Leisha A. Emens1,2 and Sherene Loi3,4 1Department of Medicine, University of Pittsburgh/UPMC Hillman Cancer Center, Pittsburgh, Pennsylvania 15232, USA 2Ankyra Therapeutics, Boston, Massachusetts 02116, USA 3The Sir Peter MacCallum Department of Medical Oncology, University of Melbourne, Parkville, Victoria 3010, Australia 4Division of Cancer Research, Peter MacCallum Cancer Centre, Melbourne, Victoria 3000, Australia Correspondence: lemensankyratx.com, sherene.loipetermac.org

Immunotherapy, particularly agents targeting the immunoregulatory PD-1/PD-L1 axis, harnesses the power of the immune system to treat cancer, with unique potential for a durable treatment effect due to immunologic memory. The PD-1 inhibitor pembrolizumab combined with neoadjuvant chemotherapy followed by adjuvant pembrolizumab improves event-free survival and is a new standard of care for high-risk, early-stage triple-negative breast cancer (TNBC), regardless of tumor PD-L1 expression. For metastatic TNBC, pembrolizumab combined with chemotherapy is a new standard of care for the first-line therapy of PD-L1+ metastatic TNBC, with improvement in overall survival. The PD-L1 inhibitor atezolizumab combined with nab-paclitaxel is also approved outside the United States for the first-line treatment of metastatic PD-L1+ TNBC. Current research focuses on refining the use of immunotherapy in TNBC by defining informative predictive biomarkers, developing immunotherapy in early and advanced HER2-driven and luminal breast cancers, and overcoming primary and secondary resistance to immunotherapy through unique immune-based strategies.