Mirum Pharmaceuticals is a rare disease biopharmaceutical company focused on rare cholestatic liver diseases. Its primary commercial product is Livmarli (maralixibat), an oral IBAT inhibitor that blocks bile acid reabsorption in the small intestine, reducing elevated bile acid levels that cause severe pruritus and liver disease progression. Livmarli is approved in the U.S. and EU for cholestatic pruritus in patients with Alagille syndrome and PFIC, two rare pediatric liver diseases. Mirum also markets two bile acid medicines acquired from Travere Therapeutics in 2023: Cholbam, approved for rare bile acid synthesis disorders, and Ctexli, approved in early 2025 for cerebrotendinous xanthomatosis. Mirum sells its products through a specialty sales force targeting pediatric hepatologists and gastroenterologists in the U.S., Canada, and select European countries, with distribution partnerships covering other markets. Mirum does not manufacture its own drugs, relying on third-party contract manufacturers. Revenue is driven by the number of patients on therapy and per-patient pricing — a model well-suited to orphan diseases, where small patient populations support high prices. Livmarli uses weight-based dosing, so revenue per patient grows as pediatric patients gain weight over time. Beyond Livmarli, Mirum is advancing volixibat, another oral IBAT inhibitor in Phase 2b trials for PSC and PBC in adults, and brelovitug, a monoclonal antibody in Phase 3 trials for chronic hepatitis D, acquired via Bluejay Therapeutics in early 2026.