LEO Pharma Gains FDA Priority Review for Dersimelagon NDA Following Acquisition of Global Rights
LEO Pharma, a global leader in medical dermatology, has announced two significant developments for dersimelagon, an investigational oral therapy being developed for the rare genetic skin disorders erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP). The U.S. Food and Drug Administration (FDA) has accepted the company’s New Drug Application (NDA) for filing and granted the application Priority Review, while LEO Pharma has completed its acquisition of the worldwide rights to dersimelagon from Tanabe Pharma.
The FDA has established a Prescription Drug User Fee Act (PDUFA) action date by the end of February 2027, providing a regulatory target for the agency’s decision on the application.
The developments mark an important stage in LEO Pharma’s strategy to expand its presence in rare dermatology and strengthen its late-stage pipeline. Dersimelagon is being developed as a potential first-in-class, once-daily oral treatment for patients living with EPP and XLP, two rare inherited disorders that can cause severe sunlight-induced pain and substantially affect everyday activities.
LEO Pharma said the completed acquisition combines Tanabe Pharma’s research and development work on dersimelagon with LEO Pharma’s more than six decades of experience in dermatology and its international commercial infrastructure.
FDA Grants Priority Review to Dersimelagon NDA
The FDA’s acceptance of the NDA for filing means the agency has determined that the application is sufficiently complete to proceed through the regulatory review process. The FDA has also granted Priority Review, a designation used for applications for medicines that, if approved, could provide significant improvements in the safety or effectiveness of the treatment, diagnosis, or prevention of serious conditions.
Under the Priority Review pathway, the FDA aims to complete its review within a shorter timeframe than under standard review procedures.
For LEO Pharma, the designation represents an important regulatory milestone for dersimelagon. The company is now preparing for the next stages of the review process ahead of the anticipated PDUFA action date in February 2027.
However, FDA acceptance and Priority Review do not indicate that the medicine will ultimately be approved. Dersimelagon remains investigational, and its safety and efficacy have not been established by the FDA or any other regulatory authority.
Christophe Bourdon, CEO of LEO Pharma, said the company was pleased to complete the acquisition and reach the regulatory milestone.
“We are pleased to have completed the acquisition of dersimelagon and to have reached this important regulatory milestone,” Bourdon said. He highlighted the significant burden experienced by people living with EPP and XLP and said the FDA’s Priority Review brings the company closer to potentially providing another treatment option for patients with these rare diseases.
Worldwide Acquisition from Tanabe Pharma Completed
In addition to the FDA development, LEO Pharma confirmed that it has successfully completed its acquisition of the worldwide rights to dersimelagon from Tanabe Pharma.
The transaction follows the fulfillment of customary closing conditions. LEO Pharma announced the planned transaction earlier in August 2026, and the financial terms remain unchanged.
Under the agreement, LEO Pharma has acquired worldwide rights to dersimelagon for up to $435 million in upfront and near-term milestone payments. The transaction also includes potential downstream milestone payments and tiered royalties on net sales ranging from the double-digit percentage range up to the mid-teens.
The completed transaction provides LEO Pharma with control of the global development and commercialization rights to dersimelagon. It also allows the company to combine the existing development work conducted by Tanabe Pharma with LEO Pharma’s expertise and infrastructure in medical dermatology.
According to LEO Pharma, the transaction is intended to strengthen its late-stage rare dermatology pipeline and expand its portfolio of innovative treatments.
The acquisition does not change LEO Pharma’s previously communicated 2026 financial outlook, which already incorporated the transaction. The company said its financial expectations were outlined in its H1 2026 Interim Report published on August 18, 2026.
Dersimelagon Targets Rare Genetic Disorders
Dersimelagon is an investigational once-daily oral small-molecule melanocortin 1 receptor (MC1R) agonist being developed for EPP and XLP.
EPP and XLP are rare inherited disorders associated with abnormalities in the body’s heme production pathway. A major characteristic of these conditions is severe sensitivity to sunlight and certain forms of visible light. Exposure can trigger intense pain and other skin symptoms, creating substantial limitations on patients’ daily lives.
People with EPP or XLP can experience symptoms including skin redness, swelling, rash, and burning or severe pain after exposure to sunlight. These reactions can occur even after relatively brief periods outdoors, potentially leading patients to significantly restrict outdoor activities and modify their daily routines.
The disorders can therefore have consequences that extend beyond physical symptoms. Patients may face challenges participating in work, education, travel, recreation, and social activities that involve exposure to sunlight.
In some patients, protoporphyria can also be associated with liver complications. This makes the development of effective treatment options an important area of unmet medical need.
Phase 3 INSPIRE Study Provided Clinical Evidence
The regulatory application for dersimelagon is supported by clinical development data, including findings from the global Phase 3 INSPIRE study.
