more tumor specific release of the active catabolites and a resulting better safety profile.

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Mechanism of Action of Cytotoxin Payloads. Beyond potent cytotoxic activity of ADC payloads, there are additional attributes that may lead to better efficacy and more durable responses. Payloads that induce bystander activity, which is dependent on the ADC target engagement, but also kills surrounding cells within the tumor, are thought to result in broader activity. Additionally, some payloads can induce immunogenic cell death pathways. These pathways not only cause potent tumor cell killing but also produce an immunological phenotype in the cancer cells, known as immunogenic cell death, or ICD. Different payload types induce variable levels of ICD, which can induce an immune response against endogenous tumor antigens, contributing to tumor elimination and improved outcomes. Importantly, there is an emerging trend in the clinic that ADCs that induce higher levels of ICD combine better with checkpoint inhibitors, including PD-1/L1 antibodies.

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Limitations of Topo1 inhibitor payloads. When compared to first generation, tubulin inhibitor-based ADCs such as T-DM1, exatecan-delivering ADCs, such as Enhertu or raludotatug deruxtecan, or R-DXd, display significant improvements in safety and efficacy measures observed in preclinical and clinical studies. Despite the progress made, serious adverse events and efficacy challenges remain. For example, upon prolonged treatment with DXd-based ADCs, a small but significant fraction of patients develop interstitial lung disease, or ILD. This adverse event is observed independent of the tumor antigen targeted by the ADC. ILD is difficult to treat and can be fatal if not detected in a timely manner. One potential cause of ILD is Fc gamma-mediated uptake of ADCs by alveolar macrophages in the lung, causing internalization followed by payload release, ultimately leading to ILD.

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Low potency of exatecan-delivering ADCs: Exatecans are, in general, less potent inducers of tumor cell death compared to tubulin inhibitors. Therefore, low copy number tumor antigens and/or antigens with low internalization rates may be poor targets for exatecan-based ADCs due to low potency.

Dual conjugations to enable iADC and dpADC modalities to address current limitations of conventional ADCs and to optimize the therapeutic index, or TI

XpressCF® enables the incorporation of non-natural amino acids into antibody sequences and results in site specific conjugation of drug payloads. More recently, we have developed technology to enable incorporation of two different non-natural amino acids that allows for the site-specific conjugation of two different payloads, providing the opportunity to combine pharmacology into a single molecule. One example of these dual-payload concepts is the iADC, which includes both an immunostimulatory and a cytotoxic payload in the same molecule. We believe these iADC concepts are the first use of dual conjugation combining a conventional cytotoxin with an immunostimulatory payload to drive not only direct killing of the tumor cells but an immune response against the tumor. These iADC molecules utilize immune agonists such as TLR 7, TLR 8 and STING agonists that are believed to induce activation of innate immune cells within the tumor microenvironment and resulted in more complete responses and protective anti-tumor immune responses in preclinical tumor models. This dual conjugation approach is the basis for our research collaboration with Astellas, focused on the discovery of iADC molecules for treatment of solid tumors.

In addition to immune modulators, additional payloads can be incorporated into our dual conjugation approach. These dpADC concepts are focused on validated targets that are upregulated in tumors that do not respond well to existing therapies. Our goal is to provide more durable responses in hard-to-treat tumors by combining two payloads that may overcome the onset of resistance to single payload ADCs. The therapeutic benefit of combining microtubule inhibitors, or MTIs, with exatecan-based ADCs has been demonstrated in the clinic by coadministration of two ADCs with either an MTI or exatecan-based payload. We believe that the use of payloads that induce tumor cell death via different mechanism of action may reduce or delay development of resistance to either one of the payloads. We are also exploring dual-payload concepts combining inhibitors of DNA repair with exatecan-based payloads. We believe that blocking alternative signaling pathways by combining a DNA double-strand repair inhibitors, or DDRi, with exatecan-based payloads may be a promising dual-payload approach for BRCA1/2 mutant tumors.

Our Proprietary XpressCF® Platform

While ADCs, iADCs, and dpADCs hold significant promise, drug developers working with these complex biologics face significant design and development challenges. Optimizing these complex biological structures is a challenging, trial and error process that requires the refinement of several properties in tandem. This iterative

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process is cumbersome and fraught with significant limitations. As a result, the drug candidate nominated for development is often plagued by inefficient design properties, which then translates to a suboptimal therapeutic index when investigated in the clinic.

Our XpressCF® platform seeks to address these significant shortcomings. We believe our cell-free-based protein synthesis technology allows for efficient and proper design exploration to be conducted prior to nominating a lead drug candidate. In addition, we believe we can optimally design these types of complex biologics in a manner that is ideal for subsequent production at relevant scale and manufacture. We believe we are the only company with products in clinical development that has the capability to produce cell-free-based protein synthesis at scale. We believe we have a significant advantage over other development approaches in this space.

Overview of Our XpressCF® Platform

Our XpressCF® platform is fundamentally different from the conventional cell-based protein synthesis approach in that we separate the production of the cell mass from the production of the protein.

We first generate a cellular mass from our proprietary cell line from which we harvest the inner cellular machinery for making proteins. The cellular mass is generated from our highly engineered variant of Escherichia coli, or E.coli bacteria, and has been optimized to make an extract that can produce complex mammalian proteins. These cells are grown over the course of several days, harvested, broken apart, clarified, and stored as a cell mass for future production of our protein therapeutics. We refer to this proprietary cell mass as extract, or XtractCF®. The extract includes necessary components for energy production, transcription and translation, and can be used to support cell-free protein synthesis. This extract can then be used agnostically to manufacture a wide variety of therapeutic proteins and protein fragments without the need to generate further cell lines.

As a result, protein synthesis then becomes a predictable and reproducible biochemical reaction, independent of the constraints of a cell. A specific DNA sequence is added to the extract, which results in the coding and expression of the desired protein in less than 24 hours. Using this process, we can express hundreds or thousands of DNA sequences simultaneously within the same cell-free extract system and therefore can make and purify hundreds or thousands of unique proteins at the same time. This allows us to perform rapid expression, testing and characterization of many variants early in discovery to elucidate structure-activity relationships. Structure-activity relationship refers to how changes to the structure of a protein can lead to modify a molecule’s properties, such as binding, internalization, functional activity and stability, which are properties that are key to the therapeutic protein’s efficacy and tolerability in the patient. We are thereby able to optimize many properties with high specificity, including: binding efficiency to each antigen target, spatial orientation, linker design, target killing efficiency, immunological activity, protein expression, and folding efficiency and stability.

Advantages of Our XpressCF® Platform

We believe the advantages of our cell-free-based protein synthesis technology platform include:

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Ability to Rapidly Produce and Evaluate a Wide Variety of Protein Structures In-house. By decoupling the production of the cell-free extract from the production of the protein, we are able to stockpile large quantities of cell-free extract from which we are able to manufacture a wide variety of proteins without the need to generate individual cell lines, including cytokine-based immuno-oncology therapeutics, ADCs, iADCs and bispecific antibodies. Additionally, our dual conjugation dpADC technology has enabled ADCs that combine two distinct small molecules with different pharmacologies onto a single antibody.

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Ability to Incorporate Non-Natural Amino Acids. Our technology allows for efficient incorporation of a non-natural amino acid in any location in an antibody or protein with high precision and fidelity, which we believe allows for the design of optimized protein conjugates. Further, our non-natural amino acid conjugation technology permits complete and rapid stable linkage between our linker components and the non-natural amino acid, resulting in a single species without loss of efficiency as the conjugates become increasingly complex.

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Absence of Fc-gamma Receptor Binding. Antibodies produced using the XpressCF® platform have not been shown to bind the Fc-gamma receptor, and therefore are not subject to Fc-gamma mediated uptake

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by alveolar macrophages, which we believe results in reduced nonspecific payload release in the lung, reducing the potential for ILD.

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Faster Cycle Time. Our ability to quickly produce thousands of protein variants in parallel allows us to rapidly express, test and characterize many variants early in discovery to elucidate structure-activity relationships and identify opportunities for superior therapeutic profiles, as well as new intellectual property. We are therefore able to efficiently optimize many properties with high specificity in parallel.

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Efficient Drug Discovery and Early Pharmacology and Safety Assessment. Our cell-free technology creates the opportunity for accelerated pharmacology and safety assessments during the design and discovery phase of product development. This approach allows us to generate optimized proteins early in our discovery process, which can be transitioned seamlessly to clinical scale production using the same cell-free process.

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Rapid and Predictable Scalability. Our cell-free extract does not need to be modified in any manner as we scale from research to preclinical to clinical to commercial production. This enables us to move more rapidly to the clinic by eliminating master cell banking activities and significantly de-risks scale-up to manufacturing.

Our XpressCF® Solution for ADCs, iADCs, Bispecific ADCs, and dpADC Therapeutics

We believe our technology enables new approaches to ADCs, iADCs, bispecific ADCs, and dpADC drug discovery, development and manufacturing. Key attributes are:

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Homogeneous Design. Our XpressCF+® platform enables precise and specific placement of non-natural amino acids in defined numbers and positions within our engineered proteins. These non-natural amino acids then serve as highly stable attachment sites, also known as conjugation sites, for chemical functional groups. For example, we attach linker-warheads to non-natural amino acids within our antibodies to create single-species, tumor-killing ADCs. Similarly, we can attach polyethylene glycol polymers onto non-natural amino acids within our cytokine-based therapeutics to create single-species immunotherapies designed for extended pharmacokinetics and safety.

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Experimentally Defined Structure-Activity Relationships. Our cell-free technology enables rational design of protein therapeutics through a rapid, reiterative process that experimentally defines structure-activity relationship for cytokine-based therapeutics, ADCs, iADCs, bispecific ADCs and dpADCs. This approach allows us to explore a wide variety of structural features and formats in parallel as we optimize therapeutic candidates. For example, the precise location of chemical conjugation sites directly affects the activity of both ADCs and cytokine-based therapeutics. Our proprietary technology is key to our ability to define the best number and positions of non-natural amino acids for conjugation based on: conjugation efficiency; functional activity/pharmacological properties; and pharmacokinetics and safety. This design flexibility is also an important aspect of our discovery approach to other protein therapeutics. For example, we are able to make and directly compare a variety of pairings and structural formats for our ADC molecules to ensure that we have optimized sites of conjugation, the number of payloads on each antibody (drug-antibody ratio, or DAR) and linker chemistry. We have identified examples wherein changing just one of these parameters can significantly impact the safety, efficacy and stability of the ADC. Further, we have demonstrated the ability to introduce more than eight non-natural amino acids into a single antibody structure, without impacting the expression levels of engineered antibodies, permitting ADCs with a DAR of greater than eight. Most conventional conjugation methods are limited by a DAR of eight, due to the availability of only eight interchain cysteines, which are used for conjugation with conventional methods. In addition, our XpressCF+® platform enables integration of two different types of non-natural amino acid, which can be used to precisely conjugate two different payloads to the same antibody, and allows us to engineer additional pharmacological properties, including iADCs and dpADC therapeutics. We believe the ability to precisely define the optimal sites of conjugation, coupled with optimized conjugation chemistry and linker chemistry, enables us to engineer ADCs, including iADCs and dpADCs, with industry-leading stability and pharmacokinetic profiles, which could result in improved safety and efficacy leading to in meaningful patient benefit.

