The US Food and Drug Administration (FDA) voted nine to three in favour of expanding the label of Alnylam Pharmaceuticals’ Onpattro (Patisiran) at a 13 September Advisory Committee (AdCom) meeting.

A possible approval would allow the drug to be used to treat cardiomyopathy caused by a wild-type or hereditary transthyretin-mediated amyloidosis (ATTR/ ATTR-CM).

At a Cardiovascular and Renal Drugs AdCom meeting, a panel reviewed results from the Phase III (NCT03997383) APOLLO-B trial. In the study, the drug showed favourable effects on functional capacity and quality of life. The drug also demonstrated a good safety profile through the 18 months of treatment with most adverse events being mild or moderate, as per May 2023 interim results.

The AdCom discussed if the results from the APOLLO-B study were enough to prove a clinically meaningful benefit for the drug in the new indication. Dr Eric Peterson, a professor of internal medicine at the University of Texas Southwestern Medical Center, voted against the drug’s approval. While the Phase III results were statistically significant, the benefit was not enough, he said. Another panellist, Johns Hopkins University's outpatient cardiology director Dr Edward Kasper said: “There is a light wind for benefit and no wind for risk,” explaining his thoughts that the small benefit seen should still warrant approval.

ATTR-CM is an underdiagnosed rare condition that results from the misshaping and build-up of transthyretin, a protein that normally circulates in the bloodstream. This causes the protein to build up in the heart, nerves, and other organs.

The FDA first approved the drug in 2018 for the treatment of hereditary ATTR amyloidosis polyneuropathy. This was the agency’s first-ever approval for an RNA interference therapeutic. Onpattro works by blocking the effects of the genetic abnormality in hATTR amyloidosis, reducing the amount of mutant or wild-type TTR present in the liver.

The FDA has set a PDUFA target action date of 8 October.