A novel liquid chromatography/tandem mass spectrometry based depletion method for measuring red blood cell partitioning of pharmaceutical compounds in drug discovery

ADME/PK Insights of Crocetin: A Molecule Having an Unusual Chemical Structure with Druglike Features

Crocetin is a promising phyto-based molecule to treat Alzheimer's disease (AD). The chemical structure of crocetin is incongruent with various standard structural features of CNS drugs. As poor pharmacokinetic behavior is the major hurdle for any candidate to become a drug, we elucidated its druggable characteristics by implementing in silico, in vitro, and in vivo approaches, as limited ADME/PK information is available. Results demonstrate several attributes of crocetin based on rules of drug-likeness, lipophilicity, pKa, P-gp inhibitory activity, plasma stability, RBC partitioning, metabolic stability, CYP inhibitory action, blood-brain barrier (BBB) permeability, oral bioavailability, and pharmacokinetic interaction with marketed anti-Alzheimer's drugs (memantine, donepezil, galantamine, and rivastigmine). However, aqueous solubility, chemical stability, plasma protein binding, and P-gp induction are some concerns associated with this molecule that should be taken into consideration during its further development. Overall results indicate favorable ADME/PK behavior and potential druggable candidature of crocetin.

Monomethyl Auristatin E (MMAE), a Payload for Multiple Antibody Drug Conjugates (ADCs), Demonstrates Differential Red Blood Cell Partitioning Across Human and Animal Species

Background: Monomethyl auristatin E (MMAE) has been used as a payload for several Food and Drug Administration (FDA) approved antibody-drug conjugates (ADCs). It is known that MMAE is released from the ADC following binding, internalization and proteolytic degradation in target tissues. A striking discrepancy in systemic MMAE levels has been observed across species with 50-fold higher MMAE levels in human than that in rodents when normalized by ADC dose with unknown mechanism.Hypothesis and purpose: Multiple factors could affect systemic MMAE levels such as production and elimination of unconjugated MMAE following ADC dosing. In this study, we have explored whether MMAE displays differential red blood cell (RBC) partitioning across species that may contribute to the different MMAE levels seen between human and animals.Experiments: To determine MMAE RBC partitioning, tritium labeled MMAE ([3H]-MMAE) was incubated in whole blood from mice, rats, monkeys and humans in vitro, then RBC partitioning was determined and compared across species. To test whether MMAE released from the ADC would show any difference in RBC partitioning, pinatuzumab vedotin or polatuzumab vedotin was administered to mice, rats, and monkeys. MMAE levels were measured in both blood and plasma, and the ratios of MMAE levels were calculated as blood-to-plasma ratio (in vivo RBC partitioning).Results: Our in vitro data showed that unconjugated MMAE has a species-dependent RBC partitioning with strong RBC partitioning in mouse, rat, followed by monkey blood, whereas minimal RBC partitioning was seen in human blood. Incubation of 2 nM of MMAE in mouse blood resulted in a blood-to-plasma ratio of 11.8 ± 0.291, followed by rat, monkey, and human at 2.36 ± 0.0825, 1.57 ± 0.0250, and 0.976 ± 0.0620, respectively. MMAE RBC partitioning is also concentration-dependent, with an inverse relationship between RBC partitioning and MMAE concentration (higher RBC partitioning at lower concentration). In vivo dosing of pinatuzumab vedotin in mouse displayed systemic MMAE at about a 5-fold higher blood concentration compared to plasma concentration once MMAE reached a pseudo-equilibrium, while systemic MMAE from blood and plasma concentration showed a 1.65-fold difference in rat.Implication and conclusion: These data demonstrated that MMAE has a distinct RBC partitioning across different species, which may contribute to, at least in part, to the differential in the systemic MMAE levels observed in vivo between preclinical and clinical studies. These findings highlight the importance of fully characterizing the ADME properties of both the ADC and its payload, to enable better translation from animals to human for ADC development.

Predictions of tissue concentrations of myclobutanil, oxyfluorfen, and pronamide in rat and human after oral exposures via GastroPlusTM physiologically based pharmacokinetic modelling

Heritage agrochemicals like myclobutanil, oxyfluorfen, and pronamide, are extensively used in agriculture, with well-established studies on their animal toxicity. Yet, human toxicity assessment relies on conventional human risk assessment approaches including the utilization of animal-based ADME (Absorption, Distribution, Metabolism, and Excretion) data. In recent years, Physiologically Based Pharmacokinetic (PBPK) modelling approaches have played an increasing role in human risk assessment of many chemicals including agrochemicals. This study addresses the absence of PBPK-type data for myclobutanil, oxyfluorfen, and pronamide by generating in vitro data for key input PBPK parameters (Caco-2 permeability, rat plasma binding, rat blood to plasma ratio, and rat liver microsomal half-life), followed by generation of PBPK models for these three chemicals via the GastroPlusTM software. Incorporating these experimental input parameters into PBPK models, the prediction accuracy of plasma AUC (area under curve) was significantly improved. Validation against rat oral administration data demonstrated substantial enhancement. Steady-state plasma concentrations (Css) of pronamide aligned well with published data using measured PBPK parameters. Following validation, parent-based tissue concentrations for these agrochemicals were predicted in humans and rats after single or 30-day repeat exposure of 10 mg/kg/day. These predicted concentrations contribute valuable information for future human toxicity risk assessments of these agrochemicals.

Challenges and Opportunities for In Vitro-In Vivo Extrapolation of Aldehyde Oxidase-Mediated Clearance: Toward a Roadmap for Quantitative Translation

Underestimation of aldehyde oxidase (AO)-mediated clearance by current in vitro assays leads to uncertainty in human dose projections, thereby reducing the likelihood of success in drug development. In the present study we first evaluated the current drug development practices for AO substrates. Next, the overall predictive performance of in vitro-in vivo extrapolation of unbound hepatic intrinsic clearance (CLint,u) and unbound hepatic intrinsic clearance by AO (CLint,u,AO) was assessed using a comprehensive literature database of in vitro (human cytosol/S9/hepatocytes) and in vivo (intravenous/oral) data collated for 22 AO substrates (total of 100 datapoints from multiple studies). Correction for unbound fraction in the incubation was done by experimental data or in silico predictions. The fraction metabolized by AO (fmAO) determined via in vitro/in vivo approaches was found to be highly variable. The geometric mean fold errors (gmfe) for scaled CLint,u (mL/min/kg) were 10.4 for human hepatocytes, 5.6 for human liver cytosols, and 5.0 for human liver S9, respectively. Application of these gmfe's as empirical scaling factors improved predictions (45%-57% within twofold of observed) compared with no correction (11%-27% within twofold), with the scaling factors qualified by leave-one-out cross-validation. A road map for quantitative translation was then proposed following a critical evaluation on the in vitro and clinical methodology to estimate in vivo fmAO In conclusion, the study provides the most robust system-specific empirical scaling factors to date as a pragmatic approach for the prediction of in vivo CLint,u,AO in the early stages of drug development. SIGNIFICANCE STATEMENT: Confidence remains low when predicting in vivo clearance of AO substrates using in vitro systems, leading to de-prioritization of AO substrates from the drug development pipeline to mitigate risk of unexpected and costly in vivo impact. The current study establishes a set of empirical scaling factors as a pragmatic tool to improve predictability of in vivo AO clearance. Developing clinical pharmacology strategies for AO substrates by utilizing mass balance/clinical drug-drug interaction data will help build confidence in fmAO.

Shared learning from a physiologically based pharmacokinetic modeling strategy for human pharmacokinetics prediction through retrospective analysis of Genentech compounds

The quantitative prediction of human pharmacokinetics (PK) including the PK profile and key PK parameters are critical for early drug development decisions, successful phase I clinical trials, and the establishment of a range of doses to enable phase II clinical dose selection. Here, we describe an approach employing physiologically based pharmacokinetic (PBPK) modeling (Simcyp) to predict human PK and to validate its performance through retrospective analysis of 18 Genentech compounds for which clinical data are available. In short, physicochemical parameters and in vitro data for preclinical species were integrated using PBPK modeling to predict the in vivo PK observed in mouse, rat, dog, and cynomolgus monkey. Through this process, the in vitro to in vivo extrapolation (IVIVE) was determined and then incorporated into PBPK modeling in order to predict human PK. Overall, the prediction obtained using this PBPK-IVIVE approach captured the observed human PK profiles of the compounds from the dataset well. The predicted Cmax was within 2-fold of the observed Cmax for 94% of the compounds while the predicted area under the curve (AUC) was within 2-fold of the observed AUC for 72% of the compounds. Additionally, important IVIVE trends were revealed through this investigation, including application of scaling factors determined from preclinical IVIVE to human PK prediction for each molecule. Based upon the analysis, this PBPK-based approach now serves as a practical strategy for human PK prediction at the candidate selection stage at Genentech.

