U.S. FDA panel backs expanded use of Alnylam's gene silencing drug

FILE PHOTO: Signage is seen outside of FDA headquarters in White Oak, Maryland

(Reuters) - An outside panel of experts to the U.S. Food and Drug Administration on Wednesday backed the expanded use of Alnylam Pharmaceuticals' gene silencing drug to treat a type of heart disease associated with a rare organ-damaging disorder.

The FDA panel voted 9 to 3 that the benefits of the drug, patisiran, outweigh its risks for treating patients with a type of heart muscle disease, cardiomyopathy, caused by a wild-type or hereditary transthyretin-mediated amyloidosis (ATTR).

ATTR, caused by mutations in the transthyretin gene, leads to accumulation of faulty proteins in body organs and tissues that can lead to loss of sensation, heart issues, eye, kidney and thyroid diseases.

The panelists, however, were concerned about the meaningfulness of the drug's benefit.

"There is a light wind for benefit and no wind for risk," said Dr. Edward Kasper, one of the panelists.

The FDA, which usually follows the recommendations of its expert panel but is not obligated to do so, is expected to make its final decision on the drug by Oct. 8.

The FDA staff reviewers had highlighted in briefing documents released on Monday that the effects of patisiran compared to placebo were "small, of questionable clinical meaningfulness, and may not be detectable by patients".

Patisiran uses RNA interference (RNAi), a Nobel prize-winning mechanism, to target and "silence" specific genetic material, and block the production of the deadly protein.

In 2018, patisiran branded as Onpattro became the first such treatment approved in the United States to treat nerve damage in adult patients with hereditary ATTR.

About 5,000 to 7,000 new cases of ATTR-related cardiomyopathy are identified annually in the United States, according to government data.

(Reporting by Mariam Sunny in Bengaluru; Editing by Shailesh Kuber)