MRK Stock Up Nearly 14% So Far This Week: What's Driving It?

Merck's stock surged nearly 14% this week, primarily driven by renewed investor optimism across the pharmaceutical sector following Pfizer's landmark deal with the Trump administration. This agreement aims to alleviate concerns over drug pricing and tariffs by linking U.S. investment commitments to tariff exemptions, potentially setting a precedent for other major drugmakers. Additionally, Merck received FDA approval for a subcutaneous Keytruda formulation, which extends patent protection for its blockbuster drug, further bolstering its outlook despite recent underperformance and an attractive 9.49x forward P/E valuation.

Analysis

Merck's stock has experienced a significant rally, gaining nearly 14% this week, driven by both sector-wide tailwinds and company-specific positive developments. The primary macro catalyst is Pfizer's landmark deal with the Trump administration, which has alleviated investor concerns regarding MFN (Most Favored Nation) drug pricing and tariffs, sparking optimism that Merck and other major pharmaceutical companies may secure similar agreements. This renewed confidence is reflected in the broad rally across the sector, with peers like Eli Lilly and AstraZeneca also gaining around 13%. Concurrently, Merck received a critical FDA approval for a subcutaneous formulation of its blockbuster drug, Keytruda, which extends patent protection well beyond the 2028 exclusivity loss of the current intravenous version, thereby safeguarding a key long-term revenue stream. Despite this positive momentum, the stock has underperformed year-to-date with a 10% decline against an 8.3% industry rise. However, from a valuation standpoint, Merck appears attractive, trading at a 9.49 forward P/E ratio, significantly below the industry average of 15.93 and its own five-year mean. This is juxtaposed with stable 2025 earnings estimates and a slight downward revision for 2026.

Key Decisions for Investors

• Given the stock's attractive valuation at a 9.49 forward P/E and the powerful dual catalysts of a de-risked regulatory environment and the Keytruda patent extension, the recent year-to-date underperformance may represent a compelling entry point for long-term investors.
• Investors should closely monitor for any announcements regarding Merck securing a pricing and investment deal with the administration similar to Pfizer's, as this would serve as a major confirmation of the bull thesis and could unlock further upside.
• While the outlook has materially improved, it is prudent to weigh the positive catalysts against the slight downward revision in 2026 earnings estimates and the stock's Zacks #3 (Hold) rank, recognizing that execution on the Keytruda SC commercial transition is critical for sustained performance.