Pharmacokinetics of dexamethasone in a rat model of rheumatoid arthritis

The history and future of population pharmacokinetic analysis in drug development

1. The analysis of pharmacokinetic data has been in a constant state of evolution since the introduction of the term pharmacokinetics. Early work focused on mechanistic understanding of the absorption, distribution, metabolism and excretion of drug products.2. The introduction of non-linear mixed effects models to perform population pharmacokinetic analysis initiated a paradigm shift. The application of these models represented a major shift in evaluating variability in pharmacokinetic parameters across a population of subjects.3. While technological advancements in computing power have feuled the growth of population pharmacokinetics in drug development efforts, there remain many challenges in reducing the time required to incorporate these learnings into a model-informed development process. These challenges exist because of expanding datasets, increased number of diagnostics, and more complex mathematical models.4. New machine learning tools may be potential solutions for these challenges. These new methodologies include genetic algorithms for model selection, machine learning algorithms for covariate selection, and deep learning models for pharmacokinetic and pharmacodynamic data. These new methods promise the potential for less bias, faster analysis times, and the ability to integrate more data.5. While questions remain regarding the ability of these models to extrapolate accurately, continued research in this area is expected to address these questions.

Route of dexamethasone administration influences parasite burden in Strongyloides hyperinfection model

Rodents infected with Strongyloides venezuelensis are experimental models applied to strongyloidiasis research. This study evaluated oral and subcutaneous dexamethasone (DEX) treatments to establish immunosuppression in an experimental model of Strongyloides hyperinfection. Rattus norvegicus Wistar were divided: G I (-): untreated and uninfected animals, G II (+): untreated and infected, G III (o -) orally treated and uninfected, G IV (o +) orally treated and infected, G V (sc -) subcutaneously treated and uninfected, G VI (sc +) subcutaneously treated and infected. For oral administration, DEX was diluted in sterile water (5 µg/ml) and made available to the animals on intervals in experimental days - 5-0, 8-13 and 21-26. For subcutaneous administration, animals received daily injections of DEX disodium phosphate (2 mg/kg). Infection was established by the subcutaneous inoculation of 3000 S. venezuelensis filarioid larvae. Groups were evaluated by egg per gram of feces and parasite females counts and IgG, IgG1 and IgG2a detection. GIV (o +) had egg peaks count on days 13 and 26 and maintained egg elimination until the last experimental day. Parasitic females recovery at day 30 was significantly higher in G IV (o +) when compared to G VI (sc +). Levels of IgG, IgG1 and IgG2a of all groups, except the positive control GII (+), were below the detection threshold. Pharmacological immunosuppression induced by oral administration of DEX produced high parasitic burden, and is a noninvasive method, useful to establish immunosuppression in strongyloidiasis hyperinfection model in rats.

Pharmacokinetic/Pharmacodynamic Modeling of Dexamethasone Anti-Inflammatory and Immunomodulatory Effects in LPS-Challenged Rats: A Model for Cytokine Release Syndrome

Dexamethasone (DEX) is a potent synthetic glucocorticoid used for the treatment of variety of inflammatory and immune-mediated disorders. The RECOVERY clinical trial revealed benefits of DEX therapy in COVID-19 patients. Severe SARS-CoV-2 infection leads to an excessive inflammatory reaction commonly known as a cytokine release syndrome that is associated with activation of the toll like receptor 4 (TLR4) signaling pathway. The possible mechanism of action of DEX in the treatment of COVID-19 is related to its anti-inflammatory activity arising from inhibition of cytokine production but may be also attributed to its influence on immune cell trafficking and turnover. This study, by means of pharmacokinetic/pharmacodynamic modeling, aimed at the comprehensive quantitative assessment of DEX effects in lipopolysaccharide-challenged rats and to describe interrelations among relevant signaling molecules in this animal model of cytokine release syndrome induced by activation of TLR4 pathway. DEX was administered in a range of doses from 0.005 to 2.25 mg·kg-1 in LPS-challenged rats. Serum DEX, corticosterone (CST), tumor necrosis factor α, interleukin-6, and nitric oxide as well as lymphocyte and granulocyte counts in peripheral blood were quantified at different time points. A minimal physiologically based pharmacokinetic/pharmacodynamic (mPBPK/PD) model was proposed characterizing the time courses of plasma DEX and the investigated biomarkers. A high but not complete inhibition of production of inflammatory mediators and CST was produced in vivo by DEX. The mPBPK/PD model, upon translation to humans, may help to optimize DEX therapy in patients with diseases associated with excessive production of inflammatory mediators, such as COVID-19. SIGNIFICANCE STATEMENT: A mPBPK/PD model was developed to describe concentration-time profiles of plasma DEX, mediators of inflammation, and immune cell trafficking and turnover in LPS-challenged rats. Interrelations among DEX and relevant biomarkers were reflected in the mechanistic model structure. The mPBPK/PD model enabled quantitative assessment of in vivo potency of DEX and, upon translation to humans, may help optimize dosing regimens of DEX for the treatment of immune-related conditions associated with exaggerated immune response.

