Novel inhibitors of LIM kinase and GABAAR-α5 to enable therapeutics in neurological disorders

Ashall-Kelly, Alexander 2023. Novel inhibitors of LIM kinase and GABAAR-α5 to enable therapeutics in neurological disorders. PhD Thesis, Cardiff University. Item availability restricted.

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Abstract

The thesis herein describes novel approaches to targeting key biological markers identified in the pathology of two disparate inherited neurological diseases; Fragile X Syndrome and Huntington’s Disease. Fragile X syndrome (FXS) is a neurological developmental disorder characterised by severe intellectual disability, behavioural issues and autism. LIM kinase 1 isoform (LIMK1), a master regulator of actin dynamics and synapse structure, was identified in the pathogenesis of FXS as an attractive target for FXS disease modifying medicines. Publication of TH257 (19), a kinome selective, allosteric inhibitor of LIMK1 and 2 presented a promising starting point for further investigation into small molecule LIMK inhibitors. This research considered novel targets based upon TH257 (19) with the aim to explore structural activity relationships (SAR) driving the potency, LIMK isoform selectivity profile and poor microsomal clearance displayed in this series. Novel targets with modifications in two key areas were designed and a telescoped synthetic methodology developed which efficiently generated target compounds in a parallel synthesis fashion. A total of 33 novel compounds were synthesised and biologically evaluated. Of the compounds tested, 5 analogues achieved reasonable nanomolar potency, comparable with the parent compound, TH257 (19), however no evidence of LIMK1 versus LIMK2 selectivity was demonstrated, with the activity profile of this series remaining unchanged. Modulation of in vitro microsomal stability was achieved however clearance remained high for those analogues evaluated. Huntington’s disease (HD) is an hereditary neurodegenerative disease characterised by physical, emotional and cognitive decline over a number of years. Onset of the disease significantly impacts a patients ability to work, undertake everyday tasks and process information, with disease progression eventually leading to immobility and mortality. The v onset of cognitive decline can commence 15-20 years prior to an inability to physically undertake tasks, significantly impacting the quality of life of the patient. Alpha 5 subunit containing γ-Aminobutyric acid receptors (GABAAR-α5) have been associated with cognitive function and selective GABAAR-α5 negative allosteric modulators (NAMs) enhance cognition in preclinical species. In-house development of a lead series generated compound 56, which exhibited low nanomolar potency and selectivity versus other GABAA receptors. In vivo dose escalation studies indicated poor plasma exposure potentially driven by the low solubility of these compounds and hence the aim for this research was to identify watersoluble analogues by modifying previously under explored structural regions of the lead compound (56) while maintaining the potency and selectivity profile over other GABAARs. Novel targets were designed and a convergent synthetic strategy, utilising a one-pot telescoped isoxazole synthesis, was employed to efficiently synthesise 19 final compounds with modifications in two structural regions. Biological evaluation of these compounds confirmed a number of modifications were not only tolerated but improved upon the potency and functional efficacy of the parent compound 56. Selectivity for GABAAR-α5 over off-target GABAAR isoforms was maintained however no vast improvements in solubility was demonstrated with the analogues exemplified. Example 78 is also reported which displayed an unexpected NAM to PAM switch with a modification of the isoxazole methyl region.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > Q Science (General)
Date of First Compliant Deposit:	18 April 2024
Last Modified:	19 Apr 2024 08:06
URI:	https://orca.cardiff.ac.uk/id/eprint/168154

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