Labcorp announced the U.S. Food and Drug Administration (FDA) has approved its nAbCyte Anti-AAVRh74var HB-FE Assay, a companion diagnostic (CDx) to determine patient eligibility for treatment with BEQVEZ (fidanacogene elaparvovec-dzkt), Pfizer's recently FDA-approved hemophilia B gene therapy. The nAbCyte cell-based neutralizing antibody assay is a component of Pfizer's program to target recombinant adeno-associated virus (rAAV)-based gene therapies to the appropriate patient population. Before infusion with BEQVEZ, patients will require testing for preexisting anti-AAVRh74var antibodies.

Labcorp's nAbCyte cell-based neutralizing antibody assay will allow for the accurate detection of preexisting neutralizing antibodies (nAbs), which could impact patient safety and/or efficacy of the one-time treatment. An estimated 6,000 people in the United States are living with hemophilia B, which is a rare inherited bleeding disorder that prevents normal blood clotting due to a deficiency in Factor IX (FIX), which causes those with the disease to bleed more frequently and longer than others. It is estimated that as many as 60% of the American population have preexisting anti-AAV antibodies, which could interfere with rAAV gene delivery, demonstrating the essential need for nAbCyte CDx testing prior to treatment with BEQVEZ.

The results from the nAbCyte test will be reported qualitatively as negative (not detected) or positive (detected). A negative test result indicates that an individual with moderate to severe hemophilia B can be considered for BEQVEZ therapy. The FDA approval of nAbCyte Anti-AAVRh74var HB-FE CDx builds on Labcorp's comprehensive cell and gene therapy solutions, including specialized pre-clinical toxicology, biomarker and CDx development, and post-commercialization capabilities.