Development of <i>N</i>‑Hydroxycinnamamide-Based Histone Deacetylase Inhibitors with an Indole-Containing Cap Group

Abstract

A novel series of histone deacetylase inhibitors combining <i>N</i>-hydroxycinnamamide bioactive fragment and indole bioactive fragment was designed and synthesized. Several compounds (<b>17c</b>, <b>17g</b>, <b>17h</b>, <b>17j</b>, and <b>17k</b>) exhibited comparable, even superior, total HDACs inhibitory activity and in vitro antiproliferative activities relative to the approved drug SAHA. A representative compound <b>17a</b> with moderate HDACs inhibition was progressed to isoform selectivity profile, Western blot analysis, and in vivo antitumor assay. Although HDACs isoform selectivity of <b>17a</b> was similar to that of SAHA, our Western blot results indicated that intracellular effects of <b>17a</b> at 1 μM were class I selective. It was noteworthy that the effect on histone H4 acetylation of SAHA decreased with time, while the effect on histone H4 acetylation of <b>17a</b> was maintained and even increased. Most importantly, compound <b>17a</b> exhibited promising in vivo antitumor activity in a U937 xenograft model