AstraZeneca has seen around £20 billion wiped from its market value following the disappointing late-stage trial results for Wainua, pushing its market capitalisation below £200 billion.
AstraZeneca was the biggest faller on the FTSE 100 after a late-stage trial of Wainua failed to meet its primary objective.
Shares in the UK pharmaceutical group fell nearly 10% at one stage and were down 9.2%, weighing heavily on the wider index. The FTSE 100 dropped around 52 points, or 0.5%, to 10,435.
Despite the sharp fall, AstraZeneca remains the second-largest company in the FTSE 100 by market value, behind HSBC at approximately £248 billion and ahead of energy giant Shell, valued at around £169 billion.
Wainua, developed in partnership with California-based biotechnology company Ionis, is a gene-silencing treatment for transthyretin amyloidosis.
AstraZeneca said the phase three CARDIO-TTRansform trial failed to show a statistically significant benefit in reducing the combined outcome of cardiovascular mortality and recurrent cardiovascular events.
Sharon Barr, executive vice president of biopharmaceuticals research at AstraZeneca, said the study had been designed to assess whether Wainua, when added to current standard-of-care treatment, could reduce recurring cardiovascular events and mortality.
Although the trial missed its primary endpoint, Barr said the findings could still contribute to scientific understanding of treatment approaches for patients suffering from the progressive and potentially fatal condition.
AstraZeneca and Ionis will now analyse the full data set to better understand the results.
The findings are expected to be presented to the scientific community at the European Society of Cardiology Congress in August.
