Merck Defends Its Offensive Strategy For Keytruda

While Merck & Co. Inc.'s Keytruda continues to trail Bristol-Myers Squibb Co.’s Opdivo and most of its sales continue to derive from the melanoma indication, the firm believes it can build its position in the checkpoint race with the first-mover advantage in first-line lung cancer and a “huge wall of data” it hopes will insulate the drug from follower competitors and potential price wars later on.

Merck had the first-to-market advantage with its PD-1 inhibitor Keytruda (pembrolizumab), with approval for metastatic melanoma in October 2014. But...