NASDAQ: VIR

We are developing therapeutic candidates in HIV cure and multiple solid tumors. Our HIV broadly neutralizing antibodies (bnAbs) are being developed as a potential long-acting treatment or cure in combination with existing or investigational regimens. We have also made available for external partnerships our next-generation preclinical influenza A and B antibodies and antibody drug conjugates (ADCs), along with our next generation coronavirus (COVID) monoclonal antibodies.

We are advancing multiple undisclosed PRO-XTEN® dual-masked TCEs targeting clinically validated targets with potential applications across a variety of solid tumors. These preclinical candidates leverage the PRO-XTEN® masking technology with novel TCE fragments discovered and engineered using our antibody discovery platform.

These research and development efforts are driven by Vir Bio’s discovery engine, comprised of our exceptional protein engineering and antibody discovery expertise and our two core technology platforms — our proprietary dAIsY™ (data, AI structure and antibodY) platform utilizing artificial intelligence and machine learning (collectively referred to as AI) for antibody optimization, and the exclusive PRO-XTEN® (a trademark of Amunix Pharmaceuticals, Inc., a Sanofi company) masking platform, which we in-licensed from Sanofi for worldwide rights in oncology and infectious diseases. The PRO-XTEN® platform allows for the development of potentially best-in-class TCEs with improved safety and efficacy profiles across multiple therapeutic areas. The dAIsY™ and PRO-XTEN® platforms, individually and in combination, enable us to modulate the immune system in innovative ways, harnessing its power to combat viruses and fight cancer.

We have an industry-leading management team and board of directors with significant immunology, infectious diseases and oncology experience, including a proven track record of progressing product candidates from early-stage research through clinical development, and worldwide regulatory approval and commercialization experience. Given the global impact of infectious diseases and cancer, we are committed to developing transformative therapies that can make a meaningful difference in the lives of people living with these serious diseases.

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Our Research and Development Pipeline

At Vir Bio, we are advancing our mission of powering the immune system with innovative medicines to transform lives, with the goal of driving better outcomes for patients in areas of high unmet medical need, such as infectious diseases and cancer. We use our world-class capabilities in antibody discovery and engineering, coupled with our proprietary AI engine dAIsY™ system, and the PRO-XTEN® masking platform, to quickly and effectively discover and optimize potential new medicines.

We have built a strong foundation based on cutting-edge core scientific capabilities and a world-class team of experts who bring deep knowledge and experience to our R&D efforts. This has enabled us to make significant strides in developing treatments for infectious diseases and to strategically expand our approach to address critical oncology indications with limited treatment options. Our pipeline includes multiple candidates in clinical development for diseases with significant unmet medical need, which is categorized by disease area in the chart below.

1: Masked TCEs licensed from Sanofi

2 In collaboration with the Gates Foundation

ARPIs: androgen receptor pathway inhibitors; EGFR: epidermal growth factor receptor; HER2: human epidermal growth factor receptor 2; HIV: human immunodeficiency virus; PSMA: prostate-specific membrane antigen; siRNA: small interfering RNA; TCE: T-cell engager

Tobevibart incorporates Xencor’s XtendTM and other Fc technologies.

Norgine holds exclusive license for the commercial rights to the combination of tobevibart and elebsiran in Europe, Australia and New Zealand

Brii Bioscience retains rights to the combination of tobevibart and elebsiran in the Greater China Territory (People’s Republic of China, Hong Kong, Taiwan and Macau)

Infectious Diseases

Tobevibart

Molecular Characteristics and Preclinical Data. Tobevibart is an investigational neutralizing monoclonal antibody (mAb) that has been engineered for immune engagement and targets a conserved region on the hepatitis B surface antigen (HBsAg), a protein which is required for the HDV viral life cycle. Tobevibart specifically targets the antigenic loop (AGL) on HBsAg. The AGL helps HBV bind to hepatocytes and subsequently infect these cells. By binding to the AGL, tobevibart is designed to prevent viral entry, which prevents the spread of HDV to uninfected hepatocytes. It has been engineered to neutralize strains from all 10 HBV genotypes. Tobevibart, through a process called opsonization, also helps remove HBV virions and sub-viral particles (SVPs) from the blood.

Tobevibart was identified using our proprietary antibody discovery platform. Tobevibart’s proprietary fragment crystallizable (Fc) engineering enhances its ability to engage immune cells, promoting the removal of antibody-virion complexes. Tobevibart also incorporates Xencor’s Xtend™ neonatal Fc receptor technology, which extends its half-life.

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Tobevibart has the potential to activate the immune system to fight the virus via three different processes. First, due to specialized mutations in the Fc domain, tobevibart has the potential to act as a T-cell vaccine, inducing the production of protective T-cells and promoting immunity. This is based on a mechanism by which tobevibart could capture virions and SVPs, deliver them to dendritic cells and instruct these cells to mature and stimulate T-cells that can then eliminate HBV- infected hepatocytes. Second, tobevibart has the potential to act via antibody-dependent cell cytotoxicity (ADCC). In this process, by binding to HBsAg at the cell surface, tobevibart recruits natural killer cells to eliminate infected hepatocytes. The Fc domain of tobevibart has been engineered to promote ADCC. Third, when large quantities of HBV proteins are released into the blood, especially HBsAg, they can be immunosuppressive. Tobevibart has the potential to activate the immune system by reducing the amount of HBsAg in the blood, decreasing the ability of HBV to suppress the immune system and further enabling the natural immune response to the virus.

Elebsiran

Molecular Characteristics and Preclinical Data. Elebsiran is an investigational HBV-targeted small interfering RNA (siRNA) that reduces HBsAg. Elebsiran targets a conserved sequence of HBV that allows for predicted activity against 99.7% of the strains of HBV, including all 10 HBV genotypes. Because this conserved sequence falls within a specific region of the X gene of HBV that exists within all four HBV RNA transcripts, elebsiran is designed to degrade each transcript, and consequently decrease the expression of all proteins produced by the virus: X, polymerase, S, and core.

Once inside the infected cell, DNA from the HBV virus can become integrated into human DNA as integrated DNA (intDNA). Because elebsiran targets a region of HBV that is conserved in the large majority of HBV intDNA, this single siRNA is predicted to be able to prevent the production of HBV proteins derived from intDNA, as well as the production of all other HBV proteins from covalently closed circular DNA (cccDNA).

There are at least two potential mechanisms by which the large amount of HBV protein that is transcribed in liver cells can suppress the immune system. The first mechanism is T-cell tolerance and exhaustion by the presentation of intracellular HBV antigens on hepatocytes. The second is the large quantities of HBV proteins that are released into the blood, especially HBsAg, which may also be immunosuppressive. By directly reducing the amount of HBV proteins made, elebsiran has the potential to decrease the ability of HBV to suppress the immune system and enable the natural immune response to the virus. In mice models, siRNAs that are able to reduce HBsAg expression can transform an otherwise ineffective therapeutic HBV vaccine into one that can functionally cure the mice of HBV, suggesting that HBsAg suppression has the ability to enhance the immune response against HBV.

We believe that elebsiran is the only HBV-targeting siRNA currently in development that includes enhanced stabilization chemistry (ESC+) technology and preclinical modeling. Initial clinical data suggest this technology may be able to enhance the safety profile of elebsiran.

Simplified mechanism of action representation of tobevibart and elebsiran.

cccDNA: covalently closed circular DNA, HBsAg: hepatitis B virus surface antigen, HBV: hepatitis B virus, HDV: hepatitis D virus, Int: integrated, NRTI: nucleoside/nucleotide reverse transcriptase inhibitor, RNP: ribonucleoprotein, SVP: subviral particle

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CHD

CHD is a progressive liver disease caused by HDV, which requires HBV for its replication. This means that HDV infection cannot occur in the absence of HBV. HDV-HBV coinfection is the most severe form of chronic viral hepatitis. HDV, recently classified as carcinogenic by the International Agency for Research on Cancer, increases the risk of liver cancer and accelerates progression to cirrhosis and liver failure, which often occurs within five years of infection. There is no approved CHD treatment in the U.S., and options are limited in the European Union and globally.

Vir Bio is working to develop a chronic suppressive therapy to help address this significant unmet medical need, based on a combination of our investigational antibody, tobevibart, and a siRNA, elebsiran.

Tobevibart + elebsiran for CHD

SOLSTICE is a Phase 2 study to evaluate the safety, tolerability, and efficacy of tobevibart, alone or in combination with elebsiran, in people with CHD. This Phase 2 study is a multi-center, open-label, randomized study. Primary endpoints include proportion of participants with protocol defined virologic endpoint (defined as HDV RNA equal or greater than 2 log10 decrease from baseline or below limit of detection) up to Week 24, alanine aminotransferase (ALT) normalization (defined as ALT below upper limit of normal) up to Week 24, and treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs) up to 118 weeks. Secondary endpoints include proportion of participants with undetectable HDV RNA at different timepoints up to 192 weeks. Clinical trial participants have been randomized to receive tobevibart 300 mg monotherapy every two weeks (n=33) or a combination of tobevibart 300 mg and elebsiran 200 mg every four weeks (combination de novo arm, n=32). In addition, the participants from previous tobevibart or elebsiran monotherapy cohorts could rollover to receive the combination of tobevibart 300 mg and elebsiran 200 mg every four weeks (combination rollover, n=13). 48-week data from the ongoing clinical trial was presented in an oral session at the American Association for the Study of Liver Diseases (AASLD) The Liver Meeting®, in Washington, D.C., in November 2025 and simultaneously published in the New England Journal of Medicine.

Additional data was later presented at the 44ᵗʰ Annual J.P. Morgan Healthcare Conference in January 2026. These data demonstrate that undetectable hepatitis delta virus RNA (HDV RNA Target Not Detected, TND) was achieved and maintained by 77% (24/31) of participants receiving the combination of tobevibart and elebsiran at Week 72, and this rate increased to 88% (21/24) in the subset of participants evaluated through Week 96. By contrast, HDV RNA TND was achieved by 53% (17/32) of participants receiving tobevibart antibody monotherapy at Week 72 and 46% (11/24) in the subset of participants evaluated through Week 96. Additionally, approximately 90% of participants receiving the combination therapy achieved reduction in HBsAg to values <10 IU/mL by Week 24 and kept that response through Week 72 and (for the subset of patients evaluable) Week 96, compared to approximately 20% of participants receiving antibody monotherapy at every time point. HBsAg reduction indicates suppression of the fundamental biologic mechanisms that HDV requires for viral replication. ALT was normalized in approximately half of participants by Week 72 and (for the subset of patients evaluable) Week 96. There were no grade 3 or higher treatment-related adverse events in the combination arm, and treatment emergent adverse events were generally mild to moderate and transient.

