STEP-5 Cost, Cost-Effectiveness, and Health-Economic Implications

At a glance

Why Economic Analysis of STEP-5 Is Distinct From Other STEP Trials

Most cost-effectiveness analyses of semaglutide 2.4 mg have used data from STEP-1, the largest of the four key trials. STEP-5 is smaller, enrolling 304 adults, but it provides something STEP-1 cannot: a full two-year placebo-controlled weight trajectory. That matters for economic modeling because obesity pharmacotherapy is not a one-time intervention. Cost-per-QALY estimates depend critically on whether weight loss is maintained over time or attenuates after the first year.

The STEP-5 primary publication in Nature Medicine showed that at week 104, participants randomized to semaglutide had lost 15.2% of body weight versus 2.6% for placebo. The weight loss trajectory remained stable from roughly week 60 onward, with no meaningful regain through week 104 in the active treatment arm. That plateau, rather than a decline, is the single most important input for any economic model that projects health outcomes beyond the trial window.

When analysts feed an attenuating weight-loss curve into a Markov or discrete-event simulation, costs per QALY rise substantially because downstream benefits (reduced incidence of type 2 diabetes, cardiovascular events, and sleep apnea-related morbidity) are proportional to maintained weight reduction. STEP-5's durable trajectory therefore produces more favorable cost-effectiveness ratios than models forced to assume gradual regain after 12 months.

How Economic Models Are Built From STEP-5 Data

The Modeling Framework

Health-technology assessment bodies including ICER (Institute for Clinical and Economic Review) use microsimulation or Markov state-transition models to translate weight change into lifetime QALYs. The standard approach maps percentage weight loss to risk reductions for incident type 2 diabetes (via the Diabetes Prevention Program equation), major adverse cardiovascular events, hypertension, dyslipidemia, and obesity-related cancers. Each avoided event contributes to both QALY gains and cost offsets.

The STEP-5 dataset inputs to these models include:

• Baseline BMI (mean 38.5 kg/m² in the trial)
• Absolute weight loss at 104 weeks (mean 15.2% or approximately 15.6 kg from a mean baseline of approximately 103 kg)
• Proportion of participants achieving ≥5%, ≥10%, and ≥15% weight loss thresholds
• Discontinuation rate (approximately 13.5% in the semaglutide arm over 104 weeks)
• Adverse-event rates that affect quality-of-life utilities (predominantly gastrointestinal)

ICER's Cost-Per-QALY Range

In its 2022 evidence report on GLP-1 and GIP/GLP-1 agonists for obesity, ICER modeled semaglutide 2.4 mg using a blended dataset including STEP-1 and STEP-5 trajectory data. At the US wholesale acquisition cost (WAC) of approximately $1,349 per month (roughly $16,200 per year), the estimated incremental cost-effectiveness ratio ranged from $130,000 to $180,000 per QALY gained in adults with BMI ≥30. For the subgroup with BMI ≥30 plus established cardiovascular disease or type 2 diabetes, the estimate improved to approximately $110,000 to $150,000 per QALY because avoided downstream costs are higher in that population.

These figures exceed the conventional US threshold of $100,000 to $150,000 per QALY, which means semaglutide at list price sits at the boundary of cost-effectiveness acceptability by standard benchmarks. The ICER report estimated that a price reduction to approximately $7,500 to $9,800 per year (net of rebates) would bring the drug within a $150,000/QALY threshold for adults with at least one comorbidity.

Sources: ICER 2022 obesity evidence report; STEP-5 primary trial.

List Price vs Net Price: The Gap That Changes Everything

Published cost-effectiveness analyses almost always model WAC because net prices (after rebates paid to pharmacy benefit managers and insurers) are confidential. The gap between WAC and net price for branded GLP-1 agonists has historically been 40% to 60% in commercial markets, though the precise figures for Wegovy (semaglutide 2.4 mg) remain undisclosed.

Novo Nordisk's FDA-approved label for Wegovy positions the drug for adults with initial BMI ≥30 kg/m² or ≥27 kg/m² with at least one weight-related comorbidity. If commercial rebates for this indication approach those seen for semaglutide 1.0 mg (Ozempic, approved for type 2 diabetes), net annual costs could fall to $8,000 to $10,000 in broad commercial formularies, substantially shifting cost-effectiveness calculations.

For the Medicare population specifically, the Inflation Reduction Act created new negotiation authority for selected drugs, though weight-loss-only indications have faced separate coverage restrictions under traditional Medicare Part D. The SELECT trial, which demonstrated a 20% reduction in major adverse cardiovascular events with semaglutide 2.4 mg in adults with obesity and established cardiovascular disease, has added pressure on CMS to broaden coverage, since a cardiovascular indication changes the payer calculus entirely.

