Is Merck’s Next Big Thing Already Here

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The KEYTRUDA family of cancer drugs generated close to half of Merck's (MRK) third-quarter revenue. On the October 29 call, management said KEYTRUDA is approaching peak revenues for certain approved uses. Merck's newer drugs therefore matter more, and sales of one of them nearly doubled from a year earlier in the third quarter. Which drug is that, and how far has it come?

Merck's WINREVAIR Sold $694 Million In Fiscal Q3 2026

The drug is WINREVAIR, a treatment for adults with pulmonary arterial hypertension, a form of high blood pressure in the lungs. Management said WINREVAIR's third-quarter sales reflected strong demand from those patients, along with some help from stock built up by distributors.

Nearly 1,600 new patients in the U.S. received a prescription for WINREVAIR in the quarter. Outside the U.S., Merck (MRK) said its launches of the drug are still under way.

How Much Does WINREVAIR Add To Merck's Sales?

WINREVAIR accounted for about 3.8% of Merck's $18.1 billion revenue in the third quarter. A single drug at that level adds to growth, but it does not change a company of Merck's size on its own. Merck's next big thing is therefore not fully here yet: WINREVAIR is growing fast, but it is still a small part of revenue.

Management expects moderate revenue growth in 2027, with strong contributions from new product launches and animal health, partly offset by more than $2 billion of headwinds from generic competition for BRIDION, the Januvia family and Adempas. WINREVAIR is therefore one of several launches Merck needs to keep its revenue rising in 2027.

This matters for the stock, which returned 84.6% over the twelve months ended November 4, 2026, against 14.9% for the S&P 500. The stock's November 4 close was 3.3% below its highest close of the past year. The shares trade at 5.5 times sales, compared with 3.2 for the S&P 500. Investors already pay a premium for each dollar of Merck's sales.

Part Of WINREVAIR's Third-Quarter Sales Will Reverse

Management said $50 million of WINREVAIR's third-quarter sales came from the timing of customer purchases, and it expects that amount to unwind in the fourth quarter. This amount is a small part of what WINREVAIR sells in a quarter.

WINREVAIR's fourth-quarter sales are the number to watch when Merck next reports, which is expected in February 2027.

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