Establishment of a suitable animal model to evaluate sustained release (SR) formulations is very important because it reduces the development time of SR formulations. Beagle dogs are often used to evaluate prototype formulations since they can be directly administered powder, such as drug substance. However, the physiological condition of dogs is very different to that of humans. Therefore, the benefits of utilizing beagle dogs for the evaluation of modified release formulations such as sustained release formulations and enteric-coated formulations are doubtful. To clarify the best animal and/or experimental technique for the evaluation of modified release formulations, we investigated dipyridamole pharmacokinetics from prototype sustained release granules by utilizing beagle dogs, propantheline bromide-treated (PBT) beagle dogs, and miniature pigs. In normal dogs, the intestinal absorption and sustained release effect of dipyridamole decreased in the 20 mg sustained release granule. However, in PBT dogs, a sustained release effect was observed in the 45 mg sustained release granule, and its bioavailability was also maintained. Accordingly, PBT dogs could be the best to evaluate sustained release formulations such as tablets and granules, and the use of miniature pigs might be better to evaluate granules with equal to or less than 1 mm diameter.

Amphotericin B (AmB) has been a cornerstone in the treatment of invasive fungal infections for over 6 decades. Compared with conventional amphotericin B deoxycholate (AmB-DOC), liposomal amphotericin B has comparable efficacy but less nephrotoxicity. The main purpose of this study was to investigate the reason why liposomal amphotericin B has similar therapeutic effects but lower toxicity and the differences of distribution in humans between liposomal amphotericin B and AmB-DOC. To compare the distribution of liposomal amphotericin B and AmB-DOC in humans, the physiologically based pharmacokinetic (PBPK) model was established by bottom-up stepwise method. A rat PBPK model was established firstly, then verified in mouse level in consideration of interspecies differences in physiological- and drug-specific parameters, and finally the PBPK model was extrapolated to humans. Based on preclinical and clinical pharmacokinetic (PK) studies, the AmB-DOC and liposomal amphotericin B PBPK model were established, respectively. The simulated results of human PBPK model showed that the liposomal formulation changed the pharmacokinetic characteristics of AmB. Compared with AmB-DOC, the plasma exposure of liposomal formulation was higher, but the renal exposure was significantly reduced.

Botulinum neurotoxins (BoNTs) are commonly used in therapeutic and cosmetic applications. One such neurotoxin, BoNT type A (BoNT/A), has been studied widely for its effects on muscle function and contraction. Despite the importance of BoNT/A products, determining the blood concentrations of these toxins can be challenging. To address this, researchers have focused on pharmacodynamic (PD) markers, including compound muscle action potential (CMAP) and digit abduction scoring (DAS). In this study, we aimed to develop a probabilistic kinetic-pharmacodynamic (K-PD) model to interpret CMAP and DAS data obtained from mice and rats during the development of BoNT/A products. The researchers also wanted to gain a better understanding of how the estimated parameters from the model relate to the bridging of animal models to human responses. We used female Institute of Cancer Research mice and Sprague-Dawley (SD) rats to measure CMAP and DAS levels over 32 weeks after administering BoNT/A. We developed a muscle-contraction inhibition model using a virtual pharmacokinetic (PK) compartment combined with an indirect response model and performed model diagnostics using goodness-of-fit analysis, visual predictive checks (VPC), and bootstrap analysis. The CMAP and DAS profiles were dose-dependent, with recovery times varying depending on the administered dose. The final K-PD model effectively characterized the data and provided insights into species-specific differences in the PK and PD parameters. Overall, this study demonstrated the utility of PK-PD modeling in understanding the effects of BoNT/A and provides a foundation for future research on other BoNT/A products.

