Merck Trading Near 52-Week High: Is the Stock a Buy, Hold or Sell?

Merck shares are trading at $150.33, about 4% below their $156.92 52-week high, after gaining 42.8% year to date; Keytruda is projected to reach $35 billion in peak sales by 2028. Positive phase III melanoma data for Moderna-partnered intismeran autogene plus Keytruda and contributions from newer products support the post-Keytruda pipeline, which Merck estimates represents more than $70 billion of non-risk-adjusted opportunity by the mid-2030s. Offsetting these strengths, Gardasil sales fell 9% in the first half of 2026, Keytruda faces a 2028 patent cliff, and 2026 EPS estimates declined to $2.97 from $4.31 over the past 60 days.

Analysis

MRK’s near-peak valuation leaves little room for execution slippage: the relevant debate is not whether Keytruda can grow into 2028, but whether post-2028 assets can replace a high-margin franchise quickly enough to prevent an earnings trough. The sharp reset in 2026 EPS expectations despite share-price strength implies investors are already looking through near-term earnings; that setup is vulnerable if 2027 guidance shows acquisition expense, generic erosion, or vaccine weakness persisting longer than modeled. A sustained premium multiple requires credible product-level revenue disclosure and margin trajectories rather than aggregate long-range pipeline opportunity claims.

The Moderna collaboration is strategically more valuable to MRNA than MRK in the next 6-18 months. For MRK, personalized neoantigen therapy is a potential lifecycle-management tool that could defend Keytruda’s treatment ecosystem but may also raise manufacturing complexity and constrain gross margins versus standalone checkpoint inhibition. For MRNA, a successful registrational path would validate an oncology platform beyond respiratory vaccines, potentially expanding partnering leverage; however, commercial economics, regulatory timing, and reproducibility across larger tumor settings remain the missing variables.

Competitive risk is asymmetric: a successful PD-(L)1/VEGF bispecific could pressure the standard-of-care backbone before patent expiry, while biosimilar entry later creates a much steeper downside because of MRK’s concentration. The more immediate catalyst is quarterly evidence that newer launches are offsetting the loss of mature products; the structural catalyst is 2027 visibility on replacement revenue. Consensus may be underweight the possibility that subcutaneous administration supports share retention after IV biosimilars emerge, but it should not be assumed to eliminate pricing pressure.

Key Decisions for Investors

• Maintain MRK as a neutral/underweight healthcare exposure rather than chase strength; reassess after next earnings only if 2027 EPS guidance stabilizes and new-product growth demonstrably offsets mature-product declines. Falsifier for caution: upward 2027 consensus revisions plus durable operating-margin guidance.
• Express relative oncology-platform upside via long MRNA / short MRK in a 6-12 month, beta-adjusted pair, sized modestly. The trade benefits if oncology data rerates MRNA while MRK faces estimate de-risking; exit if MRNA’s regulatory/commercial pathway is delayed or MRK provides quantified post-2028 replacement revenue above expectations.
• For existing MRK longs, consider 3-6 month collars around earnings rather than outright calls: elevated valuation and negative estimate momentum create unfavorable upside/downside skew. Remove hedges if vaccine/channel normalization and launch uptake drive a clear upward revision cycle.
• Monitor AZN and other PD-(L)1 competitors for PD-1/VEGF data and regulatory updates over the next 3-12 months; a superior efficacy/safety signal is an alert to increase MRK hedges, not yet a standalone short absent evidence of displacement.