Oral Weight-Loss Drug Launch Expands Market; Eli Lilly’s Zepbound Growth Remains Unaffected

Overview

This report provides J.P. Morgan’s latest prescription data tracking update on Eli Lilly’s weight-loss drug business. The core conclusion is that despite the strong initial performance of competitor Novo Nordisk’s oral Wegovy, it has primarily expanded the overall market size for weight-loss drugs without significantly impacting Eli Lilly’s flagship product Zepbound (tirzepatide) in terms of market share or new patient acquisition. The firm maintains its 'Overweight' rating on Eli Lilly, viewing this trend as positively indicative for Eli Lilly’s upcoming oral drug orforglipron.

Core views

Oral drugs as market expanders: The report notes that the introduction of oral GLP-1 drugs is perceived by the market as category expansion, primarily attracting patients with lower BMI, needle aversion, or greater price sensitivity. Data shows that oral Wegovy reached approximately 143,000 total prescriptions (TRx) in its 19th week post-launch, with around 120,900 new prescriptions (NRx), accounting for roughly 18% of all new prescriptions in the obesity category. Notably, Novo Nordisk’s internal data suggests actual prescriptions may exceed IQVIA-reported figures (e.g., 207,000 prescriptions for the week of April 17 vs. IQVIA’s 125,000), implying potential underestimation of real demand. Zepbound maintains dominance: In the injectable segment, Eli Lilly’s Zepbound continues to dominate. Over the past four weeks, low-dose new prescriptions for Zepbound—a proxy for new patient initiations—accounted for approximately 70% of the injectable market. Despite the launch of oral drugs, Zepbound’s total prescriptions grew by ~88% year-over-year, adding about 302,000 prescriptions per week and contributing roughly 56% of the overall growth in obesity market prescriptions. The report emphasizes that no negative impact on Zepbound’s new patient initiation rate has been observed following the launch of oral Wegovy. Foundayo off to a steady start: Eli Lilly’s own oral drug, Foundayo, recorded 16,698 total prescriptions in its sixth week, up from 10,248 the prior week. Although its ramp-up is slower than oral Wegovy’s—likely due to Wegovy’s earlier launch timing and stronger brand recognition—this performance aligns with expectations. Eli Lilly disclosed during its Q1 earnings call that over 20,000 patients have already used the drug, suggesting potential lag in IQVIA data capture.

Analysis framework

The firm employed high-frequency prescription data tracking, primarily relying on weekly Total Rx (TRx) and New Rx (NRx) data from IQVIA. The analytical logic hinges on decomposing 'new patient initiations' (proxied by low-dose NRx) and 'total prescription growth' to distinguish whether competition represents a zero-sum game (stealing share) or a positive-sum game (expanding the market). By comparing Zepbound’s new prescription trends before and after the launch of oral Wegovy, the report validates whether oral drugs are eroding the injectable base. Additionally, discrepancies between company-disclosed patient numbers and third-party data were used to assess data accuracy and potential upside revisions.

Methodology notes

• Industry/Sector Analysis FrameworkSupply-demand framework

  Analyzing whether new products substitute existing ones or create new demand by decomposing New Rx (NRx) and Total Rx (TRx).

  In the pharmaceutical industry, NRx represents new patient inflow, while TRx reflects overall treatment volume. If a competitor’s launch causes our NRx to decline, it indicates substitution; if our NRx remains stable while total TRx grows, it signals market expansion.

• Event Arbitrage & Behavioral FinanceExpectation Gap / Expectation Management

  Identifying expectation gaps caused by lags in third-party data (IQVIA) versus company guidance (>20k patients).

  When public data trails behind internal company disclosures, it often implies potential future data upward revisions. Investors should be mindful of such statistical discrepancies that may lead to short-term misjudgments.

Asset mapping & comparison

Structured mapping from thesis to named assets (strengths, weaknesses, peers, risks).

• Eli Lilly & Company (LLY.US)

  Beneficiary

  Strengths

  Zepbound maintains absolute dominance in the injectable market with strong new patient acquisition; Foundayo is off to a steady start, and market education from oral Wegovy creates positive spillover effects for orforglipron.

  Weaknesses

  Foundayo’s current prescription ramp-up is slower than Novo Nordisk’s oral Wegovy.

  Comparison

  Compared to Novo Nordisk, Eli Lilly shows stronger growth momentum in injectables (Zepbound +88% YoY) and has the potential to catch up in orals with upcoming products.

  Risks

  IQVIA data capture volatility may cause short-term distortions; intensifying oral drug competition could pressure long-term pricing power.

Key data

• Oral Wegovy Total Prescriptions (TRx)~143,000Week 19 post-launch; previous week: 137,300
• Zepbound Total Prescription YoY Growth~88%Adding ~302,000 prescriptions per week
• Zepbound New Patient Share~70%Share of low-dose new prescriptions in the injectable market over the past four weeks
• Foundayo Total Prescriptions (TRx)16,698Week 6 post-launch; previous week: 10,248
• Obesity Market Total Prescription YoY Growth~96%Four-week average as of May 15

Impact & implications

The report concludes that the successful launch of oral Wegovy is a net positive for the entire GLP-1 drug class, demonstrating the commercial viability and patient acceptance of oral formulations. For Eli Lilly, this not only fails to undermine Zepbound’s dominant position in injectables but also provides favorable market validation for its upcoming oral drug, orforglipron. This suggests Eli Lilly can leverage a 'injectable + oral' portfolio strategy to reach a broader patient base and further solidify its leadership in obesity therapeutics.

Risks

• IQVIA data capture issues: Since the week of April 24, Zepbound data capture has been problematic, leading to underestimation of vial and Kwikpen pen prescriptions.
• Statistical bias: IQVIA data may systematically underestimate actual prescription volumes; cross-validation with company guidance is necessary.

What to watch

• Upcoming launch progress and early prescription data for Eli Lilly’s oral drug orforglipron.
• Continued ramp-up of Foundayo prescriptions, particularly whether it can narrow the gap with oral Wegovy.
• Stability of Zepbound’s new patient initiation rate (low-dose NRx) amid oral drug competition.