Integrating trastuzumab biosimilars and HER2-directed therapies into HER2-positive breast cancer management.

The approval of the humanized monoclonal antibody trastuzumab in 1998 changed the trajectory of treatment and subsequent outcomes for patients with human epidermal growth factor receptor 2 (HER2)-positive breast cancer and is now the standard of care in the neoadjuvant, adjuvant, and metastatic settings. However, as with most biologic drugs, trastuzumab comes with a relatively high price tag compared with traditional cytotoxic chemotherapy and contributes to healthcare budgets. Three engineered products related to trastuzumab-2 antibody-drug conjugates, ado-trastuzumab emtansine and fam-trastuzumab deruxtecan-nxki, as well as the subcutaneous trastuzumab/hyaluronidase-have since been approved and have expanded the treatment options for this patient population. The approval of 5 trastuzumab biosimilars as of the end of 2019 holds the promise of considerable cost savings, but challenges to integrating their use into patient care must be addressed. Barriers to their use, including physician uncertainty to switch patients from the reference drug to the therapeutic biosimilar and patients' lack of understanding about biosimilars, are common in the United States. It is also important that all stakeholders, including managed care professionals, pharmacists, and practice administrators, understand how to incorporate trastuzumab biosimilars into formulary discussions, clinical care plans and processes, and educational initiatives for healthcare providers and patients.