Amylyx Pharmaceuticals is considering withdrawing its treatment for amyotrophic lateral sclerosis from the market after the drug failed to slow disease progression in a late-stage trial, sending its shares crashing 85% on Friday.

The company said it would stop promotions of the drug and decide on its future in coming weeks after discussions with regulators. Meanwhile, the drug will be available at this time.

"We will follow the science and will do what's right for the community, which may include voluntarily removing the product from the market," co-CEO Justin Klee said.

The drug, branded as Relyvrio and the company's only product in market, was approved in September 2022 based on mid-stage trial data in 137 patients that showed the treatment slowed disease progression and extended life expectancy.

But in the larger study of 664 patients, Relyvrio failed to confirm the reported benefit of slowing disease progression, with no significant difference seen in patients treated with the drug and placebo.

Amylyx's shares plunged 82% and were on track to wipe off more than $1 billion from its market value, if losses hold.

The drug, which has a list price of $158,000 per year in the United States, generated sales of about $381 million in 2023.

Relyvrio was approved after the U.S. Food and Drug Administration's advisers backed the drug in a rare turnaround, months after the panel rejected it for a lack of "substantially persuasive" data.

The approval followed months of lobbying by patients who urged the regulator to approve the drug based on its relative safety and the potential for increased survival.

"We are saddened by today's news and our hearts go out to everyone in the ALS community," the ALS Association said.

There are limited effective options to treat the disease, including Mitsubishi Tanabe's Radicava and the generic drug riluzole.

ALS causes progressive paralysis and death, and affects roughly 60,000 people in the U.S. and Europe.