Relationship between the areas under the curve (AUC) of mycophenolic acid (MPA) and the likelihood of rejection is well-established in solid organ transplantation recipients. In hematopoietic stem cell transplantation (HSCT), MPA AUC is also linked to graft versus host disease. This study aimed to develop a simplified method to estimate MPA AUC in Chinese patients undergoing allogeneic HSCT (allo-HSCT). Intensive sampling was conducted in 22 patients who were orally administered mycophenolate mofetil. Plasma concentrations of total MPA were measured, and a model predicting AUC using data from these 22 patients was constructed through regression analysis. The accuracy of the most suitable model was assessed in an additional 20 patients. None of the individual MPA concentrations showed a strong correlation with AUC (r < 0.7). Models utilizing 4 or more concentrations were found to effectively estimate MPA AUC (r > 0.87). The most operationally feasible model demonstrated good predictive performance with a mean absolute percentage error (APE%) < 20%. Single MPA concentrations showed poor correlation with MPA AUC. A model utilizing 4 oral concentrations (0, 0.5, 1, and 4 h postdose) over a 12-h period could effectively estimate MPA AUC with precise results and minimal bias.

The brain is a sensitive organ with numerous essential functions and complex mechanisms. It is secluded and safeguarded from the external environment as part of the central nervous system (CNS), serving as a sanctuary. By regulating their selective and specific absorption, efflux, and metabolism in the brain, the CNS controls brain homeostasis and the transit of endogenous and foreign substances. The mechanism which protects the brain from environmental chemicals, also prevent the entry of therapeutic chemicals to it. The delivery of molecules to the brain is hindered by several major barriers, such as the blood-brain barrier (BBB), blood-cerebrospinal fluid barrier (BCSFB), and blood-tumor barrier. BBB is formed by the combination of cerebral endothelial cells, astrocytes, neurons, pericytes and microglia. It is a tight junction of capillary endothelial cells, preventing the diffusion of solute into the brain. BCSFB is the second barrier, located at the choroid plexus, separating the blood from cerebrospinal fluid (CSF). It is comparatively more permeable than BBB. An uneven distribution of microvasculature across the tumor interstitial compromises drug delivery to neoplastic cells of a solid tumor, resulting in spatially inconsistent drug administration. Nasal drug delivery to the brain is a method of drug delivery that tries to deliver therapeutic substances directly from the nasal cavity to the central nervous system including the brain. In this review, besides the role of barriers we have discussed in detail about approaches adapted to deliver drugs to the brain along with mechanisms through nasal route. Further, different commercial formulations, clinical trials and patents have been thoroughly elaborated to date. The findings suggest that the nose-to-brain drug delivery method holds promise as an evolving approach, potentially contributing to the specific and targeted delivery of drugs into the brain.

This study aimed to control the oral absorption of cyclosporine A (CsA) with the use of a mucosal drug delivery system (mDDS). Mucopenetrating nanocarriers (MP/NCs) and mucoadhesive nanocarriers (MA/NCs) were prepared by flash nanoprecipitation employing polystyrene-block-poly(ethylene glycol) and polystyrene-block-poly(N,N-dimethyl aminoethyl methacrylate), respectively. Their particle distribution in the rat gastrointestinal tract were visualized by fluorescent imaging. Plasma concentrations were monitored after oral administration of CsA-loaded MP/NCs (MP/CsA) and MA/NCs (MA/CsA) to rats. MP/NCs and MA/NCs had a particle size below 200 nm and ζ-potentials of 4 and 40 mV, respectively. The results from in vitro experiments demonstrated mucopenetration of MP/NCs and mucoadhesion of MA/NCs. Confocal laser scanning microscopic images showed diffusion of MP/NCs in the gastrointestinal mucus towards epithelial cells and localization of MA/NCs on the surface of the gastrointestinal mucus layer. In a pH 6.8 solution, rapid and sustained release of CsA were observed for MP/CsA and MA/CsA, respectively. After oral dosing (10 mg-CsA/kg) to rats, amorphous CsA powder exhibited a time to maximum plasma concentration (T) of 3.4 h, maximum plasma concentration (C) of 0.12 μg/mL, and bioavailability of 0.7%. Compared with amorphous CsA powder, MP/CsA shortened T by 1.1 to 2.3 h and increased the bioavailability by 43-fold to 30.1%, while MA/CsA prolonged T by 3.4 to 6.8 h with C and bioavailability of 0.65 μg/mL and 11.7%, respectively. These pharmacokinetic behaviors would be explained by their diffusion and release properties modulated by polymeric surface modification. The mDDS approach is a promising strategy for the pharmacokinetic control of orally administered CsA.

