Animal Pharmacokinetic Studies Research Articles

Oregano Essential Oil in Livestock and Veterinary Medicine.

With a growing global concern over food safety and animal welfare issues, the livestock and veterinary industries are undergoing unprecedented changes. These changes have not only brought challenges within each industry, but also brought unprecedented opportunities for development. In this context, the search for natural and safe products that can effectively replace traditional veterinary drugs has become an important research direction in the fields of animal husbandry and veterinary medicine. Oregano essential oil (OEO), as a natural extract, is gradually emerging in the fields of animal husbandry and veterinary medicine with its unique antibacterial, antioxidant, and multiple other biological activities. OEO not only has a wide antibacterial spectrum, effectively fighting against a variety of pathogenic microorganisms, but also, because of its natural properties, helps us to avoid traditional veterinary drugs that may bring drug residues or cause drug resistance problems. This indicates OEO has great application potential in animal disease treatment, animal growth promotion, and animal welfare improvement. At present, the application of OEO in the fields of animal husbandry and veterinary medicine has achieved preliminary results. Studies have shown that adding OEO to animal feed can significantly improve the growth performance and health status of animals and reduce the occurrence of disease. At the same time, pharmacokinetic studies in animals show that the absorption, distribution, metabolism, and excretion processes of OEO in animals shows good bioavailability. In summary, oregano essential oil (OEO), as a substitute for natural veterinary drugs with broad application prospects, is gradually becoming a research hotspot in the field of animal husbandry and veterinary medicine. In the future, we look forward to further tapping the potential of OEO through more research and practice and making greater contributions to the sustainable development of the livestock and veterinary industries.

Effect of Deep Eutectic System (DES) on Oral Bioavailability of Celecoxib: In Silico, In Vitro, and In Vivo Study.

Different deep eutectic systems (DES) of choline chloride (CC)-urea (UA) (1:2), CC-glycerol (GLY) (1:2), CC-malonic acid (MA) (1:1), and CC-ascorbic acid (AA) (2:1) were generated and characterized by polarized light microscope (PLM) and Fourier transform infrared spectroscope (FTIR). The equilibrium solubility of celecoxib (CLX) in DES was compared to that in deionized water. The CC-MA (1:1) system provided ~10,000 times improvement in the solubility of CLX (13,114.75 µg/g) and was used for the generation of the CLX-DES system. The latter was characterized by PLM and FTIR to study the microstructure and intermolecular interaction between the CLX and CC-MA (1:1) DES. FTIR demonstrated the retention of the chemical structure of CLX. In vitro drug release studies in FaSSIF initially demonstrated high supersaturation, which decreased by ~2 fold after 2 h. Density functional theory (DFT)-based calculations provided a molecular-level understanding of enhanced solubility. Gibbs free energy calculations established the role of the strongest binding of CLX with CC and MA. A phase solubility study highlighted the role of hydrotropy-induced solubilization of the CLX-DES system. Animal pharmacokinetic studies established 2.76 times improvement in Cmax, 1.52 times reduction in tmax, and 1.81 times improvement in AUC0-∞. The overall results demonstrated the potential of developing a DES-based supersaturating drug-delivery system for pharmaceutical loading of drugs having solubility and dissolution rate-limited oral bioavailability.

Machine Learning Models for Human In Vivo Pharmacokinetic Parameters with In-House Validation.

Prior to clinical development, a comprehensive pharmacokinetic characterization of a novel drug is required to understand its exposure at the site of action and elimination. Accordingly, in vitro assays and animal pharmacokinetic studies are regularly employed to predict drug exposure in humans, which is often costly and time-consuming. For this reason, the prediction of human pharmacokinetics at the point of design would be of high value for drug discovery. Therefore, we have established a comprehensive data curation protocol that enables machine learning evaluation of 12 human in vivo pharmacokinetic parameters using only chemical structure information and available doses for 1001 unique compounds. These machine learning models were thoroughly investigated and validated using both an independent hold-out test set and AstraZeneca clinical data. In addition, the availability of preclinical predictions for a subset of internal clinical candidates allowed us to compare our in silico approach with state-of-the-art pharmacokinetic predictions. Based on this evaluation, three fit-for-purpose models for AUC PO (Rtest2 = 0.63; RMSEtest = 0.76), Cmax PO (Rtest2 = 0.68; RMSEtest = 0.62), and Vdss IV (Rtest2 = 0.47; RMSEtest = 0.50) were identified. Based on the findings, our machine learning models have considerable potential for practical applications in drug discovery, such as influencing decision-making in drug discovery projects and progression of drug candidates toward the clinic.

