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The measurement of receptor occupancy (RO) using positron emission tomography (PET) has been instrumental in guiding discovery and development of CNS directed therapeutics. We and others have investigated muscarinic acetylcholine receptor 4 (M4) positive allosteric modulators (PAMs) for the treatment of symptoms associated with neuropsychiatric disorders. In this article, we describe the synthesis, in vitro, and in vivo characterization of a series of central pyridinerelated M4 PAMs that can be conveniently radiolabeled with carbon-11 as PET tracers for the in vivo imaging of an allosteric binding site of the M4 receptor. We first demonstrated its feasibility by mapping the receptor distribution in mouse brain and confirming that a lead molecule 1 binds selectively to the receptor only in the presence of the orthosteric agonist carbachol. Through a competitive binding affinity assay and a number of physiochemical properties filters, several related compounds were identified as candidates for in vivo evaluation. These candidates were then radiolabeled with 11 C and studied in vivo in rhesus monkeys. This research eventually led to the discovery of the clinical radiotracer candidate [ 11 C]MK-6884.

Kutchukian, P. S. et al. (2017) Iterative focused screening with biological fingerprints identifies selective Asc-1 inhibitors distinct from traditional high throughput screening. ACS Chemical Biology, 12(2), pp. 519-527. (doi:10.1021/acschembio.6b00913) This is the author's final accepted version.There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/146530/

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Recent evidence suggests that some atypical antipsychotic drugs may protect against oxidative stress and consequent neurodegeneration by mechanisms that remain unclear. Using the neuron-like rat pheochromocytoma (PC-12) cell line, Clozapine and N-desmethylclozapine were tested for their ability to protect against cell death due to oxidative stress induced by hydrogen peroxide (H 2 O 2 ). These drugs demonstrated significant protection of PC-12 cells, as measured by both the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrasodium bromide (MTT) and Alamar Blue cell viability assays. However, neither viability assay detected a protective effect of Clozapine on human embryonic kidney (HEK293), rat primary cortical neurons, or human neuroblastoma (SHSY5Y) exposed to H 2 O 2 treatment. The mechanism of protection involves a PC-12 cell-specific differential response to H 2 O 2 treatment vs. the other cell lines. Pre-treatment with 250 μM or 125 μM diethyldithiocarbamate (DETC), a superoxide dismutase (SOD) inhibitor, unexpectedly showed protection of the PC-12 cells from H 2 O 2 treatment. Western blots revealed that Clozapine, Ndesmethylclozapine, and DETC reduce the phosphorylation of extracellular signal-regulated kinase (ERK) that is caused by H 2 O 2 exposure in PC-12 cells. In both HEK293 and SH-SY5Y cells, H 2 O 2 exposure did not increase ERK phosphorylation over control, demonstrating a different response to H 2 O 2 vs. PC-12 cells, and explaining why Clozapine could not protect these cells. Also, U0126, a specific MEK inhibitor, was able to protect PC-12 cells from H 2 O 2 exposure, showing that inhibiting ERK phosphorylation is sufficient to provide protection. Cumulatively, these results indicate that Clozapine, N-desmethylclozapine, DETC, and U0126 protect PC-12 cells by blocking the cell-type specific H 2 O 2 induced increase in ERK phosphorylation.

Novel oxazolobenzimidazoles are described as potent and selective positive allosteric modulators of the metabotropic glutamate receptor 2. The discovery of this class and optimization of its physical and pharmacokinetic properties led to the identification of potent and orally bioavailable compounds (20 and 21) as advanced leads. Compound 20 (TBPCOB) was shown to have robust activity in a PCP-induced hyperlocomotion model in rat, an assay responsive to clinical antipsychotic treatments for schizophrenia.