The United States Food and Drug Administration guidelines for the bioequivalence (BE) testing of the generic drug products suggests that there should be an equal proportion of male and female population in the BE study. Despite this requirement, many generic drug companies do not maintain the suggested proportion of female population in their studies. Several socio-economic and cultural factors lead to lower participation of the females in the BE studies. More recently, the regulatory agencies across the globe are requesting the generic drug companies to demonstrate the performance of their drug products in the under-represented sex via additional studies. In this work, we describe the case of Dextromethorphan modified release tablets where the gender effect on the product performance was evaluated by physiologically based pharmacokinetic (PBPK) modeling approach. We have compared the drug product's performance by population simulations considering four different scenarios. The data from all-male population (from in house Pharmacokinetic [PK] BE studies) was considered as a reference and other scenarios were compared against the all-male population data. In the first scenario, we made a comparison between all-male (100% male) vs all-female (100% female) population. Second scenario was as per agency's requirements-equal proportion of male and female in the BE study. As an extreme scenario, 100% male vs 30:70 male:female was considered (higher females than males in the BE studies). Finally, as a more realistic scenario, 100% male versus 70:30 male:female was considered (lower females than males in the BE studies). Population PK followed by virtual BE was employed to demonstrate the similarity/differences in the drug product performance between the sexes. This approach can be potentially utilized to seek BE study waivers thus saving cost and accelerating the entry of the generic products to the market.

Bumetanide is used widely as a tool and off-label treatment to inhibit the Na-K-2Cl cotransporter NKCC1 in the brain and thereby to normalize intra-neuronal chloride levels in several brain disorders. However, following systemic administration, bumetanide only poorly penetrates into the brain parenchyma and does not reach levels sufficient to inhibit NKCC1. The low brain penetration is a consequence of both the high ionization rate and plasma protein binding, which restrict brain entry by passive diffusion, and of brain efflux transport. In previous studies, bumetanide was determined in the whole brain or a few brain regions, such as the hippocampus. However, the blood-brain barrier and its efflux transporters are heterogeneous across brain regions, so it cannot be excluded that bumetanide reaches sufficiently high brain levels for NKCC1 inhibition in some discrete brain areas. Here, bumetanide was determined in 14 brain regions following i.v. administration of 10 mg/kg in rats. Because bumetanide is much more rapidly eliminated by rats than humans, its metabolism was reduced by pretreatment with piperonyl butoxide. Significant, up to 5-fold differences in regional bumetanide levels were determined with the highest levels in the midbrain and olfactory bulb and the lowest levels in the striatum and amygdala. Brain:plasma ratios ranged between 0.004 (amygdala) and 0.022 (olfactory bulb). Regional brain levels were significantly correlated with local cerebral blood flow. However, regional bumetanide levels were far below the IC (2.4 μM) determined previously for rat NKCC1. Thus, these data further substantiate that the reported effects of bumetanide in rodent models of brain disorders are not related to NKCC1 inhibition in the brain.

Icaritin is a prenylflavonoid derivative of the genus Epimedium (Berberidaceae) and has a variety of pharmacological actions. Icaritin is approved by the National Medical Products Administration as an anticancer drug that exhibits efficacy and safety advantages in patients with hepatocellular carcinoma cells. This study aimed to evaluate the inhibitory effects of icaritin on UDP-glucuronosyltransferase (UGT) isoforms. 4-Methylumbelliferone (4-MU) was employed as a probe drug for all the tested UGT isoforms using in vitro human liver microsomes (HLM). The inhibition potentials of UGT1A1 and 1A9 in HLM were further tested by employing 17β-estradiol (E2) and propofol (PRO) as probe substrates, respectively. The results showed that icaritin inhibits UGT1A1, 1A3, 1A4, 1A7, 1A8, 1A10, 2B7, and 2B15. Furthermore, icaritin exhibited a mixed inhibition of UGT1A1, 1A3, and 1A9, and the inhibition kinetic parameters (K) were calculated to be 3.538, 2.117, and 0.306 (μM), respectively. The inhibition of human liver microsomal UGT1A1 and 1A9 both followed mixed mechanism, with K values of 2.694 and 1.431 (μM). This study provides supporting information for understanding the drug-drug interaction (DDI) potential of the flavonoid icaritin and other UGT-metabolized drugs in clinical settings. In addition, the findings provide safety evidence for DDI when liver cancer patients receive a combination therapy including icaritin.

