Protein Binding Values Research Articles

In silico ADMET and DFT analysis of methoxy substituted curcumin derivatives

The current study aimed to predict drug ability of methoxy group substituted curcumin derivatives (MC1 to MC4) using ADMETLab 3.0 and DFT approaches. Almost all derivatives exhibited satisfactory physicochemical properties and medicinal chemistry. Pharmacokinetic profile revealed that all derivatives showed higher Caco-2 cell predicted permeability and exhibited a P-glycoprotein (Pgp) inhibitor capability, while non-of them is a Pgp-substrate. MC1 and MC2 exhibited favorable human intestinal absorption (HIA) values. MC1 was in favor of better oral bioavailability. Values for plasma protein binding and volume of distribution were optimum for MC1 and MC2. All compounds were unable to cross blood brain barrier. Fraction unbound in the plasma was moderate for all compounds. All derivatives exhibited moderate clearance rate, while having ultra short half-lives. Toxicity profile was moderate for almost all compounds. Similarly, the DFT computations of the compounds of the curcumin derivatives were conducted at B3LYP/6-311G** level to predict and then assess the key electronic characteristics underlying the bioactivity. Accordingly, the MC4 molecule (ΔEgap = 3.883 eV) would prefer to interact with the external molecular system more than the other molecules due to having the biggest energy gap. The ΔNmax (2.328 eV) and Δεback-donat. (−0.422 eV) scores implied that MC1 would have more charge transfer capability and the lowest stability via back donation among the compounds. In short, the derivative (MC1 to MC4) exhibited strong extrinsic therapeutic properties and therefore stand eligible for further in vitro and in vivo studies.

Preclinical characterisation of gallium-68 labeled ferrichrome siderophore stereoisomers for PET imaging applications

BackgroundSiderophores are small iron-binding molecules produced by microorganisms to facilitate iron acquisition from the environment. Radiolabelled siderophores offer a promising solution for infection imaging, as they can specifically target the pathophysiological mechanisms of pathogens. Gallium-68 can replace the iron in siderophores, enabling molecular imaging with positron emission tomography (PET). Stereospecific interactions play a crucial role in the recognition of receptors, transporters, and iron utilisation. Furthermore, these interactions have an impact on the host environment, affecting pharmacokinetics and biodistribution. This study examines the influence of siderophore stereoisomerism on imaging properties, with a focus on ferrirubin (FR) and ferrirhodin (FRH), two cis–trans isomeric siderophores of the ferrichrome type.ResultsTested siderophores were labelled with gallium-68 with high radiochemical purity. The resulting complexes differed in their in vitro characteristics. [68Ga]Ga-FRH showed less hydrophilic properties and higher protein binding values than [68Ga]Ga-FR. The stability studies confirmed the high radiochemical stability of both [68Ga]Ga-siderophores in all examined media. Both siderophores were found to be taken up by S. aureus, K. pneumoniae and P. aeruginosa with similar efficacy. The biodistribution tested in normal mice showed rapid renal clearance with low blood pool retention and fast clearance from examined organs for [68Ga]Ga-FR, whereas [68Ga]Ga-FRH showed moderate retention in blood, resulting in slower pharmacokinetics. PET/CT imaging of mice injected with [68Ga]Ga-FR and [68Ga]Ga-FRH confirmed findings from ex vivo biodistribution studies. In a mouse model of S. aureus myositis, both radiolabeled siderophores showed radiotracer accumulation at the site of infection.ConclusionsThe 68Ga-complexes of stereoisomers ferrirubin and ferrirhodin revealed different pharmacokinetic profiles. In vitro uptake was not affected by isomerism. Both compounds had uptake with the same bacterial culture with similar efficacy. PET/CT imaging showed that the [68Ga]Ga-complexes accumulate at the site of S. aureus infection, highlighting the potential of [68Ga]Ga-FR as a promising tool for infection imaging. In contrast, retention of the radioactivity in the blood was observed for [68Ga]Ga-FRH. In conclusion, the stereoisomerism of potential radiotracers should be considered, as even minor structural differences can influence their pharmacokinetics and, consequently, the results of PET imaging.

Adequate cefazolin therapy for critically ill patients: can we predict active concentrations from given protein-binding data?