Vir Bio initiated its registrational clinical program, ECLIPSE, evaluating the tobevibart and elebsiran combination in people living with CHD, in March of 2025. The program includes three randomized, controlled trials (ECLIPSE 1, 2, and 3) designed to evaluate the combination therapy in comparison to deferred treatment or bulevirtide. All three trials are ongoing, with ECLIPSE 1 and 3 completing enrollment ahead of the Company’s expectations. Topline results from ECLIPSE 1 are expected in the fourth quarter of 2026, and topline results from ECLIPSE 2 and ECLIPSE 3 are expected in the first quarter of 2027.

The combination of tobevibart and elebsiran has now been recognized by the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for their potential to address the critical unmet need in CHD. The investigational combination therapy has been granted Breakthrough Therapy and Fast Track designations by the U.S. Food and Drug Administration (FDA), and Priority Medicines (PRIME) and orphan drug designations by the EMA.

On December 15, 2025, we and Norgine Pharma UK Limited (together with its affiliates in the Norgine group of companies, Norgine) entered into a License Agreement (the Norgine Agreement) with respect to certain commercial and certain development rights to the combination of tobevibart and elebsiran for the treatment of people living with CHD as described in further detail below under “—Our Collaboration, License and Grant Agreements,” Under the terms of the Norgine Agreement, Vir Bio granted Norgine an exclusive license for the commercial rights and certain development rights to the combination for the treatment of CHD in Europe, Australia, and New Zealand (collectively, the Norgine Territory), while Vir Bio will retain commercial rights for the combination in the United States and all other international markets outside of the People’s Republic of China and Taiwan.

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Chronic Hepatitis B (CHB)

CHB is a long-lasting, inflammatory liver disease caused by the HBV. The World Health Organization estimates that 254 million people live with CHB, and an estimated 1.1 million yearly deaths are associated with the disease. Complications from CHB may include liver cirrhosis, liver failure and liver cancer.

The rate of functional cure (lifelong control of the virus after a finite duration of treatment) with current approved treatments is 3%-7%. Alternatively, suppressive therapy with daily nucleotide/nucleoside reverse transcriptase inhibitors (NRTIs) is commonly used, and CHB patients often require a lifetime of therapy, and NRTIs reduce but do not eliminate the risk of further progression and developing end-stage liver disease complications such as cirrhosis or cancer.

In July 2021 we initiated the MARCH two-part study to evaluate the combination of tobevibart and elebsiran in virally suppressed HBV patients. The latest results from the MARCH Part B Phase 2 trial evaluating the combination of tobevibart and elebsiran without or with pegylated interferon alpha (PEG-IFNα) were presented in an oral session at the European Association for the Study of the Liver (EASL) congress in Amsterdam (The Netherlands) in May 2025. The 24-week post-end of treatment data revealed that the study-defined primary endpoint, proportion of participants with undetectable HBsAg at 24 weeks post-end of treatment, was achieved by 17% (3/18) and 21% (3/14) of participants with baseline HBsAg<1,000 IU/mL receiving tobevibart and elebsiran without or with PEG-IFNα, respectively. These proportions were 8% (4/51) and 16% (5/32) for tobevibart and elebsiran without or with PEG-IFNα, respectively, in all participants. The safety and tolerability profile of tobevibart and elebsiran was consistent with prior studies, with no new safety concerns and generally only mild or moderate treatment emergent adverse events being reported throughout the study. Vir Bio decided not to pursue Phase 3 development of combinations of tobevibart, and elebsiran in CHB. We have streamlined the final stages of the MARCH Phase 2 program to ensure continued participant benefit and safety.

Elebsiran is also being evaluated in additional Phase 2 clinical trials with collaborators. Brii Biosciences Offshore Limited (Brii Bio) is the sponsor for the Phase 2 trial of elebsiran in combination with BRII-179, an investigational therapeutic vaccine, for the treatment of chronic HBV infection. As described in further detail below under “—Our Collaboration, License and Grant Agreements,” we granted Brii Bio an option to obtain exclusive rights to develop and commercialize elebsiran and tobevibart in the Greater China Territory (People’s Republic of China, Hong Kong, Taiwan and Macau), for the treatment, palliation, diagnosis, prevention or cure of acute and chronic diseases of infectious pathogen origin or hosted by pathogen infection, or the Field of Use.

HIV treatment and functional cure

Despite major advances in HIV treatment, most people living with HIV must take daily antiretroviral medications for viral control. HIV broadly neutralizing antibodies (bnAbs) are a novel modality that has shown promise for controlling the virus without daily antiretroviral medications. Furthermore, HIV bnAb treatment can induce a state of viral control off therapy, effectively a functional cure. While these outcomes are currently only found in rare individuals and for limited time periods, it suggests that HIV bnAbs could be an important part of a functional cure regimen.

With the support of the Gates Foundation, we are developing a unique and innovative HIV bnAb therapeutic. We have in-licensed HIV bnAbs from Togontech GmbH, including the 04-A06 bnAb published in Nature Immunology, that shows what we believe to be favorable preclinical properties, including neutralization breadth and potency to combat the diversity of HIV strains worldwide and resistance to the ability of the virus to escape from therapeutic intervention. We are further engineering HIV bnAbs with our Fc engineering technology to enhance their half-life, effector functions, and engagement with the patient’s immune system. We believe the resulting therapeutic can make an important impact on the lives of people living with HIV.

Oncology

One in five people worldwide develop cancer during their lifetime, and although tremendous strides have been made in cancer prevention and treatment, cancer still remains the second-leading cause of death globally and remains the leading or second-leading cause of premature death (before age 70 years) in 112 countries.

While major advances have been made in immunotherapies for hematologic malignancies, a large unmet need remains for novel and tolerable therapeutics for patients with solid tumors. TCEs are potent anti-tumor agents that direct the immune system, specifically T-cells, to attack cancer cells. Vir Bio’s bi-specific TCE is comprised of two antibody fragments: a tumor-associated antigen (TAA) binding domain and a CD3 binding domain. They are designed to simultaneously recruit T-cells and TAA-expressing cancer cells, directing the cytotoxic activity of T-cells against the tumor. However, if the antigen is also expressed on healthy cells, bi-specific TCEs can similarly bind to TAAs present in non-cancerous cells or healthy tissue, driving on-target, off-tumor toxicity, including cytokine release syndrome (CRS), thus limiting the potential therapeutic index of TCEs.

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Masking of TCEs is a strategy designed to circumvent these limitations. This technology specifically leverages overactivity of proteases in the tumor microenvironment (whereas proteases are tightly regulated by protease inhibitors elsewhere in the body). By attaching masks joined by protease cleavable linkers to the TCE, Vir Bio’s TCEs are designed to remain inactive until they reach the tumor microenvironment. Once in the tumor microenvironment, tumor-specific proteases can cleave off the mask and release the unmasked TCE, which can bind to both T-cell and tumor cells expressing the TAA, and lead to killing of cancer cells. By limiting the unmasking of the TCEs to the tumor microenvironment, we aim to limit the toxicity of these agents in the periphery and potentially increase their safety and efficacy.

We are currently advancing three clinical-stage dual-masked TCEs: VIR-5500 (Phase 1); VIR-5818 (Phase 1); and VIR-5525 (Phase 1). These molecules leverage the PRO-XTEN® masking technology with TCEs targeting CD3 on T-cells and HER2, PSMA and EGFR, respectively, on tumor cells.

VIR-5500 for the treatment of metastatic castration-resistant prostate cancer

Molecular Characteristics and Preclinical Data. VIR-5500 is a protease-activated, bispecific dual-masked TCE, designed to exploit the dysregulated protease activity in tumors relative to healthy tissues, thus expanding the safety margin and therapeutic index. The VIR-5500 core consists of a VHH (single-variable domain on a heavy chain) domain targeting PSMA and an scFv-targeting CD3. The core is flanked by two unstructured polypeptide masks (XTEN™ masks) that sterically reduce target engagement in healthy tissue and extend the half-life of the protein. Protease cleavage sites at the base of the XTEN™ masks enable proteolytic activation of unmasked protein in the tumor microenvironment, unleashing a small, highly potent unmasked TCE, designed to redirect cytotoxic T-cells to kill PSMA-expressing tumor cells. In healthy tissues, in which protease activity is minimal due to tight regulation, VIR-5500 should remain predominantly inactive.

Phase 1 Trial of VIR-5500. VIR-5500 is being evaluated in a Phase 1 clinical trial designed to assess its safety, pharmacokinetics, and preliminary efficacy as a monotherapy in late-line mCRPC and standard-of-care combinations in earlier-line settings. Positive updated monotherapy dose-escalation data from the ongoing Phase 1 trial will be presented at the 2026 American Society of Clinical Oncology (ASCO) Genitourinary Cancers Symposium in February 2026. These data support VIR-5500’s favorable safety and tolerability profile and show that treatment with VIR-5500 provided dose-dependent anti-tumor activity as measured by both PSA declines and radiographic responses.

Data across all patients receiving VIR-5500 monotherapy in the Phase 1 trial (n=58) show that VIR‑5500 was generally well tolerated with no dose‑limiting toxicities observed to date. Grade ≥3 treatment‑related adverse events occurred in 12% (7/58) of patients and were manageable. Limited CRS was observed in 50% (29/58) of patients, with events generally limited to Grade 1 (fever only). Prophylactic steroids were not required and were only explored in a small cohort of three patients. Enrolled patients were heavily pretreated (median of four prior lines) and a substantial proportion presented with high tumor burden, including 45% (25/58) with visceral metastases.

Dose‑dependent activity was observed across the entire treatment group as measured by both prostate-specific antigen (PSA) declines and radiographic responses. Efficacy data were reported in the highest dose cohorts (≥3,000 µg/kg Q3W; n=22/58) as of the January 9, 2026 data cut-off. In these cohorts, among those patients who were PSA-evaluable (i.e., received a full cycle of treatment and had completed both pre- and post-treatment PSA assessments in accordance with applicable prostate cancer clinical trial guidance) (n=17), PSA501 declines occurred in 82% (14/17) and PSA902 declines occurred in 53% (9/17) of patients. Among RECIST (Response Evaluation Criteria in Solid Tumors)‑evaluable patients, objective responses were seen in 45% (5/11). Of the five responders, four achieved confirmed responses with one patient pending confirmation. Reductions on PSMA‑PET (positron emission tomography) affirm PSA declines and radiographic responses, with tumor shrinkage observed across multiple lesions, including visceral metastases. These findings support proof‑of‑concept and further evaluation in expansion cohorts.

