Is Merck Stock Reaching A Valuation Ceiling At 6x Sales?

August 27th, 2026 · by Trefis TeamMRKYTD+47.6%SPYYTD+12.6%XLVYTD+12.6%Analyze MRK →The oncology franchise that still carries about half of Merck is decelerating while the stock trades near its high.

Merck (MRK) has been a very good stock lately: up 85.5% over the past twelve months, against 20.3% for the S&P 500, and now trading at about 98% of its fifty-two-week high. That price leaves little room for disappointment. A critical determinant of whether it holds will likely be how much of Merck’s top line remains tied to its core oncology franchise rather than early pipeline headlines.

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$8.4 Billion Of A $16.6 Billion Quarter Sits In One Franchise

In the second quarter of 2026 the KEYTRUDA family, which includes KEYTRUDA and KEYTRUDA QLEX, sold $8.4 billion, against total company revenue of $16.6 billion. Roughly half of what Merck sells comes out of one franchise, and it is the half with an expiry date. Management frames the loss-of-exclusivity period as a hill rather than a cliff, but the hill starts from half the company’s revenue.

KEYTRUDA Growth Slowed From 8% To 4% In One Quarter

That franchise grew 8% year over year in the first quarter of 2026, excluding currency, to $8.0 billion, helped by Q1 wholesaler inventory build that management expects to unwind in the third quarter. In the second quarter of 2026, on the same basis, it grew 4% to $8.4 billion. The rate still halved in one step, and the CFO has said total U.S. KEYTRUDA growth will moderate as the drug reaches peak penetration across several key indications. The cliff has not arrived; its approach is already in the reported line.

WINREVAIR Grew 75% And Is Still About 7% Of KEYTRUDA

The bull answer is the pipeline: management points to more than $70 billion of commercial opportunity across over 20 new products by the mid-2030s. The clinical proof points behind the rally are real, and so are the regulatory ones: the FDA approved LIPFENDRA, the first and only oral PCSK9 inhibitor. The launches cannot yet carry weight. WINREVAIR, Merck’s pulmonary arterial hypertension drug, sold $588 million in the second quarter of 2026, up 75%, about 7% of what the KEYTRUDA family sold in the same three months. A company with half its revenue in one franchise is a different proposition from the Trefis High Quality Portfolio, which does not depend on the handful of largest technology names to produce its returns.

At 5.7 Times Sales Merck Is Near Its Ten-Year Ceiling

Revenue is not the problem: it grew 4.6% over the past twelve months, better than the 1.8% pace of the four quarters before it, though short of its 8.7% five-year compound annual rate. What has moved is the price. On sales the stock is at 5.7 against a ten-year high of 5.9 and a low of 3.1. Mid-single-digit growth is being paid for at the top of that ten-year range.

The Third Quarter Of 2026 Carries A $250 Million KEYTRUDA Headwind

The risk is timing: the price already assumes a handover from KEYTRUDA that has not happened. The comparison gets harder in the third quarter of 2026: by the company’s own account, roughly $250 million of wholesaler purchase timing bolstered KEYTRUDA in the third quarter of 2025 and will not repeat. Watch whether the franchise still prints positive growth against that inflated base. Implied volatility sits at 28, in the 72nd percentile of its trailing one-year range, so anyone adding near the high should see how large a move the options market is pricing.

Concentration Risk in a Changing Pipeline

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