Two categories of increasingly targeted agents that have been used in the past 20 years due to these continued improvements in molecular subtyping, which classifies breast cancers by subtype, such as luminal A/B, HER2-enriched, triple-negative, and other types, include CDK4/6 inhibitors for hormone receptor-positive disease and immune checkpoint inhibitors in subsets of triple-negative breast cancer (TNBC) [3]. The gene discussed is ERBB2; the disease is breast cancer.