a, Schematic of DPP8/9 and PEPD activity. b, Structures of CQ04 and CQ31. c, Inhibition of recombinant PEPD activity. IC50 values are shown in parentheses. d, Evaluation of PEPD activity (AP cleavage) in control and PEPD−/− THP-1 cell lysates treated with the indicated compounds. The release of free alanine in c and d was determined using an alanine assay kit (Sigma). Data in c and d are presented as means ± s.e.m. of three replicates. e, CETSA analyses of the indicated compounds (10 μM) in HEK 293T lysates. All data, including immunoblots and CETSA, are representative of three or more independent experiments.