In a first for companion diagnostics, FDA approves test for use with BioMarin's hemophilia gene therapy

The FDA’s approval on Thursday for BioMarin’s Roctavian gene therapy for severe hemophilia A came with a second approval attached: for a companion diagnostic that can identify which patients may be best served by the drug.

The test, dubbed AAV5 DetectCDx, was developed through a collaboration between BioMarin and ARUP Laboratories, with the test used throughout several of BioMarin’s clinical trials of Roctavian. ARUP will serve as the sole lab testing provider for the diagnostic in the U.S., according to a Thursday announcement.

According to the testmaker, with the FDA’s go-ahead for use with Roctavian—which itself is the first gene therapy approved to treat severe hemophilia A—the test has become the first companion diagnostic immunoassay cleared by the agency for use alongside a gene therapy.

"It is extremely satisfying to see the effort and dedication of both teams come to fruition after a successful and long-standing collaboration,” Emily Coonrod, senior director of companion diagnostics in the ARUP’s PharmaDx department, said in the company’s announcement. “It has required the combined expertise, hard work and perseverance of both teams to achieve this milestone.”

BioMarin’s therapy is a one-time infusion that works by using adeno-associated virus serotype 5, or AAV5, to deliver a copy of the gene that produces congenital factor VIII (FVIII), since severe hemophilia A is caused by a missing or defective FVIII gene.

The drug is therefore indicated only for patients who don’t have preexisting antibodies to AAV5—which is where ARUP’s test steps in. The companion diagnostic analyzes plasma samples to look for those anti-AAV5 antibodies; only those patients who are found to be negative for the antibodies are then declared eligible for a Roctavian infusion.

The test has been approved in Europe for over a year, well before Roctavian earned its own European approval in August. In addition to the standalone companion diagnostic, ARUP’s offerings on the continent also include the AAV5 DetectCDx Kit, which can be used by partner lab facilities to perform the test.

AAV5 DetectCDx is the third of ARUP’s companion diagnostics to earn the FDA’s authorization. The other two are both aimed at weeding out potential recipients of Novartis’ Gleevec, a chemotherapy drug used to treat certain types of leukemia, gastrointestinal stromal tumors and other forms of cancer.

Both of the Gleevec-associated assays were cleared through the FDA’s humanitarian device exemption pathway in December 2015, and both look for disorders affecting the cells in bone marrow.