LEO Pharma has entered into an agreement with Tanabe Pharma Corporation to acquire the worldwide rights to dersimelagon, an oral, once-daily small-molecule melanocortin 1 receptor (MC1R) agonist being developed for the treatment of Erythropoietic Protoporphyria (EPP) and X-Linked Protoporphyria (XLP).

EPP and XLP are rare genetic disorders that can cause severe and painful reactions to sunlight, significantly restricting patients’ ability to spend time outdoors. Symptoms may include skin redness, swelling, rashes and burning sensations, while some patients may also develop liver complications.

Dersimelagon is designed to increase melanin production in the skin, with the potential to reduce sunlight penetration and protect patients from phototoxic reactions associated with EPP and XLP.

Christophe Bourdon, CEO, LEO Pharma, said, “Patients living with EPP or XLP face the devastating lifelong burden of severe reactions to sunlight, and there is a clear need for treatment options that can make a meaningful difference in their everyday lives.” 

According to LEO Pharma, the acquisition aligns with its strategy of strengthening its medical dermatology portfolio through targeted acquisitions, partnerships and external innovation, with rare dermatology representing a key area of focus.

The company said dersimelagon could provide an opportunity to expand its rare dermatology pipeline with a late-stage oral therapy candidate. LEO Pharma also intends to leverage its dermatology expertise and global commercial infrastructure to potentially bring the treatment to patients in key markets, including the US and Japan.

Dersimelagon has received Fast Track Designation and Orphan Drug Designation from the US Food and Drug Administration (FDA). Tanabe Pharma submitted a New Drug Application (NDA) to the US FDA for EPP and XLP in June 2026. The candidate has not yet been approved by the FDA or any other regulatory authority, and its safety and efficacy have not been established by a regulatory agency.

If approved, dersimelagon could become the first oral therapy specifically indicated for EPP and XLP, potentially addressing a significant unmet medical need among patients with these rare disorders.

Earlier in 2026, Tanabe Pharma reported results from the global, randomised, double-blind, placebo-controlled Phase 3 INSPIRE study evaluating dersimelagon in patients with EPP and XLP. The company reported statistically significant and clinically meaningful results across primary and secondary endpoints, including a significant increase in the average daily duration of sunlight exposure before the onset of prodromal symptoms.

The Phase 3 findings were presented as a late-breaking study at the 2026 American Academy of Dermatology Annual Meeting.

Under the terms of the agreement, LEO Pharma will acquire worldwide rights to dersimelagon for up to USD 435 million in upfront and near-term milestone payments. The deal also includes potential downstream milestone payments and tiered royalties based on net sales.

Completion of the transaction remains subject to customary closing conditions, including applicable regulatory approvals. LEO Pharma expects the acquisition to increase its investment in 2026 for pre-launch activities and in 2027 for a potential launch.

LEO Pharma said an update to its 2026 financial outlook will be provided alongside its H1 2026 Interim Report, scheduled for publication on August 18, 2026.

J.P. Morgan Securities served as financial adviser to LEO Pharma, while Latham & Watkins LLP acted as legal adviser.

LEO Pharma is a global medical dermatology company with a portfolio of treatments serving patients across more than 70 countries. Tanabe Pharma Corporation is a Japan-focused pharmaceutical company with a history dating back to 1678 and a focus on addressing unmet medical needs through research and development, business development and strategic partnerships.