Pyrazolopyrimidinone Based Selective Inhibitors of PDE5 for the Treatment of Erectile Dysfunction

Continuing research with our earlier finding of sildenafil based analogs in the search of new inhibitors of PDE5 for erectile dysfunction suggested that there is a scope of modifications at N-methylpiperazine ring with hydrophobic region followed by hydrogen bond donor or acceptor region. However, the leads identified earlier had some limitations like poor pharmacokinetic (PK) profile, low aqueous solubility and poor bioavailability. In this direction, a new series of sildenafil based analogs were designed, synthesized and screened for their PDE5 inhibitory activity. In this series compound 18 was found to have excellent in vitro activity with selectivity towards PDE5 isozyme, also the in vivo activity and pharmacokinetic profile was excellent. The cyp inhibition and CaCO2 permeability was also excellent for compound 18.

Vancomycin Sequestration in ST Filters: An In Vitro Study

BACKGROUND

Sequestration of vancomycin in ST^® filters used in continuous renal therapy is a pending question. Direct vancomycin-ST^® interaction was assessed using the in vitro NeckEpur^® technology.

METHOD

ST150^® filter and Prismaflex dialyzer, Baxter-Gambro, were used. Two modes were assessed in duplicate: (i) continuous diafiltration (CDF): 4 L/h, (ii) continuous dialysis (CD): 2.5 L/h post-filtration.

RESULTS

The mean initial vancomycin concentration in the central compartment (CC) was 51.4 +/- 5.0 mg/L. The mean percentage eliminated from the CC over 6 h was 91 +/- 4%. The mean clearances from the CC by CDF and CD were 2.8 and 1.9 L/h, respectively. The mean clearances assessed using cumulative effluents were 4.4 and 2.2 L/h, respectively. The mean percentages of the initial dose eliminated in the effluents from the CC by CDF and CD were 114 and 108% with no detectable sequestration of vancomycin in both modes of elimination.

DISCUSSION

Significant sequestration adds a clearance to that provided by CDF and CD. The study provides multiple evidence from the CC, the filter, and the effluents of the lack of an increase in total clearance in comparison with the flow rates without significant sequestration in the ST^® filter comparing cumulative effluents to the initial dose in the CC.

CONCLUSIONS

There is no evidence ST^® filters directly sequestrate vancomycin.

Discovery of novel arylpiperazine-based DA/5-HT modulators as potential antipsychotic agents – Design, synthesis, structural studies and pharmacological profiling

Schizophrenia is a mental disorder with a complex pathomechanism involving many neurotransmitter systems. Among the currently used antipsychotics, classical drugs acting as dopamine D₂ receptor antagonists, and drugs of a newer generation, the so-called atypical antipsychotics, can be distinguished. The latter are characterized by a multi-target profile of action, affecting, apart from the D₂ receptor, also serotonin receptors, in particular 5-HT_2A and 5-HT_1A. Such profile of action is considered superior in terms of both efficacy in treating symptoms and safety. In the search for new potential antipsychotics of such atypical receptor profile, an attempt was made to optimize the arylpiperazine based virtual hit, D2AAK3, which in previous studies displayed an affinity for D₂, 5-HT_1A and 5-HT_2A receptors, and showed antipsychotic activity in vivo. In this work, we present the design of D2AAK3 derivatives (1-17), their synthesis, and structural and pharmacological evaluation. The obtained compounds show affinities for the receptors of interest and their efficacy as antagonists/agonists towards them was confirmed in functional assays. For the selected compound 11, detailed structural studies were carried out using molecular modeling and X-ray methods. Additionally, ADMET parameters and in vivo antipsychotic activity, as well as influence on memory and anxiety processes were evaluated in mice, which indicated good therapeutic potential and safety profile of the studied compound.

Analysis of Time-Dependent Pharmacokinetics Using In Vitro-In Vivo Extrapolation and Physiologically Based Pharmacokinetic Modeling

SCR430, a sorafenib derivative, is an investigational drug exhibiting anti-tumor action. This study aimed to have a mechanistic understanding of SCR430's time-dependent pharmacokinetics (TDPK) through an ex vivo study combined with an in vitro-in vivo extrapolation (IVIVE) and physiologically based pharmacokinetic (PBPK) modeling. A non-compartmental pharmacokinetic analysis was performed after intravenous SCR430 administration in female Sprague-Dawley rats for a control group (no treatment), a vehicle group (vehicle only, 14 days, PO), and a repeated-dosing group (SCR430, 30 mg/kg/day, 14 days, PO). In addition, hepatic uptake and metabolism modulation were investigated using isolated hepatocytes from each group of rats. The minimal PBPK model based on IVIVE was constructed to explain SCR430's TDPK. Repeated SCR430 administration decreased the systemic exposure by 4.4-fold, which was explained by increased hepatic clearance (4.7-fold). The ex vivo study using isolated hepatocytes from each group suggested that the increased hepatic uptake (9.4-fold), not the metabolic activity, contributes to the increased hepatic clearance. The minimal PBPK modeling based on an ex vivo study could explain the decreased plasma levels after the repeated doses. The current study demonstrates the TDPK after repeated dosing by hepatic uptake induction, not hepatic metabolism, as well as the effectiveness of an ex vivo approach combined with IVIVE and PBPK modeling to investigate the TDPK.

Development of a biomarker to monitor target engagement after treatment with dihydroorotate dehydrogenase inhibitors

Dihydroorotate dehydrogenase (DHODH) catalyzes a key step in pyrimidine biosynthesis and has recently been validated as a therapeutic target for malaria through clinical studies on the triazolopyrimidine-based Plasmodium DHODH inhibitor DSM265. Selective toxicity towards Plasmodium species could be achieved because malaria parasites lack pyrimidine salvage pathways, and DSM265 selectively inhibits Plasmodium DHODH over the human enzyme. However, while DSM265 does not inhibit human DHODH, it inhibits DHODH from several preclinical species, including mice, suggesting that toxicity could result from on-target DHODH inhibition in those species. We describe here the use of dihydroorotate (DHO) as a biomarker of DHODH inhibition. Treatment of mammalian cells with DSM265 or the mammalian DHODH inhibitor teriflunomide led to increases in DHO where the extent of biomarker buildup correlated with both dose and inhibitor potency on DHODH. Treatment of mice with leflunomide (teriflunomide prodrug) caused a large dose-dependent buildup of DHO in blood (up to 16-fold) and urine (up to 5,400-fold) that was not observed for mice treated with DSM265. Unbound plasma teriflunomide levels reached 20-85-fold above the mouse DHODH IC50, while free DSM265 levels were only 1.6-4.2-fold above, barely achieving ∼ IC90 concentrations, suggesting that unbound DSM265 plasma levels are not sufficient to block the pathway in vivo. Thus, any toxicity associated with DSM265 treatment in mice is likely caused by off-target mechanisms. The identification of a robust biomarker for mammalian DHODH inhibition represents an important advance to generally monitor for on-target effects in preclinical and clinical applications of DHODH inhibitors used to treat human disease.

Drug clearance by aldehyde oxidase: can we avoid clinical failure?

