FDA Approval Summary: Ado-Trastuzumab Emtansine for the Adjuvant Treatment of HER2-positive Early Breast Cancer

On May 3, 2019, the FDA granted regular approval to ado-trastuzumab emtansine (KADCYLA), for the adjuvant treatment of patients with HER2-positive early-breast cancer (EBC) who have residual invasive disease after neoadjuvant taxane-based chemotherapy and trastuzumab-based treatment. Approval was based on data from the KATHERINE trial, which randomized patients to receive ado-trastuzumab emtansine or trastuzumab. At 3 years, the event-free rate for invasive disease-free survival in the ado-trastuzumab emtansine arm was 88.3% [95% confidence interval (CI), 85.8-90.7] compared with 77.0% (95% CI, 73.8-80.7) in the trastuzumab arm, (HR, 0.50; 95% CI, 0.39-0.64; P < 0.0001). Results from secondary endpoints, subgroup analyses, and sensitivity analyses generally supported the primary efficacy endpoint results. Common adverse reactions (>25% and higher incidence in ado-trastuzumab emtansine arm) with ado-trastuzumab emtansine were fatigue, nausea, increased transaminases, musculoskeletal pain, hemorrhage, thrombocytopenia, headache, peripheral neuropathy, and arthralgia. Ado-trastuzumab emtansine is the first drug approved for the treatment of patients with residual disease after neoadjuvant treatment and surgery. This article summarizes the FDA review and the data supporting the approval of ado-trastuzumab emtansine as a component of treatment for patients with HER2-positive EBC with residual disease.