Small molecule inhibitors of Mdm2 E3 ubiquitin ligase activity

Dickens, Michael (2011) Small molecule inhibitors of Mdm2 E3 ubiquitin ligase activity. PhD thesis, University of Nottingham.



Half of cancers retain wild type p53 but have alterations in the pathways involved in p53 regulation. Murine double minute 2 (Mdm2) regulates p53 by acting as an E3 ubiquitin ligase, which tags p53 for degradation through the proteasome. A small molecule inhibitor, a 5-deazaflavin analogue, has previously been identified by high throughput screening to inhibit Mdm2 E3 ubiquitin ligase activity, thereby reactivating apoptotic function of p53 selectively in cancer cells.

Ninety 5-deazaflavin analogues have been synthesised by an optimized existing method and a novel method of synthesis, using the required 6-anilinouracil and 2-p-toluenesulfonyloxybenzaldehyde.The biological ability of the 5-deazaflavin analogues to act as inhibitors of Mdm2 E3 ubiquitin ligase activity to reactivate p53 has been ascertained. A new quantitative biological assay was developed, by scientists based at the Beatson Institute, for 5-deazaflavin compounds, showing excellent inhibition of Mdm2 E3 ubiquitin ligase activity on the previous qualitative biological assay, to yield IC50 data.

The biological results have established a clear and logical structure-activity relationship comprising of an electron-withdrawing hydrophobic substituent at the nine position and the N10 phenyl being a prerequisite for activity as a Mdm2 inhibitor. Also meta substitution of the N10 phenyl improves activity against Mdm2 E3 ubiquitin ligase activity. Hit optimization has occurred with 10-(3-chlorophenyl)-9-trifluoromethyl-5-deazaflavin being thirty times more active than the previous identified hit compound, 10-(4-chlorophenyl)-7-nitro-5-deazaflavin.

Using the X-ray crystal structure of the Mdm2/MdmX heterodimer, an improved understanding of how Mdm2 acts as an E3 ubiquitin ligase is described and used to form a hypothesis of how 5-deazaflavin analogues function as inhibitors of Mdm2.

The work suggests the principle that small molecular weight compounds can inhibit E3 ubiquitin ligases as a possible anti-cancer therapy, and provide the foundation and framework for additional studies and investigation in a new and developing field of medicinal chemistry.

Item Type:Thesis (PhD)
Supervisors:Fischer, P.M.
Kellam, B.
Faculties/Schools:UK Campuses > Faculty of Science > School of Pharmacy
ID Code:1960
Deposited By:Mr Michael Dickens
Deposited On:13 Oct 2011 11:39
Last Modified:13 Oct 2011 11:39

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