MRK Up Nearly 10% in a Month: Should You Buy, Sell or Hold the Stock?

Core Insights - Merck's shares have increased by 9.6% over the past month, recovering from a dip following the third-quarter earnings report, which beat estimates for earnings and sales but saw Keytruda miss sales expectations [1][3] - The company has narrowed its sales guidance while raising its EPS outlook, and the stock has shown recovery due to positive pipeline updates and the acquisition of Cidara Therapeutics for approximately $9.2 billion [1][2] Keytruda's Performance - Keytruda remains Merck's most significant asset, accounting for over 50% of pharmaceutical sales, with sales reaching $23.3 billion in the first nine months of 2025, an 8% increase year-over-year [4][5] - The drug's growth is driven by its uptake in early-stage non-small cell lung cancer and continued momentum in metastatic indications [5] - Merck is pursuing strategies to enhance Keytruda's long-term growth, including innovative combinations and a new subcutaneous formulation approved by the FDA [6][7] Pipeline and M&A Activity - Merck's phase III pipeline has nearly tripled since 2021, positioning the company to launch around 20 new vaccines and drugs in the coming years, including a new pneumococcal conjugate vaccine and a drug for pulmonary arterial hypertension [9][10] - The acquisition of Verona for $10 billion added a novel treatment for chronic obstructive pulmonary disease, enhancing Merck's cardio-pulmonary portfolio [13] Challenges and Declines - Sales of the Gardasil vaccine, Merck's second-largest product, have declined by 40% in the first nine months of 2025, primarily due to weak demand in China [14][15] - Other vaccines and diabetes products are also experiencing declining sales, raising concerns about Merck's ability to diversify its product lineup ahead of Keytruda's patent expiration in 2028 [16][17] Stock Performance and Valuation - Merck's shares have underperformed the industry and the S&P 500, losing 6.5% year-to-date compared to a 14% increase in the industry [20][21] - The company's shares are trading at a forward P/E ratio of 10.04, lower than the industry average of 16.72, indicating a potentially attractive valuation [23] Future Outlook - Despite the challenges, Merck's new products are showing strong launches, and the approval of Keytruda Qlex may mitigate the impact of Keytruda's loss of exclusivity in 2028 [28] - The company is advised to adopt a wait-and-see approach due to uncertainties surrounding Gardasil's performance, competition for Keytruda, and rising pressures on other products [30]