Star Therapeutics Receives FDA Rare Pediatric Disease and Breakthrough Therapy Designations for VGA039 in Von Willebrand Disease
Key Insights
The FDA has granted both rare pediatric disease designation and Breakthrough Therapy designation to Star Therapeutics (search)' VGA039, a once-monthly subcutaneous monoclonal antibody for von Willebrand disease (search) prophylaxis.
VGA039 targets Protein S with dual actions promoting platelet attachment and enhancing fibrin deposition, potentially serving as a universal hemostatic therapy for all types of von Willebrand disease (search).
The designations are supported by interim Phase 1/2 data presented at ASH 2025 showing substantial bleed reductions across all VWD types, with a pivotal Phase 3 trial currently enrolling patients aged 12 and older.
Star Therapeutics (search) announced that the U.S. Food and Drug Administration has granted both rare pediatric disease designation (RPDD) and Breakthrough Therapy designation (BTD) to VGA039, the company's investigational monoclonal antibody therapy for routine prophylaxis in patients with von Willebrand disease (search) (VWD). The dual designations underscore the significant unmet medical need for patients with VWD, the most common inherited bleeding disorder affecting more than 134,000 patients in the United States.
Novel Mechanism Targets Protein S
VGA039 represents a differentiated approach to treating bleeding disorders (search) through its novel mechanism of action targeting Protein S. The monoclonal antibody therapy employs dual actions that promote platelet attachment and enhance fibrin deposition to restore hemostasis. This mechanism positions VGA039 as a potential universal hemostatic therapy capable of treating numerous bleeding disorders, starting with all types of von Willebrand disease (search).
The therapy is designed as a once-monthly, subcutaneously self-administered treatment, offering a significant improvement in convenience compared to current standard therapies. Current VWD prophylaxis treatments include factor replacement therapies that require multiple intravenous infusions every week, creating a substantial treatment burden for patients.
Regulatory Milestones Build on Previous Designations
The FDA's rare pediatric disease designation is intended to encourage development of therapies for serious or life-threatening rare diseases that primarily affect individuals aged 18 years or younger and impact fewer than 200,000 people in the U.S. Upon approval of a Biologics License Application, this designation makes Star Therapeutics (search) eligible to receive a Priority Review Voucher, which may be redeemed for priority review of a subsequent marketing application or transferred to another sponsor. According to the National Organization for Rare Disorders, approximately 63 rare pediatric disease Priority Review Vouchers had been awarded across 47 conditions as of 2025 since the program began in 2012.
The Breakthrough Therapy designation builds upon the Fast Track designation that VGA039 received in 2025. The BTD aims to expedite the development and review of therapies intended to treat serious conditions and address unmet medical needs.
Clinical Evidence Supports Regulatory Recognition
The FDA's designations are supported by interim data from the Phase 1/2 multidose study of VGA039 in adult and adolescent patients with VWD. These data were presented at the 67th American Society of Hematology Annual Meeting and Exposition in December 2025, demonstrating substantial bleed reductions across all types of VWD and all types of bleeds.
"People living with VWD may face serious health complications, including frequent bleeding and hospitalizations that can significantly impact their quality of life," said Gary Patou, M.D., Chief Medical Officer of Star Therapeutics (search). "The FDA's decision to grant both RPDD and BTD to VGA039 underscores the urgent need for new treatments for these patients, as well as Star's potential to make a meaningful difference."
Phase 3 Trial Currently Enrolling
VGA039 has advanced into a Phase 3 study (NCT07115004), VIVID-6, a global single-arm crossover study designed to investigate the safety and efficacy of subcutaneous administration of VGA039 as prophylaxis for bleeding in patients with every type of VWD. The pivotal trial is currently enrolling adolescent and adult patients with VWD, specifically targeting people aged 12 and over with all types of the disease.
"VGA039 could be transformative for patients, as it is designed to prevent or reduce bleeding across all types of VWD while reducing treatment burden via its once monthly, subcutaneous dosing regimen," Patou noted. "We are excited to continue to partner with physicians, patients and advocacy organizations to enroll people aged 12 and over with all types of VWD in our ongoing, pivotal Phase 3 study evaluating VGA039 prophylaxis."
Addressing Significant Unmet Need
Von Willebrand disease (search) is caused by low or defective von Willebrand factor (VWF), resulting in blood that does not clot properly. VWD patients may experience excessive bleeding with varying severity and frequency, negatively impacting their daily lives. The condition represents a serious and life-threatening disease where patients face frequent bleeding episodes and hospitalizations.
VGA039 has accumulated multiple FDA designations including Fast Track, orphan drug, rare pediatric disease, and Breakthrough Therapy designations, reflecting the regulatory agency's recognition of both the unmet medical need and the therapy's potential to address it. Star Therapeutics (search) aims to bring this new treatment to people with VWD as efficiently as possible through continued collaboration with physicians, patients, and advocacy organizations.