Interleukin-2-inducible tyrosine kinase (ITK) is a member of the Tec family of non-receptor tyrosine kinases and plays an important role in T cell receptor signalling. Phosphorylation of ITK ultimately results in the release of several cytokines from T cells which are involved in the inflammatory response in asthmatic patients. ITK inhibitors could represent useful anti-inflammatory agents for severe asthma. This thesis describes the design and development of irreversible ITK inhibitors. It was envisaged that these compounds could provide a better duration of action in vivo compared to typical reversible inhibitors. After explaining first how irreversible ITK inhibition may be achieved, the medicinal chemistry undertaken to synthesise the designed molecules, and assess their activity profiles in various biological assays, is presented. Evidence of the covalent binding between some specific analogues and ITK is illustrated, the most explicit proof being a crystal structure of a kinase/inhibitor complex, clearly displaying a bond between the inhibitor and the cysteine residue present in the ITK active site. However, the early irreversible ITK inhibitors developed did not possess the required profile (cellular activity, duration of action) expected from an irreversible ITK inhibitor drug candidate. Three approaches are then described to improve the cellular activity of these irreversible ITK inhibitors. Firstly, the nature of the electrophilic moieties was investigated. Compounds presenting improved irreversible ITK inhibitor profiles (activities and rate of the covalent reaction) have been developed but these species could not be progressed further due to their high probability of toxicity issues in the body. Secondly, the positioning of the electrophilic group with respect to the ITK active site cysteine is then discussed; this strategy did not lead to any improved compounds. Finally, moving to a chemically more challenging pyridine template provided inhibitors with enhanced non-covalent ITK recognition. Optimisation of the compounds from this series provided irreversible inhibitors with the required in vitro and in vivo activity profiles for a drug candidate within our laboratories. The progression of the lead covalent ITK inhibitor from this research programme was ultimately halted due to toxicology findings from a 14 day rat study. The final part of the thesis studies the Buchwald-Hartwig amination reaction used in the synthetic route leading to the best covalent ITK inhibitors. This coupling required 30 mol % of palladium catalyst, which, on large scale, represents a significant amount of metal waste. The investigation of this coupling strongly suggested that the substrates involved in the reaction were poisoning the catalyst. The final results from this study indicate that an alternative palladium catalyst, allowing full conversion to the required product at room temperature, has been identified.
|Date of Award||1 Dec 2013|
- University Of Strathclyde