LEO Pharma Acquires Dersimelagon Rights for Rare Skin Diseases

LEO Pharma has agreed to acquire worldwide rights to dersimelagon from Tanabe Pharma in a deal that could reach up to $435 million in upfront and near-term milestone payments.

Dersimelagon is an investigational once-daily oral treatment being developed for erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), two rare genetic disorders that can cause severe pain and skin reactions after exposure to sunlight.

The acquisition strengthens LEO Pharma’s rare dermatology pipeline and adds a late-stage treatment candidate that has already completed Phase 3 development. Tanabe Pharma submitted a New Drug Application (NDA) for dersimelagon to the U.S. Food and Drug Administration (FDA) in June 2026. The FDA has not yet approved the treatment.

EPP and XLP are lifelong conditions that can have a major impact on patients’ daily lives. Exposure to sunlight can trigger severe skin pain, along with symptoms such as redness, swelling, rash and burning sensations. In some patients, the diseases can also lead to liver damage.

Dersimelagon is designed to activate the melanocortin 1 receptor (MC1R), which increases melanin in the skin. The treatment is intended to reduce the amount of sunlight reaching deeper layers of the skin and help protect patients from painful reactions.

“Patients living with EPP or XLP face the devastating lifelong burden of severe reactions to sunlight,” said Christophe Bourdon, CEO of LEO Pharma. He added that dersimelagon could help address an important unmet need in rare dermatology and fits the company’s strategy of investing in innovative treatments for skin diseases.

Tanabe Pharma CEO Akihisa Harada said LEO Pharma’s dermatology expertise and global reach make it well positioned to advance dersimelagon and potentially bring the treatment to patients worldwide.

Dersimelagon has received both FDA Fast Track Designation and Orphan Drug Designation. If approved, it could become the first oral treatment for EPP and XLP.

The drug has already generated positive Phase 3 results. Earlier in 2026, Tanabe Pharma reported findings from the global Phase 3 INSPIRE study, a randomized, double-blind and placebo-controlled trial involving patients with EPP and XLP. The study showed statistically significant and clinically meaningful results across its primary and secondary endpoints.

One important finding was an increase in the average amount of time patients could spend in sunlight before experiencing the first signs of symptoms. The Phase 3 results were presented as a late-breaking presentation at the 2026 American Academy of Dermatology Annual Meeting.

The deal is part of LEO Pharma’s broader strategy to expand its medical dermatology portfolio through acquisitions, partnerships and external innovation. The company has also recently acquired Replay’s next-generation HSV gene therapy platform and partnered with Boehringer Ingelheim on Spevigo (spesolimab).

Under the agreement, LEO Pharma will pay up to $435 million in upfront and near-term milestone payments, along with potential additional milestone payments and tiered royalties based on net sales.

The transaction remains subject to customary closing conditions, including regulatory approvals. LEO Pharma expects to increase investment in pre-launch activities during 2026 and prepare for a potential launch in 2027.

While the FDA is reviewing the NDA, dersimelagon remains an investigational treatment. Its safety and effectiveness have not been established by any regulatory authority.