Regulators who recommend whether new medicines should be approved in Europe are opposing a new ALS drug developed by the Massachusetts-based biotechnology company Amylyx Pharmaceuticals.

The drug received approval last year in both the U.S. and Canada, where it’s respectively sold under the brand names Relyvrio and Albrioza. Amylyx has been trying to get it authorized in Europe as well, and submitted a marketing application in early 2022.

Last month, the company said it was informed the Committee for Medicinal Products for Human Use — which is part of the European Medicines Agency, a regulatory body equivalent to the Food and Drug Administration — was “trending toward a negative opinion.” And in a meeting earlier this week, the committee formally recommended that the drug not be authorized by the European Commission.

In their opinion, the regulators expressed concern with the main study meant to show Amylyx’s drug is safe and effective. The study found patients who received the drug declined a small, but significant amount less than those given a placebo, and also lived a median five months longer.

But these results weren’t enough to convince the CHMP that Amylyx’s drug effectively slows the progression of ALS, or amyotrophic lateral sclerosis. For example, the survival data were “not reliable, given the way the data were collected and analyzed,” according to the committee.

The committee said it considered advice from various groups, including patient representatives and neurology experts. Ultimately, though, it concluded that “a positive balance of benefits and risks … could not be established,” and therefore sided against approval.

Amylyx’s global head of regulator affairs and clinical compliance, Tammy Sarnelli, said in a statement that the company disagrees with the committee’s opinion and will request a re-examination of the approval application. The re-examination process takes about four months, according to Amylyx, and appoints a different “rapporteur” and “co-rapporteur” from the initial evaluation.

There are currently few treatment options for ALS, a nerve-destroying illness that erodes a person’s ability to perform essential functions like walk, talk, eat and breathe. Typically, the disease is fatal within two to five years after symptoms start to show.

Amylyx’s drug is one of the few to have generated positive results in clinical testing. The size of the effect was relatively small, though, and there remains debate about how helpful it really is.

Still, for many patients and caregivers, the drug has become a rare source of hope.