Key Takeaways Keytruda drives about 50% of MRK's pharma sales and grew 6% year over year in Q1 2025. MRK is pursuing mRNA combos, new formulations, and new drugs to extend Keytruda's momentum. Winrevair and pipeline strategies aim to cushion MRK's top line post-Keytruda patent expiry in 2028.Merck (MRK) boasts more than six blockbuster drugs in its portfolio, with the blockbuster PD-L1 inhibitor Keytruda being the key top-line driver. Keytruda, approved for several types of cancer, alone accounts for arou ...