Dersimelagon NDA Accepted by FDA with Priority Review for EPP, XLP

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 therapy for erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), with a Prescription Drug User Fee Act (PDUFA) action date expected by the end of February 2027.¹

LEO Pharma also announced it has closed its acquisition of worldwide rights to dersimelagon from Tanabe Pharma, following fulfilment of customary closing conditions.¹ The deal strengthens LEO Pharma's late-stage rare dermatology pipeline and follows the company's acquisition of Replay's HSV gene therapy platform and its partnership with Boehringer Ingelheim on spesolimab (Spevigo).¹ If approved, dersimelagon would become the first oral treatment option for EPP and XLP.¹

"We are pleased to have completed the acquisition of dersimelagon and to have reached this important regulatory milestone," said Christophe Bourdon, CEO of LEO Pharma. "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."

Dersimelagon mechanism and INSPIRE trial results

Dersimelagon is a once-daily oral small-molecule melanocortin 1 receptor (MC1R) agonist. LEO Pharma's NDA submission is based on results from the global, randomized, double-blind, placebo-controlled phase 3 INSPIRE study, run by Tanabe Pharma prior to the acquisition.¹

According to LEO Pharma, dersimelagon demonstrated statistically significant and clinically meaningful outcomes across primary and secondary endpoints in the trial.¹ Among the functional outcomes reported was a significant prolongation of average daily sunlight exposure time to first prodromal symptoms, the symptom onset that precedes the sunlight-induced pain characteristic of EPP and XLP.¹ The company has not released exact effect sizes, p-values, or confidence intervals for these endpoints in this announcement.¹

Terms of the acquisition remain unchanged from LEO Pharma's original announcement on August 18, 2026: LEO Pharma acquired worldwide rights to dersimelagon for up to USD 435 million in upfront and near-term milestone payments, plus potential downstream milestones and double-digit to mid-teens tiered royalties on net sales.¹^,² The company noted the closing does not affect its 2026 financial outlook, which already reflected the acquisition in its H1 2026 Interim Report.¹

Regulatory pathway and pipeline context for EPP, XLP treatment

EPP and XLP are both driven by disruptions to heme biosynthesis that result in accumulation of protoporphyrin IX, causing intense sunlight-induced skin pain, and, in some patients, liver damage.¹ The FDA's Priority Review designation shortens the standard review timeline, reflecting the significant unmet need in a rare disease category with no approved oral systemic therapy.¹

LEO Pharma has not disclosed detailed safety data from INSPIRE in this release; the company states the acquisition strengthens its late-stage rare dermatology pipeline alongside its Replay gene therapy platform and spesolimab partnership.¹ The PDUFA date of late February 2027 sets the timeline for a potential first regulatory decision on dersimelagon.¹

Dersimelagon has not been approved by the FDA or any other regulatory authority, and its safety and efficacy have not been established by any regulatory authority. LEO Pharma's broader rare dermatology strategy now spans dersimelagon, the Replay HSV gene therapy platform, and spesolimab, positioning the company across multiple rare and immune-mediated skin disease programs.¹ ²

References

1. LEO Pharma. LEO Pharma announces FDA acceptance of dersimelagon NDA with Priority Review and closes acquisition from Tanabe Pharma. https://www.businesswire.com/news/home/20260918178750/en/LEO-Pharma-Announces-FDA-Acceptance-of-Dersimelagon-NDA-with-Priority-Review-and-Closes-Acquisition-from-Tanabe-Pharma. Published September 18, 2026. Accessed September 18, 2026.

2. Dermatology Times. LEO Pharma Acquires Potential First Oral Therapy for EPP and XLP. https://www.dermatologytimes.com/view/leo-pharma-acquires-potential-first-oral-therapy-for-epp-and-xlp. Published August 18, 2026. Accessed September 18, 2026.