On Aug. 5, Bristol-Myers Squibb announced that its blockbuster checkpoint inhibitor nivolumab (Opdivo) failed a Phase III trial as monotherapy in patients with previously untreated non-small cell lung cancer (NSCLC). The drug missed its primary endpoint of progression-free survival in patients whose tumors expressed programmed death ligand 1 (PD-L1) at 5%.

Although the company did not release data from the study, it reported that it will complete a full evaluation of the CheckMate -026 data in the future. The drug is a humanized IgG4 anti-PD 1 monoclonal antibody similar to pembrolizumab (Keytruda). The drugs block a signal that prevents activated T cells from attacking cancer cells. Both drugs are approved for the treatment of a variety of cancers, including metastatic melanoma, advanced renal cell cancer, and NSCLC in patients who have not responded to previous treatment.

The failure of nivolumab as initial therapy for NSCLC is a major blow to Bristol-Myers Squibb, which saw its stock drop 16% the day of the announcement. Meanwhile, pembrolizumab reportedly has shown promising results in the same role, although results have not been published.