The PANACEA (Keynote-014) trial is a single-arm phase Ib/II trial assessing pembrolizumab (patients with PD-L1+ tumours in a 3 + 3 dose-escalation phase Ib part; patients with both PD-L1-positive or negative at a flat dose in phase II) plus standard trastuzumab in 58 HER2+ MBC patients at progression to previous trastuzumab-based therapy. Here, ERBB2 is linked to neoplasm.