We have concluded QW and Q3W monotherapy dose-escalation in late-line mCRPC and has defined a preliminary go-forward dose and regimen recommendation for expansion. In parallel, dose-escalation of VIR-5500 in combination with enzalutamide continues in early-line mCRPC patients. We anticipate initiating monotherapy dose-expansion cohorts in late-line mCRPC and combination dose-expansion cohorts in both early-line mCRPC and metastatic hormone-sensitive prostate cancer (mHSPC) in the second quarter of 2026 followed by pivotal Phase 3 trials in 2027.

1 PSA decline of 50%-100% from baseline.

2 PSA decline of 90%-100% from baseline.

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VIR-5818 ± pembrolizumab for the treatment of HER2-positive solid tumors

Molecular Characteristics and Preclinical Data. While the role of HER2 in breast and gastric cancer has been well established for many years, only recently has there been a recognition of the importance of HER2 in other disease types, in particular as a resistance biomarker to other signaling pathways such as EGFR. With more patients undergoing biopsies after progression from prior therapies, and the advance of more routine molecular genotyping, numerous aberrations in HER2 have been discovered. Collectively, HER2+ tumors (IHC 3+ or in situ hybridization [ISH]+) and solid tumors with activating HER2 mutations represent a large unmet need. VIR-5818, with its novel mode of action and potential for large safety margins due to masking, may be an important treatment option that can extend survival and provide cancer immunity to these tumors.

VIR-5818 is a HER2-targeted, conditionally activated masked TCE designed to exploit dysregulated protease activity in tumors while sparing healthy tissues in which there is minimal protease activity, thus broadening the safety margin and therapeutic index. The core consists of two, tandem, single-chain variable fragments (scFvs) targeting CD3 and HER2 that are flanked by two unstructured polypeptide masks (XTEN™) that sterically reduce target engagement in normal tissues and extend half-life. Protease cleavage sites at the base of the XTEN™ masks enable proteolytic activation of fully masked TCE in the tumor microenvironment, unleashing a small, highly potent, unmasked TCE, which is able to redirect cytotoxic T-cells to kill target-expressing tumor cells. The potent, unmasked form (uTCE) of VIR-5818, also has a much shorter half-life to potentially increase the therapeutic index if the activated form should leak back into circulation. In healthy tissues, in which protease activity is tightly regulated, VIR-5818 should remain predominantly masked and as an intact prodrug. Additional information is available below under “— Our Technology Platforms.”

GLP NHP toxicology studies have demonstrated minimal toxicities with a NOAEL at the top dose evaluated of 6mg/kg. Unmasked VIR-5818 had single digit pM potent cytotoxicity to HER-2 expressing tumor cells, but significantly less cytotoxic to HER-2 expressing cardiomyocytes, requiring >1uM, thus demonstrating the potential wide therapeutic index compared to normal tissue and showing the need for dysregulated proteases (only found in tumor cells) for unmasking and eventual cell killing.

Phase 1 Trial of VIR-5818 ± pembrolizumab. VIR-5818 is being evaluated in a Phase 1 clinical trial designed to study its safety and pharmacokinetics alone, and in combination with pembrolizumab, in participants with a variety of HER2-expressing cancers, including breast and colorectal cancer (CRC). Early safety and efficacy data from the monotherapy cohort was presented at an investor event on January 8, 2025.

Early efficacy data showed that 50% (10/20) of participants receiving VIR-5818 doses ≥400 µg/kg experienced dose-dependent tumor shrinkage across multiple HER2-positive tumor types at either QW or Q3W dosing schedule after an initial step-up dosing in Cycle 1. This includes participants who had received up to nine prior lines of therapy. Strong anti-tumor activity was observed in a subset of participants with HER2-positive CRC who have exhausted standard of care. In this subset, confirmed partial responses (cPRs) were seen in 33% (2/6) of participants at early doses, and one patient continued in cPR for more than 18 months as of the data cut-off in November 2024. All the HER2-positive CRC tumors were also MSS (Microsatellite Stable) which traditionally are unresponsive to immunotherapies.

Preliminary safety data demonstrated that VIR-5818 was generally well-tolerated, with minimal grade 1 or 2 CRS (20% and 10%, respectively) and no grade 3 or greater CRS observed in any of the 79 participants across doses up to 1 mg/kg. Most TEAEs were low grade, reversible and manageable. The maximum tolerated dose (MTD) has not yet been reached. Preliminary pharmacokinetics and safety data indicate low systemic unmasking of the TCE, suggesting tumor-specific activation. Dual masking results in a half-life of approximately six days, which may enable a less frequent dosing regimen, such as Q3W. VIR-5818 continues to advance through dose escalation as a monotherapy, and in combination with pembrolizumab, in multiple tumor types, including metastatic breast cancer and metastatic colorectal cancer.

VIR-5525

Molecular Characteristics and Preclinical Data. VIR-5525 is an investigational dual-masked TCE that combines a bispecific EGFR and CD3 binding TCE with the PRO-XTEN® masking technology. Similarly to VIR-5818 and VIR-5500, VIR-5525 is also conditionally activated and designed to exploit dysregulated protease activity in tumors while sparing healthy tissues in which there is minimal protease activity, thus broadening the safety margin and therapeutic index. The core consists of two, tandem, single-chain variable fragments (scFvs) targeting CD3 and EGFR, that are flanked by two unstructured polypeptide masks (XTEN™) that sterically reduce target engagement in normal tissues and extend half-life. Protease cleavage sites at the base of the XTEN™ masks enable proteolytic activation of fully masked TCE in the tumor microenvironment, unleashing a small, highly potent, unmasked TCE, which is able to redirect cytotoxic T-cells to kill target-expressing tumor cells. The potent, unmasked form (uTCE) of VIR-5525, also has a much shorter half-life to potentially increase the therapeutic index if the activated form should leak back into circulation. In healthy tissues, in which protease activity is tightly regulated, VIR-5525 should remain predominantly masked and as an intact prodrug.

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Phase 1 Trial of VIR-5525. VIR-5525 is being evaluated in a Phase 1 clinical trial designed to assess its safety, pharmacokinetics, and preliminary efficacy as a monotherapy and in combination with pembrolizumab in a variety of EGFR-expressing solid tumors, such as non-small cell lung cancer (NSCLC), CRC, head and neck squamous cell carcinoma (HNSCC), and cutaneous squamous cell carcinoma (cSCC). We announced in July 2025 that the first patient in the trial had been dosed. VIR-5525 continues to advance through Phase 1 dose escalation as a monotherapy.

Undisclosed PRO-XTEN® TCE Targets

We are advancing multiple undisclosed PRO-XTEN® dual-masked TCEs targeting clinically validated targets with potential applications across a variety of solid tumors. These preclinical candidates leverage the PRO-XTEN® masking technology with novel TCE fragments discovered and engineered using our antibody discovery platform.

Our Technology Platforms

Vir Bio has built a strong foundation based on cutting-edge core scientific capabilities and a team of experts who bring deep knowledge and experience to our R&D efforts. This has enabled us to make significant strides in infectious disease, and strategically expand our focus to address critical unmet needs in oncology.

Platforms for the Creation of Transformative Medicines

Millions of people suffer from infectious diseases and cancer, both of which result in disease by evading the immune system. We have purposefully assembled a portfolio of technology platforms that we believe will, individually or in combination, allow us to modulate the immune system in innovative ways, harnessing its power to combat viruses and fight cancer.

Vir Bio’s Discovery Engine is propelled by our exceptional protein engineering and antibody discovery expertise and our two core technology platforms:

1.Antibody and TCE Discovery and Engineering Platform: We continue to leverage our expertise in antibody discovery and development, enhanced by machine learning and artificial intelligence. Using strategies such as our dAIsY™ system, we can engineer our candidates to optimize key biological and biophysical properties, such as half-life and developability. This discovery platform is utilized to generate antibodies that can be further developed into therapeutic molecules, including the generation of dual-masked TCEs against novel tumor targets.

2.PRO-XTEN® Masking Technology Platform: This innovative technology aims to prevent potential toxicity of highly active drugs outside of their intended site of action. In oncology, this means anti-cancer agents, such as TCEs, become active selectively when entering the tumor microenvironment. This enhances tumor specificity while minimizing off-target effects, potentially improving both efficacy and safety. Masking also increases half-life in circulation, potentially resulting in more convenient dosing regimens for patients and clinicians. Importantly, the PRO-XTEN® masking technology is a universal platform – meaning that it can be used with different molecules without the need to tailor it every single time.

This discovery engine is complemented by our internal capabilities in process development, analytical development, manufacturing, and quality control. We also maintain strategic partnerships with contract development and manufacturing organizations (CDMOs) to support our clinical programs. This combination of cutting-edge technologies, artificial intelligence-driven optimization, and deep immunological expertise positions us to create potentially transformative medicines for some of the more challenging diseases facing humanity today.

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mAb: monoclonal antibody platform; prot. eng: protein engineering capabilities; AI: artificial intelligence

Antibody and TCE Discovery and Engineering Platform

Overview

We have developed cutting-edge platforms to identify and enhance rare, potent mAbs using AI-enabled protein engineering for the treatment of infectious diseases and cancer. Our platforms leverage the efficient interrogation of memory B cells from two primary sources: convalescent human patients and transgenic mice expressing human- immunoglobulin G (IgG) following immunization. This approach enables the selection of highly potent antibodies with unique characteristics that can be further developed into therapeutic molecules, including PRO-XTEN® dual-masked TCEs targeting novel TAAs.

Our platform has been successfully applied to identify mAbs for multiple pathogens including SARS-CoV-2, HBV, HDV, Ebola virus, and HIV. Noteworthy achievements include:

•Sotrovimab (Xevudy®): Anti-SARS-CoV-2 mAb, granted Emergency Use Authorization (EUA) or marketing authorization in multiple regions.

•Ansuvimab (Ebanga™): Anti-Ebola virus mAb developed in collaboration with the NIH and marketed by Ridgeback Biotherapeutics LP.

Our Approach

mAbs function through various mechanisms including pathogen neutralization, target cell lysis (infected or tumor cells), and immunomodulation. Our approach combines rapid, high-throughput isolation of rare and highly potent fully human mAbs from cell culture-based libraries of clonal B lymphocytes. Our deep expertise in antibody discovery and engineering provides a strong foundation for developing next-generation TCEs as well as antibody-based therapeutics for multiple therapeutic areas, including cancer.

Our proprietary antibody screening technology enables the screening of antibodies from hundreds of millions of B cells derived from either convalescent individuals or human-Ig immunized mice. This screening identifies rare and potent mAbs capable of binding highly conserved antigens, neutralizing multiple pathogens, or selectively targeting host proteins, including tumor antigens or antigens involved in the modulation of anti-tumor immune responses.

