AstraZeneca's Wainua, a nerve disease drug developed in partnership with Ionis Pharmaceuticals, failed to meet the primary endpoint of a late-stage trial in transthyretin-mediated amyloid cardiomyopathy.

The failure sent AstraZeneca shares down nearly 10% while also raising questions about the company's clinical trial design capabilities. In the trial, the drug did not demonstrate a statistically significant reduction in cardiovascular deaths and recurring heart problems when added to standard care in the 140-week trial, which enrolled 1,432 patients.¹

What went wrong?

Analysts pointed quickly to trial design as a central issue. In the study, 57% of patients were already taking a stabilizer, drugs such as Pfizer's Vyndaqel that work by stabilizing the faulty proteins that accumulate in the heart, and a further 24% added a stabilizer during the study period. Wainua, like Alnylam's Amvuttra, works by reducing production of those proteins rather than stabilizing them, making the co-administration of the two drug classes difficult to disentangle in assessing Wainua's benefit.

AstraZeneca noted that taking Wainua as a standalone therapy without stabilizers showed "nominally significant" benefit, but the primary endpoint, which included patients on combination therapy, was not met.²

Jefferies analysts are calling the design flaw a potential credibility problem for management, which had previously expressed strong confidence in the trial's prospects ahead of the readout. "AstraZeneca is meant to be able to have exceptionally good trial design ability," Jefferies said, though the firm added that the miss should not derail the company's long-term revenue targets.¹

BofA analyst Sachin Jain says the result came as a surprise. "Data comes as a surprise given we and investors hadn't even debated likelihood of a primary endpoint miss, given positive precedent data and successful launch for competitor Amvuttra," Jain said.

What was the market’s reaction?

After sharing trial results, AstraZeneca shares fell nearly 10%, their lowest level since November 2024, finishing the session down 7.7% marking the largest single-day percentage decline since that month and the biggest loss on the FTSE 100.¹ At the day's low, the company had shed approximately 31.21 billion in market value.¹

AstraZeneca wasn’t the only one to see shares slide, as Ionis shares fell nearly 21% on the news, while competitors with approved drugs in the ATTR-CM space benefited, with Alnylam Pharmaceuticals and BridgeBio rising between 6% and 16%.¹

Lucy Coutts, investment director at AstraZeneca shareholder JM Finn, framed the selloff in terms of investor expectations rather than the drug's financial materiality. "While the news is relatively small to AstraZeneca's valuation, the effect is much greater on the company's own gold standard of design trials success," Coutts said. "In simple terms, investors expect AstraZeneca to succeed, and this is why the share price has taken such a hit and future expectations may be tempered."

Sources

1. AstraZeneca's Wainua fails key heart disease trial, shares tumble Reuters July 9, 2026 https://www.reuters.com/business/healthcare-pharmaceuticals/astrazeneca-ionis-drug-fails-meet-main-goal-late-stage-heart-disease-trial-2026-07-09/
2. Update on CARDIO-TTRansform Phase III trial for Wainua (eplontersen) in adults with transthyretin-mediated amyloid cardiomyopathy AstraZeneca July 9, 2026 https://www.astrazeneca.com/media-centre/press-releases/2026/update-cardio-ttransform-phase-iii-trial.html