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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