Preclinical pharmacokinetics and metabolism study of SCO-267, a GPR40 full agonist, in beagle dogs using ultra-high performance liquid chromatography coupled to tandem mass spectrometry

SCO-267 is a GPR40 full agonist that has been developed for the treatment of diabetes. To support its preclinical and clinical development, in this study, we developed an ultra-high performance liquid chromatography tandem mass spectrometric method for the determination of SCO-267 in dog plasma using cabozantinib as internal standard (IS). The chromatographic separation was obtained on a Waters acquity BEH C18 column (50 × 2.1 mm, i.d., 1.7 μm) and the detection was performed using Thermo TSQ triple quadrupole mass spectrometer with multiple reaction monitoring positive mode at m/z 615.3 > 230.1 for SCO-267 and m/z 502.5 > 323.3 for IS. The method was validated over the concentration range of 1-2,000 ng/ml with the lower limit of quantification of 1 ng/ml. The selectivity, linearity, precision and accuracy over this range were acceptable. The extraction recovery was more than 88.73% and no matrix effect was observed. SCO-267 was demonstrated to be stable during the storage and processing period. The new method was successfully applied to the pharmacokinetic study in beagle dogs following a single oral and intravenous administration. The oral bioavailability was 64.34%. In addition, the metabolites from dog liver microsomal incubation and plasma collected after an oral administration were identified by a UHPLC-HRMS method. The biotransformation pathways of SCO-267 involved oxygenation, O-demethylation, N-dealkylation and acyl glucuronidation.

Development & validation of LC-MS/MS assay for 5-amino-1-methyl quinolinium in rat plasma: Application to pharmacokinetic and oral bioavailability studies

5-Amino-1-methyl quinolinium (5-AMQ) is a potent Nicotinamide N-methyl transferase (NNMT) inhibitor. NNMT is an enzyme that catalyzes the N-methylation of the endogenous substrate nicotinamide, as well as exogenous xenobiotics. NNMT is fundamental to cellular metabolism; NNMT is overexpressed in select tissues (e.g., adipose tissue, skeletal muscle, etc.) in pathophysiological conditions, making it a clinically relevant target for drug development in several chronic diseases including obesity and diabetes. The objective of this study was to develop and validate a simple, sensitive, and reproducible liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of 5-AMQ in rat plasma and urine samples. 5-AMQ was extracted from plasma and urine by protein precipitation. Chromatographic separation was achieved using an ACE® Excel™ C₁₈ column (2 μm, 50 × 2.1 mm) with a binary gradient solvent system comprising of water (A) and acetonitrile (B) containing 0.1 % formic acid as the mobile phase. Analysis was performed using an API 4000 QTRAP hybrid triple quadruple mass spectrometer and multiple reaction monitoring (MRM) in positive mode at m/z transitions of 159.100 → 90.00 and 162.200 → 117.200 for 5-AMQ and the internal standard, respectively. The standard curves of 5-AMQ in rat urine and plasma samples were linear in the concentration range of 10-2500 ng/mL. The intra-day and inter-day precisions and accuracies for 5-AMQ at four concentration levels in rat plasma and urine samples were found to be within the 15 % FDA acceptance range. Similarly, the accuracy and precision of 5-AMQ quantification in samples diluted up to 20-fold using blank plasma were within the 15 % acceptable range. Furthermore, the extraction recoveries and matrix effects at three concentration levels of rat plasma samples ranged from 99.5 %-110.6 % and -6.1 %-14.1 %, respectively. 5-AMQ was stable in rat plasma samples subjected to standard storage, preparation, and handling conditions, with less than 15 % variation noted at two concentration levels. The validated, sensitive, and reproducible LC-MS/MS method for 5-AMQ in rat plasma and urine samples was effectively applied to a pharmacokinetic study in rats with IV and oral administration of 5-AMQ. 5-AMQ displayed substantial plasma exposures via IV and oral route, with a mean maximum plasma concentration of 2252 ng/mL after oral administration, mean area under the curve (AUC_0-∞) of 3708 h.ng/mL and 14431 h.ng/mL for the IV and oral groups, respectively, mean terminal elimination half-life of 3.80 ± 1.10 h and 6.90 ± 1.20 h respectively after intravenous and oral dose, and a good oral bioavailability (F % = 38.4).

An Isoquinolinium Dual Inhibitor of Cholinesterases and Amyloid β Aggregation Mitigates Neuropathological Changes in a Triple-Transgenic Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is a complex neurodegenerative disorder affecting millions of people worldwide. The underlying pathologic mechanisms of AD are unclear. Over the decades, the development of single target agent did not lead to any successful treatment for AD. A multitarget agent that could tackle more than one AD phenotype may be helpful as a treatment strategy. Cholinesterases (ChEs) including acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), are currently the drug targets with approved treatments. Moreover, amyloid beta (Aβ) deposition is a hallmark of AD that receives considerable attention. Herein, 9Q, a previously reported dual target inhibitor dealing with cholinergic dysfunction and amyloid deposition for AD treatment, has undergone thorough investigations. In vitro studies revealed that 9Q exhibited over 80% inhibition of ChE activity at 100 μM and more than 30% inhibition of Aβ aggregation at 1 mM concentration. Moreover 9Q was able to penetrate the blood-brain barrier (BBB) and enhance the cerebral acetylcholine level in triple transgenic AD (3xTg-AD) mice. Following one month treatment with 9Q, the amyloid burden and the cognitive deficits in 3xTg-AD mice were significantly ameliorated. It was observed that 9Q treatment mitigated synapse dysfunction, decreased amyloidogenic APP processing, and reduced the tau pathology in 3xTg-AD mice. Taken together, our results suggested that dual inhibition of cholinesterases and Aβ aggregation could be a promising approach in AD treatment.

