Methods of selectively inhibiting Akt3 are provided. It has been discovered that 4-[(6-nitroquinolin-4-yl)amino]-N-[4-(pyridin-4-ylamino)phenyl]benzamide selectively inhibits Akt3. Because Akt3 modulates the suppressive function of natural Tregs and the polarization of induced Tregs, 4-[(6-nitroquinolin-4-yl)amino]-N-[4-(pyridin-4-ylamino)phenyl]benzamide can be used for modulating immune responses.