Ionis Pharmaceuticals Faces Investor Probe After Heart Drug Trial Fails
Ionis Pharmaceuticals shares dropped more than 23% following the announcement that a late-stage trial for an experimental heart disease therapy did not meet its primary endpoint. An investor rights law firm has launched an investigation.
Investors in Ionis Pharmaceuticals (NASDAQ: IONS) saw share prices decline by over 23% on July 9, 2026, after the company and its partner AstraZeneca announced that a late-stage trial for an experimental heart disease therapy failed to meet its primary efficacy endpoint.
The unexpected outcome has prompted Hagens Berman, a national law firm specializing in shareholders' rights, to launch an investigation. The firm is examining whether Ionis was adequately transparent with investors about the trial's data and design, and if potential violations of federal securities laws occurred.
The investigation centers on Ionis' prior statements regarding the development of eplontersen, a drug intended to treat transthyretin amyloid cardiomyopathy (ATTR-CM). Ionis had previously described the Phase 3 CARDIO-TTRansform study as the largest ever conducted in ATTR-CM and assured investors of its smooth progress.
However, the company revealed on July 9 that adding eplontersen did not provide a statistically significant benefit in patients already receiving standard care, including a majority on a stabilizer treatment. This revelation led to a market capitalization loss exceeding $3.3 billion for Ionis.