(Reuters) – Bristol-Myers Squibb Co said on Friday that its blockbuster cancer drug Opdivo failed to meet the main goal in a late-stage trial on patients with a type of lung cancer, whose condition had relapsed after chemotherapy.

The drug failed to extend overall survival in patients suffering from small cell lung cancer, an aggressive form of the disease, when compared to patients already on chemotherapy.

Opdivo has already been approved to treat several forms of cancer, including skin and lung cancer.

As the leading cause of cancer deaths, lung cancer represents the biggest opportunity for companies seeking to exploit the power of modern cancer therapies.

The drug’s failure to meets its main goal in the study comes nearly two months after the U.S. Food and Drug Administration approved the drug to treat patients whose lung cancer had progressed despite undergoing two previous therapies.

The drug competes with Merck & Co’s Keytruda and belongs to a class of treatments that work by activating the immune system to attack tumors.

Bristol’s Opdivo generated sales of $1.63 billion in the second quarter, while Merck’s Keytruda raked in $1.67 billion.

(Reporting by Manas Mishra and Aakash Jagadeesh Babu in Bengaluru; Editing by Shounak Dasgupta and Shailesh Kuber)