PI3K inhibitors may overcome drug resistance and improve advanced breast cancer (ABC) outcomes. Different PI3K inhibitors exhibit different effect against various PI3K types. Class IA pan-PI3K inhibitors have been more extensively studied than isoform specific inhibitors; Pictilisib is another pan-PI3K inhibitor with greater subunitα-inhibitor activity than buparlisib. Idelalisib is the first PI3K inhibitor approved by the US Food and Drug Administration and is utilized in the treatment of relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma and follicular lymphoma. Copanlisib is approved for relapsed follicular lymphoma in patients who have received at least two prior systemic therapies. Duvelisib is approved for relapsed/refractory chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL),  and relapsed/refractory follicular lymphoma, both indications for patients who have received at least two prior therapies.