RK-9123016 is a potent inhibitor of SIRT2. RK-9123016 inhibits the enzymatic activity of SIRT2 with an IC 50 value of 0.18 µM but not other human sirtuin members including SIRT1 and SIRT3 at 100 µM. RK-9123016 increases the acetylation level of eukaryotic translation initiation factor 5A (eIF5A), a physiological substrate of SIRT2 , and reduces cell viability of human breast cancer cells accompanied with a decrease in c-Myc expression.