Performance Verification of CYP2C19 Enzyme Abundance Polymorphism Settings within the Simcyp Simulator v21.

Physiologically based pharmacokinetic (PBPK) modeling has a number of applications, including assessing drug−drug interactions (DDIs) in polymorphic populations, and should be iteratively refined as science progresses. The Simcyp Simulator is annually updated and version 21 included updates to hepatic and intestinal CYP2C19 enzyme abundance, including addition of intermediate and rapid metabolizer phenotypes and changes to the ultra-rapid metabolizer enzyme abundance, with implications for population clearance and DDI predictions. This work details verification of the updates with sensitive CYP2C19 substrates, omeprazole and lansoprazole, using available clinical data from literature. Multiple assessments were performed, including recovery of areas under the concentration-time curve (AUC) and Cmax from compiled datasets for each drug, recovery of victim DDI ratios with CYP2C19 and/or CYP3A4 inhibition and recovery of relative exposure between phenotypes. Simulated data were within respective acceptance criteria for >80% of omeprazole AUC values, >70% of lansoprazole AUC and Cmax, >60% of AUC and Cmax DDI ratios and >80% of exposure ratios between different phenotypes. Recovery of omeprazole Cmax was lower (>50−70% within 2-fold) and possibly attributed to the variety of formulations used in the clinical dataset. Overall, the results demonstrated that the updated data used to parameterize CYP2C19 phenotypes reasonably described the pharmacokinetics of omeprazole and lansoprazole in genotyped or phenotyped individuals.

Insight into stereoselective disposition of enantiomers of a potent antithrombotic agent, S002-333 following administration of the racemic compound to mice.

S002-333 [2-(4-methoxy-benzenesulfonyl)-2,3,4,9-tetrahydro-1H-b-carboxylic acid amide], a potent antithrombotic agent developed by CSIR-CDRI, is a racemic mixture of two enantiomers (S004-1032 (R)-isomer and S007-1558 (S)-isomer). Despite extensive research, little is known about the pharmacokinetics of S002-333 enantiomers. Given that mouse is an established model for anti-platelet/antithrombotic activity and interspecies differences exists in the direction of stereoselectivity in pharmacokinetic processes, we investigated the pharmacokinetic disposition of S002-333 enantiomers in mice. Whereas the pharmacokinetics of S002-333 was non-stereoselective after intravenous (i.v.) administration, substantial stereoselectivity was observed after oral administration of the racemate. The oral AUC0-∞ of (R)-isomer (1228.21±97.55h∗ng/mL) was higher than that of (S)-isomer (861.55±182.07h∗ng/mL) whereas it was comparable after i.v. administration. The absolute oral bioavailability of (R)-isomer was ~1.7 times higher than that of its antipode. On incubating the racemic mixture or individual isomers with mice liver microsomes, (S)-isomer depleted significantly faster than (R)-isomer. Thus, low absolute oral bioavailability of (S)-isomer in comparison to (R)-isomer could be associated to stereoselective hepatic metabolism of (S)-isomer. Furthermore, no metabolic interaction between the enantiomers was observed. Tissue distribution analysis revealed that the highest amount of the enantiomers was localized in small intestine and liver which could be due to first pass metabolism in these organs. Stereoselectivity in the distribution of S002-333 was observed in liver, kidney, spleen and brain; however no significant differences between the plasma protein binding of the enantiomers were observed. The information revealed in the present work might prove valuable in deciding the development of S002-333 as racemic mixture and/or single enantiomer.

Investigation of salt formation between memantine and pamoic acid: Its exploitation in nanocrystalline form as long acting injection.

