AstraZeneca and Ionis's Wainua Fails Pivotal Phase 3 CARDIO-TTRansform Heart Disease Trial

AstraZeneca and Ionis's Wainua Fails Pivotal Phase 3 CARDIO-TTRansform Heart Disease Trial

On July 9, 2026, AstraZeneca and Ionis Pharmaceuticals announced a major clinical setback as their once-monthly subcutaneous RNA-targeted silencer, Wainua (eplontersen), failed to meet its primary objective in the Phase 3 CARDIO-TTRansform trial for adults with transthyretin-mediated amyloid cardiomyopathy (ATTR-CM).

The trial did not achieve statistical significance on its primary composite endpoint of cardiovascular (CV) mortality and recurrent CV clinical events up to 140 weeks compared to placebo.¹

Trial Design and Baseline Confounders

CARDIO-TTRansform is the largest ATTR-CM trial conducted to date, randomizing 1,432 participants across 20 countries. However, the contemporary standard of care introduced significant confounding stabilizer therapies (primarily Pfizer's Vyndaqel/Vyndamax, or tafamidis):

• At baseline, 57% of patients in each arm were already receiving a TTR stabilizer treatment.
• An additional 24% of patients in each arm initiated stabilizer therapy during the course of the 140-week trial, meaning over 80% of patients experienced dual-mechanism therapy.
• Key Findings:
  • "In patients who were on stabiliser therapy at baseline, no treatment effect was observed."
  • In a prespecified subgroup analysis of Wainua monotherapy compared to placebo, fewer primary composite events were observed, and this benefit was nominally significant.
  • Wainua was generally well-tolerated, with a safety profile consistent with its approved indication in ATTR polyneuropathy (hATTR-PN).

Market and Competitive Implications

This unexpected late-stage clinical failure keeps AstraZeneca and Ionis out of a massive and rapidly growing ATTR cardiomyopathy market, which is currently dominated by Pfizer’s Vyndaqel/Vyndamax. The results also present a massive competitive boost for:

• Alnylam Pharmaceuticals, whose rival RNA-silencing therapy Amvuttra (vutrisiran) recently succeeded in the HELIOS-B trial in ATTR-CM.
• BridgeBio Pharma, whose oral TTR stabilizer acoramidis is currently awaiting regulatory approval.

AstraZeneca and Ionis plan to present the full dataset and subgroup analyses at the European Society of Cardiology (ESC) Congress in late August 2026.