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Efficient Transition from Research Scale to Development Scale Protein Production. Protein therapeutics can encounter obstacles, or even fail, during the transition from research cell lines to cGMP cell lines appropriate for clinical development and commercialization. Our XpressCF® platform may reduce these risks because it can rapidly produce different protein types from a single proprietary extract, which can be scaled for discovery, development and ultimately, we believe, commercialization of cytokine-based immuno-oncology therapeutics, ADCs, iADCs, bispecific ADCs and dpADCs.

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Manufacturable Dual Conjugations. Our XpressCF+® platform allows us to manufacture antibodies that contain two different non-natural amino acids that are substrates for mutually orthogonal site-specific conjugation reactions. This advantage permits dual conjugation, resulting in homogenous iADC or dpADC dual conjugate molecules with two different precisely placed payloads.

Accordingly, we use our XpressCF® platform to discover and develop cancer therapeutics by empirically determining the optimum structure-activity relationships for cytokine-based immuno-oncology therapeutics, ADCs, iADCs, bispecific ADCs and dpADCs and transitioning those products to cGMP compliant manufacturing.

Our Collaborations Validate Our Technology

Our XpressCF® platform has garnered the attention of leading pharmaceutical and biopharmaceutical companies and resulted in collaborations to discover and develop novel therapeutics. We have leveraged these strategic partnerships to extend our own capabilities and broaden the scope of our XpressCF® platform. Through December 31, 2025, all of our collaborations have provided us with an aggregate of approximately $1.016 billion in payments, which includes approximately $79 million in investments in our stock. Our currently active collaborations include:

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Astellas Collaboration. The collaboration and license agreement with Astellas covers the discovery and development of immunostimulatory antibody-drug conjugates for two biological targets.

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Vaxcyte Relationship. We have granted Vaxcyte the right to discover and develop vaccines for the prophylaxis and treatment of infectious diseases. Vaxcyte’s most advanced product candidates are VAX-31 and VAX-24, 31-valent and 24-valent, respectively, pneumococcal conjugate vaccine candidates under investigation for the prevention of invasive pneumococcal disease in adults and adults and infants, respectively. Further, in the fourth quarter of 2023, Vaxcyte exercised an option to obtain development and manufacturing rights for XtractCF® providing Vaxcyte the right to make and source our cell-free extract for research, development, and manufacture of vaccines for the prophylaxis and treatment of infectious disease.

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Our Pipeline of Product Candidates and Discovery/Preclinical Programs

Our current product candidates and Discovery and Preclinical stage programs, all based on our proprietary XpressCF® platform, are summarized in the chart below:

Our Product Candidates

STRO-004, An ADC Directed Against Tissue Factor

Our lead developmental asset is STRO-004. STRO-004 is a TF-targeting ADC for the treatment of TF-expressing solid tumors, potentially including cervical, head and neck, lung, pancreatic, bladder, and colorectal cancers. STRO-004 is an anti-TF human IgG1 antibody conjugated using our XpressCF+® platform technology to a cleavable DBCO-PEGylated β-glucuronidase-exatecan linker-payload, at a DAR of approximately eight. There is an approved ADC targeting TF, TIVDAK®, developed by Seattle Genetics and Genmab A/S, which is approved for the treatment of recurrent or metastatic cervical cancer. In preclinical in vitro and in vivo studies benchmarking STRO-004 against a TIVDAK® surrogate molecule, we observed comparable antitumor activity but achieved 5- to 10-fold higher dose levels in nonhuman primate safety studies for STRO-004. Therefore, we believe that STRO-004 has the potential for an improved clinical therapeutic index over existing standard of care. We believe these features present a unique opportunity for clinical development of STRO-004 to address unmet medical needs in multiple solid tumors.

We believe STRO-004 has been precisely designed and optimized to provide the potential for a best-in-class ADC targeting TF. Our proprietary non-natural amino acid, which provides the substrate for conjugation to our proprietary β-glucuronidase cleavable exatecan linker warhead, has been placed at what we believe are the optimal sites in the amino acid sequence of our high affinity anti-TF antibody, resulting in enhanced performance and stability in preclinical in vitro and in vivo models. These models also suggest that our β-glucuronidase cleavable linkers may provide greater tumor specificity and enhanced tolerability relative to a protease-cleavable linker delivering an exatecan payload. In particular, in a nonhuman primate safety study, we did not observe neutropenia, ocular toxicity signals or ILD signals, even in the highest dose cohort for STRO-004. Finally, our preclinical testing has shown that the exatecan payload delivered by STRO-004 elicits potent tumor cell killing, bystander activity and immunogenic cell death, which we believe may provide meaningful clinical benefit to patients.

STRO-004 is currently in a Phase 1 open-label, multicenter trial and is designed to evaluate the safety, pharmacokinetics, and preliminary anti-tumor activity of STRO-004 in patients with advanced TF-expressing solid

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tumors, including non-small cell lung cancer, head and neck squamous cell carcinoma, cervical cancer, colorectal cancer, pancreatic ductal adenocarcinoma, endometrial cancer, and bladder cancer. The dose-escalation phase includes multiple cohorts with ascending dose levels, supported by strong tolerability in non-human primates at up to 50 mg/kg. Dosing of patients in the dose level 2 cohort was completed and dosing of patients in the dose level 3 cohort was initiated in February 2026. We expect to report initial preliminary data, including safety and pharmacokinetic data, from this trial in mid-2026.

STRO-004 Business Opportunity

We believe TF is a favorable target for an ADC due to its clinical validation in cervical and head and neck cancer and its prevalence across many solid tumors, including cervical, head and neck, lung, pancreatic, bladder and colorectal cancers. Its expression is correlated with poor prognosis in different cancers.

STRO-227, A Dual-Payload ADC Directed Against PTK7

In 2025, we nominated STRO-227 for further development. STRO-227 is a PTK7-targeting ADC for the treatment of PTK7-expressing solid tumors. STRO-227 is an anti-PTK7 human IgG1 antibody conjugated using our XpressCF+®platform technology to a cleavable DBCO-PEGylated β-glucuronidase-exatecan linker-payload, at a DAR of approximately eight and to a cleavable hydroxy-PEGylated β-glucuronidase-mono-methyl auristatin E, or MMAE, at a DAR of approximately two. Currently, there are no therapeutics approved that specifically target PTK7, although there are several PTK7-targeting ADCs in development. Based on preclinical in vitro and in vivo data, we believe that STRO-227 has the potential for overcoming resistance and prolonging responses when compared to other PTK7-targeting ADCs. We believe these features present a unique opportunity for clinical development of STRO-227 to address unmet medical needs in multiple solid tumors.

We believe STRO-227 has been precisely designed and optimized to provide the potential for a best-in-class ADC targeting PTK-7. Our proprietary non-natural amino acid, which provides the substrate for conjugation to our proprietary β-glucuronidase cleavable exatecan linker warhead, has been placed at what we believe are the optimal sites in the amino acid sequence of the heavy chain of our high affinity anti-PTK7 antibody. Similarly, the non-natural amino acid providing the conjugation site for the β-glucuronidase cleavable MMAE linker warhead has been precisely placed at what we believe to be the optimal site in the light chain. Taken together, we believe this design results in the enhanced performance and stability observed in preclinical in vitro and in vivo models. These models also suggest that our β-glucuronidase cleavable linkers may provide greater tumor specificity and enhanced tolerability relative to a protease-cleavable linker delivering an exatecan or tubulin-targeting payload. Finally, our preclinical testing has shown that STRO-227 elicits potent tumor cell killing, bystander activity and immunogenic cell death, which we believe may provide meaningful clinical benefit to patients.

STRO-227 Business Opportunity

We believe PTK7 is a favorable target for an ADC due to its early clinical validation in multiple cancers, as well as its prevalence in solid tumors, including lung, TNBC, ovarian, endometrial, colorectal, renal cell carcinoma, gastric/GEJ and cervical. Its expression is correlated with poor prognosis in different cancers. Currently, there are no approved therapeutics that specifically target PTK7, but it is a target of increasing interest with several clinical-stage ADCs in development, including DAY301 (Phase 1), LY4175408 (Phase 1), KIVU-107 (Phase 1), and SKB518 (Phase 1 in China). As all of these programs are single payload ADCs made using conventional ADC technology, we believe that STRO-227, as a dual-payload ADC, has best in-class potential relative to these molecules.

STRO-006, An ADC Directed Against Iβ6

In 2025, we also nominated STRO-006 for further development. STRO-006 is an ITGB6-targeting ADC for the treatment of ITGB6-expressing solid tumors, including non-small cell lung cancer, or NSCLC, and head and neck cancer. STRO-006 is an anti-ITGB6 human IgG1 antibody conjugated using our XpressCF+® platform technology to a cleavable DBCO-PEGylated β-glucuronidase-exatecan linker-payload, at a DAR of approximately eight. Currently, there are no therapeutics approved that specifically target ITGB6, although there is one ITGB6-targeting ADC, sigvotatug vedotin, or SV, also known as SGN-V6A, in Phase 3 testing targeting NSCLC and in Phase 1 testing for other solid tumors. In addition to SV, Pfizer is developing at least two additional ADCs

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targeting ITGB6. Based on preclinical in vitro and in vivo data, we believe that STRO-006 has the potential for an improved therapeutic index compared to SV.

We believe STRO-006 has been precisely designed and optimized to provide the potential for a best-in-class ADC targeting ITGB6 that could address unmet medical needs in NSCLC, head and neck cancer, and other solid tumors. Our proprietary non-natural amino acid, which provides the substrate for conjugation to our proprietary β-glucuronidase cleavable exatecan linker warhead, has been placed at what we believe are the optimal sites in the amino acid sequence of our high affinity anti-ITGB6 antibody, resulting in enhanced performance and stability in preclinical in vitro and in vivo models. These models also suggest that our β-glucuronidase cleavable linkers may provide greater tumor specificity and enhanced tolerability relative to a protease-cleavable linker delivering an exatecan payload. In particular, in a nonhuman primate safety study, we did not observe neutropenia, ocular toxicity signals or lung toxicity signals even in the highest dose cohort for STRO-006. Finally, our preclinical testing has shown that the exatecan payload delivered by STRO-006 elicits potent tumor cell killing, bystander activity and immunogenic cell death, which we believe may provide meaningful clinical benefit to patients.

STRO-006 Business Opportunity

We believe ITGB6 is a favorable target for an ADC due to its emerging clinical validation in NSCLC, as well as its prevalence in solid tumors, including head and neck cancer. Its expression is correlated with poor prognosis in different cancers. As mentioned above, there are no approved therapeutics that specifically target ITGB6, but it is a target of increasing interest with several clinical-stage ADCs in development, most notably SV (Phase 3) and the two other ITGB6-targeting ADCs in development by Pfizer (PF08046876 and PF08052667).

Additional Discovery Efforts

We are also actively researching to identify new ADCs and dpADCs to add to our pipeline. We have multiple ADC discovery programs ongoing using our XpressCF+® platform. Our protein engineering and chemistry efforts are focused on maximizing therapeutic indices, and our technology allows us to rapidly test our therapeutic hypotheses in significantly more product candidates than conventional protein synthesis allows in order to identify the best molecule to advance to the clinic.

