FDA Approves New Hemophilia A or B Treatment

The U.S. Food and Drug Administration (FDA) has given the green light to a new medical treatment called Hympavzi (marstacimab-hncq). This drug is designed for the routine prevention of bleeding episodes in adult and pediatric patients aged 12 and older who have hemophilia A without factor VIII inhibitors or hemophilia B without factor IX inhibitors. This announcement was made on October 11, 2024, in Silver Spring, Md.

Ann Farrell, M.D., the director of the Division of Non-Malignant Hematology at the FDA’s Center for Drug Evaluation and Research, expressed optimism about the new approval. She highlighted that Hympavzi represents a novel treatment avenue for patients with hemophilia by targeting a specific protein involved in the blood clotting mechanism. According to Farrell, the approval of Hympavzi illustrates the FDA's dedication to fostering the development of innovative, safe, and effective therapeutic options.

Hemophilia A and B are hereditary disorders that result from the malfunction or absence of coagulation factors VIII (FVIII) or IX (FIX), respectively. These conditions hinder the blood’s ability to clot, leading to prolonged bleeding after injuries or surgeries. Additionally, spontaneous bleeding in muscles, joints, and internal organs can occur, posing significant health risks. Typically, these bleeding episodes are managed through either on-demand treatment or prophylactic measures using products containing FVIII or FIX, or products that mimic these factors.

Unlike traditional treatments, Hympavzi does not replace a clotting factor. Instead, it works by reducing the activity of the naturally occurring anticoagulant protein known as tissue factor pathway inhibitor. This action increases the production of thrombin, an essential enzyme in the clotting process, thus potentially lowering or preventing the occurrence of bleeding episodes.

The approval of Hympavzi was based on findings from an open-label, multi-center study that included 116 male patients with severe hemophilia A or B, both without inhibitors. During the initial six months of the study, patients were treated with either on-demand or prophylactic replacement factor. In the subsequent 12 months, they received Hympavzi prophylaxis. The primary metric for evaluating Hympavzi’s effectiveness was the annualized bleeding rates of treated bleeds.

Results from the study showed a significant reduction in bleeding rates for patients who transitioned from on-demand factor replacement to Hympavzi prophylaxis. Specifically, the estimated annualized bleeding rate dropped from 38 to 3.2. For those who initially received prophylactic factor replacement, the annualized bleeding rate decreased from 7.85 to 5.08 during the period they were on Hympavzi prophylaxis, indicating comparable bleeding rates.

However, Hympavzi is accompanied by warnings regarding the potential for blood clots, hypersensitivity reactions, and embryofetal toxicity. The most frequently reported side effects include reactions at the injection site, headaches, and itching.

The FDA has granted Hympavzi Orphan Drug designation, a status that provides certain benefits and incentives to encourage the development of drugs for rare diseases. Pfizer Inc. has been awarded the approval for this innovative treatment.

This approval marks a significant step forward in the treatment options available for individuals with hemophilia, offering a new approach that could improve the quality of life for many patients.