AstraZeneca shares slumped after the British-Swedish drugmaker announced a late-stage trial failure, denting the commercial prospects for its gene silencing drug. Analysts were seeing an overreaction.

AstraZeneca said Thursday that Wainua, a gene silencer administered as a monthly injection, "did not provide a statistically significant benefit" to survival rates in patients with transthyretin amyloid cardiomyopathy, a progressive, deadly heart disease.

Although Wainua was generally well tolerated, it failed to show an improvement versus a placebo when added to standard care in a Phase 3 trial, AstraZeneca said.

The drugmaker's U.S.-listed shares sank 7.7% in premarket trading, wiping out roughly $25 billion in market capitalization. The stock fell even further in London.

Wainua is developed and commercialized alongside Ionis Pharmaceuticals, a California-based biotech. Shares of the smaller company cratered 19%.

Bernstein analysts described the results as unexpected, saying they had spoken to the company, which was extremely surprised and disappointed by the data. "We are too," the analysts added.

The firm noted that AstraZeneca had doubled its trial size to 1,400 patients to increase the chances of positive, statistically rigorous results -- an outcome that didn't come to fruition.

The results don't make Wainua a total commercial failure. The drug is already approved for a different form of transthyretin amyloidosis affecting the nervous system. The drug generated $212 million in product revenue for AstraZeneca last year and earned Ionis around $49 million in royalties.

However, the trial miss casts doubt on its approval for the cardiomyopathy indication, which would have dramatically expanded the addressable patient population.

Transthyretin amyloid cardiomyopathy is significantly more prevalent than transthyretin amyloid polyneuropathy. In the U.S., the estimated prevalence in 2022 was 41.1 cases per million people, compared to just 15.1 cases per million.

The trial failure also limit the drugmakers' ability to compete with approved treatments from Pfizer, BridgeBio Pharma, and Alnylam Pharmaceuticals. Shares of the rival pharma companies were up 0.3%, 11%, and 18%, respectively, in Thursday's premarket session.

Jefferies analysts urged investors to "wait it out" as AstraZeneca stock slid Thursday. "This was meant to be a slam dunk, making the outright failure surprising," the firm wrote in a research note.

However, the analysts asserted that pulling Wainua's new indication from their model "has limited impacts," reflecting AstraZeneca's "therapeutic positioning and the robustness of the growth trajectory." The same could be said for consensus views, the firm added.

Critically, Jefferies doesn't expect the trial failure to impact the company's path to deliver $80 billion in revenue in 2030 and only shaves 30 basis points off the five-year earnings-per-share compound annual growth rate.

The stock reaction "seems an over-reaction," the analysts concluded. In their view, AstraZeneca remains "the premium growth company into the end of the decade and beyond." They recommended buying the dip.

Write to Mackenzie Tatananni at mackenzie.tatananni@barrons.com

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July 09, 2026 08:45 ET (12:45 GMT)

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