Clinical development of immunotherapies for HER2 + breast cancer: a review of HER2-directed monoclonal antibodies and beyond.

Human epidermal growth factor receptor 2-positive (HER2 ⁺ ) breast cancer accounts for ~25% of breast cancer cases. Monoclonal antibodies (mAbs) against HER2 have led to unparalleled clinical benefit for a subset of patients with HER2 ⁺ breast cancer. In this narrative review, we summarize advances in the understanding of immune system interactions, examine clinical developments, and suggest rationales for future investigation of immunotherapies for HER2 ⁺ breast cancer. Complex interactions have been found between different branches of the immune system, HER2 ⁺ breast cancer, and targeted treatments (approved and under investigation). A new wave of immunotherapies, such as novel HER2-directed mAbs, antibody drug conjugates, vaccines, and adoptive T-cell therapies, are being studied in a broad population of patients with HER2-expressing tumors. The development of immunotherapies for HER2 ⁺ breast cancer represents an evolving field that should take into account interactions between different components of the immune system.
Competing Interests: Competing interestsR.L.B.C. received honorarium from Bristol Meyers Squib and Pfizer; he has also received a research grant from Bristol Meyers Squib. B.J.C. has intellectual property potential on the DC1 vaccine.
(© The Author(s) 2020.)