On 29 September 2022, the US Food and Drug Administration (FDA) approved AMX0035 (sodium phenylbutyrate and ursodoxicoltaurine) for the treatment of adults with amyotrophic lateral sclerosis (ALS) under the brand name RELYVRIO.

Marketing authorisation was applied for in the European Union (EU) and initially not granted, with the reasoning that the results of the Phase III trial (PHOENIX trial) should be awaited first. These were not available until early 2024. The Phase III trial was negative in all study objectives.

As a result, it was clear that RELYVRIO would not be authorised in the European Union (EU). The company Amylyx also withdrew the marketing authorisation in the countries where it had already been granted (USA, Canada), meaning that this therapy is no longer available and cannot be recommended based on the current study situation.