We have also expanded our ADC technology platform to include dpADCs, including iADCs. For iADCs, our XpressCF+® platform has enabled homogeneous, dually-conjugated immunostimulant and cytotoxic warheads on a single ADC molecule. Our novel iADC design is intended to deliver two different drugs directly to the tumor, to not only kill tumor cells but also potentially prime a local immune response to the patient’s particular tumor cells. We believe that our iADC approach has the potential to create a new therapeutic opportunity by combining the best features of an ADC with the biology of a personalized vaccine.

In addition, development of our XpressCF+® platform to enable homogenous, dually-conjugated iADCs also enables us to discover, develop and manufacture other dpADC molecules, such as STRO-227. In these dpADC molecules, two different linker-warheads are precisely conjugated at specific positions to deliver two different small molecule payloads to a single cancer cell. We are actively investigating different combinations of payloads to identify synergistic pairings with differentiated toxicity profiles. To date, we have assessed combinations that include two different cytotoxins, such as a tubulin-targeting agent combined with a topoisomerase-targeting agent, and a cytotoxin and a potentiating molecule, such as a topoisomerase-targeting agent combined with a DDRI. We believe such dpADC molecules have the potential to provide the next generation of highly potent cancer therapeutics with acceptable safety and tolerability.

Collaboration and License Agreements

Astellas Agreement

In June 2022, we entered into a license and collaboration agreement with Astellas, or the Astellas Agreement, for the development of immunostimulatory antibody-drug conjugates for up to three biological targets, to be identified by Astellas. In June 2024, Astellas notified us that it would not be nominating a third target program. This decision was based on Astellas' strategic portfolio considerations. We will conduct research and preclinical development of any compound (as designated by Astellas) in each of the two programs in accordance with the

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terms of a research plan between us and Astellas. Astellas will have an exclusive worldwide license to develop and commercialize any such designated compound, subject to our rights to participate in cost and profit sharing in the United States, as described below. The first Astellas program began clinical development in the first quarter of 2026.

Pursuant to the Astellas Agreement, we received from Astellas a one-time, nonrefundable, non-creditable, upfront payment of $90.0 million during the year ended December 31, 2022.

We are also eligible to receive up to $422.5 million in development, regulatory and commercial milestone payments for each product candidate, and tiered royalties ranging from low double-digit to mid-teen percentages on worldwide sales of any commercial products that may result from the collaboration, subject to customary deductions under certain circumstances. We can also elect to convert any product candidate into a cost and profit-sharing arrangement, for the United States only. In the event we make such election, we will share commercialization costs and profits relating to such product candidate equally with Astellas in the United States, and no royalties will be due from Astellas for net sales of such product candidates in the United States.

The Astellas Agreement contains customary provisions for termination, including by Astellas for convenience upon 30 days’ written notice and by either party for cause, including for material breach (subject to cure). We have certain reversion rights as to product candidates in connection with certain termination events.

Vaxcyte (formerly known as SutroVax) Relationship

In 2013, we and Johnson & Johnson Innovation, through the Johnson & Johnson Development Corporation, provided initial co-funding for Vaxcyte, with which we have a license agreement, a supply agreement, an option agreement and a manufacturing rights agreement related to certain development and manufacturing rights. Under the license agreement, Vaxcyte has the right to use the XpressCF® and XpressCF+® platforms to discover and develop vaccine candidates for the treatment or prophylaxis of infectious diseases. The lead programs for Vaxcyte are VAX-31 and VAX-24, its 31-valent and 24-valent, respectively, pneumococcal conjugate vaccine candidates. Vaxcyte is responsible for performing all research and development activities, and we provide technical support and supply XtractCF® and other materials to Vaxcyte.

In May 2018, we entered into a Supply Agreement with Vaxcyte, wherein Vaxcyte engaged us to supply extracts and custom reagents, as requested by Vaxcyte. The pricing is based on an agreed upon cost plus arrangement.

In December 2022, we entered into a letter agreement, or the Vaxcyte Agreement, with Vaxcyte and granted Vaxcyte an option, or the Option, to obtain development and manufacturing rights for XtractCF® that, when exercised, would grant Vaxcyte the right to make and source our cell-free extract for research, development, and manufacture of vaccines for the prophylaxis and treatment of infectious disease.

Pursuant to the Vaxcyte Agreement, we received a one-time, nonrefundable, non-creditable, upfront payment of $10.0 million in cash, and 167,780 shares of Vaxcyte common stock with a fair value of $7.5 million in December 2022.

Additionally, pursuant to the Vaxcyte Agreement, we and Vaxcyte agreed to negotiate the terms and conditions of a form definitive agreement to be entered into in the event Vaxcyte exercises the Option, or the Form Definitive Agreement. In September 2023, we and Vaxcyte mutually agreed upon the Form Definitive Agreement, and in October 2023, we received a $5.0 million payment from Vaxcyte.

Effective immediately upon agreement to the Form Definitive Agreement, we and Vaxcyte entered into Amendment No 3., or Amendment 3, to that certain license agreement between us and Vaxcyte, dated August 1, 2014, and amended and restated on October 12, 2015, and amended again on May 9, 2018 and May 29, 2018, or the License Agreement. Amendment 3 amended certain terms of the License Agreement including with respect to (i) royalty reduction provisions applicable in the event of expiration of relevant patent claims, which would result in lower royalties payable by Vaxcyte under certain circumstances, (ii) the ownership, prosecution, maintenance and enforcement of certain intellectual property rights licensed or arising under the License Agreement, and (iii) the timing and form for financial reporting of royalty payment calculations.

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In November 2023, or the Exercise Date, Vaxcyte exercised the Option by submitting written notice thereof to us and concurrently paid us $50.0 million in cash as the first of two installment payments for the Option exercise price. In May 2024, Vaxcyte paid us an additional $25.0 million in cash as the second of two installment payments for the Option exercise price under the Vaxcyte Agreement. Upon the occurrence of certain regulatory milestones, Vaxcyte would be obligated to pay us certain additional milestone payments totaling up to $60.0 million in cash. In the event that Vaxcyte undergoes a change of control, certain rights and payments may be accelerated.

We are eligible for four percent royalties on worldwide net sales of any vaccine candidates for human health use under the license agreement, except for royalties on sales of vaccines for prophylaxis of invasive pneumococcal disease, such as VAX-24 or VAX-31, which are owned by Blackstone, as discussed below. Also, we retain the right to discover and develop vaccines for the treatment or prophylaxis of any disease that is not caused by an infectious pathogen, including cancer.

Vaxcyte has the right to terminate the Vaxcyte license agreement for convenience upon prior written notice. Either party may terminate for the other party’s material uncured breach under certain circumstances.

Tasly Relationship

In December 2021, we entered into the Tasly License Agreement with Tasly to grant an exclusive license to develop and commercialize STRO-002 in Greater China. Tasly has the right to pursue the clinical development, regulatory approval, and commercialization of STRO-002 in multiple indications, including ovarian cancer, NSCLC, TNBC, and other indications in Greater China. We retained development and commercial rights of STRO-002 globally outside of Greater China, including the United States.

Tasly has the right to terminate the Tasly License Agreement for convenience or other reasons specified in the Tasly License Agreement, upon prior written notice. Tasly has not disclosed its plans for development of STRO-002 in Greater China following our decision to deprioritize development outside of Greater China in 2025.

Blackstone Relationship

In June 2023, we entered into a purchase and sale agreement with Blackstone, or the Blackstone Agreement, to sell to Blackstone a revenue interest in our 4% royalty on potential future sales of Vaxcyte’s products, including Vaxcyte’s pneumococcal conjugate vaccine, or PCV, products such as VAX-24 and its second-generation PCV product, VAX-31.

Under the Blackstone Agreement, Blackstone paid us an initial upfront payment of $140.0 million in June 2023, with potential payments totaling up to $250.0 million triggered at various return thresholds to Blackstone under the Blackstone Agreement. In addition, under the Blackstone Agreement, we agreed to certain covenants with respect to the exercise of its rights under the Vaxcyte License Agreement, including with respect to the right to amend, assign and terminate the Vaxcyte License Agreement. The Blackstone Agreement contains other customary terms and conditions, including representations and warranties, covenants and indemnification obligations in favor of each party.

Following agreement with Vaxcyte on the Form Definitive Agreement and upon effectiveness of the Amendment, the revenue interest in the 4% royalty on potential future sales of Vaxcyte products other than Vaxcyte’s PCV products reverted to us. As such, we retain the revenue interest in royalties from Vaxcyte on sales of all products other than a PCV product, such as VAX-24 or VAX-31.

Stanford License

In October 2007, we entered into an Amended and Restated Exclusive Agreement, or the Stanford License, with the Board of Trustees of the Leland Stanford Junior University (Stanford), that grants us an exclusive license, with the right to sublicense, under the patent rights owned by Stanford covering certain technology rights related to our XpressCF® expression system.

We owe Stanford annual license maintenance fees of $75,000, which may be creditable against earned royalties in such year and are required to reimburse Stanford for ongoing patent-related costs. We are also

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required to pay to Stanford low single digit royalties on net sales and to share any sublicensing income received related to the licensed technology. We may terminate the agreement at any time upon 30 days’ written notice.

Manufacturing

We have significant expertise in the production of therapeutic biologics. Our proprietary XpressCF® platform is a cell-free protein synthesis technology that enables rapid and systematic process development, streamlined scale-up and GMP manufacturing.

Extract and Reagents

In 2025, we made the strategic decision to cease operations at our GMP manufacturing facility in San Carlos, California for manufacture of our cell-free extract and reagents in service of our clinical trials and supply commitments. We have identified a contract manufacturing organization, or CMO, to serve as our strategic partner for the production of cell-free extract and have completed technology transfer to this CMO. Similarly, we have identified a CMO to produce custom reagents used in our cell-free production and have completed this technology transfer as well. Given the success of these technology transfers, we have wound down our manufacturing activities in our San Carlos facility and expect to exit the facility completely in 2026 upon expiration of our leases.

Drug Substance and Drug Product

Our process development and manufacturing strategies are tailored to rapidly advance our product candidates, including the use of a supply chain of established CMOs to ensure successful execution. Our strategy for the production of antibodies is to manufacture with our CMO network. We have identified multiple CMOs with the ability to produce the antibody component of our products at different scales and we have successfully completed technology transfer of the manufacturing process to more than one of these CMOs. The production of all other necessary elements for the manufacture of our ADC product candidates, and the final manufacture of the ADC drug product, will also be handled entirely by CMOs. Our XpressCF+® platform has been successfully used for manufacturing several antibodies containing non-natural amino acids and requires minimal process optimization to support early clinical phase manufacturing. We utilize industry established production steps for the purification of our antibodies. The CMOs we have selected have strong track records in cGMP manufacturing with expertise in clinical or commercial drug manufacturing for cytotoxic agents, large scale manufacture of antibodies, conjugation and fill-finish of therapeutic biologics. All activities from cell-free extract production to formulated drug product are performed to maintain aggressive timelines and minimize delays.