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These fully human antibodies can be refined using our proprietary AI-driven protein engineering technology, dAIsY™, enhancing their potency, resistance, pharmacokinetics, as well as their manufacturability. This involves optimizing the antigen-binding fragment (Fab) regions to improve efficacy, potency, and manufacturability, as well as the Fc region to fine-tune the antibody's half-life and to enhance its ability to engage effector functions of the immune system. In this context, we have developed a set of novel and proprietary Fc mutations that have the potential to enhance the anti-tumor efficacy of antibodies.

PRO-XTEN® Masking Technology Platform

Overview

The PRO-XTEN® masking technology exploits the high protease activity of the tumor microenvironment to specifically release the active form of a drug via release of the mask selectively in tumor tissues. It can be applied to a variety of molecules such as TCEs or cytokines to broaden the therapeutic index for patients. The preferential release of the drug in the tumor microenvironment is designed to minimize on-target, off-tumor toxicity. The PRO-XTEN® mask is designed to extend the half-life resulting in more convenient dosing regimens for patients and clinicians. This masking approach could be key to pursuing validated oncology targets typically associated with therapies of high toxicity, ultimately offering an opportunity to potentially increase the therapeutic index of drug candidates and deliver more efficacious and safer options for patients.

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Our Approach

We are currently investigating the PRO-XTEN® technology in conjunction with TCEs. These are powerful anti-tumor agents that direct the immune system, specifically T-cells, to destroy cancer cells. The PRO-XTEN® masking technology is designed to keep the TCEs inactive (or masked) until they reach the tumor microenvironment, where tumor-specific proteases cleave off the masks and activate the TCEs leading to killing of cancer cells. By driving the activity selectively to the tumor microenvironment, we aim to circumvent the traditionally high toxicity associated with TCEs and increase their efficacy and tolerability.

TCE: T-Cell Engager

Our dual-masked TCEs are single protein polypeptides with three key functions, a bi-specific TCE at their core, two universal PRO-XTEN® masks, which are connected to the TCE component by protease-cleavable linkers. The bi-specific TCE is comprised of two antibody fragments: a TAA binding domain and a CD3 binding domain. Upon unmasking, they are designed to simultaneously recruit T-cells to cells expressing the target TAA, preferentially cancer cells, directing the cytotoxic activity of T-cells against the tumor. Our discovery and antibody engineering capabilities are extendable to optimizing TAA and T-cell engagement components and identifying novel TCE fragments for additional targets. The protease-activated linkers that are part of PRO-XTEN® were discovered by applying a combination of in vitro and in vivo experiments together with a genetic algorithm for sequence optimization.

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TME: tumor microenvironment; TCE: T-Cell Engager; CD3: cluster of differentiation 3; TAA: tumor associated antigen; CRS: cytokine release syndrome; Q3W: once every 3 weeks

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Our Collaboration, License and Grant Agreements

Collaboration and License Agreement with Astellas

On February 19, 2026, we and Astellas US LLC (together with its subsidiaries and affiliates (including its indirect parent, Astellas Pharma Inc.), Astellas) entered into a Collaboration and License Agreement (the Astellas Agreement). Upon closing of the transaction contemplated by the Astellas Agreement, we and Astellas will enter into a global strategic collaboration to co-develop and co-commercialize VIR-5500, an investigational PRO-XTEN® dual-masked CD3 TCE targeting PSMA for the treatment of prostate cancer that is currently in Phase 1 development, through a sharing of expenses and revenues. We have agreed to grant to Astellas, subject to certain intellectual property rights of Sanofi, an exclusive license to develop, manufacture, commercialize and otherwise exploit VIR-5500 and certain related derivative compounds throughout the world for therapeutic, prophylactic, palliative and diagnostic uses.

Under the terms of the Astellas Agreement, in the U.S., we will share profits and losses from future sales of VIR-5500 equally with Astellas, should VIR-5500 receive regulatory approval, and we will have the option to co-promote VIR-5500. Outside of the U.S., Astellas will obtain exclusive rights to commercialize VIR-5500 and be responsible for all commercialization costs. We will jointly develop VIR-5500, with global clinical development costs shared 40% by us and 60% by Astellas, while costs of U.S.-specific studies will be shared equally, and Astellas will be solely responsible for costs of ex-U.S.-specific studies. In addition, we have the option to opt out of development cost sharing responsibilities and U.S. profit sharing, and in such case, Astellas will pay us royalties on net sales made in the U.S., as described below.

We will receive $335 million in upfront and near-term milestone payments, including $240 million in cash, a $75 million equity investment pursuant to a separate Stock Purchase Agreement (the Astellas SPA, described further below), and a near-term $20 million milestone payment upon completion of manufacturing technology transfer, anticipated in the second quarter or third quarter of 2027. We will also be eligible to receive up to $1.37 billion in future development, regulatory and ex-U.S. sales milestones, along with tiered, double-digit royalties on ex-U.S. net sales, which royalties are subject to reduction under certain specified circumstances. If we elect to opt out of development cost sharing responsibilities and U.S. profit sharing, we would be eligible to receive up to $1.37 billion (or $1.60 billion if we have met a pre-defined limited funding threshold at the time of the opt-out) in future development, regulatory and global sales milestones, along with tiered, double-digit royalties on global net sales, which royalties are subject to reduction under certain specified circumstances. Further, certain opt-out milestones, if met, will include reimbursement of a portion of our previously expensed development and commercialization spend. The closing of the transaction is subject to the expiration or termination of the applicable waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

Under the terms of the Sanofi Agreement, we will share with Sanofi 20% of certain future collaboration proceeds, including the upfront payment, equity premium and the portion of milestones, profit-share and royalties that exceed amounts already owed to Sanofi.

Either party may terminate the Astellas Agreement in cases of uncured, material breaches or insolvency. Astellas may terminate the Astellas Agreement for convenience in its entirety (upon 90 days’ notice to us if there has not been any commercial sale for any licensed product in any covered territory or else upon 180 days’ written notice) or with respect to a licensed product and a given country (upon 90 days’ written notice if there has been no commercial sale in the relevant country or else upon 180 days’ written notice). Astellas may also terminate the agreement in its entirety or with respect to one or more products upon 30 days’ written notice if Astellas determines in good faith that the risks to patients from continuing the development or commercialization of the relevant product or products are greater than the potential benefits of such development and commercialization. Subject to certain conditions, we have the right to terminate the agreement upon certain patent challenges by Astellas or if Astellas does not conduct any material development or commercialization activities or otherwise ceases or abandons all such activities for 12 consecutive months.

Concurrently with the execution of the Astellas Agreement, we have also entered into the Astellas SPA, pursuant to which Astellas has agreed to purchase 7,239,382 shares of our common stock for an aggregate purchase price of approximately $75 million, subject to customary closing conditions and the closing of the Astellas Agreement. The purchase price per share of our common stock of $10.36 is equal to a 50% premium of the 30-day volume weighted average price of a share of our common stock as of February 17, 2026. The Astellas SPA includes standstill, voting and lockup provisions, with customary exceptions, that expire one year after the date of the anticipated closing of the Astellas SPA. One year after the anticipated closing of the Astellas SPA, Astellas will have, under certain circumstances, a customary right to require us to register the resale of the shares purchased pursuant to the Astellas SPA.

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License Agreement with Norgine

On December 15, 2025, we and Norgine Pharma UK Limited (together with its affiliates in the Norgine group of companies, Norgine) entered into a License Agreement (the Norgine Agreement) under which we granted Norgine an exclusive license for the commercial rights to the combination of tobevibart and elebsiran for the treatment of CHD in Europe, Australia, and New Zealand (collectively, the Norgine Territory), while we will retain commercial rights for the combination in the United States and all other international markets outside of the Greater China Territory. In exchange, we received an initial reimbursement of development costs from Norgine in the amount of €55 million in December 2025 and are eligible to receive up to an additional €495 million in clinical, regulatory and sales milestones, along with tiered, mid-teen to high-twenties percent royalties on net sales in the Norgine Territory. In addition, clinical development costs for the ongoing trials in our ECLIPSE registrational program (ECLIPSE 1, 2 and 3) will be shared, with Norgine contributing approximately 25% of go-forward external costs.

The Norgine Agreement will remain in force, on a licensed product-by-licensed product and country-by-country basis, until the latest of (a) the 12th anniversary of the first commercial sale; (b) the date of expiration of the last-to-expire valid claim of any licensed patent; and (c) the expiration of regulatory exclusivity. Either party may terminate the Norgine Agreement in cases of material breaches or insolvency. Norgine may terminate the Norgine Agreement with 180 days’ prior written notice prior to the first commercial sale of any licensed product and with 12 months’ prior written notice on or after the first commercial sale of any licensed product.

License Agreement with Sanofi

On September 9, 2024, we closed a license agreement with Amunix Pharmaceuticals Inc. (Amunix), a Sanofi company, previously announced on August 1, 2024 (the Sanofi Agreement), pursuant to which we obtained an exclusive (as to Sanofi and its affiliates), worldwide, royalty-bearing, sublicensable (through multiple tiers), transferable license to research, develop, manufacture, commercialize and otherwise exploit: (i) three clinical-stage masked TCEs of Sanofi, for all therapeutic, prophylactic, palliative, and diagnostic uses, and (ii) the PRO-XTEN® universal masking technology for oncology and infectious disease, excluding the ophthalmological field. As part of the closing of the Sanofi Agreement, we made an upfront payment to Sanofi in the amount of $100.0 million and transferred $75.0 million to an escrow account that was due to former shareholders of Amunix upon VIR-5525 achieving “first in human dosing” by 2026. In July 2025, the first patient was dosed in a phase 1 study evaluating VIR-5525 and as a result, we paid the $75.0 million milestone during the third quarter of 2025. Sanofi will also be eligible to receive up to an additional $323.0 million in future development and regulatory milestone payments, up to an additional $1.49 billion in commercial net sales-based milestone payments, and low single-digit to low double-digit tiered royalties on worldwide net sales. In addition, if, within a two-year period from the execution of the Sanofi Agreement, we execute a transaction that gives rise to Vir Bio receiving certain sublicense income related to the licenses obtained from the Sanofi Agreement, Sanofi may be eligible to receive a portion of such income.

The Sanofi Agreement will remain in force, on a product-by-product and country-by-country basis, until the expiration of all royalty payment obligations. We may terminate the Sanofi Agreement in its entirety, or on a product-by-product basis, for convenience upon 120 days’ written notice if there have been no commercial sales of such target or upon 12 months written notice after the first commercial sale of such target as long as such termination is after December 31, 2026.

