FDA Rejects Alnylam’s Expanded Approval Request for RNA Drug Patisiran in Rare Heart Condition

The FDA has declined Alnylam Pharmaceuticals’ request to expand the approval of its RNA drug, patisiran, for individuals with a rare genetic heart condition, marking a significant setback for the company’s plans.

Alnylam Pharmaceuticals’ bid for expanded FDA approval of its RNA drug, patisiran, for use in individuals with a rare genetic heart disorder has been rejected. Alnylam revealed in a statement issued on Monday that the FDA found the clinical trial data provided by the company insufficient to establish the “clinical significance of patisiran’s therapeutic effects” for the specific condition, known as cardiomyopathy of ATTR amyloidosis. As per the biotech company’s statement, the FDA’s comprehensive response letter did not identify any further issues concerning clinical safety, the execution of the study, drug quality, or manufacturing.

In light of this decision, Alnylam has abandoned its plans to pursue an expanded approval for patisiran. The drug is already approved in the United States under the name Onpattro for individuals with ATTR amyloidosis who have polyneuropathy (nerve damage). Instead, the company will shift its focus toward a follow-up medication called vutrisiran, which is currently undergoing evaluation in a study called HELIOS-B, specifically for the cardiomyopathy subtype of the disease.

The FDA’s ruling did not come as a complete surprise, as FDA experts had previously raised doubts about the true benefits of the RNA-based medication for individuals with ATTR amyloidosis suffering from heart-related damage. Nonetheless, during the same regulatory meeting, the FDA’s advisors voted by a margin of 9-3 in favor of the belief that the advantages of patisiran outweigh its risks when used in the treatment of cardiomyopathy associated with ATTR amyloidosis. While the FDA is not legally bound to adhere to the guidance of its consultants, it generally adheres to their recommendations. Therefore, the FDA’s unfavorable decision in this case is rather uncommon.

ATTR amyloidosis is characterized by the harmful accumulation of mutated transthyretin (TTR) protein in nerves and organs, resulting in tissue damage. In 2018, Onpattro received FDA approval for treating the less common polyneuropathy form of this condition. Pfizer’s tafamidis, available as Vyndaqel and Vyndamax, is currently accessible for ATTR amyloidosis patients with heart-related symptoms and is supported by clinical trial data illustrating its ability to prolong patients’ lives and reduce heart-related hospitalizations.

In contrast, Alnylam has only shown that patisiran can enhance the physical functioning and quality of life of these patients. These findings originate from a trial called APOLLO-B, which assessed patisiran based on two primary criteria.

During the recent FDA meeting involving external experts, some of the agency’s advisors deliberated on the extent of patisiran’s benefits in the APOLLO-B trial. They highlighted that specific subgroups, including women, Black participants, and those who had received tafamidis at the outset of the trial, did not appear to experience substantial benefits from one or both of the trial’s assessments. Nevertheless, the panel ultimately endorsed patisiran, citing its manageable side effects and modest therapeutic advantages.

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