Alnylam faces securities probes after 28% stock plunge on guidance cut

Alnylam Pharmaceuticals faces securities investigations after its stock plunged 28 percent on July 30 when the company cut full-year TTR revenue guidance by $200 million.

Kirby McInerney LLP, Kessler Topaz Meltzer & Check LLP and the Law Offices of Frank R. Cruz have opened probes into whether Alnylam or members of senior management violated federal securities laws, the firms said in separate statements. No lawsuit has been filed, and the investigations remain ongoing.

On July 30, Alnylam reported second-quarter 2026 results and said it had "lowered our TTR product sales guidance for full-year 2026 to reflect learnings from the initial phase of our launch in the evolving ATTR-CM market, in particular the normalization of growth in second line volume after satisfying pent-up demand from patients waiting for a new therapy." The company cut total projected TTR net product revenues by approximately $200 million.

Shares of Alnylam fell $81.14, or about 28 percent, to close at $205.48 on July 30, with intraday losses reaching as much as $81.25, or 28.35 percent. The Cambridge, Massachusetts-based RNAi therapeutics company markets therapies for transthyretin amyloidosis, including the ATTR-CM indication that drove the launch.

The investigations center on whether the company's statements about the ATTR-CM launch and demand outlook misled investors before the guidance cut. The firms are seeking investors who purchased Alnylam securities and suffered losses, saying they may have legal rights under federal securities laws. Kessler Topaz, which has recovered more than $25 billion for clients, is among the firms soliciting affected shareholders.

The guidance shortfall reflects a launch dynamic specific to the ATTR-CM market, where patients who had been waiting for a new therapy drove an initial surge in second-line volume that has since normalized. Alnylam competes in that indication against established transthyretin amyloidosis treatments, and the demand reset raises questions about the durability of the product's growth trajectory.

For holders, the probes add legal and reputational risk on top of the guidance shortfall. Investors will watch for any formal complaint filing and for Alnylam's next quarterly report, due in late October, for updated TTR sales trends.

This article is for informational purposes only and does not constitute investment advice.