Exploration of some indole-based hydroxamic acids as histone deacetylase inhibitors and antitumor agents

In our search for novel small molecules targeting histone deacetylases, we have designed and synthesized a series of novel hydroxamic acids incorporating indole moiety as a cap group (3a–l). Biological evaluation showed that these hydroxamic acids potently inhibited HDAC2 with IC50 values in submicromolar range and up to tenfold (compound 3j) better than that of SAHA (also known as suberoylanilide hydroxamic acid). In four human cancer cell lines [SW620 (colon), PC-3 (prostate), AsPC-1 (pancreatic), NCI-H23 (lung)], the synthesized compounds that exhibited potent cytotoxicity with several compounds (3k, 3l) were found to be 12- to 77-fold more cytotoxic than SAHA. Docking experiments indicated that the compounds tightly bound to HDAC2 at the active binding site with binding affinities much higher than that of SAHA. Our present results demonstrate that these novel hydroxamic acids are potential for further development as anticancer agents.