LEO Pharma A/S / Replay Holdings LLC

Dystrophic Epidermolysis Bullosa (DEB)

2K US cases/yr · $715M US Market · $389.1M Vyjuvek FY2025 global net product revenue

Disease Overview

Dystrophic epidermolysis bullosa (DEB) is a rare, inherited connective tissue disorder caused by mutations in the COL7A1 gene that encodes type VII collagen, the protein anchoring the epidermis to the underlying dermis. Loss of functional anchoring fibrils leads to extreme skin fragility, with minor friction or trauma producing painful blisters, chronic wounds, scarring, joint contractures, esophageal strictures, and a markedly elevated lifetime risk of aggressive squamous cell carcinoma. DEB exists in dominant (DDEB, milder) and recessive (RDEB, severe) forms, with RDEB patients facing dramatically reduced life expectancy, often dying from metastatic skin cancer in their third or fourth decade. US prevalence is estimated at approximately 3.3 per million population (roughly 1,000-2,000 patients), with global prevalence varying widely by registry methodology. Until recently, management was supportive only, focused on wound dressings, infection control, nutrition, and pain management. The May 2023 FDA approval of Krystal Biotech's Vyjuvek (beremagene geperpavec, B-VEC), a topically applied HSV-1-vectored gene therapy delivering functional COL7A1, marked the first disease-modifying therapy for DEB and the first redosable topical gene therapy approved anywhere in the world. The September 2025 label update extended Vyjuvek to patients from birth, broadening the addressable population. Despite Vyjuvek, significant unmet need persists for non-cutaneous manifestations and for patients with extensive wound burden requiring more efficient delivery approaches.

Competitive Landscape

DEB is a one-product market today: Krystal Biotech's Vyjuvek (beremagene geperpavec) holds clear US category leadership as the first and only FDA-approved redosable topical gene therapy for DEB, generating $389.1M in FY2025 global product revenue with Q4 2025 alone at $107.1M and over 575 US reimbursement approvals. Krystal expanded the Vyjuvek label to patients from birth in September 2025 and is rolling out commercially in Europe and Japan. Replay's preclinical HSV gene therapy platform enters as a Vyjuvek follow-on with similar viral vector chassis (HSV-1 tropism for skin and redosing capability) but with a 'high-payload' design that LEO believes can carry larger genetic cargo and address features Vyjuvek cannot. The asset is preclinical, so direct head-to-head differentiation will not surface for years, and LEO's $50M upfront plus undisclosed milestones reflects appropriately staged risk. The strategic logic is platform optionality across LEO's broader rare-dermatology portfolio rather than near-term Vyjuvek displacement. Update (Q1 2026): Krystal reported VYJUVEK net product revenue of $116.4M for Q1 2026 (+32% YoY), bringing cumulative since-launch revenue to $846.7M (Krystal Biotech 8-K, 4 May 2026), underscoring the scale and momentum of the incumbent LEO/Replay would eventually face.