Abstract Objectives Therapeutic drug monitoring of β-lactam antibiotics has become an important tool for treatment of severe infections, especially for critically ill patients who often exhibit altered PK/PD. Therapeutic targets are based on MIC, which refers to the active concentration of the drug. Cefazolin, a β-lactam agent used for treating of MSSA bacteraemia, has a protein binding of approximately 80 %. Therefore, a reliable determination of the active, non-protein-bound concentration is required to ensure optimal therapeutic outcome. Methods From seven critically ill patients who received an initial dose of 2 g cefazolin, followed by a continuous 24 h infusion, a total of 24 serum samples were obtained. The non-protein-bound concentration was directly measured after ultrafiltration and compared to prediction based total concentrations and protein binding values from the literature. For the analysis, a rapid and reliable LC-MS3 based assay was established, offering maximum sensitivity and specificity. Results The measured non-protein-bound concentration varied over a wide range (7.6–118 mg/L), with 22 out of 24 samples exhibiting cefazolin levels above the therapeutic target values (8–16 mg/L). Additionally, the observed protein binding ranged from 29 to 78 % (median 66.8 %), which was significantly lower than that reported in the literature. When comparing the measurements to the predictive performance of total concentrations and protein binding values, poor results were obtained. Conclusions The results show a high variability in plasma protein binding of cefazolin in critically ill patients. Therefore, the “one-dose-fits-all” principle can no longer be considered up to date. For personalised cefazolin therapy based on therapeutic drug monitoring (TDM) it is recommended to determine the active, non-protein-bound drug concentration, as calculations from the total fraction yield poor results.

The shortcoming of using glibenclamide in exploratory clinical headache provocation studies

Objective Preclinical and clinical studies implicate the vascular ATP-sensitive potassium (KATP) channel in the signaling cascades underlying headache and migraine. However, attempts to demonstrate that the KATP channel inhibitor glibenclamide would attenuate triggered headache in healthy volunteers have proven unsuccessful. It is questionable, however, whether target engagement was achieved in these clinical studies. Methods Literature data for human glibenclamide pharmacokinetics, plasma protein binding and functional IC50 values were used to predict the KATP receptor occupancy (RO) levels obtained after glibenclamide dosing in the published exploratory clinical headache provocation studies. RO vs. time profiles of glibenclamide were simulated for the pancreatic KATP channel subtype Kir6.2/SUR1 and the vascular subtype Kir6.1/SUR2B. Results At the clinical dose of 10 mg of glibenclamide used in the headache provocation studies, predicted maximal occupancy levels of up to 90% and up to 26% were found for Kir6.2/SUR1 and Kir6.1/SUR2B, respectively. Conclusions The findings of the present study indicate that effective Kir6.1/SUR2B target engagement was not achieved in the clinical headache provocation studies using glibenclamide. Therefore, development of novel selective Kir6.1/SUR2B inhibitors, with good bioavailability and low plasma protein binding, is required to reveal the potential of KATP channel inhibition in the treatment of migraine.

Small volume rapid equilibrium dialysis (RED) measures effects of interstitial parameters on the protein-bound fraction of topical drugs

The importance of plasma protein binding in the early stages of drug development is well recognized. Free and bound drug fractions in plasma are routinely determined with well-established methods. However, for physiological fluids with a small accessible volume and low protein concentrations, such as dermal interstitial fluid (dISF) validated methods are currently missing. Due to the low protein concentration and highly dynamic processes in the dermis, protein binding data obtained from plasma samples may underestimate in-vivo efficacy. This study aimed to validate a small volume rapid equilibrium dialysis (RED) for low protein samples, as a tool to examine drug-protein binding directly in the biological fluid at the site of action. The sample volume required for RED was successfully downscaled to 50 µl and plasma protein binding values of the four model drugs were consistent with previous studies with an average recovery of 88 ± 8% which makes all tested drugs suitable for small volume RED. Inter- and intra-batch variability showed sufficient reproducibility across RED plates. Small volume RED was successfully applied to assess the effects of interstitial parameters, including the evaluation of the major binding protein and the effects of binding protein concentration, drug concentration, and pH on the protein-bound drug fraction using 2% HSA and/or diluted human plasma as a surrogate for dISF.

