Potential Label Restrictions Loom For Alnylam's Patisiran Despite Approval Prospects

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 the cardiomyopathy of transthyretin-mediated (ATTR) amyloidosis. 

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

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

While the committee's concerns about the degree of benefit, lack of outcomes data, and limited information on combination use with tafamidis are understandable, William Blair (Reiterates Outperform rating) maintains that the study showed statistical significance on measures deemed acceptable by the FDA and is, therefore, approvable.

Needham (Reiterates Buy rating & $240 PT) writes that the positive vote mitigates some approval risk and puts the approval probability of success at ~80%. The analyst acknowledges that investors may have concerns over a potentially restrictive label or how the FDA's relatively pessimistic tone on the treatment effect will impact the approval decision, resulting in shares being down on these concerns.

Stifel (Buy rating with $240 PT) says that as the panel votes are non-binding, the FDA is not bound to follow the recommendation, and the analyst would not be surprised either way. In turn, ALNY shares may be volatile as the Onpattro probability of label expansion is around 50/50 now, though the big picture around HELIOS-B is unchanged.

Cantor Fitzgerald (Reiterates Neutral rating & $190 PT) notes that the FDA is leaning towards a CRL - and a narrow label would probably be a "best-case" scenario for ALNY.

But if the drug does get approved, it would carry a very restricted label, with limited use to tafamidis-naive patients and no inclusion of cardiovascular benefit language on the label.

Price Action: ALNY shares are down 8.08% at $194.55 on the last check Thursday.