FDA AdCom votes in favour of first gene transfer therapy for DMD

In a closely contested debate, a US Food and Drug Administration Advisory Committee (AdCom) panel voted eight to six in favour of the accelerated approval for Sarepta Therapeutics’ Duchenne muscular dystrophy (DMD) gene transfer therapy delandistrogene moxeparvovec (SRP-9001).

The gene therapy consists of a gene coding for micro-dystrophin carried through a recombinant adeno-associated virus vector. If approved, the therapy could become the first FDA-approved gene transfer therapy for the condition. The FDA will assess the drug’s approval before its Prescription Drug User Fee Act (PDUFA) date on 29 May 2023.

DMD is a rare disease caused by mutations in the dystrophin gene, leading to a deficiency in dystrophin protein and progressive muscle degeneration and weakness. The AdCom’s decision was based on results from Sarepta’s 101, 102, and 103 clinical trials along with an analysis of the three studies that compared results to a propensity score-weighted external control (EC). The 12 May AdCom mostly centred around data from the Phase II, randomized, placebo-controlled 102 study (NCT03769116).

At the Cellular, Tissue and Gene Therapies Advisory Committee AdCom, Dr. John Brandsema, paediatric neurologist in the Division of Neurology at the Children’s Hospital of Philadelphia (CHOP), discussed the long journey to developing the gene therapy. He said when the dystrophin gene was first discovered in the 1980s, the Duchenne community was convinced that this was the key to a “cure”, but for various reasons, it has taken 40 years to “come close to the realization of this dream”. He added, “Based upon the data I have seen thus far from the ongoing development program I am convinced this therapy should be approved.”

Dr. Anne Connelly, a paediatric neuromuscular disease expert at Nationwide Children’s Hospital, Columbus, and and sub-investigator on the micro-dystrophin gene trial agreed with Brandsema saying, “Over the last ten years, FDA-approved exon skipping therapies have allowed boys to walk a little longer and young men to breathe a little longer without support, but none have ever allowed function above their own baseline like we have observed with SRP 9001”.

However, panelist Diana Zuckerman, PhD, president of the Washington DC-based nonprofit National Center for Health Research, had some concerns about the gene therapy. She pointed out that the analyses did not show significant differences in motor function between patients receiving the drugs and those on a placebo at week 48. She also brought up Sarepta’s history of three DMD accelerated approvals based on “questionable data that had never been confirmed and required post-market studies”. She said, “I wish the data were more persuasive”.

The FDA accelerated approval pathway is designed to give patients with serious unmet needs earlier access to disease therapies earlier access. In a press release, Sarepta’s CEO Doug Ingram said, “Today’s advisory committee outcome is extremely important to the patient community, who are in urgent need of new therapies”.