Despite increased awareness of aldehyde oxidase (AO) as a major drug-metabolising enzyme, predicting the pharmacokinetics of its substrates remains challenging. Several drug candidates have been terminated due to high clearance, which were subsequently discovered to be AO substrates. Even retrospective extrapolation of human clearance, from models more sensitive to AO activity, often resulted in underprediction.The questions of the current work thus were: Is there an acceptable degree of in vitro AO metabolism that does not result in high in vivo human clearance? And, if so, how can this be predicted?We built an in vitro/in vivo correlation using known AO substrates, combining multiple in vitro parameters to calculate the blood metabolic clearance mediated by AO (CLb_AO). This value was compared with observed blood clearance (CLb_-obs), establishing cut-off CLb_AO values, to discriminate between low and high CLb_-obs. The model was validated using additional literature compounds, and CLb_-obs was predicted in the correct category.This simple, categorical, semi-quantitative yet multi-factorial model is readily applicable in drug discovery. Further, it is valuable for high-clearance compounds, as it predicts the CLb group, rather than an exact CLb value, for the substrates of this poorly-characterised enzyme.

Preclinical pharmacokinetics, CYP phenotyping, and tissue distribution study of novel anti-breast cancer candidate S-011-1559

S-011-1559 is a tyrosine-derived novel benzoxazine CDRI molecule targeted to the estrogen-related receptor (ER-α/β) modulator in breast cancer. To explore the pharmacokinetics of S-011-1559, a selective and sensitive bioanalytical method using LC-MS/MS was established and validated in different biological matrices of female rats.Blood-to-plasma ratio and plasma protein binding (PPB) of S-011-1559 was found to be <1 and >97% in both rats and humans respectively. The human serum albumin (HSA) and alpha-1-acid glycoprotein (AAG) binding was found in the range of >68 to 45% and >14% respectively. Half-life and intrinsic clearance by microsomal stability study were found to be 28.83 min and 0.05 mL/min/mg in rats, 78.35 min and 0.036 mL/min/mg in humans respectively. The IC₅₀ value of S-011-1559 against CYP isoforms was revealed to moderately inhibit CYP2D6 by a reversible noncompetitive mechanism.Tissue distribution of S-011-1559 on single intravenous injection at 2mg/kg was found in the order of C lungs > C mammary gland > C spleen > C heart > C kidney > C liver > C brain.The data from the present study provides crucial information about S-011-1559 for further development as a novel potential drug candidate in modulating ER-α/β receptors of lung and breast neoplasia.

Prediction of Pharmacokinetics of IDP-73152 in Humans Using Physiologically-Based Pharmacokinetics

IDP-73152, a novel peptide deformylase inhibitor with an antibacterial effect against Gram-positive bacteria, is in phase I development. The objective of this study was to develop a physiologically-based pharmacokinetic model (PBPK) for IDP-73152 in animals, and to extend the model to humans. Biopharmaceutical properties of IDP-73152 are determined using in vitro/in vivo experimentations for the PBPK model. A transit model consisting of gastrointestinal segments is applied for an estimation of the intestinal absorption kinetics. The PBPK model of IDP-73152 in rats is able to appropriately predict the plasma concentration–time profiles after the administration of IDP-73152 at different doses and by different routes (combined absolute average fold error (cAAFE), 1.77). The model is also found to be adequate in predicting the plasma concentration–time profiles of IDP-73152 in mice (cAAFE 1.59) and dogs (cAAFE 1.42). Assuming the oral administration of IDP-73152 to humans at doses of 640 and 1280 mg, the model is able to reproduce the concentration–time profiles obtained in humans (cAAFE 1.38); therefore, these observations indicate that the PBPK model used for IDP-73152 is applicable to animal species and humans. This model may be useful in predicting efficacious doses of IDP-73152 for the management of infectious disease in humans.

Application of physiologically based pharmacokinetic modelling for the prediction of drug-drug interactions involving anlotinib as a perpetrator of cytochrome P450 enzymes

Anlotinib is a small molecule of novel tyrosine kinase inhibitor initially approved to treat non-small cell lung cancer in China. Drug-drug interaction (DDI) is an extrinsic factor important for the appropriate use of anlotinib in clinical practice. In vitro experiments demonstrated that anlotinib is a substrate of cytochrome P450 (CYP) enzymes and moderate inhibitor of several common ones; however, no clinical DDI studies have been performed to investigate inhibitory effects of anlotinib on these CYP enzymes. Thus, its drug label recommends avoiding co-administration with substrates of these enzymes, which have narrow therapeutic windows. In this study, we performed a CYP450 inhibition study, followed by gathering in vitro and clinical pharmacokinetic data to build the first physiologically based pharmacokinetic (PBPK) model of anlotinib. The verified model was subsequently used to predict the DDI mediated by anlotinib. As a result, the marginal plasma exposure changes of typical CYP3A and CYP2C9 substrates were less than the bioequivalence threshold, indicating that anlotinib has a very low potential of causing clinically meaningful DDI through the inhibition of several major CYP enzymes. According to the FDA's latest guideline on DDI, the established model with the simulation results may support the revision of anlotinib labelling without further clinical studies, lifting unnecessary restrictions on anlotinib regimens.

The Lack of Contribution of 7-Hydroxymitragynine to the Antinociceptive Effects of Mitragynine in Mice: A Pharmacokinetic and Pharmacodynamic Study

Kratom (Mitragyna speciosa), a Southeast Asian tree, has been used for centuries in pain relief and mitigation of opium withdrawal symptoms. Mitragynine (MTG), the major kratom alkaloid, is being investigated for its potential to provide analgesia without the deleterious effects associated with typical opioids. Concerns have been raised regarding the active metabolite of MTG, 7-hydroxymitragynine (7HMG), which has higher affinity and efficacy at µ-opioid receptors than MTG. Here we investigated the hotplate antinociception, pharmacokinetics, and tissue distribution of MTG and 7HMG at equianalgesic oral doses in male and female C57BL/6 mice to determine the extent to which 7HMG metabolized from MTG accounts for the antinociceptive effects of MTG and investigate any sex differences. The mechanism of action was examined by performing studies with the opioid receptor antagonist naltrexone. A population pharmacokinetic/pharmacodynamic model was developed to predict the behavioral effects after administration of various doses of MTG and 7HMG. When administered alone, 7HMG was 2.8-fold more potent than MTG to produce antinociception. At equivalent effective doses of MTG and 7HMG, there was a marked difference in the maximum brain concentration of 7HMG achieved, i.e., 11-fold lower as a metabolite of MTG. The brain concentration of 7HMG observed 4 hours post administration, producing an analgesic effect <10%, was still 1.5-fold higher than the maximum concentration of 7HMG as a metabolite of MTG. These results provide strong evidence that 7HMG has a negligible role in the antinociceptive effects of MTG in mice. SIGNIFICANCE STATEMENT: Mitragynine (MTG) is being investigated for its potential to aid in pain relief, opioid withdrawal syndrome, and opioid use disorder. The active metabolite of MTG, 7-hydroxymitragynine (7HMG), has been shown to have abuse potential and has been implicated in the opioid-like analgesic effect after MTG administration. The results of this study suggest a lack of involvement of 7HMG in the antinociceptive effects of MTG in mice.

Evaluation of the Pharmacokinetics of the Pancreastatin Inhibitor PSTi8 Peptide in Rats: Integration of In Vitro and In Vivo Findings

PSTi8 is a pancreastatin inhibitory peptide that is effective in the treatment of diabetic models. This study investigates the pharmacokinetic (PK) properties of PSTi8 in Sprague Dawley rats, for the first time. In vitro and in vivo PK studies were performed to evaluate the solubility, stability in plasma and liver microsomes, plasma protein binding, blood-plasma partitioning, bioavailability, dose proportionality, and gender difference in PK. Samples were analyzed using the validated LC-MS/MS method. The solubility of PSTi8 was found to be 9.30 and 25.75 mg/mL in simulated gastric and intestinal fluids, respectively. The protein binding of PSTi8 was estimated as >69% in rat plasma. PSTi8 showed high stability in rat plasma and liver microsomes and the blood-plasma partitioning was >2. The bioavailability of PSTi8 after intraperitoneal and subcutaneous administration was found to be 95.00 ± 12.15 and 78.47 ± 17.72%, respectively, in rats. PSTi8 showed non-linear PK in dose proportionality studies, and has no gender difference in the PK behavior in rats. The high bioavailability of PSTi8 can be due to high water solubility and plasma protein binding, low clearance and volume of distribution. Our in vitro and in vivo findings support the development of PSTi8 as an antidiabetic agent.

