Alnylam faces securities fraud probe after shares plunge on guidance cut

Glancy Prongay Wolke & Rotter LLP, a national shareholder rights law firm, is investigating potential securities law violations at Alnylam Pharmaceuticals (ALNY) after the Cambridge, Massachusetts-based RNA interference specialist slashed its revenue outlook, sending its shares tumbling nearly 30 per cent.

The inquiry centers on whether Alnylam may have misled investors ahead of its second-quarter 2026 results, which the company reported on July 30. In that update, Alnylam lowered its full-year net product revenue guidance for its transthyretin amyloidosis franchise by approximately $200mn, citing what it described as a normalization of growth in second-line patient volumes following an initial burst of demand from patients who had been waiting for a new therapy in the ATTR cardiomyopathy market.

Shares fell as much as $81.25, or 28.35 per cent, in intraday trading on the day of the announcement, erasing billions of dollars in market capitalization and prompting the law firm to solicit contact from shareholders who sustained losses.

The investigation is examining whether the company's prior statements about the trajectory of its TTR franchise adequately reflected conditions in the ATTR-CM market, or whether investors were given an overly optimistic picture of demand dynamics before the guidance was revised.