FDA speeds up review of daily pill for rare sun-sensitive skin conditions

An experimental oral therapy that protects sensitive skin from painful reactions to sunlight is on track toward potential approval in the U.S. The U.S. Food and Drug Administration (FDA) has agreed to review an application seeking approval of the experimental oral therapy dersimelagon as a treatment for two types of porphyria, namely erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP).

The agency granted the application priority review, cutting its usual 10-month evaluation period down to six months. A final decision from the FDA is expected by the end of February 2027.

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Priority review and acquisition

The application was submitted by Leo Pharma, which recently acquired rights to dersimelagon from prior developer Tanabe Pharma for $435 million in upfront and near-term payments, plus additional milestone and royalty payments down the line.

“We are pleased to have completed the acquisition of dersimelagon and to have reached this important regulatory milestone,” Christophe Bourdon, CEO of Leo Pharma, said in a company press release. “The FDA’s Priority Review brings us one step closer to potentially providing a new treatment option for patients and addressing the significant unmet medical need in these rare skin diseases.”

Porphyrias are a group of genetic disorders marked by the buildup of molecules called porphyrins. XLP and EPP are both cutaneous forms of porphyria — in other words, these types of porphyria are marked mainly by skin symptoms. In particular, people with XLP and EPP usually experience photosensitivity, where exposure to sunlight can trigger painful reactions.

“Patients living with EPP or XLP face a devastating lifelong burden of sunlight-induced pain and a significant impact on their daily lives,” Bourdon said.

Dersimelagon, previously known as MT-7117, is designed to increase levels of a form of melanin — the dark brown pigment that normally helps to protect the skin from sun-related damage. By boosting melanin levels, the therapy aims to lessen photosensitivity.

Earlier this year, Tanabe Pharma announced results from a Phase 3 clinical trial called INSPIRE (NCT06144840). The study evaluated daily oral doses of dersimelagon against a placebo in 165 adults and teenagers (ages 12 to 75) living with EPP or XLP.

The study met its primary goal, which was to show that dersimelagon outperformed a placebo in increasing the amount of time patients could spend in the sun without any symptoms. The average amount of daily time in the sun without symptoms was nearly half an hour longer with dersimelagon than with the placebo after 16 weeks.

Dersimelagon also performed better than the placebo across other key secondary clinical measures, including rates of pain episodes, reducing the overall frequency of painful flare-ups, and improving patient-reported health scores.

The most common side effects reported in patients given dersimelagon were benign moles, headache, nausea, diarrhea, and skin darkening. These findings from INSPIRE, which formed the basis for Leo’s application seeking FDA approval, were generally consistent with results from earlier trials.