PDCD1 and breast cancer: Current clinical trials attempting to modulate immunity and attain durable responses in BC via PD-1 blockade along with standard treatment options, include TONIC phase II trial (NCT02499367) for the treatment of TNBC, and the phase Ib/II clinical trial PANACEA (NCT02129556), which is studying the efficacy in trastuzumab-resistant HER2-amplified BC.