DPP8/9-IN-2 (Compound 21) is a DPP8/9 inhibitor with IC50 values of 0.22 nM and 3 nM, respectively, and Ki values of 2.9 nM and 6 nM, respectively . DPP8/9-IN-2 has certain cardiotoxicity, with IC50 values of 0.7 µM, 29.0 µM and 27.7 µM for hERG potassium channel, Nav1.5 sodium channel and Cav1.2 calcium channel, respectively. DPP8/9-IN-2 can be used in the research of diseases such as tumors[1].