Dominantly or recessively inherited variants in COL7A1 cause dystrophic epidermolysis bullosa (DEB), a devastating skin disorder. A gene therapy approach to treat DEB on a molecular basis has now been evaluated for efficacy and safety in a phase 3 clinical study. The approach uses herpes simplex virus (HSV) type 1 as a gene vector to deliver two copies of COL7A1 into patients’ skin cells to restore production of functional protein. The randomized, double-blind, placebo-controlled study included 31 patients for a period of 26 months. In each patient, a pair of similar wounds were selected and received weekly either placebo or beremagene geperpavec (B-VEC) applied as a gel. As the New England Journal of Medicine reports, complete wound healing occurred after three or six months in a higher percentage of wounds treated with B-VEC compared to wounds exposed to placebo (67 % B-VEC, 22 % placebo after six months; 71 % B-VEC, 20 % placebo after three months). Pruritus and mild systemic side effects were reported in patients treated with B-VEC.

COL7A1 incorporates type 7 collagen into anchoring fibrils in the skin, providing cohesion between the two top most skin layers, epidermis and dermis. If COL7A1 is deficient, the structural integrity of these skin layers is disrupted. Skin becomes fragile. Patients with DEB will develop painful blisters and chronic, non-healing wounds even after minimal friction or trauma to the skin. Excessive scarring may result in limb deformities. Additionally, chronic wounds and fibrosis can lead to skin cancer (squamous-cell carcinoma).