Longevity of hemophilia gene therapy in question as BioMarin seeks accelerated approval

As BioMarin reported interim Phase III data Tuesday that sets the company up for regulatory submissions, long-term Phase I/II data cast doubt on the durability of gene therapy valoctocogene roxaparvovec to treat severe hemophilia A. The product is an adeno-associated viral serotype 5 (AAV5) vector delivering the Factor VIII gene.

Among 16 evaluable patients treated with a single IV dose of 6x10¹³ vector genomes per kg (vg/kg) valoctocogene roxaparvovec in the Phase III GENEr8-1 trial, eight achieved Factor VIII levels of at least 40 IU/dL at weeks 23 to 26, meeting the prespecified criteria for U.S. and EU regulatory submissions. The therapy also decreased mean annualized bleed rate (ABR) from baseline to week 26 by 85% and mean Factor VIII usage from week 5 to 26 by 94%...