Mirum Pharmaceuticals Secures FDA Approval for First-Ever Treatment of Rare Liver Disease

Mirum Pharmaceuticals has further solidified its position as a leader in rare liver diseases with the recent FDA approval of Ctexli (chenodiol) for the treatment of cerebrotendinous xanthomatosis (CTX). This milestone marks the first-ever FDA-approved drug for this extremely rare lipid storage disease, affecting approximately one in a million people globally.

Groundbreaking Approval for CTX Treatment

The U.S. Food and Drug Administration (FDA) granted approval to Ctexli on February 24, 2025, providing patients and physicians with a safe and effective treatment option for CTX. Janet Maynard, director of the FDA's Office of Rare Diseases, Pediatrics, Urologic and Reproductive Medicine, emphasized the significance of this approval in addressing an unmet medical need.

CTX is a progressive metabolic disorder characterized by the body's inability to break down certain lipids, particularly cholesterol. This leads to toxic accumulation throughout the body, especially in the brain and connective tissues. Patients typically experience neurological abnormalities in early adulthood, including seizures and problems with movement and speech.

Ctexli, an orally available drug, works by replenishing the body's insufficient levels of bile acids, thereby reducing the build-up of toxic metabolites that cause the disease. The drug's approval was supported by data from the Phase III RESTORE study, which demonstrated a 20-fold greater benefit in lowering bile alcohols compared to placebo.

Expanding Portfolio in Rare Liver Diseases

The approval of Ctexli further strengthens Mirum's expertise in the rare liver disease space. The company's business is anchored by its oral drug Livmarli, which first received FDA approval in September 2021 for cholestatic pruritus in Alagille syndrome. Livmarli's indication was later expanded in March 2024 to include familial intrahepatic cholestasis.

Livmarli has been a significant contributor to Mirum's revenue, generating $59.1 million in sales during the third quarter of 2024, accounting for more than half of the company's net product sales for that period. Full-year results for 2024 are expected to be released in the coming week.

Pipeline Progress and Future Outlook

In addition to Ctexli and Livmarli, Mirum is developing volixibat, an oral inhibitor of the ileal bile acid transporter, for primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). The company reported promising mid-stage data for volixibat in June 2024, showing significant pruritus improvement in PBC patients and a PSC benefit that "exceeds efficacy threshold."

The FDA granted volixibat Breakthrough Therapy designation for PBC in October 2024, further highlighting the potential of this drug candidate. Additional data from the Phase IIb trial of volixibat in PBC is expected in 2026, potentially paving the way for another significant addition to Mirum's rare liver disease portfolio.

With these developments, Mirum Pharmaceuticals continues to establish itself as a key player in the treatment of rare liver diseases, addressing critical unmet needs and providing hope for patients with limited therapeutic options.