Therapeutic approaches for anti-sperm-antibodies in the testicular sperm aspiration rat model

Background and Aim: Anti-sperm antibodies (ASAs) treatment continued to be neglected. This study aimed to generate ASAs using the testicular sperm aspiration (TSA) rat model, which allowed for investigation of four distinct therapeutic approaches to find potential treatments for ASAs. Materials and Methods: Adult Wistar albino male rats were divided into six equal groups (n = 12). The negative control group underwent scrotal sac surgery without having their testicles punctured. Punctures were made in the remaining 5 groups, with one group left untreated to serve as the positive control group. The remaining 4 groups were treated with either dexamethasone (DEX), azathioprine (AZA), frankincense, or anti-ASAs secondary antibodies. For 10 weeks, serum samples were collected every 2 weeks for specific quantification of ASAs. Testis and epididymis tissues were collected for histopathological analysis. Results: The ASAs concentrations of the positive controls were significantly higher (p ≤ 0.001) than their negative control counterparts during the examined weeks. However, The ASAs indices (%) differed according to the treatment type. While the ASAs indices at the 2nd and 4th weeks in the AZA-treated group were significantly reduced compared to the positive control group (p ≤ 0.001), no significant differences were observed at any of the sample collection week for the DEX-treated rats. The ASAs indices were significantly decreased only at weeks 6 and 8 of treatment in the frankincense-treated group (p ≤ 0.001). In the secondary antibodies-treated group, the antibody indices were significantly decreased in all weeks except for samples collected at week 4 (p ≤ 0.001). The testosterone levels reverted to normal only in TSA rats treated with either Frankincense or secondary antibodies, as they were significantly higher than the positive controls (p ≤ 0.05). Tissue samples from the secondary antibody-treated rats showed a generally normal histological appearance. Conclusion: This study tried to offer realistic therapy suggestions; however, caution should be applied when extrapolating findings from experimental models to meet clinical requirements.

Thiamine as a peripheral neuro-protective agent in comparison with N-acetyl cysteine in axotomized rats

Objectives

In this study, the impact of thiamine (Thi), N-acetyl cysteine (NAC), and dexamethasone (DEX) were investigated in axotomized rats, as a model for neural injury.

Materials and Methods

Sixty-five axotomized rats were divided into two different experimental approaches, the first experiments included five study groups (n=5): intrathecal Thi (Thi.it), intraperitoneal (Thi), NAC, DEX, and control. Cell survival was assessed in L5DRG in the 4^th week by histological assessment. In the second study, 40 animals were engaged to assess Bcl-2, Bax, IL-6, and TNF-α expression in L4-L5DRG in the 1^st and 2^nd weeks after sural nerve axotomy under treatment of these agents (n=10).

Results

Ghost cells were observed in morphological assessment of L5DRG sections, and following stereological analysis, the volume and neuronal cell counts significantly were improved in the NAC and Thi.it groups in the 4^th week (P<0.05). Although Bcl-2 expression did not show significant differences, Bax was reduced in the Thi group (P=0.01); and the Bcl-2/Bax ratio increased in the NAC group (1^st week, P<0.01). Furthermore, the IL-6 and TNF-α expression decreased in the Thi and NAC groups, on the 1^st week of treatment (P≤0.05 and P<0.01). However, in the 2^nd week, the IL-6 expression in both Thi and NAC groups (P<0.01), and the TNF-α expression in the DEX group (P=0.05) were significantly decreased.