Cost Per Kilogram Lost: A Patient-Facing Metric

Cost per QALY is a population-level construct that individual patients rarely find intuitive. A more accessible metric is cost per kilogram of body weight lost over the treatment period.

Using STEP-5 data directly: the mean weight loss in the semaglutide arm was approximately 15.6 kg over 104 weeks. At WAC of $16,200 per year, the two-year drug cost is $32,400. Cost per kilogram lost (drug cost only, ignoring injection supplies and monitoring visits) is therefore approximately $2,077 per kg.

For comparison, bariatric surgery (Roux-en-Y gastric bypass) produces approximately 25 to 35 kg of sustained weight loss at a one-time procedural cost of roughly $20,000 to $35,000 in US centers, yielding a cost-per-kilogram-lost in the range of $600 to $1,200. However, surgery carries procedural risk, requires lifelong nutritional monitoring, and is not appropriate for all patients. The pharmacotherapy alternative requires indefinite continuation to maintain weight loss, as demonstrated by the STEP-1 withdrawal extension, where participants who discontinued semaglutide regained approximately two-thirds of lost weight within one year.

This regain risk, documented in post-STEP-1 extension data published in Diabetes, Obesity and Metabolism, means that the effective cost of pharmacotherapy is ongoing rather than bounded. Over a 10-year horizon at net price ($9,000/year), total drug expenditure reaches $90,000 before accounting for rebates, co-pay assistance, or any potential generic entry.

Payer Coverage Realities and Formulary Design

As of mid-2024, coverage of semaglutide 2.4 mg for obesity without a specific cardiovascular or diabetic indication remains highly variable across US commercial payers. Several large employers and state Medicaid programs have restricted or excluded coverage due to budget impact concerns. A Health Affairs analysis published in 2023 estimated that universal coverage of GLP-1 agonists at list price for all eligible US adults could add $145 billion to $265 billion annually to national drug expenditures, a figure that explains formulary resistance independent of per-patient cost-effectiveness.

The practical result for patients is a tiered system where access correlates heavily with insurance type and employer benefit design. Patients with employer-sponsored plans that include obesity pharmacotherapy coverage, patients who qualify for Novo Nordisk's patient assistance program, and those enrolled in clinical programs with outcomes-based contracts face meaningfully different effective costs than patients paying out of pocket.

Criticisms of Existing Economic Models

Several methodological limitations affect all published economic analyses that draw on STEP-5:

Extrapolation uncertainty. STEP-5 provides 104 weeks of data. Most cost-effectiveness models project outcomes over 10, 20, or lifetime horizons. Weight-loss maintenance beyond two years without a placebo-controlled comparator is assumed rather than directly observed, though real-world registry data from LEADER and other long-term GLP-1 studies provide partial support for durability assumptions.

Utility weights. The quality-of-life gains assigned to weight reduction vary substantially across models. If the model uses utilities derived from obese populations with significant comorbidities, QALY gains are higher. STEP-5's population had a mean BMI of 38.5 with relatively lower rates of established diabetes than STEP-2, which could mean baseline utility was higher and incremental QALY gain from weight loss is smaller than in more metabolically compromised cohorts.

Adverse-event costs. Gastrointestinal adverse events (nausea in approximately 44% of semaglutide participants in STEP-5) are frequently underweighted in published models, affecting both cost and disutility estimates.

Discontinuation modeling. Real-world discontinuation rates exceed trial rates substantially. A 2024 analysis of commercial claims data found 12-month persistence rates of approximately 30% for GLP-1 agonists prescribed for obesity. Models using trial-based discontinuation rates will overestimate long-term effectiveness and underestimate effective cost per outcome.

Frequently asked questions

›What was the actual cost-per-QALY estimate derived from STEP-5 data?

No single published analysis uses STEP-5 in isolation. ICER's 2022 obesity report, which incorporated STEP-5 trajectory data alongside STEP-1, estimated incremental cost-effectiveness ratios between $130,000 and $180,000 per QALY at US list price, depending on the patient subgroup modeled. At negotiated net prices of approximately $7,500 to $9,800 per year, that range falls below the $150,000 per QALY threshold for adults with at least one cardiometabolic comorbidity.

›Why does STEP-5 produce better economic modeling inputs than STEP-1?

STEP-5 ran for 104 weeks with a placebo comparator, providing a full two-year weight trajectory. STEP-1 was 68 weeks. Economic models that project lifetime health benefits depend heavily on whether weight loss is maintained. STEP-5's stable plateau after week 60 allows analysts to use an optimistic but defensible maintenance assumption, which lowers projected cost per QALY compared to models that assume gradual regain.

›Does Medicare cover semaglutide 2.4 mg for weight loss?

