Leo Pharma agreed to acquire rights to dersimelagon from Tanabe Pharma in a deal potentially worth up to $435 million, adding a late-stage, oral candidate to its dermatology portfolio. Tanabe’s small molecule is undergoing FDA review, with the drug granted Fast Track and Orphan Drug designations. Dersimelagon targets erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), both rare genetic disorders marked by painful light sensitivity and, in some patients, liver complications. Leo said a Phase 3 program showed the therapy could increase patients’ time outdoors and reduce pain episodes, with reported tolerability including benign moles and gastrointestinal effects. The acquisition extends Leo’s push into potentially differentiated oral rare-disease treatments while complementing its existing dermatology and gene-therapy expansion plans.