Why did the CARDIO-TTRansform trial fail to show a statistically significant benefit in the primary endpoint?

The trial took place within a rapidly shifting clinical landscape where a high percentage of contemporary ATTR-CM patients are already treated with baseline stabilizer therapies. Specifically, 57% of participants were taking a stabilizer at baseline and another 24% initiated one during the study, masking any incremental treatment effects from adding eplontersen.

What specific findings were observed in the prespecified subgroup analyses?

In a distinct subgroup tracking patients who received eplontersen as a monotherapy rather than in combination with standard stabilizers, researchers observed a nominally significant hazard ratio of 0.71 against the placebo group. Conversely, no treatment effect or clinical divergence was seen in patients who were already on stabilizer therapy at baseline.

What secondary measures and biological markers favored eplontersen during the Phase 3 study?

Across the global study population, multiple secondary clinical targets, cardiac imaging results, and structural biomarker analyses trended in favor of the active treatment over placebo. Eplontersen successfully drove deep, sustained reductions in overall transthyretin (TTR) proteins, matching the expectations for its underlying therapeutic class.

What are the primary characteristics and physical symptoms of ATTR-CM?

ATTR-CM is a progressive and often fatal disease that occurs when misfolded TTR proteins form amyloid fibril deposits within the heart, weakening its structural pumping ability. Patients frequently encounter non-specific symptoms such as severe shortness of breath, heart palpitations, chronic swelling, dizziness, and intense fatigue.

When and where will Ionis and AstraZeneca present the full dataset to the clinical community?

The joint clinical teams are finalizing deep-dive reviews of the comprehensive trial spreadsheets and imaging registers. The full findings are officially scheduled to be unveiled and discussed at the upcoming European Society of Cardiology (ESC) Congress in August 2026.

Image for illustrative purposes only. Not a real photo.

Ionis and AstraZeneca share disappointing Phase 3 data for eplontersen

Written by Isaac FrancisPublished Jul 9, 2026, 7:57 AM

The CARDIO-TTRansform trial did not reach its primary endpoint for treating transthyretin-mediated amyloid cardiomyopathy.
Adding eplontersen to the modern standard of care yielded no statistically significant benefit over placebo.
Ionis highlights near- and long-term value creation driven by its wholly owned pipeline and ongoing independent launches.

Ionis Pharmaceuticals (NASDAQ:IONS) and its development partner AstraZeneca (NYSE:AZN) announced today that their Phase 3 CARDIO-TTRansform clinical trial evaluating eplontersen did not meet its primary efficacy endpoint.

The extensive, late-stage study focused on a contemporary population of patients with transthyretin-mediated amyloid cardiomyopathy (ATTR-CM).

The trial failed to demonstrate a statistically significant benefit over a placebo regarding the composite outcome of cardiovascular mortality and recurrent cardiovascular clinical events up to Week 140.

"Although we are disappointed that the study did not meet the primary endpoint, these results have the potential to guide the treatment landscape for ATTR-CM and contribute to advancing future care for patients," stated Ionis Chief Executive Officer Brett P. Monia, Ph.D.

Despite the setback in the overall population, a prespecified subgroup analysis of patients treated with eplontersen monotherapy—those not on baseline stabilizers—showed a nominally significant hazard ratio of 0.71 on the composite endpoint.

The clinical data from the trial will be analyzed continuously by both development partners, with comprehensive final metrics slated to be shared publicly with the global scientific community during the European Society of Cardiology (ESC) Congress in August 2026.

Ionis emphasized that its broader corporate and financial trajectory remains healthy, backed by active commercial launches like TRYNGOLZA and a robust wholly owned drug pipeline on track to achieve cash flow breakeven by 2028.

Ionis and AstraZeneca share disappointing Phase 3 data for eplontersen

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