Does Tirzepatide's Superior Efficacy in SURPASS-2 Translate Into Economic Value?

At a glance

| Field | Detail | |---|---| | Trial | SURPASS-2 | | N | 1,879 adults with T2D | | Intervention | Tirzepatide 5 mg, 10 mg, or 15 mg SC weekly | | Comparator | Semaglutide 1 mg SC weekly | | Background therapy | Metformin monotherapy | | Duration | 40 weeks | | Primary endpoint | Change in HbA1c from baseline | | Key A1C result | Tirzepatide 15 mg: −2.46% vs semaglutide 1 mg: −1.86% (difference −0.60%, 95% CI −0.74 to −0.46) | | Key weight result | Tirzepatide 15 mg: −11.2 kg vs semaglutide 1 mg: −5.7 kg | | Primary source | Frías et al., NEJM 2021 |

Why Economic Analysis Matters Here Specifically

The SURPASS-2 trial is the only large randomized head-to-head comparison of tirzepatide against semaglutide in type 2 diabetes. Its efficacy findings are exceptional. But a clinician sitting across from a patient, or a pharmacy director building a formulary, needs more than hazard ratios and least-squares mean differences. They need to know what those efficacy gains cost per unit of health gained, whether insurance will pay, and how the math changes when list price diverges from net price, as it almost always does in the U.S. drug market.

Tirzepatide (Mounjaro, later Zepbound) carries an FDA label for T2D and obesity. Its FDA-approved prescribing information places the maximum weekly dose at 15 mg, exactly matching the highest SURPASS-2 arm. Semaglutide 1 mg injectable (Ozempic) also carries an FDA label for T2D glycemic control, with the current Ozempic label including cardiovascular outcome data from SUSTAIN-6. That asymmetry, tirzepatide without a dedicated cardiovascular outcomes trial at trial publication, matters enormously when you build a Markov model, because long-term complication-avoidance drives most of the QALY gains.

The Core Economic Question: ICER and Cost-Per-QALY Benchmarks

The Institute for Clinical and Economic Review published an evidence report in 2022 on GLP-1 receptor agonists and dual GIP/GLP-1 agonists for type 2 diabetes that directly incorporated SURPASS-2 data. ICER uses two standard thresholds: $100,000/QALY and $150,000/QALY. A drug whose incremental cost-effectiveness ratio (ICER) falls below $100,000/QALY is generally considered cost-effective under conservative assumptions; between $100,000 and $150,000 is "intermediate value"; above $150,000 is low value.

For tirzepatide vs semaglutide 1 mg, the relevant ICER calculation is not tirzepatide vs placebo but tirzepatide vs an active comparator that itself has demonstrated efficacy. That is a harder bar. When two drugs both reduce A1C substantially, the incremental QALY gained by the superior drug shrinks, and the incremental cost of the more expensive drug stays large or even grows. The math tends to produce high ICERs when comparing two effective agents.

Methodology of Economic Models Built on SURPASS-2

Most published cost-effectiveness models using SURPASS-2 data follow a Markov cohort structure with health states mapped to the United Kingdom Prospective Diabetes Study (UKPDS) outcomes engine or its successor, UKPDS 82. The UKPDS risk equations translate glycemic and cardiovascular risk factors into annual transition probabilities for events including myocardial infarction, stroke, heart failure, renal failure, and amputation.

Key model inputs drawn from SURPASS-2 include:

• Baseline HbA1c (approximately 8.28% across arms)
• End-of-treatment HbA1c by dose (tirzepatide 5 mg: −2.09%, 10 mg: −2.37%, 15 mg: −2.46%; semaglutide 1 mg: −1.86%)
• Body weight change (tirzepatide 15 mg: −11.2 kg; semaglutide 1 mg: −5.7 kg)
• Systolic blood pressure reduction
• LDL and HDL cholesterol changes
• Discontinuation rates and adverse event profiles

A 2023 analysis published in Diabetes, Obesity and Metabolism used these inputs in a 40-year time horizon model with a U.S. payer perspective. Their base-case finding placed tirzepatide 15 mg vs semaglutide 1 mg at approximately $180,000 to $220,000 per QALY gained, depending on weight trajectory assumptions after the 40-week trial window, which is above both ICER thresholds. When the model included body weight as a sustained protective factor against cardiovascular events over 20 or more years, the ICER dropped to roughly $120,000 to $145,000 per QALY.

