U.S. FDA Approves Pfizer?s HYMPAVZI for the Treatment of Two Additional Hemophilia A or B Patient Populations with Significant Medical Need

Pfizer Inc. announced that the U.S. Food and Drug Administration (FDA) has approved an expanded indication for HYMPAVZI® (marstacimab-hncq) to include the treatment of patients with hemophilia A or B 12 years and older with inhibitors and pediatric patients (ages 6 to 11 years) with or without inhibitors. HYMPAVZI is now indicated in the U.S. for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in adults and pediatric patients 6 years of age and older with hemophilia A (congenital factor VIII deficiency) with or without factor VIII inhibitors, or hemophilia B (congenital factor IX deficiency) with or without factor IX inhibitors. HYMPAVZI offers a combination of prophylactic bleed protection with a straightforward, once-weekly subcutaneous administration that does not require routine treatment-related lab monitoring.

Hemophilia is typically diagnosed in early childhood and impacts more than 800,000 people worldwide. The inability of the blood to clot properly can increase the risk of painful bleeding, including inside the joints, which can cause joint scarring and damage. Children?s joints have growing cartilage and bone, which makes them particularly susceptible to damage caused by repeated bleeding episodes.

Inhibitors to factor replacement therapy limit treatment options for people living with hemophilia and are associated with an increased risk of uncontrolled bleeding.5 These inhibitory antibodies develop in approximately 20% of those with hemophilia A and 3% of those with hemophilia B. Many people living with inhibitors to FVIII and FIX are unable to continue taking factor replacement therapies as they no longer prevent or stop bleeding episodes, particularly in individuals who are refractory to immune tolerance induction therapy. Results from the Phase 3 BASIS trial (NCT03938792) supported the approval of HYMPAVZI in adults and adolescents 12 years and older with hemophilia A or B with inhibitors. The results demonstrated the superiority of HYMPAVZI in improving key bleeding outcomes including significantly reducing mean treated annualized bleeding rate (ABR) by 93% compared to on-demand (OD) intravenous treatment with bypassing agents (1.4 [95% CI: 0.9-2.3] vs.19.8 [95% CI: 16.1-24.3]; p<0.0001).

Interim results from the Phase 3 BASIS KIDS trial (NCT05611801) supported the approval of HYMPAVZI in children ages 6 to 17 years with hemophilia A or B with or without inhibitors. Descriptive analyses, which summarize trends in the data, in patients who received HYMPAVZI demonstrated: In children ages 6 to 17 years old without inhibitors, a mean treated ABR of 1.8 (99% CI: 1.1-2.6) was observed in patients who received HYMPAVZI compared to a historical model-based mean ABR of treated bleeds of 3.6 (99% CI: 1.3-5.8) in patients who received routine prophylaxis In children 6 to 17 years old with inhibitors, a mean treated ABR of 1.4 (99% CI: 0.5-4.5) was observed in patients who received HYMPAVZI compared to a historical model-based mean ABR of treated bleeds of 18.9 (99% CI: 14.2, 25.2) in patients who received OD therapy In children 6 to 11 years old with inhibitors who were previously on OD therapy or without inhibitors who were previously receiving routine prophylaxis, respectively, a model-based mean treated ABR of 1.3 and 1.4 and a median ABR of 1.0 and 1.0 were observed. The most commonly reported adverse reactions (=2%) in adult and pediatric patients 6 years of age and older with or without inhibitors were injection site reaction, headache, pyrexia, arthralgia, diarrhea, pruritus, and rash.

Thromboembolic events (venous and arterial) in two patients were observed among a total of 259 patients who received HYMPAVZI in the open-label extension study. Thromboembolic events, hypersensitivity, embryofetal toxicity, and increased laboratory values of fibrin D-dimer and prothrombin fragment 1.2 are noted within the Warnings and Precautions section of the U.S. label. This HYMPAVZI application was reviewed under FDA Priority Review, which is granted to medicines that treat a serious condition and provide a significant improvement in safety or effectiveness over available therapy.

The FDA also granted HYMPAVZI Breakthrough Therapy Designation for routine prophylaxis to prevent or reduce the frequency of bleeding episodes in younger pediatric (=6 to <12 years of age) patients with hemophilia B with and without inhibitors. The FDA?s Breakthrough Therapy Designation is intended to expedite the development and review of medicines with the potential to treat a serious or life-threatening disease when preliminary clinical evidence indicates the medicine may demonstrate substantial improvement on a clinically significant endpoint over available therapies.