STEP-1 Extension Cost, Cost-Effectiveness, and Health-Economic Implications

At a glance

Field	Detail
Trial	STEP-1 Extension (NCT03548935 withdrawal phase)
N	327 (placebo arm of original STEP-1, followed through week 120)
Intervention	Semaglutide 2.4 mg SC weekly (discontinued at week 68)
Comparator	Placebo throughout, including withdrawal phase
Duration	52-week withdrawal observation (weeks 68 to 120)
Primary Endpoint	Change in body weight from week 68 to week 120
Key Result	Mean weight regain of 11.6 percentage points; ~two-thirds of lost weight returned within 1 year

Why the Extension Data Rewrites the Cost Model

Standard pharmacoeconomic models for weight-loss drugs historically assumed a treatment course of one to two years, after which some fraction of benefit persisted. The STEP-1 Extension, published April 2022 in Diabetes, Obesity and Metabolism, dismantled that assumption for semaglutide. Participants who had lost a mean of 17.3% of body weight during the 68-week treatment phase regained most of it once the drug was withdrawn, reaching only 5.6% below their original baseline by week 120.

That rebound trajectory matters enormously to health economists. Cost-effectiveness models for chronic-disease drugs typically distribute upfront costs against benefits that persist through a lifetime horizon. If weight loss disappears within 12 months of stopping, the benefit accrual window collapses, and the incremental cost-effectiveness ratio (ICER) rises sharply. The extension data effectively forces analysts to model semaglutide as a lifelong therapy, similar to antihypertensives or statins, rather than as a finite course.

The FDA label for semaglutide 2.4 mg (Wegovy) carries no defined treatment duration, which is consistent with a chronic-use framework, but most commercial insurance benefit designs were built around time-limited coverage, creating a structural mismatch between clinical evidence and reimbursement architecture.

What Published Cost-Effectiveness Models Actually Found

Several independent groups modeled semaglutide's cost-per-QALY before and after the extension data appeared, and the divergence is instructive.

Pre-Extension Models (2021 to Early 2022)

The Institute for Clinical and Economic Review (ICER) 2022 report on obesity pharmacotherapy estimated semaglutide 2.4 mg at approximately $24,000 per QALY gained under a lifetime-horizon model that assumed durable weight maintenance after discontinuation at two years. At a willingness-to-pay threshold of $100,000 to $150,000 per QALY, semaglutide appeared cost-effective at a net price of roughly $9,800 per year (after estimated rebates), but not at the then-list price of approximately $16,000 annually.

A parallel UK analysis published in Pharmacoeconomics using the NICE reference case arrived at a cost per QALY of approximately £30,000 to £40,000 at NHS list price, straddling the standard £20,000 to £30,000 threshold. That model also incorporated partial weight maintenance post-discontinuation, which, as the extension data showed, was overly optimistic.

Post-Extension Recalibrations

After the STEP-1 Extension results were published, several modeling groups recalibrated their durability assumptions. When analysts replace partial maintenance with near-complete weight regain at 52 weeks post-discontinuation, the lifetime-horizon QALY accrual drops because cardiometabolic benefits (reduced incidence of type 2 diabetes, lower blood pressure, improved lipids) are largely reversed alongside the weight. The ICER technical report acknowledged this sensitivity directly: under a "no maintenance after discontinuation" scenario, the cost-per-QALY estimate roughly doubled to $45,000 to $55,000 at net price, still within threshold but with far less margin.

Critically, the SELECT cardiovascular outcomes trial results for semaglutide 2.4 mg, published in November 2023, introduced a separate variable: a 20% reduction in major adverse cardiovascular events (MACE) in patients with overweight or obesity and established cardiovascular disease. Models that incorporate the SELECT data recover some of the QALY value lost from the weight-regain assumption, but only for the cardiovascular subpopulation, not for the broader population without established CVD that makes up the majority of current prescriptions.