Competition

The biotechnology and biopharmaceutical industries, and the immuno-oncology subsector, are characterized by rapid evolution of technologies, fierce competition, and strong defense of intellectual property. Any product candidates that we successfully develop and commercialize will have to compete with existing therapies and new therapies that may become available in the future. While we believe that our proprietary XpressCF® platform and scientific expertise in the field of biologics and immuno-oncology provide us with competitive advantages, a wide variety of institutions, including large biopharmaceutical companies, specialty biotechnology companies, academic research departments and public and private research institutions, are actively developing potentially competitive products and technologies. We face substantial competition from biotechnology and biopharmaceutical companies developing products in immuno-oncology. Our competitors include larger and better funded biopharmaceutical, biotechnological and therapeutics companies, as well as numerous small companies. Moreover, we also compete with current and future therapeutics developed at universities and other research institutions.

If our most advanced product candidates are approved, they will compete with a range of therapeutic treatments that are either in development or currently marketed. Currently marketed oncology therapeutics include a range of biologic modalities with the top selling products by class spanning tumor targeting monoclonal antibodies, to ADCs, to immune checkpoint inhibitors, to T cell-engager immunotherapies, to CAR-T cell therapies. In addition, numerous compounds are in clinical development for cancer treatment. The clinical development pipeline for cancer includes small molecules, antibodies, vaccines, cell therapies and immunotherapies from a variety of companies and institutions.

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We also face substantial competition from biotechnology and biopharmaceutical companies developing products with TF-targeted therapies. The most advanced clinically active agent targeting TF to date has been TIVDAK® (tisotumab vedotin-tftv; TF-011-MMAE), an ADC currently approved for recurrent or metastatic cervical cancer that is composed of a TF-binding antibody linked to the tubulin-disrupting antimitotic agent, MMAE, via a cleavable linker. Other pharmaceutical companies are developing TF-targeted ADCs for the treatment of a broad range of advanced or metastatic cancers, including the indications we may select for STRO-004 development. As discussed above, our STRO-006 and STRO-227 programs also face substantial competition, with multiple ITGB6-targeting and PTK7-targeting ADCs in clinical development for the treatment of a broad range of advanced or metastatic cancers, including the indications we may select for STRO-227 and/or STRO-006 development.

In addition, we face increasing competition from Chinese biotechnology and pharmaceutical companies, including Chinese state-owned or state-backed enterprises. China has become one of the world's leading developers of new drugs, and Chinese companies benefit from a regulatory regime that enables rapid, low-cost clinical trials that facilitate innovation. Furthermore, we compete with other large pharmaceutical companies, many of which have invested significantly in development in China, in acquiring or licensing Chinese product candidates, or in developing product candidates in China.

Many of our competitors, either alone or with strategic partners, have substantially greater financial, technical, manufacturing, marketing, sales, supply and human resources or experience than we have. Accordingly, our competitors may be more successful than us in obtaining approval for treatments and achieving widespread market acceptance, rendering our treatments obsolete or non-competitive. Accelerated merger and acquisition activity in the biotechnology and biopharmaceutical industries may result in even more resources being concentrated among a smaller number of our competitors. These companies also compete with us in recruiting and retaining qualified scientific and management personnel, establishing clinical trial sites and patient registration for clinical trials, and acquiring technologies complementary to, or necessary for, our programs. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies. Our commercial opportunity could be substantially limited in the event that our competitors develop and commercialize products that are more effective, safer, less toxic, more convenient or less expensive than our comparable products. In geographies that are critical to our commercial success, competitors may also obtain regulatory approvals before us, resulting in our competitors building a strong market position in advance of the entry of our products. We believe the factors determining the success of our programs will be the efficacy, safety and convenience of our product candidates.

Intellectual Property

We strive to protect and enhance the proprietary technology, inventions, and improvements that are commercially important to our business, including seeking, maintaining, and defending patent rights, whether developed internally or licensed from third parties. Our policy is to seek to protect our proprietary position by, among other methods, pursuing and obtaining patent protection in the United States and in jurisdictions outside of the United States related to our proprietary technology, inventions, improvements, platforms, and product candidates that are important to the development and implementation of our business. Our patent portfolio is intended to cover, but is not limited to, our technology platforms, our product candidates, and components thereof, their methods of use and processes for their manufacture, our proprietary reagents and assays, and any other inventions that are commercially important to our business. We also rely on trade secret protection of our confidential information and know-how relating to our proprietary technology, platforms, and product candidates, continuing innovation, as well as trademark protection and in-licensing opportunities to develop, strengthen, and maintain our proprietary position in our XpressCF® platform, XpressCF+® platform, and product candidates. We expect to rely on data exclusivity, market exclusivity, patent term adjustment and patent term extensions when available. Our commercial success may depend in part on our ability to obtain and maintain patent and other proprietary protection for our technology, inventions, and improvements; to preserve the confidentiality of our trade secrets; to maintain our licenses to use intellectual property owned or controlled by third parties; to defend and enforce our proprietary rights, including our patents; to defend against and challenge the assertion by third parties of their purported intellectual property rights; and to operate without the unauthorized infringement on the valid and enforceable patents and other proprietary rights of third parties.

We believe that we have a strong global intellectual property position and substantial know-how and trade secrets relating to our XpressCF® platform, XpressCF+® platform, and product candidates. Our patent portfolio as of December 31, 2025, contained 38 U.S. issued patents and 252 patents issued in ex-U.S. jurisdictions, including Europe, China, Japan, Australia and Singapore, and 46 U.S. pending applications, as well as 119 patent

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applications pending in ex-U.S. jurisdictions, including Europe, China, Japan, Australia and Singapore owned solely by us. These patents and patent applications include claims relating to:

Our patent portfolio includes the following families and/or groups of families:

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XpressCF® Platform. We have approximately 10 patent families related to our XpressCF® platform, which include claims directed to certain bacterial strains and extracts prepared therefrom and methods of producing thereof, extract formulations and methods of making thereof, methods of producing antibodies using prefabricated light chain, and methods of producing high cell density fermentations and extracts prepared therewith. Our issued patents, and any patents that may issue from our pending patent applications, related to our XpressCF® platform are expected to remain in force until various times between October 2033 and February 2046, absent any patent term adjustments or extensions.

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XpressCF+® Platform and ADC Platform. We have approximately 13 patent families related to our XpressCF+® platform and ADC platform, which include claims directed to para-azidomethylphenylalanine (pAMF) and proteins comprising pAMF, non-natural amino acid tRNA synthetases, antibodies with engineered CH2 domains, antibodies with site-specific glutamine tags, antibodies and antibody fragments containing one or more non-natural amino acids at defined positions in their amino acid sequences, dual conjugates (including iADC and dpADC), high drug antibody ratio (DAR) conjugates and methods of treating therewith, and methods of conjugation. Our issued patents, and any patents that may issue from our pending patent applications, related to our XpressCF+® platform and ADC platform are expected to remain in force until various times between June 2033 and October 2046, absent any patent term adjustments or extensions.

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STRO-004. We have approximately 2 patent families related to STRO-004, which include composition of matter and methods of treatment claims directed to our lead product candidate, STRO-004, and composition of matter, methods of treatment, and methods of making claims to aTF antibodies, exatecan linker-payloads and conjugates thereof. Any patents that issue from these patent applications will expire between June 2043 and October 2044, absent any patent term adjustments or extensions.

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STRO-006. We have approximately 3 patent families related to STRO-006, which include composition of matter and methods of treatment claims directed to our lead product candidate, STRO-006, and composition of matter, methods of treatment, and methods of making claims to aITGB6 antibodies, exatecan linker-payloads and conjugates thereof. Our issued patent, and any patents that may issue from our pending patent applications, related to our STRO-006 are expected to remain in force until 2046, absent any patent term adjustments or extensions.

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STRO-227. We have approximately 3 patent families related to STRO-227, which include composition of matter and methods of treatment claims directed to our lead product candidate, STRO-227, and composition of matter, methods of treatment, and methods of making claims to aPTK7 antibodies, exatecan linker-payloads and conjugates thereof. Our issued patent, and any patents that may issue from our pending patent applications, related to our STRO-227 are expected to remain in force until 2046, absent any patent term adjustments or extensions.

In addition, we have exclusively licensed the following patent portfolio from Stanford: 7 U.S. issued patents and 11 patents issued in ex-U.S. jurisdictions, including Europe, China, Canada, India, Australia, South Korea, Eurasia and Singapore. This patent portfolio includes claims relating to methods related to in vitro protein synthesis that we use in our XpressCF® platform and XpressCF+® platform when discovering, developing and manufacturing our product candidates.

Remaining patents in our patent portfolio licensed from Stanford are expected to expire between June 2026 and January 2028, absent any patent term adjustments or extensions.

As for the XpressCF® platform, XpressCF+® platform, product candidates and processes we develop and commercialize, in the normal course of business, we intend to pursue, where appropriate, patent protection or trade secret protection relating to compositions, methods of manufacture, assay methods, methods of use, treatment of indications, dosing and formulations. We may also pursue patent protection with respect to product development processes and technology.

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We continually assess and refine our intellectual property strategy as we develop new platform technologies and product candidates. To that end, we are prepared to file additional patent applications if our intellectual property strategy requires such filings, or where we seek to adapt to competition or seize business opportunities. Further, we are prepared to file patent applications, as we consider appropriate under the circumstances relating to the new technologies that we develop. In addition to filing and prosecuting patent applications in the United States, we often file counterpart patent applications in the European Union and in additional countries where we believe such foreign filing is likely to be beneficial, including but not limited to any or all of Australia, Brazil, Canada, China, Hong Kong, India, Israel, Japan, Mexico, New Zealand, Singapore, South Africa, South Korea, and Taiwan.

The term of individual patents depends upon the laws of the countries in which they are obtained. In most countries in which we file, the patent term is 20 years from the earliest date of filing of a non-provisional patent application. However, the term of United States patents may be extended for delays incurred due to compliance with the FDA requirements or by delays encountered during prosecution that are caused by the United States Patent and Trademark Office, or the USPTO. For example, the Hatch-Waxman Act permits a patent term extension for FDA-approved drugs 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 development and regulatory review. Patent 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 other jurisdictions to extend the term of a patent that covers an approved drug. In the future, if and when our biopharmaceutical product candidates receive FDA approval, we expect to apply for patent term extensions on patents covering those product candidates. We intend to seek patent term extensions to any of our issued patents in any jurisdiction where these are available; however, there is no guarantee that the applicable authorities, including the USPTO and FDA, will agree with our assessment of whether such extensions should be granted, and even if granted, the length of such extensions. Our currently issued patents will likely expire on dates ranging from 2033 to 2040, unless we receive patent term extension or patent term adjustment, or both. If patents are issued on our pending patent applications, the resulting patents are projected to expire on dates ranging from 2033 to 2045, unless we receive patent term extension or patent term adjustment, or both. However, the actual protection afforded by a patent varies on a product-by-product basis, from country-to-country, and depends upon many factors, including the type of patent, the scope of its coverage, the availability of regulatory-related extensions, the availability of legal remedies in a particular country and the validity and enforceability of the patent.