Collaboration Agreements with GSK

2020 Collaboration Agreement with GSK

In June 2020, we entered into a definitive collaboration agreement with GSK (the 2020 GSK Agreement), pursuant to which we agreed to collaborate to research, develop and commercialize products for the prevention, treatment and prophylaxis of diseases caused by SARS-CoV-2, the virus that causes COVID-19, and potentially other coronaviruses. The collaboration was originally structured around three categories of product candidates; however, only sotrovimab, VIR-7832, and certain related antibody variants remain active programs under the 2020 GSK Agreement. In connection with the 2020 GSK Agreement, we also entered into a stock purchase agreement in April 2020, pursuant to which we issued 6,626,027 shares of our common stock to Glaxo Group Limited, an affiliate of GSK, at a price per share of $37.73 and an aggregate purchase price of approximately $250.0 million.

We retained the sole right to progress the development and commercialization of the terminated antibody products independently (including with or for third parties), subject to the payment of tiered royalties to GSK on net sales of such terminated antibody products at percentages ranging from the very low single digits to the mid-single digits, depending on the nature of the antibody product being commercialized.

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Regarding sotrovimab, the parties share all development costs, manufacturing costs, and costs and expenses for the commercialization of the collaboration products, with us bearing 72.5% of such costs for sotrovimab, except that GSK has the sole right to develop (including to seek, obtain or maintain regulatory approvals), manufacture and commercialize sotrovimab in and for the Greater China Territory at GSK’s sole cost and expense. As the lead party for all manufacturing and commercialization activities, GSK incurs all of the manufacturing, sales and marketing expenses and is the principal on sales transactions with third parties.

The 2020 GSK Agreement will remain in effect with respect to sotrovimab for as long as it is being commercialized by the lead party. Either party has the right to terminate the 2020 GSK Agreement in the case of the insolvency of the other party, an uncured material breach of the other party with respect to a collaboration program or collaboration product, or as mutually agreed by the parties.

In May 2021, the FDA granted an EUA in the U.S. for sotrovimab, for the early treatment of mild to moderate COVID-19 in adults and pediatric patients (12 years of age and older weighing at least 40 kg) with positive results of direct SARS-CoV-2 viral testing, and at high risk for progression to severe COVID-19, including hospitalization or death. In December 2021, the EC granted marketing authorization to Xevudy® (sotrovimab) in the EU for the treatment of adults and adolescents at increased risk of progressing to severe COVID-19. In April 2022, the FDA excluded the use of sotrovimab in all U.S. regions due to the continued proportion of COVID-19 cases caused by certain variants, and in December 2024, the FDA revoked EUA granted to sotrovimab. Going forward, we expect a nominal amount of license and collaboration revenue, if any, from our 2020 GSK Agreement, and we may incur negative license and collaboration revenue related to costs for ongoing required support efforts that our partner GSK leads.

2021 Expanded GSK Collaboration

In 2021, we entered into the 2021 GSK Agreement under which the parties agreed to expand the 2020 GSK Agreement and to collaborate on three separate programs, all of which had been subsequently terminated except for an RSV program selected in 2022.

We opted-out of the RSV program during the fourth quarter of 2024. As a result of our opt-out, GSK may continue to pursue the development and commercialization of the RSV program unilaterally. If the RSV program reaches commercialization, GSK will pay us a royalty on net sales in the low single digits.

In connection with the 2021 GSK Agreement, we entered into a stock purchase agreement with GGL pursuant to which we issued 1,924,927 shares of our common stock to GGL for an aggregate purchase price of approximately $120.0 million.

Collaboration and License Agreement with Alnylam

In October 2017, we and Alnylam Pharmaceuticals, Inc. (Alnylam) entered into a collaboration and license agreement (the Alnylam Agreement). Under the Alnylam Agreement, we obtained a worldwide, exclusive license to develop, manufacture and commercialize siRNA product candidates directed to HBV, including elebsiran, for all uses and purposes including the treatment of HBV and HDV indications. Under the Alnylam Agreement, we also held options to obtain similar licenses to siRNA product candidates for up to four other infectious disease targets selected by Vir Bio, but following an amendment and restatement of the Alnylam Agreement in March 2025 (the Restated Alnylam Agreement), those options (and all rights and obligations related to those infectious disease targets) were terminated. At the same time Alnylam elected to not opt-in to the profit-sharing arrangement with respect to any licensed siRNA product candidates, including elebsiran, directed to HBV or HDV. We remain solely responsible, at our expense, for conducting all development, manufacture and commercialization activities for elebsiran in HBV and HDV indications, and we are required to use commercially reasonable efforts to develop and commercialize elebsiran for the treatment of HBV or HDV indications in the United States and specified major markets.

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In connection with the Restated Alnylam Agreement and Alnylam’s election to not opt-in to the profit-sharing arrangement, we paid Alnylam $30.0 million in April 2025, and we will be required to pay Alnylam up to $145.0 million for remaining development and regulatory milestones for elebsiran. Such development and regulatory milestones for elebsiran will be payable to Alnylam only once, irrespective of dosage, formulation forms, route of administration or indication. Following commercialization, we will be required to pay Alnylam up to $250.0 million in the aggregate for the first achievement of specified levels of net sales by elebsiran products directed to HBV, whether for the treatment of HBV or HDV indications. We will also be required to pay Alnylam tiered royalties at percentages ranging from the low double-digits to mid-teens on annual net sales of siRNA products directed to HBV, such as elebsiran, whether for the treatment of HBV or HDV indications, subject to specified reductions and offsets. The royalties are payable on a product-by-product and country-by-country basis until the later of the expiration of all valid claims of specified patents covering such product in such country and 10 years after the first commercial sale of such product in such country. Alnylam is entitled to receive a portion of consideration we receive as a result of granting a sublicense under the licenses granted to Vir Bio by Alnylam under the Alnylam Agreement.

The term of the Restated Alnylam Agreement will continue, on a product-by-product and country-by-country basis, until expiration of all royalty payment obligations under the Restated Alnylam Agreement. We may terminate the Alnylam Agreement on a program-by-program basis or in its entirety for any reason on 90 days’ written notice. Either party may terminate the agreement for cause for the other party’s uncured material breach on 60 days’ written notice (or 30 days’ notice for payment breach), or if the other party challenges the validity or enforceability of any patent licensed to it under the Restated Alnylam Agreement on 30 days’ notice.

Exclusive License Agreement with the Institute for Research in Biomedicine

Prior to our acquisition of Humabs BioMed SA (referred to herein as Humabs) in August 2017, it entered into an exclusive license agreement in December 2011 with the Institute for Research in Biomedicine (IRB, and the agreement, the IRB Agreement). The IRB Agreement amended and restated an original 2004 exclusive license agreement between the parties in connection with IRB’s proprietary technologies relating to human monoclonal antibodies and the discovery of unique epitopes recognized by such antibodies performed at the IRB. In May 2008, Humabs entered into an exclusive license agreement with IRB (the Humabs IRB Agreement, and together with the IRB Agreement, the Current IRB License Agreements). Pursuant to the Humabs IRB Agreement, IRB granted to Humabs an exclusive license under certain intellectual property rights for the development of certain monoclonal antibodies with certain proprietary technologies of the IRB. In February 2012, Humabs and IRB entered into a research agreement (the IRB Research Agreement) to provide for a continuing research collaboration between Humabs and IRB, and to coordinate the exploitation of intellectual property rights arising from the IRB Research Agreement with the rights granted under the Current IRB License Agreements. Under the terms of the IRB Research Agreement, IRB performs certain research activities for Humabs, and all intellectual property rights arising under the IRB Research Agreement are either owned by Humabs, or included in and licensed to Humabs pursuant to the terms of the Current IRB License Agreements.

We use technology licensed under the Current IRB License Agreements in our product candidate tobevibart.

Pursuant to the Current IRB License Agreements, IRB granted to Humabs an exclusive, worldwide, royalty-bearing, sublicensable license under patent and know-how rights covering or associated with certain IRB’s proprietary technology platforms relating to antibody discovery, as well as rights in certain antibodies, including as a result of activities under the IRB Research Agreement, in each case for all purposes, including to practice the licensed technology platform, and to develop, manufacture and commercialize any drug, vaccine or diagnostic product containing such licensed antibodies.

Humabs is required to use commercially reasonable efforts to develop and commercialize licensed products, as well as maintain an active program to commercialize licensed products. Humabs is required to pay to IRB a flat royalty on net sales of licensed products approved for non-diagnostic use in the low single-digits, and a flat royalty on licensed products for diagnostic use at 50% of the non-diagnostic product rate, in each case subject to standard reductions and offsets. Humabs is also required to pay to IRB a specified percentage in the sub-teen double-digits of consideration received in connection with the grant of a sublicense to a non-affiliate third party, subject to a specified maximum dollar amount for the first up front or milestone payment received under such sublicense for each licensed product, and a lower specified maximum dollar amount for subsequent up front or milestone payments for such licensed product.

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Each of the Current IRB License Agreements remains in force until the expiration of all valid claims of the licensed patent rights and trade secrets included in the licensed IRB know-how. In addition, no royalties shall be payable under IRB know-how for any licensed product in any country after ten years from the date of first commercialization of such licensed product in that country. Humabs may terminate the IRB Agreement at will on 90 days’ written notice to IRB, and either party may terminate either of the Current IRB License Agreements on 60 days’ written notice for the uncured material breach of the other party.

Exclusive License Agreement with The Rockefeller University

In July 2018, we entered into an exclusive license agreement with The Rockefeller University, or Rockefeller, which was amended in May 2019, in September 2020, and in March 2021, or the Rockefeller Agreement. Pursuant to the Rockefeller Agreement, Rockefeller granted us a worldwide exclusive license under certain patent rights, and a worldwide non-exclusive license under certain materials and know-how covering certain antibody variants relating to a specified mutation leading to enhanced antibody function and utility, to develop, manufacture and commercialize infectious disease products covered by the licensed patents, or that involve the use or incorporation of the licensed materials and know-how, in each case for all uses and purposes for infectious diseases. The licenses granted to us are freely sublicensable to third parties. Rockefeller retains the right to use the licensed patents outside the field of use, and within the field of use solely in connection with educational, research and non-commercial purposes, as well as for certain research being conducted in collaboration with us. We are obligated to grant sublicenses to third parties with respect to products that are not being pursued and are not of interest to us following a specified anniversary of the May 2019 amendment date. Pursuant to the Rockefeller Agreement, we are required to use commercially reasonable efforts to develop and commercialize infectious disease products as soon as reasonably practicable, including by achieving certain specified development milestone events within specified time periods for products arising from our HBV and influenza programs.

