Leo Pharma said it will acquire worldwide rights to Tanabe Pharma’s rare disease drug dersimelagon, in a deal potentially worth up to $435 million including upfront and milestone payments. The therapy is in FDA review and has Fast Track and Orphan Drug designations, with a Phase 3 program already completed. Dersimelagon is being developed as a potential once-daily oral treatment for erythropoietic protoporphyria (EPP) and X-linked protoporphyria (XLP), conditions that cause severe sunlight-induced skin reactions. Leo characterized the acquisition as a way to expand its rare dermatology pipeline. If approved, the deal could position Leo to compete in a niche with limited oral options, while Tanabe monetizes its late-stage asset under a licensing structure.