AstraZeneca has announced that Imfinzi (durvalumab), combined with tremelimumab, failed to achieve its primary endpoint in the Phase III NEPTUNE trial of patients with previously-untreated Stage IV non-small cell lung cancer (NSCLC).

Imfinzi and tremelimumab did not improve overall survival (OS), the primary endpoint, in the primary analysis population of patients with a blood tumour mutational burden (TMB) of at least 20 mutations per megabase, compared to standard of care platinum-based chemotherapy.

TMB is a measurement of the number of mutations in the genome of a tumour; usually higher levels of TMB make the tumour more visible to the immune system.

AstraZeneca executive vice-president of oncology research and development José Baselga said: “We are fully committed to a deep analysis of the vast clinical and biomarker data from this trial to gain further insights to improve immuno-oncology approaches for patients with metastatic non-small cell lung cancer.”

Full results from the NEPTUNE study will be presented at an upcoming medical meeting.

Imfinzi is a human monoclonal antibody (mAb) that binds to Programmed death-ligand 1 (PD-L1), blocking the interaction of PD-L1 with Programmed cell death protein 1 and CD80 and countering the tumour’s evasion of the immune system.

Tremelimumab is also a human mAb that inhibits cytotoxic T-lymphocyte-associated protein 4 and contributes to T cell activation, thus boosting immune response to tumours.

Imfinzi is already approved in 49 countries for Stage III NSCLC based on the Phase III PACIFIC trial. It is also currently being studied as a monotherapy and in combination with chemotherapy with or without tremelimumab for Stage IV NSCLC in other Phase III trials.

As a monotherapy, Imfinzi is also being studied for a range of other oncology indications, including small cell lung cancer; it recevied orphan status for this indication from the US Food and Drug Administration in July this year based on the results of the Phase III CASPIAN trial.