The patent positions of companies like ours are generally uncertain and involve complex legal and factual questions. No consistent policy regarding the scope of claims allowable in patents in the field of immunotherapy has emerged in the United States. The patent situation outside of the United States is even more uncertain. Changes in the patent laws and rules, either by legislation, judicial decisions, or regulatory interpretation in the United States and other countries may diminish our ability to protect our inventions and enforce our intellectual property rights, and more generally could affect the value of our intellectual property. In particular, our ability to stop third parties from making, using, selling, offering to sell, or importing any of our patented inventions, either directly or indirectly, will depend in part on our success in obtaining, defending, and enforcing patent claims that cover our technology, inventions, and improvements. With respect to both licensed and company-owned intellectual property, we cannot be sure that patents will be granted with respect to any of our pending patent applications or with respect to any patent applications filed by us in the future, nor can we be sure that any of our existing patents or any patents that may be granted to us in the future will be commercially useful in protecting our platforms and product candidates and the methods used to manufacture those platforms and product candidates. Moreover, even our issued patents do not guarantee us the right to practice our technology in relation to the commercialization of our platform’s product candidates. However, the area of patent and other intellectual property rights in biotechnology is an evolving one with many risks and uncertainties, and third parties may have blocking patents that could be used to prevent us from commercializing our patented XpressCF® platform, XpressCF+® platform, and product candidates and practicing our proprietary technology. Our issued patents and those that may issue in the future may be challenged, invalidated, or circumvented, which could limit our ability to stop competitors from marketing related platforms or product candidates or limit the length of the term of patent protection that we may have for our XpressCF® platform, XpressCF+® platform, and product candidates. In addition, the rights granted under any issued patents may not provide us with protection or competitive advantages against competitors with similar technology. Furthermore, our competitors may independently develop similar technologies. For these reasons, we may have competition for our XpressCF® platform, XpressCF+® platform, and product candidates. Moreover, because of the extensive time required for

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development, testing and regulatory review of a potential product, it is possible that, before any particular product candidate can be commercialized, any related patent may expire or remain in force for only a short period following commercialization, thereby reducing any advantage of the patent. For this and more comprehensive risks related to our proprietary technology, inventions, improvements, platforms, and product candidates, please see the section entitled “Risk Factors—Risks Related to Intellectual Property.”

In addition to patent protection, we also rely on trademark registration, trade secrets, know how, other proprietary information and continuing technological innovation to develop and maintain our competitive position. We seek to protect and maintain the confidentiality of proprietary information to protect aspects of our business that are not amenable to, or that we do not consider appropriate for, patent protection. Although we take steps to protect our confidential and proprietary information as trade secrets, including through contractual means with our employees, consultants, partners, and contractors, third parties may independently develop substantially equivalent proprietary information and techniques or otherwise gain access to our trade secrets or disclose our technology. Thus, we may not be able to meaningfully protect our trade secrets. It is our policy to require our employees, consultants, outside scientific collaborators, sponsored researchers and other advisors to execute confidentiality agreements upon the commencement of employment or consulting relationships with us. These agreements provide that all confidential information concerning our business or financial affairs developed or made known to the individual during the course of the individual’s relationship with us is to be kept confidential and not disclosed to third parties except in specific circumstances. In the case of employees, the agreements provide that all inventions conceived by the individual, and which are related to our current or planned business or research and development or made during normal working hours, on our premises or using our equipment or proprietary information, are our exclusive property. In many cases our confidentiality and other agreements with consultants, outside scientific collaborators, sponsored researchers and other advisors require them to assign or grant us licenses to inventions they invent as a result of the work or services they render under such agreements or grant us an option to negotiate a license to use such inventions.

Information Security

We seek to preserve the integrity and confidentiality of our proprietary technology and processes by maintaining physical security of our premises and physical and electronic security of our information technology systems. Our Infosec Governance Committee, comprising senior executives and facilities and information technology employees, and under the supervision of our Audit Committee of our Board of Directors, is responsible for designing, implementing, monitoring and improving the security of our confidential and/or proprietary information. We conduct regular audits of our information security systems, including our on-site and cloud-based information systems and strive to continuously improve the robustness of our security and information recovery systems in the event of, for example, a cyberattack or natural disaster that compromises our data integrity. As part of our security framework, we review publicly available cybersecurity assessments of our third-party partners and vendors to evaluate potential risks. In addition, we conduct regular training and testing of our employees to identify, and report cyberattacks, including phishing and other forms of social engineering. We also maintain a limited insurance policy against cyberattacks that may provide a measure of compensation in the event that we are harmed by an information security attack. Although we have confidence in these individuals, organizations, and systems, our security measures have been breached in the past and may again be breached in the future, and we may not have adequate remedies for any breach. To the extent that our employees, contractors, consultants, collaborators, and advisors use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions.

Government Regulation

Government authorities in the United States, at the federal, state and local level, and in other countries and jurisdictions extensively regulate, among other things, the research, development, testing, manufacture, quality control, approval, packaging, storage, recordkeeping, labeling, advertising, promotion, distribution, marketing, post-approval monitoring and reporting, and import and export of pharmaceutical products. The processes for obtaining regulatory approvals in the United States and in foreign countries and jurisdictions, along with subsequent compliance with applicable statutes and regulations and other regulatory authorities, require the expenditure of substantial time and financial resources.

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FDA Review and Approval Process

In the United States, pharmaceutical products are subject to extensive regulation by the FDA. The Federal Food, Drug, and Cosmetic Act, or the FDC Act, and other federal and state statutes and regulations, govern, among other things, the research, development, testing, manufacture, storage, recordkeeping, approval, labeling, promotion and marketing, distribution, post-approval monitoring and reporting, sampling, and import and export of pharmaceutical products. Biological products used for the prevention, treatment, or cure of a disease or condition of a human being are subject to regulation under the FDC Act, except the section of the FDC Act which governs the approval of new drug applications, or NDAs. Biological products are approved for marketing under provisions of the Public Health Service Act, or PHS Act, via a Biologics License Application, or BLA. However, the application process and requirements for approval of BLAs are very similar to those for NDAs, and biologics are associated with similar approval risks and costs as drugs. Failure to comply with applicable U.S. requirements may subject a company to a variety of administrative or judicial sanctions, such as clinical hold, FDA refusal to approve pending BLAs, warning or untitled letters, product recalls, product seizures, total or partial suspension of production or distribution, injunctions, fines, civil penalties, and criminal prosecution.

Biological product development for a new product or certain changes to an approved product in the United States typically involves preclinical laboratory and animal tests, the submission to the FDA of an IND, which must become effective before clinical testing may commence, and adequate and well-controlled clinical trials to establish the safety and effectiveness of the biologic for each indication for which FDA approval is sought. Satisfaction of FDA pre-market approval requirements typically takes many years and the actual time required may vary substantially based upon the type, complexity, and novelty of the product or disease.

Preclinical tests include laboratory evaluation of product chemistry, formulation, and toxicity, as well as animal trials to assess the characteristics and potential safety and efficacy of the product. The conduct of the preclinical tests must comply with federal regulations and requirements, including good laboratory practices. The results of preclinical testing are submitted to the FDA as part of an IND along with other information, including information about product chemistry, manufacturing and controls, and a proposed clinical trial protocol. Long-term preclinical tests, such as animal tests of reproductive toxicity and carcinogenicity, may continue after the IND is submitted. A 30-day waiting period after the submission of each IND is required prior to the commencement of clinical testing in humans. If the FDA has neither commented on nor questioned the IND and placed the IND on clinical hold within this 30-day period, the clinical trial proposed in the IND may begin. Clinical trials involve the administration of the investigational biologic to healthy volunteers or patients under the supervision of a qualified investigator. Clinical trials must be conducted: (i) in compliance with federal regulations; (ii) in compliance with good clinical practice, or GCP, an international standard meant to protect the rights and health of patients and to define the roles of clinical trial sponsors, administrators, and monitors; as well as (iii) under protocols detailing the objectives of the trial, the parameters to be used in monitoring safety, and the effectiveness criteria to be evaluated. Each protocol involving testing on U.S. patients and subsequent protocol amendments must be submitted to the FDA as part of the IND.

The FDA may order the temporary, or permanent, discontinuation of a clinical trial, in whole or in part, at any time, or impose other sanctions, if it believes that the clinical trial either is not being conducted in accordance with FDA requirements or presents an unacceptable risk to the clinical trial patients. The trial protocol and informed consent information for patients in clinical trials must also be submitted to an institutional review board, or IRB, for approval. An IRB may also require the clinical trial at the site to be halted, either temporarily or permanently, for failure to comply with the IRB’s requirements, or may impose other conditions.

Clinical trials to support BLAs for marketing approval are typically conducted in three sequential phases, but the phases may overlap. In Phase 1, the initial introduction of the biologic into healthy human subjects or patients, the product is tested to assess metabolism, pharmacokinetics, pharmacological actions, side effects associated with increasing doses, and, if possible, early evidence on effectiveness. In oncology clinical trials, efficacy endpoints are also often explored in Phase 1. Phase 2 usually involves trials in a limited patient population to determine the effectiveness of the drug or biologic for a particular indication, dosage tolerance, and optimum dosage, and to identify common adverse effects and safety risks. If a compound demonstrates evidence of effectiveness and an acceptable safety profile in Phase 2 evaluations, Phase 3 trials are undertaken to obtain the additional information about clinical efficacy and safety in a larger number of patients, typically at geographically dispersed clinical trial sites, to permit the FDA to evaluate the overall benefit-risk relationship of the drug or biologic and to provide adequate information for the labeling of the product. In some instances, trial phases may be truncated or combined into one or more combined-phase or adaptive design trials. In many cases, particularly for prevalent diseases, the FDA requires two adequate and well-controlled Phase 3 clinical trials to demonstrate the efficacy of the biologic. A single Phase 3 trial may be sufficient in many other conditions, particularly for rare disease therapies, when in conjunction with confirmatory evidence. A single adequate and well-controlled trial

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may also be sufficient, though it is less common, when the trial is a large multicenter trial demonstrating internal consistency and a statistically very persuasive finding of a clinically meaningful effect on mortality, irreversible morbidity or prevention of a disease with a potentially serious outcome and confirmation of the result in a second trial would be practically or ethically impossible.

The manufacturer of an investigational drug in a Phase 2 or 3 clinical trial for a serious or life-threatening disease is required to make available, such as by posting on its website, its policy on evaluating and responding to requests for expanded access.

After completion of the required clinical testing, a BLA is prepared and submitted to the FDA. FDA approval of the BLA is required before marketing of the product may begin in the United States. The BLA must include the results of all preclinical, clinical, and other testing and a compilation of data relating to the product’s pharmacology, chemistry, manufacture, and controls. The cost of preparing and submitting a BLA is substantial. The submission of most BLAs is additionally subject to a substantial application user fee, currently exceeding $4,682,000 for Fiscal Year 2026 for applications requiring clinical data. The applicant under an approved BLA is also subject to an annual program fee, currently exceeding $442,000 per prescription drug product for Fiscal Year 2026. These fees are typically increased annually. The FDA has 60 days from its receipt of a BLA to determine whether the application will be filed based on the agency’s threshold determination that it is sufficiently complete to permit substantive review. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission and may request additional information. In that event, the BLA must be resubmitted with the additional information. The resubmitted application also is subject to review before the FDA files it. Once the submission is filed, the FDA begins an in-depth review. The FDA has agreed to certain performance goals in the review of BLAs. Most such applications for standard review biologic products are reviewed within 10 months of the date the FDA files the BLA; most applications for priority review biologics are reviewed within six months of the date the FDA files the BLA. Priority review can be applied to a biologic that the FDA determines has the potential to treat a serious or life-threatening condition and, if approved, would be a significant improvement in safety or effectiveness compared to available therapies. The review process for both standard and priority review may be extended by the FDA for three additional months to consider information deemed by the FDA to be a major amendment to the BLA.

