BioMarin’s Hemophilia A Gene Therapy Shows Promise in Clinical Trial
As of May 28, 2019, eight out of 20 patients in the GENEr8-1 study showed Factor VIII levels of 40 international units per deciliter (IU/dL) or more at 23 to 26 weeks, which was the pre-specified criteria for Factor VIII activity levels.
As of April 30, between weeks 23 to 26, in a cohort dosed at 6e13 vg/kg, seven of 16 patients reached or exceeded the pre-specified Factor VIII levels of 40 IU/dl using the chromogenic substrate (CS) assay. Prior to the April 30 cutoff date, one more patient met that criteria, bringing the total to eight.
Of the 16 patients who made it to week 26 by the April 30 cutoff, the estimated median Annual Bleed Rate (ABR) was zero and the estimated ABR was 1.5. This comes to a decrease of 85% from baseline levels where all patients were receiving standard of care prophylaxis. There was also an 84% decrease in annualized Factor VIII usage and a 94% decrease in mean FVIII usage annualized between week 5 and 26.
One concern is the 94% reduction in mean Factor VIII usage. In May 2018, BioMarin had reported a 98% drop. The change from 98% to 94% suggests there may be a diminishing treatment effect.
“We believe plateauing of declining Factor VIII is reassuring (and) the data appears stronger than what we or investors largely assumed,” wrote SVB Leerink analyst Joseph Schwartz.
The company expects to meet with the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) to review the data. BioMarin says it plans to announce the timing for its marketing applications in the third quarter of this year.
“Reaching this pre-specified clinical endpoint is an important milestone that brings us one step closer to a potential regulatory submission in both the U.S. and Europe for valoctocogene roxaparvovec to treat adults with severe hemophilia A,” stated Hank Fuchs, president of Worldwide Research and Development at BioMarin. “Our discussions with the FDA and EMA underscore the high level of unmet need in the hemophilia community, and we look forward to continuing our productive dialogue on the submissions.”
The gene therapy received Breakthrough Therapy Designation from the FDA and Priority Medicines (PRIME) access by the EMA. It also received orphan drug designation from both organizations.
BioMarin’s Phase III program for valoctocogene roxaparvovec includes two trials, one with the 6e13 vg/kg dose (GENEr8-1) and one with the 4e13 vg/kg dose (GENEr8-2). GENEr8-1 has about 130 participants and is powered to determine the superiority of the current standard of care. Enrollment is expected to finish to the amended GENEr8-1 trial in the third quarter of this year. GENEr8-2 is ongoing and remains unchanged with 40 participants. It is expected to complete enrollment one or two quarters after GENEr8-1 in 2019.