The blood-to-plasma ratio and predicted GABAA-binding affinity of designer benzodiazepines

PURPOSE

The number of benzodiazepines appearing as new psychoactive substances (NPS) is continually increasing. Information about the pharmacological parameters of these compounds is required to fully understand their potential effects and harms. One parameter that has yet to be described is the blood-to-plasma ratio. Knowledge of the pharmacodynamics of designer benzodiazepines is also important, and the use of quantitative structure-activity relationship (QSAR) modelling provides a fast and inexpensive method of predicting binding affinity to the GABA_A receptor.

METHODS

In this work, the blood-to-plasma ratios for six designer benzodiazepines (deschloroetizolam, diclazepam, etizolam, meclonazepam, phenazepam, and pyrazolam) were determined. A previously developed QSAR model was used to predict the binding affinity of nine designer benzodiazepines that have recently appeared.

RESULTS

Blood-to-plasma values ranged from 0.57 for phenazepam to 1.18 to pyrazolam. Four designer benzodiazepines appearing since 2017 (fluclotizolam, difludiazepam, flualprazolam, and clobromazolam) had predicted binding affinities to the GABA_A receptor that were greater than previously predicted binding affinities for other designer benzodiazepines.

CONCLUSIONS

This work highlights the diverse nature of the designer benzodiazepines and adds to our understanding of their pharmacology. The greater predicted binding affinities are a potential indication of the increasing potency of designer benzodiazepines appearing on the illicit drugs market.

A new dried blood spot LC-MS/MS method for therapeutic drug monitoring of palbociclib, ribociclib, and letrozole in patients with cancer

Therapeutic drug monitoring (TDM) is strongly suggested to define the proper drug dosage to overcome inter- and intra-patient variability in drug exposure, which is typically observed with oral anticancer agents, such as palbociclib (PALBO), ribociclib (RIBO) and letrozole (LETRO), all approved for the treatment of HR+, HER2- locally advanced or metastatic breast cancer (BC). Optimal TDM implementation requires a blood sampling organization that can be hampered by limited availability of health and laboratory personnel. Dried Blood Spot (DBS) sampling is proposed to overcome such limitations. The aim of this work was the development of a new LC-MS/MS method to analyze DBS samples containing PALBO, RIBO, and LETRO. Analytes extraction from DBS was performed by adding a methanolic solution containing the corresponding internal standards. LC-MS/MS analysis was performed using a LC Nexera (Shimadzu) system coupled with an API 4000 QTrap (SCIEX) mass spectrometer. The chromatographic separation was performed on a Luna Omega Polar C18 column (Phenomenex). The method was applied to 38 clinical samples collected by finger prick. The influence of hematocrit and spot size, sample homogeneity, stability, and correlation between finger prick and venous DBS measurement were assessed. The analytical validation was performed according to EMA and FDA guidelines. The analytical range of the method was 1 to 250 ng/mL for PALBO, 40 to 10000 ng/mL for RIBO, and 2 to 500 ng/mL for LETRO, where linearity was assessed, obtaining mean coefficients of determination (R²) of 0.9979 for PALBO, 0.9980 for RIBO, and 0.9987 for LETRO). The LC-MS/MS method runtime was 6.6 min. Incurred sample reanalysis demonstrated reproducibility, as the percentage difference between the two quantifications was lower than 20% for 100% of PALBO, 81.8% of RIBO, and 90.9% of LETRO paired samples. Intra- and inter-day precision (CV (%)) was lower than 11.4% and intra- and inter-day accuracy was between 90.0 and 106.5%. DBS sample stability at room temperature was confirmed for 2.5 months. A positive correlation was observed between DBS and plasma concentrations for the 3 drugs, Lin's concordance correlation coefficients obtained by DBS normalization applying a selected strategy were 0.958 for PALBO, 0.957 for RIBO, and 0.963 for LETRO. In conclusion, a fast, easy, and reproducible DBS LC-MS/MS method for the simultaneous quantification of palbociclib; ribociclib and letrozole was developed to be used in clinical practice.

Comparing Dried Blood Spots and Plasma Concentrations for Busulfan Therapeutic Drug Monitoring in Children

BACKGROUND

Busulfan (Bu) is one of the conditioning regimen components for pediatric hematopoietic stem cell transplantation. Bu therapeutic drug monitoring (TDM) is essential for a successful treatment outcome and toxicity evasion. Dried blood spot (DBS) sampling is a rapid and simple method for Bu TDM, compared with conventional plasma sampling. This study evaluated the feasibility of using the DBS method for Bu TDM. The hematocrit (Hct) and conditioning day were also examined for their impact on the DBS method's performance.

METHODS

Venous blood collected from 6 healthy volunteers was diluted, using their plasma into 4 samples of varying Hct values. Each sample was spiked with Bu calibrators (300, 600, and 1400 ng/mL), prepared using DBS and dried plasma spot (DPS) sampling and analyzed using a validated liquid-chromatography tandem-mass spectrometry method. Clinical blood samples (n = 153) from pediatric patients (n = 15) treated with Bu (mainly from doses 1, 2, 5, and 9) were used to prepare paired volumetric DBS and DPS samples. A Bland-Altman plot and Deming regression were used to define the agreement between the paired DBS and DPS measurements. Passing-Bablok regression analyses investigated the effects of Hct and conditioning day on the linearity between both methods.

RESULTS

In vitro analyses showed good agreement between DBS and DPS measurements, with a mean difference of -5.4% and a 95% confidence interval on the limits of agreement of -15.3% to 4.6%. Clinical samples showed good correlation (Pearson correlation coefficient = 0.96; slope = 1.00) between the DBS and DPS methods. The DBS method met the clinical acceptance limits for clinical samples, with a bias <±20%. Bland-Altman plots showed good agreement, with only 5.8% of paired measurements exceeding the limits of agreement (±1.96 SD), although within its 95% confidence interval. Hct observations ranged from 21.7% to 34.7% and did not affect Bu concentrations measured from DBS in either the in vitro or in vivo studies.

CONCLUSIONS

These results show that DBS is a useful method for Bu TDM, provided samples are analyzed on the collection day. DBS sampling offers advantages over traditional plasma sampling in infants and younger children because only small volumes of blood are required.

Elucidation of plasma protein binding, blood partitioning, permeability, CYP phenotyping and CYP inhibition studies of Withanone using validated UPLC method: An active constituent of neuroprotective herb Ashwagandha

ETHNOPHARMACOLOGICAL RELEVANCE

Withanone (WN), an active constituent of Withania somnifera commonly called Ashwagandha has remarkable pharmacological responses along with neurological activities. However, for a better understanding of the pharmacokinetic and pharmacodynamic behavior of WN, a comprehensive in-vitro ADME (absorption, distribution, metabolism, and excretion) studies are necessary.

AIM OF THE STUDY

A precise, accurate, and sensitive reverse-phase ultra-performance liquid chromatographic method of WN was developed and validated in rat plasma for the first time. The developed method was successfully applied to the in-vitro ADME investigation of WN.

MATERIAL AND METHODS

The passive permeability of WN was assayed using PAMPA plates and the plasma protein binding (PPB) was performed using the equilibrium dialysis method. Pooled liver microsomes of rat (RLM) and human (HLM) were used for the microsomal stability, CYP phenotyping, and inhibition studies. CYP phenotyping was evaluated using the specific inhibitors. CYP inhibition study was performed using specific probe substrates along with WN or specific inhibitors.

RESULTS

WN was found to be stable in the simulated gastric and intestinal environment and has a high passive permeability at pH 4.0 and 7.0 in PAMPA assay. The PPB of WN at 5 and 20 μg/mL concentrations were found to be high i.e. 82.01 ± 1.44 and 88.02 ± 1.15%, respectively. The in vitro half-life of WN in RLM and HLM was found to be 59.63 ± 2.50 and 68.42 ± 2.19 min, respectively. CYP phenotyping results showed that WN was extensively metabolized by CYP 3A4 and1A2 enzymes in RLM and HLM. However, the results of CYP Inhibition studies showed that none of the CYP isoenzymes were potentially inhibited by WN in RLM and HLM.