Conclusion

The findings may classify Thi in the category of peripheral neuroprotective agents, in combination with routine medications. Furthermore, it had strong cell survival effects as it could interfere with the destructive effects of TNF-α by increasing Bax.

Hydro-ethanol extract of Holarrhena floribunda stem bark exhibits anti-anaphylactic and anti-oedematogenic effects in murine models of acute inflammation

Background

Holarrhena floribunda (G.Don) T.Durand & Schinz stem bark has anecdotal use in Ghanaian folk medicine for the management of inflammatory conditions. This study was conducted to investigate the in vivo anti-inflammatory activity of the bark extract using models of acute inflammation in male Sprague Dawley rats, C57BL/6 mice and ICR mice.

Methods

A 70% hydro-ethanol extract of the stem bark (HFE) was evaluated at doses of 5–500 mg/kg bw. Local anaphylaxis was modelled by the pinnal cutaneous anaphylactic test. Systemic anaphylaxis or sepsis were modeled by compound 48/80 or lipopolysaccharide, respectively. Clonidine-induced catalepsy was used to investigate the effect on histamine signaling. Anti-oedematogenic effect was assessed by induction with carrageenan. Effects on mediators of biphasic acute inflammation were studied using histamine and serotonin (early phase) or prostaglandin E2 (late phase).

Results

HFE demonstrated anti-inflammatory and/or anti-oedematogenic activity comparable to standard doses of aspirin and diclofenac (inhibitors of cyclooxygenases-1 and -2), chlorpheniramine (histamine H1-receptor antagonist), dexamethasone (glucocorticoid receptor agonist), granisetron (serotonin receptor antagonist) and sodium cromoglycate (inhibitor of mast cell degranulation). All observed HFE bioactivities increased with dose.

Conclusions

The data provide evidence that the extract of H. floribunda stem bark has anti-anaphylactic and anti-oedematogenic effects; by interfering with signalling or metabolism of histamine, serotonin and prostaglandin E₂ which mediate the progression of inflammation. The anti-inflammatory and antihistaminic activities of HFE may be relevant in the context of the management of COVID-19.

Physiologically Based Pharmacokinetics of Dexamethasone in Rats

Blood and multitissue concentration-time profiles for dexamethasone (DEX), a synthetic corticosteroid, were measured in male rats after subcutaneous bolus and infusion dosing. A physiologically based pharmacokinetics (PBPK) model was applied for 12 measured tissues. Tissue partition coefficients (K _p ) and metabolic clearance were assessed from infusion studies. Blood cell to plasma partitioning (0.664) and plasma free fraction (0.175) for DEX were found to be moderate. DEX was extensively partitioned into liver (K _p = 6.76), whereas the calculated K _p values of most tissues ranged between 0.1 and 1.5. Despite the moderate lipophilicity of DEX (log P = 1.8), adipose exhibited very limited distribution (K _p = 0.17). Presumably due to P-glycoprotein-mediated efflux, DEX concentrations were very low in brain compared with its expected high permeability. Infusion studies yielded K _p values from male and female rats at steady state that were similar. In silico K _p values calculated for different tissues by using GastroPlus software were similar to in vivo values except for adipose and liver. Glucocorticoid receptors are found in diverse tissues, and these PBPK modeling results may help provide exposure profiles driving pharmacodynamic effects of DEX. SIGNIFICANCE STATEMENT: Our physiologically based pharmacokinetics model describes the experimentally determined tissue and plasma dexamethasone (DEX) pharmacokinetics (PK) profiles in rats reasonably well. This model can serve for further investigation of DEX tissue distribution in rats as the PK driving force for PD effects in different tissues. No major sex differences were found for DEX tissue distribution. Knowledge gained in this study may be translatable to higher-order species including humans.