Retinoic acid-conjugated chitosan/manganese porphyrin ionic-complex nanoparticles for improved T1 contrast MR imaging of hepatic fibrosis.

Noninvasive and precise diagnosis of hepatic fibrosis is very important for the preventive therapeutic regimen of hepatic cirrhosis and cancer. In this study, we fabricated T1 contrast Mn-porphyrin (MnTPPS4 )/retinoic acid-chitosan ionic-complex nanoparticles (MRC NPs). The functional properties of MRC NPs were evaluated via transmission electron microscopy (TEM) imaging, release study, cytotoxicity assay, hepatocyte-specific uptake assay, and magnetic resonance (MR) imaging study. TEM images confirmed the typical structure of an ionic-complex NPs with around 100-200 nm of diameter. MnTPPS4 is released from MRC NPs for up to 24 hr in controlled pattern which implies that more reliable and convenient hepatic MR imaging is possible using of MRC NPs in clinical practice. Hepatocytes uptake assay proved retinoic acid-specific targeting of MRC NPs. The same results were observed in animal pharmacokinetic studies. In vitro MR phantom study, MRC NPs showed an increased T1 relaxivity (r1 =6.772 mM-1 s-1 ) in comparison with 3.242 mM-1 s-1 of MnTPPS4 . The result was confirmed again in vivo MR imaging studies. Taken together, MRC NPs displayed a potential for noninvasive diagnostic T1 MR imaging of hepatic fibrosis with improved target specificity and prolonged MR imaging time window.

Characterization of Antibody-Drug Conjugate Pharmacokinetics and in Vivo Biotransformation Using Quantitative Intact LC-HRMS and Surrogate Analyte LC-MRM.

Antibody-drug conjugates (ADCs) pose challenges to bioanalysis because of their inherently intricate structures and potential for very complex catabolism. Common bioanalysis strategy is to measure the concentration of ADCs and Total Antibody (Ab) as well as deconjugated warhead in circulation. The ADCs and the Total Ab can be quantified with ligand binding assays (LBA) or with hybrid immunocapture-liquid chromatography coupled with multiple reaction monitoring mass spectrometry (LBA-LC-MRM). With the LBA-LC-MRM approach, a surrogate analyte, often the signature peptide, and released warhead can be used for the quantification of the Total Ab and ADCs, respectively. Recent advances in analytical instrumentation, especially the development of high resolution mass spectrometers (HRMS), have enabled characterization and quantification of intact macromolecules such as ADCs. The LBA-LC-HRMS approach employs immunocapture, followed by chromatographic separation at the macromolecule level and detection of the intact analyte. We developed an intact quantification method with 1-10 μg/mL linear dynamic range using 25 μL of plasma sample volume. This method was qualified for the measurement of naked monoclonal antibody (mAb), a site-specific cysteine-conjugated ADC with drug to antibody ratio ∼2 (DAR2) and a site-nonspecific cysteine-conjugated ADC (DAR8) in rat plasma. Samples from a rat pharmacokinetic (PK) study were analyzed with both methods. For the naked mAb, the results from both assays matched well. For ADCs, new species were observed from the LBA-HRMS method. The results demonstrated that potential biotransformation of the ADC was unveiled using the intact quantification approach while not being observed with traditional LBA-LC-MRM approach. Our work demonstrated an application of novel intact quantification by supporting animal PK studies. Moreover, our results suggest that the intact quantification method can provide novel perspectives on ADC in vivo characterization and quantification, which can benefit future drug candidate optimization as well as the immunogenicity impact evaluation and safety assessment.