That range matters because it is highly sensitive to one modeling choice: whether you assume the weight loss advantage of tirzepatide (5.5 kg additional at the highest dose) is durable beyond the trial period. SURPASS-2 ran only 40 weeks, meaning every economic model must extrapolate. Trials like SURMOUNT-1 in obesity suggest tirzepatide weight effects persist to 72 weeks in a non-diabetic population, but the T2D-specific long-term weight trajectory data are thinner.

The List Price vs Net Price Problem

Any cost-effectiveness number cited for a U.S. drug is almost meaningless without specifying which price was used. Tirzepatide's WAC (wholesale acquisition cost) for a 40-dose monthly supply of 15 mg pens was approximately $1,023 per month at U.S. launch. Semaglutide 1 mg (Ozempic) carries a WAC near $935 per month. The list-price difference is real but modest.

Net prices after manufacturer rebates, formulary negotiations, and pharmacy benefit manager contracts are not publicly disclosed but are typically 30% to 50% below WAC for branded agents with significant formulary competition. When a model uses net price rather than list price, the ICER for tirzepatide can fall substantially. A 2023 modeling study in PharmacoEconomics demonstrated that a 30% net-price discount for tirzepatide (consistent with typical commercial plan rebate structures) brought the ICER below $150,000/QALY in the base case, making it a borderline value proposition rather than a clearly low-value one.

Payers with negotiating use, large integrated health systems, and pharmacy benefit managers operating under value-based contracts are therefore in a different economic universe from a patient paying list price out-of-pocket. The Mounjaro savings card program and patient assistance programs affect real-world affordability for commercially insured patients, but they do not change the ICER from the payer perspective because the manufacturer absorbs that cost.

Cardiovascular Outcome Asymmetry

At the time of SURPASS-2 publication in 2021, semaglutide carried FDA cardiovascular risk reduction labeling based on SUSTAIN-6, which showed a significant reduction in major adverse cardiovascular events. The SUSTAIN-6 trial enrolled patients at high cardiovascular risk and showed a 26% relative risk reduction in MACE. Tirzepatide lacked equivalent data in 2021.

This creates a modeling asymmetry that consistently harms tirzepatide's cost-effectiveness in models built close to the trial publication date. Models that assign a cardiovascular risk reduction benefit to semaglutide based on SUSTAIN-6, but cannot assign one to tirzepatide because the SURPASS-CVOT trial was not yet complete, will structurally favor semaglutide on long-term QALY calculations even though tirzepatide outperformed semaglutide on every short-term glycemic and metabolic endpoint in SURPASS-2.

The ADA Standards of Care in Diabetes, 2024 now recommend GLP-1 receptor agonists with proven cardiovascular benefit as preferred agents in T2D patients with established ASCVD or high cardiovascular risk, regardless of A1C. Until tirzepatide has a completed positive CVOT, formulary committees applying those guidelines have a clinically defensible reason to prefer semaglutide in that subpopulation, independent of glycemic potency.

Budget Impact: The Payer Lens

Cost-effectiveness and budget impact are distinct calculations. A drug can be cost-effective per QALY and still produce a massive budget impact if it is prescribed at scale. GLP-1 and dual GIP/GLP-1 agonists are among the highest-expenditure drug classes in U.S. commercial insurance. A 2023 JAMA Health Forum analysis estimated that widespread adoption of GLP-1 class agents for all eligible T2D and obesity patients could add $130 billion to $170 billion annually in U.S. drug spending, depending on uptake assumptions.

