Merck

Keytruda has reigned as oncology's apex predator for a decade—the PD-1 inhibitor generated $29.48 billion in 2024, an 18% increase from $25.01 billion in 2023, and hit $8.1 billion in Q3 2025 alone. Over 41 FDA-approved indications span solid tumors like a generalist species occupying diverse niches. September 2025 brought FDA approval for KEYTRUDA QLEX, a subcutaneous formulation covering most solid tumor indications—metabolic efficiency through faster administration. Yet Keytruda's 2028 patent expiration looms like the Cretaceous asteroid: biosimilar competition will obliterate monopoly rents that currently represent over half of Merck's pharmaceutical revenue. The organism's survival depends on adaptive radiation into adjacent therapeutic space before the catastrophe arrives.

Merck's 2024 revenue of $64.17 billion ranked it the world's third-largest pharmaceutical company, yet "virtually all" growth came from Keytruda. This resource concentration creates evolutionary vulnerability—specialization yields short-term dominance but long-term fragility when environments shift. The company acquired Harpoon Therapeutics in early 2024, adding T-cell engager MK-6070 targeting DLL3, and partnered with Daiichi Sankyo on three antibody-drug conjugates. These represent bet-hedging: diversifying the pipeline beyond PD-1 inhibition into next-generation oncology mechanisms. Management emphasizes pipeline diversification in every earnings call, projecting 20 new blockbuster drugs with $50 billion combined potential—though such forecasts often assume ideal conditions like greenhouse seedlings that wilt when transplanted to wild ecosystems.

For 2025, Merck expects $64.1-65.6 billion in revenue and $8.88-9.03 adjusted EPS, essentially flat growth as Keytruda's expansion slows toward its peak. GARDASIL vaccine sales face headwinds in China from consumer spending pressure, revealing how dependence on two mega-products (Keytruda + GARDASIL) amplifies market-specific shocks. The organism must accomplish what few pharmaceutical companies achieve: replace a dominant product's revenue before patent expiration. Analogies to oak trees are instructive—long-lived, resource-efficient, but vulnerable to sudden blight. Merck's next five years will determine whether it diversifies quickly enough to survive Keytruda's patent cliff, or whether it joins the list of pharmaceutical empires that peaked with a single molecule and never recovered their prior biomass.