Alzheimer's disease is a complex multifactorial neurodegenerative disorder wherein age is a major risk factor. The appropriateness of the Hartley guinea pig (GP), which displays high sequence homologies of its amyloid-β (Aβ and Aβ) peptides, Mdr1 and APP (amyloid precursor protein) and similarity in lipid handling to humans, was appraised among 9-40 weeks old guinea pigs. Protein expression levels of P-gp (Abcb1) and Cyp46a1 (24(S)-hydroxylase) for Aβ, and Aβ efflux and cholesterol metabolism, respectively, were decreased with age, whereas those for Lrp1 (low-density lipoprotein receptor related protein 1), Rage (receptor for advanced glycation endproducts) for Aβ efflux and influx, respectively, and Abca1 (the ATP binding cassette subfamily A member 1) for cholesterol efflux, were unchanged among the ages examined. There was a strong, negative correlation of the brain Aβ peptide concentrations and Abca1 protein expression levels with free cholesterol. The correlation of Aβ peptide concentrations with Cyp46a1 was, however, not significant, and concentrations of the 24(S)-hydroxycholesterol metabolite revealed a decreasing trend from 20 weeks old toward 40 weeks old guinea pigs. The composite data suggest a role for free cholesterol on brain Aβ accumulation. The decreases in P-gp and Lrp1 protein levels should further exacerbate the accumulation of Aβ peptides in guinea pig brain.

VX-548 is a sodium channel blocker, which acts as an analgesic. This study aims to investigate the gender differences in the pharmacokinetics and metabolism of VX-548 in rats. After intravenous administration, the area under the curve (AUC) of VX-548 was much higher in female rats (1505.8 ± 47.3 ng·h/mL) than in male rats (253.8 ± 6.3 ng·h/mL), and the clearance in female rats (12.5 ± 0.8 mL/min/kg) was much lower than in male rats (65.1 ± 1.7 mL/min/kg). After oral administration, the AUC in female rats was about 50-fold higher than that in male rats. The oral bioavailability in male rats was 11% while it was 96% in female rats. An in vitro metabolism study revealed that the metabolism of VX-548 in female rat liver microsomes was much slower than in male rats. Further metabolite identification suggested that the significant gender difference in pharmacokinetics was attributed to demethylation. The female rat liver microsomes showed a limited ability to convert VX-548 into desmethyl VX-548. Phenotyping experiments indicated that the formation of desmethyl VX-548 was mainly catalyzed by CYP3A2 and CYP2C11 using rat recombinant CYPs. Overall, we revealed that the pharmacokinetics and metabolism of VX-548 in male and female rats showed significant gender differences.

This research aims to identify regional differences in vildagliptin absorption across the intestinal membrane. Furthermore, it was to investigate the effect of verapamil or metformin on vildagliptin absorptive clearance. The study utilized an in situ rabbit intestinal perfusion technique to determine vildagliptin oral absorption from duodenum, jejunum, ileum, and ascending colon. This was conducted both with and without perfusion of metformin or verapamil. The findings revealed that the vildagliptin absorptive clearance per unit length varied by site and was in the order as follows: ileum < jejunum < duodenum < ascending colon, implying that P-gp is significant in the reduction of vildagliptin absorption. Also, the arrangement cannot reverse intestinal P-gp, but the observations suggest that P-gp is significant in reducing vildagliptin absorption. Verapamil co-perfusion significantly increased the vildagliptin absorptive clearance by 2.4 and 3.2 fold through the jejunum and ileum, respectively. Metformin co-administration showed a non-significant decrease in vildagliptin absorptive clearance through all tested segments. Vildagliptin absorption was site-dependent and may be related to the intestinal P-glycoprotein content. This may aid in understanding the important elements that influence vildagliptin absorption, besides drug-drug interactions that can occur in type 2 diabetic patients taking vildagliptin in conjunction with other drugs that can modify the P-glycoprotein level.