Reductive amination derivatization for the quantification of garlic components by isotope dilution analysis

In this work, we synthesized internal standards for four garlic organosulfur compounds (OSCs) by reductive amination with ¹³C, D₂-formaldehyde, and developed an isotope dilution analysis method to quantitate these organosulfur components in garlic samples. Internal standards were synthesized for internal absolute quantification of S-allylcysteine (SAC), S-allylcysteine sulfoxide (alliin), S-methylcysteine (SMC), and S-ethylcysteine (SEC). We used a multiple reaction monitoring (MRM) to detect ¹³C, D₂-formaldehyde-modified OSCs by ultrahigh-performance liquid phase chromatography coupled with tandem mass spectrometry (UHPLC-MS/MS) and obtained MS spectra showing different ratios of ¹³C, D₂-formaldehyde-modified and H₂-formaldehyde-modified compounds. The resulting labeled and unlabeled OSCs were exhibited correlation coefficient (R²) ranged from 0.9989 to 0.9994, respectively. The average recoveries for four OSCs at three concentration levels ranged from 89% to 105%. By ¹³C, D₂-formaldehyde and sodium cyanoborohydride, the reductive amination-based method can be utilized to generate novel internal standard for isotope dilution and to extend the quantitative application.

SLM, a novel carbazole-based fluorophore attenuates okadaic acid-induced tau hyperphosphorylation via down-regulating GSK-3β activity in SH-SY5Y cells

Phosphorylated tau dissociates from microtubules and aggregates to form neurofibrillary tangles resulting in neuronal toxicity and cognitive deficits. Attenuating tau hyperphosphorylation is considered as an effective therapeutic approach for Alzheimer's disease (AD). From our previous study, SLM, a carbazole-based fluorophore prevents Aβ aggregation, reduced glycogen synthase kinase-3β (GSK-3β) activity and tau hyperphosphorylation in triple transgenic mouse model of AD. However, the mechanism by which SLM attenuates tau hyperphosphorylation warrants further investigation. In the current study, we intend to evaluate the effects of SLM against okadaic acid (OA)-induced tau hyperphosphorylation and microtubules instability in human neuroblastoma (SH-SY5Y) cells. The results showed that, SLM reduced the OA-induced cell neurotoxicity and tau hyperphosphorylation in SH-SY5Y cells. SLM treatment down-regulated GSK-3β activity. However, in the presence of GSK-3β inhibitor (SB216763, 10μM), SLM treatment could not reduce GSK-3β activity and tau hyperphosphorylation as compared with SB216763 treatment alone. Furthermore, SLM treatment also ameliorated OA-induced microtubules instability and cytoskeleton damage. Collectively, SLM attenuated OA-induced tau hyperphosphorylation via down-regulating GSK-3β activity in SH-SY5Y cells. Therefore, this study supports SLM as a potential compound for AD and other tau pathology-related neurodegenerative disorders.

Neuroprotective Effect of SLM, a Novel Carbazole-Based Fluorophore, on SH-SY5Y Cell Model and 3xTg-AD Mouse Model of Alzheimer's Disease

Amyloid β (Aβ) peptide aggregating to form a neurotoxic plaque, leading to cognitive deficits, is believed to be one of the plausible mechanisms for Alzheimer's disease (AD). Inhibiting Aβ aggregation is supposed to offer a neuroprotective effect to ameliorate AD. A previous report has shown that SLM, a carbazole-based fluorophore, binds to Aβ to inhibit the aggregation. However, it is not entirely clear whether the inhibition of Aβ aggregation alone would lead to the anticipated neuroprotective effects. In the current study, we intended to examine the protective action of SLM against Aβ-induced neurotoxicity in vitro and to evaluate if SLM can decrease the cognitive and behavioral deficits observed in triple transgenic AD mouse model (3xTg-AD). In the in vitro study, neurotoxicity induced by Aβ42 in human neuroblastoma (SH-SY5Y) cells was found to be reduced through the treatment with SLM. In the in vivo study, following one month SLM intraperitoneal injection (1, 2, and 4 mg/kg), 3xTg-AD mice were tested on Morris water maze (MWM) and Y-maze for their cognitive ability and sacrificed for biochemical estimations. Results show that SLM treatment improved the learning and memory ability in 3xTg-AD mice in MWM and Y-maze tasks. SLM also mitigated the amyloid burden by decreasing brain Aβ40 and Aβ42 levels and reduced tau phosphorylation, glycogen synthase kinase-3β activity, and neuro-inflammation. From our observations, SLM shows neuroprotection in SH-SY5Y cells against Aβ42 and also in 3xTg-AD mouse model by mitigating the pathological features and behavioral impairments.