Synthesis and Biological Investigation of Phenothiazine-Based Benzhydroxamic Acids as Selective Histone Deacetylase 6 Inhibitors

  • J Med Chem. 2019 Feb 14;62(3):1138-1166. doi: 10.1021/acs.jmedchem.8b01090.
Katharina Vögerl  1 ,  Nghia Ong  1 ,  Johanna Senger  2 ,  Daniel Herp  2 ,  Karin Schmidtkunz  2 ,  Martin Marek  3 ,  Martin Müller  1 ,  Karin Bartel  1 ,  Tajith B Shaik  3 ,  Nicholas J Porter  4 ,  Dina Robaa  5 ,  David W Christianson  4 ,  Christophe Romier  3 ,  Wolfgang Sippl  5 ,  Manfred Jung  2 ,  Franz Bracher  1
Affiliations
  • 1. Department of Pharmacy-Center for Drug Research , Ludwig-Maximilians University Munich , Butenandtstr. 5-13 , 81377 Munich , Germany.
  • 2. Institute of Pharmaceutical Sciences , University of Freiburg , Albertstraße 25 , 79104 Freiburg , Germany.
  • 3. Département de Biologie Structurale Intégrative, Institut de Génétique et Biologie Moléculaire et Cellulaire (IGBMC) , Université de Strasbourg (UDS), CNRS, INSERM , 67404 Illkirch Cedex , France.
  • 4. Department of Chemistry , University of Pennsylvania , 231 South 34th Street , Philadelphia , Pennsylvania 19104-6323 , United States.
  • 5. Institute of Pharmacy , Martin-Luther University of Halle-Wittenberg , 06120 Halle/Saale , Germany.
PMID: 30645113 DOI: 10.1021/acs.jmedchem.8b01090
Abstract

The phenothiazine system was identified as a favorable cap group for potent and selective histone deacetylase 6 (HDAC6) inhibitors. Here, we report the preparation and systematic variation of phenothiazines and their analogues containing a benzhydroxamic acid moiety as the zinc-binding group. We evaluated their ability to selectively inhibit HDAC6 by a recombinant HDAC enzyme assay, by determining the protein acetylation levels in cells by western blotting (tubulin vs histone acetylation), and by assessing their effects on various Cancer cell lines. Structure-activity relationship studies revealed that incorporation of a nitrogen atom into the phenothiazine framework results in increased potency and selectivity for HDAC6 (more than 500-fold selectivity relative to the inhibition of HDAC1, HDAC4, and HDAC8), as rationalized by molecular modeling and docking studies. The binding mode was confirmed by co-crystallization of the potent azaphenothiazine inhibitor with catalytic domain 2 from Danio rerio HDAC6.