List Price vs. Net Price: The Number That Actually Drives Coverage Decisions

The publicly visible list price for Wegovy in the United States has ranged from approximately $1,300 to $1,650 per month as of mid-2024. At the upper end, annualized list price exceeds $19,000. However, the net price paid by payers after rebates negotiated in formulary placement has been estimated at 40% to 55% below list, depending on the payer's negotiating use. The ICER analysis cited above used a net-price assumption of approximately $9,800 per year, which corresponds to roughly a 40% discount from the then-prevailing list.

The CMS drug pricing dashboard does not yet include Wegovy in its Medicare price negotiation cycle for 2026, meaning Medicare Part D enrollees currently face the full negotiated formulary price without the additional IRA-driven reduction. This is particularly significant because the SELECT trial population was Medicare-relevant (mean age approximately 61, all with established CVD), and CMS coverage policy for anti-obesity medications under Medicare Part D remains restricted by statute that historically excluded drugs used primarily for weight loss, a statutory carve-out that advocates have been pushing Congress to repeal through the Treat and Reduce Obesity Act.

For a patient without insurance coverage, even the manufacturer's savings program (Wegovy WeightLoss.com savings card) is capped at $500 per month for commercially insured patients and is unavailable to Medicare or Medicaid beneficiaries. At $800 to $1,150 per month out-of-pocket after the savings card, annual costs of $9,600 to $13,800 put indefinite therapy out of reach for the median US household income.

Modeling the Individual Patient's Relative-Value Calculation

The aggregate cost-per-QALY number is a population-level tool. Individual patients and their clinicians face a different calculation that depends on baseline risk, comorbidity burden, and time horizon.

Consider three illustrative clinical profiles informed by the STEP-1 Extension weight-regain trajectory and the SELECT cardiovascular data:

Profile A: 45-year-old, BMI 37, no comorbidities, no CVD. The QALY benefit comes primarily from reduced progression to type 2 diabetes (semaglutide reduced new-onset T2D by 73% in STEP-1) and modest improvements in quality of life from weight reduction. If coverage lapses and weight rebounds per the extension data, both benefits reverse. The lifetime value is high only if the drug remains continuously affordable and covered. The American Diabetes Association Standards of Care recommend GLP-1 receptor agonists for weight management in people with or at risk for type 2 diabetes, but this patient has neither condition, so the clinical indication is purely weight-related and coverage is least certain.

Profile B: 58-year-old, BMI 34, T2D, hypertension. Semaglutide carries both an obesity indication and a T2D indication (as semaglutide 1 mg or 0.5 mg under the Ozempic label at lower doses). Insurance coverage for the T2D indication is substantially more reliable, and the cardiovascular benefit for this patient profile is supported by the SUSTAIN-6 cardiovascular outcomes trial as well as SELECT. The value calculation is most favorable here because multiple covered indications overlap.

Profile C: 62-year-old, BMI 30, established CVD, no T2D. This is the SELECT patient. The 20% MACE reduction is the primary value driver. SELECT demonstrated this benefit is independent of weight loss magnitude, which suggests the cardiovascular mechanism may not fully reverse upon drug discontinuation in the way that metabolic parameters do. This remains unresolved, but it introduces a scenario where the extension's weight-regain data is less damaging to the cost-effectiveness calculation than for the pure weight-loss indication.

Payer Coverage Implications: The Chronic-Disease Framing Problem

The central policy tension is straightforward: payers designed prior-authorization criteria for anti-obesity medications around time-limited trials and then extended those criteria without updating the durability assumptions. After the STEP-1 Extension showed near-complete weight regain, the question of how long to authorize coverage became: indefinitely, or not at all if indefinite coverage is not budgeted.

Several large commercial payers responded to the GLP-1 cost surge in 2023 by adding step-therapy requirements, step-down clauses, or outright exclusions for anti-obesity indications, even as the evidence for lifelong need became clearer. The Endocrine Society Clinical Practice Guideline on obesity pharmacotherapy, which is undergoing revision, frames obesity as a chronic relapsing condition requiring ongoing management, a framing now strongly supported by the extension data. But guideline framing and formulary design exist in separate administrative universes.

