James Peter Sinclair

Cellular Models of Aggregation-dependent Template-directed Proteolysis to Characterize Tau Aggregation Inhibitors for Treatment of Alzheimer Disease

Background: Tau aggregation inhibitors could treat Alzheimer disease. Results: Stable reduced forms of leucomethylthioninium (LMTX®) are active in blocking prion-like Tau aggregation in novel cellular models. Conclusion: The intracellular Ki (0.12 μm) is comparable with brain levels required for clinical benefit. Significance: LMTX® could treat Alzheimer disease. Alzheimer disease (AD) is a degenerative tauopathy characterized by aggregation of Tau protein through the repeat domain to form intraneuronal paired helical filaments (PHFs). We report two cell models in which we control the inherent toxicity of the core Tau fragment. These models demonstrate the properties of prion-like recruitment of full-length Tau into an aggregation pathway in which template-directed, endogenous truncation propagates aggregation through the core Tau binding domain. We use these in combination with dissolution of native PHFs to quantify the activity of Tau aggregation inhibitors (TAIs). We report the synthesis of novel stable crystalline leucomethylthioninium salts (LMTX®), which overcome the pharmacokinetic limitations of methylthioninium chloride. LMTX®, as either a dihydromesylate or a dihydrobromide salt, retains TAI activity in vitro and disrupts PHFs isolated from AD brain tissues at 0.16 μm. The Ki value for intracellular TAI activity, which we have been able to determine for the first time, is 0.12 μm. These values are close to the steady state trough brain concentration of methylthioninium ion (0.18 μm) that is required to arrest progression of AD on clinical and imaging end points and the minimum brain concentration (0.13 μm) required to reverse behavioral deficits and pathology in Tau transgenic mice.

New tetrahydro-1,2,4,5-tetrazinan-3-ones and oxoverdazyl free radicals

A series of tetrahydro-1,2,4,5-tetrazinan-3-ones have been prepared by the reaction of carbonic acid bis (1-methylhydrazide) with aromatic aldehydes. These were oxidised to oxoverdazyl free radicals and used immediately for ESR spectroscopy studies that indicate that the unpaired electron is delocalised over the verdazyl ring. The ESR spectra can be very well simulated considering hyperfine couplings with the four nitrogen atoms of the verdazyl ring and the six hydrogen atoms of the two methyl groups bonded to it.

Mimicking biological systems through modular control of solvation : a synthetic receptor that binds in both water or chloroform

Two receptors are described which are designed to complex barbiturates and cyanuric acids. The functional groups at the binding pocket are polar and are designed to enable guest exchange from water to occur by a dispersion of the host. One receptor has a charged binding pocket lined with two phosphate groups resembling a surfactant. Evidence for the partial extraction of diethylbarbituric acid from water is presented. The more polar guest sodium alloxan 5-f-sulfonatophenylhydrazone was not complexed. The receptors were both used to solubilise two insoluble bis-isocyanuric acids by forming 2:1 complexes in chloroform.

Co-operative stabilisation of a 15-component nanostructure

2-Amino-4-(4-tert-butylphenylamino)-6-{4-[(4-pyridyl)ethynyl]phenylamino}-1,3,5-triazine was synthesised and mixed with dibutylbarbituric acid in CDCl3 to study rosette formation. The formation of a double decker rosette aggregate was studied by complexation of the pyridyl groups to a zinc containing porphyrin dimer.