Ionis and AstraZeneca Hit by Phase 3 Trial Failure for Eplontersen

Key Facts

1Ionis and AstraZeneca announced that the CARDIO-TTRansform Phase 3 trial for eplontersen did not meet its primary efficacy endpoint.

2The trial failed to meet the composite outcome of cardiovascular mortality and recurrent CV clinical events compared to placebo up to Week 140.

In a development highlighting the high risks of biotech innovation, Ionis Pharmaceuticals and AstraZeneca announced that their Phase 3 CARDIO-TTRansform trial for eplontersen failed to meet its primary efficacy endpoint. The trial did not demonstrate a statistically significant reduction in the composite outcome of cardiovascular mortality and recurrent clinical events compared to a placebo through Week 140. This failure represents a major setback for the drug's development as a treatment for ATTR-CM, a progressive and fatal heart disease.

This clinical disappointment occurs amid a competitive landscape dominated by Pfizer’s Vyndaqel, which remains a standard of care in the ATTR-CM market. Per market data, AstraZeneca (AZN) shares closed at $189.28 on July 8, 2026. Industry experts note that the failure of eplontersen to differentiate itself in a contemporary patient population may lead to downward revisions of long-term revenue forecasts for Ionis, which has heavily marketed its RNA-targeted platform to investors.

Traders are closely watching Ionis (IONS) price action after the stock closed at $86.33 on July 7, 2026, with potential support levels being tested following the news. With no major pharmaceutical regulatory catalysts listed in the immediate seven-day calendar, market attention will shift to upcoming management commentary regarding the future of the eplontersen program and any potential impact on the broader partnership between the two firms.