On May 3, 2019, the US Food and Drug Administration (FDA) approved ado-trastuzumab emtansine (Kadcyla; Genentech) for the adjuvant treatment of patients with HER2-positive early breast cancer who have residual invasive disease after neoadjuvant taxane and trastuzumab-based treatment. Patients should be selected for treatment with this agent based on an FDA-approved companion diagnostic test (Ventana Medical System’s PATHWAY anti-HER-2/neu [4B5] Rabbit Monoclonal Primary Antibody assay or INFORM HER2 Dual ISH DNA Probe Cocktail assay).
This latest approval was based on the phase 3, multicenter, open-label KATHERINE clinical trial of 1486 patients with HER2-positive early breast cancer. Patients were randomized in a 1:1 ratio to ado-trastuzumab emtansine (3.6 mg/kg intravenously every 3 weeks) or trastuzumab (6 mg/kg intravenously every 3 weeks) for 14 cycles. Patients were required to have had neoadjuvant taxane and trastuzumab-based therapy with residual invasive tumor in the breast and/or axillary lymph nodes.
After a median follow-up of 40 months, results showed that treatment with ado-trastuzumab emtansine significantly improved invasive disease-free survival compared with trastuzumab (hazard ratio, 0.50; 95% confidence interval, 0.39-0.64; P <.0001).
The most common adverse reactions (≥25%) associated with ado-trastuzumab in patients with early breast cancer were fatigue, nausea, increased transaminases, musculoskeletal pain, hemorrhage, thrombocytopenia, headache, peripheral neuropathy, and arthralgia.
Ado-trastuzumab emtansine was previously approved by the FDA on February 22, 2013, for the treatment of patients with HER2-positive, metastatic breast cancer who previously received trastuzumab and a taxane, separately or in combination.
The recommended dose of ado-trastuzumab emtansine is 3.6 mg/kg given as an intravenous infusion, every 3 weeks (21-day cycle), until disease recurrence or unacceptable toxicity, or a total of 14 cycles for patients with early breast cancer.