Design, synthesis, and evaluation of 4-(4-methyl-4H-1,2,4-triazol-3-yl)piperidine derivatives as potential glutaminyl cyclase isoenzyme inhibitors for the treatment of cancer.

Upregulated glutaminyl cyclase isoenzyme (isoQC) contributes to cancer development by catalyzing pE-CD47 generation and thus enhancing CD47-SIRPα binding and subsequent "don't eat me" signals. We thus consider that isoQC could represent a novel target for cancer therapy. We previously prepared a series of diphenyl conjugated imidazole derivatives (DPCIs) and evaluated their use as glutaminyl cyclase (QC) inhibitors. Here, a new series of DPCIs was rationally designed and synthesized. As anticipated, the analogues exhibited considerably improved inhibitory potency against both QC and isoQC. Crucially, these chemicals exhibited marked selectivity toward isoQC. Further assessments established that one selected compound (27) did not affect the viability of A549, H1299, PC9, or HEK293T cells or the body weight of mice. This compound did, however, reduce pE-CD47 levels in infected A549 cells (isoQC_OE and isoQC_KD) and exhibited apparent anti-cancer effects in vivo by downregulating the level of pE-CD47 via the inhibition of isoQC activity. Taken together, these findings indicated that the compounds synthesized in this study could represent potential QC/isoQC inhibitors for the treatment of cancers.