Merck & Co. (MRK) Advances on Robust Keytruda Sales and Positive Clinical Trial Results

Impax Asset Management's "Impax US Sustainable Economy Fund" released its Q4 2025 investor letter. A copy of the letter can be downloaded here. The fund reported that equity markets remained volatile during the quarter amid concerns over elevated valuations and financing for large-scale data center investments, although the portfolio modestly outperformed the Russell 1000 benchmark on the back of sustainability tilts and stock-specific gains, particularly within Health Care and Financials. On an annual basis, the Fund’s Institutional Class delivered a total return of 16.00% in 2025, compared to 17.37% for the Russell 1000, reflecting the impact of sector allocation and company-level developments such as gains in pharmaceutical and payment processing holdings and weakness in certain Consumer Staples names. Management noted that performance was influenced more by changing market leadership than macroeconomic deterioration, while maintaining a cautiously optimistic outlook supported by falling interest rates, resilient corporate earnings, and continued investment in structurally advantaged businesses positioned to benefit from the transition toward a more sustainable economy. In addition, please check the Fund’s top five holdings to know its best picks in 2025.

In its fourth-quarter 2025 investor letter, Impax US Sustainable Economy Fund highlighted stocks like Merck & Co., Inc. (NYSE:MRK). Merck & Co., Inc. (NYSE:MRK) is a multinational biopharmaceutical company leveraging a robust oncology and immunology portfolio—led by blockbuster drug Keytruda—to drive sustained revenue growth and global market share expansion. The one-month return of Merck & Co., Inc. (NYSE:MRK) was 9.41% while its shares traded between $73.31 and $123.33 over the last 52 weeks. On February 17, 2026, Merck & Co., Inc. (NYSE:MRK) stock closed at approximately $121.57 per share, with a market capitalization of about $303.66 billion.

Impax US Sustainable Economy Fund stated the following regarding Merck & Co., Inc. (NYSE:MRK) in its Q4 2025 investor letter:

"Merck & Co., Inc. (NYSE:MRK) (Health Care, Pharmaceuticals) demonstrates outstanding Corporate Resilience across governance, environmental and social dimensions. The organization is strategically positioned to leverage opportunities in Health Care Access and Innovation. During the quarter, Merck's shares advanced due to robust sales of its oncology and immunology medications, notably Keytruda, which continued to expand its global market share. Positive clinical trial results and an upward adjustment to 2026 earnings guidance further enhanced market confidence."

Merck & Co., Inc. (NYSE:MRK) is not on our list of 30 Most Popular Stocks Among Hedge Funds. As per our database, 92 hedge fund portfolios held Merck & Co., Inc. (NYSE:MRK) at the end of the third quarter, which was 92 in the previous quarter. While we acknowledge the risk and potential of Merck & Co., Inc. (NYSE:MRK) as an investment, our conviction lies in the belief that some AI stocks hold greater promise for delivering higher returns and doing so within a shorter time frame. If you're looking for an extremely undervalued AI stock that also stands to benefit significantly from Trump-era tariffs and the onshoring trend, see our free report on the best short-term AI stock.

In another article, we covered Merck & Co., Inc. (NYSE:MRK) and shared the list of best medical research stocks to buy according to hedge funds. In addition, please check out our hedge fund investor letters Q4 2025 page for more investor letters from hedge funds and other leading investors.

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Disclosure: None. This article is originally published at Insider Monkey.