Results from a roughly 140-person clinical trial published in The New England Journal of Medicine showed those given Relyvrio as opposed to a placebo appeared to decline a little slower and live a median of five months longer. The trial represented a rare win in a notoriously difficult area of drug development. Yet, the Food and Drug Administration wasn't entirely convinced the results were persuasive enough to grant an approval. The FDA twice convened outside experts to weigh the pros and cons of Relyvrio. And, during the second of those meetings, a top agency official called on Amylyx to commit to a market withdrawal if it didn't succeed in confirmatory testing. Amylyx pledged to do so, and by the fall of 2022, had secured approval in the U.S. and Canada. Since then, the drug has been met with high demand. Nearly 4,000 of the approximately 30,000 ALS patients in the U.S. were on Relyvrio by the end of last September.