Early trials of an AstraZeneca cancer drug have indicated the potential for “combination therapies” to widen the range of patients who can benefit from new breakthroughs in oncology.

These findings emerged from a study of durvalumab, AstraZeneca’s leading contender in the hotly-contested field of “cancer immunotherapies” — treatments that work by turning the body’s immune system against tumours.

Immunotherapies have been heralded as the biggest advance against cancer for decades — but only a relatively small proportion of patients have so far been shown to benefit from them.

Data from the AstraZeneca study published over the weekend will raise hopes that immunotherapies can be made more widely effective by combining them with one or more other complementary cancer drugs.

According to the study, combining durvalumab with another AstraZeneca drug called tremelimumab showed potential against so-called PD-L1 negative tumours, which have so far proved largely resistant to immunotherapies.

First generation of immunotherapies from Merck and Bristol-Myers Squibb have targeted PD-L1 positive tumours but only between a quarter and a third of cancer patients are diagnose with that kind. This has left a much bigger potential market for AstraZeneca, Roche and other companies seeking to develop combination therapies for patients with PD-L1 negative cancer.

Data from the study of durvalumab and tremelimumab showed a similar level of response between patients with PD-L1 positive and negative tumours — 22 and 29 per cent respectively. This compares with a response rate of 5 per cent among PD-L1 negative patients treated with durvalumab alone.

“The results suggest that this combination has potential as a treatment option for patients with PD-L1 negative tumours whose needs are not addressed by currently available therapies,” said Scott Antonia of the Moffitt Cancer Center in Florida, which was involved in the trial.

This latest study, published in The Lancet Oncology, adds detail to initial findings revealed last November. It involved 26 patients taking doses of durvalumab and tremelimumab who were chosen by AstraZeneca for a larger late-stage trial which will determine whether the product reaches market.

However, the small number of patients and the fact that a majority of them still failed to respond shows that there is still a long way to go before immunotherapies become the “wonder drugs” that some experts believe will make cancer a manageable condition akin to HIV.

Pascal Soriot, AstraZeneca chief executive, has put cancer immunotherapy at the centre of efforts to revive the company as older drugs lose patent protection. He has said that, while Merck and BMS are ahead in a market estimated to be worth $35bn a year within a decade, AstraZeneca’s focus on combination therapies would prove an advantage in the long run.

“The competition is all happening in the PD-L1 positive box, which is only a quarter of the market,” he said last week. “The other box is still very open.”

AstraZeneca recently scrapped plans to seek regulatory approval for durvalumab on its own, in favour of focusing on the combination with tremelimumab. “We were always behind in monotherapies,” said Mr Soriot. “Combinations was always our commercial focus.”

AstraZeneca has forecast peak annual sales of $6.5bn for durvalumab, making it an important part of Mr Soriot’s goal to increase group revenues by three-quarters to $45bn by 2023. The drug is part of new class of drugs called “checkpoint inhibitors” which aim to bypass the blockades used by cancer cells to avoid detection by the immune system.

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