FDA Casts Doubt on Alnylam Drug Trial Results for Expanded Usage

US regulators questioned the effectiveness of a drug made by Alnylam Pharmaceuticals Inc. as the company seeks approval for expanded use in treating a heart muscle disease called cardiomyopathy.

Onpattro’s effects compared to a placebo “were small, of questionable clinical meaningfulness, and may not be detectable by patients,” the US Food and Drug Administration wrote in documents posted Monday ahead of a meeting with Alnylam and expert advisors later this week. There were no major safety issues identified.

The drug, the company’s second best-selling, was initially approved in 2018 as a first-of-its-kind treatment for a rare genetic disease called polyneuropathy ...