Modeling Combined Anti-Inflammatory Effects of Dexamethasone and Tofacitinib in Arthritic Rats

Tofacitinib (TOF), a Janus kinase (JAK) inhibitor, which was approved in 2012, has been recommended for the treatment of clinically active rheumatoid arthritis (RA). Dexamethasone (DEX), a potent corticosteroid, is also used in RA therapy but with limited usefulness due to dose- and time-dependent adverse effects. This pilot study examines the single and combined effects of DEX and TOF in order to explore the steroid-sparing potential of TOF. Collagen-induced arthritic (CIA) rats were subcutaneously (SC) dosed with vehicle, 1.5 mg/kg TOF, 5 mg/kg TOF, 0.225 mg/kg DEX, or a combination of 1.5 mg/kg TOF and 0.225 mg/kg DEX. Paw sizes were measured as an index of disease and drug efficacy and dynamically depicted using a logistic function for natural paw growth, a turnover model for disease progression, an indirect response model for inhibitory effects of TOF and DEX and a non-competitive interaction model for the combined effect of DEX and TOF. TOF alone exerted only a slight inhibitory effect on RA paw edema compared to DEX, which reduced edema by 40%. In combination, TOF and DEX had additive effects with an interaction factor of 0.76. Using model simulations, a single SC dose of TOF does not have a visible steroid-sparing potential, although BID oral dosing has such potential. The current study suggests an additive effect of TOF and DEX and simulations indicate that further exploration of TOF and DEX administration timing may produce desirable drug efficacy with lower DEX doses.

Lipopolysaccharide (LPS) enhances prostate cancer metastasis potentially through NF-κB activation and recurrent dexamethasone administration fails to suppress it in vivo

BACKGROUND

Previous studies have shown the effect of bacterial lipopolysaccharide (LPS) on enhanced cancer cells' growth and metastasis. However, the effect of LPS on prostate cancer (PCa) cells metastasis has not been investigated in details. This study aimed to investigate the functional role of LPS on PCa cells metastasis and determine the effect of dexamethasone (DEX) on this event.

METHODS

Two different PCa reporter cells lines (DU145-NF-κB-Luc and MAT-LyLu- NF-κB-Luc) were used to assess the direct effect of LPS on NF-κB activation in PCa cells. Plasma collected from LPS-stimulated human and rodent blood were used to check the indirect effect of LPS on NF-κB activation in PCa cells. Trans-well migration assay and two different orthotopic PCa animal models were used to investigate the effect of LPS on DU145 and MAT-LyLu cells migration or metastasis in vitro and in vivo, respectively. In all the studies DEX was used with or without LPS stimulation.

RESULTS

LPS and secretory factors present in plasma collected from LPS-stimulated blood, significantly activated NF-κB in DU145, and MAT-LyLu cells and enhanced their migration in vitro. DEX significantly suppressed LPS-mediated activation of cancer and blood cells and abrogated the direct and indirect pro-migratory effect of LPS on PCa cells. Systemic administration of LPS activated NF-κB in DU145 cells in vivo; however, failed to alter the metastatic properties of these cells. On the other hand, systemic administration of LPS to MAT-LyLu tumor bearing animals significantly enhanced the incidence of metastasis without altering the overall growth of primary tumors. Unexpectedly, though DEX significantly suppressed MAT-LyLu primary tumor weights, it aggravated metastasis of cancer cells in presence and absence of LPS. Moreover, consecutive DEX pre-treatment enhanced experimental peritoneal metastasis of MAT-LyLu cells. At the molecular level, LPS, and/or DEX induced overexpression of immunosuppressive molecules in MAT-LyLu tumors.

CONCLUSIONS

Overall, our study has shown that LPS and/or LPS induced inflammation can increase PCa metastasis and immunosuppressive dose of DEX might further enhance cancer metastasis.

Modeling Sex Differences in Anti-inflammatory Effects of Dexamethasone in Arthritic Rats

PURPOSE

Collagen-induced arthritic (CIA) rats are used commonly for preclinical pharmacologic research into rheumatoid arthritis (RA). Dexamethasone (DEX), a potent corticosteroid (CS), remains an important component in combination therapy for RA. Although sex differences in RA and CS pharmacokinetics/pharmacodynamics (PK/PD) have been documented in humans, there has been no such comprehensive evaluation of sex differences in CIA rats.

