ALS Treatment Relyvrio Gets FDA Approval Despite Lingering Uncertainty About Effectiveness

A sign for the Food and Drug Administration is seen in Silver Spring
A sign for the Food and Drug Administration is seen in Silver Spring

AP Photo/Manuel Balce Ceneta

The U.S. Food and Drug Administration has approved a new treatment for amyotrophic lateral sclerosis, or ALS, months after an advisory committee voted that Phase 2 trials did not fully establish the drug's effectiveness.

On Thursday, the FDA announced that it had approved Relyvrio, which can be taken orally or via feeding tube, to treat patients with ALS.

The efficacy of the drug for ALS treatment was determined via a 24-week-long "multicenter, randomized, double-blind, placebo-controlled, parallel-group study" in which 137 adult patients with ALS received either Relyvrio or a placebo at random. It found that patients who received Relyvrio "experienced a slower rate of decline on a clinical assessment of daily functioning compared to those receiving a placebo," according to an FDA statement.

The FDA also noted in its statement Thursday that studies observed "longer overall survival" in patients who "originally received Relyvrio versus those who originally received placebo."

RELATED: Lindsey Vonn's Mother, Lindy Lund, Dies One Year After ALS Diagnosis: 'So Grateful for Every Moment'

However, the FDA's decision to approve the drug reverses an advisory committee's recommendation against doing so in March, in which it voted that the data from Amylyx Pharmaceutical's Phase 2 trial did not fully establish that the drug is effective.

"There are limitations to these findings that result in a degree of residual uncertainty about the evidence of effectiveness that exceeds that which might typically remain following a conclusion that substantial evidence of effectiveness has been demonstrated," reads an FDA summary memo regarding Relyvrio's approval. "However, given the serious and life-threatening nature of ALS and the substantial unmet need, this level of uncertainty is acceptable in this instance and consideration of these results in the context of regulatory flexibility is appropriate."

Tablet with the text ALS on the display
Tablet with the text ALS on the display

Getty Images

"The benefits of AMX0035 outweigh the risk, as the drug appears well tolerated without any significant safety signals of concern," the memo adds.

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up to date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.

Amylyx CEOs Joshua Cohen and Justin Klee said in a statement Thursday that the FDA's approval "is an exciting milestone for the ALS community and is a major step toward achieving our mission to one day end the suffering caused by neurodegenerative diseases."

"Our priority now is to ensure that adults living with ALS in the U.S. whose doctors have prescribed RELYVRIO can access it as quickly as possible," Amylyx COO Margaret Olinger added in a statement Thursday. "Physicians will be able to prescribe immediately, and we anticipate specialty pharmacies will be able to start to fill prescriptions and ship RELYVRIO to people with ALS in the next four to six weeks."

Though CNN noted that Amylyx's Phase 2 trial showed that Relyvrio is "generally well-tolerated," the company noted in its statement Thursday that the group that received the treatment in its trial experienced at least 5% more frequent "gastrointestinal-related adverse reactions" during the study, particularly in its first three weeks.

Amyotrophic lateral sclerosis - ALS
Amyotrophic lateral sclerosis - ALS

Getty Images

The FDA's Peripheral and Central Nervous System Drugs Advisory Committee voted 6-4 in March that Amylyx's Phase 2 trial did not fully establish that the drug is effective, according to CNN.

A larger Phase 3 trial involving around 600 patients is expected to complete in late 2023 or early 2024, according to the FDA's summary memo, which also noted that all members who previously voted against approving the drug acknowledged that the Phase 3 trial will "resolve the uncertainties on effectiveness of [Relyvrio]."

RELATED: Zac Brown Band's John Driskell Hopkins Reveals ALS Diagnosis in Video Message to Fans

Amylyx also indicated in its more recent meeting with the FDA that it would consider pulling the treatment from the market if its Phase 3 trials do not confirm the drug's efficacy, according to CNN.

"With today's approval, we are encouraged that RELYVRIO can offer people living with ALS and their families the potential of more time with functional independence," several U.S.-based ALS advocacy organizations said in Amylyx's statement Thursday. "This is especially important for a rapidly progressive disease with a median survival time from diagnosis of just two to three years."

"This is significant for people living with ALS, their loved ones, caregivers, clinicians, researchers, and advocacy, as we now have a new treatment option that could be a big step forward for the future of ALS care," the statement added.