CONCLUSION

The in vitro results of pH-dependent stability, plasma stability, permeability, PPB, blood partitioning, microsomal stability, CYP phenotyping, and CYP inhibition studies demonstrated that WN could be a better phytochemical for neurological disorders.

Dried Blood Spot Technique Applied in Therapeutic Drug Monitoring of Anticancer Drugs: a Review on Conversion Methods to Correlate Plasma and Dried Blood Spot Concentrations

BACKGROUND

Anticancer drugs are notoriously characterized by a low therapeutic index, the introduction of therapeutic drug monitoring (TDM) in oncologic clinical practice could therefore be fundamental to improve treatment efficacy. In this context, an attractive technique to overcome the conventional venous sampling limits and simplify TDM application is represented by dried blood spot (DBS). Despite the significant progress made in bioanalysis exploiting DBS, there is still the need to tackle some challenges that limit the application of this technology: one of the main issues is the comparison of drug concentrations obtained from DBS with those obtained from reference matrix (e.g., plasma). In fact, the use of DBS assays to estimate plasma concentrations is highly dependent on the chemical-physical characteristics of the measured analyte, in particular on how these properties determine the drug partition in whole blood.

METHODS

In the present review, we introduce a critical investigation of the DBS-to-plasma concentration conversion methods proposed in the last ten years and applied to quantitative bioanalysis of anticancer drugs in DBS matrix. To prove the concordance between DBS and plasma concentration, the results of statistical tests applied and the presence or absence of trends or biases were also considered.

Exploring the Interplay between Drug Release and Targeting of Lipid-Like Polymer Nanoparticles Loaded with Doxorubicin

Targeted delivery of doxorubicin still poses a challenge with regards to the quantities reaching the target site as well as the specificity of the uptake. In the present approach, two colloidal nanocarrier systems, NanoCore-6.4 and NanoCore-7.4, loaded with doxorubicin and characterized by different drug release behaviors were evaluated in vitro and in vivo. The nanoparticles utilize a specific surface design to modulate the lipid corona by attracting blood-borne apolipoproteins involved in the endogenous transport of chylomicrons across the blood–brain barrier. When applying this strategy, the fine balance between drug release and carrier accumulation is responsible for targeted delivery. Drug release experiments in an aqueous medium resulted in a difference in drug release of approximately 20%, while a 10% difference was found in human serum. This difference affected the partitioning of doxorubicin in human blood and was reflected by the outcome of the pharmacokinetic study in rats. For the fast-releasing formulation NanoCore-6.4, the AUC_0→1h was significantly lower (2999.1 ng × h/mL) than the one of NanoCore-7.4 (3589.5 ng × h/mL). A compartmental analysis using the physiologically-based nanocarrier biopharmaceutics model indicated a significant difference in the release behavior and targeting capability. A fraction of approximately 7.310–7.615% of NanoCore-7.4 was available for drug targeting, while for NanoCore-6.4 only 5.740–6.057% of the injected doxorubicin was accumulated. Although the targeting capabilities indicate bioequivalent behavior, they provide evidence for the quality-by-design approach followed in formulation development.

Whole blood or plasma: what is the ideal matrix for pharmacokinetic-driven drug candidate selection?

In the present era of drug development, quantification of drug concentrations following pharmacokinetic studies has preferentially been performed using plasma as a matrix rather than whole blood. However, it is critical to realize the difference between measuring drug concentrations in blood versus plasma and the consequences thereof. Pharmacokinetics using plasma data may be misleading if concentrations differ between plasma and red blood cells (RBCs) because of differential binding in blood. In this review, factors modulating the partitioning of drugs into RBCs are discussed and the importance of determining RBC uptake of drugs for drug candidate selection is explored. In summary, the choice of matrix (plasma vs whole blood) is an important consideration to be factored in during drug discovery.

Low-volume LC-MS/MS method for the pharmacokinetic investigation of carvedilol, enalapril and their metabolites in whole blood and plasma: Application to a paediatric clinical trial

Evidence-based pharmacotherapy with carvedilol and enalapril in children suffering from heart failure is insufficient owing to limited pharmacokinetic data. Although a few data sets regarding enalapril, its metabolite enalaprilat and carvedilol in children have been published, pharmacokinetic data on carvedilol metabolites are missing. However, for both drug substances, their active metabolites contribute substantially to drug efficacy. As data can hardly be derived from adults owing to the unknown impacts of enzymatic maturation and ontogeny during childhood, customised assays are important to facilitate paediatric evidence-based pharmacotherapy. Considering ethical paediatric constraints, a low-volume liquid chromatography coupled to mass spectrometry (LC-MS/MS) assay was developed using whole blood or plasma for the quantification of enalapril, enalaprilat, carvedilol, O-desmethyl carvedilol, 4- and 5-hydroxyphenyl carvedilol as well as 3- and 8-hydroxy carvedilol. To facilitate broader applications in adults, the elderly and children, a wide calibration range-between 0.024/0.049 and 50.000 ng/ml-was achieved with good linearity (r ≥ 0.995 for all analytes). In compliance with international bioanalytical guidelines, accuracy, precision, sensitivity and internal standard normalised matrix effects were further successfully validated with the exception of those for 3-hydroxy carvedilol, which was therefore assessed semi-quantitatively. Distinct haematocrits did not impact matrix effects or recoveries when analysing whole blood. Blood-to-plasma ratios were determined for all analytes to form the basis for pharmacokinetic modelling. Finally, incurred sample reanalysis of paediatric samples confirmed the reproducibility of the developed low-volume LC-MS/MS method during study sample analysis. The assay facilitates the reliable generation of important data and contributes towards a safe drug therapy in children.

Enantioselective in vitro ADME, absolute oral bioavailability, and pharmacokinetics of (-)-lumefantrine and (+)-lumefantrine in mice

Lumefantrine (LFN) is a chiral antimalarial drug. Enantioselective in vitro attributes and absolute oral pharmacokinetics for (-)-LFN and (+)-LFN have been characterized in mice. No stereoselectivity was seen with either of the enantiomers when compared with rac-LFN in the executed in vitro studies (solubility, metabolic stability, protein binding, permeability and blood partitioning). Post intravenous or oral administration of rac-LFN, the AUC_0-∞ and MRT of (+)-LFN was higher over (-)-LFN, which is reflected in higher clearance value for (-)-LFN. Following (-)-LFN intravenous administration to mice, the key PK parameters were comparable to (-)-LFN from rac-LFN; however, post intravenous administration of (+)-LFN alone to mice, the AUC_0-∞ was 1.3-fold higher than (+)-LFN from rac-LFN. Similarly, post oral administration of (-)-LFN to mice, both AUC_0-∞ and C_max were 1.3-fold higher than (-)-LFN from rac-LFN. On other hand, (+)-LFN showed 1.4-fold higher AUC_0-∞ and 1.7-fold higher C_max post oral administration over (+)-LFN from rac-LFN.

Description of Druglike Properties of Safranal and Its Chemistry behind Low Oral Exposure

Safranal, a plant secondary metabolite isolated from saffron, has been reported for several promising pharmacological properties toward the management of Alzheimer's disease. In the present study, we observe and report for the first time about several druglike attributes of safranal, such as adherence to Lipinski's rule of five; optimum lipophilicity; high permeability; low blood-to-plasma ratio; less to moderate propensity to interact with P-glycoprotein (P-gp) or breast cancer-resistant protein (BCRP) transporters; and high plasma protein binding as common to most of the marketed drugs using in vitro and ex vivo models. In spite of the above attributes, in vivo oral absorption was found to be very poor, which is linked to the structural integrity of safranal in simulated gastric fluid, simulated intestinal fluid, plasma, and liver microsomes. Moreover, the presence of unsaturated aldehyde moiety in safranal remains in equilibrium with its hydroxylated acetal form. Further research work is required to find out the stable oral absorbable form of safranal by derivatization of its aldehyde group without losing its potency.

