Biotechnology company Ionis Pharmaceuticals Inc (Nasdaq:IONS) and its partner AstraZeneca plc (STO:AZN) (LON:AZN) (NYSE:AZN) reported on Thursday that the Phase 3 CARDIO-TTRansform trial of eplontersen in adults with transthyretin-mediated amyloid cardiomyopathy (ATTR-CM) did not meet its primary endpoint, with no statistically significant improvement versus placebo in the composite of cardiovascular mortality and recurrent cardiovascular events through Week 140.

In a prespecified subgroup analysis, patients receiving eplontersen monotherapy achieved a nominally significant hazard ratio of 0.71 versus placebo for the composite endpoint, while no treatment effect was observed in patients receiving stabiliser therapy at baseline. Secondary, imaging and biomarker analyses favoured eplontersen over placebo, with large and sustained reductions in transthyretin levels, and the therapy demonstrated a favourable safety profile consistent with previous findings.

The trial enrolled patients receiving standard of care, with 57% in each study arm on stabiliser therapy at baseline and an additional 24% initiating stabiliser treatment during the study.

Ionis and AstraZeneca said they will continue analysing the full data set and plan to present the results at the European Society of Cardiology Congress in August 2026.