In the present work, we prepared memantine-pamoic acid (MEM-PAM) salt by counter ion exchange in the aqueous phase to reduce the water solubility of MEM hydrochloride (native form) to make it suitable for long acting injection. The ratio of MEM to PAM in salt formation was optimized to maximize the loading efficiency and complexation efficiency. The 2:1 molar ratio of MEM to PAM salt form displayed nearly 95% complexation efficiency and 50% drug loading. The solubility was decreased by a ∼1250 folds. Thermo Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Powder X-ray Diffraction Analysis (PXRD) studies revealed the formation of new solid phase. Additionally, Nuclear Magnetic Resonance (NMR) spectroscopy confirmed the anhydrous nature of the salt form. Through Fourier transformation infrared spectroscopy (FT-IR) we identified the molecular interactions. Further, the microcrystals of the salt were transformed into nanocrystals (NCs) using high pressure homogenization. The particle size distribution and atomic force microscopy confirmed the monodispersed and spherical shape of the NCs. The in vitro dissolution studies were performed under sink condition in phosphate buffer saline pH 6.8. The results of MTT assay in murine fibroblast 3T3 cell line show that the NCs were less cytotoxic and more tolerable than plain MEM HCl. The in vivo performance of NCs administered as i.m. injection at three different doses in female Sprague-Dawley rats showed that the plasma levels lasted till the 24th day of the study. The pharmacokinetic parameters AUC0-∞ and Cmax increased linearly with increasing dose. Therefore, the results suggest that injectable NCs could represent a therapeutic alternative for the treatment of AD.

In vitro effects of standardized extract of Bacopa monniera and its five individual active constituents on human P-glycoprotein activity.

1. For centuries Bacopa monniera (BM) has been used as an herbal drug for the treatment of various mental ailments. A chemically standardized alcoholic extract of BM is clinically available over the counter herbal remedy for memory enhancement in children and adults. Consumption of herbal preparations has been reported to alter the function of membrane transporters, especially P-glycoprotein (P-gp), ATP-dependent drug efflux transporter responsible for the development of herb-drug interactions. 2. In the present study, we evaluated the in vitro effect of BM extract and its five individual active constituents (namely, bacopaside I, bacopaside II and bacopasaponin C, bacoside A and bacoside A3) on P-gp function using luminescent P-gp ATPase assay and Rh123 transport assay across human MDR1 gene transfected LLC-GA5-COL150 cell line. 3. It was observed that BM extract and its five individual constituents inhibited both basal activity as well as verapamil-stimulated ATPase activity, suggesting their affinity towards P-gp. Further, BM and its five active constituents inhibited the rhodamine 123 (Rh123) transport across LLC-GA5-COL150 cell monolayer with bacopaside II being the most potent inhibitor of P-gp, which decreased P-gp efflux ratio of Rh123 by fourfold in comparison to control. 4. Our finding may prove beneficial in predicting the potential herb-drug interactions of BM on concomitant medication with P-gp substrate drugs in clinical settings.

Erythrocytes-based synthetic delivery systems: transition from conventional to novel engineering strategies.

INTRODUCTION: Erythrocytes (red blood cells [RBCs]) and artificial or synthetic delivery systems such as liposomes, nanoparticles (NPs) are the most investigated carrier systems. Herein, progress made from conventional approach of using RBC as delivery systems to novel approach of using synthetic delivery systems based on RBC properties will be reviewed. AREAS COVERED: We aim to highlight both conventional and novel approaches of using RBCs as potential carrier system. Conventional approaches which include two main strategies are: i) directly loading therapeutic moieties in RBCs; and ii) coupling them with RBCs whereas novel approaches exploit structural, mechanical and biological properties of RBCs to design synthetic delivery systems through various engineering strategies. Initial attempts included coupling of antibodies to liposomes to specifically target RBCs. Knowledge obtained from several studies led to the development of RBC membrane derived liposomes (nanoerythrosomes), inspiring future application of RBC or its structural features in other attractive delivery systems (hydrogels, filomicelles, microcapsules, micro- and NPs) for even greater potential. EXPERT OPINION: In conclusion, this review dwells upon comparative analysis of various conventional and novel engineering strategies in developing RBC based drug delivery systems, diversifying their applications in arena of drug delivery. Regardless of the challenges in front of us, RBC based delivery systems offer an exciting approach of exploiting biological entities in a multitude of medical applications.