AstraZeneca and Ionis' heart disease drug Wainua fails pivotal trial, shares plunge

AstraZeneca and Ionis Pharmaceuticals' heart drug Wainua failed its Phase 3 CARDIO-TTRansform trial, failing to reduce cardiovascular deaths and events in 1,432 patients with ATTR cardiomyopathy. The failure, attributed to trial design flaws where up to 81% of patients took background stabilizer therapies, sent AstraZeneca shares down 9% and Ionis down 21% on July 9, 2026. Conversely, shares of rivals Alnylam and BridgeBio surged as Alnylam's Amvuttra secures a near-monopoly in the multi-billion dollar silencer market.

Wainua ATTR cardiomyopathy trial failure

• ▪Wainua demonstrated a nominally significant benefit over placebo in a prespecified subgroup of patients who received the drug as a standalone monotherapy without stabilizer drugs
• ▪The CARDIO-TTRansform trial evaluated Wainua in 1,432 patients across 20 countries
• ▪The CARDIO-TTRansform trial of Wainua did not show a statistically significant reduction in cardiovascular deaths and recurrent cardiovascular events over 140 weeks compared to placebo
• ▪AstraZeneca and Ionis Pharmaceuticals' drug Wainua failed to meet its primary endpoint in the Phase 3 CARDIO-TTRansform trial for transthyretin-mediated amyloid cardiomyopathy

AstraZeneca management credibility concerns

• ▪Jefferies analysts noted that the trial failure could cause a credibility loss for AstraZeneca management, who had expressed strong confidence in the trial's success
• ▪The trial failure represents a setback for AstraZeneca following a U.S. regulatory panel's rejection of its breast cancer drug camizestrant in May 2026 on trial design grounds

Share price decline across companies

• ▪Ionis Pharmaceuticals' shares fell between 12% and 21% following the announcement of the Wainua trial failure on July 9, 2026
• ▪AstraZeneca's London-listed shares fell as much as 9% on July 9, 2026, wiping out £23.3 billion in market value at the day's low
• ▪Shares of competitor Alnylam Pharmaceuticals rose approximately 10% to 15%, while BridgeBio shares climbed 6% to 16% on July 9, 2026

ATTR cardiomyopathy competitive landscape

• ▪Wainua's failure leaves Alnylam Pharmaceuticals' Amvuttra as the only approved silencer drug in the transthyretin-mediated amyloid cardiomyopathy market
• ▪Transthyretin-mediated amyloid cardiomyopathy is a progressive, life-threatening heart condition estimated to affect between 300,000 and 500,000 people globally
• ▪Wainua generated $212 million in product revenue in 2025 and remains approved in over 20 countries to treat polyneuropathy in adults with hereditary transthyretin-mediated amyloidosis

Stabilizer baseline trial design flaws

• ▪In the CARDIO-TTRansform trial, 57% of patients were taking a stabilizer drug at baseline, and an additional 24% initiated stabilizer therapy during the study
• ▪Analysts criticized the trial design because the high proportion of patients taking background stabilizer therapies masked the potential additive benefit of Wainua