Key clinical trial results for a new AstraZeneca heart drug have disappointed, sending the company's stock sharply lower.

The British pharmaceutical giant announced that its investigational drug, Wainua, did not achieve its primary goal in a Phase III trial for a rare heart condition.

The drug failed to demonstrate a statistically significant reduction in the risk of death and recurrent cardiovascular events compared to a placebo over a 140-week study period.

Wainua is being developed to treat transthyretin amyloid cardiomyopathy, a rare and life-threatening disease where misfolded proteins build up in heart tissue.

An analyst noted that while this trial setback is a disappointment, it does not derail AstraZeneca PLC's broader long-term sales target. However, the company had previously held high expectations for the drug's performance on this primary endpoint.

The trial focused on a specific subtype of the disease, which is estimated to affect around 500,000 patients globally.

In London trading, shares of AstraZeneca PLC fell as much as 8.9%, on track for their worst single-day performance in over six years.