FDA Issues CRL for Hemophilia A Gene Therapy


Valoctocogene roxaparvovec would be the first ever approved gene therapy to treat patients with hemophilia A.


The US Food and Drug Administration (FDA) has issued a complete response letter (CRL) to BioMarin Pharmaceutical for its valoctocogene roxaparvovec (Valrox) gene therapy for severe hemophilia A.

The company’s application was supported by its ongoing phase 3 study of the investigative gene therapy as well as three-year data from the Phase 1/2 study.

However, the agency requested that the company provide substantial evidence of a durable effect using Annualized Bleeding Rate (ABR) as the primary endpoint. Thus, they introduced a new recommendation for two years of data from the study.

The FDA’s decision recommends that investigators complete their Phase 3 study, which began on November 2019, with the last patient expecting to complete two years of follow up on November 2021.

Furthermore, the agency concluded that the differences between Phase 1/2 and Phase 3 of the study limited its ability to rely on the Phase 1 study to support durability of effect.

BioMarin has indicated their commitment to pursuing approval for the novel gene therapy.

"We are surprised and disappointed that the FDA introduced new expectations for the first time in the Complete Response Letter.” Jean-Jacques Bienaimé, M.B.A., Chairman and Chief Executive Office of BioMarin said in a statement. “We are confident in valoctocogene roxaparvovec gene therapy and its potential to redefine the treatment paradigm for people with hemophilia A."

Valoctocogene roxaparvovec was previously granted Priority Review status and Breakthrough Therapy and Orphan Drug designations, which it currently maintains.

Clinical trials will nonetheless continue as the company explores next steps to obtain approval.

The company is also waiting on the European Medicines Agency to review and approve its Marketing Authorization Application for its therapy.

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