Amylyx Pharmaceuticals announced it will voluntarily halt sales and marketing of the drug in the U.S. and Canada, where new patients will no longer be able to get a prescription.

“While this is a difficult moment for the ALS community, we reached this path forward in partnership with the stakeholders who will be impacted and in line with our steadfast commitment to people living with ALS,” company executives said in a statement. Patients already taking the therapy who wish to continue will be able to enroll in a program to receive it for free.

The Food and Drug Administration approved the much-debated drug, Relyvrio, in September 2022, following a years-long advocacy campaign by patients with amyotrophic lateral sclerosis, or ALS.

The drug’s failure is a bitter disappointment for patients and advocates, who have pressed the FDA and other federal agencies to fund and approve more experimental therapies for the fatal muscle-wasting disease.

Relyvrio’s withdrawal leaves just three ALS medicines available to U.S. patients, only one of which has been shown to extend survival by several months.

Cambridge, Massachusetts-based Amylyx said in March it was considering pulling its drug after a clinical trial in 600 patients failed to show any improvements in survival or other health measures, such as muscle strength or walking ability.

The company’s voluntary action resolves what could have been a major dilemma for the FDA. The agency’s regulators would not have had a clear path to quickly force the drug from the market if the company had refused to remove it. That’s because the FDA granted the drug full approval, despite the preliminary nature of the company’s data on effectiveness.

The 2022 approval was mainly based on results from one small, mid-stage study that was criticized by some of the agency’s own internal scientists. Normally the agency requires two large, late-stage studies that show a clear benefit before granting approval. But at the time FDA officials explained that “regulatory flexibility” was appropriate when reviewing Relyvrio, “given the serious and life-threatening nature of ALS and the substantial unmet need.”

The medication is part of a string of drugs for deadly, degenerative diseases that have won FDA approval in recent years despite questionable evidence they work.

ALS gradually destroys the nerve cells and connections needed to walk, talk, speak and breathe. Most patients die within three to five years of a diagnosis.

Relyvrio is a powder that combines two older drugs: a prescription medication for liver disorders and a dietary supplement associated with traditional Chinese medicine.

Amylyx faced criticism for pricing the drug at $158,000 for a year’s supply. Sales were disappointing, with some patients discontinuing the medicine after only a few months.