Why wasn't mirabegron chosen for the first year of the CMS negotiation program?

Importance: The most used overactive bladder (OAB) medications are anticholinergics, which professional societies recommend avoiding in older patients given dementia risk. Cost prevents patients from switching to preferred beta-3 agonists. Mirabegron was the only beta-3 agonist eligible for the Centers for Medicare/Medicaid Services (CMS) 2023 Drug Negotiation Program (DNP). While mirabegron's price would be markedly reduced by inclusion in the DNP, only ten drugs were chosen in its first year.Objectives: We sought to explain mirabegron's absence from CMS's 2023 DNP and estimate the percentage of anticholinergic to mirabegron conversions needed to merit DNP inclusion.Study design: We modeled CMS's 2023 selection process using publicly available dashboards from 2017-2021. Among the 20 costliest drugs, we excluded ineligible drugs and categorized the remainder as DNP chosen/not chosen. For drugs not chosen, we used price inflation and beneficiary utilization trends to project total 2023 costs.Results: In 2021, mirabegron was the 14th most costly drug overall-9th when excluding ineligibles-and the only top-20 drug eligible but not selected for the 2023 DNP. We estimated mirabegron to be 96.7% the cost of the 10th most costly drug. Switching 1.2% of 2021 anticholinergic prescriptions to mirabegron would have led to DNP inclusion, presenting an interesting dilemma where more patients would use mirabegron if it were cheaper, but insufficient patients used it for DNP inclusion to make it cheaper.Conclusions: Mirabegron came exceedingly close to DNP selection in 2023, and its future inclusion in the DNP would likely herald a massive shift of Medicare patients away from anticholinergics.