Should Investors Be Worried About Merck's Keytruda?

Merck's (NYSE: MRK) cancer immunology drug, Keytruda, is already one of the best-selling drugs in the world and is well on track to becoming the No. 1 drug by revenue within the next few years. Having already been approved to treat a number of different cancer types, Keytruda is poised to play a crucial role in the company's future sales growth.

Over the past couple of weeks, however, Keytruda has been hit by some mixed, if not outright disappointing, clinical results. Let's take a closer look at some of these developments and whether they should worry pharmaceutical investors.

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Source Fool.com