625. SPR206 Pharmacokinetics (PK) in Plasma, Epithelial Lining Fluid (ELF), and Alveolar Macrophages (AM) in Healthy Adult Subjects

Abstract Background SPR206 is a novel intravenously (IV)-administered next-generation polymyxin being developed for the treatment of multi-drug resistant (MDR) Gram-negative (GN) infections. A Phase 1 bronchoalveolar lavage (BAL) study was conducted to evaluate SPR206 safety and PK in plasma and pulmonary matrices (ELF and AM) in healthy volunteers. Methods Subjects received 100 mg SPR206 administered intravenously over 1 h q8h for 3 consecutive doses. Blood samples were collected pre-dose (second and third dose) and at 2, 3, 4, 6, and 8 h after the start of the last dose. Each subject underwent one standardized bronchoscopy with BAL at 2, 3, 4, 6 or 8 hours after the start of the third IV infusion. Concentrations of SPR206 in plasma, BAL, and cell pellet were measured with a validated LC-MS/MS assay. Plasma, ELF, and AM PK parameters were determined by noncompartmental analysis. SPR206 AUC0–8 in ELF and AM were calculated using the mean concentration values at the BAL sampling times. SPR206 AUC0–8 ratios of ELF and AM to unbound plasma were determined using plasma protein binding value of 8.6%. Results Thirty-four subjects were enrolled and completed the study and 30 of 34 completed bronchoscopy. The mean SPR206 Cmax concentrations in plasma, ELF, and AM were 4395.0, 735.5, and 860.6 ng/mL, respectively. Mean AUC0-8 h values in plasma, ELF, and AM concentrations were 20120.7, 4859.8, and 6026.4 ng*h/mL, respectively--leading to a free ELF to plasma concentration ratio of 0.264 and free AM to plasma ratio of 0.328. Importantly, mean concentrations of SPR206 in the ELF achieved lung exposures above its minimum inhibitory concentration for the targeted gram-negative pathogens for the entire 8-hour dosing interval. Figure 1 displays the mean (±SD) SPR206 total and unbound plasma, ELF, and AM concentrations at the BAL sampling times. Overall, SPR206 was well tolerated; 22 subjects (64.7%) experienced at least 1 TEAE, mostly mild with a few moderate. The most frequently reported TEAEs were oral paresthesia [10 subjects (29.4%)] and nausea [2 subjects (5.9%)], which were reversible. Conclusion This study demonstrates pulmonary penetration of SPR206 and supports further development of SPR206 for the treatment of patients with pneumonia caused by MDR GN infections. Figure 1.Mean (±SD) plasma (total and unbound), epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of SPR206 in healthy adult subjects. This study was conducted in collaboration with, and with financial support from, the United States Department of Defense (Award No. W81XWH1910295). Disclosures Keith A. Rodvold, PharmD, Spero Therapeutics: Advisor/Consultant|Spero Therapeutics: Honoraria Justin Bader, n/a, Spero Therapeutics: Employee Vipul K. Gupta, Ph.D., Spero Therapeutics: Employee Troy Lister, Ph.D., Spero Therapeutics: Employee Praveen Srivastava, Ph.D., Spero Therapeutics: Employee Jon Bruss, M.D., Spero Therapeutics: Employee.

Optimizing a High-Throughput Solid-Phase Microextraction System to Determine the Plasma Protein Binding of Drugs in Human Plasma.

Plasma protein binding refers to the binding of a drug to plasma proteins after entering the body. The measurement of plasma protein binding is essential during drug development and in clinical practice, as it provides a more detailed understanding of the available free concentration of a drug in the blood, which is in turn critical for pharmacokinetics and pharmacodynamics studies. In addition, the accurate determination of the free concentration of a drug in the blood is also highly important for therapeutic drug monitoring and in personalized medicine. The present study uses C18-coated solid-phase microextraction 96-pin devices to determine the free concentrations of a set of drugs in plasma, as well as the plasma protein binding of drugs with a wide range of physicochemical properties. It should be noted that the extracted amounts used to calculate the binding constants and plasma protein bindings should be measured at respective equilibrium for plasma and phosphate buffer. Therefore, special attention is placed on properly determining the equilibration times required to correctly estimate the free concentrations of drugs in the investigated systems. The plasma protein binding values obtained with the 96-pin devices are consistent with those reported in the literature. The 96-pin device used in this research can be easily coupled with a Concept96 or other automated robotic systems to create an automated plasma protein binding determination protocol that is both more time and labor efficient compared to conventional equilibrium dialysis and ultrafiltration methods.

In silico Plasma Protein Binding Studies of Selected Group of Drugs Using TLC and HPLC Retention Data.

