FDA may OK Hympavzi for children 6 and older with hemophilia A or B
Agency grants Pfizer’s request for priority review of expanded approval
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Pfizer said the U.S. Food and Drug Administration (FDA) will review the company’s request to expand approval of its preventive treatment Hympavzi (marstacimab) to cover all people with hemophilia A or B ages 6 and older.
Hympavzi is FDA-approved to treat hemophilia A and B in patients ages 12 and older who do not have inhibitors (antibodies that can interfere with standard hemophilia treatments). Pfizer is asking the agency to expand this approval for patients as young as 6, and to authorize Hympavzi for inhibitor-positive hemophilia A and B patients ages 6 and older.
The FDA granted Pfizer’s application priority review, which shortens the agency’s review time from the usual 10 months to about six months. Pfizer said it expects the FDA’s decision in the second quarter of this year.
“We believe Hympavzi has the potential to become a transformative option for these patients that have limited or burdensome treatment options today,” Michael Vincent, MD, PhD, chief inflammation and immunology officer at Pfizer, said in a company press release. “We look forward to progressing discussions with regulators to make this medicine available for patients.”
Hemophilia A and B are disorders marked by low levels of clotting proteins — factor VIII in hemophilia A and factor IX in hemophilia B. As a result, blood can’t clot correctly, leading to hemophilia symptoms like easy and prolonged bleeding.
‘Significant’ need for treatment alternatives
Standard treatment for hemophilia generally involves factor replacement, in which a version of the defective clotting protein is administered. But some patients develop antibodies against the therapies. These antibodies are known as inhibitors because they can prevent the replacement therapies from working properly.
“There is a significant medical need for younger patients with hemophilia and for those who have developed inhibitors, which neutralize factor replacement therapies and render them ineffective,” Vincent said.
Instead of targeting the disease-causing defect, Hympavzi is designed to reduce the activity of tissue factor pathway inhibitor (TFPI), a protein that normally prevents unneeded clotting. By inhibiting TFPI, the therapy aims to make the blood more prone to clotting, thus normalizing clotting activity in both hemophilia A and B. The therapy is given by weekly subcutaneous (under-the-skin) injection.
Pfizer’s application seeking approval of Hympavzi for hemophilia A and B patients ages 12 and older with inhibitors is based mainly on findings from the Phase 3 BASIS clinical trial (NCT03938792). Inhibitor-positive patients in the trial reported reductions in bleeding rates and improvements in life quality after starting Hympavzi.
The company’s application seeking approval for children as young as 6 is based on data from an ongoing study called BASIS KIDS (NCT05611801), which is testing Hympavzi in children with hemophilia. If that application is approved, Hympavzi would be the only available non-factor replacement therapy for children ages 6 to 11 with hemophilia B.
“For children living with hemophilia A or B between ages 6 and 11, treatment approaches that prevent bleeds are particularly important to protect growing joints,” said Guy Young, MD, director of the hemostasis and thrombosis program at Children’s Hospital Los Angeles. “Hympavzi would address a critical unmet medical need for these patients and those with inhibitors if approved, particularly patients ages 6 to 11 with hemophilia B who do not have non-factor treatment options available today.”