Fast and reliable ICP-MS quantification of palladium and platinum-based drugs in animal pharmacokinetic and biodistribution studies

Palladium-(Pd)-based drugs are emerging as alternatives to platinum (Pt) anticancer chemotherapeutics, which increases the need for efficient and suitable procedures of Pd analysis in reduced amounts of pre-clinical animal samples. Herein, an ICP-MS (inductively coupled plasma-mass spectrometry) method was developed and validated for simple and fast analysis of Pd/Pt-based drugs in 11 distinct biological matrices (adipose tissue, muscle, liver, kidney, spleen, testis, heart, lungs, brain, blood and serum). The critical variables affecting sample preparation and Pd/Pt extraction were optimized using two-level (2k) factorial and central composite designs. Biological samples (50 mg) were digested in closed tubes with a screw cap, using a 3 : 1 (v/v) mixture of nitric acid (900 μL) and hydrochloric acid (300 μL) for 60 min in a 90 °C water bath. Full method validation using in-house materials showed a LOD of 0.001 μg L-1, linear dynamic range from 0.025-10 μg L-1 (R2 = 0.9999 for Pd; R2 = 0.9998 for Pt), good repeatability (CV: 0.02-1.9%) and intermediate precision (CV: 0.52-1.53%) for both the studied metals. The accuracy ranged from 83.5-105.1% considering microwave-assisted digestion as the reference method. The developed and validated method allows the processing of hundreds of biological samples simultaneously, with low reagent and sample consumption. Therefore, the method is highly suitable for analysis of novel Pd/Pt-based drugs in pharmaco-toxicokinetic and biodistribution animal studies that involve a large number of multi-organ samples.

Abstract 1292: A new generation of N-terminal domain androgen receptor inhibitors, with improved pharmaceutical properties, in castration-resistant prostate cancer models

Abstract Introduction: The androgen receptor (AR) pathway continues to drive castration-resistant prostate cancer (CRPC) even in late stages of the disease, and ligand binding domain (LBD)-linked resistance inevitably emerges. Selective inhibition of the N-terminal domain (NTD) of the AR can inhibit its’ transcription even in the presence of anti-androgen resistance. A Phase I clinical trial of the first-generation AR NTD inhibitor, EPI-506 (EPI-002 pro-drug), demonstrated PSA declines in anti-androgen resistant metastatic CRPC patients. However, these declines were minor and of short duration, revealing the need for more potent and metabolically stable NTD inhibitors. A new generation of NTD transcriptional inhibitors (Anitens) has been generated. Examples of this new class, EPI-7170 and EPI-7245, demonstrate improved potency, metabolic stability and pharmaceutical properties, and are potent against anti-androgen resistant prostate cancers in in vitro and in preclinical models. Methods: Chemical structure activity relationships were developed to identify more potent molecules as measured by both cellular and in vivo assays, while metabolic stability improvements were assessed in in vitro ADME assays and in animal pharmacokinetic studies. In addition, the on-target activity and selectivity were also optimized using a variety of cellular experiments. Results: These next generation Anitens demonstrated a 10-20-fold improvement on AR-driven cellular potency, with IC50’s of 0.5-1 uM compared to 10 uM for EPI-002. Aniten AR inhibition was specific to the NTD, as demonstrated by the absence of LBD binding and the inhibition of the AR-V7-driven transcription inLNCaP95 model. In vitro proliferation assays demonstrated AR-dependent activity, with an IC50 ~ 1 uM in LNCaP and >10 uM in the AR-independent cell model PC-3. The antiproliferative effect aligned with the inhibitory effect on a subset of AR-driven genes. In vivo, next generation Anitens demonstrated PSA serum decreases along with significant tumor growth inhibition in mice bearing LNCaP tumors. While EPI-7170 represents a major advance, subsequent chemistry efforts led to the generation of EPI-7245 and other next generation Anitens which exhibit IC50’s <500 nM. These new compounds exhibited favorable ADME and PK profiles, with half-life ~ 8 hrs in mice, and predicted low human clearance. Conclusions: Promising next-generation Aniten compounds have been identified which retain the NTD specificity of first-generation agents. These new molecules demonstrate major improvements in potency and metabolic stability in comparison to the first-generation clinical compound EPI-002. These next generation Anitens, by selectively inhibiting AR transcription in both hormone sensitive and castrated resistant prostate cancer, represent an important next step in AR targeted therapeutics. Citation Format: Ronan Le Moigne, Nasrin R. Mawji, C. Adriana Banuelos, Jun Wang, Kunzhong Jian, Raymond J. Andersen, Marianne D. Sadar, Han-Jie Zhou, Peter Virsik. A new generation of N-terminal domain androgen receptor inhibitors, with improved pharmaceutical properties, in castration-resistant prostate cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1292.

