Budget Impact Model for a One-Time Gene Therapy
A US regional payer with 1.2 million members asks the medical affairs HEOR team to review a budget impact model for a one-time gene therapy for hemophilia B. The list price is $2.8 million per infusion. The company's model assumes 92% of patients achieve durable factor IX expression for 5 years, based on a single-arm trial of 54 patients with 3-year follow-up, and assumes 100% adherence to annual prophylaxis costs in the comparator arm. The payer's pharmacy director says the plan can only budget over a 2-year horizon and asks for a 40% discount scenario. The commercial team wants medical affairs to 'validate' the model and say it is cost-saving. The published trial shows factor IX activity varied widely, two patients lost expression by year 3, and annual factor IX use fell but not to zero. The payer also asks about re-dosing if expression wanes.
1. What are the key methodological issues in the model that medical affairs should flag?
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Key issues: the model's 5-year durability assumption exceeds the 3-year single-arm evidence; 92% durable expression is optimistic given two patients lost expression and wide variability. The 100% comparator adherence assumption inflates savings. The payer's 2-year horizon does not match a one-time therapy with long-term benefit, so the model should show both horizons and explain the mismatch. A 40% discount is a scenario, not a base case. Re-dosing is a real cost and must be included. The model should also account for eligible population, uptake, wastage, administration, and patient assistance. Reasoning: budget impact is not the same as cost-effectiveness; a cost-saving claim depends on durability and comparator assumptions. Medical affairs should distinguish a methodological critique from commercial negotiation.
2. How should medical affairs respond to the commercial request to 'validate' the model as cost-saving?
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Medical affairs should not 'validate' the model as cost-saving unless the assumptions are defensible. It can provide a written critical appraisal: which inputs are supported by trial data, which are extrapolated, and how the conclusions change under plausible scenarios. It should correct the 100% adherence assumption, add re-dosing, and present a range of durability (for example, 3-year observed and 5-year scenario). The response should be transparent about the single-arm design and short follow-up. Boundary: commercial may use approved HEOR materials, but medical affairs cannot become a sales validator. Any external communication must be fair-balanced and reviewed. If the payer asks for a discount, that is a commercial discussion; medical affairs can explain the evidence but not negotiate. Document the request and the independent review.
3. What evidence would strengthen the payer discussion, and what claims should be avoided?
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Strengthen the discussion with long-term registry data, real-world factor IX use, re-dosing rates, bleeding outcomes, adherence, and patient-reported outcomes. A head-to-head trial is unlikely, so indirect comparisons need transparency. The company should also provide a patient assistance and outcomes-based agreement framework if available. Avoid: claiming cure, claiming cost savings beyond the model, extrapolating beyond the data without disclosure, or implying the payer must cover the drug. Offer a joint medical/HEOR meeting and a scenario-based dossier. If evidence is immature, say so; payers respect uncertainty more than overclaiming.