The First Biologically Active Synthetic Analogues of FK228, the Depsipeptide Histone Deacetylase Inhibitor

Abstract

The FK228 and spiruchostatin bicyclic depsipeptide natural products are among the most potent histone deacetylase (HDAC) inhibitors known. Although FK228 is in advanced clinical trials, the complexity of the natural products has precluded mechanistic studies and the discovery of structure-activity relationships. By total synthesis, we have prepared the first depsipeptide analogues. Our results prove that the dehydrobutyrine residue in FK228 is not essential, and other residues can be substituted without loss of HDAC inhibitory activity. Conformational restriction by the macrocyclic scaffold is important, as a linear peptide was inactive. The intramolecular disulfide formed with a cysteine side chain can be removed provided the zinc-binding thiol is protected to ensure good cellular availability. Like the natural products, the analogues are selective against class I isoforms, with nanomolar inhibition of class I HDAC1 and significantly less potency against class II HDAC6.Eukaryotic DNA is packaged together with histone and nonhistone proteins into the higher order structure of chromatin. Chromatin proteins feature extensive posttranslational modification 1 including methylation, acetylation, phosphorylation, ubiquitinylation, sumoylation, and poly-ADPribosylation. These dynamic alterations are believed to constitute a 'histone code' 2 that mediates protein-DNA and protein-protein interactions in chromatin and thereby ultimately regulates gene transcription. Consequently, the modulation of the chromatin histone code offers opportunities for targeting diverse disease states at a higher level of intervention than individual signal transduction pathways. Among the enzymes involved in chromatin remodeling, zinc-dependent histone deacetylases (HDACs a ) are currently at the most advanced stage in drug discovery, with one FDA approval and numerous other compounds in clinical development. These metalloenzymes catalyze the hydrolysis of acetyllysine residues back to lysine. Since the latter, unlike acetyllysine, is protonated at physiological pH, this switch has a dramatic effect on chromatin structure and recruitment of binding partners. Furthermore, reversible lysine acetylation is now recognized 3 as a general posttranslational modification with important functional consequences in nuclear and cytoplasmic proteins unrelated to chromatin, thus increasing the therapeutic importance of this event.HDAC inhibitor design has concentrated 4 on the class I and class II zinc-dependent enzymes, comprising HDACs 1-11 in the human genome. These hydrolases share a highly conserved catalytic domain containing an active site zinc ion, and the majority of inhibitors fall into five broad structural classes (Figure 1): short chain aliphatic carboxylic acids, hydroxamic acids, benzamides, cyclic peptides, and the depsipeptides. HDAC inhibitors are typically substrate mimics of the linear acetyllysine side chain with a zinc-binding group replacing the scissile acetamide and a 'cap' at the other end extending beyond the enzyme substrate-bi...

Anticolon Cancer Activity of Largazole, a Marine-Derived Tunable Histone Deacetylase Inhibitor

“…Our previous and present studies indicated that altering the macrocycle conformation, e.g., by inversion of C17 stereocenter (Ying et al, 2008a) or N-methylation, is detrimental to largazole's activity. In contrast, there is only limited SAR available for FK228 (Yurek-George et al, 2007).…”

Human endogenous retrovirus (HERV) expression is not induced by treatment with the histone deacetylase (HDAC) inhibitors in cellular models of HIV-1 latency

“…The removal of acetyl groups from histones by HDACs leads to transcriptional repression; inhibition of these enzymes is therefore thought to favour gene expression [34]. Vorinostat and panobinostat are hydroxamic acids that bind to zinc, preventing its use by the zinc-dependent HDACs [29], while romidepsin is activated in vivo to produce a zinc-binding thiol [35]. In addition, the use of protein kinase C (PKC) activators, such as phorbol 12-myristate 13-acetate (PMA), has been found to induce HIV-1 expression, via nuclear factor κB (NF-κB) and specificity protein (Sp) transcription factor activation [1].…”

Functionalisation of Macroheterocycles with Preserving and Changing Their Sizes

“…Thus, the development of the bicyclic structure in synthesis of antitumor agents of spiruchostatin A (119) [74,75] and FK228 depsipeptide (FR901228) (120) [76][77][78][79][80][81][82] was carried out by consecutive macrocyclization reactions of hydroxy acids (121) or (122) by the Shiina's method or under Mitsunobu conditions, correspondingly, followed by the formation of the disulphide fragment in oxidation with iodine (Scheme 28).…”