Dive Brief:

• The Food and Drug Administration will spend more time reviewing a closely watched treatment for ALS, the drug’s developer, Amylyx Pharmaceuticals, revealed Friday, announcing the agency delayed its expected decision by three months.

• The FDA now expects to reach a verdict on the drug, known as AMX0035, by Sept. 29 rather than the previously set target decision date of June 29. Amylyx said it had submitted additional data from its clinical trial, which the FDA judged to be a “major amendment” to the company’s approval application.

• “We are confident in the potential of AMX0035 to help people living with ALS and other neurodegenerative diseases, and we continue to work closely with the FDA as they complete their review,” Justin Klee and Joshua Cohen, Amylyx’s co-CEOs and cofounders, said in a statement.

Dive Insight:

The FDA doesn’t disclose its rationale for extending drug reviews and Amylyx’s statement on the delay offered few details, making it hard to tell how the agency views the company’s application.

Two months ago, expert advisers convened by the FDA recommended the regulator hold off on approving Amylyx’s medicine, having grappled with several issues in how the main study supporting its benefit was run and analyzed. In documents prepared for the meeting, and in presentations to the experts, FDA officials acknowledged the devastating nature of ALS and their promises to be more flexible in reviewing drugs for the condition. But they also questioned how effective AMX0035 really is.

Amylyx is currently running a larger study of AMX0035 to confirm the benefits it observed in earlier testing, and expects to complete the trial by March 2024.

As one of the few ALS drugs to have shown a statistically significant benefit in testing, AMX0035 has become closely followed by ALS patients and physicians. The FDA’s eventual decision will likely attract considerable scrutiny, particularly after the same division at the regulator controversially cleared Biogen’s Alzheimer’s drug Aduhelm last year, despite conflicting evidence.

“Following the disappointing [advisory committee meeting], the investment community has expected AMX0035 to not get approved by the FDA,” wrote SVB Securities analyst Marc Goodman in a client note sent after Amylyx announced the three-month delay. ”[B]ut it appears that the FDA is still struggling with its decision.”

Shares in Amylyx rose by more than 20% in Friday trading on the news.