LEO Pharma pens $435m deal for Tanabe Pharma’s dersimelagon

LEO Pharma is betting up to $435 million on a pill that could give people with an ultra-rare light sensitivity disorder a way to spend more time outdoors.

The Danish company has agreed to acquire worldwide rights to Tanabe Pharma’s dersimelagon, an investigational once-daily oral melanocortin 1 receptor (MC1R) agonist designed to treat patients with erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP).

Both conditions are caused by a build-up of protoporphyrin in the body, which results in phototoxic reactions. When exposed to light, the protein can trigger painful reactions in the skin, including burning, swelling, redness, and, in some cases, liver damage.

Dersimelagon is designed to protect against such reactions by increasing skin melanin. By binding onto melanocortin-1 receptor proteins on skin cells, the drug triggers melanin production, which in turn stimulates pigmentation. The extra pigment absorbs light and provides natural photoprotection, helping patients tolerate sunlight.

Although the drug has not yet been approved, it has been granted both Fast Track Designation and Orphan Drug Designation by the US FDA. Tanabe submitted the drug to the US Food and Drug Administration in June, putting the programme within reach of a regulatory decision. If approved, dersimelagon would become the first oral treatment for EPP and XLP.

That would give LEO an opportunity to move into a rare disease market where treatment options are limited. Afamelanotide, sold as Scenesse, is approved for EPP, but is delivered through a subcutaneous implant, rather than as a daily pill.

Study results published by Tanabe earlier this year indicate that approval may not be too far off. Findings from the INSPIRE trial showed that patients taking dersimelagon could go longer after exposure to sunlight before experiencing the first signs of a prodromal reaction, such as burning or tingling – hitting nearly 30 minutes before symptoms appeared at Week 16 – meeting both primary and secondary endpoints.

"Patients living with EPP or XLP face the devastating lifelong burden of severe reactions to sunlight, and there is a clear need for treatment options that can make a meaningful difference in their everyday lives," said Christophe Bourdon, CEO, LEO Pharma, in a statement. "By addressing a clear unmet need in a rare skin disease, dersimelagon represents a compelling opportunity to expand our rare dermatology pipeline with a late-stage oral therapy candidate."

While the transaction is still subject to customary closing conditions and regulatory approvals, LEO expects to increase spending on preparations for a potential launch in 2026, with further investment planned for 2027.