On Tuesday's edition of Market Checkup, Motley Fool health-care analyst David Williamson looks at the biggest winners and losers in health-care stocks today.

Bristol-Myers Squibb (NYSE:BMY) took a hit recently, when it was unclear about its timeline for advancing its lead immuno-oncology drug candidate Nivolumab. While investors are excited about how this may pair up with Bristol's already approved drug Yervoy, management is taking a cautious pace while it tests out a number of different drug pairings. This delay has not only put doubt about the pairing in the mind of investors, but it has also given Merck (NYSE:MRK), which has a similar drug in development that would be a direct competitor, a chance to strike.

In this segment, David breaks this competitive race down for investors and discusses what to watch with these two companies in this space.