Green chemistry appended synthesis, metabolic stability and pharmacokinetic assessment of medicinally important chromene dihydropyrimidinones

A green chemistry approach has been developed for the synthesis of chromene dihydropyrimidinone (CDHPM) using recyclable Fe/Al pillared clay catalyst. Pharmacokinetic parameters like aqueous solubility, lipophilicity, P-glycoprotein (P-gp) ATPase activity, permeability, plasma protein binding, red blood cell (RBC) partitioning, metabolic stability in liver microsomes and in silico computations have been studied for the most potent anticancer chromene dihydropyrimidinone hybrid 1. This compound exhibited low solubility, optimum lipophilicity, no P-gp inhibitory activity, intermediate permeability, high plasma protein binding, low RBC partitioning, acceptable metabolic stability in rat liver microsomes (RLM) as well as human liver microsomes (HLM) with transitional hepatic extraction ratio.

Pharmacokinetic evaluation of medicinally important synthetic N,N' diindolylmethane glucoside: Improved synthesis and metabolic stability

An improved route for the synthesis of N,N'-diindolyl methane (DIM) glycosides has been developed by using Fe/Al pillared clay catalyst. In-silico pharmacokinetics followed by in-vitro studies like aqueous solubility, lipophilicity, P-glycoprotein (P-gp) dependent ATPase activity, permeability, plasma protein binding, RBC partitioning, metabolic stability in different liver microsomes and its in-vitro-in-vivo extrapolation were conducted for the most potent derivative namely NGD16. The compound was found to have low solubility, optimum lipophilicity, no P-gp inhibitory activity, intermediate permeability, high plasma protein binding, low RBC partitioning, acceptable metabolic stability in rat liver microsomes (RLM) as well as human liver microsomes (HLM) with intermediate hepatic extraction ratio.

Preclinical assessment of the ADME, efficacy and drug-drug interaction potential of a novel NAMPT inhibitor

GNE-617 (N-(4-((3,5-difluorophenyl)sulfonyl)benzyl)imidazo[1,2-a]pyridine-6-carboxamide) is a potent, selective nicotinamide phosphoribosyltransferase (NAMPT) inhibitor being explored as a potential treatment for human cancers. Plasma clearance was low in monkeys and dogs (9.14 mL min^-1kg^-1 and 4.62 mL min^-1kg^-1, respectively) and moderate in mice and rats (36.4 mL min^-1kg^-1 and 19.3 mL min^-1kg^-1, respectively). Oral bioavailability in mice, rats, monkeys and dogs was 29.7, 33.9, 29.4 and 65.2%, respectively. Allometric scaling predicted a low clearance of 3.3 mL min^-1kg^-1 and a volume of distribution of 1.3 L kg^-1 in human. Efficacy (57% tumor growth inhibition) in Colo-205 CRC tumor xenograft mice was observed at an oral dose of 15 mg/kg BID (AUC = 10.4 µM h). Plasma protein binding was moderately high. GNE-617 was stable to moderately stable in vitro. Main human metabolites identified in human hepatocytes were formed primarily by CYP3A4/5. Transporter studies suggested that GNE-617 is likely a substrate for MDR1 but not for BCRP. Simcyp^® simulations suggested a low (CYP2C9 and CYP2C8) or moderate (CYP3A4/5) potential for drug-drug interactions. The potential for autoinhibition was low. Overall, GNE-617 exhibited acceptable preclinical properties and projected human PK and dose estimates.

Effects of fructose-containing sweeteners on fructose intestinal, hepatic, and oral bioavailability in dual-catheterized rats

Objective

Fructose is commonplace in Western diets and is consumed primarily through added sugars as sucrose or high fructose corn syrup. High consumption of fructose has been linked to the development of metabolic disorders, such as cardiovascular diseases. The majority of the harmful effects of fructose can be traced to its uncontrolled and rapid metabolism, primarily within the liver. It has been speculated that the formulation of fructose-containing sweeteners can have varying impacts on its adverse effects. Unfortunately, there is limited data supporting this hypothesis. The objective of this study was to examine the impact of different fructose-containing sweeteners on the intestinal, hepatic, and oral bioavailability of fructose.

Methods

Portal and femoral vein catheters were surgically implanted in male Wistar rats. Animals were gavaged with a 1 g/kg carbohydrate solution consisting of fructose, 45% glucose/55% fructose, sucrose, glucose, or water. Blood samples were then collected from the portal and systemic circulation. Fructose levels were measured and pharmacokinetic parameters were calculated.

Results

Compared to animals that were gavaged with 45% glucose/55% fructose or sucrose, fructose-gavaged animals had a 40% greater fructose area under the curve and a 15% greater change in maximum fructose concentration in the portal circulation. In the systemic circulation of fructose-gavaged animals, the fructose area under the curve was 17% and 24% higher and the change in the maximum fructose concentration was 15% and 30% higher than the animals that received 45% glucose/55% fructose or sucrose, respectively. After the oral administration of fructose, 45% glucose/55% fructose, and sucrose, the bioavailability of fructose was as follows: intestinal availability was 0.62, 0.53 and 0.57; hepatic availability was 0.33, 0.45 and 0.45; and oral bioavailability was 0.19, 0.23 and 0.24, respectively.

Conclusions

Our studies show that the co-ingestion of glucose did not enhance fructose absorption, rather, it decreased fructose metabolism in the liver. The intestinal, hepatic, and oral bioavailability of fructose was similar between 45% glucose/55% fructose and sucrose.

Efflux transporter breast cancer resistance protein dominantly expresses on the membrane of red blood cells, hinders partitioning of its substrates into the cells, and alters drug-drug interaction profiles

1. Red blood cell (RBC) partitioning is important in determining pharmacokinetic and pharmacodynamic properties of a compound; however, active transport across RBC membranes is not well understood, particularly without transporter-related cell membrane proteomics data. 2. In this study, we quantified breast cancer resistance protein (BCRP/Bcrp) and MDR1/P-glycoprotein (P-gp) protein expression in RBCs from humans, monkeys, dogs, rats and mice using nanoLC/MS/MS, and evaluated their effect on RBC partitioning and plasma exposure of their substrates. BCRP-specific substrate Cpd-1 and MDR1-specific substrate Cpd-2 were characterized using Caco-2 Transwell® system and then administered to Bcrp or P-gp knockout mice. 3. The quantification revealed BCRP/Bcrp but not MDR1/P-gp to be highly expressed on RBC membranes. The knockout mouse study indicated BCRP/Bcrp pumps the substrate out of RBCs, lowering its partitioning and thus preventing binding to intracellular targets. This result was supported by a Cpd-1 and Bcrp inhibitor ML753286 drug-drug interaction (DDI) study in mice. Because of enhanced partitioning of Cpd-1 into RBCs after BCRP/Bcrp inhibition, Cpd-1 plasma concentration changed much less extent with genetic or chemical knockout of Bcrp albeit marked blood concentration increase, suggesting less DDI effect. 4. This finding is fundamentally meaningful to RBC partitioning, pharmacokinetics and DDI studies of BCRP-specific substrates.

In vitro and in vivo pharmacokinetic characterization of mavacamten, a first-in-class small molecule allosteric modulator of beta cardiac myosin

Mavacamten is a small molecule modulator of cardiac myosin designed as an orally administered drug for the treatment of patients with hypertrophic cardiomyopathy. The current study objectives were to assess the preclinical pharmacokinetics of mavacamten for the prediction of human dosing and to establish the potential need for clinical pharmacokinetic studies characterizing drug-drug interaction potential. Mavacamten does not inhibit CYP enzymes, but at high concentrations relative to anticipated therapeutic concentrations induces CYP2B6 and CYP3A4 enzymes in vitro. Mavacamten showed high permeability and low efflux transport across Caco-2 cell membranes. In human hepatocytes, mavacamten was not a substrate for drug transporters OATP, OCT and NTCP. Mavacamten was determined to have minimal drug-drug interaction risk. In vitro mavacamten metabolite profiles included phase I- and phase II-mediated metabolism cross-species. Major pathways included aromatic hydroxylation (M1), aliphatic hydroxylation (M2); N-dealkylation (M6), and glucuronidation of the M1-metabolite (M4). Reaction phenotyping revealed CYPs 2C19 and 3A4/3A5 predominating. Mavacamten demonstrated low clearance, high volume of distribution, long terminal elimination half-life and excellent oral bioavailability cross-species. Simple four-species allometric scaling led to predicted plasma clearance, volume of distribution and half-life of 0.51 mL/min/kg, 9.5 L/kg and 9 days, respectively, in human.

