Discovery of (2E)-3-{2-butyl-1-[2-(diethylamino)ethyl]-1H-benzimidazol-5-yl}-N-hydroxyacrylamide (SB939), an orally active histone deacetylase inhibitor with a superior preclinical profile

J Med Chem. 2011 Jul 14;54(13):4694-720. doi: 10.1021/jm2003552. Epub 2011 Jun 16.


A series of 3-(1,2-disubstituted-1H-benzimidazol-5-yl)-N-hydroxyacrylamides (1) were designed and synthesized as HDAC inhibitors. Extensive SARs have been established for in vitro potency (HDAC1 enzyme and COLO 205 cellular IC(50)), liver microsomal stability (t(1/2)), cytochrome P450 inhibitory (3A4 IC(50)), and clogP, among others. These parameters were fine-tuned by carefully adjusting the substituents at positions 1 and 2 of the benzimidazole ring. After comprehensive in vitro and in vivo profiling of the selected compounds, SB939 (3) was identified as a preclinical development candidate. 3 is a potent pan-HDAC inhibitor with excellent druglike properties, is highly efficacious in in vivo tumor models (HCT-116, PC-3, A2780, MV4-11, Ramos), and has high and dose-proportional oral exposures and very good ADME, safety, and pharmaceutical properties. When orally dosed to tumor-bearing mice, 3 is enriched in tumor tissue which may contribute to its potent antitumor activity and prolonged duration of action. 3 is currently being tested in phase I and phase II clinical trials.

MeSH terms

  • Administration, Oral
  • Animals
  • Antineoplastic Agents / chemical synthesis*
  • Antineoplastic Agents / pharmacokinetics
  • Antineoplastic Agents / pharmacology
  • Benzimidazoles / chemical synthesis*
  • Benzimidazoles / pharmacokinetics
  • Benzimidazoles / pharmacology
  • Biological Availability
  • Cell Line, Tumor
  • Dogs
  • Drug Screening Assays, Antitumor
  • Female
  • Histone Deacetylase 1 / antagonists & inhibitors
  • Histone Deacetylase Inhibitors / chemical synthesis*
  • Histone Deacetylase Inhibitors / pharmacokinetics
  • Histone Deacetylase Inhibitors / pharmacology
  • Humans
  • Isoenzymes / antagonists & inhibitors
  • Isoenzymes / metabolism
  • Mice
  • Mice, Inbred BALB C
  • Mice, Nude
  • Microsomes, Liver / metabolism
  • Neoplasm Transplantation
  • Quantitative Structure-Activity Relationship
  • Rats
  • Rats, Wistar
  • Stereoisomerism


  • Antineoplastic Agents
  • Benzimidazoles
  • Histone Deacetylase Inhibitors
  • Isoenzymes
  • SB939 compound
  • Histone Deacetylase 1