The FDA may also refer applications for novel biologic products, or biologic products that present difficult questions of safety or efficacy, to an advisory committee—typically a panel that includes clinicians and other experts—for review, evaluation, and a recommendation as to whether the application should be approved. The FDA is not bound by the recommendation of an advisory committee, but it generally follows such recommendations. Before approving a BLA, the FDA will typically inspect one or more clinical sites to assure compliance with GCP. Additionally, the FDA will inspect the facility or the facilities at which the biologic product is manufactured. The FDA will not approve the product unless compliance with current Good Manufacturing Practices, or cGMPs, is satisfactory and the BLA contains data that provide substantial evidence that the biologic is safe, pure, potent and effective in the indication studied.

After the FDA evaluates the BLA and the manufacturing facilities, it issues either an approval letter or a complete response letter. A complete response letter generally outlines the deficiencies in the submission and may require substantial additional testing, or information, in order for the FDA to reconsider the application. If, or when, those deficiencies have been addressed to the FDA’s satisfaction in a resubmission of the BLA, the FDA will issue an approval letter. The FDA has committed to reviewing such resubmissions in two or six months depending on the type of information included. An approval letter authorizes commercial marketing of the biologic with specific prescribing information for specific indications. As a condition of BLA approval, the FDA may require a risk evaluation and mitigation strategy, or REMS, to help ensure that the benefits of the biologic outweigh the potential risks. REMS can include medication guides, communication plans for healthcare professionals, and elements to assure safe use, or ETASU. ETASU can include, but are not limited to, special training or certification for prescribing or dispensing, dispensing only under certain circumstances, special monitoring, and the use of patient registries. The requirement for a REMS can materially affect the potential market and profitability of the product. Moreover, product approval may require substantial post-approval testing and surveillance to monitor the product’s safety or efficacy.

Once granted, product approvals may be withdrawn if compliance with regulatory standards is not maintained, or problems are identified following initial marketing. Changes to some of the conditions established in an approved application, including changes in indications, labeling, or manufacturing processes or facilities, require submission and FDA approval of a new BLA or BLA supplement before the change can be implemented. A BLA supplement for a new indication typically requires clinical data similar to that in the original application, and the FDA uses the same procedures and actions in reviewing BLA supplements as it does in reviewing BLAs.

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Expedited Programs

Under the fast track program, the FDA is authorized to facilitate the development, and expedite the review, of biologics that are intended for the treatment of a serious or life-threatening disease or condition for which there is no effective treatment and which demonstrate the potential to address unmet medical needs for the condition. The sponsor of a new biologic candidate may request that the FDA designate the candidate for a specific indication as a fast track biologic concurrent with, or after, the submission of the IND for the candidate. The FDA must determine if the biologic candidate qualifies for fast track designation within 60 days of receipt of the sponsor’s request. In addition to other benefits, such as the ability to engage in more frequent interactions with the FDA, the FDA may initiate review of sections of a fast track product’s BLA before the application is complete. This rolling review is available if the applicant provides, and the FDA approves, a schedule for the submission of the remaining information, the FDA determines after preliminary evaluation of clinical data submitted by the sponsor that the product may be effective, and the applicant pays applicable user fees. However, the FDA’s time period goal for reviewing an application does not begin until the last section of the BLA is submitted. Additionally, the fast track designation may be withdrawn by the FDA if the FDA believes that the designation is no longer supported by data emerging in the clinical trial process.

The FDA may designate a biologic candidate as a breakthrough therapy if it finds that the biologic candidate is intended, alone or in combination with one or more other product candidates or approved products, to treat a serious or life-threatening disease or condition, and preliminary clinical evidence indicates that the biologic candidate may demonstrate substantial improvement over existing therapies on one or more clinically significant

endpoints. For biologic candidates designated as breakthrough therapies, more frequent interaction and communication between the FDA and the sponsor can help to identify the most efficient path for clinical development. The receipt of a breakthrough therapy designation for a biologic candidate may not result in a faster development process, review or approval compared to product candidates considered for approval under conventional FDA procedures and, in any event, does not assure ultimate approval by the FDA. In addition, the FDA may later decide that a biologic candidate that has been designated as a breakthrough therapy no longer meets the conditions for designation.

Under the FDA’s accelerated approval regulations, the FDA may approve a biologic for a serious or life-threatening illness that addresses an unmet medical need based upon a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments.

In clinical trials, a surrogate endpoint is a measurement of laboratory or clinical signs of a disease or condition that substitutes for a direct measurement of how a patient feels, functions, or survives. Surrogate endpoints can often be measured more easily or more rapidly than clinical endpoints. A biologic 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 trials, or confirm a clinical benefit during post-marketing trials, will allow the FDA to withdraw the biologic from the market on an expedited basis. All promotional materials for biologic candidates approved under accelerated regulations are subject to prior review by the FDA. The FDA is authorized to require a post-approval study to be underway prior to approval or within a specified time period following approval. The FDA must also specify conditions of any required post-approval study, which may include milestones such as a target date of study completion. Sponsors must submit progress reports for required post-approval studies and any conditions required by the FDA not later than 180 days following approval and not less frequently than every 180 days thereafter until completion or termination of the study. The FDA can initiate an enforcement action for the failure to conduct with due diligence a required post-approval study, including a failure to meet any required conditions specified by the FDA or to submit timely reports.

Orphan Drug Designation

Under the Orphan Drug Act, the FDA may grant orphan drug designation to biological products intended to treat a rare disease or condition—generally a disease or condition that affects fewer than 200,000 individuals in the United States, or that affects more than 200,000 individuals in the United States and there is no reasonable expectation that the cost of developing and making a product available in the United States for such disease or condition will be recovered from sales of the product.

Orphan drug designation must be requested before submitting a BLA. After the FDA grants orphan drug designation, the generic identity or trade name, or a meaningful description, of the biological product and its

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potential orphan use are disclosed publicly by the FDA. Orphan drug designation does not convey any advantage in, or shorten the duration of, the regulatory review and approval process. The first BLA applicant to receive FDA approval for a product with particular principal molecular structural features to treat a particular disease with FDA orphan drug designation is entitled to a seven-year exclusive marketing period in the United States for that product for that indication. During the seven-year exclusivity period, the FDA may not approve any other applications to market the same drug for the same indication. In the case of a biological product, the same drug is a drug that contains the same principal molecular structural features, except if it is clinically superior. A product is clinically superior if it is safer, more effective or makes a major contribution to patient care. Orphan drug exclusivity does not prevent the FDA from approving a different drug or biological product for the same disease or condition, or the same biological product for a different disease or condition. Among the other benefits of orphan drug designation are tax credits for certain research and a waiver of the BLA user fee.

Disclosure of Clinical Trial Information

Sponsors of clinical trials of FDA-regulated products, including biological products, are required to register and disclose certain clinical trial information. Information related to the product, patient population, phase of investigation, trial sites and investigators, and other aspects of the clinical trial are then made public as part of the registration. Sponsors are also obligated to discuss the results of their clinical trials after completion. Disclosure of the results of these trials can be delayed in certain circumstances 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.

Pediatric Information

Under the Pediatric Research Equity Act, or PREA, BLAs or supplements to BLAs must contain data to assess the safety and effectiveness of the biological product for the claimed indications in all relevant pediatric subpopulations and to support dosing and administration for each pediatric subpopulation for which the biological product is safe and effective. The FDA may grant full or partial waivers, or deferrals, for submission of data. Unless otherwise required by regulation, PREA does not apply to any biological product for an indication for which orphan designation has been granted, except a product with a new active ingredient that is molecularly targeted cancer product intended for the treatment of an adult cancer and directed at a molecular target determined by FDA to be substantially relevant to the growth or progression of a pediatric cancer.

The Best Pharmaceuticals for Children Act, or BPCA, provides a six-month extension of any non-patent exclusivity for a biologic if certain conditions are met. Conditions for exclusivity include the FDA’s determination that information relating to the use of a new biologic in the pediatric population may produce health benefits in that population, FDA making a written request for pediatric studies, and the applicant agreeing to perform, and reporting on, the requested studies that fairly respond to the written request within the statutory timeframe. Applications under the BPCA are treated as priority applications, with all of the benefits that designation confers.

Additional Controls for Biologics

To help reduce the increased risk of the introduction of adventitious agents, the PHS Act emphasizes the importance of manufacturing controls for products whose attributes cannot be precisely defined. The PHS Act also provides authority to the FDA to immediately suspend licenses in situations where there exists a danger to public health, to prepare or procure products in the event of shortages and critical public health needs, and to authorize the creation and enforcement of regulations to prevent the introduction or spread of communicable diseases in the United States and between states.

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After a BLA is approved, the product may also be subject to official lot release as a condition of approval. As part of the manufacturing process, the manufacturer is required to perform certain tests on each lot of the product before it is released for distribution. If the product is subject to official release by the FDA, the manufacturer submits samples of each lot of products to the FDA together with a release protocol showing a summary of the history of manufacture of the lot and the results of all of the manufacturer’s tests performed on the lot. The FDA may also perform certain confirmatory tests on lots of some products, such as viral vaccines, before releasing the lots for distribution by the manufacturer. In addition, the FDA conducts laboratory research related to the regulatory standards on the safety, purity, potency, and effectiveness of biological products. As with drugs, after approval of biologics, manufacturers must address any safety issues that arise, are subject to recalls or a halt in manufacturing, and are subject to periodic inspection after approval.

Post-Approval Requirements

Once a BLA is approved, a product will be subject to certain post-approval requirements. For instance, the FDA closely regulates the post-approval marketing and promotion of biologics, including standards and regulations for direct-to-consumer advertising, off-label promotion, industry-sponsored scientific and educational activities and promotional activities involving the internet. Biologics may be marketed only for the approved indications and in accordance with the provisions of the approved labeling.

Adverse event reporting and submission of periodic reports is required following FDA approval of a BLA. The FDA also may require post-marketing testing, known as Phase 4 testing, REMS, and surveillance to monitor the effects of an approved product, or the FDA may place conditions on an approval that could restrict the distribution or use of the product. In addition, quality control, biological product manufacture, packaging, and labeling procedures must continue to conform to cGMPs after approval. Biologic manufacturers and certain of their subcontractors are required to register their establishments with the FDA and certain state agencies. Registration with the FDA subjects entities to periodic unannounced inspections by the FDA, during which the agency inspects manufacturing facilities to assess compliance with cGMPs. Accordingly, manufacturers must continue to expend time, money, and effort in the areas of production and quality-control to maintain compliance with cGMPs. Regulatory authorities may withdraw product approvals or request product recalls if a company fails to comply with regulatory standards, if it encounters problems following initial marketing, or if previously unrecognized problems are subsequently discovered.

FDA Regulation of Companion Diagnostics

A biologic product may rely upon an in vitro companion diagnostic for use in selecting the patients that will respond to a therapy. If an in vitro diagnostic is essential to the safe and effective use of the therapeutic product, then the FDA generally will require approval, authorization or clearance of the diagnostic at the same time that FDA approves the therapeutic product.

