Eli Lilly shares fell 2% after mixed weekly GLP-1 prescription data showed Mounjaro rising to about 758,400 total prescriptions while Zepbound slipped to 615,300. Combined prescriptions for Lilly’s GLP-1 franchise were down 0.3% week over week, though the company held roughly 59% weekly new prescription share. Morgan Stanley said it sees about 6% upside to 2026 Mounjaro/Zepbound estimates, but the launch data for Foundayo remained modest at about 3,700 prescriptions in its second week.
The key read-through is not that Lilly is losing share, but that the cadence of growth is normalizing just as the market is looking for evidence that the next leg of GLP-1 expansion can support premium expectations. A flat-ish weekly share print with softer Zepbound net adds suggests the category is transitioning from scarcity-driven acceleration to more elastic demand, where prescription growth becomes more sensitive to payer access, refill continuity, and dose escalation rather than pure new patient conversion.
That matters for suppliers and competitors in different ways. IQVIA-based weekly data can move sentiment on Lilly and Novo near term, but the second-order winners are likely the channel operators and data intermediaries that benefit from more volatile monitoring demand, while the first casualty is the multiple on the obesity complex if investors start underwriting every week as a data point rather than a trend. The launch comparison for Foundayo is also instructive: the market may be overestimating how quickly a new oral entrant can meaningfully cannibalize injectables when physician behavior, titration, and patient persistence create a long adoption curve.
The bigger contrarian point is that the move looks tactically overdone unless the weekly trend persists for several reads. A 2% pullback on a modest deceleration in aggregate prescriptions is more about positioning than fundamentals; the real risk is not this week’s print, but whether payer pressure or competitive discounting forces a lower terminal growth assumption over the next 6-12 months. If that happens, the whole GLP-1 basket de-rates together, but if weekly growth re-accelerates, today’s dip becomes a buying opportunity.
For now, the cleanest setup is to fade the reflex selloff while using catalysts to hedge. The data still supports a structurally large obesity market, but the cadence suggests investors should stop extrapolating linear weekly gains into 2027 growth rates.
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mildly negative
Sentiment Score
-0.15
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