Traditional Medicare Part D historically excluded drugs approved solely for weight management under a statutory exclusion. The SELECT trial's cardiovascular outcomes data has prompted ongoing policy discussion about expanding Medicare coverage, but as of mid-2024, coverage for weight-loss-only indications remains restricted. Patients with both obesity and established cardiovascular disease may have a pathway under emerging coverage policies tied to the SELECT results.

›What is the list price of Wegovy and how does it compare to net price?

The US wholesale acquisition cost for Wegovy is approximately $1,349 per month, or roughly $16,200 annually. Net prices after rebates are not publicly disclosed but are estimated to be 40% to 60% lower in commercial formularies where the drug is covered, placing effective annual costs potentially in the $7,000 to $9,700 range. This gap is critical because all published academic cost-effectiveness analyses use WAC, making them less favorable than what insurers may actually model internally.

›What happens to the cost-effectiveness calculation if a patient stops taking semaglutide?

Discontinuation significantly worsens cost-effectiveness. Data from the STEP-1 withdrawal extension study, published in Diabetes, Obesity and Metabolism, showed that participants who stopped semaglutide regained approximately two-thirds of their lost weight within 52 weeks. A patient who achieves 15% weight loss over two years but then discontinues captures only a fraction of the projected lifetime QALY benefit, while having incurred the full two-year drug cost. Models that account for real-world discontinuation rates (approximately 30% at 12 months by claims data) produce substantially higher cost-per-QALY estimates.

›How does the cost-effectiveness of semaglutide compare to bariatric surgery?

At list price, bariatric surgery (Roux-en-Y gastric bypass) is generally considered cost-effective at a threshold of $50,000 to $100,000 per QALY, in part because weight loss is larger and the cost is bounded at one procedure plus follow-up care. Semaglutide at list price exceeds most surgery benchmarks on a cost-per-QALY basis and on cost-per-kilogram-lost over a 10-year horizon. At net price, the comparison narrows considerably, and pharmacotherapy has advantages in procedural risk avoidance and broader eligibility.

›What comorbidities most improve the cost-effectiveness of semaglutide in STEP-5-based models?

Established cardiovascular disease and pre-diabetes or type 2 diabetes most strongly improve cost-effectiveness ratios. Patients in these subgroups have higher baseline event rates, so a given reduction in cardiovascular or metabolic risk translates to a larger absolute reduction in costly events, increasing QALY gains and cost offsets. STEP-5's population was not restricted to these subgroups, but scenario analyses stratifying by baseline comorbidity consistently show more favorable ratios in higher-risk patients.

›Have any analyses looked at cost-effectiveness specific to the populations enrolled in STEP-5?

STEP-5 enrolled adults without type 2 diabetes, with BMI ≥30 or ≥27 with comorbidities, and without prior major cardiovascular events (unlike SELECT). This population is metabolically lower risk than STEP-2 (diabetes) or SELECT (established CVD) cohorts. Cost-effectiveness in this group is less favorable than in higher-risk populations because downstream event-cost offsets are smaller, though long-term diabetes prevention value is an important offsetting factor given that STEP-5's durable weight loss is associated with meaningful reductions in diabetes incidence risk.

›What did STEP-5 authors specifically acknowledge as limitations affecting economic interpretation?

The STEP-5 publication acknowledged a relatively small sample size (304 participants), which limits subgroup precision. The authors also noted that all participants received lifestyle intervention, meaning real-world effectiveness (without intensive counseling support) may be lower than trial results, further affecting cost-effectiveness projections. The trial did not include quality-of-life instruments that would directly generate utility weights, requiring analysts to import utilities from external sources.

›What is the practical takeaway for a patient trying to decide if semaglutide is worth the cost?

At out-of-pocket list price, the two-year drug cost from STEP-5's trial period is approximately $32,400 for an average weight loss of 15.6 kg. Whether that expenditure represents good individual value depends on a patient's baseline metabolic risk, the presence of comorbidities that weight loss would meaningfully improve, availability of insurance coverage, and whether they can maintain the lifestyle changes that amplify drug efficacy. For patients with insurance coverage that brings net cost below $10,000 per year and who have obesity-related comorbidities, the individual value calculation is substantially more favorable than the list-price QALY analysis suggests.

References

1. Garvey WT, Batterham RL, Bhatta M, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nature Medicine. 2022;28(10):2083-2091. https://pubmed.ncbi.nlm.nih.gov/36216945/

2. Institute for Clinical and Economic Review. Overweight and Obesity: Effectiveness and Value of Pharmacologic Treatments. ICER Evidence Report. 2022. https://icer.org/assessment/obesity-2022/

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

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

5. Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes. New England Journal of Medicine. 2023;389(24):2221-2232. https://pubmed.ncbi.nlm.nih.gov/37952131/

6. Dieleman JL, Cao J, Chapin A, et al. US health care spending by payer and health condition, 1996-2016. JAMA. 2020;323(9):863-884. https://pubmed.ncbi.nlm.nih.gov/32125369/