1177-OR: Informing Medicare Prescription Drug Subsidy Expansion: A Cost Sensitivity Analysis of Income-Related Heterogeneity in Discontinuation of GLP-1 Receptor Agonists and SGLT2 Inhibitors

Introduction and Objective: GLP-1RAs and SGLT2is reduce cardiometabolic risk in patients with T2D, but high OOP costs limit access among lower-income Medicare Part D enrollees not receiving subsidies (income 150% federal poverty level FPL). It is unclear which income levels are most vulnerable to cost-related medication discontinuation. Evidence is needed to inform equitable policy design aligned with the benefits of these therapies. Methods: We examined unsubsidized Part D enrollees with T2D using 2015-23 Medicare Current Beneficiary Survey and claims data (n=11,020). To estimate the effect of higher OOP costs, we applied regression discontinuity at the Part D coverage gap threshold, comparing enrollees whose cumulative spending reached the threshold with those just below it, with pseudo-gap entry dates matched to the actual date distribution. Discontinuation was defined as a ≥30-day treatment gap within a 60-day window. Models had nonlinear income-cost interactions with covariate adjustment. We tested if effects differed by income and estimated counterfactual discontinuation rates. Results: Overall, 28.8% had incomes ≤ 200% FPL and 33.8% entered the coverage gap. Relative to enrollees just below the coverage gap, those who reached the gap had slightly higher incomes, higher rates of obesity and ASCVD, and greater use of GLP-1RAs (17.9% 0.7 vs 1.2% 0.1) and SGLT2is (16.8% 0.8 vs 2.0% 0.2). The effect of higher OOP in the coverage gap on discontinuation varied by income (GLP-1RAs p0.001; SGLT2is p=0.05), with the greatest cost sensitivity occurring among below-median-income unsubsidized enrollees (subgroup median ≈200% FPL) and attenuating with higher income. Higher OOP increased predicted discontinuation by about 75 pp at lower incomes vs 20 pp at higher incomes. Conclusion: Extending subsidy eligibility to 200% FPL may be a vital policy lever to prevent cost-related discontinuation and maximize the clinical benefits of GLP-1RAs and SGLT2is in Medicare. Disclosure E. Mitchell: None. M.K. Ali: Consultant; Ended; Eli Lilly and Company, Siemens, Novo Nordisk. M. Dieci: None. I. Graetz: Research Support; Current; Pfizer Inc. S.A. Patel: None. S. Patrick: None. C.R. Yarbrough: None. P. Li: None. H. Shao: None. Funding T32HL130025 (NHLBI), P30DK111024 (NIDDK), R01DK133465 (NIDDK), and 1R01DK143456 (NIDDK).