Metabolism and pharmacokinetics of JM6 in mice: JM6 is not a prodrug for Ro-61-8048.

Understanding whether regulation of tryptophan metabolites can ameliorate neurodegeneration is of high interest to investigators. A recent publication describes 3,4-dimethoxy-N-(4-(3-nitrophenyl)-5-(piperidin-1-ylmethyl)thiazol-2-yl)benzenesulfonamide (JM6) as a novel prodrug for the kynurenine 3-monooxygenase (KMO) inhibitor 3,4-dimethoxy-N-(4-(3-nitrophenyl)thiazol-2-yl)benzenesulfonamide (Ro-61-8048) that elicits therapeutic effects in mouse models of Huntington's and Alzheimer's diseases (Cell 145:863-874, 2011). Our evaluation of the metabolism and pharmacokinetics of JM6 and Ro-61-8048 indicate instead that Ro-61-8048 concentrations in mouse plasma after JM6 administration originate from a Ro-61-8048 impurity (<0.1%) in JM6. After a 0.05 mg/kg Ro-61-8048 oral dose alone or coadministered with 10 mg/kg JM6 to mice, the Ro-61-8048 areas under the concentration-time curves (AUCs) from 0 to infinity were similar (4300 and 4900 nM × h, respectively), indicating no detectable contributions of JM6 metabolism to the Ro-61-8048 AUCs. JM6 was stable in incubations under acidic conditions and Ro-61-8048 was not a product of JM6 metabolism in vitro (plasma, blood, or hepatic models). Species differences in the quantitative rate of oxidative metabolism indicate that major circulating JM6 metabolite(s) in mice are unlikely to be major in humans: JM6 is rapidly metabolized via the piperidyl moiety in mouse (forming an iminium ion reactive intermediate) but is slowly metabolized in human (in vitro), primarily via O-dealkylation at the phenyl ring. Our data indicate that JM6 is not a prodrug for Ro-61-8048 and is not a potent KMO inhibitor.

It is time for us all to embrace person-centred language for people in prison and people who were formerly in prison.

The use of person-centred language is well accepted regarding substance use and infectious disease healthcare and research, and appropriate acronyms have become commonplace, e.g., "people who inject drugs (PWID)" has mostly replaced phrases like "injecting drugs users". However, the use of the term's 'prisoner' or 'prisoners' remains common. Although less common, terms such as 'offenders' and 'inmates' are also still used on occasion. This persists despite calls from people with lived experience of incarceration, and fellow academics, to stop using these terms. Given the considerable overlap between substance use, infectious diseases, and incarceration, in this commentary we discuss how they interact, including the stigma that is common to each. We propose that using person-centred language (i.e., people in prison or people formerly in prison) needs to become the default language used when presenting research related to people in prison or people formerly in prison. This is a much-needed step in efforts to overcome the continued stigma that people in prison face while incarcerated from prison officers and other employees, including healthcare providers. Likewise, overcoming stigma, including legalised discrimination, that follows people who were formerly in prison upon gaining their freedom is critical, as this impacts their health and related social determinants, including employment and housing.

Dynamics of Aß42 reduction in plasma, CSF and brain of rats treated with the γ-secretase modulator, GSM-10h.

BACKGROUND: Allosteric modulation of γ-secretase is an attractive therapeutic approach for the treatment of Alzheimer's disease. We recently identified a novel γ-secretase modulator, GSM-10h, which effectively lowers Aß42 production in cells and in amyloid precursor protein transgenic mice. OBJECTIVE: Here, we describe the in vivo characterization of GSM-10h in a model of endogenous Aß production. METHODS: Rats were administered orally with GSM-10h, and the effect on Aß levels in peripheral and central compartments was determined. In addition, the effect of GSM-10h on Notch processing was assessed. RESULTS: Acute administration of GSM-10h to rats causes a dose-dependent decrease in the level of Aß42 in plasma, CSF and brain, with little effect on the level of Aß40 in these compartments. The magnitude of Aß42 lowering in the CSF and brain was further enhanced upon sub-chronic administration of GSM-10h. No deleterious effect on Notch processing was evident in either of these studies. To further explore the dynamics of Aß42 reduction in peripheral and CNS compartments, a time course study was conducted. In all compartments, the decrease in Aß42 was greatest at 6 h after administration of GSM-10h. This decrease in Aß42 was maintained for 9-15 h, after which time Aß42 levels returned to baseline levels. Encouragingly, no rebound in Aß42 levels beyond baseline levels was observed. CONCLUSIONS: These findings support the γ-secretase modulator profile of GSM-10h, and highlight the utility of the rat for assessing the pre-clinical efficacy of γ-secretase modulators.

TASTPM mice expressing amyloid precursor protein and presenilin-1 mutant transgenes are sensitive to γ-secretase modulation and amyloid-ß42 lowering by GSM-10h.

BACKGROUND: Cleavage of the amyloid precursor protein (APP) by ß-site APP-cleaving enzyme and γ-secretase results in the generation of amyloid-ß (Aß) peptides that aggregate and deposit as senile plaques in brains of Alzheimer disease patients. Due to the fundamental role γ-secretase plays in the proteolysis of a number of proteins including Notch, pharmacological inhibition of γ-secretase has been associated with mechanism-based toxicities. Therefore, efforts have focussed on the modulation of γ-secretase activity to selectively decrease levels of Aß42 peptide while avoiding deleterious activity on Notch processing. OBJECTIVE: Here, we describe the in vitro and in vivo characterisation of a novel γ-secretase modulator, GSM-10h, and investigate the potential for shorter Aß peptides to induce neurotoxicity in rat primary cortical neurons. METHODS: The effect of GSM-10h on Aß levels was investigated in SH-SY5Y cells expressing mutant APP and in TASTPM mice expressing APP and presenilin-1 mutant transgenes. The effect of GSM-10h on Notch processing was also determined. RESULTS: In cells, GSM-10h decreased levels of Aß42 while concomitantly increasing levels of Aß38 in the absence of effects on Aß40 levels. In TASTPM mice, GSM-10h effectively lowered brain Aß42 and increased brain Aß38, with no effect on Notch signalling. Unlike Aß42, which causes neuronal cell death, neither Aß37 nor Aß38 were neurotoxic. CONCLUSIONS: These findings confirm GSM-10h exhibits the profile of a γ-secretase modulator. In addition, TASTPM mice are shown to be responsive to treatment with a γ-secretase modulator, thereby highlighting the utility of this bitransgenic mouse model in drug discovery efforts focussed on the development of γ-secretase modulators.

