Will Lilly maintain above 55% U.S. incretin prescription share through H1 2026?

Current share at 60% with 5 consecutive quarters of gains provides a 5pp buffer above the 55% threshold. Novo's own 2026 guidance of -5% to -13% confirms the competitor does not expect meaningful supply normalization in H1 2026. Clinical superiority (47% greater weight loss, E3 evidence) provides structural prescriber preference beyond supply dynamics. Manufacturing advantage ($50B+ investment) creates a 2-4 year capacity lead that fully covers the H1 2026 timeframe. Even accounting for weak switching costs, reversing 5pp of share in 6 months from a position of momentum is extremely difficult.

The committee flagged this as a monitoring trigger because a failure scenario exists, but the base case strongly favors YES. Going from 60% to below 55% requires a 5+ point drop in at most 6 months. Novo hasn't begun to normalize supply, and their deeply negative guidance (-5% to -13%) suggests they won't in H1 2026. The 'every month' clause adds marginal risk since even one month below 55% triggers NO, but from a 60% base with compounding new Rx share (~2/3 of new prescriptions), any single month dropping below 55% requires an acute shock event like a major PBM formulary exclusion. The CVS Q3 2025 disruption is precedent but affected a single product/channel, not total incretin share.

The 'every month' resolution clause deserves careful attention. January and February 2026 are near-certain above 55% given current momentum. March-April likely safe. The danger zone is May-June if Novo supply normalization begins. However, Novo's -5% to -13% 2026 guidance strongly suggests they do NOT expect meaningful supply normalization even through year-end 2026. The committee's unresolved debate about structural vs temporal gains is relevant but cuts both ways: even if gains are partly supply-driven, the supply advantage persists through H1 2026 per Novo's own guidance. The committee assigned HIGH materiality to this debate, and the Moat Mapper's VERY HIGH confidence was partly on share trajectory. I weight this slightly lower than pure momentum would suggest due to the unresolved structural question.

This is a high-conviction YES. The 60% current share with a 55% floor gives 5pp of breathing room. Novo is in full retreat, guiding -5% to -13% for 2026 while Lilly guides +23-27%. The competitive divergence is widening, not narrowing. Weak switching costs are a long-term concern (years), not a 6-month concern. Clinical superiority is confirmed at E3 evidence level with 47% greater weight loss. Even a CVS-style PBM disruption would be unlikely to erase 5+ points of total incretin share in a single month. The only realistic failure scenario requires multiple simultaneous shocks.

A 5pp buffer from 60% with the primary competitor guiding deeply negative is a strong position for a 6-month hold question. The risks are real but theoretical within the H1 2026 timeframe. Manufacturing lead is 2-4 years per committee assessment, fully covering the resolution period. The 'every month' clause does add some risk since prescription data can be volatile month-to-month, but the buffer is large enough to absorb normal fluctuations. The only scenario for failure is a black swan PBM exclusion event or sudden regulatory action, neither of which the committee identified as high-probability near-term risks.

Ranking key factors by relevance: (1) 5pp buffer above threshold with 5 consecutive quarters of gains - this momentum is strong; (2) Novo guiding -5% to -13% for 2026 - competitor explicitly forecasting continued weakness; (3) 2/3 of new Rx share creates compounding gains, meaning Lilly's share is more likely to increase than decrease; (4) clinical superiority (47% greater weight loss) is structural, not temporal. Against: (1) weak switching costs cap long-term moat but don't threaten 6-month hold; (2) PBM formulary risk is real but episodic; (3) possible supply normalization in late H1 - but Novo's own guidance contradicts this. The committee's VERY HIGH confidence in DEFENSIBLE classification at post-earnings update strongly supports this assessment.

60% share with 55% floor means 5pp buffer. Novo guiding -5% to -13% for 2026 - they don't expect to recover share. Clinical superiority confirmed (47% greater weight loss). Manufacturing advantage holds through H1. Most salient fact: Novo's own negative guidance eliminates the primary bear case of supply normalization in the resolution window.

Committee assigned VERY HIGH confidence to DEFENSIBLE moat classification. Current share at 60% with 5 consecutive quarters of gains gives strong momentum. The 55% threshold is well below current levels. Main risk is supply normalization, but Novo's 2026 guidance (-5% to -13%) suggests this isn't imminent. The 6-month timeframe is too short for a 5pp reversal without an acute shock event.

5-point cushion above 55% threshold from current 60% share. Novo guiding negative for full year 2026. Clinical superiority (47% greater weight loss) drives structural prescriber preference beyond supply dynamics. Manufacturing advantage is temporal but 2-4 year lead means it holds through H1 2026. The 'every month' clause creates some risk since a single bad month resolves NO, but from 60% base, breaching 55% in any single month requires a major disruption. Slightly lower confidence due to the unresolved structural vs temporal debate.