Under the FDC Act, in vitro diagnostics, including companion diagnostics, are regulated as medical devices. The FDC Act classifies medical devices, including in vitro diagnostics, into one of three categories based on the risks associated with the device and the level of control necessary to provide reasonable assurance of safety and effectiveness. Class I devices are deemed to be low risk and are subject to the fewest regulatory controls. Class III devices are generally the highest risk devices and are subject to the highest level of regulatory control to provide reasonable assurance of the device’s safety and effectiveness. While most Class I and some Class II devices can be marketed without prior FDA authorization, most medical devices can be legally sold within the U.S. only if the FDA has: (i) approved a PMA application prior to marketing, generally applicable to Class III devices; or (ii) cleared the device in response to a premarket notification, or 510(k) submission, generally applicable to Class I and II devices. Devices of a new type that FDA has not previously classified based on risk are automatically classified into Class III regardless of the level of risk they pose, but the FDA may classify a low- to moderate-risk device not previously classified into Class I or II through the de novo classification process.

Pursuing FDA approval of an in vitro companion diagnostic has historically required a pre-market approval, or PMA, for a diagnostic to identify patient populations suitable for a cancer therapy. The review of these in vitro companion diagnostics involves coordination of review by the FDA’s Center for Biologics Evaluation and Research and by the FDA’s Center for Devices and Radiological Health. Approval of a companion diagnostic is generally required at the time of new drug approval.

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The PMA process, including the gathering of clinical and nonclinical data and the submission to and review by the FDA, can take several years or longer. The applicant must prepare and provide the FDA with reasonable assurance of the device’s safety and effectiveness, including information about the device and its components regarding, among other things, device design, manufacturing and labeling. PMA applications are subject to an application fee, which exceeds $579,000 for most PMAs for Fiscal Year 2026. In addition, PMAs for devices must generally include the results from extensive preclinical and adequate and well-controlled clinical trials to establish the safety and effectiveness of the device for each indication for which FDA approval is sought. In particular, for a diagnostic, the applicant must demonstrate that the diagnostic produces reproducible results between multiple users at multiple laboratories. As part of the PMA review, the FDA will typically inspect the manufacturer’s facilities for compliance with the Quality Management System Regulation, or QMSR, which imposes elaborate testing, control, documentation and other quality assurance requirements.

PMA approval is not guaranteed, and the FDA may ultimately respond to a PMA submission with a not approvable determination based on deficiencies in the application and require additional clinical trial or other data that may be expensive and time consuming to generate and that can substantially delay or prevent approval. If the FDA concludes that the applicable criteria have been met, the FDA will issue a PMA for the approved indications, which can be more limited than those originally sought by the applicant. The PMA can include post-approval conditions that the FDA believes necessary to ensure the safety and effectiveness of the device, including, among other things, restrictions on labeling, promotion, sale and distribution.

In 2024, CDRH announced that it intended to reclassify most high-risk in vitro diagnostic products from Class III to Class II medical devices and stated that it expected most future companion diagnostics would be regulated as Class II devices. Reclassification would allow companion diagnostic developers to seek marketing authorization through the FDA’s 510(k) or de novo classification pathways rather than the more costly and time-consuming PMA pathway. Since that time, CDRH has taken steps to begin the reclassification process for certain companion diagnostic products, such as in situ hybridization test systems and nucleic acid-based test systems intended for use with a corresponding approved oncology therapeutic product. However, these proposed reclassifications are not yet final and commercializing any such tests requires PMA approval until the reclassification is final.

The 510(k) and de novo submission processes are less burdensome than the PMA approval process. To obtain 510(k) clearance, a manufacturer must submit a premarket notification demonstrating that the proposed device is substantially equivalent to a legally marketed device, referred to as the predicate device. To be substantially equivalent, the proposed device must have the same intended use as the predicate device, and either have the same technological characteristics as the predicate device or have different technological characteristics and be shown to be equally safe and effective and not raise different questions of safety and effectiveness than the predicate device. The de novo classification process is used when there is no predicate device. In a de novo submission, the sponsor must demonstrate that the proposed device is of low or moderate risk and the benefits outweigh the risks. The type of data included in a de novo request is similar to the type of data included in a 510(k), although a larger proportion of de novo submissions require clinical data as compared to 510(k)s. The review time for a de novo request is longer as compared to the 510(k) process, and the outcome for de novo requests is more uncertain.

After a device is placed on the market, it remains subject to significant regulatory requirements. Medical devices may be marketed only for the uses and indications for which they are cleared, authorized or approved. A modification that could significantly affect a device’s safety or effectiveness, or that would constitute a major change in its intended use, requires a new 510(k) clearance, de novo authorization, or could require a PMA approval. Device manufacturers must also register with FDA and list their devices. A medical device manufacturer’s manufacturing processes are required to comply with the applicable portions of the QMSR, which cover the methods and documentation of the design, testing, production, processes, controls, quality assurance, labeling, packaging and shipping of medical devices. Domestic facility records and manufacturing processes are subject to periodic inspections by the FDA.

Failure to comply with applicable regulatory requirements can result in enforcement action by the FDA, which may include any of the following sanctions: warning or untitled letters, fines, injunctions, civil or criminal penalties, recall or seizure of current or future products, operating restrictions, partial suspension or total shutdown of production, denial of submissions for new products, or withdrawal of approvals, authorizations or clearances.

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Other Healthcare Laws

In addition to FDA restrictions on marketing of pharmaceutical products, several other types of state and federal laws have been applied to restrict certain general business and marketing practices in the pharmaceutical industry in recent years. These laws include anti-kickback statutes, false claims statutes and other healthcare laws and regulations.

The federal Anti-Kickback Statute prohibits, among other things, knowingly and willfully offering, paying, soliciting or receiving remuneration to induce, or in return for, purchasing, leasing, ordering or arranging for the purchase, lease or order of any healthcare item or service reimbursable under Medicare, Medicaid, or other federally financed healthcare programs. The Patient Protection and Affordable Care Act as amended by the Health Care and Education Reconciliation Act, collectively, the ACA, amended the intent element of the federal statute so that a person or entity no longer needs to have actual knowledge of the statute or specific intent to violate it in order to commit a violation. This statute has been interpreted to apply to arrangements between pharmaceutical manufacturers on the one hand and prescribers, purchasers and formulary managers on the other. Although there are a number of statutory exceptions and regulatory safe harbors protecting certain common activities from prosecution or other regulatory sanctions, the exceptions and safe harbors are drawn narrowly, and practices that involve remuneration intended to induce prescribing, purchases or recommendations may be subject to scrutiny if they do not qualify for an exception or safe harbor.

Federal civil and criminal false claims laws, including the federal civil False Claims Act, prohibit any person or entity from knowingly presenting, or causing to be presented, a false claim for payment to the federal government, or knowingly making, or causing to be made, a false statement to have a false claim paid. This includes claims made to programs where the federal government reimburses, such as Medicaid, as well as programs where the federal government is a direct purchaser, such as when it purchases off the Federal Supply Schedule. Several pharmaceutical and other healthcare companies have been prosecuted under these laws for allegedly inflating drug prices they report to pricing services, which in turn were used by the government to set Medicare and Medicaid reimbursement rates, and for allegedly providing free product to customers with the expectation that the customers would bill federal programs for the product. In addition, certain marketing practices, including off-label promotion, may also violate false claims laws. Additionally, the ACA amended the federal Anti-Kickback Statute such that a violation of that statute can serve as a basis for liability under the federal False Claims Act. The majority of states also have statutes or regulations similar to the federal Anti-Kickback Statute and False Claims Act, which apply to items and services reimbursed under Medicaid and other state programs, or, in several states, apply regardless of the payor.

Other federal statutes pertaining to healthcare fraud and abuse include the civil monetary penalties statute, which prohibits, among other things, the offer or payment of remuneration to a Medicaid or Medicare beneficiary that the offeror or payor knows or should know is likely to influence the beneficiary to order a receive a reimbursable item or service from a particular supplier, and the additional federal criminal statutes created by the Health Insurance Portability and Accountability Act of 1996, or HIPAA, which prohibits, among other things, knowingly and willfully executing or attempting to execute a scheme to defraud any healthcare benefit program or obtain by means of false or fraudulent pretenses, representations or promises, any money or property owned by or under the control of any healthcare benefit program in connection with the delivery of or payment for healthcare benefits, items or services.

In addition, HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act of 2009, or HITECH, imposes obligations on certain healthcare providers, health plans, and healthcare clearinghouses, known as covered entities, as well as their business associates that perform certain services involving the storage, use or disclosure of individually identifiable health information, including mandatory contractual terms, with respect to safeguarding the privacy, security, and transmission of individually identifiable health information, and require notification to affected individuals and regulatory authorities of certain breaches of security of individually identifiable health information. In addition, many state laws govern the privacy and security of health information in certain circumstances, many of which differ from each other in significant ways and may not have the same effect, and often are not preempted by HIPAA. For example, the California Consumer Privacy Act, or CCPA, which went into effect on January 1, 2020, creates new data privacy obligations for covered companies and provides new privacy rights to California residents. On January 1, 2023, the California Privacy Rights Act, or CPRA, which substantially amends the CCPA, went into effect. The CCPA and CPRA provide for unlimited civil penalties for violations, as well as a private right of action for data breaches that is expected to

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increase data breach litigation. Virginia’s Consumer Data Protection Act, which took effect on January 1, 2023, requires businesses subject to the legislation to conduct data protection assessments in certain circumstances and requires opt-in consent from consumers to acquire and process their sensitive personal information, which includes information revealing a consumer’s physical and mental health diagnosis and genetic and biometric information that can identify a consumer. Colorado enacted the Colorado Privacy Act, and Connecticut enacted the Connecticut Data Privacy Act, each of which took effect on July 1, 2023, and Utah enacted the Consumer Privacy Act, which became effective on December 31, 2023, and each of these laws may increase the complexity, variation in requirements, restrictions, and potential legal risks, and could require increased compliance costs and changes in business practices and policies. Other states have also enacted, proposed, or are considering proposing, data privacy laws, which could further complicate compliance efforts, increase our potential liability and adversely affect our business.

Further, pursuant to the ACA, the Centers for Medicare & Medicaid Services, or CMS, has issued a final rule that requires manufacturers of prescription drugs to collect and report information on certain payments or transfers of value to physicians, physician assistants, certain types of advanced practice nurses and teaching hospitals, as well as investment interests held by physicians and their immediate family members. The reports must be submitted on an annual basis and the reported data are posted in searchable form on a public website on an annual basis. Failure to submit required information may result in civil monetary penalties.

In addition, several states now require prescription drug companies to report certain expenses relating to the marketing and promotion of drug products and to report gifts and payments to individual healthcare practitioners in these states. Other states prohibit various marketing-related activities, such as the provision of certain kinds of gifts or meals. Still other states require the posting of information relating to clinical studies and their outcomes. A growing number of states require the reporting of certain pricing information, including information pertaining to and justifying price increases and introductory prices for new drugs. In addition, certain states require pharmaceutical companies to implement compliance programs and/or marketing codes. Additional states and local jurisdictions, such as Nevada, Connecticut, the City of Chicago and the District of Columbia, require pharmaceutical sales representatives to be registered, licensed and/or meet continuing education requirements. Certain states and local jurisdictions also require the registration of pharmaceutical sales representatives. Compliance with these laws is difficult and time consuming, and companies that do not comply with these state laws face civil penalties.

