LEO Pharma Expands Rare Dermatology Pipeline with Replay Gene Therapy Acquisition

LEO Pharma has entered into a definitive agreement to acquire Replay, a San Diego-based gene therapy company developing a herpes simplex virus (HSV)-based platform for rare genetic skin diseases¹. The acquisition adds a next-generation gene delivery system designed to transport large therapeutic genes directly into skin cells using a topical formulation approach².

Replay’s platform is built on engineered HSV vectors with natural skin tropism, enabling targeted delivery of genetic payloads to diseased tissue². According to the companies, this approach allows for redosing capability and localized application—two features considered important for chronic dermatologic conditions¹.

The financial terms of the transaction include a $50 million upfront payment, with additional milestone-based payments and tiered royalties contingent on future development success².

Why is dystrophic epidermolysis bullosa a key focus?

The lead program within Replay’s pipeline targets dystrophic epidermolysis bullosa (DEB), a severe and life-limiting genetic skin disorder characterized by fragile skin, chronic blistering, and painful wound formation⁴. The disease is driven by mutations affecting structural skin proteins, making it a prime candidate for gene replacement approaches⁴.

Replay’s investigational therapy is currently in preclinical development and is being formulated as a topical gel intended to deliver functional genetic material directly to affected skin areas².

Patient advocacy groups and dermatology researchers have long highlighted DEB as an area of high unmet need due to the lack of curative or disease-modifying therapies⁴. The condition is also associated with serious long-term complications, including scarring and increased risk of skin cancer⁴.

How does HSV gene therapy work in dermatology applications?

The HSV-based platform leverages the virus’s natural ability to infect skin cells while being engineered to remove pathogenic properties². Instead, it serves as a delivery vehicle for therapeutic genes that can restore missing or defective protein function at the site of disease².

Unlike systemic gene therapies, this approach is designed for localized dermatologic administration, potentially reducing systemic exposure and improving safety profiles². The ability to redose patients is also considered a key differentiator, as many current gene therapy approaches are limited by immune response constraints after a single administration².

Replay’s platform has also been designed to accommodate large genetic payloads, expanding its potential use beyond single-gene disorders².

Why is LEO Pharma investing in gene therapy now?

The acquisition aligns with LEO Pharma’s broader strategy to expand beyond traditional dermatology and into next-generation genetic medicine¹ . The company has increasingly focused on building a diversified pipeline across inflammatory and rare dermatologic diseases, including biologics, small molecules, and now gene therapy³.

Industry analysts note that dermatology is becoming one of the most active areas for rare disease innovation, particularly as gene delivery technologies mature². By integrating Replay’s platform, LEO Pharma gains early access to a modality that could reshape how inherited skin diseases are treated².

What are the broader implications for rare dermatology innovation?

The acquisition reflects a growing trend of established dermatology companies investing in cell and gene therapy platforms to address previously untreatable conditions². Gene therapy approaches in dermatology remain in early stages, but they are gaining momentum as vector design, safety, and delivery methods improve².

For LEO Pharma, the deal represents a strategic expansion into precision medicine for skin diseases, complementing its existing portfolio of topical and biologic therapies¹. It also signals increased competition in rare dermatology, where companies are racing to develop first-in-class or best-in-class disease-modifying treatments².

If successful, HSV-based gene therapy could open pathways not only for DEB but also for other genetically driven dermatologic disorders².

References

1. LEO Pharma acquires Replay. (2026, April 30). LEO Pharma.
   https://www.leo-pharma.com/media-center/news/2026-leo-pharma-acquires-replay
   
2. Waldron, J. (2026 Apr 30). Denmark’s LEO Pharma pays $50M for Replay and its preclinical skin disease gene therapy. Fierce Biotech.
   https://www.fiercebiotech.com/biotech/denmarks-leo-pharma-pays-50m-replay-and-its-preclinical-skin-disease-gene-therapy
   
3. Media center news. (n.d.). LEO Pharma.
   https://www.leo-pharma.com/media-center/news
   
4. Bader, K. (2025 Oct 3). LEO Pharma finalizes acquisition of spesolimab for GPP. Dermatology Times.
   https://www.dermatologytimes.com/view/leo-pharma-finalizes-acquisition-of-spesolimab-for-gpp