AstraZeneca has struck a $1bn (£773m) deal to buy a Belgian biotech company that specialises in cancer immunotherapies, the latest in a string of acquisitions that also yielded positive results for a late-stage rare disease drug on Monday.

EsoBiotec, a small privately held firm founded four years ago in Mont-Saint-Guibert, develops in-vivo cell therapies that empower the immune system to attack cancers, and could offer many more patients access to cell therapy treatments provided in minutes rather than weeks.

The deal marks the latest acquisition by Astra, which is Britain’s biggest listed company valued at £186bn, as the pharmaceutical group continues to expand its global operations.

EsoBiotec’s treatment uses highly targeted lentiviruses to deliver genetic instructions to specific immune cells, such as T-cells, which program them to recognise and destroy tumour cells for cancer treatment, or tackle autoreactive cells (that target the body’s own tissues or cells) for potential use in autoimmune diseases. This means cell therapies can be administered through a simple injection, and EsoBiotec describes them as “cost-effective, off-the-shelf therapies”.

In traditional cell therapies, cells are taken from a patient, genetically modified outside the body, and then put back into the patient as a medicine after immune cell depletion, which usually takes weeks.

Susan Galbraith, the executive vice-president of oncology research and development at AstraZeneca, said: “We believe it has the potential to transform cell therapy and will enable us to scale these innovative treatments so that many more patients around the world can access them.

“EsoBiotec will accelerate and expand the impact of our recent investments and marks a major step forward in realising our ambition to harness the full potential of cell therapy.”

EsoBiotec recently launched a clinical trial for multiple myeloma, a type of bone marrow cancer.

AstraZeneca, which fended off a hostile £69bn takeover approach from the US group Pfizer in 2014, will pay $425m initially for the Belgian company, and up to $575m based on development and regulatory milestones. It has been beefing up its drug portfolio with targeted acquisitions, such as China’s Gracell Biotechnologies, which specialises in cancer therapy known as CAR-T that modifies a patient’s cells to fight the disease.

AstraZeneca’s biggest deal was the $39bn acquisition of the US rare disease drug developer Alexion in 2020, but it was criticised for paying a high price. Marc Dunoyer, who runs the division and is AstraZeneca’s chief strategy officer, defended the deal as a “fantastic acquisition” last month when the company took a $753m hit for scrapping one of the Alexion drugs, while two other products from the acquisition have also been abandoned.

Separately, Britain’s biggest pharmaceutical group said on Monday that its Imfinzi treatment had been approved in the EU as the first and only immunotherapy for patients with limited-stage small cell lung cancer, whose disease has not progressed after platinum-based chemoradiation therapy.

AstraZeneca also announced that a drug for a rare endocrine disease, hypoparathyroidism, which can lead to bone density loss and osteoporosis, had met its goal of normalising calcium levels in the blood after 24 weeks. It was well tolerated by patients, and the trial continues as planned to 52 weeks. The company acquired the medicine along with the French rare disease specialist Amolyt Pharma in a deal worth more than $1bn a year ago.

AstraZeneca also announced a licence agreement with South Korea’s Alteogen to acquire the worldwide rights to its platform, to develop and commercialise subcutaneous formulations of several oncology medicines.

Injecting medicines into the fatty tissue just under the skin can offer many advantages, including time savings for patients, clinical staff and health systems.

AstraZeneca’s share price reaction was muted, dipping by 0.3%.