Shares in AstraZeneca dropped by 9% today after the big pharma company announced that its Wainua treatment did not meet the primary goal in a phase III study.

AstraZeneca said its Phase III Cardio-TTRansform trial of Wainua (eplontersen), developed with Ionis Pharmaceuticals, failed to meet its primary endpoint in patients with transthyretin-mediated amyloid cardiomyopathy (ATTR-CM), sending its shares down around 9% and wiping about £20bn off its market value.

This is one of AstraZeneca's largest one-day declines in recent months. Despite today's fall, the shares remain above their 52-week low and are still up over the past year. A top 10 FTSE company, its market value is still about £200–223bn.

The study found that adding Wainua to current standard of care did not significantly reduce the combined risk of cardiovascular death and recurrent cardiovascular events compared with placebo over 140 weeks, although the treatment was generally well tolerated and had a safety profile consistent with previous studies.

The trial enrolled patients receiving existing therapies, with 57% already taking a transthyretin stabiliser at baseline and a further 24% starting one during the study. AstraZeneca said a pre-specified subgroup analysis suggested Wainua monotherapy reduced the number of primary events compared with placebo, although the result was only nominally significant, while no treatment benefit was seen in patients already receiving stabiliser therapy.

Sharon Barr, executive vice president, BioPharmaceuticals R&D, said: “The CARDIO-TTRansform trial was designed to examine the role of Wainua, a gene silencer treatment, on top of today’s standard of care in reducing recurring cardiovascular events and mortality. 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.”

The companies said they would analyse the full dataset before presenting the findings at the European Society of Cardiology Congress in August.

The setback disappointed investors because Wainua had been viewed as a potential growth driver in the expanding ATTR-CM market, prompting one of AstraZeneca's steepest one-day share price falls in recent months.

Dan Coatsworth, head of markets at AJ Bell, said investors had been "shocked by AstraZeneca's drug trial flop", adding that the failure would raise questions over the company's ambition to reach $80bn in annual sales by 2030. “It’s not unusual to see phase III trials fail, but AstraZeneca has had far more hits than misses so far this year. It’s a giant in the drugs industry and that creates high expectations for success."

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