Star Therapeutics Presents Interim Data from Phase 1/2 Multidose Study of VGA039 in Von Willebrand Disease, Demonstrating Substantial Bleed Reductions in All Patients, at ASH Annual Meeting

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SOUTH SAN FRANCISCO, Calif.--(BUSINESS WIRE)--Dec 6, 2025--

Star Therapeutics, a late clinical-stage biotechnology company discovering and developing best-in-class antibodies for bleeding disorders and other diseases, today announced interim data from its ongoing Phase 1/2 multidose study of VGA039 in von Willebrand disease (VWD). The data are being presented in an oral session at the 67 th American Society of Hematology (ASH) Annual Meeting and Exposition in Orlando, Florida. VGA039 is a first-in-class monoclonal antibody therapy that targets Protein S, with dual actions promoting platelet attachment and enhancing fibrin deposition to restore hemostasis.

In the Phase 1/2 multidose study, treatment with VGA039 administered subcutaneously once monthly resulted in a substantial reduction in annual bleeding rate (ABR) across all types of VWD and all types of bleeds, including meaningful improvement in bleed control for patients switching from prior von Willebrand factor (VWF)-containing intravenous (IV) prophylaxis. The study population includes patients with Types 1, 2, and 3 VWD who have high disease burden, including patients with serious gastrointestinal (GI) and hemophilia-like joint and muscle bleeds.

“The data presented at ASH indicate that VGA039 could be transformative for people living with VWD, a condition with more than 130,000 diagnosed patients in the U.S. alone,” said Allison Wheeler, M.D., MSCI, Associate Professor of Pediatrics at the University of Washington. “VWD can have a significant impact on quality of life, with patients experiencing frequent and severe bleeds that can require hospitalization. Current treatment options remain limited, with VWF-containing prophylaxis requiring multiple IV infusions per week. Data from the multidose trial support a once monthly subcutaneous dosing regimen for VGA039, which could meaningfully alleviate the current treatment burden with the potential for even better bleed control over the standard of care.”

Key highlights from the presentation include:

• As of November 14, 2025, interim data from all 16 patients enrolled in the Phase 1/2 multidose study were available, including safety data on all 16 patients and efficacy data on all 8 patients who had completed treatment with VGA039.
• VGA039 once monthly subcutaneous prophylaxis was safe and well tolerated.
• VGA039 demonstrated substantial reductions in ABR across all patients, with all types of VWD and all types of bleeds (including serious GI and hemophilia-like joint and muscle bleeds).
  • Bleed reductions were 73%-87% for all the participants enrolled who have the same ABR as the population being recruited into the Phase 3 trial (ABR ≥ 12, no prior IV prophylaxis).
  • In patients switching from prior VWF-containing prophylaxis (IV infusions multiple times per week), bleed reductions were 75%-100%, indicating potential efficacy and dosing improvement over standard-of-care.
• All participants to date who have completed the multidose study have transitioned to the open-label extension (OLE) study.

“This dataset is compelling, encompassing a diverse patient population across multiple VWD types, a full spectrum of bleed profiles, and individuals transitioning from prior prophylaxis regimens. VGA039’s ability to consistently reduce bleeding across these groups along with its favorable safety and tolerability profile indicate that VGA039 has the potential to improve outcomes for all patients with VWD,” said Steven Pipe, M.D., Professor of Pediatrics and Pathology at the University of Michigan. “Importantly, patients who transitioned from IV prophylaxis multiple times per week to once monthly subcutaneous VGA039 experienced marked improvements in bleed control, highlighting the potential to establish a new standard of care for people living with VWD.”

“These interim data provide further validation of VGA039 as a potential once monthly subcutaneous treatment for multiple bleeding disorders, starting with VWD. All patients to date have opted to continue treatment as part of our open-label extension study after finishing the multidose trial,” said Gary Patou, M.D., Chief Medical Officer of Star Therapeutics. “These data, along with the recent initiation of our pivotal Phase 3 study, VIVID-6, continue to add to the momentum surrounding this program, bringing us another step closer to achieving our mission of creating life-changing therapies for patients with bleeding disorders.”

About VGA039

VGA039 is a monoclonal antibody therapy with a novel mechanism of action that targets Protein S, with dual actions promoting platelet attachment and enhancing fibrin deposition to restore hemostasis. VGA039 has potential to be a universal hemostatic therapy that can treat numerous bleeding disorders, starting with von Willebrand disease (VWD). As a subcutaneously self-administered antibody therapy with a convenient once monthly dosing regimen, VGA039 has the potential to dramatically reduce treatment burden for patients. VGA039 has received Fast Track and orphan drug designations from the U.S. Food and Drug Administration (FDA). VGA039 has advanced into a Phase 3 study ( NCT07115004 ), VIVID-6, a global single arm cross-over study designed to investigate the safety and efficacy of subcutaneous administration of VGA039 as prophylaxis for bleeding in patients with every type of VWD. For additional information on our VIVID trials of VGA039, including how to enroll, please visit the website here.

About von Willebrand disease

Von Willebrand disease (VWD) is the most common inherited bleeding disorder in which the blood does not clot properly, caused by absent or defective von Willebrand factor (VWF). VWD patients may experience excessive bleeding with varying severity and frequency, negatively impacting their daily lives. Current therapies for VWD prophylaxis include factor replacement therapies requiring multiple intravenous (IV) infusions every week. More than 130,000 people in the U.S. are diagnosed with VWD.

About Star Therapeutics

Star Therapeutics is a late clinical-stage biotechnology company discovering and developing best-in-class antibodies for bleeding disorders and other diseases. The company applies its expertise in antibody innovation to interrogate areas of biology that have been overlooked and have the potential to address multiple diseases with a single therapy. Star’s leadership team has deep expertise in novel antibody drug development, having invented four first-in-class antibodies including the first approved drug (ENJAYMO ® ) for cold agglutinin disease, a hematology disease, and other therapies that are each in Phase 3 trials. Based in South San Francisco, Star has raised more than $300 million from leading life sciences investors. For more information, please visit Star-Therapeutics.com and follow us on LinkedIn and X.

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Star Therapeutics

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KEYWORD: CALIFORNIA UNITED STATES NORTH AMERICA

INDUSTRY KEYWORD: HEALTH CLINICAL TRIALS RESEARCH SCIENCE PHARMACEUTICAL CARDIOLOGY BIOTECHNOLOGY

SOURCE: Star Therapeutics

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PUB: 12/06/2025 04:00 PM/DISC: 12/06/2025 04:00 PM

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