Hympavzi now approved for more hemophilia patients in Europe

The European Commission has approved Hympavzi (marstacimab) to treat certain people with hemophilia A or hemophilia B who have inhibitors, the therapy’s maker, Pfizer, announced.

Hympavzi was approved in Europe in 2024 to treat patients with hemophilia A or B ages 12 and older who weigh at least 35 kg (77 pounds) and do not have inhibitors, antibodies that can reduce the efficacy of standard hemophilia treatments. The commission’s expanded approval covers all patients in this age and weight range, regardless of inhibitor status. The approval applies in all 27 member states of the European Union as well as in Iceland, Liechtenstein, and Norway.

“This approval brings a once-weekly medicine to the EU that meets a critical need for patients who face a treatment journey that can be complex and challenging with limited options available today, representing the latest step in Pfizer’s more than 40-year commitment to advancing care for people living with hemophilia,” Alexandre de Germay, chief international commercial officer and executive vice president at Pfizer, said in a company press release.

Hemophilia encompasses a group of genetic disorders marked by a deficiency of certain clotting proteins: clotting factor VIII in hemophilia A and clotting factor IX in hemophilia B. Standard treatment involves factor replacement therapy, in which a functional version of the deficient protein is administered to the body. But some patients develop antibodies against the replacement therapy. These are known as inhibitors, because they prevent the replacement treatment from working properly.

“Inhibitors present a substantial challenge for people living with hemophilia as they neutralize traditional factor replacement therapies, in turn limiting treatment options and leaving patients vulnerable to uncontrolled bleeding episodes,” said Laurent Frenzel, MD, PhD, head of the Hemophilia Treatment and Research Center at the Necker-Enfants Malades Hospital in Paris.

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Hympavzi works by blocking the activity of tissue factor pathway inhibitor (TFPI), a protein that normally helps prevent unneeded clotting. By inhibiting this protein, the therapy aims to make blood more prone to clotting, thus counteracting the defect of clotting proteins that drives hemophilia. Hympavzi is administered once weekly via a subcutaneous (under-the-skin) injection.

The new European approval was based primarily on data from the Phase 3 BASIS clinical trial (NCT03938792), which tested the therapy in people with hemophilia A or B aged 12 and older, with and without inhibitors. Results from the year-long study showed that preventive treatment with Hympavzi decreased average annual bleeding rates by more than 90% compared with rates observed during on-demand treatment alone. Patients also reported improvements in life quality after starting Hympavzi.

Patients who completed the BASIS study could enter an open-label extension study (NCT05145127) in which they receive Hympavzi for several more years. Interim data, covering more than four years of Hympavzi treatment, showed the median annual bleeding rate was zero; in other words, most patients did not have any reported bleeds.

“The approval of Hympavzi offers adults and adolescents in the EU a once-weekly subcutaneous option that has demonstrated the ability to reduce bleeding episodes and maintain bleed reduction based on observation to date in a long-term extension study,” Frenzel said.

Safety data from inhibitor-positive patients were generally consistent with the therapy’s known profile. Common side effects of Hympavzi include itching, injection site reactions, and headache; the therapy is also known to increase the risk of clot-related complications.

In the U.S., Hympavzi is approved for hemophilia A or B patients aged 12 and older who are inhibitor-negative. Pfizer recently submitted an application asking the U.S. Food and Drug Administration (FDA) to expand approval for patients regardless of inhibitor status, and to authorize the therapy for patients as young as 6. The FDA granted that application priority review, and a decision is expected by the end of June.

“We look forward to working with regulators globally to continue bringing Hympavzi to those who can benefit from it,” de Germay said.