METHODS

Paw size measurements were obtained for males and females from four groups of animals: healthy controls, non-drug treated arthritic animals, and both 0.225 and 2.25 mg/kg DEX-treated arthritic animals. A turnover model for disease progression, minimal PBPK model for drug concentrations, and inhibitory indirect response model were applied using population PK/PD modeling.

RESULTS

The clearances of DEX were 43% greater in males, but other PK parameters were similar. The temporal profiles of paw swelling exhibited earlier progression, peak edema times, and disease remission in females. DEX suppressed paw edema well in both males and females with similar capacity (I_max) values (=1.0), but DEX potency was less in females with higher IC₅₀ values (0.101 versus 0.015 ng/mL).

CONCLUSIONS

The pharmacology of DEX was well characterized in CIA rats. This study addresses knowledge gaps about sex differences and can be a guide for more mechanistic assessment of sex, drug, and disease differences in RA.

Time-dependent pharmacokinetics of dexamethasone and its efficacy in human breast cancer xenograft mice: a semi-mechanism-based pharmacokinetic/pharmacodynamic model

Dexamethasone (DEX) is the substrate of CYP3A. However, the activity of CYP3A could be induced by DEX when DEX was persistently administered, resulting in auto-induction and time-dependent pharmacokinetics (pharmacokinetics with time-dependent clearance) of DEX. In this study we investigated the pharmacokinetic profiles of DEX after single or multiple doses in human breast cancer xenograft nude mice and established a semi-mechanism-based pharmacokinetic/pharmacodynamic (PK/PD) model for characterizing the time-dependent PK of DEX as well as its anti-cancer effect. The mice were orally given a single or multiple doses (8 mg/kg) of DEX, and the plasma concentrations of DEX were assessed using LC-MS/MS. Tumor volumes were recorded daily. Based on the experimental data, a two-compartment model with first order absorption and time-dependent clearance was established, and the time-dependence of clearance was modeled by a sigmoid E_max equation. Moreover, a semi-mechanism-based PK/PD model was developed, in which the auto-induction effect of DEX on its metabolizing enzyme CYP3A was integrated and drug potency was described using an E_max equation. The PK/PD model was further used to predict the drug efficacy when the auto-induction effect was or was not considered, which further revealed the necessity of adding the auto-induction effect into the final PK/PD model. This study established a semi-mechanism-based PK/PD model for characterizing the time-dependent pharmacokinetics of DEX and its anti-cancer effect in breast cancer xenograft mice. The model may serve as a reference for DEX dose adjustments or optimization in future preclinical or clinical studies.

Bortezomib treatment induces a higher mortality rate in lupus model mice with a higher disease activity

Background

Bortezomib (Bz) is a proteasome inhibitor that directly targets antibody-producing plasma cells. We recently reported the first randomized control trial that evaluated the effects of Bz in patients with systemic lupus erythematosus (SLE). In that study, we demonstrated that Bz treatment is associated with many adverse reactions in patients with refractory disease. In the present study, we examine the therapeutic and toxic effects of Bz on MRL/MpJ-lpr/lpr (MRL/lpr) mice with severe disease activity.

Methods

Female MRL/lpr mice at 10 and 14 weeks of age were treated with phosphate buffered saline (PBS) (n = 19), Bz (750 μg/kg twice weekly) (n = 27), or cyclophosphamide (Cyc) (1 mg/body, once in 2 weeks) (n = 20). Cellular subsets, serum immunoglobulin, anti-double-stranded DNA (anti-dsDNA) antibody titer, and a pathological index of glomerulonephritis were then analyzed at 22 weeks of age. Survival curves of the 10-week-old and 14-week-old Bz-treated groups were compared. Blood counts, creatinine, liver enzymes, and serum cytokine levels were measured 1 week after Bz treatment. Gene expression profiling of spleens from Bz and Cyc treatment mice were compared with those from control mice.

