Several TKIs are used to treat breast cancer and are directed against EGFR (gefitinib, lapatinib, erlotinib), HER2 (lapatinib, neratinib), CDK4/6 (ribociclib, palbociclib, abemaciclib), and the PI3K/Akt/mTOR pathway (alpelisib, pictisilib, everolimus), among others [reviewed in (236)]. The gene discussed is PIK3CA; the disease is breast cancer.