Sodium phenylbutyrate/ursodoxicoltaurine

Sodium phenylbutyrate/ursodoxicoltaurine, also known as sodium phenylbutyrate/taurursodiol and sold under the brand names Albrioza and Relyvrio, is a fixed-dose combination medication used for the treatment of amyotrophic lateral sclerosis (ALS). It contains sodium phenylbutyrate and ursodoxicoltaurine (taurursodiol).

The most common adverse reactions experienced with sodium phenylbutyrate/ursodoxicoltaurine include diarrhea, abdominal pain, nausea and upper respiratory tract infection.

Sodium phenylbutyrate/ursodoxicoltaurine acts by blocking apoptotic pathways in the mitochondria and in the endoplasmic reticulum. Sodium phenylbutyrate is a chemical chaperone that helps proteins maintain their normal conformation, preventing aggregation that may lead to cell death. Ursodoxicoltaurine improves mitochondrial energy production.

The combination was approved for medical use in Canada as Albrioza, in June 2022, and in the United States, as Relyvrio, in September 2022. The European Union's drug regulators refused to approve it, citing concerns about effectiveness. In April 2024, the manufacturer announced that it is withdrawing the medication from the US and Canadian markets, due to it failing a key phase III clinical trial.