As of March 23, 2026 we found one new phase 3 trial of a product containing sodium phenyl butyrate. This trial failed to slow ALS. Since this is by far the largest and best ALS trial of a butyrate containing product, we change our trials grade from U to F. Details of this negative trial can be found here https://www.amylyx.com/news/
Key Information
Butyrates have plausible mechanisms for slowing ALS progression and positive pre clinical studies. One trial suggests that sodium phenylbutyrate (NaPB) in combination with Tauroursodeoxycholic acid (TUDCA) can slow ALS progression and prolong survival, but the specific contribution of NaPB toward this effect is unclear. Butyrates appear reasonably safe for use in humans. Based on the above information, we support a trial of a butyrate in PALS, but we cannot yet recommend one as a treatment.
https://www.tandfonline.com/doi/pdf/10.1080/21678421.2022.2045323