AST-001 is a chemically synthesized inactive nitrogen mustard prodrug that is selectively cleaved to a cytotoxic aziridine (AST-2660) via aldo-keto reductase family 1 member C3 (AKR1C3). The purpose of this study was to investigate the pharmacokinetics and tissue distribution of the prodrug, AST-001, and its active metabolite, AST-2660, in mice, rats, and monkeys. After single and once daily intravenous bolus doses of 1.5, 4.5, and 13.5 mg/kg AST-001 to Sprague-Dawley rats and once daily 1 h intravenous infusions of 0.5, 1.5, and 4.5 mg/kg AST-001 to cynomolgus monkeys, AST-001 exhibited dose-dependent pharmacokinetics and reached peak plasma levels at the end of the infusion. No significant accumulation and gender differences were observed after 7 days of repeated dosing. In rats, the half-life of AST-001 was dose independent and ranged from 4.89 to 5.75 h. In cynomolgus monkeys, the half-life of AST-001 was from 1.66 to 5.56 h and increased with dose. In tissue distribution studies conducted in Sprague-Dawley rats and in liver cancer PDX models in female athymic nude mice implanted with LI6643 or LI6280 HepG2-GFP tumor fragments, AST-001 was extensively distributed to selected tissues. Following a single intravenous dose, AST-001 was not excreted primarily as the prodrug, AST-001 or the metabolite AST-2660 in the urine, feces, and bile. A comprehensive analysis of the preclinical data and inter-species allometric scaling were used to estimate the pharmacokinetic parameters of AST-001 in humans and led to the recommendation of a starting dose of 5 mg/m in the first-in-human dose escalation study.

The aim of this study was firstly to investigate the effect of membrane permeability on the intestinal availability (F ) of 10 cytochrome P450 3A4 substrates with differing permeability (P ) and metabolic activity (CL ) using Madin-Darby canine kidney II (MDCKII) cells expressing human CYP3A4 (MDCKII/CYP3A4 cells), and secondly to confirm the essential factors by simulations. A membrane permeation assay using MDCKII/CYP3A4 cells showed a significant correlation between human intestinal extraction ratio (ER) (E (=1 - F )) and in vitro cellular ER (r = 0.834). This relationship afforded better predictability of E values than the relationship between E and CL values obtained from human intestinal microsomes (r = 0.598). An even stronger correlation was observed between 1 - F ·F and ER (r = 0.874). Simulation with a cellular kinetic model indicated that ER is sensitive to changes of PS and CL values, but not to the intracellular unbound fraction (f ) or P-gp-mediated efflux (PS ). It may be concluded that, based on the concentration-time profile of drugs in epithelial cells, transmembrane permeability influences F (or ER) and drug exposure time to metabolizing enzymes for P450 substrate.

