Currently, four PI3K inhibitors—copanlisib (pan-class I PI3K inhibitor), duvelisib (PI3Kδ/γ), idelalisib (PI3Kδ), and alpelisib (PI3Kα)—have received FDA approval for a variety of indications, including breast cancer and several lymphoma subtypes [86]. This evidence concerns the gene PIK3CA and breast cancer.