The European Medicines Agency (EMA) is leaning towards not approving Relyvrio, Amylyx Pharmaceuticals’ amyotrophic lateral sclerosis (ALS) drug, the company announced Tuesday.

A negative opinion from the regulatory agency would be a major setback for Amylyx, which has been pushing for a European approval for Relyvrio after winning approvals in both the U.S. and Canada.

In September, the Food and Drug Administration (FDA) approved Relyvrio amid controversy over its clinical benefit. That approval was based on results from the CENTAUR clinical trial, which showed a statistically significant benefit in function, as well as an observed benefit on survival in a long-term analysis, Amylyx said.

However, at the moment, the Committee for Medicinal Products for Human Use (CHMP), part of EMA, is leaning towards a ‘no’ on Relyvrio’s application. The EMA is expected to decide on Relyvrio’s approval sometime in June.

“We disagree with the current view expressed by the CHMP and remain confident in the data from the CENTAUR trial,” Tammy Sarnelli, global head of regulatory affairs and clinical compliance at Amylyx, said in a statement. “Should a negative opinion ultimately be issued, we intend to request a formal re-examination procedure.”

The ALS treatment’s rocky road to mainstream use continues with the likely objections of the EU health panel. Still, the drug has been boosted by a positive reception in North America.

Earlier this year, Amylyx noted that it was seeing higher-than-expected demand for the drug, despite some concerns around its efficacy. By the end of March, the company reported about 3,000 patients were taking the drug.

In May, Amylyx reported that Relyvrio brought in $71.4 million in Q1 2023, after generating $22.2 million in full-year revenue for 2022.

Patient advocates have supported approval of the drug, given the lack of effective treatments for the disease, which affects some 29,000 people in the U.S. and 30,000 people in Europe. Amylyx cited that demand in its latest statement.

“There has not been a new product approved in the European Union for ALS in over 25 years,” Stéphanie Hoffmann-Gendebien, head and general manager of international markets, EMEA at Amylyx, said. “We know from the European ALS community that there is a desperate need for new therapeutic options for this devastating disease, and timely access to safe and effective treatments is especially important.”

Not all are convinced that a European regulatory approval of Relyvrio is entirely a no-go, however. Even if the EMA chooses not to approve the drug this time around, Amylyx can file for a re-examination, which can lead to a different decision, according to analysts at Evercore ISI. 

“Furthermore, we dug up some stats which show that the CHMP changed their opinion ~39% of the time for drugs that were reexamined, which makes us believe that AMLX still has a shot for conditional approval in the EU,” the analysts wrote.