DraftWashington Office of the Insurance CommissionerPolicy N/A

Obesity Treatment Analysis — Modeling & Coverage Criteria (GLP-1 uptake, effectiveness, persistence, cost offsets)

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Advisory-group feedback on a draft Milliman Obesity Treatment Analysis report focused on projected GLP-1 uptake, effectiveness, persistence, and healthcare cost offsets; intended for Washington OIC staff, advisory members, and stakeholders informing the final report and potential coverage/mandate decisions.

Policy Summary

PayerWashington Office of the Insurance Commissioner

PolicyObesity Treatment Analysis — Modeling & Coverage Criteria

Policy CodePolicy N/A

Change TypeAdvisory recommendations to modeling and analytic assumptions

Effective DateN/A

Next Review DateN/A

Key ActionExclude enrollees with a type 2 diabetes diagnosis or any antidiabetic pharmacy claim from incremental obesity-GLP-1 uptake estimates.

SourceLink

POLICY UPDATE CHANGES

Exclude diabetes from obesity-GLP-1 incremental uptake

Agent-specific effectiveness modeling

Transparency and calculation disclosure

89%share of projected cost increase attributed to GLP-1s

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DraftWashington Office of the Insurance CommissionerPolicy N/A

Obesity Treatment Analysis — Modeling & Coverage Criteria (GLP-1 uptake, effectiveness, persistence, cost offsets)

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Policy Summary

PayerWashington Office of the Insurance Commissioner

PolicyObesity Treatment Analysis — Modeling & Coverage Criteria

Policy CodePolicy N/A

Change TypeAdvisory recommendations to modeling and analytic assumptions

Effective DateN/A

Next Review DateN/A

Key ActionExclude enrollees with a type 2 diabetes diagnosis or any antidiabetic pharmacy claim from incremental obesity-GLP-1 uptake estimates.

SourceLink

POLICY UPDATE CHANGES

Exclude diabetes from obesity-GLP-1 incremental uptake

Agent-specific effectiveness modeling

Transparency and calculation disclosure

89%share of projected cost increase attributed to GLP-1s

Modeling & Analytic Coverage Criteria

Modeling and analytic criteria

Recommended analytic criteria to produce valid estimates

Population definition: Exclude enrollees with a type 2 diabetes diagnosis or any antidiabetic pharmacy claim from the obesity-incremental GLP-1 uptake; consider excluding forecasted percentages who will receive bariatric surgery or GLP-1 for other covered indications (e.g., obstructive sleep apnea).

Ensures costs attributed to mandate are incremental to obesity coverage

Effectiveness inputs: Anchor to agent-specific efficacy (semaglutide, tirzepatide), weight by projected market share, and use observed real-world joint weight-loss distributions when available rather than multiplying trial efficacy by separate persistence factors.

Prevents double-counting dropout and enforces nesting across thresholds (>=5% subset includes >=10%, etc.)

Persistence inputs: Use post-shortage persistence data (2024 and later) specific to each agent; avoid using shortage-era refill-gap measures as they understate go-forward persistence.

Reference Marshall et al. showing persistence recovery; distinguishes supply disruption from patient-directed discontinuation

Cost-offsets: Apply a full multi-tier cost-offset schedule mapped to weight-loss bands (5/10/15/20/25%) per Thorpe & Joski rather than capping offsets at >=10%.

Captures larger savings among high responders, especially with tirzepatide

Transparency and sensitivity: Disclose exact calculations, primary sources, weighting, and provide sensitivity analyses for prevalence assumptions (e.g., 12.7% vs. CDC estimates) and average weight loss used in offset calculations.

Addresses concerns about unexplained assumptions and conflicting prevalence figures

Recommend excluding enrollees with a type 2 diabetes diagnosis or any antidiabetic pharmacy claim from estimates of incremental uptake of GLP-1 therapies attributed to an obesity coverage mandate. The report’s current exclusion removes only members already filling branded diabetes-specific GLP-1s and therefore leaves in people with obesity who have diabetes but are not yet on a GLP-1 (for example, those managed on metformin, newly diagnosed, or untreated). Including those enrollees risks attributing GLP-1 starts — and associated costs — to an obesity mandate when they would be covered and likely treated under existing diabetes indications.

