Despite questions about the therapy's effectiveness, the FDA approved an experimental treatment for A.L.S.

The treatment, conceived about a decade ago by two college students, was approved even though analyses by the F.D.A.'s reviewers concluded there was not yet enough evidence that the medication could help patients live longer or slow the rate at which they lose functions. The agency decided to approve the drug without waiting for the results of a large clinical trial because of data showing the treatment to be safe and the desperation of patients with a disease that often causes death within two-to-five years.

The drug will be called Relyvrio.

Given the serious and life-threatening nature of A.L.S., the level of uncertainty about the evidence of effectiveness is acceptable. The benefits outweigh the risks because the treatment is safe, according to the memorandum.

Patients and advocacy groups have been campaigning for months. Doctors who treat A.L.S. patients wrote letters to the F.D.A. and testified before an F.D.A. advisory committee.

The director of the A.L.S. clinic at Duke University testified this month that there is always a chance that a mistake will be made. People with A.L.S. got to try something that looked promising in two years, so I don't think they'll be angry.

He wondered if it was a mistake to say no and then get confirmatory evidence in two years. All those patients were disabled or dead when they didn't need to be. If you make that mistake, I don't know how you'll live with yourself.

About 6,000 people are diagnosed with A.L.S. every year. The two approved A.L.S. medications in the US are riluzole and edaravone.

The creators of Relyvrio were undergrad students at Brown University. They proposed that combining two drugs used to treat urea disorders could protect the brain from damage caused by A.L.S. Amylyx Pharmaceuticals was founded by them.

Some patients obtained the ingredients on their own after learning about the compound. Canada became the first country to approve the treatment after Amylyx provided better evidence that it worked. If the F.D.A. didn't approve it, some American patients would go to Canada to get it.

ImageJustin Klee and Joshua Cohen, wearing business-casual suits, stand on a grassy area next to a red brick building.
The two-drug combination was conceived by Justin Klee, left, and Joshua Cohen when they were undergraduates at Brown University.Credit...Cody O’Loughlin for The New York Times
Justin Klee and Joshua Cohen, wearing business-casual suits, stand on a grassy area next to a red brick building.

Amylyx didn't say what price it was considering for the treatment in the US, but it did say that the price was still being negotiated in Canada.

Everyone who is eligible for Relyvrio will have access as quickly and efficiently as possible as we know people with A.L.S. and their families have no time to wait.

The medication, a bitter-tasting powder mixed with water and consumed through a feeding tube, traveled an unusual path to approval. Phase 3 trials are larger and more extensive than Phase 2 studies. One trial and additional confirmatory data can be accepted for serious diseases.

The data for Relyvrio comes from a single Phase 2 trial in which 137 patients took the drug or placebo and an extension study that followed some patients after the trial ended.

Patients in the second trial were considered to have fast-progressing disease. Most of the people received Relyvrio. They experienced a 25 percent slower decline than placebo, which was 2.32 points lower on the A.L.S. scale.

The placebo group started taking the medication about seven months after those who received it from the beginning. According to Amylyx, patients who received the longest treatment had more time before being hospitalized, put on a ventilator or die. Another analysis was published that suggested benefits.

Amylyx should not be approved until the Phase 3 trial is done, according to the F.D.A.

The F.D.A. approved the Alzheimer's drug Aduhelm despite doubts about its effectiveness. F.D.A. officials suggested that Amylyx submit an application for approval.

In March, a committee of independent advisers to the F.D.A. voted by a narrow margin that the treatment had not yet been shown to work. After allowing Amylyx to submit more data, the agency scheduled a second independent advisory committee meeting in September. Reviewers said in the report that the new data was insufficient.

The director of the F.D.A.'s office of neuroscience told the advisory committee that although some might argue that substantial evidence does not currently exist to justify approval, the agency should also consider seriousness.

If the treatment received approval now and was shown to be useless in the trial, would Amylyx voluntarily withdraw it from the market? The company would.

Amylyx's commitment and emotional testimony from patients and doctors persuaded more advisory committee members to vote in favor of the project.

One of the people who voted against approval was a doctor from the National Institutes of Health.

Mark Weston is a member of the advisory committee and he was disappointed that the new information the company presented wasn't stronger. He was hoping for more. Mr. Weston said he voted for approval because he couldn't ignore his thoughts about the unmet need.

Patients who testified said that they needed treatments. In testimony read by a friend, Brian Wallach said that he wanted you to recommend approval so that he could live.

The rate of functional decline has slowed considerably since Gregory began taking the drug over three years ago.

The basement is where we start the stairs. Each step up is important to point us in the right direction.

The president and CEO of the A.L.S. Association said that the F.D.A. decision was a victory for the entire community. The association met with F.D.A. officials and submitted a petition with over 50,000 signatures.

The A.L.S. Association contributed more than two million dollars to the development and study of AMX0035. The sales of the drug will be used to repay the association's grant.