Next generation N-terminal domain androgen receptor inhibitors with improved potency and metabolic stability in castration-resistant prostate cancer models.

220 Background: EPI-506, pro-drug of EPI-002, was a first-in-class oral small molecule from the Aniten family of compounds, which inhibit androgen receptor (AR) activity by binding to the N-terminal domain of the AR. EPI-506 was tested in a Phase 1 study in men with metastatic castration-resistant prostate cancer (mCRPC) resistant to current therapies and demonstrated a favorable tolerability profile with signs of moderate efficacy. Metabolic vulnerabilities in the chemical scaffold of EPI-506 were identified and new Aniten molecules, EPI-7170 and EPI-7245 , with improved potency, metabolic stability and pharmaceutical properties have been generated. Methods: Chemical structure activity relationships were developed in order to increase molecule potency in cellular and in vivo assays, while metabolic stability improvements were assessed in in vitro ADME assays and in animal pharmacokinetic studies. In addition, the on-target activity and selectivity was also optimized using a variety of cellular experiments. Results: Next generation Anitens demonstrated a 10-20 fold improvement on AR-driven cellular potency, with IC50’s of 0.5-1 uM when compared to 10-12 uM for EPI-002. In vitro proliferation assays demonstrated on target activity, with an IC50 ~ 2 uM in LNCaP and > 10 uM in the AR-independent cell model PC-3. EPI-7170 was also active in AR-V7-driven LNCaP95 cells. The antiproliferative effect was in alignment with the inhibitory effect on a subset of AR driven genes. In vivo activity in castrated mice bearing LNCaP tumors showed tumor growth inhibition of approximately 70%. While EPI-7170 represents a major advance, subsequent chemistry efforts led to the generation of EPI-7245 and other next generation Anitens which exhibit IC50’s < 500 nM and favorable ADME and PK profiles. Conclusions: Promising next-generation Aniten compounds have been identified. Major chemistry efforts led to the identification of several Anitens with > 10-20 fold improvements in cellular potency compared to EPI-506 which are also metabolically stable. IND-selection preclinical studies are underway on the most promising Aniten’s with an IND submission planned shortly.

Using mathematical modeling to infer the valence state of arsenicals in tissues: A PBPK model for dimethylarsinic acid (DMAV) and dimethylarsinous acid (DMAIII) in mice

Chronic exposure to inorganic arsenic (iAs), a contaminant of water and food supplies, is associated with many adverse health effects. A notable feature of iAs metabolism is sequential methylation reactions which produce mono- and di-methylated arsenicals that can contain arsenic in either the trivalent (III) or pentavalent (V) valence states. Because methylated arsenicals containing trivalent arsenic are more potent toxicants than their pentavalent counterparts, the ability to distinguish between the +3 and +5 valence states is a crucial property for physiologically based pharmacokinetic (PBPK) models of arsenicals to possess if they are to be of use in risk assessment. Unfortunately, current analytic techniques for quantifying arsenicals in tissues disrupt the valence state; hence, pharmacokinetic studies in animals, used for model calibration, only reliably provide data on the sum of the +3 and +5 valence forms of a given metabolite. In this paper we show how mathematical modeling can be used to overcome this obstacle and present a PBPK model for the dimethylated metabolite of iAs, which exists as either dimethylarsinous acid, (CH3)2AsIIIOH (abbreviated DMAIII) or dimethylarsinic acid, (CH3)2AsV(O)OH (abbreviated DMAV). The model distinguishes these two forms and sets a lower bound on how much of an organ's DMA burden is present in the more reactive and toxic trivalent valence state. We conjoin the PBPK model to a simple model for DMAIII-induced oxidative stress in liver and use this extended model to predict cytotoxicity in liver in response to the high oral dose of DMAV. The model incorporates mechanistic details derived from in vitro studies and is iteratively calibrated with lumped-valence-state PK data for intravenous or oral dosing with DMAV. Model formulation leads us to predict that orally administered DMAV undergoes extensive reduction in the gastrointestinal (GI) tract to the more toxic trivalent DMAIII.