Plasma protein binding is an important determinant of the pharmacokinetic properties of chemical compounds in living organisms. The aim of the present study was to determine the index of protein binding affinity based on chromatographic experiments. The question is which chromatographic environment will best mimic the drug–protein binding conditions. Retention data from normal phase thin-layer liquid chromatography (NP TLC), reversed phase (RP) TLC and HPLC chromatography experiments with 129 active pharmaceutical ingredients (APIs) were collected. The stationary phase of the TLC plates was modified with protein and the HPLC column was filled with immobilized human serum albumin. In both chromatographic methods, the mobile phase was based on a buffer with a pH of 7.4 to mimic physiological conditions. Chemometric analyses were performed to compare multiple linear regression models (MLRs) with retention data, using protein binding values as the dependent variable. In the course of the analysis, APIs were divided into acidic, basic and neutral groups, and separate models were created for each group. The MLR models had a coefficient of determination between 0.73 and 0.91, with the highest values from NP TLC data.

The interaction of alpha-mangostin and its derivatives against main protease enzyme in COVID-19 using in silico methods.

More than 111 million people worldwide have been affected by the COVID-19 outbreak caused by SARS-CoV-2. The main therapeutic target of COVID-19 is main protease (Mpro). It plays a key role as an enzyme in the SARS-CoV-2 replication and transcription. In this case, the alpha-mangostin potentially has antiviral activity against Mpro by inhibiting this enzyme. Nevertheless, the alpha-mangostin has low solubility and a lack of information about alpha-mangostin activity against the SARS-CoV-2. The aim of this study is to describe the molecular interactions and identify the pharmacokinetics profile between alpha-mangostin and its derivatives. in silico study was conducted by pharmacokinetics and toxicity prediction, molecular docking simulation, and Lipinski's rule of five. FKS9 has a Gibbs free energy value of-10.5 kcal/mol with an inhibition constant of 36.45 μM and an interaction with amino acid His41 residue. Its human intestinal absorption and Caco-2 values were 95.13% and 47.71% while the plasma protein binding and blood-brain barrier values were 96.66% and 6.99%. FKS9 also has no mutagenic and carcinogenic potential. FKS9 as an alpha-mangostin derivative had the best interaction with the Mpro enzyme and its pharmacokinetic profiles was identified.

Structure-Activity Relationship of Antischistosomal Ozonide Carboxylic Acids.

Semisynthetic artemisinins and other bioactive peroxides are best known for their powerful antimalarial activities, and they also show substantial activity against schistosomes-another hemoglobin-degrading pathogen. Building on this discovery, we now describe the initial structure-activity relationship (SAR) of antischistosomal ozonide carboxylic acids OZ418 (2) and OZ165 (3). Irrespective of lipophilicity, these ozonide weak acids have relatively low aqueous solubilities and high protein binding values. Ozonides with para-substituted carboxymethoxy and N-benzylglycine substituents had high antischistosomal efficacies. It was possible to increase solubility, decrease protein binding, and maintain the high antischistosomal activity in mice infected with juvenile and adult Schistosoma mansoni by incorporating a weak base functional group in these compounds. In some cases, adding polar functional groups and heteroatoms to the spiroadamantane substructure increased the solubility and metabolic stability, but in all cases decreased the antischistosomal activity.

Developing a flow cytometry-based quantitative ido assay to measure immune potency of mesenchymal stromal cells product for phase i clinical trial

Background & Aim Establishment of a potency assay in the manufacturing of clinical grade mesenchymal stromal cells (MSCs) has been a challenge due to the issues of variability in starting cellular material, complex mechanisms of action, and lack of reference cells or materials. Indoleamine 2, 3-dioxygenase (IDO) is one of the most important factors for human MSC-mediated immunosuppression. IDO is expressed in IFN-γ-licensed MSC, but not in resting MSC in vitro. This intracellular enzyme catalyzes tryptophan degradation toward kynurenine and depletion of tryptophan suppresses T cells proliferation. Methods, Results & Conclusion In this study, we have developed a flow cytometry-based IDO assay for quantitatively measuring the IDO expression level per cell, the IPBV (Intracellular Protein Binding Value) of the cells represents the relative quantity of IDO expressed in the MSC. IPBV is defined as the number of anti-IDO fluorescent antibody molecules bound to intracellular IDO and standardized by fluorescence intensity of beads. Two kinds of in-house quality control reference cells were running in parallel with product to ensure that the assay is performing as expected and the level of IDO expression. Validation of the quantitative IDO assay, including accuracy, precision, specificity, linearity, range and robustness, were presented in this study. Moreover, we presented the application of the quantitative IDO assay for analysis of MSC product stability, comparability, and compatibility in the manufacturing of clinical grade MSC-based product- RegStem® ASC. In this study, we demonstrated the flow cytometry-based quantitative MSC IDO assay correlates with MSC's inhibition of autologous T cells proliferation, as well as the correlation with preliminary clinical effects in the phase I autologous MSC-based clinical trial for the treatment of Osteoarthritis. As the results, we believe that our novel flow cytometry-based quantitative IDO assay can be a potential potency assay candidate for advanced phase clinical trial of MSCs products.