SCO-267 is a potent G-protein-coupled receptor 40 agonist that is undergoing clinical development for the treatment of type 2 diabetes mellitus. The current work was undertaken to investigate the bioactivation potential of SCO-267 in vitro and in vivo. Three SCO-267-derived glutathione (GSH) conjugates (M1-M3) were found both in rat and human liver microsomal incubations supplemented with GSH and nicotinamide adenine dinucleotide phosphate. Two GSH conjugates (M1-M2) together with two N-acetyl-cysteine conjugates (M4-M5) were detected in the bile of rats receiving SCO-267 at 10 mg/kg. The identified conjugates suggested the generation of quinone-imine and ortho-quinone intermediates. CYP3A4 was demonstrated to primarily catalyze the bioactivation of SCO-267. In addition, SCO-267 concentration-, time-, and NADPH-dependently inactivated CYP3A in human liver microsomes using testosterone as a probe substrate, along with K and k values of 4.91 μM and 0.036 min , respectively. Ketoconazole (a competitive inhibitor of CYP3A) displayed no significant protective effect on SCO-267-induced CYP3A inactivation. However, inclusion of GSH showed significant protection. These findings revealed that SCO-267 undergoes a facile CYP3A4-catalyzed bioactivation with the generation of quinone-imine and ortho-quinone intermediates, which were assumed to be involved in SCO-267 induced CYP3A inactivation. These findings provide further insight into the bioactivation pathways involved in the generation of reactive, potentially toxic metabolites of SCO-267. Further studies are needed to evaluate the influence of SCO-267 metabolism on the safety of this drug in vivo.

Drug metabolism plays a crucial role in drug fate, including therapeutic inactivation or activation, as well as the formation of toxic compounds. This underscores the importance of understanding drug metabolism in drug discovery and development. Considering the substantial costs associated with traditional drug development methods, computational approaches have emerged as valuable tools for predicting the metabolic fate of drug candidates. With this in mind, the present study aimed to investigate the potential mechanisms underlying the modulation of microsomal cytochrome P450 3A1 (CYP3A1) enzyme activity by various phytochemicals found in Cichorium intybus L., commonly known as chicory. To achieve this goal, several in silico methods, including molecular docking and molecular dynamics (MD) simulation, were employed to explore computationally the microsomal CYP3A1 enzyme. Schrodinger software was utilized for the molecular docking study, which involved the interaction analysis between CYP3A1 and 28 phytoconstituents of Cichorium intybus. Virtual screening of 28 compounds from chicory led to the identification of the top five ranked compounds. These compounds were evaluated for drug-likeness properties, pharmacokinetic profiles, and predicted binding affinities to CYP3A1. Caffeoylshikimic acid and cichoric acid emerged as promising candidates due to their favorable characteristics, including good oral bioavailability and high binding affinities to CYP3A1. Molecular dynamics simulations were conducted to assess the stability of caffeoylshikimic acid within the CYP3A1 binding pocket. The results demonstrated that caffeoylshikimic acid maintained stable interactions with the enzyme throughout the simulation, suggesting its potential as an effective modulator of CYP3A1 activity. The findings of this study have the potential to provide valuable insights into the complex molecular mechanisms by which Cichorium intybus L. acts on hepatocytes and modulates CYP3A1 enzyme expression or activity. By elucidating the impact of these phytochemicals on drug metabolism, this research contributes to our understanding of how chicory may interact with drugs and influence their efficacy and safety profiles.

The renal tubular organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) mediate the vectorial elimination of many drugs and toxins from the kidney, and endogenous biomarkers for vectorial transport (OCT2-MATE1) would allow more accurate drug dosing and help to characterize drug-drug interactions and toxicity. Human serum uptake in OCT2-overexpressing cells and metabolomics analysis were carried out. Potential biomarkers were verified in vitro and in vivo. The specificity of biomarkers was validated in renal transporter overexpressing cells and the sensitivity was investigated by K . The results showed that the uptake of thiamine, histamine, and 5-hydroxytryptamine was significantly increased in OCT2-overexpressing cells. In vitro assays confirmed that thiamine, histamine, and 5-hydroxytryptamine were substrates of both OCT2 and MATE1. In vivo measurements indicated that the serum thiamine level was increased significantly in the presence of the rOCT2 inhibitor cimetidine, and the level in renal tissue was increased significantly by the rMATE1 inhibitor pyrimethamine. There were no significant changes in the uptake or efflux of thiamine in cell lines overexpressed OAT1, OAT2, OAT3, MRP4, organic anion transporting polypeptide 4C1, P-gp, peptide transporter 2, urate transporter 1, and OAT4. The K for thiamine with OCT2 and MATE1 were 71.2 and 10.8 μM, respectively. In addition, the cumulative excretion of thiamine at 2 and 4 h was strongly correlated with metformin excretion (R  > 0.6). Thus, thiamine is preferentially secreted by the OCT2 and MATE1 in renal tubules and can provide a reference value for evaluating the function of the renal tubular OCT2-MATE1.