If enrollees with diabetes are retained in the uptake population, the analysis must explicitly model diabetes-specific cost offsets and adherence (which the advisory group notes are typically higher for the diabetes population). Additionally, the population definition should align with other inputs (for example, adherence sources that exclude members by diagnosis or any antidiabetic drug claim) and consider excluding forecasted shares who will receive bariatric surgery or GLP-1 therapy for other covered indications such as obstructive sleep apnea.

Weight-loss Tiers & Coding Considerations

Weight-loss tiers for cost offsets

Weight-loss tiersApply Thorpe & Joski multi-tier offsets at 5%, 10%, 15%, 20%, and 25% mapped to modeled weight-loss bands

Thorpe reference valuesThorpe reports employer-sponsored savings from $670 (5%) to $2,849 (25%) per enrollee-year

Problem with truncationDo not collapse all responders ≥10% into a single 10% offset; that omits larger savings among high responders

Implementation noteModel a full weight-loss distribution so each band (5/10/15/20/25%) can be assigned its corresponding offset

RationaleModern GLP-1s, especially tirzepatide, reach high-response bands where Thorpe shows substantially greater savings

Provider Actions, Exclusions & Transparency

Prior Authorization

Exclude T2D patients from obesity-incremental GLP-1 uptake

Recommend excluding enrollees with a type 2 diabetes diagnosis or any antidiabetic pharmacy claim from the incremental obesity–GLP‑1 uptake estimate; if diabetes patients are retained, the analysis must instead include diabetes-specific cost‑offsets and adherence assumptions.

Exclude members with a recorded T2D diagnosis or any antidiabetic drug claim from obesity-targeted GLP-1 uptake projections.
If members with diabetes remain in the population, include higher expected GLP-1 cost offsets and higher adherence for the diabetes subgroup.

Step Therapy

Anchor effectiveness to semaglutide/tirzepatide and weight by market share

Anchor effectiveness inputs to the specific agents expected to be dispensed post-mandate (semaglutide and tirzepatide), weight evidence by projected market share, and model efficacy separately from adherence rather than conflating them into a single effectiveness parameter.

Clinical Background

GLP-1 receptor agonists and dual agonists (for example, semaglutide and tirzepatide) produce substantial weight loss in modern randomized trials and in real-world cohorts. Contemporary agents and dual agonists show higher proportions of participants achieving clinically meaningful weight-loss thresholds compared with older pharmacotherapies, and trial results (for example, SURMOUNT-1 for tirzepatide) report large shares reaching ≥5% and ≥10% weight loss at trial endpoints.

Because newer agents and market conditions differ from older products and shortage-era patterns, persistence and effectiveness estimates should be anchored to agent-specific evidence and recent real-world data rather than historical refill-gap metrics that understate likely go-forward persistence. The advisory group recommends using post-shortage persistence data and weighting trial efficacy by projected market share of semaglutide and tirzepatide rather than multiplying trial efficacy by separate persistence factors to avoid double-counting dropout.

Key Definitions

treatment-regimen estimand

DefinitionTreatment-regimen estimand: trial-reported efficacy measure that already reflects within-trial discontinuation and should not be multiplied again by external persistence rates

Implication for modelingDo not apply a separate persistence multiplier to trial treatment-regimen estimand efficacy — trials already include discontinuers

Supporting evidenceSURMOUNT-1 (tirzepatide) reports very high ≥5% and ≥10% rates at week 72 (85–91% and 69–84%), demonstrating high efficacy even with within-trial discontinuation accounted for

Real-world corroborationGasoyan et al. (2025) cohort measured at one year shows semaglutide ≈57% (≥5%) and ≈36% (≥10%); tirzepatide ≈73% (≥5%) and ≈56% (≥10%), all-including discontinuers