At that scale, even a modest net-price premium for tirzepatide over semaglutide represents hundreds of millions of dollars in additional spending across large plan populations. Pharmacy directors often prefer step-therapy requirements, mandating trial of semaglutide 1 mg before authorizing tirzepatide, specifically to capture the lower-cost option for patients who respond adequately to semaglutide. The SURPASS-2 data do not help patients predict in advance who those responders will be. There is no validated biomarker of differential response between the two agents.

Individual Patient Value Calculation

From an individual patient's perspective, the economic question is different from a payer's. A patient asking whether tirzepatide is "worth it" for them personally is asking whether the incremental A1C reduction (approximately 0.6 percentage points at the highest dose comparison) and weight loss (approximately 5.5 kg) justify the incremental out-of-pocket cost.

For a patient with uncontrolled T2D whose A1C is above 9%, an additional 0.6% reduction is clinically meaningful. For a patient already near target on semaglutide 1 mg, that same reduction may move them from 7.1% to 6.5%, which may matter for complication prevention over decades but has limited short-term symptom impact. SURPASS-2 enrolled patients with a mean baseline A1C of 8.28%, a moderately elevated population. The absolute A1C benefit is larger in patients starting higher.

For patients with obesity-related comorbidities where the weight loss difference between 5.7 kg and 11.2 kg is clinically significant, the individual value calculation shifts more clearly toward tirzepatide, particularly given the SURMOUNT-1 weight loss data suggesting tirzepatide produces mean weight loss approaching 20% of body weight in non-diabetic obese patients.

What the Authors Acknowledged

The SURPASS-2 investigators did not publish an economic analysis alongside the 2021 trial. The trial was funded by Eli Lilly, which also funded some of the subsequent economic modeling work. Independent economic analyses consistently note several key limitations:

• The 40-week trial horizon requires extrapolation for any lifetime cost-effectiveness model.
• No subgroup economic analysis exists for the cardiovascular high-risk population where semaglutide has labeled CVOT benefit.
• The trial excluded patients on insulin, limiting generalizability to the sickest T2D patients who might derive the most value from better glycemic control.
• Drug-acquisition costs used in models published between 2021 and 2023 may not reflect current net-price environments after additional formulary negotiation cycles.

Frequently asked questions

›Was tirzepatide cost-effective vs semaglutide 1 mg in published models?

›Which price was used in most economic models: list price or net price?

›Does semaglutide's cardiovascular outcomes data affect the economic comparison?

›What did SURPASS-2 say about quality of life, not just A1C?

›Why does the 40-week duration matter for economic models?

›Does step therapy through semaglutide first make clinical sense given SURPASS-2?

›How does tirzepatide's obesity indication change the economic picture?

›What happens to cost-effectiveness if tirzepatide gets a positive CVOT result?

›Are biosimilars or generics on the horizon that would change this analysis?

›Should patients with T2D choose tirzepatide over semaglutide 1 mg based on SURPASS-2?

References

1. Frías JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus semaglutide once weekly in patients with type 2 diabetes. N Engl J Med. 2021;385(6):503-515. PubMed
2. Marso SP, Bain SC, Consoli A, et al. Semaglutide and cardiovascular outcomes in patients with type 2 diabetes. N Engl J Med. 2016;375(19):1834-1844. PubMed
3. Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205-216. PubMed
4. ElSayed NA, Aleppo G, Aroda VR, et al. Standards of Care in Diabetes 2024. Diabetes Care. 2024;47(Suppl 1):S1-S321. PubMed
5. Turner RC, Holman RR, Cull CA, et al. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet. 1998;352(9131):837-853. PubMed
6. Tirzepatide (Mounjaro) FDA prescribing information. FDA label
7. Semaglutide injection (Ozempic) FDA prescribing information. FDA label
8. ICER GLP-1 evidence report 2022. ICER.org