(190) Budget impact analysis of generic mirabegron in Medicare Part D: translating savings into access

Background: : Anticholinergic drugs for overactive bladder and urinary incontinence (OAB/UI) have significant side effects in older adults. Safer β3‑agonists are more costly.

Objective: : To estimate the budget impact in Medicare Part D associated with recently available generic mirabegron, and determine the degree that generic pricing permits more patients to access mirabegron at the current level of Part D spending for OAB/IU drugs.

Methods: : A budget impact model was developed to estimate Medicare Part D savings after the introduction of generic mirabegron in 2024. Baseline utilization and expenditure data for anticholinergics, brand mirabegron, and brand vibegron were obtained from the 2023 Medicare Part D Prescribers by Provider and Drug dataset. In the new environment, brand vibegron utilization remained constant, while all patients using mirabegron were assumed to use the generic product, at a 14% price reduction (reflecting the current Wholesale Acquisition Cost). A two-way sensitivity analysis varied both generic price reduction (10%-75%) and mirabegron utilization (0%-200% increase). Additionally, we devised a spending-neutral scenario to determine the number of beneficiaries who could shift from anticholinergics to generic mirabegron at the 2023 level of overall spending, according to varying levels of generic mirabegron price reduction (10%-50%). A scenario analysis incorporated fracture and fall costs associated with anticholinergic use to evaluate their effect on overall spending

Results: : In 2023, prior to the introduction of generic mirabegron, the estimated annual Part D spending for drugs for OAB/UI was $2.813B. In the new environment spending was reduced by $295M, assuming a 14% mirabegron price reduction. Redirecting these savings could allow 140,838 patients to switch from anticholinergics to mirabegron without raising total annual costs. In the two-way sensitivity analysis, a 14% price reduction and 50% increase in the use of mirabegron resulted in $547M in additional spending. If the generic mirabegron price was reduced by 50% of brand cost, more than half (51.5%) of patients using anticholinergics could switch to generic mirabegron while maintaining current levels of spending. Incorporating costs for anticholinergic-associated falls/fractures added $85.4M to the current environment. This cost would be reduced by $6.8M in the new environment where 140,838 patients switched to mirabegron at neutral overall spending.

Conclusions: : Managed care can expand access to a safer alternative for OAB/UI without increasing overall spending.

Sponsorship:: None