FDA greenlights Hympavzi for underserved hemophilia populations

FDA has expanded the indication for Hympavzi (marstacimab-hncq) to include patients aged 12 years and older with hemophilia A or B who have developed inhibitors to factor replacement therapy, as well as children aged 6 to 11 years with hemophilia A or B, with or without inhibitors.

The approval addresses important unmet needs in hemophilia care. Patients who develop inhibitors to factor VIII or factor IX replacement therapy often have limited treatment options because standard factor replacement may no longer effectively prevent or control bleeding episodes. In younger children, treatment burden can be substantial because of the challenges associated with IV therapy and venous access.

Hympavzi is a once-weekly subcutaneous anti–tissue factor pathway inhibitor therapy that doesn't require routine treatment-related laboratory monitoring. The expanded indication also makes Hympavzi the first subcutaneous non-factor therapy available for children aged 6 to 11 years with hemophilia B, a population with limited treatment options beyond factor replacement.

Clinical trial data from the phase 3 BASIS and BASIS KIDS studies supported the expanded indication. In adolescents and adults with inhibitors, Hympavzi reduced mean treated annualized bleeding rates by 93% compared with on-demand treatment using bypassing agents. Pediatric data showed low annualized bleeding rates in children with and without inhibitors, including those previously receiving on-demand therapy.

The most commonly reported adverse reactions included injection-site reactions, headache, pyrexia, arthralgia, diarrhea, pruritus, and rash. Thromboembolic events have been observed and are included in the prescribing information warnings and precautions.

“For children who have to deal with bleeding episodes from an early age and for people living with hemophilia who develop inhibitors, treatment options have been limited and are often burdensome,” said Guy Young, MD, director of the Hemostasis and Thrombosis Center at Children's Hospital Los Angeles. “A treatment that can reduce bleeding with straightforward, once-weekly administration has the potential to fundamentally change how patients and caregivers approach this disease.”

Source: Pfizer. 2026 June 8. [Press release]. U.S. FDA Approves Pfizer's Hympavzi for the Treatment of Two Additional Hemophilia A or B Patient Populations with Significant Medical Need