Today, the U.S. Food and Drug Administration (FDA) approved a gene therapy for persons with dystrophic epidermolysis bullosa (DEB). More specifically, it is a herpes-simplex virus type 1 (HSV-1) vector-based gene therapy (beremagene geperpavec  or Vyjuvek) approved to treat wounds in patients 6 months of age and older with DEB with mutation(s) in the collagen type VII alpha 1 chain (COL7A1) gene.

DEB is a genetic skin disorder due to mutations in the COL7A1 gene. When COL7A1 is deficient, skin layers can separate, causing painful blisters and wounds. The signs and symptoms of DEB vary widely among affected people. In mild cases, blistering may primarily affect the hands, feet, knees, and elbows. Severe cases often involve widespread blistering that can lead to vision loss, disfigurement, and other serious medical problems.

The approved gene therapy delivers normal copies of the COL7A1 gene to the wounds. The net results is an increase in collagen fibers that help to anchor and strengthen skin tissue.

The approval of beremagene geperpavec was largely based on a randomized, double-blinded, placebo-controlled study involving a total of 31 subjects with DEB. In the study, two DEB wounds of comparable size on each patient were identified and randomized to receive either topical administration of the gene therapy or the placebo on a weekly basis. After 6 months, complete wound healing occurred in 67% of the wounds exposed to the gene therapy compared to 22% of those given placebo. Results of this study were recently published in the New England Journal of Medicine.

The most common adverse reactions associated with beremagene geperpavec include itching, chills, redness, rash, cough and runny nose.

The approval of this therapy also provides the developers (Krystal Biotech) with a Rare Pediatric Disease Priority Review Voucher. The company can use this voucher for another drug under review by the FDA to have priority review (i.e.,  the FDA will have to review the medicine within 6 months instead of 10 months). For small companies like Krystal Biotech, this voucher is often sold to another company.  Eiger Biopharmaceuticals sold their review voucher for $95 million.

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