Tricyclic azepine derivatives as selective brain penetrant 5-HT6 receptor antagonists.

Starting from a benzazepine sulfonamide 5-HT(6) receptor antagonist lead with limited brain penetration, application of a strategy of conformational constraint and reduction of hydrogen bond donor count led to a novel series of tricyclic derivatives with high 5-HT(6) receptor affinity and excellent brain:blood ratios.

Lead optimization toward proof-of-concept tools for Huntington's disease within a 4-(1H-pyrazol-4-yl)pyrimidine class of pan-JNK inhibitors.

Through medicinal chemistry lead optimization studies focused on calculated properties and guided by X-ray crystallography and computational modeling, potent pan-JNK inhibitors were identified that showed submicromolar activity in a cellular assay. Using in vitro ADME profiling data, 9t was identified as possessing favorable permeability and a low potential for efflux, but it was rapidly cleared in liver microsomal incubations. In a mouse pharmacokinetics study, compound 9t was brain-penetrant after oral dosing, but exposure was limited by high plasma clearance. Brain exposure at a level expected to support modulation of a pharmacodynamic marker in mouse was achieved when the compound was coadministered with the pan-cytochrome P450 inhibitor 1-aminobenzotriazole.

Assessment of chloroquine treatment for modulating autophagy flux in brain of WT and HD mice.

BACKGROUND: Increasing mutant huntingtin (mHTT) clearance through the autophagy pathway may be a way to treat Huntington's disease (HD). Tools to manipulate and measure autophagy flux in brain in vivo are not well established. OBJECTIVE: To examine the in vivo pharmacokinetics and pharmacodynamics of the lysosomal inhibitor chloroquine (CQ) and the levels of selected autophagy markers to determine usefulness of CQ as a tool to study autophagy flux in brain. METHODS: Intraperitoneal injections of CQ were administered to WT and HD(Q175/Q175) mice. CQ levels were measured by LC-MS/MS in WT brain, muscle and blood at 4 to 24 hours after the last dose. Two methods of tissue preparation were used to detect by Western blot levels of the macroautophagy markers LC3 II and p62, the chaperone mediated autophagy receptor LAMP-2A and the late endosome/lysosomal marker RAB7. RESULTS: Following peripheral administration, CQ levels were highest in muscle and declined rapidly between 4 and 24 hours. In the brain, CQ levels were greater in the cortex than striatum, and levels persisted up to 24 hours post-injection. CQ treatment induced changes in LC3 II and p62 that were variable across regions and tissue preparations. HD(Q175/Q175) mice exposed to CQ had variable but diminished levels of LC3 II, p62 and LAMP-2A, and increased levels of RAB7. Higher levels of mHTT were found in the membrane compartment of CQ treated HD mice. CONCLUSION: Our findings suggest that the response of brain to CQ treatment, a blocker of autophagy flux, is variable and not as robust as it has been demonstrated in vitro, suggesting that CQ treatment has limitations for modulating autophagy flux in vivo. Alternative methods, compounds, and technologies need to be developed to further investigate autophagy flux in vivo, especially in the brain.

Nanofiber-based delivery of therapeutic peptides to the brain.

The delivery of therapeutic peptides and proteins to the central nervous system is the biggest challenge when developing effective neuropharmaceuticals. The central issue is that the blood-brain barrier is impermeable to most molecules. Here we demonstrate the concept of employing an amphiphilic derivative of a peptide to deliver the peptide into the brain. The key to success is that the amphiphilic peptide should by design self-assemble into nanofibers wherein the active peptide epitope is tightly wrapped around the nanofiber core. The nanofiber form appears to protect the amphiphilic peptide from degradation while in the plasma, and the amphiphilic nature of the peptide promotes its transport across the blood-brain barrier. Therapeutic brain levels of the amphiphilic peptide are achieved with this strategy, compared with the absence of detectable peptide in the brain and the consequent lack of a therapeutic response when the underivatized peptide is administered.

Design, synthesis, and biological evaluation of potent and selective class IIa histone deacetylase (HDAC) inhibitors as a potential therapy for Huntington's disease.

Inhibition of class IIa histone deacetylase (HDAC) enzymes have been suggested as a therapeutic strategy for a number of diseases, including Huntington's disease. Catalytic-site small molecule inhibitors of the class IIa HDAC4, -5, -7, and -9 were developed. These trisubstituted diarylcyclopropanehydroxamic acids were designed to exploit a lower pocket that is characteristic for the class IIa HDACs, not present in other HDAC classes. Selected inhibitors were cocrystallized with the catalytic domain of human HDAC4. We describe the first HDAC4 catalytic domain crystal structure in a "closed-loop" form, which in our view represents the biologically relevant conformation. We have demonstrated that these molecules can differentiate class IIa HDACs from class I and class IIb subtypes. They exhibited pharmacokinetic properties that should enable the assessment of their therapeutic benefit in both peripheral and CNS disorders. These selective inhibitors provide a means for evaluating potential efficacy in preclinical models in vivo.