Merck & Co.

Winrevair achieved $1.4B in its first full year — one of the fastest specialty launches ever. PAH is chronic, progressive, and undertreated. Winrevair is the only disease-modifying therapy (addresses underlying vascular remodeling, not just vasodilation). Patient lifetime value is enormous given chronic dosing. The $7B peak may be conservative if earlier-line use expands and combination regimens become standard. PAH diagnosis is also expanding with improved right heart catheterization and screening.

PAH is a niche market (~30-50K treated patients in the US). Competition from existing vasodilators limits share. Pricing pressure in specialty may compress unit economics. The $7B peak already assumes dominant share.

SubQ Keytruda extends brand life by 2-3 years. ADC combinations (Padcev-pembro, Dato-pembro) create branded regimens that survive LOE. Pipeline (V940, sotatercept, tulisokibart) fills the gap.

Keytruda is $31.7B — over 50% of MRK revenue. No drug in pharma history has replaced a $30B+ franchise. SubQ extends brand life marginally but biosimilar pembrolizumab will still take 60-70% of volume. The math: even if SubQ retains $10B and pipeline delivers $15B by 2030, MRK is still down $5-10B in revenue vs peak. At current margins, that is $3-5/share in EPS. The pipeline must deliver SIMULTANEOUSLY on Winrevair, tulisokibart, V940, enlicitide, and efinopegdutide — each with binary clinical risk. The probability of all succeeding is low.