Characterization of the Preclinical Pharmacology of the New 2-Aminomethylphenol, JPC-3210, for Malaria Treatment and Prevention

The new 2-aminomethylphenol, JPC-3210, has potent in vitro antimalarial activity against multidrug-resistant Plasmodium falciparum lines, low cytotoxicity, and high in vivo efficacy against murine malaria. Here we report on the pharmacokinetics of JPC-3210 in mice and monkeys and the results of in vitro screening assays, including the inhibition of cytochrome P450 (CYP450) isozymes. In mice, JPC-3210 was rapidly absorbed and had an extensive tissue distribution, with a brain tissue-to-plasma concentration ratio of about 5.4. JPC-3210 had a lengthy plasma elimination half-life of about 4.5 days in mice and 11.8 days in monkeys. JPC-3210 exhibited linear single-oral-dose pharmacokinetics across the dose range of 5 to 40 mg/kg of body weight with high oral bioavailability (∼86%) in mice. Systemic blood exposure of JPC-3210 was 16.6% higher in P. berghei-infected mice than in healthy mice. In vitro studies with mice and human hepatocytes revealed little metabolism and the high metabolic stability of JPC-3210. The abundance of human metabolites from oxidation and glucuronidation was 2.0% and 2.5%, respectively. CYP450 studies in human liver microsomes showed JPC-3210 to be an inhibitor of CYP2D6 and, to a lesser extent, CYP3A4 isozymes, suggesting the possibility of a metabolic drug-drug interaction with drugs that are metabolized by these isozymes. In vitro studies showed that JPC-3210 is highly protein bound to human plasma (97%). These desirable pharmacological findings of a lengthy blood elimination half-life, high oral bioavailability, and low metabolism as well as high in vivo potency have led the Medicines for Malaria Venture to select JPC-3210 (MMV892646) for further advanced preclinical development.

Pharmacokinetics and Metabolism of Streptochlorin and Its Synthetic Derivative, 5-Hydroxy-2'-isobutyl Streptochlorin, in Mice

The purpose of this study was to investigate the pharmacokinetics and metabolism of streptochlorin and its derivative 5-hydroxy-2'-isobutyl streptochlorin (HIS) in mice. Plasma concentration of streptochlorin declined rapidly resulting in a high sustemic plasma clearance (CL_p) (5.8±1.7 L/h/kg), a large volume of distribution (V_ss) (1.4±0.9 L/kg) and a short half-life (t_1/2) (0.4±0.1 h) after a single intravenous administration (5 mg/kg). Oral bioavailability (F) was 10.3±3.4% after a single oral administration (10 mg/kg). HIS also showed a rapid plasma decline with a high CL_p (11.3±8.8 L/h/kg), a high V_ss (0.8±1.0 L/kg) and a short t_1/2 (0.070±0.004 h) following intravenous administration. It was not detected in plasma after oral administration. Metabolic stability studies using mouse liver microsomes and S9 fractions predicted a high hepatic clearance for both compounds, consistent with the in vivo data. Metabolite identification studies revealed three metabolic pathways for streptochlorin: monooxygenation, glucuronidation of the indole moiety and oxidative opening of the 4-chlorooxazole ring. HIS was metabolized via monooxygenation of the isobutyl chain and glucuronidation of the indole ring. These results may aid in structural optimization to mitigate the metabolic liability of streptochlorin.

Clinical application of microsampling versus conventional sampling techniques in the quantitative bioanalysis of antibiotics: a systematic review

Conventional sampling techniques for clinical pharmacokinetic studies often require the removal of large blood volumes from patients. This can result in a physiological or emotional burden, particularly for neonates or pediatric patients. Antibiotic pharmacokinetic studies are typically performed on healthy adults or general ward patients. These may not account for alterations to a patient’s pathophysiology and can lead to suboptimal treatment. Microsampling offers an important opportunity for clinical pharmacokinetic studies in vulnerable patient populations, where smaller sample volumes can be collected. This systematic review provides a description of currently available microsampling techniques and an overview of studies reporting the quantitation and validation of antibiotics using microsampling. A comparison of microsampling to conventional sampling in clinical studies is included.

Prediction of inter-individual variability on the pharmacokinetics of CYP2C8 substrates in human

Inter-individual variability in pharmacokinetics can lead to unexpected side effects and treatment failure, and is therefore an important factor in drug development. CYP2C8 is a major drug-metabolizing enzyme known to be involved in the metabolism of over 100 drugs. In this study, we predicted the inter-individual variability in AUC/Dose of CYP2C8 substrates in healthy volunteers using the Monte Carlo simulation. Inter-individual variability in the hepatic intrinsic clearance of CYP2C8 substrates (CL_int,h,2C8) was estimated from the inter-individual variability in pharmacokinetics of pioglitazone, which is a major CYP2C8 substrate. The coefficient of variation (CV) of CL_int,h,2C8 was estimated to be 40%. Using this value, the CVs of AUC/Dose of other major CYP2C8 substrates, rosiglitazone and amodiaquine, were predicted to validate the estimated CV of CL_int,h,2C8. As a result, the reported CVs of both substrates were within the 2.5-97.5 percentile range of the predicted CVs. Furthermore, the CVs of AUC/Dose of the CYP2C8 substrates loperamide and chloroquine, which are affected by renal clearance, were also successfully predicted. Combining this value with previously reported CVs of other CYPs, we were able to successfully predict the inter-individual variability in pharmacokinetics of various drugs in clinical.

Pharmacokinetics of dinalbuphine sebacate and nalbuphine in human after intramuscular injection of dinalbuphine sebacate in an extended-release formulation

Nalbuphine is a semi-synthetic opioid indicated for the relief of moderate to severe pain. Its short half-life requires frequent injections in clinical practice, resulting in a greater incidence of adverse events. A prodrug of nalbuphine has been developed, dinalbuphine sebacate (DNS), dissolved in a simple oil-based injectable formulation, which could deliver and maintain an effective blood level of nalbuphine. An open-label, prospective, two-period study was performed in healthy volunteers to verify the extended blood concentration profile of nalbuphine. Twelve healthy Taiwanese were randomized to receive an intramuscular injection of 20 mg nalbuphine HCl and 150 mg DNS sequentially with a washout period of 5 days. To prevent DNS hydrolysis during sample analysis, the effect of four esterase inhibitors was evaluated in the quantitation of DNS in human whole blood and thenoyltrifluoroacetone was chosen. The bioavailability of nalbuphine from intramuscularly injected DNS relative to that from nalbuphine HCl was 85.4%. The mean absorption time of nalbuphine from DNS was 145.2 h. It took approximately 6 days for the complete release of DNS into the blood stream where DNS was rapidly hydrolysed to nalbuphine; suggesting a single injection of 150 mg DNS in our extended-release formulation could provide long-lasting pain relief.

Pharmacokinetics and tissue distribution of crotonoside

1. Crotonoside is a bioactive ingredient from Croton Herba with a strong antitumour activity. This study aimed to develop a highly sensitive and selective high-performance liquid chromatography (HPLC) method to quantify crotonoside in biological samples for pharmacokinetics and distribution studies. 2. Protein precipitation by perchloric acid was used to separate crotonoside from the biological samples, and the recovery rates for crotonoside and the internal standard (luteoloside) were  >80%. All calibration curves examining the crotonoside levels in plasma and tissues were linear (all correlation coefficients > 0.99). 3. The response to crotonoside appeared to be dose disproportional to the maximum plasma concentration and the area under the time-concentration curve in plasma over the range of 12.5-50.0 mg/kg, and crotonoside was highly distributed in tissues after intravenous administration. The highest crotonoside level was detected in the liver (28.79 ± 14.96 μg/g), whereas crotonoside was undetected in the brain.

