Leo Pharma agreed to acquire Tanabe Pharma’s oral rare-disease candidate dersimelagon in a deal potentially worth up to $435 million, targeting two genetic, sunlight-sensitive conditions: erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP). The drugmaker said the acquisition includes upfront and milestone payments plus royalties. Tanabe has advanced dersimelagon with FDA Fast Track and Orphan Drug designations and submitted to the FDA in June. Leo Pharma positioned dersimelagon as a potential first orally available option for these photosensitivity disorders, referencing Phase 3 results previously reported. The transaction further expands Leo’s dermatology franchise as it seeks to bring a late-stage asset into clinical-regulatory execution for a rare segment with major patient burden.