We use technology licensed under the Rockefeller Agreement in our antibody platform and in our product candidate tobevibart.

Under the agreement we are required to pay license maintenance fees of $1.0 million annually, which will be creditable against royalties following commercialization. In addition, for the future achievement of specified development, regulatory and commercial success milestone events, we will be required to pay up to $80.3 million, in the aggregate, for up to six infectious disease products. Any follow-on products beyond six products may result in additional milestone event payments. We will also be required to pay Rockefeller a tiered royalty at a low single-digit percentage rate on net sales of licensed products, subject to certain adjustments. Our obligation to pay royalties to Rockefeller will terminate, on a product-by-product and jurisdiction-by-jurisdiction basis, upon the latest of the expiration of the last valid claim of a licensed patent in such jurisdiction, the expiration of all regulatory exclusivity in such jurisdiction or 12 years following the first commercial sale of the applicable licensed product in such jurisdiction. If we grant a sublicense to a non-affiliate third party under the Rockefeller technology, we will be required to pay Rockefeller a specified percentage of the consideration received from such sublicensee for the grant of the sublicense, depending on the date of receipt of the applicable sublicense income from such sublicensee.

The Rockefeller Agreement will remain in force, absent earlier termination, until the expiration of all of our obligations to pay royalties to Rockefeller in all jurisdictions. We have the right to terminate the Rockefeller Agreement in its entirety, or in part, for any reason on 60 days’ written notice to Rockefeller. Rockefeller may terminate the Rockefeller Agreement on 90 days’ written notice for our uncured material breach, or if we challenge the validity or enforceability of any of the licensed patents, or immediately in the event of our insolvency. Rockefeller may also terminate the Rockefeller Agreement if we cease to carry on business with respect to the rights granted to us under the agreement.

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Collaboration, Option and License Agreement with Brii Bio

In May 2018, we entered into a collaboration, option and license agreement with Brii Biosciences Limited (Brii Bio Parent) (formerly known as BiiG Therapeutics Limited), and Brii Bio (and such agreement, the Brii Agreement), pursuant to which we granted to Brii Bio, with respect to up to four of our programs, an exclusive option to obtain exclusive rights to develop and commercialize compounds and products arising from such programs in the Greater China Territory, for the treatment, palliation, diagnosis, prevention or cure of acute and chronic diseases of infectious pathogen origin or hosted by pathogen infection, or the Field of Use. In partial consideration for the options granted by us to Brii Bio, Brii Bio Parent and Brii Bio in turn granted us, with respect to up to four of Brii Bio Parent’s or Brii Bio’s programs, an exclusive option to be granted exclusive rights to develop and commercialize compounds and products arising from such Brii Bio programs in the United States for the Field of Use. The number of options that we may exercise for a Brii Bio program is limited to the corresponding number of options that Brii Bio exercises for a Vir Bio program. All options granted to Brii Bio under the Brii Agreement that are not exercised expired in May 2025. All options granted to us under the Brii Agreement that are not exercised will expire no later than two years following the expiration of all options granted to Brii Bio.

We are responsible, at our expense and discretion, for the conduct of all development activities under our programs prior to the exercise of Brii Bio’s options, and Brii Bio is responsible, at its expense and discretion, for all activities under its programs prior to the exercise of our options. Following the exercise of an option for a specified program by either us or Brii Bio, the exercising party is granted an exclusive, royalty-bearing license to develop, manufacture and commercialize products arising from the applicable program in the United States (where we are exercising the option) or the Greater China Territory (where Brii Bio is exercising the option), and such party is thereafter responsible for all development and commercialization activities, at its expense, in the optioned territory. If Brii Bio exercises its option with respect to our development program being conducted under the Amended Alnylam Agreement, Brii Bio’s rights will be subject to the terms of such amended agreement.

Under the terms of the Brii Agreement, following our option exercise, we are obligated to use commercially reasonable efforts to develop at least one licensed product arising from each optioned Brii Bio program, and to commercialize each such product in the United States following regulatory approval, and following Brii Bio’s option exercise, Brii Bio is obligated to use commercially reasonable efforts to develop at least one licensed product arising from each optioned Vir Bio program and to commercialize each such product in the Greater China Territory following regulatory approval.

On June 12, 2020, Brii Bio notified us of the exercise of its option to obtain exclusive rights to develop and commercialize compounds and products arising from elebsiran in the Greater China Territory. Brii Bio paid us a $20.0 million option exercise fee in connection with the option exercise. As mentioned above, our elebsiran program is being developed under the Amended Alnylam Agreement and as a result, we separately paid $10.0 million, half of the option proceeds, to Alnylam. In July 2022, Brii Bio notified us of the exercise of its option to obtain exclusive rights to develop and commercialize compounds and products arising from tobevibart in the Greater China Territory. Brii Bio paid us a $20.0 million option exercise fee in connection with the option exercise.

With respect to elebsiran and tobevibart for which Brii Bio exercised its options, Brii Bio will be required to pay regulatory milestone payments on a licensed product-by-licensed product basis ranging from the mid-single-digit millions up to $30.0 million, also determined based on the commercial potential of such program. Following commercialization, Brii Bio will be required to make sales milestone payments based on certain specified levels of aggregate annual net sales of products arising from each licensed program in the Greater China Territory, up to an aggregate of $175.0 million per licensed program. Brii Bio also will pay us royalties that range from the mid-teens to the high-twenties.

As partial consideration for our entry into the Brii Agreement, upon closing of Brii Bio Parent’s Series A preferred stock financing, we received Class A ordinary shares equal to 9.9% of the outstanding shares in Brii Bio Parent. As a result of Brii Bio’s right to exercise one of its options for elebsiran, under the terms of the Amended Alnylam Agreement, in February 2020 we transferred to Alnylam a specified percentage of such equity consideration allocable to such program. In July 2021, Brii Bio Parent completed its initial public offering, or the Brii Bio Parent IPO, on the Stock Exchange of Hong Kong Limited. Upon completion of the Brii Bio Parent IPO, our Class A ordinary shares held at Brii Bio Parent converted into the same single class of ordinary shares issued in the Brii Bio Parent IPO.

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In the event that we exercise an option for a Brii Bio program, we will be required to pay to Brii Bio an option exercise fee ranging from the low tens of millions to up to $50.0 million, determined based on the commercial potential of the licensed program. We will be required to make regulatory milestone payments to Brii Bio on a licensed product-by-licensed product basis ranging from the low tens of millions up to $100.0 million, also determined based on the commercial potential of such program. We will also be required to make sales milestone payments based on certain specified levels of aggregate annual net sales of products in the United States arising from each licensed program, up to an aggregate of $175.0 million per licensed program.

In addition, we are obligated under the Brii Agreement to pay Brii Bio tiered royalties based on net sales of products arising from the programs licensed to Vir Bio in the United States, and Brii Bio is obligated to pay us tiered royalties based on net sales of products arising from the programs licensed to Brii Bio in the Greater China Territory. The rates of royalties payable by us to Brii Bio, and by Brii Bio to us on net sales range from mid-teens to high-twenties. Each party’s obligations to pay royalties expires, on a product-by-product and territory-by-territory basis, on the latest of 10 years after the first commercial sale of such licensed product in the United States or Greater China Territory, as applicable; the expiration or abandonment of licensed patent rights that cover such product in the United States or Greater China Territory, as applicable; and the expiration of regulatory exclusivity in the United States or the Greater China Territory, as applicable. Royalty rates are subject to specified reductions and offsets.

The Brii Agreement will remain in force until the expiration of all options or, if any option is exercised, expiration of all royalty payment obligations for all licensed products within such licensed program, unless terminated in its entirety or on a program-by-program basis by either party. Each party may terminate for convenience all rights and obligations with respect to any program for which it has an option, with 30 days’ written notice (if the terminating party has not exercised an option for such program) or 180 days’ notice (following the exercise of an option for such program). The Brii Agreement may also be terminated by either party for insolvency of the other party, and either party may terminate the Brii Agreement in its entirety or on a program-by-program basis for the other party’s uncured material breach on 60 days’ written notice (or 30 days’ notice following failure to make payment).

Patent License Agreements with Xencor

In August 2019, we entered into a patent license agreement, which was amended in February 2021, or the 2019 Xencor Agreement, with Xencor, pursuant to which we obtained a non-exclusive, sublicensable (only to our affiliates and subcontractors) license to incorporate Xencor’s licensed technologies into, and to evaluate, antibodies that target influenza A and HBV, and a worldwide, non-exclusive, sublicensable license to develop and commercialize products containing such antibodies incorporating such technologies for all uses, including the treatment, palliation, diagnosis and prevention of human or animal diseases, disorders or conditions. We are obligated to use commercially reasonable efforts to develop and commercialize an antibody product that incorporates Xencor’s licensed technologies, for each of the influenza A and HBV research programs. These technologies are used in tobevibart, incorporating Xencor’s Xtend.

In consideration for the grant of the license, we paid Xencor an upfront fee. For each of the influenza A and HBV research programs, we will be required to pay Xencor development and regulatory milestone payments of up to $17.8 million in the aggregate and commercial sales milestone payments of up to $60.0 million in the aggregate, for a total of up to $77.8 million in aggregate milestones for each program and $155.5 million in aggregate milestones for both programs. On a product-by-product basis, we will also be obligated to pay tiered royalties based on net sales of licensed products ranging from low- to mid-single-digits. The royalties are payable, on a product-by-product and country-by-country basis, until the expiration of the last to expire valid claim in the licensed patents covering such product in such country.

The 2019 Xencor Agreement will remain in force, on a product-by-product and country-by-country basis, until the expiration of all royalty payment obligations. We may terminate the agreement in its entirety, or on a target-by-target basis, for convenience upon 60 days’ written notice. Either party may terminate the agreement for the other party’s uncured material breach upon 60 days’ written notice (or 30 days in the case of non-payment) or in the event of bankruptcy of the other party immediately upon written notice. Xencor may terminate the agreement immediately upon written notice if we challenge, or upon 30 days’ written notice if any of our sublicensees challenge the validity or enforceability of any patent licensed to us under each respective agreement.

