Ionis Pharmaceuticals IncPhase 3 trial of eplontersen failed to meet primary efficacy endpoint, causing 23% stock drop.

Ionis Pharmaceuticals is under investigation by shareholders' rights firm Hagens Berman after a late-stage trial failure for its heart disease therapy caused the stock to plunge 23% on July 9, 2026. The Phase 3 CARDIO-TTRansform study of eplontersen for transthyretin amyloidosis cardiomyopathy did not meet its primary efficacy endpoint, with the company revealing that 57% of patients in each arm were on a stabilizer at baseline and another 24% initiated one during the trial. The market reaction wiped out over $3.3 billion in market capitalization. Hagens Berman is examining whether Ionis was sufficiently transparent about the trial's data and design, particularly given prior assurances that the study was progressing well and would yield a rich dataset. The firm is encouraging investors who suffered substantial losses to come forward.
Ionis Pharmaceuticals IncPhase 3 trial of eplontersen failed to meet primary efficacy endpoint, causing 23% stock drop.