PHARMACOKINETICS OF MELOXICAM FOLLOWING A SINGLE ORAL DOSE IN MALAYAN FLYING FOXES ( PTEROPUS VAMPYRUS).

Meloxicam, a COX-2 selective nonsteroidal anti-inflammatory medication, has been used in many exotic animals at doses extrapolated from domestic animal pharmacokinetic and pharmacodynamic studies. Increasing evidence suggests that significant species differences exist in meloxicam metabolism. Because of this, dose extrapolation from domestic animals may not be appropriate for exotic species. The objective of this study was to investigate the pharmacokinetics of meloxicam in a population of male Malayan flying foxes, Pteropus vampyrus, following a single oral dose of 0.2 mg/kg. Using a sparse sampling method based on a pilot study, two blood samples from each of 10 bats were collected over an 8-hr time period. Analysis of meloxicam in plasma samples was conducted using reversed-phase high-performance liquid chromatography. The peak plasma concentration of 598 ± 157.5 ng/ml occurred at 1.0 hr post dosing. The terminal half-life was 1.1 ± 0.1 hr, which indicates that meloxicam is rapidly metabolized in this species. No adverse clinical effects were noted during the study period. A single oral dose of 0.2 mg/kg appears safe for use in male Malayan flying foxes, but due to rapid elimination, frequent dosing may be required to maintain plasma concentrations within a therapeutic range. Multidose studies are needed to determine if plasma accumulation of meloxicam occurs.

LC-MS/MS method for the determination of the prodrug aripiprazole lauroxil and its three metabolites in plasma and its application to in vitro biotransformation and animal pharmacokinetic studies

A sensitive and selective LC-MS/MS method for determination of the prodrug aripiprazole lauroxil (AL) and the three metabolites (N-hydroxymethyl aripiprazole [NHA], aripiprazole [ARP], and dehydro aripiprazole [DHA]) in plasma was developed using ARP-d8 as an internal standard. The analytes were determined on an AB Sciex Triple Quad™ 4500 system using positive ion electrospray ionization and selected multiple reaction monitoring mode. Solid phase extraction was applied for sample preparation for AL, ARP, and DHA, and protein precipitation for NHA. Chromatographic separation was performed on an Agilent Eclipse XDB-CN column (100 × 2.1 mm i.d., 3.5 μm) using the mobile phase of water and acetonitrile (25:75, v/v) containing 0.1% formic acid with a flow rate of 0.5 mL/min. The linear ranges for AL, NHA, ARP, and DHA were 0.5–50 ng/mL, 1.0–50 ng/mL, 0.5–50 ng/mL, and 0.05–5.0 ng/mL, respectively. The average recovery in the plasma sample was stable and reproducible. The precision and accuracy of the intra- and inter-run were within assay variability criteria limits. The developed method was suitable for in vitro biotransformation studies in plasma and animal pharmacokinetic studies after intramuscular injection of AL formulations.

Development of Nanoemulsion Based Gel Loaded with Phytoconstituents for the Treatment of Urinary Tract Infection and in Vivo Biodistribution Studies.

