Shares in AstraZeneca and Ionis decline on heart drug trial failure

AstraZeneca's stock fell about 8% in London.

Shares in AstraZeneca and Ionis Pharmaceuticals slid on Thursday after the companies announced that a heart disease drug they had been developing together failed a late-stage trial.

Swedish-British pharmaceutical giant AstraZeneca (UK:AZN) announced in a statement on Thursday that the Wainua medicine, a gene silencer to be administered once a month via syringe, "did not provide a statistically significant benefit" in deaths related to cardiovascular health.

The Cambridge, England-headquartered company's stock declined close to 8% on London's stock exchange and was the top laggard in the U.K.'s flagship FTSE 100 index UK:UKX. Its shares $(AZN)$ are down 8% in premarket trading in New York.

The decline equates to an approximately GBP20 billion ($27 billion) decline in its market value.

Shares in Ionis $(IONS)$, a Carlsbud, California-based company, tumbled more than 17% in premarket trading in New York.

"Although the trial did not meet its primary objective, we believe the results support greater scientific understanding of treatment approaches for the hundreds of thousands of patients worldwide suffering from this progressive and often fatal condition," Sharon Barr, executive vice president for biopharmaceutical research and development at AstraZeneca, said in a statement.

"AstraZeneca's latest update was more bitter than sweet as it said the drugs don't work," Dan Coatsworth, head of markets at AJ Bell, wrote in a note on Thursday. "It meant the U.K. market was the only major European index to be in the red."

The drug was intended to treat patients with transthyretin-mediated amyloid cardiomyopathy, a cardiovascular disease that results from proteins building up in the heart, and affects between 300,000 and 500,000 people globally, according to Ionis's estimates.

Analysts at Jefferies, led by Michael Leuchten, wrote in a note on Thursday that the real risk from the failed trial for AstraZeneca is "probably a degree of credibility loss," adding that management had been highly confident in the drug's ability.

-Nora Redmond

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July 09, 2026 05:53 ET (09:53 GMT)

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