Isolation, semisynthesis, covalent docking and transforming growth factor beta-activated kinase 1 (TAK1)-inhibitory activities of (5Z)-7-oxozeaenol analogues

Lara Fakhouri,Tamam El-Elimat,Dow P Hurst,Patricia H Reggio,Cedric J Pearce,Nicholas H Oberlies,Mitchell P Croatt

doi:10.1016/j.bmc.2015.09.037

Abstract

(5Z)-7-Oxozeanol and related analogues were isolated and screened to explore their activity as TAK1 inhibitors. Seven analogues were synthesized and more than a score of natural products isolated that examined the role that different areas of the molecule contribute to TAK1 inhibition. A novel nonaromatic difluoro-derivative was synthesized that had similar potency compared to the lead. This is the first example of a nonaromatic compound in this class to have TAK1 inhibition. Covalent docking for the isolated and synthesized analogues was carried out and found a strong correlation between the observed activities and the calculated binding.

Highlights

Turning on of the upstream key signaling enzyme results in subsequent phosphorylation of specific MAP2Ks and MAPKs, which in turn activates a number of transcription factors including AP-1 and NF-κB.3
It has been shown that inhibiting the Transforming growth factor-β-activated kinase 1 (TAK1)/NF-κB signaling pathway, using either TAK1 inhibitors or via silencing its expression, promotes apoptosis in colon cancer,5 suppresses renal cell6 carcinoma survival,7 inhibits proliferation of LPS-induced human hepatocellular carcinoma,8 and reverses chemoresistance of pancreatic cancer
In 2003 it was found that 1 was a potent inhibitor of TAK1 with an IC50 of 8.1 nM.12 (5Z)-7-Oxozeaenol binds covalently to its target and, similar to almost all other kinase inhibitors,13 is a competitive ATP ligand that binds covalently to its target.12. This irreversible interaction was determined when the covalently-bound ligand was co-crystalized with TAK1.14 The interest in discovering and developing small molecule covalent inhibitors stems from the fact that these ligands may have increased selectivity for their targets and the potential for less intense side effects, resulting from dose reduction of the candidate drug to achieve therapeutic efficacy

Summary

Introduction

Transforming growth factor-β-activated kinase 1 (TAK1) is a member of the serine/threonine mitogen-activated protein kinase kinase kinase (MAP3K) family. A wide range of extracellular stimuli, such as proinflammatory interleukins, activate the intracellular TAK1 via membranebound receptors. Turning on of the upstream key signaling enzyme results in subsequent phosphorylation of specific MAP2Ks and MAPKs, which in turn activates a number of transcription factors including AP-1 and NF-κB. The aforementioned DNA-binding proteins are known to regulate inflammatory responses and apoptosis. In 2003 it was found that 1 was a potent inhibitor of TAK1 with an IC50 of 8.1 nM. (5Z)-7-Oxozeaenol binds covalently to its target and, similar to almost all other kinase inhibitors, is a competitive ATP ligand that binds covalently to its target.12 This irreversible interaction was determined when the covalently-bound ligand was co-crystalized with TAK1.14 The interest in discovering and developing small molecule covalent inhibitors stems from the fact that these ligands may have increased selectivity for their targets and the potential for less intense side effects, resulting from dose reduction of the candidate drug to achieve therapeutic efficacy.. Covalent docking of the isolated and synthesized analogues was carried out to correlate, at a molecular level, structural changes with variations in inhibitory activity. These data are presented to establish structure–activity relationships for (5Z)-7oxozeaenol’s TAK1 activity.

Results and discussion

Analysis of TAK1 inhibition

Covalent docking

Conclusion

General experimental procedures

Computational calculations and covalent docking