Purpose: A nanoemulsion based gel containing Polyphenon 60 (P60) and cranberry (CRB) has been developed to deliver via intravaginal route for the treatment of urinary tract infection.Methods: Polyphenon 60 and cranberry were loaded in a single nanoemulsion gel (NBG) by ultra-sonication method and characterized for particle size, rheological properties, in vitro release and growth curve analysis. P60+CRB NBG were radiolabelled using technetium pertechnetate (99mTc) to perform in vivo pharmacokinetic studies in animals.Results: The finalized NE had a droplet size of 58±1 nm. In vitro release of 90.92 ± 0.6% in 8 hr for P60 and 99.39 ± 0.5% in 6 hr for CRB was observed in simulated vaginal fluid. Growth curve of E. coli indicated the inhibitory action of nanoemulsion based gel at the fifth hour of inoculation. Gamma scintigraphy studies on female Sprague-Dawley rats showed transport of nanoemulsion based gel from the vaginal cavity into the systemic circulation. Further, biodistribution studies with radiolabelled P60+CRB NBG showed significant higher uptake of radiolabelled actives by kidney (3.20±0.16) and urinary bladder (3.64±0.29), when administered intravaginally.Conclusion: The findings suggested 99mTc-P60+CRB NBG can potentially be transported through vaginal cavity and reach the target organs and showed effective distribution in organs affected in urinary tract infection

Liquid chromatography tandem-mass spectrometry (LC-MS/MS) and dried blood spot sampling applied to pharmacokinetics studies in animals: Correlation of classic and block design

A relative bioavailability study (RBA) of two phenytoin (PHT) formulations was conducted in rabbits, in order to compare the results obtained from different matrices (plasma and blood from dried blood spot (DBS) sampling) and different experimental designs (classic and block). The method was developed by liquid chromatography tandem-mass spectrometry (LC-MS/MS) in plasma and blood samples. The different sample preparation techniques, plasma protein precipitation and DBS, were validated according to international requirements. The analytical method was validated with ranges 0.20-50.80 and 0.12-20.32 µg ml-1, r > 0.999 for plasma and blood, respectively. Accuracy and precision were within acceptance criteria for bioanalytical assay validation (< 15 for bias and CV% and < 20 for limit of quantification (LOQ)). PHT showed long-term stability, both for plasma and blood, and under refrigerated and room temperature conditions. Haematocrit values were measured during the validation process and RBA study. Finally, the pharmacokinetic parameters (Cmax, Tmax and AUC0-t) obtained from the RBA study were tested. Results were highly comparable for matrices and experimental designs. A matrix correlation higher than 0.975 and a ratio of (PHT blood) = 1.158 (PHT plasma) were obtained. The results obtained herein show that the use of classic experimental design and DBS sampling for animal pharmacokinetic studies should be encouraged as they could help to prevent the use of a large number of animals and also animal euthanasia. Finally, the combination of DBS sampling with LC-MS/MS technology showed to be an excellent tool not only for therapeutic drug monitoring but also for RBA studies.

Study of Jadomycin Pharmacokinetics in Balb/C Mice

BackgroundJadomycins are natural product molecules derived from the soil bacteria Streptomyces venezuelae; jadomycins maintain their cytotoxicity in multidrug resistant (MDR) human and mouse breast cancer cell lines that overexpress ATP‐binding cassette (ABC) transporters. While effective in in vitro assays, jadomycins have not been studied in animal models.ObjectiveTo conduct the first in animal pharmacokinetic and safety studies of jadomycins B, S, and F in male and female Balb/C mice.MethodsJadomycins were administered intraperitoneally (IP) to male and female Balb/C mice at a 6mg/kg dose. In one group of mice (n = 5) up to four repeated saphenous vein blood samples (40 mL) were obtained after 15, 30, 60, and 90 minutes with terminal blood collection occurring at 120 minutes in order to characterize absorption and distribution phases. In a second group of mice saphenous vein blood samples were obtained at 2, 4, 6, 8 and 10 hours to characterize terminal elimination. Liver, kidney, lung and brains were collected after 2 hours and then at 8 or 10 hours (males and females respectively) to characterize jadomycin distribution to these tissues. Serum and tissue samples underwent extraction and jadomycin concentrations were then determined by mass spectrometry.ResultsThe concentration versus time profiles of jadomycins B, S and F were similar. They were absorbed rapidly after IP injection with peak concentrations in the 1–10 mM range observed after 15 minutes. This was followed by a rapid distribution phase (t1/2a = 20 – 40 min) and a slower terminal elimination (t1/2b = 1.5 – 2 hours). Jadomycins accumulated in the liver &gt; kidney &gt; lung and were not detectable in the brain. No metabolites were detected and no acute toxicity responses were observed.ConclusionsThese 1st in vivo studies of jadomycins reveal that jadomycins are safe at a 6 mg/kg IP dose and achieve concentrations in mouse serum that are above the IC50s (1–4 μM) for human and mouse breast cancer cells in vitro. Our results indicate that jadomycins are rapidly eliminated as unchanged drug and that two to three times daily dosing will be required for future tumor studies.Support or Funding InformationCancer Research Training Program (CRTP) through Beatrice Hunter Cancer Research Institute, Canadian Breast Cancer Foundation Atlantic (CBCF), Nova Scotia Health Research Foundation (NSHRF), and Dalhousie University

