Merck Stock Fluctuates Between Cancer Data Hope and Patent Cliff Risks
This article was created with the help of artificial intelligence.
Key Takeaways
- Merck stock traded at $113.87 on June 18, 2026, declining 1.36% from the previous day.
- Kelun-Biotech published positive Phase III study results on May 22, 2026 for a Keytruda combination treatment for lung cancer.
- Merck faces significant revenue risks from the impending patent expiration of Keytruda, as cheaper generics can take over the market.
- The stock showed multiple declines of approximately 1 to 2 percent since April 2026, while broader market indices rose on the same days.
- Merck & Co. is a US company and not to be confused with German Merck KGaA from Darmstadt.
US pharmaceutical company Merck & Co. (ticker: MRK) closed at $113.87 on June 18, 2026, representing a decline of 1.36% compared to the previous day. Financial platform Zacks reported this. The price movement reflects a volatile phase that investors have observed in the pharmaceutical stock since April 2026.
Volatile price movement since April 2026
As early as April 24, 2026, Merck stock fell 2.37% to $111.90, as Zacks reported. Previously, on April 7, 2026, the stock declined 1.3% to $119.28. In all three cases, the stock moved against the general market trend downward, while broader indices gained on those days.
Positive cancer study data as price driver in May
Study results published on May 22, 2026 provided a bright spot. According to Barron's, Merck shares rose after partner Kelun-Biotech presented positive data from a late-stage clinical trial (Phase III) for a combination treatment with Keytruda for lung cancer. Keytruda is Merck's top-selling cancer drug and a central pillar in the company's product portfolio.
The study results show that Merck is developing further growth prospects beyond Keytruda – an important signal for investors who do not want to reduce the company to a single blockbuster drug.
Patent cliff risk remains central issue
Investment platform Motley Fool addressed in early June 2026 in an analysis the strategic challenge facing Merck: the expiration of patents on key drugs and growth prospects thereafter. A patent cliff refers to the point at which patent protection for a drug expires and cheaper generics can enter the market. This typically leads to significant revenue losses for the affected branded drugs.
For Merck, this issue is particularly relevant because Keytruda – despite successful combination approaches – faces patent expiration in the coming years. Analysts are therefore closely monitoring how the company diversifies its product portfolio and opens up new revenue sources.
Assessment for DACH investors
Merck & Co., headquartered in the US, is not to be confused with German Merck KGaA from Darmstadt. The two companies share a common historical root but have operated independently for decades. Merck & Co. is traded on the New York Stock Exchange in US dollars. DACH investors who invest in the US company bear, in addition to price risk, also currency risk between the euro or Swiss franc and the US dollar.
The fluctuations of recent months show that Merck is under valuation pressure despite positive research results. The question of how the company can grow long-term without full patent protection for Keytruda will likely continue to influence price movement in the future.