Summary
The study will consist of two parts.
In Part 1, the safety of pembrolizumab (MK-3475) in combination with one of three different
chemotherapies will be assessed in the treatment of locally recurrent inoperable or
metastatic triple negative breast cancer (TNBC), which has not been previously treated with
chemotherapy.
In Part 2, the safety and efficacy of pembrolizumab plus background chemotherapy will be
assessed compared to the safety and efficacy of placebo plus background chemotherapy in the
treatment of locally recurrent inoperable or metastatic TNBC, which has not been previously
treated with chemotherapy.
The primary hypotheses are that:
1. the combination of pembrolizumab and chemotherapy prolongs Progression-Free Survival
(PFS) compared to placebo and chemotherapy in:
- all participants,
- participants with programmed cell death-ligand 1 (PD-L1) combined positive score
(CPS) =1 tumors, and
- participants with PD-L1 CPS =10 tumors, and
2. the combination of pembrolizumab and chemotherapy prolongs Overall Survival (OS)
compared to placebo and chemotherapy in:
- all participants,
- participants with PD-L1 CPS =1 tumors, and
- participants with PD-L1 CPS =10 tumors.