US regulators have widened the scope of Merck & Co’s immunotherapy Keytruda to include the treatment of certain patients with lung cancer.

The US and Drug Administration says the drug can now be used to treat patients with non-small cell lung cancer whose disease has progressed despite prior therapy and, crucially, whose tumours express the protein PD-1.

As such, Keytruda (pembrolizumab) has been cleared under the FDA’s accelerated approvals process for use with a companion diagnostic - the PD-L1 IHC 22C3 pharmDx test - to determine which NSCLC patients are eligible for treatment.  

The decision follows clinical data showing that Keytruda shrank tumours in 41% of pre-treated patients with advanced disease and PD-L1 positive tumours, and that this effect lasted between 2.1 and 9.1 months, the regulator said.     

Keytruda became the first US-approved PD-1 inhibitor last year when it received the nod for advanced melanoma, and is now also the first and only anti-PD-1 therapy approved for both squamous and non-squamous metastatic NSCLC.

Bristol-Myers Squibb’s rival PD-1 checkpoint inhibitor Opdivo (nivolumab) was cleared for squamous non-small cell lung cancer unresponsive to chemotherapy in the the US earlier this year.

The drugs work by blocking the Programmed Death receptor on tumour cells, thus impeding their ability to escape detection and destruction cytotoxic T-cells.