Will MRK's Growing Pipeline Help Navigate the Looming Keytruda LOE?

Merck (MRK) is aggressively expanding its pipeline, which has nearly tripled since 2021, with plans for approximately 20 new drug and vaccine launches, many with blockbuster potential, to mitigate the impending loss of exclusivity for its top-selling cancer drug Keytruda in 2028. While Keytruda generated $7.21 billion in Q1 2025 sales, Merck is banking on strong initial launches of products like Capvaxive and Winrevair, alongside promising late-stage candidates including a GLP-1 agonist and ADCs, to drive future growth. However, uncertainty remains regarding the new portfolio's ability to fully offset Keytruda's patent cliff and competitive pressures, as reflected in MRK's year-to-date share underperformance of -19.9% and recent slight declines in earnings estimates, despite an attractive valuation relative to the industry.

Analysis

Merck is aggressively executing a strategy to mitigate the impact of the 2028 patent expiration of its blockbuster drug, Keytruda. The company has nearly tripled its phase III pipeline since 2021 through a combination of in-house development and M&A, and is now planning approximately 20 new drug and vaccine launches. Early commercial traction for new products like the vaccine Capvaxive and the PAH drug Winrevair is encouraging, and the pipeline shows diversification into high-potential areas such as antibody-drug conjugates (ADCs) with Daiichi Sankyo and the lucrative obesity market via an in-licensed oral GLP-1 agonist. However, significant uncertainty remains as to whether this new portfolio can fully offset the revenue loss from Keytruda, which still grew 6% year-over-year to $7.21 billion in the first quarter of 2025. This uncertainty is amplified by intense competition from rivals like AstraZeneca's Imfinzi, which saw 16% sales growth. The market appears to be pricing in this risk, as reflected by the stock's 19.9% year-to-date decline, which significantly underperforms the industry's 1.8% decrease. This negative sentiment is further supported by minor downward revisions to 2025 and 2026 earnings estimates, despite the company trading at an attractive forward P/E ratio of 8.56, well below both industry and its historical averages.

Key Decisions for Investors

• Investors should consider the stock's currently attractive valuation, with a forward P/E of 8.56, as a potential deep-value opportunity, but must weigh this against the significant execution risk associated with replacing Keytruda's revenue post-2028.
• Closely monitor the sales trajectory of newly launched products Capvaxive and Winrevair, as their commercial success is a primary indicator of the company's ability to navigate the upcoming patent cliff.
• Pay close attention to late-stage clinical trial data and regulatory milestones for key pipeline assets, particularly the Daiichi-Sankyo-partnered ADCs and the oral GLP-1 candidate for obesity, as these represent major potential growth drivers.
• Track Keytruda's market share and growth against competitors like Bristol Myers' Opdivo and AstraZeneca's Imfinzi, as any erosion ahead of the 2028 patent expiration would be a significant negative catalyst for future earnings.