Draft guidance describes seven types of confirmatory evidence that can be used with one adequate and well-controlled clinical study to demonstrate substantial evidence of effectiveness, including evidence from expanded access, real-world data, and studies of other drugs in the same class.

In an interview with the Pink Sheet, Stealth’s CEO says she is not confident the company could design a clinical trial in the rare disease that would meet the FDA’s expectations.

The company reported 3,800 ALS patients on drug, a figure that came in slightly below some analyst estimates but which suggested discontinuation rates consistent with the pivotal trial.

Outcomes measures in the neurodegenerative disease space are not yet well understood by regulators, according to Amylyx, which recently received a negative opinion from the EMA for its amyotrophic lateral sclerosis drug, Albrioza.