Histone lysine N-methyltransferase 2D (KMT2D), an important methyltransferase that is involved in the methylation of lysine 4 in histone H3 (H3K4) and related to the development of prostate cancer. Hypermethylation of H3K4 is shown in prostate cancer (PCa). However, KMT2D inhibitors have not yet been developed. This article aims to design small molecule inhibitors targeting KMT2D_SET to prevent PCa cell proliferation and migration. Twenty-four inhibitors were firstly designed according to a virtual screening of computers, and shown different degrees of binding to KMT2D_SET. Compounds 1 and 16 showed high binding affinities to KMT2D, with KD values of 147 +/- 32.9 mu M and 176 +/- 37.9 mu M, respectively. In addition, they exerted strong inhibitory activity against the PCa cell lines PC-3 and DU145, with IC50 values of 1.1 +/- 0.06 mu M, 1.5 +/- 0.06 mu M and 1.8 +/- 0.1 mu M, 2.3 +/- 0.2 mu M, respectively. Furthermore, these two compounds significantly suppressed the migration of PCa cells. (C) 2020 Elsevier Inc. All rights reserved.