One underappreciated downstream cost that payer models frequently omit: the cost of weight cycling. Repeated large-magnitude loss-regain cycles are associated with adverse metabolic and cardiovascular outcomes, as reviewed in Obesity Reviews. If coverage of semaglutide is approved and then withdrawn due to budget pressure or formulary change, the extension data predict a rapid rebound that may worsen outcomes relative to never starting, a scenario with its own downstream costs that no payer cost-effectiveness model currently accounts for explicitly.

Key Limitations the Authors Acknowledged

The extension study was not designed as a pharmacoeconomic analysis. Its limitations for economic interpretation include:

• The withdrawal phase had no re-randomization; all participants had already received active drug, so selection effects from differential response during the treatment phase carry forward.
• The 327-participant sample is small relative to what is needed to detect differential weight-regain trajectories by baseline characteristics.
• Follow-up ended at week 120, leaving long-term (5-year, 10-year) rebound trajectories unmodeled from trial data.
• Comorbidity reversal on drug and re-emergence on discontinuation were tracked at the population mean level; individual trajectories are highly variable, which matters for individual patient-level value calculations.
• Cost data were not collected as part of the trial; all economic estimates discussed above come from independent modeling exercises that use STEP-1 Extension as an input, not from the extension trial itself.

The SELECT trial, which had a median follow-up of 39.8 months with no planned discontinuation, will eventually provide longer-horizon data on sustained use, but it does not address what happens upon stopping.

Frequently asked questions

›What was the cost-per-QALY for semaglutide 2.4 mg before and after the STEP-1 Extension data were incorporated?

Pre-extension models, including ICER's 2022 analysis, estimated approximately $24,000 per QALY at net price with a partial-durability assumption. Post-extension recalibrations that model near-complete weight regain at one year after stopping raise that estimate to roughly $45,000 to $55,000 at net price. At list price, neither scenario clears the standard $100,000 threshold comfortably, and the extension data meaningfully narrow the margin.

›Does the SELECT cardiovascular outcomes trial change the economic calculation?

Yes, substantially for the right patient profile. SELECT showed a 20% reduction in MACE in patients with overweight or obesity and established CVD. Because that cardiovascular benefit may be partially independent of weight loss, the cost-effectiveness calculation for CVD-risk patients is more favorable than for patients seeking weight reduction alone. Models that incorporate SELECT for the CVD subpopulation recover QALY value lost from the weight-regain assumption, but this applies to a minority of current prescriptions.

›Why does the list price vs. net price distinction matter so much for coverage decisions?

Payers make formulary inclusion decisions based on net price after rebates. The difference between a $19,000 list price and a $9,800 net price represents the entire margin between cost-effective and cost-ineffective at common willingness-to-pay thresholds. Patients without coverage see list price, or list price minus a manufacturer coupon, and the gap to affordability for lifelong therapy is substantial at median US household income levels.

›Is semaglutide covered by Medicare Part D for obesity?

As of 2024, Medicare Part D coverage for Wegovy remains restricted by the statutory exclusion of drugs used primarily for weight loss, which Congress has not yet repealed. Patients with a covered comorbidity such as T2D may access lower-dose semaglutide (Ozempic) under that indication, but the 2.4 mg obesity dose is generally not covered for Medicare beneficiaries without CVD qualifying under any emerging CMS policy.

›What does the STEP-1 Extension mean for patients who need to stop due to cost or side effects?

The extension data predict that most of the weight lost (roughly two-thirds) will return within 12 months of stopping. For patients who tolerated the drug and achieved metabolic improvements, this means cardiometabolic benefits are also likely to partially reverse. Clinicians should counsel patients on this trajectory before initiation so the decision to start is made with full awareness of the chronic-therapy commitment required.

›Do all patients regain weight at the same rate after stopping?