MOLECULAR DOKING AND ADMET STUDIES OF AMINO-PYRIMIDINE DERIVATIES AS MYCOBACTERIUM TUBERCULOSIS SER/THR PROTEIN KINASES B INHIBITORS

We used the molecular docking method with Molegro software and we calculate ADME-T properties using Marvin Sketch and preADMET. The 29 amino-pyrimidines ligands were examined for docking studies with PknB (PDB Code: 2FUM).The Moldock score of the best three ligands L9, L12 and L21 are-161.475, -152.003 and-143.359 Kcal/Mol. These percentage shows that these candidature ligands have high binding energy percentage than the native MIX ligand. The ligand L21 has the human intestinal absorption (HIA), Caco-2 cell permeability, and plasma protein binding values of 85.48, 6.312 (nm/Sec.) and 93.097% respectively, which are comparable to MIX and the other ligands L9, L12. This computational study helped to prove that the ligand L21 have the ability to kill the Mycobacterium tuberculosis by inhibiting the expression of protein kinase B.

Pharmacokinetic-Pharmacodynamic Analyses to Provide Rezafungin Prophylaxis Dose Selection for Prevention of Invasive Fungal Infections for Bone Marrow Transplant Patients

Background: Rezafungin is a novel antifungal of the echinocandin class being developed as a single agent for prevention of invasive fungal infections (IFIs) caused by Candida, Aspergillus, and Pneumocystis spp. in patients at high risk of infection. Rezafungin exhibits an exceptionally long half-life (~133 h) which enables the administration of once-weekly dosing regimens. Treatment efficacy in a mouse Pneumocystis model is achieved at a human equivalent dose of <50 mg once-weekly [EHA. 2017. Abstr 9645]. A dose of 400 mg, followed by 200 mg once-weekly achieved >90% target attainment for treatment of Candida [AAC. 2018. 62:e02614-17]. Although lower doses of rezafungin might be useful for prevention of Pneumocystis and Candida infections, prevention of invasive aspergillosis in immunosuppressed populations is often considered more challenging. Pharmacokinetic-pharmacodynamic simulations were performed, at the dosing regimen for treatment of Candida, to evaluate the appropriateness of rezafungin for prophylaxis against A. fumigatus among bone marrow transplant (BMT) patients.Methods: A previously developed rezafungin population pharmacokinetic (PK) model [AAC. 2018. 62:e02603-17] was refined in NONMEM Version 7.2 using intravenous (IV) data from additional Phase 1 and Phase 2 studies. The ability of covariates such as body size, age, sex, albumin, markers of liver and renal function, and infection status to explain a portion of the interindividual variability on select PK parameters was explored using stepwise forward selection (α = 0.01) and backward elimination (α = 0.001). The final model was validated by comparing model-based predictions to observed data.Baseline demographic data were available from 100 patients who underwent a BMT at Stanford Medical Center. Using this dataset and the developed population PK model, a Monte Carlo simulation (n=2,000) was conducted to simulate expected rezafungin concentration-time profiles in BMT patients following administration of rezafungin 400 mg IV on Week 1 then 200 mg IV weekly x11. Using a human protein-binding value of 97.4%, free-drug concentration-time profiles were evaluated relative to the maximum observed A. fumigatus minimal effective concentration to inhibit 100% of isolates tested (MEC100) from surveillance data collected in 2016 [ASM Microbe 2018. Abstr Friday-485].Results: The final population PK model was a linear, 4-compartment model with zero order IV input. Albumin was an important predictor of the interindividual variability in rezafungin PK, as significant relationships were found between serum albumin concentration and clearance and volume of peripheral compartment 1. Additional relationships were found between PK parameters and sex, body surface area, presence of cirrhosis, and infection status. The model provided precise and unbiased fits to the observed data (r2=0.993 observed vs individual-predicted concentrations).The demographic dataset utilized for the simulations contained 100 BMT patients, of which 39 were female. Median (range) baseline body surface area and albumin were 1.84 m2 (1.27 - 2.61) and 3.35 g/dL (1.8 - 4.43), respectively. None of the patients had a baseline infection nor did any of the patients have cirrhosis. Following administration of rezafungin 400 mg IV on Week 1 then 200 mg IV weekly x11, free-drug plasma concentration-time profiles for Weeks 1, 2, and 12 relative to the A. fumigatus MEC100 (0.03 mg/L) are displayed in Figure 1. On Weeks 1, 2, and 12, 98.4%, 93.3%, and 91.9% of simulated patients, respectively, had rezafungin free-drug concentrations above the MEC100 value for the entire dosing interval (one week). This result was ≥99.9% for all 12 weeks when based on the MEC90 (0.015 mg/L).Conclusions: These data provide support for a once-weekly rezafungin dosing regimen for prevention of A. fumigatus infections among BMT patients. The effectiveness of current antifungal prophylactic regimens is frequently limited by safety, tolerability, drug interactions, adherence, pill burden and patient factors such as mucositis or background chemotherapeutic regimens. In addition to the excellent safety, tolerability, and lack of drug interactions exhibited by echinocandin agents, the favorable PK profile of rezafungin presents the opportunity to mitigate the typical challenges faced when administering IFI prophylaxis in BMT and other immunocompromised patients. [Display omitted] DisclosuresLakota:Cidara Therapeutics: Research Funding. Flanagan:Cidara Therapeutics: Employment, Equity Ownership. Sandison:Cidara Therapeutics: Employment, Equity Ownership. Brown:Cidara Therapeutics: Consultancy. Rubino:Cidara Therapeutics: Research Funding.