Prediction of Plasma Concentration-time Profiles of Drugs in Humans from Animals Following Oral Administration: An Allometric Approach.

Allometric scaling is regularly used for the prediction of human pharmacokinetic (PK) parameters from animal PK studies. The predicted human PK parameters can also be used for the prediction of plasma concentration-time profiles in humans. The main objective of this work is to predict human concentration-time profiles of drugs (one-compartment model) following oral administration using animal oral pharmacokinetic parameters. Six drugs from the literature were chosen that were described by one-compartment model in both humans and animals following oral administration. Pharmacokinetic parameters such as oral clearance, oral volume of distribution of the central compartment, time to reach maximum plasma concentration, absorption rate constant, and half-life in humans were predicted from animals using allometric scaling. These predicted human pharmacokinetic parameters were then used to predict human plasma concentrations-time profiles of drugs. The results of this study indicate that the proposed method can be used to predict human plasma concentrations- time profiles of drugs with reasonable accuracy (≤50% prediction error). Given the complexity in the pharmacokinetics of oral drugs there remains some uncertainty in this entire exercise. One can minimize the prediction error by experience in allometric scaling, scientific judgment, and unconventional or innovative thinking.

Modeling Mass Transfer from Carmustine-Loaded Polymeric Implants for Malignant Gliomas

Significant advances in the encapsulation and release of drugs from degradable polymers have led to the Food and Drug Administration approval of Gliadel wafers for controlled local delivery of the chemotherapeutic drug carmustine to high-grade gliomas following surgical resection. Due to the localized nature of the delivery method, no pharmacokinetic measurements have been taken in humans. Rather, pharmacokinetic studies in animals and associated modeling have indicated the capability of carmustine to be delivered in high concentrations within millimeters from the implant site over approximately 5 days. Mathematical models have indicated that diffusion has a primary role in transport, which may be complemented by enhanced fluid convection from postsurgical edema in the initial 3 days following implantation. Carmustine's penetration distance is also presumably limited by its lipophilicity and permeability in the capillaries. This review discusses the mathematical models that have been used to predict the release and distribution of carmustine from a polymeric implant. These models provide a theoretical framework for greater understanding of systems for localized drug delivery while highlighting factors that should be considered in clinical applications. In effect, Gliadel wafers and similar drug delivery implants can be optimized with reduction in required time and resources with such a quantitative and integrative approach.

Complex Encounters: Nanoparticles in Whole Blood and Their Uptake Into Different Types of White Blood Cells

A whole blood assay for evaluating the uptake of nanoparticles into white blood cells in order to close the gap between basic studies in cell culture and pharmacokinetic studies in animals was developed. After drawing peripheral blood into standard blood collection vials with different anticoagulants, amino- and carboxy-functionalized polymeric styrene nanoparticles were added and uptake was evaluated by flow cytometry. By counterstaining surface markers of leukocytes (e.g., monocytes, neutrophil granulocytes, B or T lymphocytes), investigations of different cell types can be conducted in a single run by flow cytometry. The authors demonstrated that anticoagulation should be done with heparin, and not EDTA, in order to prevent hampering of uptake mechanisms. By using heparinized whole blood, the authors demonstrated differences and usefulness of this assay for screening cellular uptake as it should occur in the bloodstream. Nevertheless, animal studies are warranted for final assessment of the nanoparticles.

