Shares in Innate Pharma plunged near 50 percent on Thursday after it said that a combination of lirilumab and Bristol-Myers Squibb's PD-1 inhibitor Opdivo failed to provide clear evidence of benefit in patients with squamous cell carcinoma of the head and neck (SCCHN).

The firm also said that while the drug combination was tolerated, the assessment of efficacy from the ongoing exploration of doublet failed to show an “obvious development path” going forward.

“Clearly this is disappointing, but we remain convinced, based on broad preclinical evidence, that NK cells play an important role in cancer immunosurveillance,” said Mondher Mahjoubi, Innate’s chief executive.

“Together with Bristol-Myers Squibb, our partner, we will further examine these data to better understand the results and explore whether other combinations should be investigated.”

Lirilumab is a fully human antibody directed against the inhibitory killer-cell immunoglobulin-like receptors (KIRs) expressed predominantly on circulating natural killer (NK) cells.

BMS picked up global rights to the drug and other potential KIR receptors back in 2011 a deal with Innate worth $465 million.

Innate said discussions are ongoing regarding next steps for the programme.