Drug development and bioanalytical method validation for a novel anticancer molecule, 4-(dimethylamino)-2-(p-tolylamino) thiazole-5-carbonitrile.

Hit, Lead & Candidate Discovery The thiazole ring system represents a significant building block that exists in many biologically active natural products and clinically successful anticancer drugs. Modifications of the thiazole core have been a proven and highly effective method in improving anticancer potency. We designed a novel thiazole-based molecule, 4-(dimethylamino)-2-(p-tolylamino) thiazole-5-carbonitrile, which showed potent in vitro anticancer effect against targeted Bcl-2 Jurkat cell-line quantified using 3-(4, 5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Physicochemical parameters (pKa, LogP, LogD) of the molecule have also been evaluated as a part of the drug development process. Moreover, a rapid Reverse phase-high performance liquid chromatography (RP-HPLC) bioanalytical method has been developed to quantitate the molecule in human plasma. The method has been validated following the United States Food and Drug Administration bioanalytical method validation guideline. The stability studies showed no significant instability of the analyte in respective stability conditions (6 hr autosampler, 8 hr bench top, 30 days long-term, and 3 freeze-thaw cycles). The molecule was found to be stable for 3 hr in human plasma. The molecule was shown to have high plasma protein binding affinity. It showed favorable pKa (11), Log P (3.01), Log D (2.96), and plasma protein binding (90%) values toward its further exploitation as a lead anticancer candidate molecule. The developed bioanalytical method can be used for quantifying the molecule in different pharmacokinetic, toxicokinetic, or other clinical trial samples involving human plasma during development process or in routine bioavailability and bioequivalence study after its regulatory approval.

Experimental versus theoretical log D7.4 , pKa and plasma protein binding values for benzodiazepines appearing as new psychoactive substances.

The misuse of benzodiazepines as new psychoactive substances is an increasing problem around the world. Basic physicochemical and pharmacokinetic data is required on these substances to interpret and predict their effects upon humans. Experimental log D7.4 , pKa and plasma protein binding values were determined for 11 benzodiazepines that have recently appeared as new psychoactive substances (3-hydroxyphenazepam, 4'-chlorodiazepam, desalkylflurazepam, deschloroetizolam, diclazepam, etizolam, flubromazepam, flubromazolam, meclonazepam, phenazepam, and pyrazolam) and compared with values generated by various software packages (ACD/I-lab, MarvinSketch, ADMET Predictor and PreADMET). ACD/I-LAB returned the most accurate values for log D7.4 and plasma protein binding while ADMET Predictor returned the most accurate values for pKa . Large variations in predictive errors were observed between compounds. Experimental values are currently preferable and desirable as they may aid with the future 'training' of predictive models for these new psychoactive substances.

