LEO Pharma has agreed to buy the worldwide rights to Tanabe Pharma’s drug in development for photosensitive genetic disorder treatment, bolstering the Danish company’s pipeline that has already undergone expansion this year.
As per the deal, LEO is outlaying up to $435m in upfront and near-term milestone payments for global rights to Tanabe’s dersimelagon. The Japanese biopharma is also eligible for potential downstream milestones and tiered royalties on net sales if the drug wins approval.
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A route to market may not be far off. Dersimelagon is already under US Food and Drug Administration (FDA) review and is on an expedited regulatory process owing to its fast track and orphan drug designations.
Dersimelagon is designed to treat erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP) – two rare genetic conditions that cause severe, painful skin reactions under exposure to sunlight and certain wavelengths of artificial light.
The disorders are caused by the buildup of a molecule called protoporphyrin in the body, which acts as a strong phototoxic agent. The protein absorbs light energy and sets off a chemical reaction that results in burning pain.
Tanabe’s dersimelagon is a once-daily oral pill under evaluation in 50mg and 100mg doses. The small MC1R agonist works by increasing skin melanin, helping to reduce sunlight penetration and protect against phototoxic reactions.
Results from a Phase III trial (NCT06144840) announced by Tanabe earlier this year demonstrated dersimelagon’s ability to prolong the average time between sunlight exposure and first manifestation of symptoms such as burning, tingling, or itching – hitting the study’s primary endpoint.
If approved, dersimelagon would represent the first oral therapy for the treatment of EPP and XLP. A subcutaneous implant of Scenesse (afamelanotide) is already approved for EPP, though the availability of a pill would mark a significant advancement of treatment options for patients.
It is hard to definitively state the rarity of the two diseases. Combined global prevalence is estimated between one in 57,000 and one in 200,000 people for EPP and XLP, respectively.
LEO’s CEO, Christophe Bourdon, 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.
“By addressing a clear unmet need in a rare skin disease, dersimelagon represents a compelling opportunity to expand our rare dermatology pipeline with a late-stage oral therapy candidate.”
The rights acquisition marks another recent bolstering of LEO’s rare disease pipeline. In May 2026, the Danish drugmaker spent $50 upfront to buy Replay, a gene therapy company developing treatments for rare genetic dermatological conditions. LEO also secured the rights to Boehringer Ingelheim’s psoriasis drug Spevigo (spesolimab) for $105m in July last year.
In a statement announcing the Tanabe deal, LEO said the acquisition reflects its strategy to “strengthen its medical dermatology portfolio through targeted partnerships, acquisitions, and external innovation, with rare dermatology as a key focus area.”