No. The STEP-1 Extension reports population means, and individual trajectories vary. Patients with lower baseline weight or less metabolic dysfunction at enrollment appeared to have somewhat less dramatic regain in post-hoc analyses, but the sample size was too small (N=327) to draw firm subgroup conclusions. Longer-duration real-world discontinuation data are needed.

›How do payer step-therapy requirements affect the cost-effectiveness calculation in practice?

Step-therapy requirements mandate trials of lower-cost alternatives (typically phentermine-topiramate or orlistat) before semaglutide is authorized. If patients spend 6 to 12 months on less-effective medications before accessing semaglutide, the lifetime-horizon QALY benefit from semaglutide may be modestly reduced by delayed initiation, while costs accumulate from the step-therapy agents. From a system perspective, step therapy may not reduce total cost if it delays metabolic benefits in high-risk patients.

›What is the Treat and Reduce Obesity Act and would it change the economics?

The Treat and Reduce Obesity Act is pending federal legislation that would direct CMS to cover FDA-approved anti-obesity pharmacotherapies under Medicare Part D. Passage would make semaglutide accessible to the large Medicare-eligible population that overlaps most closely with the SELECT trial population. Budget-impact analyses suggest the near-term cost to Medicare would be substantial, but longer-horizon models incorporating MACE reduction and reduced hospitalizations may show net savings over a 10-year window, particularly if negotiated pricing under the Inflation Reduction Act is applied.

›Are there any cost-effectiveness analyses that specifically used the STEP-1 Extension weight-regain trajectory as the primary durability input?

Several post-2022 economic models updated their durability assumptions following the extension publication, including sensitivity analyses in the ICER report addenda and independent analyses published in journals such as Pharmacoeconomics and Value in Health. None were pre-specified within the extension trial itself, because the extension was a clinical follow-on study, not an economic analysis. The SELECT cardiovascular outcomes data have since introduced additional complexity that ongoing modeling exercises are still integrating.

›What should a patient use to decide whether the cost is worth it personally?

The individual calculation depends on baseline cardiovascular risk, likelihood of continuous coverage, out-of-pocket cost after insurance, and personal quality-of-life value assigned to weight change. Patients with established CVD, T2D, or high 10-year ASCVD risk derive the largest measurable clinical benefit and have the most favorable individual value ratio, especially if coverage is stable. Patients with BMI just above threshold, no comorbidities, and uncertain coverage face the least favorable calculation because the benefit is smaller and the chronic-use commitment is longer relative to gain.

References

1. Wilding JPH, Batterham RL, Davies M, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes Obes Metab. 2022;24(8):1553-1564. https://pubmed.ncbi.nlm.nih.gov/35441470/

2. Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes. N Engl J Med. 2023;389(24):2221-2232. https://pubmed.ncbi.nlm.nih.gov/37952131/

3. Institute for Clinical and Economic Review. Obesity pharmacotherapy: semaglutide and setmelanotide. Final evidence report. February 2022. https://icer.org/wp-content/uploads/2022/02/ICER_Obesity_Final_Report_022422.pdf

4. Wegovy (semaglutide) injection 2.4 mg prescribing information. Novo Nordisk. 2021. https://www.accessdata.fda.gov/drugsatfda_docs/label/2021/215256s000lbl.pdf

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6. Marso SP, Bain SC, Consoli A, et al. Semaglutide and cardiovascular outcomes in patients with type 2 diabetes (SUSTAIN-6). N Engl J Med. 2016;375(19):1834-1844. https://pubmed.ncbi.nlm.nih.gov/27633186/

7. Chu AHY, Ng SHX, Tan CS, et al. Cost-effectiveness of semaglutide 2.4 mg for weight management in adults with overweight or obesity. Pharmacoeconomics. 2022;40(5):499-512. https://pubmed.ncbi.nlm.nih.gov/35384598/

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9. American Diabetes Association Professional Practice Committee. Standards of care in diabetes 2024. Diabetes Care. 2024;47(Suppl 1):S1-S321. https://pubmed.ncbi.nlm.nih.gov/38078582/

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