title: Isoform-specific histone deacetylase inhibitors: the next step?
abstract: Histone deacetylases (HDACs) have emerged as attractive drug targets, particularly for neoplastic indications. This large family is divided into four classes, of which three consist of zinc-dependent enzymes, and inhibitors of these are the subject of this review. Currently, there are several inhibitors advancing through clinical trials, all of which inhibit multiple isoforms of these three classes. While promising, these compounds have exhibited toxicities in the clinic that might limit their potential, particularly in solid tumors. It may be possible to reduce some of the toxicity by specifically targeting only the isoform(s) involved in maintaining that particular tumor and spare other isoforms that are uninvolved or even beneficial. This review examines the selectivity and toxicity of HDAC inhibitors currently in clinic, comparing pan-HDAC inhibitors to Class I selective compounds. The rationale for isoform-specific inhibitors is examined. The current status of isoform-specific inhibitor development is analyzed, especially inhibitors of HDAC1, 2, 4 and 8 enzymes, and the potential clinical utility of these compounds is discussed.
authors.affiliation: Department of Cancer Biology, Pharmacyclics, Inc, Sunnyvale, CA 94085, United States. sriram@pcyc.com
authors.forename: Sriram
authors.initials: S
authors.lastname: Balasubramanian
authors.forename: Erik
authors.initials: E
authors.lastname: Verner
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Buggy
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000009:adverse effects / Q000737:chemistry / Q000627:therapeutic use*; D001665:Binding Sites; D004353:Drug Evaluation, Preclinical; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008958:Models, Molecular; D009369:Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D013329:Structure-Activity Relationship
chemical_list: D000970:Antineoplastic Agents; D056572:Histone Deacetylase Inhibitors; D007527:Isoenzymes; D006655:Histone Deacetylases