Pembrolizumab in combination with binimetinib in patients with unresectable locally advanced or metastatic triple-negative breast cancer.

Purpose: Activation of the RAS/MAPK pathway is associated with reduced tumor-infiltrating lymphocytes and poor outcomes in triple-negative breast cancer (TNBC). Previous studies demonstrated that inhibition of the MAPK pathway with a MEK inhibitor is synergistic with immune checkpoint inhibitors.

Experimental Design: We conducted a phase I/II trial of pembrolizumab and binimetinib in patients with metastatic TNBC with ≤ 3 prior lines of therapy.