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# FDA Approves Relyvrio for ALS After 137-Patient Trial and Divided Review, Adding First New U.S. Treatment Since 2017
- URL: https://www.theamericanquorum.com/taq-historical-2022-10-01-healthcare/
- Published: 2022-10-02T03:59:00.000Z
- Updated: 2022-10-02T03:59:00.000Z
- Description: FDA approved Relyvrio for adults with ALS after a 137-patient trial showed slower functional decline, ending a divided review while a larger confirmatory study continues.
- Author: Kenneth R. Deans Jr.
- Tags: Healthcare, #Import 2026-08-31 17:02

The Food and Drug Administration has approved Relyvrio, an oral combination of sodium phenylbutyrate and taurursodiol, for adults with amyotrophic lateral sclerosis, adding a new treatment option for a progressive and fatal neurological disease after an unusually closely watched review centered on a 137-patient clinical trial.

The agency announced the [September 29 approval](https://www.fda.gov/news-events/press-announcements/la-fda-aprueba-nueva-opcion-de-tratamiento-para-pacientes-con-ela?ref=theamericanquorum.com) for all adults with ALS. The drug, developed by Amylyx Pharmaceuticals and previously known as AMX0035, is taken once daily for the first three weeks and then twice daily. FDA said the most common adverse reactions in the clinical program included diarrhea, abdominal pain, nausea and upper respiratory tract infection.

## A small trial showed slower functional decline

The approval rests primarily on the CENTAUR study, a 24-week randomized, double-blind, placebo-controlled trial conducted at 25 U.S. sites. FDA’s [Drug Trials Snapshot](https://www.fda.gov/drugs/drug-approvals-and-databases/drug-trials-snapshots-relyvrio?ref=theamericanquorum.com) says 137 adults with ALS were randomized to receive Relyvrio or placebo, with benefit measured using the ALS Functional Rating Scale-Revised, a standard instrument that tracks abilities such as walking, speaking, swallowing and breathing.

The peer-reviewed [CENTAUR results](https://www.nejm.org/doi/full/10.1056/NEJMoa1916945?ref=theamericanquorum.com), published in the New England Journal of Medicine in 2020, found that ALSFRS-R scores declined by an average of 1.24 points per month in the treatment group and 1.66 points per month with placebo, a difference of 0.42 points per month. Secondary outcomes did not differ significantly between groups, and the investigators said larger and longer studies were needed to establish the treatment’s efficacy and safety more fully.

FDA also cited a post hoc long-term analysis in which patients originally assigned to Relyvrio showed longer overall survival than those originally assigned to placebo. That survival analysis was supportive rather than the trial’s original primary endpoint, an important distinction in understanding why the evidence generated substantial debate.

## The regulatory path was unusually contested

Relyvrio reached approval after the FDA’s Peripheral and Central Nervous System Drugs Advisory Committee considered the application twice. In March, the committee narrowly concluded that the available evidence did not yet establish effectiveness. FDA later reconvened the panel after receiving additional analyses and commitments from Amylyx concerning a larger confirmatory trial.

At the September 7 meeting, the advisory committee voted 7-2 that the evidence was sufficient to support approval. Amylyx summarized the [committee vote](https://investors.amylyx.com/news-releases/news-release-details/amylyx-pharmaceuticals-announces-fda-advisory-committee-supports?ref=theamericanquorum.com) after the meeting, saying the company continued to enroll a phase 3 study intended to provide more definitive evidence.

The final [FDA approval package](https://www.accessdata.fda.gov/drugsatfda%5Fdocs/nda/2022/216660Orig1s000Approv.pdf?ref=theamericanquorum.com) confirms that New Drug Application 216660 is approved for treatment of ALS in adult patients and imposes postmarketing requirements, including additional studies of carcinogenicity, drug interactions and pharmacokinetics. The approval therefore allows broad adult use while continuing to require further safety characterization.

## ALS leaves little room for regulatory delay

The debate around Relyvrio reflects the particular difficulty of drug development in ALS. The disease destroys motor neurons, progressively depriving patients of voluntary movement, speech, swallowing and breathing. FDA says most cases lead to death from respiratory failure within three to five years after symptoms begin. Approximately 5,000 people in the United States are diagnosed each year, with roughly 20,000 Americans living with the disease.

That clinical urgency has shaped patient advocacy. The ALS Association, which helped fund development of AMX0035 with money raised through the Ice Bucket Challenge, called the approval a major milestone in a [September 29 statement](https://www.als.org/stories-news/fda-approves-first-als-treatment-funded-ice-bucket-challenge?ref=theamericanquorum.com). The organization said it invested $2.2 million in the drug’s development and trial and had urged regulators to make the treatment available before completion of the larger phase 3 study.

Patient groups have argued that people facing a rapidly progressive fatal disease should be able to accept greater uncertainty when a treatment has a plausible benefit and manageable known risks. Critics of accelerated decision-making counter that small studies can overestimate effects and that approval can make it harder to determine whether a therapy truly changes disease progression.

## The treatment combines two compounds aimed at cellular stress

Relyvrio combines sodium phenylbutyrate and taurursodiol, compounds intended to address cellular pathways associated with endoplasmic-reticulum stress and mitochondrial dysfunction. The biological rationale is that reducing stress within motor neurons could help preserve function, although the exact contribution of each component to the observed clinical effect is not established.

Amylyx said in its [approval announcement](https://investors.amylyx.com/news-releases/news-release-details/amylyx-pharmaceuticals-announces-fda-approval-relyvriotm?ref=theamericanquorum.com) that Relyvrio can be used as a standalone therapy or alongside existing ALS treatments as clinically appropriate. The drug is mixed with eight ounces of room-temperature water and can be taken orally or administered through a feeding tube.

The approval expands a limited treatment landscape that already includes riluzole and edaravone. None cures ALS, and the practical value of a new therapy will depend on whether its modest average effect on functional decline translates into meaningful preservation of independence for individual patients.

## A larger trial remains central to the evidence question

Relyvrio’s approval does not resolve the underlying scientific uncertainty. The pivotal study was small, and FDA’s own review process exposed disagreement about how much weight to place on its primary functional result, survival analyses and the severe unmet need in ALS. The ongoing confirmatory trial will therefore carry unusual importance for clinicians, patients and regulators.

The decision nevertheless changes the immediate choices available to adults with ALS. Physicians can now prescribe a third disease-directed therapy while discussing the limitations of the evidence, gastrointestinal adverse effects, potential drug interactions and the still-evolving understanding of long-term benefit.

For the ALS community, the approval represents both progress and a test of a regulatory model built around urgent access under uncertainty. FDA has chosen to make the treatment available now rather than wait for a larger trial, while requiring additional evidence after approval. The effectiveness of that balance will depend on how clearly future studies define what Relyvrio can—and cannot—do for people living with ALS.