Frequently Asked Questions:
- What is dersimelagon being developed for?
Dersimelagon is an investigational oral MC1R agonist under FDA Priority Review for erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), with a PDUFA date set for the end of February 2027.
- How does dersimelagon work?
Dersimelagon is a once-daily oral small-molecule agonist of the melanocortin 1 receptor (MC1R), a pathway involved in skin pigmentation and photoprotection.
- What did the INSPIRE trial show?
The Phase 3 INSPIRE study showed dersimelagon significantly extended the time to first prodromal symptoms after sunlight exposure compared with placebo, with topline data also showing fewer total pain events on active treatment.
The US Food and Drug Administration (FDA) has accepted for filing and granted Priority Review to the new drug application (NDA) for dersimelagon, an investigational oral melanocortin 1 receptor (MC1R) agonist for erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), with a Prescription Drug User Fee Act (PDUFA) action date set for the end of February 2027, according to LEO Pharma.¹
LEO Pharma also announced it has closed the acquisition of worldwide rights to dersimelagon from Tanabe Pharma, following completion of customary closing conditions.¹ No oral therapy is currently approved for EPP or XLP, and the NDA is supported by data from the global, randomized, double-blind, placebo-controlled Phase 3 INSPIRE study (NCT06144840).²
"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 statement. "Patients living with EPP or XLP face a devastating lifelong burden of sunlight-induced pain and a significant impact on their daily lives. 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."¹
Dersimelagon Efficacy in the INSPIRE Trial
The INSPIRE study enrolled 165 patients with EPP or XLP, aged 12 - 75 years, across global sites, randomly assigning 82 participants to dersimelagon 200 mg once-per-day and 83 to placebo for a 16-week double-blind treatment period.² A 36-week open-label extension is ongoing.² Investigators excluded patients with laboratory-confirmed liver disease or those on other active therapies for EPP or XLP.³ The primary endpoint was change from baseline in average daily sunlight exposure time to first prodromal symptom, measured between 1 hour post-sunrise and 1 hour pre-sunset.³
Dersimelagon produced a placebo-adjusted increase in sunlight exposure time to first prodromal symptom of approximately 23 minutes during Weeks 12 through 16 (P = .004), with the effect reaching nearly 30 minutes by Week 16 in supplementary analysis.² LEO Pharma's release and Tanabe Pharma's original announcement did not disclose full statistical detail beyond these topline figures.¹
Dersimelagon Safety and Secondary Outcomes in EPP, XLP
Secondary endpoints in the INSPIRE study included patient Global Impression of Change (PGIC) at Week 16, the total number of sunlight-induced pain events, and the total number of non-prodromal phototoxic reactions during the double-blind period.³ Patients receiving dersimelagon reported roughly 39% fewer total pain events compared with placebo, supporting translation of the extended sunlight exposure window into clinically meaningful benefit.²
Dersimelagon demonstrated a favorable safety and tolerability profile in the trial, with most adverse events characterized as mild or moderate in severity, per Tanabe Pharma's topline announcement.³ Neither LEO Pharma's release nor the topline data disclosed specific adverse event rates or discontinuation figures, and no new safety signals were reported.¹ The open-label extension period remains ongoing.³
LEO Pharma acquired worldwide rights to dersimelagon for up to USD 435 million in upfront and near-term milestone payments, plus downstream milestones and tiered royalties reaching the mid-teens, with terms unchanged from the deal's original announcement in August 2026.¹ The acquisition adds to LEO Pharma's recent rare dermatology expansion, which includes its acquisition of Replay's HSV gene therapy platform and its partnership with Boehringer Ingelheim for spesolimab (Spevigo).¹
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