Results

The anti-dsDNA antibody levels were significantly higher in 14-week-old than in 10-week-old mice, indicating a higher disease activity at 14 weeks. A significant decrease in the number of splenic cells and glomerulonephritis index was observed in Bz-treated and Cyc-treated mice. Bz, but not Cyc, significantly decreased serum immunoglobulin and anti-dsDNA antibody titer levels. Survival curve analysis revealed a significantly higher mortality rate in 14-week-old than in 10-week-old Bz-treated and control groups. Following two injections of Bz, serum IL-6 and TNF-α levels were significantly more elevated in 14-week-old than in 10-week-old mice. Potentially immunogenic molecules, such as heat shock proteins, were characteristically upregulated in spleens of Bz-treated but not Cyc-treated mice.

Conclusions

In spite of its therapeutic effect, Bz treatment had more toxic effects associated with increased proinflammatory cytokine levels in mice with a higher disease activity. Understanding the mechanism of the toxicity and developing preventive strategies against it is important for the safe clinical application of Bz in human SLE.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1397-7) contains supplementary material, which is available to authorized users.

Modeling Combined Immunosuppressive and Anti-inflammatory Effects of Dexamethasone and Naproxen in Rats Predicts the Steroid-Sparing Potential of Naproxen

Dexamethasone (DEX), a widely prescribed corticosteroid, has long been the cornerstone of the treatment of inflammation and immunologic dysfunctions in rheumatoid arthritis. Corticosteroids are frequently used in combination with other antirheumatic agents such as nonsteroidal anti-inflammatory drugs (NSAIDs) and disease-modifying antirheumatic drugs to mitigate disease symptoms and minimize unwanted effects. We explored the steroid dose-sparing potential of the NSAID naproxen (NPX) with in vitro and in vivo studies. The single and joint suppressive effects of DEX and NPX on the in vitro mitogen-induced proliferation of T lymphocytes in blood and their anti-inflammatory actions on paw edema were investigated in female and male Lewis rats with collagen-induced arthritis (CIA). As expected, DEX was far more potent than NPX in these systems. Mathematical models incorporating an interaction term ψ were applied to quantitatively assess the nature and intensity of pharmacodynamic interactions between DEX and NPX. Modest synergistic effects of the two drugs were found in suppressing the mitogenic response of T lymphocytes. A pharmacokinetic/pharmacodynamic/disease progression model integrating dual drug inhibition quantitatively described the pharmacokinetics, time-course of single and joint anti-inflammatory effects (paw edema), and sex differences in CIA rats, and indicated additive effects of DEX and NPX. Further model simulations demonstrated the promising steroid-sparing potential of NPX in CIA rats, with the beneficial effects of the combination therapy more likely in males than females.

Effect of Disease-Related Changes in Plasma Albumin on the Pharmacokinetics of Naproxen in Male and Female Arthritic Rats

Naproxen (NPX) is used in the treatment of rheumatoid arthritis (RA) for alleviation of pain and inflammation. In view of the extensive albumin binding of NPX, this study investigates whether chronic inflammation and sex influence the physiologic albumin concentrations, plasma protein binding, and pharmacokinetics (PK) of NPX. The PK of NPX was evaluated in a rat model of RA [collagen-induced arthritis (CIA) in Lewis rats] and in healthy controls. These PK studies included 1) NPX in female and male CIA rats that received 10, 25, or 50 mg/kg NPX i.p.; and 2) NPX in healthy female and male rats after i.p. dosing of NPX at 50 mg/kg. Plasma albumin concentrations were quantified by enzyme-linked immunosorbent assay, and protein binding was assessed using ultrafiltration. The NPX concentrations in plasma and filtrates were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Plasma concentration-time data of NPX were first assessed by noncompartmental analysis (NCA). Nonlinear PK as indicated by dose-dependent NCA clearances and distribution volumes was observed. A two-compartment model with a first-order absorption process incorporating nonlinear protein binding in plasma and tissues jointly described the PK data of all groups. Saturable albumin binding accounts for the nonlinearity of NPX PK in all rats as well as part of the PK differences in arthritic rats. The CIA rats exhibited reduced albumin concentrations, reduced overall protein binding, and reduced clearances of unbound NPX, consistent with expectations during inflammation. The net effect of chronic inflammation was an elevation of the C_max and area under the plasma concentration-time curve (AUC) of unbound drug.

