Overall survival (OS) in KATE2, a phase II study of programmed death ligand 1 (PD-L1) inhibitor atezolizumab (atezo) plus trastuzumab emtansine (T-DM1) vs placebo (pbo) T-DM1 in previously treated HER2 advanced breast cancer (BC)

Abstract

Background T-DM1 is indicated for the treatment of HER2+ metastatic BC previously treated with trastuzumab and a taxane, separately or in combination. Atezo is an anti-PD-L1 antibody that inhibits PD-L1 binding to PD-1 and B7.1 thereby restoring antitumor immunity. In a phase 3 study, the addition of atezo to nab-paclitaxel significantly improved PFS in PD-L1+ pts with metastatic triple negative BC. In KATE2 (NCT02924883), adding atezo to T-DM1 in pts with HER2+ BC did not significantly increase PFS compared to T-DM1+pbo in the ITT population, but PFS was numerically longer in PD-L1+ pts. Here, we present OS and updated safety data from KATE2. Methods Pts with advanced HER2-positive BC that ..