Renal function is an important factor affecting the pharmacokinetics of vancomycin. The renal function in elderly patients gradually decreases with age. An accurate estimated glomerular filtration rate (GFR) is essential in drug dosing. The study aimed to determine the most appropriate renal function estimation equations to describe vancomycin pharmacokinetics in elderly patients using population pharmacokinetic analysis. Data were obtained retrospectively from elderly patients aged ≥65 years who received vancomycin for infection from September 2016 to January 2022. Renal function was estimated using the Cockcroft-Gault equation (CG), Modification of Diet in Renal Disease equation (MDRD), three Chronic Kidney Disease Epidemiology Collaboration equations (CKD-EPI , CKD-EPI , and CKD-EPI ) and two Berlin Initiative Study equations (BIS-1 and BIS-2). The CKD-EPI and BIS-2 equations were based on cystatin C (Cys C) and serum creatinine (Scr). The others were based on Cys C or Scr. A nonlinear mixed effects model (NONMEM) was used to develop the population pharmacokinetic model. A total of 471 serum concentrations from 313 elderly patients were used to develop the population pharmacokinetic model. Weight and GFR were identified as significant covariates affecting the pharmacokinetics of vancomycin. Cys C and Scr-based GFR (CKD-EPI and BIS-2) yielded significant improvement performance compared with the other equations in model building. The interindividual variability of CL was reduced from 49.4% to 23.6% and 49.4% to 23.7% in CKD-EPI and BIS-2 based models, respectively. However, greater interindividual variabilities of CL (from 26.6% to 29.0%) were represented in the other five models which were based on either Cys C or Scr. The GFR estimated by EPI and BIS-2 equations and vancomycin CL exhibited a good correlation (r = 0.834 and 0.833). In the external validation with 124 serum concentrations, the predictive performances of the CKD-EPI and BIS-2 based models (the mean relative prediction errors were less than 1%, the mean relative absolute prediction errors were about 23%) were also superior to the other five models (the mean relative prediction errors were about 2%, the mean relative absolute prediction errors were greater than 25%) which are based on either Cys C or Scr. In this study, we determined that the equation used to estimate GFR can affect the population pharmacokinetic model fitting result. Population pharmacokinetics model with CKD-EPI or BIS-2 can be used to optimize vancomycin dosage in elderly Chinese patients.

The study aimed to explore the pharmacokinetic and pharmacodynamic alterations of the active components of Shenkang injection (i.e. hydroxy saffron yellow pigment A [HSYA], tanshinol, rheum emodin, and astragaloside IV) in rats with chronic renal failure (CRF), and establish a pharmacokinetic-pharmacodynamic model (PK-PD model) in order to provide a scientific and theoretical basis for the rational clinical use of Shenkang injection. Sprague-Dawley (SD) rats were randomly divided into a normal group, model group, and Shenkang injection group. A rat model of CRF was induced by adenine gavage and then followed by drug administration via tail vein injection. Orbital blood was collected at different timepoints and the blood concentrations of the four active components were measured by UHPLC-Q-Orbitrap HRMS. Serum levels of creatinine (Scr), urea nitrogen (BUN), and uric acid (UA) were determined using an automatic biochemical analyzer. A PK-PD model was established, and DAS 3.2.6 software was used for model fitting as well as statistical analysis. TGF-β1 was utilized to induce normal rat kidney cells to construct a renal fibrosis model to investigate the protective effect of the pharmacological components on renal fibrosis. The pharmacokinetic analysis of hydroxy saffron yellow pigment A, tanshinol, rheum emodin, and astragaloside IV based on UHPLC-Q-Orbitrap HRMS was stable. The linear regression equations for the four active components were as follows: Y = 0.031X + 0.0091 (R  = 0.9986) for hydroxy saffron yellow pigment A, Y = 0.0389X + 0.164 (R  = 0.9979) for tanshinol, Y = 0.0257X + 0.0146 (R  = 0.9973) for rheum emodin, and Y = 0.0763X + 0.0139 (R  = 0.9993) for astragaloside IV, which indicated good linear relationships. The methodological investigation was stable, with the interday and intraday precision RSD <10%. Meanwhile, the recoveries ranged between 90% and 120%, in accordance with the requirements for in vivo analysis of drugs. Compared with the model group, the levels of Scr, BUN, and UA were significantly decreased after 20 min in the Shenkang injection group (p < 0.01). The PK-PD model showed that the four active components in the Shenkang injection group could fit well with the three effect measures (i.e. Scr, BUN, and UA), with the measured values similar to the predicted values. The cell model of renal fibrosis showed that the connective tissue growth factor and FN1 protein expression levels were significantly lower in the Shenkang injection group than those in the model group, and the cell fibrosis was improved. The established method for in vivo analysis of Shenkang injection was highly specific, with good separation of the components and simple operation. The total statistical moment could well integrate the pharmacokinetic parameters of the four active components. After treatment with Shenkang injection, all indexes in the administered group improved and showed significant inhibition of renal cell fibrosis in vitro. This study could provide scientific reference ideas for the clinical rational use of traditional Chinese medicine.

