Ionis Pharmaceuticals IncLate-stage trial for eplontersen failed to meet primary endpoint, causing 23% share drop.
Ionis Pharmaceuticals shares plunged 23% on July 9, 2026 after its late-stage CARDIO-TTRansform trial for eplontersen failed to meet its primary endpoint in transthyretin amyloidosis cardiomyopathy. The company and partner AstraZeneca revealed that adding eplontersen did not provide a statistically significant benefit in a patient population where 57% were on a stabilizer at baseline and another 24% initiated one during the trial. The market reaction erased over $3.3 billion in market capitalization. National shareholders' rights firm Hagens Berman has opened an investigation into whether Ionis was sufficiently transparent about the trial's data and design, citing prior assurances that the study was the largest ever in ATTR-CM and that execution was going very well. One analyst reportedly noted that more than 80% of participants were on a stabilizer, driving the primary endpoint failure.
Ionis Pharmaceuticals IncLate-stage trial for eplontersen failed to meet primary endpoint, causing 23% share drop.
AstraZeneca PLCPartner's trial failure for eplontersen in ATTR-CM, though AstraZeneca is not the primary subject.