Neuroprotective Effects of the Herbal Formula B401 in Both Cell and Mouse Models of Alzheimer's Disease

In this study, we have reported the herbal formula B401 that has neuroprotective effects via multifunction, multitarget characteristics. It is possible that the herbal formula B401 may also provide new insights for AD. Here, we studied protective effects in the Tet-On Aβ₄₂-GFP SH-SY5Y cell model and the APP/PS1/Tau triple transgenic mouse model by the herbal formula B401. In in vitro experiments, we showed that the herbal formula B401 treatment effectively reduces glutamate-induced excitotoxicity and acetylcholinesterase activity in Tet-On Aβ₄₂-GFP SH-SY5Y cells. In in vivo experiments, we found that oral B401 treatment effectively ameliorates neurocognitive dysfunctions of 3× Tg-AD mice via motor and cognitive behavior tests. By using magnetic resonance imaging, moorFLPI instruments, and chemiluminescence methods, we reported that oral B401 treatment effectively alleviates brain atrophy, improves subcutaneous blood flow, and reduces blood ROS in 3× Tg-AD mice. As observed from results of immunohistochemistry staining and western blotting, we found that oral B401 treatment significantly enhances expressions of neuroprotective proteins, while reducing expressions of AD derived proteins such as amyloid beta, phosphorylated Tau, neurofibrillary tangles, and 3-nitrotyrosine in the brain of 3× Tg-AD mice. Thus, the herbal formula B401 may have the potential to be developed into optimum TCM for AD patients.

A Pharmacokinetic Modeling Approach to Predict the Contribution of Active Metabolites to Human Efficacious Dose

A preclinical drug candidate, MRK-1 (Merck candidate drug parent compound), was found to elicit tumor regression in a mouse xenograft model. Analysis of samples from these studies revealed significant levels of two circulating metabolites, whose identities were confirmed by comparison with authentic standards using liquid chromatography-tandem mass spectrometry. These metabolites were found to have an in vitro potency similar to that of MRK-1 against the pharmacological target and were therefore thought to contribute to the observed efficacy. To predict this contribution in humans, a pharmacokinetic (PK) modeling approach was developed. At the mouse efficacious dose, the areas under the plasma concentration time curves (AUCs) of the active metabolites were normalized by their in vitro potency compared with MRK-1. These normalized metabolite AUCs were added to that of MRK-1 to yield a composite efficacious unbound AUC, expressed as "parent drug equivalents," which was used as the target AUC for predictions of the human efficacious dose. In vitro and preclinical PK studies afforded predictions of the PK of MRK-1 and the two active metabolites in human as well as the relative pathway flux to each metabolite. These were used to construct a PK model (Berkeley Madonna, version 8.3.18; Berkeley Madonna Inc., University of California, Berkeley, CA) and to predict the human dose required to achieve the target parent equivalent exposure. These predictions were used to inform on the feasibility of the human dose in terms of size, frequency, formulation, and likely safety margins, as well as to aid in the design of preclinical safety studies.

Quantitative analysis of methyl and propyl parabens in neonatal DBS using LC–MS/MS

Aim: Excipients are used to overcome the chemical, physical and microbiological challenges posed by developing formulated medicines. Both methyl and propyl paraben are commonly used in pediatric liquid formulations. There is no data on systemic exposure to parabens in neonates. The European Study of Neonatal Exposure to Excipients project has investigated this. Results & methodology: DBS sampling was used to collect opportunistic blood samples. Parabens were extracted from the DBS and analyzed using a validated LC–MS/MS assay. Discussion & conclusion: The above assay was applied to analyze neonatal DBS samples. The blood concentrations of parabens in neonates confirm systemic exposure to parabens following administration of routine medicines.

Human-on-a-chip design strategies and principles for physiologically based pharmacokinetics/pharmacodynamics modeling

Advances in maintaining multiple human tissues on microfluidic platforms has led to a growing interest in the development of microphysiological systems for drug development studies. Determination of the proper design principles and scaling rules for body-on-a-chip systems is critical for their strategic incorporation into physiologically based pharmacokinetic (PBPK)/pharmacodynamic (PD) model-aided drug development. While the need for a functional design considering organ-organ interactions has been considered, robust design criteria and steps to build such systems have not yet been defined mathematically. In this paper, we first discuss strategies for incorporating body-on-a-chip technology into the current PBPK modeling-based drug discovery to provide a conceptual model. We propose two types of platforms that can be involved in the different stages of PBPK modeling and drug development; these are μOrgans-on-a-chip and μHuman-on-a-chip. Then we establish the design principles for both types of systems and develop parametric design equations that can be used to determine dimensions and operating conditions. In addition, we discuss the availability of the critical parameters required to satisfy the design criteria, consider possible limitations for estimating such parameter values and propose strategies to address such limitations. This paper is intended to be a useful guide to the researchers focused on the design of microphysiological platforms for PBPK/PD based drug discovery.

Oral treatment with the herbal formula B401 protects against aging-dependent neurodegeneration by attenuating oxidative stress and apoptosis in the brain of R6/2 mice

BACKGROUND

Neurodegeneration is characterized by progressive neurological deficits due to selective neuronal loss in the nervous system. Huntington's disease (HD) is an incurable neurodegenerative disorder. Neurodegeneration in HD patients shows aging-dependent pattern. Our previous study has suggested that a herbal formula B401 may have neuroprotective effects in the brains of R6/2 mice.

OBJECTIVE

To clarify possible mechanisms for neurodegeneration, which improves the understanding the aging process. This study focuses on clarifying neurodegenerative mechanisms and searching potential therapeutic targets in HD patients.

METHODS

The oxidative stress and apoptosis were compared in the brain tissue between R6/2 HD mice with and without oral B401 treatment. Expressions of proteins for oxidative stress and apoptosis in the brain tissue of R6/2 HD mice were examined by using immunostaining and Western blotting techniques.

RESULTS

R6/2 HD mice with oral B401 treatment significantly reduced reactive oxygen species levels in the blood, but markedly increased expressions of superoxide dismutase 2 in the brain tissue. Furthermore, R6/2 HD mice with oral B401 treatment significantly increased expressions of B-cell lymphoma 2 (Bcl-2), but significantly reduced expressions of Bcl-2-associated X protein (Bax), calpain, and caspase-3 in the brain tissue.

CONCLUSION

Our findings provide evidence that the herbal formula B401 can remedy for aging-dependent neurodegeneration of R6/2 mice via suppressing oxidative stress and apoptosis in the brain. We suggest that the herbal formula B401 can be developed as a potential health supplement for ameliorating aging-dependent neurodegeneration.

Capillary microsampling of whole blood for mouse PK studies: an easy route to serial blood sampling

Background: Capillary microsampling (CMS) of 8 µl of blood provides a methodology that can be utilized for serial sampling in drug discovery mouse PK studies. Results: Blood CMS sample results were compared to plasma sample results for three compounds (with expected Cb/Cp of 1 to 2) and found to be similar. In addition, for three compounds, blood CMS results were found to be equivalent to results generated with standard whole blood sampling. In a 5-day repeated dose PK study, four mice were dosed (IV) daily and sampled on both day one and day five using blood CMS procedure. Conclusion: Blood CMS using 8 µl glass capillary microsamples provides a straightforward and effective approach for mouse serial blood sampling.

Small molecule disruptors of the glucokinase-glucokinase regulatory protein interaction: 4. Exploration of a novel binding pocket

Structure-activity relationship investigations conducted at the 5-position of the N-pyridine ring of a series of N-arylsulfonyl-N'-2-pyridinyl-piperazines led to the identification of a novel bis-pyridinyl piperazine sulfonamide (51) that was a potent disruptor of the glucokinase-glucokinase regulatory protein (GK-GKRP) interaction. Analysis of the X-ray cocrystal of compound 51 bound to hGKRP revealed that the 3-pyridine ring moiety occupied a previously unexplored binding pocket within the protein. Key features of this new binding mode included forming favorable contacts with the top face of the Ala27-Val28-Pro29 ("shelf region") as well as an edge-to-face interaction with the Tyr24 side chain. Compound 51 was potent in both biochemical and cellular assays (IC50=0.005 μM and EC50=0.205 μM, respectively) and exhibited acceptable pharmacokinetic properties for in vivo evaluation. When administered to db/db mice (100 mg/kg, po), compound 51 demonstrated a robust pharmacodynamic effect and significantly reduced blood glucose levels up to 6 h postdose.