Imfinzi by AstraZeneca (AZN.US) has been granted priority review by the FDA for use in patients with small cell lung cancer in the US

British drug giant AstraZeneca (AZN.US) said on Thursday that its blockbuster cancer drug Imfinzi has been granted "FDA breakthrough designation" by the US regulator FDA for use in a group of patients with advanced small cell lung cancer who have not responded to platinum-based chemotherapy.

AstraZeneca, a crucial part of the UK's economy, said it expects the FDA's regulatory decision to be finalised in the fourth quarter of 2024.

The company's important application to the FDA was mainly based on positive late-stage trial data showing the drug improved overall survival and progression-free survival in patients with the cancer who had not responded to platinum-based chemotherapy.

AstraZeneca's drug research team also said Imfinzi had recently been granted "breakthrough therapy designation" by the FDA in the same background, which would help speed up the FDA's regulatory review process.

Small cell lung cancer is a highly aggressive type of cancer. Imfinzi is a human monoclonal antibody that works by blocking the ability of tumours to evade the immune system and by inhibiting the immune system's overactive response, while enhancing the body's immune response to cancer, providing an important alternative to chemotherapy.

AstraZeneca's mechanism of action for Imfinzi makes it more effective than traditional chemotherapy in treating certain types of cancer, as Imfinzi is an immune checkpoint inhibitor that targets the PD-L1 protein. This targeted therapy can more precisely inhibit the immune escape mechanisms of tumour cells without the widespread damage to rapidly dividing cells (including healthy cells) that chemotherapy causes.

Chemotherapy works by killing rapidly dividing cells, but this mechanism also affects healthy cells, leading to a range of side effects such as hair loss, fatigue and increased risk of infection. In contrast, Imfinzi's immunotherapy is more targeted and AstraZeneca's trials have shown few side effects.