Ctexli’s approval further entrenches Mirum as a leader in rare liver diseases, alongside its cornerstone product Livmarli and upcoming drug volixibat.
The FDA on Friday signed off on the use of Mirum Pharmaceuticals’ chenodiol—under the brand name Ctexli—to treat cerebrotendinous xanthomatosis, a “very rare lipid storage disease,” as per the regulator’s announcement of the approval.
Ctexli is the first-ever FDA-approved drug for this disease and will give patients and physicians “a safe and effective treatment option” to address cerebrotendinous xanthomatosis (CTX), Janet Maynard, director of the FDA’s Office of Rare Diseases, Pediatrics, Urologic and Reproductive Medicine, said in a statement.
The drug’s label is relatively clean—with no boxed warning—though it carries precautions for liver toxicity. The most common adverse events associated with Ctexli include hypertension, muscle weakness and diarrhea.
Afflicting one in a million people globally, CTX is a rare and progressive metabolic disorder characterized by the inability to break down certain types of lipids—especially cholesterol—leading to their toxic accumulation throughout the body, particularly in the brain and connective tissues. Patients with CTX suffer from neurological abnormalities in early adulthood, including seizures as well as problems with movement and speech.
CTX is caused by mutations in the CYP27A1 gene, which under healthy circumstances encode for an enzyme that breaks down cholesterol into bile acids. Ctexli, an orally available drug, is Mirum’s answer to this defect. In CTX patients, it works by replenishing the body’s insufficient levels of bile acids, in turn reducing the build-up of the toxic metabolites that cause the disease.
To back its drug application, Mirum submitted data from the Phase III RESTORE study, a June 2024 readout from which showed that the drug could lower bile alcohols “with high statistical significance,” the biotech said at the time. In particular, Ctexli’s benefit was 20-fold greater in magnitude than that of placebo.
With Friday’s approval, Mirum entrenches its expertise in the rare liver disease space. The biotech’s business is anchored by its oral drug Livmarli, which first won the FDA’s approval in September 2021 for cholestatic pruritus in Alagille syndrome, a genetic disorder occurring in between one in 30,000 and one in 100,000 births—before securing an expansion in March last year for familial intrahepatic cholestasis, another rare bile secretion disorder.
In the third quarter of 2024, Livmarli secured $59.1 million in sales, accounting for more than half of Mirum’s net product sales that quarter. The biotech is expected to release its full-year results this week.
In addition, Mirum is also developing volixibat, an oral inhibitor of the ileal bile acid transporter, for primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC). In June 2024, the biotech reported promising mid-stage data for the volixibat, touting significant pruritus improvement in PBC patients and a PSC benefit that “exceeds efficacy threshold,” enabling the continuation of the study.
A few months later, in October, the FDA granted volixibat its Breakthrough Therapy designation for PBC. Additional data from the Phase IIb trial of volixibat in this indication is expected in 2026.