Vinca Alkaloid Pharmacokinetics in the Context of a Physiologically‐Based Murine Model

Vinca alkaloids are a class of molecule clinically used as cytotoxic chemotherapeutics, and exert their activity through mitotic disruption by preventing the polymerization of microtubules. While successfully used to treat a variety of cancer types, patients receiving these treatments remain at risk of toxic side‐effects due to significant variability observed in drug disposition. The objective of this study was to characterize the primary factors driving vinca alkaloid pharmacokinetics (PK), and develop a model capable of predicting PK based on alterations in these drivers. Physiologic sources of variability are known to include a wide range of reported values for CYP3A‐mediated metabolism and plasma protein binding, as well as a strong correlation between tissue uptake and tissue tubulin content. Additionally, vinca alkaloids are known substrates of ABCB1 (MDR1, PGP), which mediates drug efflux from tissues. To investigate dependence on these factors we initially developed a physiologically‐based pharmacokinetic (PBPK) model for vinblastine (VBL) dosed IV at 2 mg/kg in MDR1a −/− (KO) and MDR1a +/+ (WT) mice. An increase in VBL exposure was observed in all KO tissues compared to WT, particularly in brain which accumulated roughly 10‐fold more VBL over 6 hours. This is of particular importance as neurotoxicity is the most commonly reported dose‐limiting toxicity for vinca alkaloids. Additionally, excretion through biliary and renal routes were 6‐fold and 10‐fold lower, respectively, for both VBL and the active metabolite, desacetylVBL. Using known physiological and biochemical parameters the PBPK model was developed and validated for key organs involved in distribution, metabolism, and excretion of VBL in the MDR1a WT and KO mice. Through adjustment of relevant biochemical parameters the model was validated for vincristine (VCR) PK in MDR1a WT mice receiving the same 2mg/kg IV bolus dose, and used to simulate what VCR PK might look like in an MDR1a KO scenario. The validated PBPK model for VBL and VCR allows for investigation of PK based on alterations in measurable, physiologically‐relevant driving factors in murine models. Due to the pharmacologic similarities between molecules within the vinca alkaloid class, biochemical parameters can easily be adjusted to predict PK of vindesine and vinorelbine as well. Value of this model lies in its ability predict exposure in pre‐clinical studies involving vinca alkaloids, and provide insight into how exposure would be altered in combination therapy or gene knockout settings.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Pharmacokinetics of the anti-androgenic drug flutamide in healthy stallions

Alternatives to surgical castration are necessary for controlling the sexual behaviour of stallions with breeding potential in training and competition. Flutamide is a potent selective non-steroidal androgen receptor competitive antagonist that has been used in human beings as an anti-androgenic drug. In this study, the pharmacokinetics and bioavailability of flutamide and its main active metabolite, 2-hydroflutamide, were determined in seven healthy mature stallions. Single doses of flutamide (1mg/kg intravenously, 1mg/kg orally in fasted horses, 5mg/kg orally in fasted horses and 5mg/kg orally in fed horses) were administered randomly at intervals of 2 weeks. All horses had full physical examinations and blood samples were collected for pharmacokinetics, complete blood counts and biochemistry before and after drug administration. Administration of flutamide did not result in any abnormalities on physical examination or in blood parameters. After intravenous administration of flutamide, the volume of distribution was 0.83L/kg and clearance was 1.20L/h/kg. Flutamide and its metabolite had high protein binding values (93–97%). After oral administration, flutamide was rapidly transformed to 2-hydroxyflutamide, with areas under the concentration–time curve ratios of metabolite:drug ∼7. Oral bioavailability was 6.63% after 1mg/kg flutamide in fasted horses, 6.50% after 5mg/kg flutamide in fasted horses and 6.95% after 5mg/kg in fed horses. Half lives of flutamide were close to 1h after intravenous administration and 2h after oral administration. Half lives of 2-hydroxyflutamide were 4.79–6.84h for all routes and doses. After oral administration, oral flutamide reached plasma concentrations that could be effective as an anti-androgenic agent in horses, but further studies are needed to determine whether flutamide has clinical value as an alternative to castration for controlling sexual behaviour in stallions.

Revisiting the SAR of the Antischistosomal Aryl Hydantoin (Ro 13-3978).

