A blockbuster cancer treatment failed in a key study as the drug’s maker, Bristol-Myers Squibb, attempts to extend its usage to lung cancer patients.

Shares of the New Jersey pharmaceutical company are plunging before the opening bell.

Opdivo is already approved as a treatment for melanoma, kidney cancer and lung cancer following chemotherapy.

The latest late-stage study involved 541 patients who had received no prior treatment for lung cancer.

Shares of Bristol-Myers Squibb Co. plunged $13.67 to $61.65 in premarket trading.