Merck & Co. stock trades near 52-week high as Keytruda faces new biosimilar and trial challenge

Merck & Co., Inc. stock (ISIN US58933Y1055) is trading near its recent 52-week high, with shares around 152.32 USD as of early September 2026 on the New York Stock Exchange, valuing the U.S. pharmaceutical group at approximately 369.73 billion USD according to market data compiled by ad-hoc-news and stock portals as of September 2, 2026.The same overview shows the stock close to a 52-week high of 156.92 USD, underlining how strongly the market is pricing Merck’s oncology franchise.

Keytruda faces biosimilar and trial pressure

A key topic for Merck & Co. investors on September 4, 2026 is fresh competitive pressure on its flagship immunotherapy Keytruda, including a new biosimilar partnership and clinical trial data favoring a rival drug.According to a report in Economic Times Pharma updated on September 4, 2026, India-based Cipla has licensed exclusive U.S. rights from China’s Qilu Pharmaceutical for QL2107, a biosimilar version of Keytruda (pembrolizumab) for the U.S. market, ahead of Keytruda’s patent expiry in 2028. The same report highlights that Keytruda generated more than 31 billion USD in sales in 2025, illustrating the size of the market that biosimilar entrants are targeting.

Competitive pressure is also emerging from novel therapies designed to outperform PD-1 inhibitors like Keytruda. In a broader market piece on September 3, 2026, a U.S. stock-market report noted that Summit Therapeutics surged after its partner Akeso announced Phase 3 data from the HARMONi-2 trial in advanced non-small cell lung cancer, where ivonescimab monotherapy delivered a statistically significant survival advantage over Keytruda in PD-L1-positive patients.The same article states that Merck shares slipped 0.9 percent on the news, reflecting investor sensitivity to clinical readouts that could reshape standard-of-care regimens.

Regulatory wins support Keytruda demand

Despite these challenges, recent regulatory decisions continue to broaden Keytruda’s addressable market and underpin Merck & Co.’s revenue base. On September 4, 2026, a Chinese market-news service reported that Merck announced approval from China’s National Medical Products Administration (NMPA) for Keytruda (pembrolizumab) in locally advanced squamous cell carcinoma of the head and neck.The report describes approval for use as neoadjuvant monotherapy in adult patients with resectable disease whose tumors express PD-L1, followed by adjuvant treatment with pembrolizumab plus radiotherapy with or without cisplatin after surgery, and subsequent pembrolizumab monotherapy. For investors, such label expansions in major markets like China help support continued growth even as patent expiries and biosimilars approach.

Keytruda’s commercial importance is underlined by data from a corporate-news summary that cites Merck & Co. reporting quarterly Keytruda sales of 8.4 billion USD in its latest figures, with oncology revenues a major contributor to the group’s performance.A news summary on September 4, 2026 ties the 8.4 billion USD quarterly Keytruda sales figure to the same biosimilar deal, emphasizing the revenue at stake for Merck over the coming years. Compared with the 31 billion USD Keytruda revenue in 2025 mentioned in another report, this quarterly level shows that the drug continues to grow strongly on an annualized basis.

Representative product: Keytruda as Merck’s oncology cornerstone

Keytruda is the representative product that best captures Merck & Co.’s current growth story and risk profile. Originally approved in melanoma and lung cancer, the PD-1 inhibitor has steadily expanded into indications across more than 20 tumor types and over 45 cancer types and stages, according to an overview of its usage in an article on biosimilar development.That report notes that Keytruda until recently ranked as the world’s top-selling drug, underscoring why competitors and biosimilar makers are keen to position alternatives.

For shareholders, Keytruda’s performance translates directly into Merck & Co.’s financial trajectory. With quarterly Keytruda sales of around 8.4 billion USD in Merck’s most recent reported quarter and 2025 full-year revenue from the drug above 31 billion USD, the oncology franchise accounts for a substantial share of group sales and profit.The sales data point to continued demand growth, but the latest Phase 3 lung-cancer trial where ivonescimab outperformed Keytruda also shows that Merck will need to defend its lead with combination regimens and new indications to sustain that momentum.

Merck & Co. stock valuation stays elevated

From a stock-market perspective, Merck & Co. shares remain highly valued relative to the broader pharmaceutical sector, with the stock trading within a few dollars of its 52-week high of 156.92 USD as of early September 2026.A German-language quote overview highlights that the shares stood at 150.78 USD on September 2, 2026, only a few dollars below the 52-week peak, implying a year-to-date gain above 40 percent. Separate analyst-data pages show a recent closing price of 152.34 USD on September 3, 2026 and a one-year performance of plus 44.73 percent, with an average analyst price target around 148.73 USD.MarketScreener data therefore suggest the shares are trading modestly above the consensus target, a sign that investors are paying a premium for Merck’s oncology pipeline strength.

Institutional portfolio moves reflect this high valuation and ongoing demand for the stock. In a September 4, 2026 filing summary, a U.S. investment firm was reported to have trimmed its Merck & Co. position while the article noted that the shares opened at 152.32 USD on the relevant trading day and were up around 0.4 percent in the latest session.The same price-performance section emphasises that shares recently traded close to the 12-month high again, indicating that even minor bouts of profit-taking from institutions occur against a backdrop of strong overall performance.