Why Wall Street Cools on Merck Stock Despite Cancer Vaccine Success

2026-08-21 companies

New York, Friday, 21 August 2026.
RBC Capital downgraded Merck to Sector Perform following a steep stock rally, warning that its $150 valuation is unprecedented ahead of Keytruda’s $30 billion patent loss in 2028.

RBC Capital Adjusts Rating Amid Volatility

RBC Capital Markets downgraded Merck & Co. (NYSE: MRK) to “Sector Perform” from “Outperform” on 20 August 2026, citing valuation concerns following a significant stock rally [1][4]. The adjustment came as the stock experienced profit-taking, declining approximately 2.1% to trade near $149, shortly after surging 12.60% on 19 August 2026 [1][4]. Analysts at the Canadian bank raised their price target for the pharmaceutical giant to $150 from $142, representing a 5.634 increase in the target despite the downgrade [5][6].

RBC Capital Adjusts Rating Amid Volatility

The rating adjustment reflects a cautious stance on the company’s near-term valuation relative to its long-term risks [4]. RBC Capital analysts noted that the current stock price reflects “unprecedented” valuation levels for a company facing a major loss of exclusivity within two years [2][6]. Consequently, the firm believes the risk-reward profile is now fairly valued, with substantial optimism already embedded in the multiple [4].

Clinical Trial Success and Market Reaction

The recent volatility stemmed from positive Phase 3 clinical trial results announced on 19 August 2026, involving a cancer vaccine developed in partnership with Moderna (NASDAQ: MRNA) [1][2]. The INTerpath-001 trial tested the combination of personalized therapy Intismeran Autogene with Keytruda for surgically removed high-risk melanoma, demonstrating extended recurrence-free survival compared to Keytruda monotherapy [2][6]. Following the announcement, Moderna shares skyrocketed 176.97% before falling 19.34% during the subsequent profit-taking session [1][4].

Clinical Trial Success and Market Reaction

Merck and Moderna are currently conducting nine Phase 2 and Phase 3 trials for the combined therapy across melanoma, lung, bladder, and kidney cancers [2]. The trial results surpassed expectations, leading BMO Capital to project $5.6 billion in potential peak revenue from the INTerpath-001 trial alone [2][6]. Despite the clinical success, the immediate market reaction highlighted investor sensitivity to valuation metrics alongside clinical data [3][4].

Competing Analyst Perspectives

While RBC Capital adopted a cautious tone, other major financial institutions maintained bullish outlooks on Merck & Co. [1][6]. Goldman Sachs adjusted its price target to $160 from $140 while maintaining a “Buy” rating, and UBS raised its target to $175 from $145 [1]. Additionally, BofA maintained a “Buy” rating with a price target of $166, citing confidence that Merck can offset Keytruda’s patent challenges with pipeline growth [2][6].

Competing Analyst Perspectives

The divergence in analyst ratings underscores the tension between immediate valuation concerns and long-term pipeline potential [4]. Keytruda, Merck’s top-selling drug, generated over $30 billion in 2025, representing nearly 50% of total revenue [2]. Patents covering Keytruda begin expiring in 2028, creating a defined timeline for the company to establish new revenue streams [6].

Valuation and Future Outlook

RBC Capital analyst Trung Huynh emphasized that further stock gains would require an acceleration in pipeline momentum versus already very high expectations [4][6]. The firm noted “modest mid-term growth” prospects until new products can compensate for the impending patent loss [1][2]. This perspective suggests that while the clinical data is strong, the financial integration of these advancements may take time to materialize in the stock price [4][5].

Valuation and Future Outlook

Retail investor sentiment remains highly optimistic, with Stocktwits data showing “bullish” sentiment and “extremely high” message volumes as of 19 August 2026 [2]. Some retail investors projected a $200 price target by the end of 2026, contrasting with the more conservative institutional targets [2]. As the market digests the clinical news and analyst ratings, Merck & Co. stock performance will likely depend on balancing these competing narratives of innovation and valuation [3][6].

Sources

Pharmaceuticals Stock Downgrade