Model-Informed Development and Registration of a Once-Daily Regimen of Extended-Release Tofacitinib

Extended‐release (XR) formulations enable less frequent dosing vs. conventional (e.g., immediate release (IR)) formulations. Regulatory registration of such formulations typically requires pharmacokinetic (PK) and clinical efficacy data. Here we illustrate a model‐informed, exposure–response (E‐R) approach to translate controlled trial data from one formulation to another without a phase III trial, using a tofacitinib case study. Tofacitinib is an oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis (RA). E‐R analyses were conducted using validated clinical endpoints from phase II dose–response and nonclinical dose fractionation studies of the IR formulation. Consistent with the delay in clinical response dynamics relative to PK, average concentration was established as the relevant PK parameter for tofacitinib efficacy and supported pharmacodynamic similarity. These evaluations, alongside demonstrated equivalence in total systemic exposure between IR and XR formulations, provided the basis for the regulatory approval of tofacitinib XR once daily by the US Food and Drug Administration.

Effects of the stem extracts of Schisandra glaucescens Diels on collagen-induced arthritis in Balb/c mice

ETHNOPHARMACOLOGICAL RELEVANCE

Schisandra glaucescens Diels (SGD) is used in a subclass of traditional Chinese medicine known as "Tujia drugs". It has been long used for the treatment of rheumatoid arthritis (RA), cough with dyspnea, spontaneous sweating, night sweating, chronic diarrhea, and neurasthenia. As a woody liana growing in mountain jungles at the altitudes of 750-1800m, it is mainly distributed in Sichuan and Hubei Provinces of China.

AIM OF THE STUDY

To evaluate the antiarthritic activity of acetate (EA) and n-butanol (Bu) fractions of SGD extract on a collagen-induced arthritis mice model.

MATERIALS AND METHODS

Acute toxicity of EA and Bu fractions of SGD extract was evaluated by gavage on normal mice. Pharmacological investigations were conducted on arthritis male Balb/c mice. The animal model was induced by immunization with type II bovine collagen (CII) on the 1st and the 14th day of the experimental schedule. EA fraction (104, 312, 936mg/kg), Bu fraction (156, 469, 1407mg/kg) of SGD extract was orally administered every two days since the 15th day for 3 weeks. Progression of edema in the paws was measured using a vernier caliper every 3 days since the 10th day. At the end of the experiment, the spleen index and histological changes of the hind knee joints were investigated. Additionally, to explore the possible antirheumatic mechanisms of the EA and Bu fractions, ELISA was carried out to analyze TNF-α, IL-10, IL-6 and IL-1β in the serum.

RESULTS

The half lethal doses of both EA and Bu fractions were much higher than the dose administered in the pharmacological investigations. Oral administration of EA fraction and Bu fraction of SGD extract significantly and does-dependently inhibited type ІІ collagen induced arthritis (CIA) in mice, as indicated by the effects on paws swelling and spleen index. Histopathological examinations demonstrated that SGD effectively protected the bones and cartilages of knee joints from erosion, lesion and deformation. Besides, the serum concentrations of cytokines TNF-α, IL-1β and IL-6 were significantly lower than the ones from the vehicle control group. Respectively, while cytokine IL-10 was remarkably higher compare with the vehicle control group.

CONCLUSIONS

SGD might be a safe and effective candidate for the treatment of RA, and deserves further investigation on the chemical components in both EA and Bu fractions of SGD extract.

Modeling effects of dexamethasone on disease progression of bone mineral density in collagen-induced arthritic rats

