The most potent NNMT inhibitor identified so far, 17u, has an IC50 value of 3.7 nM, but the inhibition of tumor growth only appeared when tested at 100 μM concentration in oral, lung, and bladder cancer cell lines, and this difference may be related to the poor cellular permeability of compound 17u [50]. Here, NNMT is linked to urinary bladder cancer.