LEO Pharma to acquire Tanabe’s Dersimelagon for rare photosensitivity disorders
Under the agreement, LEO will pay up to US$435 million in upfront and near-term milestone payments for global rights to dersimelagon.
DENMARK—LEO Pharma has agreed to acquire worldwide rights to Tanabe Pharma’s investigational treatment dersimelagon, strengthening its rare dermatology pipeline with a late-stage oral therapy for two painful, light-sensitive genetic disorders.
Under the agreement, LEO will pay up to US$435 million in upfront and near-term milestone payments for global rights to dersimelagon.
Tanabe will also be eligible for additional development and commercial milestones, as well as tiered royalties on net sales if the drug receives regulatory approval.
FDA review underway
Dersimelagon is already under review by the US Food and Drug Administration (FDA), potentially bringing it closer to market.
The agency has granted the treatment both fast track and orphan drug designations, which support expedited development and regulatory review for therapies addressing serious conditions with limited treatment options.
The drug targets erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), rare inherited disorders that can cause severe and painful skin reactions after exposure to sunlight and certain wavelengths of artificial light.
Both conditions result from the accumulation of protoporphyrin, a molecule that reacts strongly to light.
When exposed to light, protoporphyrin triggers a chemical reaction that can cause intense burning pain and other symptoms, including tingling and itching.
Oral treatment option
Tanabe is developing dersimelagon as a once-daily oral tablet in 50mg and 100mg doses.
The small-molecule melanocortin-1 receptor (MC1R) agonist works by increasing melanin production in the skin, potentially reducing light penetration and protecting patients from phototoxic reactions.
Results from the Phase III trial NCT06144840, announced by Tanabe earlier this year, showed that dersimelagon extended the average time between sunlight exposure and the first appearance of symptoms. The treatment met the study’s primary endpoint.
If approved, dersimelagon would become the first oral treatment specifically indicated for EPP and XLP.
Afamelanotide, marketed as Scenesse, is already approved for EPP as a subcutaneous implant. However, an oral option could provide patients with a more convenient treatment alternative.
The combined prevalence of EPP and XLP is difficult to establish precisely, although estimates range from approximately one in 57,000 to one in 200,000 people.
Expanding rare dermatology portfolio
LEO CEO Christophe Bourdon said people living with EPP or XLP face a severe lifelong burden from reactions to sunlight and need treatments that can improve their daily lives.
He added that dersimelagon addresses an important unmet need in rare dermatology while giving LEO a late-stage oral candidate for its growing pipeline.
The acquisition follows other moves by LEO to expand its rare disease portfolio.
In May 2026, the Danish drugmaker agreed to pay US$50 million upfront to acquire Replay, a gene therapy company developing treatments for rare genetic dermatological disorders.
In July 2025, LEO also secured rights to Boehringer Ingelheim’s psoriasis treatment Spevigo (spesolimab) for US$105 million.
LEO said the Tanabe agreement reflects its strategy of strengthening its medical dermatology portfolio through targeted partnerships, acquisitions and external innovation, with rare dermatology remaining a key focus.
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