CYP2C19 is a member of the human microsomal cytochrome P450 (CYP). Significant variation in CYP2C19 levels and activity can be attributed to polymorphisms in this gene. Wildtype CYP2C19 and 13 mutants (CYP2C19.1B, CYP2C19.5A, CYP2C19.5B, CYP2C19.6, CYP2C19.8, CYP2C19.9, CYP2C19.10, CYP2C19.11, CYP2C19.13, CYP2C19.16, CYP2C19.19, CYP2C19.23, CYP2C19.30, and CYP2C19.33) were coexpressed with NADPH-cytochrome P450 reductase in Escherichia coli. Hydroxylase activity toward testosterone and progesterone was also examined. Ten CYP2C19 variants showed Soret peaks (450 nm) typical of P450 in the reduced CO-difference spectra. CYP2C19.11 and CYP2C19.23 showed higher testosterone 11α, 16α-/17- and progesterone 6β-,21-,16α-/17α-hydroxylase activities than CYP2C19.1B. CYP2C19.6, CYP2C19.16, CYP2C19.19, and CYP2C19.30 showed lower activity than CYP2C19.1B. CYP2C19.9, CYP2C19.10. CYP2C19.13, and CYP2C19.33 showed different hydroxylation activities than CYP2C19.1B. These results indicated that CYP2C19 variants have very different substrate specificities for testosterone and progesterone.

Model-informed drug development is an important area recognized by regulatory authorities and is gaining increasing interest from the generic drug industry. Physiologically based biopharmaceutics modeling (PBBM) is a valuable tool to support drug development and bioequivalence assessments. This study aimed to utilize an artificial neural network (ANN) with a multilayer perceptron (MLP) model to develop a sustained-release matrix tablet of metformin HCl 500 mg, and to test the likelihood of the prototype formulation being bioequivalent to Glucophage XR, using PBBM modeling and virtual bioequivalence (vBE). The ANN with MLP model was used to simultaneously optimize 735 formulations to determine the optimal formulation for Glucophage XR release. The optimized formulation was evaluated and compared to Glucophage XR using PBBM modeling and vBE. The optimized formulation consisted of 228 mg of hydroxypropyl methylcellulose (HPMC) and 151 mg of PVP, and exhibited an observed release rate of 42% at 1 h, 47% at 2 h, 55% at 4 h, and 58% at 8 h. The PBBM modeling was effective in assessing the bioequivalence of two formulations of metformin, and the vBE evaluation demonstrated the utility and relevance of translational modeling for bioequivalence assessments. The study demonstrated the effectiveness of using PBBM modeling and model-informed drug development methodologies, such as ANN and MLP, to optimize drug formulations and evaluate bioequivalence. These tools can be utilized by the generic drug industry to support drug development and biopharmaceutics assessments.