Efforts to ensure that business arrangements with third parties comply with applicable healthcare laws and regulations involve substantial costs. If a drug company’s operations are found to be in violation of any such requirements, it may be subject to significant penalties, including civil, criminal and administrative penalties, damages, fines, disgorgement, imprisonment, the curtailment or restructuring of its operations, loss of eligibility to obtain approvals from the FDA, exclusion from participation in government contracting, healthcare reimbursement or other government programs, including Medicare and Medicaid, integrity oversight and reporting obligations and reputational harm. Although effective compliance programs can mitigate the risk of investigation and prosecution for violations of these laws, these risks cannot be entirely eliminated. Any action for an alleged or suspected violation can cause a drug company to incur significant legal expenses and divert management’s attention from the operation of the business, even if such action is successfully defended.

Coverage, Pricing and Reimbursement

The regulations that govern coverage, pricing and reimbursement for new pharmaceutical products vary widely from country to country. Some countries require approval of the sale price of a pharmaceutical product before it can be marketed. In many countries, the pricing review period begins after marketing approval is granted. In some foreign markets, prescription pharmaceutical pricing remains subject to continuing governmental control even after initial approval is granted. As a result, a pharmaceutical company can obtain regulatory approval for a product in a particular country, but then be subject to price regulations that delay commercial launch of that product.

A pharmaceutical company’s ability to commercialize any products successfully will also depend in part on the extent to which coverage and adequate reimbursement for these products and related treatments will be available from government authorities, private health insurers and other organizations. The process for determining whether a third-party payor will provide coverage for a product may be separate from the process for setting the price of a product or for establishing the reimbursement rate that such a payor will pay for the product. Even if one

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or more products are successfully brought to the market, these products may not be considered cost-effective, and the amount reimbursed for such products may be insufficient to allow them to be sold on a competitive basis. Increasingly, third-party payors who reimburse patients or healthcare providers, such as government and private insurance plans, are requiring that pharmaceutical companies provide them with predetermined discounts from list prices and are seeking to reduce the prices charged or the amounts reimbursed for biopharmaceutical products.

Moreover, one payor’s determination to provide coverage for a product does not assure that an adequate reimbursement rate will be approved, or that other payors will also provide coverage for the product. Further, no uniform policy for coverage and reimbursement exists in the United States. Private payors often rely upon Medicare coverage policy and payment limitations in setting their own reimbursement rates, but also have their own methods and approval processes apart from Medicare determinations. Therefore, coverage and reimbursement can differ significantly from payor to payor as well as from state to state. Consequently, the coverage determination process is often a time-consuming and costly process that must be played out across many jurisdictions and different entities. Further, a payor’s decision to provide coverage for a drug product does not imply that an adequate reimbursement rate will be approved.

Significant delays can occur in obtaining reimbursement for newly approved pharmaceutical products, and coverage may be more limited than the purposes for which product is approved by the FDA or similar foreign regulatory authorities. Interim reimbursement levels, if applicable, may also be insufficient to cover a pharmaceutical company’s costs and may not be made permanent. Moreover, eligibility for reimbursement does not imply that any pharmaceutical product will be reimbursed in all cases or at a rate that covers a pharmaceutical company’s costs, including research, development, manufacture, sale and distribution. In addition, coverage policies and third-party reimbursement rates may change at any time.

Healthcare Reform

Healthcare reforms that have been adopted, and that may be adopted in the future, could result in further reductions in coverage and levels of reimbursement for pharmaceutical products, increases in rebates payable under U.S. government rebate programs and additional downward pressure on pharmaceutical product prices. Several healthcare reform proposals culminated in the enactment of Inflation Reduction Act, or IRA, which among other things, requires the Department of Health and Human Services, or HHS, to directly negotiate the selling price of a statutorily specified number of drugs and biologics each year that CMS reimburses under Medicare Part B and Part D. The negotiated price may not exceed a statutory ceiling price. Only high-expenditure single-source biologics that have been approved for at least 11 years (7 years for single-source drugs) are eligible to be selected by CMS for negotiation, with the negotiated price taking effect two years after the selection year. For 2026, the first year in which negotiated prices become effective, CMS selected 10 high-cost Medicare Part D products in 2023, negotiations began in 2024, and the negotiated maximum fair price for each product has been announced. In addition, CMS has selected and announced the negotiated maximum fair price for 15 additional Medicare Part D drugs, which will become effective in 2027. For 2028, CMS has selected an additional 15 drugs, comprised of drugs covered under Medicare Part D and, for the first time, drugs payable under Medicare Part B. For 2029 and subsequent years, 20 Part B or Part D drugs will be selected. Currently, a drug or biological product that has an orphan drug designation for only one rare disease or condition will be excluded from the IRA’s price negotiation requirements, but will lose that exclusion if it receives designations for more than one rare disease or condition, or if it is approved for an indication that is not within that single designated rare disease or condition, unless such additional designation or such disqualifying approvals are withdrawn by the time CMS evaluates the drug for selection for negotiation. However, as a result of a statutory amendment enacted in July 2025, beginning with the 2028 negotiated price applicability year, a drug may be designated for more than one rare disease or condition and still be excluded from price negotiation, as long as the only approved indications are for such rare diseases or conditions. The IRA also imposes rebates on Medicare Part D and Part B drugs whose prices have increased at a rate greater than the rate of inflation, and in November 2024, CMS finalized regulations for the Medicare Part B and Part D inflation rebates. The IRA permits the Secretary of HHS to implement many of these provisions through guidance, as opposed to regulation, for the initial years. Manufacturers that fail to comply with the IRA may be subject to various penalties, including civil monetary penalties. These provisions have been and may continue to be subject to legal challenges. For example, the provisions related to the negotiation of selling prices of high-expenditure single-source drugs and biologics have been challenged in multiple lawsuits brought by pharmaceutical manufacturers. Thus, while it is unclear how the IRA will be implemented, it will likely have a significant impact on the biopharmaceutical industry and the pricing of prescription drug products.

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Recently there has been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in recent Executive Orders, 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 methodologies for drug products. For example, on May 12, 2025, President Trump issued an Executive Order that, among other things, required HHS, within 30 days, to establish and communicate to drug manufacturers most-favored-nation, or MFN, price targets designed to bring drug prices for American patients in line with those in comparably developed nations. If significant progress towards MFN pricing is not achieved, the Executive Order requires HHS to propose a rulemaking to implement MFN pricing. In July 2025, President Trump sent letters to certain pharmaceutical companies demanding that these companies extend MFN pricing to Medicaid and newly launched drugs as well as move to direct-to-consumer models priced at MFN pricing, and soliciting binding commitments by September 29, 2025. Since this time, multiple drug manufacturers have announced plans to, for certain of their drugs, lower prices to reflect similar pricing around the world, and to sell these reduced-price drugs on a direct-to-consumer purchasing platform developed by the federal government; however, it is not known what results will occur to the extent the recipients of these letters do not reduce their U.S. prices. Recently, on December 23, 2025, CMS issued proposed regulations to establish, under the Center for Medicare and Medicaid Innovation, two mandatory MFN pricing demonstration models under Medicare Part B and Part D. If these rules or other MFN pricing rules are finalized, they are likely to mandate reduced prices of at least some drugs in the United States, if they are also sold in comparator countries. Even if a pharmaceutical company does not market drugs in such countries, it may be indirectly affected if its drugs compete with drugs that were reduced by MFN pricing.

At the state level, legislatures have increasingly passed legislation and implemented regulations designed to control pharmaceutical 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.

Human Capital Resources

As of December 31, 2025, we had 137 full-time employees. Of these employees, 44 have an M.D. or a Ph.D. None of our employees are represented by a labor union or covered by collective bargaining agreements, and we believe our relationship with our employees is good. However, in March 2025 and again in September 2025, we executed significant reductions in workforce, which may negatively impact our relationship with our employees going forward.

We recognize that attracting, motivating, and retaining talent at all levels is vital to continuing our success. We invest in our employees in many ways, including through high-quality benefits and various health and wellness initiatives and offer competitive compensation packages (base salary and incentive plans), ensuring fairness in internal compensation practices. The principal purposes of our incentive plans (bonus and equity) are to provide retention incentives that align with the long-term interests of our stakeholders and stockholders.

To further engage and incentivize our workforce, we also offer a range of opportunities to support professional development and growth. We support ongoing education by providing an appropriate level of reimbursement for courses which are related to an individual’s current or future position, we support our scientific team through encouraging their in-person and/or virtual attendance at conferences and symposia which further their development and we have a robust internal transfer practice to engage our current talent in growth opportunities within and outside of their functional areas. We embarked upon a Company-wide leadership development program which offered the opportunity for every employee to continue to build upon their learning. For our talent pipeline assessment and development, we work closely with individual scientific and business functional leaders to identify our high-performing and high-potential employees, by conducting a company-wide talent assessment and calibration. This assessment is completed annually to ensure we tie together our incentives, development, and recognition to retain and attract the people we need to drive our success.

We provide our team with ongoing resources aimed at both mental and physical health. We work closely with our Employee Assistance Plan which provides important mental health services and resources. We have a health and wellness initiative which encourages healthy behaviors aimed at creating positive life-long habits. We have a culture of collaboration and collaborative principles which we intentionally foster. Our initiatives on Diversity, Equity, Inclusion and Belonging aim to learn, listen and act in support of these principles. We are actively involved

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in our community through, among other things, mentoring underserved communities and supporting the philanthropic interests of our employees and patients.

We also recognize that maintaining continuity of management in the event of the departure of one or more of our senior executives is critical to the continued success of the organization. To this end, we have prepared a formal written succession plan for our senior executives and to provide guidance for the next generation of our leaders to ensure an orderly and smooth transition in the event of an executive departure. While senior management is primarily responsible for developing our succession plan, our Nominating and Corporate Governance Committee of our Board of Directors (with respect to the CEO) and Compensation Committee of our Board of Directors (with respect to other executives) oversee and guide our process and thinking.

Corporate Information

We were incorporated under the laws of the State of Delaware in April 2003 under the name Fundamental Applied Biology, Inc. We subsequently changed our name to Sutro Biopharma, Inc. Our principal executive offices are located at 111 Oyster Point Boulevard, South San Francisco, California 94080, and our telephone number is (650) 881- 6500. Our website address is www.sutrobio.com. The information contained on, or that can be accessed through, our website is not part of, and is not incorporated by reference into, this report.

Available Information

We file annual, quarterly and current reports, proxy statements and other documents with the Securities and Exchange Commission, or SEC, under the Securities Exchange Act of 1934, as amended, or Exchange Act. The SEC maintains an Internet website that contains reports, proxy and information statements, and other information regarding issuers, including us, that file electronically with the SEC. The public can obtain any documents that we file with the SEC at www.sec.gov. Copies of each of our filings with the SEC can also be viewed and downloaded free of charge at our website, ir.sutrobio.com, after the reports and amendments are electronically filed with or furnished to the SEC.

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