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Amended and Restated Letter Agreement with the Gates Foundation

In January 2022, we entered into an amended and restated letter agreement with the Gates Foundation (formerly known as the Bill & Melinda Gates Foundation, and the agreement, the Gates Agreement), which amended and restated the original letter agreement with the Gates Foundation that we entered into in December 2016. In connection with the Gates Agreement, the Gates Foundation purchased $10.0 million of shares of our Series A-1 convertible preferred stock in December 2016, $10.0 million of shares of our Series B convertible preferred stock in January 2019 and $40.0 million of shares of our common stock in January 2022. We are obligated to use the proceeds of the Gates Foundation’s January 2022 investment in furtherance of its charitable purposes to develop our vaccinal antibody program, in each case for use in specified developing countries. We agreed to use reasonable efforts to achieve specified research and development milestones with respect to our vaccinal antibody program, and, if requested by the Gates Foundation and agreed by us, on further development of such programs beyond stated milestones. Additionally, we are bound by specified global access commitments including a commitment to provide any products developed using the proceeds of the Gates Foundation’s investment at an affordable price to the people most in need within the specified low- and middle-income countries, not to exceed a specified percentage over our fully burdened manufacturing and sales costs. As of December 31, 2025, the Company had stock purchase premium liability of $9.3 million, which will be recognized as we advance the development of our vaccinal antibody program with the Gates Foundation.

If we fail to comply with (i) our obligations to use the proceeds of the Gates Foundation’s investment for the purposes described in the paragraph above and to not use such proceeds for specified prohibited uses, (ii) specified reporting requirements or (iii) specified applicable laws, or if we materially breach our specified global access commitments (any such failure or material breach, a Specified Default), we will be obligated to redeem or arrange for a third party to purchase all of our stock purchased by the Gates Foundation under the Gates Agreement at the Gates Foundation’s request, at a price equal to the greater of (a) the original purchase price or (b) the fair market value, such redemption or sale, a Gates Foundation Redemption. Following a Gates Foundation Redemption, if a sale of the company or all of our material assets relating to the Gates Agreement occurs prior to the six month anniversary of the first redemption or sale of any stock in such Gates Foundation Redemption, then the Gates Foundation will receive compensation equal to the excess of what it would have received in such transaction if it still held the stock redeemed or sold at the time of such sale transaction over what it actually received in the Gates Foundation Redemption. Additionally, if a specified default occurs, if we are unable or unwilling to continue the vaccinal antibody program or, if applicable, any mutually agreed additional program (except for scientific or technical reasons), or if we institute bankruptcy or insolvency proceedings, then the Gates Foundation will have the right to exercise a non-exclusive, fully-paid license (with the right to sublicense) under our intellectual property to the extent necessary to use, make and sell products arising from such programs, in each case solely to the extent necessary to benefit people in specified low- and middle-income countries (as defined in the Gates Agreement) in furtherance of the Gates Foundation’s charitable purpose.

In the event that we sell, exclusively license, or transfer to a third party all or substantially all of our assets, the technology platform, or products arising from programs that are funded using the proceeds of the Gates Foundation’s investment, such third party is required to assume our specified global access commitments on terms that are reasonably acceptable to the Gates Foundation. Additionally, we will not grant any third party any rights or enter into any agreement with any third party that would restrict the Gates Foundation’s rights with respect to our specified global access commitments unless such third party expressly assumes such commitments to the reasonable satisfaction of the Gates Foundation. The global access commitments will continue for as long as the Gates Foundation continues to be a charitable entity.

In relation to the agreements discussed above, we have entered into various grant agreements with the Gates Foundation, to support our HIV vaccine program, TB vaccine program, HIV vaccinal antibody program and malaria vaccinal antibody program. During the year, all of the grant agreements expired except for the HIV vaccine program, for which the term expires in June 2027. The remaining grant agreement may be terminated early by the Gates Foundation for our breach, failure to progress the applicable funded projects, in the event of our change of control, change in our tax status, or significant changes in our leadership that the Gates Foundation reasonably believes may threaten the success of the applicable project.

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Sales and Marketing

Given our stage of development, we have not yet established a meaningful commercial (sales or marketing) organization, nor distribution capabilities. We intend to build a commercial infrastructure to support the sales and marketing of our product candidates, if approved, including tobevibart and elebsiran for the treatment of CHD. We expect to manage sales, marketing and distribution through internal resources and third-party relationships, including with Norgine with respect to commercialization of the combination of tobevibart and elebsiran for the treatment of CHD patients in the Norgine Territory. While we may commit significant financial and management resources to commercial activities for tobevibart and elebsiran and our broader portfolio, we will also consider collaborating with one or more biopharmaceutical companies to enhance our commercial capabilities going forward, as we have with the exclusive license granted to Norgine.

Manufacturing

We manufacture product candidates for three therapeutic modalities: mAbs, masked TCEs and siRNA. We have established our own internal process, analytical and pharmaceutical development, manufacturing, supply chain and quality organizations that work with our selected CDMOs, to develop, manufacture, test and supply our early- and late-stage product candidates developed with our proprietary and external technology platforms. Contract development and manufacturing of our antibody, TCE and siRNA product candidates is supported at our San Francisco, California, corporate headquarters for process, analytical and formulation development, small-scale non-current Good Manufacturing Practice (cGMP) manufacturing for preclinical studies. Our headquarters also conducts cell line development for our antibody and TCE product candidates.

We have established relationships with multiple CDMOs and have produced material to support preclinical studies and Phase 1, Phase 2 and Phase 3 clinical trials. Material for any Phase 3 clinical trials and commercial supply will generally require large-volume, low-cost-of-goods production. However, there are no assurances that our manufacturing and supply chain infrastructure will remain uninterrupted and reliable, or that the third parties we rely on to manufacture our products will be able to satisfy demand in a timely manner or not have supply chain disruptions, stock-outs due to raw material shortages, extended lead times, and/or greater than anticipated demand or quality issues.

Manufacturing Technology Platforms

Antibody

We currently leverage the antibody process platforms and manufacturing facilities of our CDMOs and strategic collaborators for development, manufacturing and supply of our preclinical, clinical and future commercial mAb product candidates. These manufacturing platforms are based on mAb technology and industrial processes that have been optimized, standardized and well-established across the biopharmaceutical industry over the last 30 years to enable process portability between biomanufacturing facilities and manufacturing with high success rates at most biologic CDMOs, as well as the partnered use of excess capacity with other biopharmaceutical companies. We established in-house capabilities in our San Francisco headquarters for mAb cell line development, Phase 1/2 process development, and small-scale drug substance and drug product manufacturing to produce non-cGMP material for preclinical studies. Our new process development laboratory was successfully brought online in 2024.

T-Cell Engager - PRO-XTEN®

We have also established process, analytical and formulation development capabilities for our E. coli -derived TCEs in our San Francisco facility. The manufacturing processes for TCE drug substances (DS) and drug products (DP) have been developed by our scientists based on standard E. coli manufacturing and pharmaceutical processes that have been well-established across the biopharmaceutical industry for other biologics. Similar to our antibody programs, we leverage the E.coli process platforms and manufacturing facilities of our CDMOs and strategic collaborators for further development and optimization, manufacturing and supply of our preclinical, clinical and future E.coli TCE product candidates.

siRNA

Vir Bio licensed and conducted a technology transfer of the siRNA DS and DP process for elebsiran. Similarly, we rely on the siRNA process platforms and manufacturing facilities of our CDMOs and strategic collaborators for further development, optimization, manufacturing and supply of our siRNA product candidate.

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Manufacturing Agreements

In 2024, we and a large CDMO entered into various scopes of work and continue to do so with the respect to process performance qualification (PPQ) for tobevibart DS (the Tobevibart Agreements). Under the terms of these agreements, the CDMO has reserved these manufacturing slots and will manufacture the agreed upon number of batches in accordance with an agreed upon manufacturing schedule to successfully complete PPQ. Future commercial supply will be subject to finalizing a commercial supply agreement and relevant terms by the end of 2026.

In 2024, we entered into binding commitments with a large CDMO for process characterization and manufacture through completion of PPQ of elebsiran DS (the Elebsiran Agreements). Under the terms of these agreements, the CDMO has reserved these manufacturing slots and will manufacture the agreed upon number of batches in accordance with the agreed upon manufacturing schedule to successfully complete PPQ. Future commercial supply will be subject to finalizing a commercial supply agreement and relevant terms in 2026. As of December 31, 2025, we had unaccrued unpaid commitments of approximately $24 million under the Tobevibart Agreements and Elebsiran Agreements.

For TCEs, we have agreements with CDMOs to manufacture our DS and DP for clinical trials on a yearly basis with commitments through 2028. In 2025, we entered into binding commitments with a CDMO for manufacture of our TCE products. As of December 31, 2025, we had unaccrued unpaid commitments of approximately $20 million for various TCE programs.

Competition

The pharmaceutical industry is characterized by rapidly advancing technologies, intense competition and a strong emphasis on proprietary products. While we believe that our technology, the expertise of our executive and scientific team, research, clinical capabilities, development experience and scientific knowledge provide us with competitive advantages, we face increasing competition from many different sources, including pharmaceutical and biotechnology companies, academic institutions, governmental agencies and public and private research institutions. Product candidates that we successfully develop and commercialize may compete with existing therapies and new therapies that may become available in the future.

Many of our competitors, either alone or with their collaborators, have significantly greater financial resources, established presence in the market, expertise in research and development, manufacturing, preclinical and clinical testing, obtaining regulatory approvals and reimbursement and marketing approved products than we do. These competitors also compete with us in recruiting and retaining qualified scientific, sales, marketing and management personnel, establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or potentially 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. Additional mergers and acquisitions may result in even more resources being concentrated in our competitors.

Our commercial potential could be reduced or eliminated if our competitors develop and commercialize products that are safer, more effective, have fewer or less severe side effects, are more convenient or are less expensive than products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for ours, which could result in our competitors establishing a strong market position before we are able to enter the market or make our development more complicated. The key competitive factors affecting the success of all of our programs are likely to be efficacy, safety, convenience, and cost/access.

HDV

There are currently no FDA-approved treatments for CHD. Gilead’s bulevirtide is approved for use by the EMA. Gilead has refiled for bulevirtide with the FDA and has announced that they expect a U.S. launch in the first half of 2026 should bulevirtide be approved by the FDA. Bulevirtide has led to limited HDV clearance and requires daily injections to maintain viral suppression. Mirum recently acquired Bluejay Therapeutics and their pipeline asset, brelovitug, which is currently in pivotal trials. Additionally, there are two known small pharmaceutical companies developing programs with various mechanisms of action, including Huahui Health and Assembly Biosciences (in partnership with Gilead).

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Prostate Cancer

Novartis’ lutetium Lu 177 vipivotide tetraxetan is the only currently approved PSMA-targeted therapy for prostate cancer. There are a number of PSMA therapies in development for prostate cancer including TCEs (e.g., Janux’s JANX007), ADC’s (e.g., Johnson & Johnson’s JNJ-8177) and other mechanisms of action from various companies, including Regeneron, GSK, and Bayer, among others. Beyond PSMA-targeted therapies, there are other clinical development programs focused on other prostate cancer targets (STEAP1, KLK2, B7-H3, etc.) utilizing various mechanisms of action that are sponsored by various companies, including J&J, Amgen, Novartis, Merck (MSD), Pfizer, and AstraZeneca, among others.

