AstraZeneca shares plunge as Wainua fails late-stage heart disease trial

AstraZeneca shares slumped nearly 10% on Thursday after the drugmaker said its nerve disease treatment Wainua failed to achieve the primary objective in a late-stage clinical trial for a serious heart condition, dealing a setback to one of its most closely watched pipeline assets.

The stock fell about 9.5% in London trading, making it the biggest loser on the FTSE 100 index.

The Anglo-Swedish pharmaceutical company said Wainua, developed in partnership with US-based Ionis Pharmaceuticals, did not significantly reduce cardiovascular deaths and recurrent heart-related events in patients suffering from transthyretin-mediated amyloid cardiomyopathy (ATTR-CM).

The disease is caused by the build-up of abnormal proteins in the heart, impairing its ability to pump blood and potentially leading to heart failure.

The disappointing outcome is a blow to AstraZeneca's ambitions of expanding beyond its core oncology business as it works toward its goal of generating $80 billion in annual revenue by 2030 through the launch of up to 20 new medicines.

Analysts had viewed the trial as a crucial opportunity to establish Wainua in the underpenetrated ATTR treatment market.

They believed Wainua could generate multi-billion-dollar peak sales for the company.

Existing approvals remain intact

In the phase-three CARDIO-TTRansform study, Wainua was tested against placebo in 1,432 patients over a period of 140 weeks.

The company said adding Wainua to standard treatment failed to provide a statistically significant benefit in the overall patient population.

However, subgroup analysis showed mixed results.

Among patients already receiving stabilizer therapy at the start of the trial, who accounted for 57% of participants, Wainua showed no measurable benefit.

A separate subgroup receiving Wainua as a standalone treatment without stabilizers demonstrated a "nominally significant" benefit.

"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," said Sharon Barr, executive vice president of AstraZeneca's biopharmaceuticals R&D.

Wainua remains approved in more than 20 countries for treating polyneuropathy, a rare neurological disorder that causes progressive nerve damage.

The drug generated $212 million in revenue for AstraZeneca during 2025.

Investors turn cautious on the remaining pipeline

The failed trial has prompted investors to reassess the company's near-term pipeline prospects.

Citi, which maintains a Buy rating on AstraZeneca, had previously projected peak Wainua sales of around $6.2 billion in ATTR-CM, assigning the programme a 59% probability of success.

The bank had estimated in May that failure of the CARDIO-TTRansform trial would reduce its discounted cash flow valuation by around 2.8%, or roughly £5.20 per share from its £181 fair value estimate.

At the time, Citi argued that the roughly 10% decline in AstraZeneca's stock from its earlier highs had already more than reflected the combined downside risk associated with three key clinical trial readouts.

The brokerage estimated a bear-case valuation of £168 per share even if all three major trials failed, still substantially above where the stock had been trading then.

The bullish scenario, assuming success across all three programmes, implied a valuation of about £204 per share.

Thursday's sharp sell-off suggests investors are attaching greater risk to AstraZeneca's remaining late-stage pipeline, with attention now turning to the company's upcoming SERENA-4 and AVANZAR trial results later this year, which are expected to play a significant role in shaping sentiment toward the drugmaker's long-term growth strategy.