The investigation centers on the company's July 30, 2026, financial update, in which Alnylam lowered its full-year product sales guidance for the ATTR-CM market. Management attributed the revision to a normalization of growth in second-line volume, noting that initial pent-up demand had been largely satisfied. This disclosure resulted in a sharp market reaction, wiping out more than a quarter of the company's valuation in a single session.

Kessler Topaz Meltzer & Check, a Radnor-based firm specializing in investor protection, is inviting shareholders who sustained financial losses to review their legal options. The firm, which has historically managed large-scale recoveries in securities litigation, is assessing whether the company provided adequate information to investors prior to the guidance adjustment. No formal class action has been filed, and the inquiry remains in the preliminary stages.