| Summary: | The interactions between specific proteins (PPIs) is known to be critical for numerous biological processes, implicating them in many pathological conditions, thus modulation of PPIs has substantial therapeutic potential. The complexity, topography and, in some cases, the hydrophobic nature of the PPIs presents a considerable challenge. One important PPI of therapeutic interest, that has been implicated in the treatment of bi-polar and schizophrenia disorders, occurs between neuronal calcium sensor 1 (NCS1) and the dopamine receptor 2 (D2). The research detailed in this thesis describes the application of structure-based drug design (SBDD) to select small molecule compounds for synthesis and biophysical assessment against the NCS1 D2 target. The use of a structure-based drug design method, has been seen in previous PPI studies and uses a combination of techniques, including computational modelling used in conjunction with “hit identification” and ”hit to lead” optimisation processes in a drug discovery pipeline. The biophysical analyses of the first generation synthesised were hampered by problems associated with limited aqueous solubility, restricting the determination of accurate affinity values. Thus a second generation of ligands were developed with addition of solubilising groups to the scaffold, based on that of the compound 1-benzyl-N-((2-methoxy-4,6-dimethylpyridin-3-yl)methyl)-3,5-dimethyl-1H-pyrazole-4-carboxamide (Inhibitor 2). The second generation of compounds displayed improved aqueous solubility, in particular; 1-(4-chlorobenzyl)-3,5-dimethyl-N-((5-(morpholine-4-carbonyl)pyridin-3-yl)methyl)-1H-pyrazole-4-carboxamide (Inhibitor 5), presented the most promising hit. A fragment based approach was also investigated, adapting the SBDD approach by developing a computational pipeline to select 28 compounds from a library of 1137 for biophysical screening. A two-step biophysical screening protocol was developed; employing high throughput NMR techniques, five fragments were identified alongside a hit fragment candidate 5-methyl-3-phenyl-1H-pyrazole (4.21). This research presents two applications of an in silico screening protocol able to identify ligands targeting PPIs. Through verification via biophysical techniques, a number of compounds were determined as hits however, no affinity for the target was determined. This project highlights that despite some successes, many challenges remain in the development of targeting PPIs with small molecules.
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