The aryl hydantoin 1 (Ro 13-3978) was identified in the early 1980s as a promising antischistosomal lead compound. However, this series of aryl hydantoins produced antiandrogenic side effects in the host, a not unexpected outcome given their close structural similarity to the antiandrogenic drug nilutamide. Building on the known SAR of this compound series, we now describe a number of analogs of 1 designed to maximize structural diversity guided by incorporation of substructures and functional groups known to diminish ligand–androgen receptor interactions. These analogs had calculated polar surface area (PSA), measured LogD7.4, aqueous kinetic solubility, and estimated plasma protein binding values in ranges predictive of good ADME profiles. The principal SAR insight was that the hydantoin core of 1 is required for high antischistosomal activity. We identified several compounds with high antischistosomal efficacy that were less antiandrogenic than 1. These data provide direction for the ongoing optimization of antischistosomal hydantoins.

Early and protective microglial activation in Alzheimer's disease: a prospective study using 18F-DPA-714 PET imaging.

While emerging evidence suggests that neuroinflammation plays a crucial role in Alzheimer's disease, the impact of the microglia response in Alzheimer's disease remains a matter of debate. We aimed to study microglial activation in early Alzheimer's disease and its impact on clinical progression using a second-generation 18-kDa translocator protein positron emission tomography radiotracer together with amyloid imaging using Pittsburgh compound B positron emission tomography. We enrolled 96 subjects, 64 patients with Alzheimer's disease and 32 controls, from the IMABio3 study, who had both (11)C-Pittsburgh compound B and (18)F-DPA-714 positron emission tomography imaging. Patients with Alzheimer's disease were classified as prodromal Alzheimer's disease (n = 38) and Alzheimer's disease dementia (n = 26). Translocator protein-binding was measured using a simple ratio method with cerebellar grey matter as reference tissue, taking into account regional atrophy. Images were analysed at the regional (volume of interest) and at the voxel level. Translocator protein genotyping allowed the classification of all subjects in high, mixed and low affinity binders. Thirty high+mixed affinity binders patients with Alzheimer's disease were dichotomized into slow decliners (n = 10) or fast decliners (n = 20) after 2 years of follow-up. All patients with Alzheimer's disease had an amyloid positive Pittsburgh compound B positron emission tomography. Among controls, eight had positive amyloid scans (n = 6 high+mixed affinity binders), defined as amyloidosis controls, and were analysed separately. By both volumes of interest and voxel-wise comparison, 18-kDa translocator protein-binding was higher in high affinity binders, mixed affinity binders and high+mixed affinity binders Alzheimer's disease groups compared to controls, especially at the prodromal stage, involving the temporo-parietal cortex. Translocator protein-binding was positively correlated with Mini-Mental State Examination scores and grey matter volume, as well as with Pittsburgh compound B binding. Amyloidosis controls displayed higher translocator protein-binding than controls, especially in the frontal cortex. We found higher translocator protein-binding in slow decliners than fast decliners, with no difference in Pittsburgh compound B binding. Microglial activation appears at the prodromal and possibly at the preclinical stage of Alzheimer's disease, and seems to play a protective role in the clinical progression of the disease at these early stages. The extent of microglial activation appears to differ between patients, and could explain the overlap in translocator protein binding values between patients with Alzheimer's disease and amyloidosis controls.

Preparation and biological evaluation of (99m)Tc-labelled phenazine dioxides as potential tracers for hypoxia imaging.

The aim of this study was to investigate the capability of phenazine dioxides, recognized bioreductive antitumour agents, as carriers for (99m)Tc in order to generate potential theranostic radiopharmaceuticals towards hypoxic solid tumours. Two different phenazine dioxides were used as ligands for the (99m)Tc-tricarbonyl core in order to prepare the potential radiopharmaceuticals. The main physicochemical and biological properties were evaluated. Biodistribution of the two radiotracers was studied at different time points after intravenous injection in tumour bearing animals. Both compounds were obtained in high yield and radiochemichal purity. They were stable in labelling milieu, in human plasma and in the presence of histidine. Biodistribution studies in mice were characterized by slow blood clearance and persistent liver uptake, results that correlate with the values of lipophilicities and protein binding. Both the complexes showed good tumour uptake, which remained constant during the studied period. Tumour/muscle ratios proved very favourable, comparable to those of FMISO in the same animal model. On the other hand, tumour/blood ratios were low due to high blood uptake. The use of phenazine dioxides as ligands for the preparation of potential (99m)Tc-radiopharmaceuticals towards solid tumours is possible since tumour uptake and retention are promising although high blood and liver uptake are drawbacks worth consideration.