The safety analysis showed a similar incidence of grade 3 or greater adverse events during neoadjuvant therapy (15% of patients on ABP 980 vs. 14% on trastuzumab). Grade 3 or greater neutropenia occurred in 6% of patients in each group.
During adjuvant therapy, grade 3 or greater adverse events occurred in 9% of patients continuing ABP 980, 6% continuing trastuzumab, and 8% of these switched from trastuzumab to ABP 980. The most frequent grade 3 or greater events of interest were infections and neutropenia, all occurring in 1% of patients in each arm, and infusion reaction, which occurred in 1% of patients who stayed on the assigned HER2 inhibitor and in 2% of patients who were switched to ABP 980.
There were two patient deaths from adverse events, each deemed to be unrelated to treatment. One patient died from pneumonia during neoadjuvant ABP 980 therapy, and one died from septic shock during adjuvant therapy with ABP 980 after being switch from trastuzumab.
“To our knowledge, this is the first study of a trastuzumab biosimilar encompassing a single-switch design from the reference product to a biosimilar, which allowed us to assess the clinical safety and immunogenicity of this approach to treatment. Safety and immunogenicity were similar in patients who were switched and in those who continued to receive trastuzumab as adjuvant therapy,” the investigators wrote.
SOURCE: von Minckwitz G et al. Lancet Oncol 2018 Jun 4. doi: 10.1016/S1470-2045(18)30241-9.