CARDIO-TTRansform: No Significant Difference With Eplontersen vs Placebo in ATTR-CM

A once-monthly transthyretin gene silencer developed by Ionis Pharmaceuticals and AstraZeneca failed to demonstrate a significant reduction in cardiovascular death and recurrent cardiovascular events compared to placebo. The trial enrolled participants across 130 centers in 20 countries, evaluating patients with wild-type or hereditary ATTR-CM who received either 45 mg of eplontersen or a placebo via subcutaneous injection every four weeks.

Despite large and sustained reductions in circulating serum transthyretin, the overall study population experienced a total of 381 primary endpoint events among the 210 patients receiving eplontersen, compared with 392 events among the 231 patients receiving placebo, according to clinical data released by the companies. Researchers noted that the trial population was heavily treated with standard of care, with 57% of participants receiving stabilizer therapy at baseline and an additional 24% initiating a stabilizer during the course of the study.

Subgroup Analysis Points to Baseline Stabilizer Impact

While the overall trial did not achieve statistical significance for its primary efficacy endpoint, a prespecified subgroup analysis revealed a differing outcome among patients who were not taking stabilizer therapy when the study began. In that specific cohort, a nominally significant hazard ratio of 0.71 was observed for the composite outcome of cardiovascular mortality and recurrent events.

“Primary results appeared to be influenced by baseline stabiliser use with no clear benefit in patients receiving background stabiliser therapy, while fewer primary endpoint events occurred with eplontersen in patients not receiving a stabiliser.”

Maurer, who serves as the Arnold and Arlene Goldstein professor of cardiology at Columbia University Irving Medical Center, presented the findings at the European Society of Cardiology Congress. He noted that multiple secondary, imaging, and biomarker analyses across the broader study population favored eplontersen over placebo, even though background stabilizer therapy appeared to influence the primary outcome.

Shifting Treatment Landscape in ATTR-CM Care

Industry executives and clinical investigators emphasized that the trial results underscore how rapidly patient care has evolved over the past decade. With growing disease awareness and earlier diagnoses, contemporary patients diagnosed with transthyretin amyloidosis with cardiomyopathy are routinely treated with established stabilizers prior to or alongside newer therapies.

ATTR-CM is a progressive and fatal systemic condition driven by misfolded transthyretin protein fibers building up inside cardiac tissue. The disease affects an estimated 300,000 to 500,000 people worldwide, causing heart failure symptoms such as fatigue, shortness of breath, and swelling. Investigators note that while gene silencers successfully lower protein production, evaluating their additive benefit in a patient population already receiving background stabilizers remains a complex clinical question.

Next Steps and Pipeline Focus for Ionis and AstraZeneca

Following the trial outcome, Ionis and AstraZeneca plan to continue analyzing the full dataset from the CARDIO-TTRansform study. Researchers point out that the trial represents the largest enrolled study of a contemporary ATTR-CM patient population, providing a benchmark for future clinical trial designs in amyloidosis research.

For Ionis, the trial outcome arrives alongside independent commercial launches, including TRYNGOLZA, as the company works toward its financial target of achieving cash flow breakeven by 2028. Meanwhile, medical researchers emphasize that fully understanding how gene silencers interact with established stabilizer regimens will require ongoing evaluation as treatment protocols continue to adapt.