PI3Kα-IN-21 (compound 8) is a PI3Kα inhibitor, and its selectivity for PI3Kα is 10.41/16.99/37.53 times higher than PI3Kβ/γ/δ respectively ( IC 50 : 96.89/568.24/397.48 nM ). PI3Kα-IN-21 inhibits cancer cell activity, proliferation, and migration, and induces mitochondrial apoptosis through the PI3K/Akt/mTOR pathway. PI3Kα-IN-21 exhibits in vivo antitumor potency in a mouse model of non-small cell lung cancer.