Ctexli (Chenodiol) Gains FDA Approval as First CTX Treatment

Mirum Pharmaceuticals, a biotech innovator known for developing therapies for rare metabolic disorders, now has FDA approval for its new treatment, Ctexli (chenodiol) tablets — the first and only medication approved for cerebrotendinous xanthomatosis (CTX) in adults.

CTX is a rare, progressive genetic disorder caused by mutations in the CYP27A1 gene, which disrupts the liver’s ability to produce chenodeoxycholic acid, a bile acid.

This deficiency results in an abnormal buildup of cholesterol metabolites in various organs, including the brain, liver, skin and tendons, ultimately leading to irreversible damage.

According to the NIH, older studies suggest that CTX affects approximately 1 in 72,000 to 1 in 150,000 individuals among Americans of European ancestry, though its true prevalence is likely higher due to underdiagnosis.

“CTX is a progressive multisystemic disorder that significantly impacts patients and previously lacked approved treatments,” stated Dr. Janet Maynard, director of the Office of Rare Diseases, Pediatrics, Urologic and Reproductive Medicine at the FDA’s Center for Drug Evaluation and Research in the FDA news release.

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Ctexli is designed to replace the missing bile acid, reducing the toxic accumulation of these metabolites.

Administered as an oral tablet at a dosage of 250 mg three times per day, the treatment aims to restore normal bile acid levels and reestablish metabolic equilibrium.

The FDA’s approval was supported by data from the Phase III RESTORE study — a 24‑week, double‑blind, placebo‑controlled, randomized crossover withdrawal trial.

In this study, patients receiving chenodiol experienced a statistically significant reduction in both plasma cholestanol and urine 23S-pentol levels, with a remarkable 20‑fold difference in urine 23S‑pentol between the treatment and placebo groups. These results reinforce the drug’s effectiveness in addressing the metabolic disturbances at the core of CTX.

The prescribing information for Ctexli includes a warning for liver toxicity.

Patients, especially those with pre‑existing liver disease or bile duct abnormalities, are advised to undergo liver blood tests before starting treatment, annually during therapy and as clinically indicated if symptoms such as abdominal pain, nausea or jaundice occur.

Currently, the cornerstone of CTX management is long‑term supplementation with chenodeoxycholic acid (CDCA), which normalizes bile acid synthesis and reduces toxic cholestanol buildup when initiated early.

Meanwhile, Vivet Therapeutics is advancing an investigational gene therapy candidate, VTX‑806, which employs an adeno‑associated virus (AAV) vector engineered to reinstate CYP27A1 enzymatic activity. Preclinical studies in a CTX mouse model demonstrated that VTX‑806 normalizes toxic bile acid metabolite levels in the blood, liver, tendons and brain.

In addition to its clinical promise, Mirum’s FDA approval of Ctexli has significantly bolstered its market position. A recent SWOT (strengths, weaknesses, opportunities and threats) analysis by Investing.com noted that this regulatory win has driven impressive stock performance and strengthened investor confidence.

Together, these developments highlight a multi‑pronged approach to addressing CTX and contribute to a broader movement toward targeted therapies for rare metabolic disorders.