Earlier in 2026, Tanabe Pharma announced results from the randomized, double-blind, placebo-controlled Phase 3 trial. According to the company, the study demonstrated statistically significant and clinically meaningful outcomes across its primary and secondary endpoints.
One of the reported findings involved a functional measure that is particularly relevant to people with EPP and XLP: the amount of time patients can spend in sunlight before experiencing their first prodromal symptoms.
The study demonstrated a statistically significant prolongation of average daily sunlight exposure time to the onset of first prodromal symptoms among patients receiving dersimelagon compared with placebo.
Such outcomes are relevant because sunlight avoidance is a major part of managing EPP and XLP. Patients may need to plan activities around sunlight exposure, use protective clothing, remain indoors during daylight hours, or take other measures to minimize exposure and prevent painful reactions.
A treatment capable of extending the amount of time patients can spend outdoors before symptoms develop could potentially have implications for daily functioning and quality of life.
The Phase 3 findings provided the clinical foundation for the regulatory submission now undergoing FDA review. Nevertheless, the FDA will independently assess the complete evidence package, including efficacy, safety, manufacturing, and other regulatory considerations, before making a decision.
Potential First Oral Treatment for EPP and XLP
If approved by the FDA, dersimelagon could become the first oral treatment for EPP and XLP, according to LEO Pharma.
The potential availability of an oral therapy could represent an important addition to the treatment landscape for patients with these rare diseases. Oral administration may offer a different treatment approach compared with existing disease-management strategies, particularly for patients who must make extensive adjustments to their daily activities because of sunlight sensitivity.
LEO Pharma’s development strategy for dersimelagon reflects the company’s broader focus on addressing unmet needs in dermatology. The company has increasingly expanded its activities through acquisitions and partnerships designed to strengthen its pipeline and broaden its portfolio of innovative treatments.
The acquisition of dersimelagon is part of this broader strategy and follows other recent innovation activities, including LEO Pharma’s acquisition of Replay’s next-generation HSV gene therapy platform and its partnership with Boehringer Ingelheim for Spevigo® (spesolimab).
These activities contribute to LEO Pharma’s efforts to build a diversified pipeline across dermatological conditions with significant unmet medical needs.
Regulatory Decision Expected in Early 2027
With the NDA now accepted and granted Priority Review, the next major milestone for dersimelagon in the United States is the FDA’s regulatory decision.
The agency has established a PDUFA action date by the end of February 2027. Until that review is completed, dersimelagon remains an investigational medicine in the United States.
The upcoming regulatory assessment will determine whether the evidence submitted by LEO Pharma supports approval for the proposed use in EPP and XLP. As part of its review, the FDA will evaluate the available clinical evidence and other components of the NDA.
The Priority Review designation shortens the targeted review timeline but does not guarantee approval or establish the medicine’s safety and efficacy.
For patients and healthcare professionals involved in the treatment of EPP and XLP, the FDA review will therefore be an important milestone in determining whether dersimelagon can become a new treatment option.
Strengthening LEO Pharma’s Rare Dermatology Pipeline
The completion of the Tanabe Pharma transaction gives LEO Pharma worldwide rights to a late-stage investigational medicine with potential applications in two rare genetic disorders.
The company believes its global dermatology expertise and commercial infrastructure can support the continued development and potential future launch of dersimelagon, subject to regulatory approval.
The transaction also illustrates the role of strategic partnerships and acquisitions in advancing treatments for rare diseases. Tanabe Pharma’s development of dersimelagon and LEO Pharma’s dermatology expertise are being combined under a single global development and commercialization strategy.
For now, the focus remains on the FDA review and continued preparation for potential future commercialization. The company will also need to address regulatory requirements in other markets if it seeks approvals outside the United States.
Dersimelagon has not yet been approved by the FDA or any other regulatory authority, and its safety and efficacy have not been established by any regulatory authority.
With the NDA now under Priority Review and the worldwide acquisition completed, LEO Pharma enters the next stage of development with a potential new oral treatment for EPP and XLP. The FDA’s anticipated decision by the end of February 2027 will represent the next major regulatory milestone for dersimelagon and could determine whether the investigational MC1R agonist advances toward becoming a treatment option for patients living with these rare and debilitating genetic disorders.
About LEO Pharma
LEO Pharma is a global leader in medical dermatology. We deliver innovative solutions for skin health, building on a century of experience with breakthrough medicines in healthcare. We are committed to making a fundamental difference in people’s lives, and our broad portfolio of treatments serves close to 100 million patients in over 70 countries annually. LEO Pharma is co-owned by majority shareholder the LEO Foundation and, since 2021, Nordic Capital. Headquartered in Denmark, LEO Pharma has a team of 4,300 people worldwide. Together, we reach far beyond the skin. For more information, visit www.leo-pharma.com.