HER2-Expressing Solid Tumors

There are several HER2 therapies currently approved and in development for HER2-expressing solid tumors. For HER2 positive breast cancer, there are a number of approved drugs including ADCs (e.g. AstraZeneca’s and Daiichi Sankyo’s trastuzumab deruxtecan, Roche’s trastuzumab emtansine); monoclonal antibodies (e.g. Roche’s trastuzumab & pertuzumab); and inhibitors (e.g. Pfizer's tucatinib). Outside of HER2 positive breast cancer, there are other companies evaluating HER2 therapies in HER2-expressing solid tumors with various mechanisms of action including AstraZeneca, Daiichi Sankyo, Pfizer, Remegen, Jazz, BioNTech, Duality Bio, Hengrui Pharma, Adagene among others. Beyond HER2 therapies, companies are also developing programs targeting other tumor targets (non-HER2) that could also compete in HER2-expressing solid tumors.

EGFR-Expressing Solid Tumors

There are several EGFR therapies currently approved and in development for EGFR-expressing solid tumors. For colorectal cancer, EGFR-targeting mAbs including Lilly’s cetuximab and Amgen’s cetuximab are currently approved globally. Outside of colorectal cancer, there are also other companies evaluating EGFR therapies in EGFR-expressing solid tumors with various mechanisms of action including Janux, Regeneron, J&J, Genmab, Bicara, BMS, SystImmune, Affimed, AstraZeneca and others. Beyond EGFR therapies, companies are also developing programs targeting other tumor targets (non-EGFR) that could also compete in EGFR-expressing solid tumors.

Intellectual Property

Our intellectual property is critical to our business and we strive to protect it, including by obtaining and maintaining patent protection in the United States and internationally for our product candidates, new therapeutic approaches and potential indications, and other inventions that are important to our business. Our policy is to seek to protect our proprietary and intellectual property position by, among other methods, filing U.S. and foreign patent applications related to our proprietary technology, inventions and improvements that are important for the development and implementation of our business. We also rely on the skills, knowledge, and experience of our scientific and technical personnel, as well as that of our advisors, consultants, and other contractors. To help protect our proprietary know-how that is not patentable, we rely on confidentiality agreements to protect our interests. We require our employees, consultants and advisors to enter into confidentiality agreements prohibiting the disclosure of confidential information and requiring disclosure and assignment to us of the ideas, developments, discoveries and inventions important to our business.

Our patent portfolio includes patents and patent applications that are licensed from several collaborators and other third parties, including Sanofi, Alnylam, IRB, Rockefeller and Xencor, and patents and patent applications that are owned by us. Our patent portfolio includes patents and patent applications that cover our product candidates elebsiran, tobevibart, VIR-5500, VIR-5818, and VIR-5525, and the use of these candidates for therapeutic purposes. Our proprietary technology has been developed primarily through in-licenses, acquisitions, relationships with academic research centers, and contract research organizations (CROs).

For our product candidates, we will, in general, initially pursue patent protection covering compositions of matter and methods of use. Throughout the development of our product candidates, we seek to identify additional means of obtaining patent protection that would potentially enhance commercial success, including through additional methods of use, process of making, formulation and dosing regimen-related claims.

In total, our patent portfolio, including patents licensed from our collaborators and other third parties, comprises over 90 different patent families as of December 31, 2025, filed in various jurisdictions worldwide. Our patent portfolio includes over 1,500 active cases with over 690 issued patents in the United States and abroad. Our patent portfolio for our product candidates and technology platforms is outlined below.

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Patents and Proprietary Rights

U.S. and European Patent Expiration

We have a number of U.S. and foreign patents, patent applications and rights to patents related to our molecules, products and technology, but we cannot be certain that issued patents will be enforceable or provide adequate protection or that pending patent applications will result in issued patents.

The following table shows the estimated expiration dates (including patent term extensions, supplementary protection certificates and/or pediatric exclusivity where granted) in the United States and the European Union for the primary patents for our key product candidates as described above. Dates in parentheses reflect the estimated expiration date of patents which may issue from currently pending applications. The estimated expiration dates do not include any potential additional exclusivity (e.g., patent term extension, supplementary protection certificates or pediatric exclusivity) that have not yet been granted.

Key Product CandidatesPatent Expiration

U.S.E.U.

HBV/HDV

Elebsiran (VIR-2218)
20392039

Tobevibart (VIR-3434)
20422039

ONCOLOGY

VIR-5818

2041

(2041)

VIR-5525
(2044)(2044)

VIR-5500
2044
(2044)

Platform Patent Portfolio by Technology Platform

Antibody Platform

Licensed Patents

We have exclusively licensed a patent family from Rockefeller. The 20-year term of any patents issuing from the application in this family is presently estimated to expire in 2038, absent any available patent term adjustments or extensions.

We have exclusively licensed from IRB two patent families that relate to our antibody platform technology. The 20-year term of the first of these families expired in 2024. The US patent in this family is, however, still in force as its term was extended until 2027 due to patent office delay. The 20-year term of the issued patents and any patent issuing from the pending patent applications in the second patent family is estimated to expire in 2038, absent any available patent term adjustments or extensions.

In addition, we have non-exclusively licensed a group of patents and applications from Xencor. The 20-year term of these patents and applications if granted is presently estimated to expire between 2024 and 2028, absent any available patent term adjustments or extensions.

Patents Owned by Us

We also own, with our subsidiary Humabs, one patent family that includes, as of December 31, 2025, 33 pending applications in both the US and abroad. These applications include composition of matter claims, pharmaceutical composition claims, method of treatment claims, and composition for use in treatment claims. The 20-year term of any patents issuing from patent applications in this family is presently estimated to expire in 2042, absent any available patent term adjustments or extensions.

PRO-XTEN® Platform

Licensed Patents

We have exclusively licensed from Sanofi 13 different patent families related to our PRO-XTEN® portfolio.

The 20-year term of the issued patents in these families is presently estimated to expire between 2036 and 2041, absent any available patent term adjustments or extensions.

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Patent Term and Term Extensions

Individual patents have terms for varying periods depending on the date of filing of the patent application or the date of patent issuance and the legal term of patents in the countries in which they are obtained. Generally, utility patents issued for applications filed in the United States are granted a term of 20 years from the earliest effective filing date of a non-provisional patent application. In addition, in certain instances, the term of a U.S. patent can be extended to recapture a portion of the delay from the U.S. Patent and Trademark Office (USPTO) in issuing the patent, as well as a portion of the term effectively lost as a result of the FDA regulatory review period. However, as to the FDA component, the restoration period cannot be longer than five years, and the restoration period cannot extend the patent term beyond 14 years from FDA approval. In addition, only one patent applicable to an approved drug is eligible for the extension, and only those claims covering the approved drug, a method for using it, or a method of manufacturing may be extended. The duration of foreign patents varies in accordance with provisions of applicable local law, but typically is also 20 years from the earliest effective filing date. All taxes, annuities or maintenance fees for a patent, as required by the USPTO and various foreign jurisdictions, must be timely paid in order for the patent to remain in force during this period of time.

The actual protection afforded by a patent may vary on a product by product basis, from country to country, and can depend upon many factors, including the type of patent, the scope of its coverage, the availability of regulatory-related extensions and the availability of legal remedies in a particular country and the validity and enforceability of the patent.

Patent Protection and Certain Challenges

Patents and other proprietary rights are very important to our business. If we have a properly drafted and enforceable patent, it can be more difficult for our competitors to use our technology to create competitive products and more difficult for our competitors to obtain a patent that prevents us from using technology we create. As part of our business strategy, we actively seek patent protection both in the United States and internationally and file additional patent applications, when appropriate, to cover improvements in our molecules, products and technology.

Patents covering certain of our products are held by third parties. We acquired exclusive rights to these patents in the agreements we have with these parties.

We may obtain patents for certain products many years before marketing approval is obtained. Because patents have a limited life that may begin to run prior to the commercial sale of the related product, the commercial value of the patent may be limited. However, we may be able to apply for patent term extensions or supplementary protection certificates in some countries. For example, extensions for the patents or supplementary protection certificates on many of our products have been granted in the United States and in several European countries, compensating in part for delays in obtaining marketing approval. Similar patent term extensions may be available for other products we are developing, but we cannot be certain we will obtain them in some countries.

It is also important that we do not infringe the valid patents of third parties. If we infringe the valid patents of third parties, our reputation may be harmed and we may be required to pay significant monetary damages, we may be prevented from commercializing products, or we may be required to obtain licenses from these third parties. We may not be able to obtain alternative technologies or any required license on reasonable terms or at all. If we fail to obtain these licenses or alternative technologies, we may be unable to develop or commercialize some or all of our products.

Because patent applications are confidential for a period of time until a patent is issued, we may not know if our competitors have filed patent applications for technology covered by our pending applications or if we were the first to invent or first to file an application directed toward the technology that is the subject of our patent applications. Competitors may have filed patent applications or received patents and proprietary rights that block or compete with our products. In addition, if competitors file patent applications covering our technology, we may have to participate in litigation, post-grant proceedings before the USPTO or other proceedings to determine the right to a patent or validity of any patent granted.

Future litigation or other proceedings regarding the enforcement or validity of our existing patents, or any future patents could result in the invalidation of our patents or substantially reduce their protection.

Our pending patent applications and patent applications filed by our collaborative partners may not result in the issuance of any patents or may result in patents that do not provide adequate protection. As a result, we may not be able to prevent third parties from developing compounds or products that are closely related to those which we have developed or are developing. In addition, certain countries do not provide effective enforcement of our patents, and third-party manufacturers may be able to sell generic versions of our products in those countries. For more information, see the section titled “Risk Factors—Risks Related to Our Intellectual Property.”

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Trademarks and Know-How

In connection with the ongoing development and advancement of our products and services in the United States and various international jurisdictions, we seek to create protection for our marks and enhance their value by pursuing trademarks and service marks where available and when appropriate. In addition to patent and trademark protection, we rely upon know-how and continuing technological innovation to develop and maintain our competitive position. We seek to protect our proprietary information, in part, by using confidentiality agreements with our commercial partners, collaborators, employees and consultants, and invention assignment agreements with our employees and consultants. These agreements are designed to protect our proprietary information and, in the case of the invention assignment agreements, to grant us ownership of technologies that are developed by our employees and through relationships with third parties. For more information, see “