CD274 and breast cancer: The phase II KATE2 trial evaluated the efficacy and safety of another anti-PDL1 agent, atezolizumab, in combination with T-DM1 in pre-treated patients with advanced HER2-positive breast cancer [95] but failed to demonstrate a clinically meaningful improvement in PFS (8.2 vs. 6.8 months; HR = 0.82, 95%CI 0.55–1.23, p = 0.33) and showed an association with more adverse events.