Despite FDA Doubts, Adcomm Backs Alnylam's Gene Silencing Therapy For Expanded Use Into Rare Heart Disease

On Wednesday, an FDA advisory committee voted 9-3 in favor of Alnylam Pharmaceuticals Inc's ALNY patisiran. It has a favorable benefit-risk profile in cardiomyopathy of transthyretin-mediated (ATTR) amyloidosis.

ATTR is caused by misfolded transthyretin (TTR) proteins, accumulating as amyloid deposits in various body parts, including the heart, resulting in cardiomyopathy and heart failure.

Patisiran is designed to target and silence TTR messenger RNA, thereby reducing the production of TTR protein before it is made. Reducing the pathogenic protein leads to a reduction in amyloid deposits in tissues.

The FDA has set an action date of October 8, 2023, under the Prescription Drug User Fee Act.

FDA panel backing represents a potential opportunity for Alnylam to challenge Pfizer Inc's PFE market dominance with tafamidis, sold under Vyndaqel and Vyndamax, in treating ATTR-CM. The two drugs together generated $2.4 billion in revenue last year. 

In 2018, the FDA approved patisiran, as Onpattro, to treat polyneuropathy (nerve damage) of hereditary ATTR amyloidosis in adults.

The favorable vote contrasts with doubts the FDA's staffers raised earlier this week.

In a briefing document released before the Cardiovascular and Renal Drugs Advisory Committee, the FDA questioned the drug's efficacy.

For Alnylam's Onpattro application in ATTR-cardiomyopathy, the drug's efficacy data in a phase 3 trial were "small, of questionable clinical meaningful, and may not be detectable by patients," the FDA's drug reviewers said in a briefing document.

In addition, the regulator said, "the effects of patisiran compared to placebo on 6MWT appeared confined to patients, not on background therapy with tafamidis."  

Price Action: ALNY shares are up 4.80% at $211.65 premarket on the last check Thursday.