Preliminary evaluation of technetium-99m-labeled ceftriaxone: infection imaging agent for the clinical diagnosis of orthopedic infection

In this study we sought to assess the efficacy of a technetium-99m (Tc-99m)-labeled third-generation cephalosporin as an infection imaging agent in the accurate detection of the sites of bacterial infection in vivo. Ceftriaxone (CRO) was formulated into a ready-to-use single-vial cold kit with a shelf-life of over 6 months and was successfully labeled with technetium. The radiolabeled drug, Tc-99m-CRO, was subjected to the following preclinical evaluations: radiochemical purity, in vitro and in vivo stability, bacterial binding assay, and pharmacokinetic studies in animals and in human patients. The kit formulation exhibited excellent radiolabeling efficiency (∼99%) and high in vitro and in vivo stability. The radiolabeled drug exhibited slow blood clearance (12% at 4 h), and the high protein binding and excretion pattern of the labeled formulation mimics the reported pharmacokinetic profile of the drug alone. In the animal model, scintigraphy scans showed higher uptake of the radiopharmaceutical in infectious lesions, even at 1 h post-administration, in comparison to inflammatory lesions. The clinical evaluation of Tc-99m-labeled CRO showed a diagnostic accuracy of 83.3%, and a sensitivity and specificity of 85.2% and 77.8%, respectively. This kit formulation has the potential for imaging bacterial infections with much higher sensitivity and specificity as compared to other Tc-99m-labeled antibiotics available as convenient ready-to-use kits in routine clinical practice.

Case Studies for Practical Food Effect Assessments across BCS/BDDCS Class Compounds using In Silico, In Vitro, and Preclinical In Vivo Data

Practical food effect predictions and assessments were described using in silico, in vitro, and/or in vivo preclinical data to anticipate food effects and Biopharmaceutics Classification System (BCS)/Biopharmaceutics Drug Disposition Classification System (BDDCS) class across drug development stages depending on available data: (1) limited in silico and in vitro data in early discovery; (2) preclinical in vivo pharmacokinetic, absorption, and metabolism data at candidate selection; and (3) physiologically based absorption modeling using biorelevant solubility and precipitation data to quantitatively predict human food effects, oral absorption, and pharmacokinetic profiles for early clinical studies. Early food effect predictions used calculated or measured physicochemical properties to establish a preliminary BCS/BDDCS class. A rat-based preclinical BCS/BDDCS classification used rat in vivo fraction absorbed and metabolism data. Biorelevant solubility and precipitation kinetic data were generated via animal pharmacokinetic studies using advanced compartmental absorption and transit (ACAT) models or in vitro methods. Predicted human plasma concentration-time profiles and the magnitude of the food effects were compared with observed clinical data for assessment of simulation accuracy. Simulations and analyses successfully identified potential food effects across BCS/BDDCS classes 1-4 compounds with an average fold error less than 1.6 in most cases. ACAT physiological absorption models accurately predicted positive food effects in human for poorly soluble bases after oral dosage forms. Integration of solubility, precipitation time, and metabolism data allowed confident identification of a compound's BCS/BDDCS class, its likely food effects, along with prediction of human exposure profiles under fast and fed conditions.

Formulation and delivery of improved amorphous fenofibrate solid dispersions prepared by thin film freezing

The objective of this study was to prepare amorphous fenofibrate (FB) solid dispersions using thin film freezing (TFF) and to incorporate the solid dispersions into pharmaceutically acceptable dosage forms. FB solid dispersions prepared with optimized drug/polymer ratios were characterized by modulated differential scanning calorimetry (MDSC), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) specific surface area measurements, Fourier-transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), and supersaturation dissolution testing. Furthermore, a dry granulation technique was used to encapsulate the TFF compositions for in vitro dissolution and in vivo animal pharmacokinetic studies. The results showed that the TFF process produced amorphous, porous, microstructured, and stable solid dispersions with high surface areas. Development of solid oral dosage forms revealed that the performance of the FB containing solid dispersions was not affected by the formulation process, which was confirmed by DSC and XRD. Moreover, an in vivo pharmacokinetic study in rats revealed a significant increase in FB absorption compared to bulk FB. We confirmed that amorphous solid dispersions with large surface areas produced by the TFF process displayed superior dissolution rates and corresponding enhanced bioavailability of the poorly water-soluble drug, FB.