The US Food and Drug Administration (FDA) has approved AstraZeneca and MedImmune’s immunotherapy Imfinzi (durvalumab) to treat patients with a certain form of lung cancer.

Imfinzi, a human monoclonal antibody that binds to PD-L1, was previously approved in the US in May 2017 for treating patients with urothelial cancer.

Based on positive results from the Phase 3 Pacific trial, the drug can now treat unresectable stage III non-small cell lung cancer (NSCLC) in patients whose disease has not progressed following platinum-based chemotherapy and radiation therapy, which has been the only approved treatment available in the US until now.

The Pacific trial showed an improvement in median progression-free survival (PFS) of 11.2 months in patients taking Imfinzi versus a placebo, representing a 48% reduction in the risk of disease progression or death.

Lung cancer is the leading cause of cancer death in the US, with an estimated 222,500 new diagnoses and 155,870 deaths in 2017, according to the National Cancer Institute.  NSCLC is the most common type of lung cancer, and stage III means tumors have spread to nearby lymph nodes or other parts of the body.

“Given that up to 89% of patients will progress to metastatic disease, it is important that there is now a new option that can give patients more time without disease progression,” said Scott Antonia, chair of the thoracic oncology department at the H. Lee Moffitt Cancer Center and Research Institute in Tampa, and investigator in the Pacific trial.

According to Leerink Partners analyst Seamus Fernandez, Imfinzi could bring in peak sales of $3.8 billion for AstraZeneca. The lung cancer indication alone could hit $1 billion in sales worldwide, Fernandez predicts, citing a survey of 51 oncologists who have suggested a broad uptake of the drug in those patients who cannot be treated with surgery.

AstraZeneca also filed for approval in Europe last October for the same indication.