What Will Decide Merck Stock Over The Next Six Months?

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Merck (MRK) stock returned 66.3% over the twelve months to November 12, 2026, against 12.2% for the S&P 500. Yet management has already said it expects only moderate sales growth in 2027, a year it calls another year of investment in its pipeline and new launches. Below are the events most likely to move Merck stock over the next six months.

Generic Rivals For Three Older Drugs

Merck’s older drugs Bridion, Adempas and the Januvia family will lose sales to generic competition in 2027. Management puts that hit at more than $2 billion for the year. Generic copies of Bridion have already entered the market, while the Januvia family faces a government-set price for Janumet that takes effect on January 1, 2027.

Those losses compare with $67.4 billion of revenue over the twelve months to September 2026. Management expects strong contributions from new product launches and the animal health business, partly offset by those losses, and that is why it sees only moderate sales growth in 2027. Management also expects underlying operating expenses to rise at a mid- to high-single-digit rate in 2027 as it invests behind its pipeline and launches. The thing to watch is what the new launches add against those losses, which each quarterly report will show.

Keytruda’s Slowing Growth And Price Setting

Merck’s cancer drug Keytruda faces two changes. Management sees its growth moderating now, and the company expects the therapy to be selected during 2027 for government price setting. The set price would take effect on January 1, 2029. The Keytruda family sold $8.6 billion in fiscal Q3 2026, against total company revenue of $18.1 billion.

Excluding currency moves, those Keytruda sales grew 6% in the quarter. Management said growth is moderating because the drug has reached peak use in several cancers. Keytruda family sales growth, reported every quarter, is the measure to watch, along with whether the drug is named for price setting during 2027.