Utilization trends in CAR T cell therapy and bispecific antibodies among Medicare beneficiaries: A five-year claims analysis (2019-2023).

e19012 Background: T-cell engaging therapies, including chimeric antigen receptor T-cell (CAR T-cell) therapy and many bispecific monoclonal antibodies (BsAbs), have expanded treatment options for those living with relapsed/refractory hematologic malignancies. These therapies offer potential for durable remission, making equitable access a critical concern. Despite clinical advances, significant access gaps remain, and real-world utilization patterns across Medicare coverage types remain understudied. Prior research has largely focused on clinical outcomes, costs, and sociodemographic disparities, with limited examination of utilization differences by Medicare coverage type. With Medicare Advantage (MA) enrollment now exceeding 50% of beneficiaries, understanding access patterns has important policy implications. Methods: We conducted a retrospective analysis of CAR T-cell and BsAb claims among Medicare beneficiaries in the United States. Fee-for-service (FFS) claims were obtained from 100% Research Identifiable Files, and MA data were obtained from 100% Medicare Advantage Encounter Data (2019-2023). Unique beneficiaries receiving CAR T-cell or BsAb therapy were identified using HCPCS and ICD-10-PCS codes for seven CAR T-cell products and nine BsAb products. Clinical trial claims were excluded to focus on commercially purchased therapies. FFS claims were excluded if Medicare was not the primary payer. Annual beneficiary counts were tabulated and compared to underlying FFS/MA enrollment shares. Results: From 2019-2023, unique beneficiaries receiving CAR T-cell therapy increased from 336 to 1,635 (FFS) and 150 to 936 (MA); BsAb beneficiaries increased from 78 to 2,920 (FFS) and 248 to 1,826 (MA). In 2023, FFS beneficiaries accounted for 64% of CAR T-cell recipients and 62% of BsAb recipients, despite representing 49% of Medicare enrollment. FFS beneficiaries were approximately 1.3 times more likely than MA beneficiaries to receive both therapy classes relative to their enrollment shares. Conclusions: While utilization of CAR T-cell and BsAb therapies is growing among Medicare beneficiaries, absolute numbers remain modest, and significant access gaps persist; prior research suggests fewer than 2 in 10 eligible patients receive CAR T-cell therapy. FFS beneficiaries are overrepresented among recipients of both therapy classes relative to their enrollment share. Whether this reflects differences in patient characteristics, prior authorization requirements, ATC network participation, or reimbursement dynamics remains unclear. As MA enrollment continues to grow, ensuring equitable patient access to CAR T-cell and BsAb therapies across coverage types warrants further attention. Future research should adjust for patient and clinical factors to better isolate coverage-related barriers.