Amylyx to Pull ALS Drug Relyvrio From US, Canada Markets After Phase III Fail

Neurons, ALS_iStock, Dr_Microbe

Pictured: Illustration showing a neuron being destroyed/iStock, Dr_Microbe

Amylyx Pharmaceuticals on Thursday announced that it has started the process of pulling its amyotrophic lateral sclerosis drug Relyvrio (sodium phenylbutyrate and taurursodiol) from the U.S. and Canadian markets and will reduce the company’s workforce by approximately 70% under a restructuring plan.

Effective Thursday, Relyvrio will no longer be available for new patients. Those who are currently being treated with Relyvrio can either stay on treatment or transition into a free program, depending on their physician’s advice, according to the company. Amylyx said it will work with the FDA and Health Canada to terminate the marketing authorizations for Relyvrio in these countries.

Joshua Cohen and Justin Klee, co-CEOs of Amylyx, in a statement called the withdrawal of Relyvrio a “difficult moment” for the company and for patients with amyotrophic lateral sclerosis (ALS).

“The decision to remove Relyvrio from the market and provide therapy free of charge for those who wish to continue was informed by the PHOENIX trial results, engagement with regulatory authorities, and discussions with the ALS community,” Cohen and Keel said.

Last month, Relyvrio failed its highly anticipated Phase III PHOENIX trial, unable to significantly improve scores in the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale at 48 weeks versus placebo. Amylyx’s drug also fell short of its secondary endpoints, including slow vital capacity and self-reported health status, as measured by the Amyotrophic Lateral Sclerosis Assessment Questionnaire.

Amylyx will present data from PHOENIX at the upcoming American Academy of Neurology meeting, according to Thursday’s announcement. The study’s open-label extension phase is also ongoing, and Amylyx plans to collect survival data from the trial to help inform future studies in ALS.

Losing its only commercial product, Amylyx on Thursday also launched a sweeping restructuring initiative to cut costs and optimize the use of its resources, with an eye toward upcoming clinical milestones. The biotech will lay off around 70% of its employees and lower financial commitments outside of its new priority areas.

Amylyx will now focus on its lead asset AMX0035—which, like Relyvrio, also contains sodium phenylbutyrate and taurursodiol—being developed for Wolfram syndrome and progressive supranuclear palsy. The biotech is also advancing the antisense oligonucleotide candidate AMX0114 in ALS.

CMO Camille Bedrosian revealed in a statement that Amylyx will present Phase II data for AMX0035 in Wolfram syndrome later this month while its Phase III ORION study in progressive supranuclear palsy is set for an interim analysis in mid-2025. The biotech is also preparing to initiate a clinical trial for AMX0114 in the second half of 2024.

The company restructuring and priority changes should extend Amylyx’s cash runway into 2026, according to the announcement.

Tristan Manalac is an independent science writer based in Metro Manila, Philippines. Reach out to him on LinkedIn or email him at or

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