FDA approves first gene therapy for rare skin disorder

US Food and Drug Administration

The US Food and Drug Administration has approved Krystal Biotech’s Vyjuvek, a herpes-simplex virus type 1 (HSV-1) vector-based gene therapy, for the treatment of dystrophic epidermolysis bullosa (DEB).

It is approved for treating wounds in patients six months of age and older with mutation(s) in the collagen type VII alpha 1 chain (COL7A1) gene.

“Vyjuvek is the first FDA-approved gene therapy treatment for DEB, a rare and serious genetic skin disorder,” said Peter Marks, Director of the FDA’s Center for Biologics Evaluation and Research. “Today’s action demonstrates the FDA’s ongoing commitment to supporting the development and evaluation of new treatments that address unmet needs for rare diseases or conditions.”

DEB is a genetic disorder that affects the connective tissue in the skin and nails and results from mutation(s) in the COL7A1 gene. This gene encodes type VII collagen (COL7), which is an essential protein that helps strengthen and stabilise the outer and middle layers of the skin. When COL7A1 is deficient, skin layers can separate, causing painful and debilitating blisters and wounds.

DEB usually presents itself at birth and is divided into two major types depending on the inheritance pattern: recessive dystrophic epidermolysis bullosa (RDEB) and dominant dystrophic epidermolysis bullosa (DDEB).

Individuals with DDEB typically have mild cases with blistering primarily affecting the hands, feet, knees, and elbows. RDEB cases can be painful and debilitating, often involving widespread blistering that can lead to vision loss, disfigurement, and other serious medical complications, which could be fatal.

Established efficacy

Vyjuvek is a genetically modified (engineered in a laboratory) herpes-simplex virus used to deliver normal copies of the COL7A1 gene to the wounds. COL7 molecules arrange themselves into long, thin bundles that form anchoring fibrils that hold the epidermis (skin) and dermis together, which is essential for maintaining the integrity of the skin.

Vyjuvek has also been modified to eliminate its ability to replicate in normal cells. Vyjuvek is mixed into an excipient (non-active ingredient) gel prior to topical application. A healthcare professional evenly applies Vyjuvek gel in droplets to a patient’s wounds once a week.

The safety and effectiveness of Vyjuvek was established in a randomised study involving 31 subjects with DEB. Efficacy was established by improved wound healing, defined as the difference in the proportion of confirmed complete (100%) wound closure between the Vyjuvek-treated and the placebo-treated wounds at 24 weeks.

Sixty-five percent of the Vyjuvek-treated wounds completely closed while only 26% of the placebo-treated wounds completely closed.

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