Research Scientist Harvard Pilgrim Health Care Institute and Harvard Medical School , United States
Background: Trastuzumab is an anti-human epidermal growth factor receptor 2 (HER2) monoclonal antibody used to treat breast and other cancers. Trastuzumab biosimilars were approved in the United States beginning in 2017, yet utilization information on these biosimilars is limited.
Objectives: To evaluate utilization plus patient baseline sociodemographic and clinical characteristics for the trastuzumab originator (Herceptin®), its biosimilars, and other HER2 inhibitors.
Methods: We evaluated healthcare claims data from the Biologics & Biosimilars Collective Intelligence Consortium (BBCIC) distributed research network (DRN), representing >95 million person-years among commercially insured individuals in the US. We distributed a data query using the Food and Drug Administration Sentinel analytical tools to four DRN health plan partners to capture product usage data and patient information (i.e., demographics and clinical characteristics that may impact prescribing) from 01 October 2016 to 31 May 2022. Patients were required to be continuously enrolled in their health plan with both medical and drug coverage for ≥365 days before their first observed trastuzumab utilization date in this study period. Data were then aggregated across the partners.
Results: Nearly 18 million eligible health plan members representing over 33 million person-years of data were evaluated. We identified 7,598 incident treatment episodes (incident to the drug itself), of which, 3,920 (52%) episodes were with the originator. The mean age varied from 53.4 to 64.1 years old and over 80% of the episodes for each product were among females. The mean comorbidity index score was 1.2 (SD=1.9) among users of the originator versus the biosimilars (range 1.0-2.6); other clinical characteristics were generally comparable across products. The proportion of total incident episodes of the originator was high at the beginning of the study period and decreased over time (90% in 2016 vs. 19% in 2021) as utilization of the biosimilars increased. For instance, use of trastuzumab-anns (Kanjinti®) increased from 0% in 2016 to 28% in 2021. Similar utilization trends were seen among patients with and without metastatic disease. Data in 2020-2022 need to be interpreted with caution due to incomplete data of certain partners in those years.
Conclusions: Utilization of trastuzumab biosimilar products has grown since their introduction to the US market and is expected to continue to rise. Exploration of these biosimilars' comparative benefit and safety to their originator product is warranted and is a priority for future BBCIC analyses.
