Shares of Merck & Co. (MRK) climbed on Monday, April 16, while Bristol-Myers Squibb Co. (BMY) shares dropped after the drugmakers released data from their respective lung cancer studies.

Merck appears to be the "clear winner so far," according to Credit Suisse Securities (USA) LLC analyst Vamil Divan in a note. Merck's data was "better-than-expected across all patient subgroups," while Bristol-Myers' data "shows early signs of a survival benefit, but questions remain until we see full data," Divan wrote.

Kenilworth, N.J.-based Merck said a Phase 3 study of Keytruda in tandem with pemetrexed (Alimta) and platinum chemotherapy for metastatic lung cancer cut the risk of death by half versus chemotherapy alone. 

Meanwhile, also on Monday, rival Bristol-Myers unveiled initial results from its own Phase 3 clinical trial of Opdivo (nivolumab) plus low-dose Yervoy (ipilimumab) in first-line metastatic lung cancer. Findings showed that the treatment lowered the risk of progression or death by 42% compared to chemotherapy alone.

Shares of Merck gained 3.1% to $58.92 in morning trading. The stock is up 4.7% year-to-date but down 6% over the last 12 months.

Progression-free survival refers to the period of time during and post-treatment that a patient lives with the disease but it does not worsen.

Shares of New York Bristol-Myers fell more than 7% to $54.26. The stock is down nearly 10% this year but up 4.1% over the last 12 months.

Merck and Bristol-Myers are presenting data from the studies at the Association for Cancer Research's annual meeting in Chicago.