A mechanism-based model was developed to characterize the crosstalk between proinflammatory cytokines, bone remodeling biomarkers, and bone mineral density (BMD) in collagen-induced arthritic (CIA) rats. Male Lewis rats were divided into five groups: healthy control, CIA control, CIA receiving single 0.225 mg kg⁻¹ subcutaneous (SC) dexamethasone (DEX), CIA receiving single 2.25 mg kg⁻¹ SC DEX, and CIA receiving chronic 0.225 mg kg⁻¹ SC DEX. The CIA rats underwent collagen induction at day 0 and DEX was injected at day 21 post-induction. Disease activity was monitored throughout the study and rats were sacrificed at different time points for blood and paw collection. Protein concentrations of interleukin (IL)-1β, IL-6, receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), and tartrate-resistant acid phosphatase 5b (TRACP-5b) in paws were measured by enzyme-linked immunosorbent assays (ELISA). Disease progression and DEX pharmacodynamic profiles of IL-1β, IL-6, RANKL, and OPG were fitted simultaneously and parameters were sequentially applied to fit the TRACP-5b and BMD data. The model was built according to the mechanisms reported in the literature and modeling was performed using ADAPT 5 software with naïve pooling. Time profiles of IL-1β and IL-6 protein concentrations correlated with their mRNAs. The RANKL and OPG profiles matched previous findings in CIA rats. DEX inhibited the expressions of IL-1β, IL-6, and RANKL, but did not alter OPG. TRACP-5b was also inhibited by DEX. Model predictions suggested that anti-IL-1β therapy and anti-RANKL therapy would result in similar efficacy for prevention of bone loss among the cytokine antagonists.

Effect of orexin-A (hypocretin-1) on hyperalgesic and cachectic manifestations of experimentally induced rheumatoid arthritis in rats

Orexin-A has been shown to modulate pain sensation and increase appetite. Rheumatoid arthritis (RA) is characterized by joint destruction, deformity, hyperalgesia, and weight reduction. Aim: Evaluate the possible effect of orexin-A on hyperalgesic and cachectic manifestations in an adjuvant-induced arthritis (AIA) rat model. Methods: Forty adult male Wistar rats were distributed among 4 groups; I, normal controls; II, rats with AIA induced by intradermal injection of Mycobacterium butyricum, but with no other treatment; III, AIA rats treated daily with an intravenous injection of orexin-A for 8 days; and IV, AIA rats treated orally with dexamethasone for 8 days. The parameters we assessed were pain-associated behavior, body mass, hind paw volume, serum levels of nerve growth factor (NGF) and neuropeptide Y (NPY). Results: Orexin-A caused a significant reduction in pain sensation and NGF levels, and increased body mass and the levels of NPY, whereas treatment with dexamethasone led to significant reductions in paw swelling and pain sensation. Conclusion: Orexin-A has hypoalgesic properties and increases body mass, whereas dexamethasone has a potent anti-inflammatory effect. Therefore, the combination of orexin-A and dexamethasone should have a greater effect with respect to attenuating the manifestations and complications associated with RA.

Application of population pharmacokinetics for preclinical safety and efficacy studies

From the beginning of the 1980s, population PK has been primarily used in clinical development and only in the last decade has it been convincingly applied in a preclinical setting. Sparse sampling and covariate analyses are key features of preclinical popPK, useful for toxicology and efficacy studies in animals to assemble data obtained from different studies; for describing individual PK and PD; for building mechanistic models; and for performing interspecies scaling-up of disposition and efficacy. Application in disease models, mainly in behavioral and neurological models, allows the quantitative description of PK and PD without frequent blood sampling and recurrent physiological measurements, which are the critical and compromising perturbations of experimental systems. A preclinical population approach to PK and PD, by its versatility and possibility of simulating ‘what if’ scenarios, offers a unique and potent tool in the development of new drugs, in particular biologics.

Hemodynamic flow improves rat hepatocyte morphology, function, and metabolic activity in vitro

In vitro primary hepatocyte systems typically elicit drug induction and toxicity responses at concentrations much higher than corresponding in vivo or clinical plasma C(max) levels, contributing to poor in vitro-in vivo correlations. This may be partly due to the absence of physiological parameters that maintain metabolic phenotype in vivo. We hypothesized that restoring hemodynamics and media transport would improve hepatocyte architecture and metabolic function in vitro compared with nonflow cultures. Rat hepatocytes were cultured for 2 wk either in nonflow collagen gel sandwiches with 48-h media changes or under controlled hemodynamics mimicking sinusoidal circulation within a perfused Transwell device. Phenotypic, functional, and metabolic parameters were assessed at multiple times. Hepatocytes in the devices exhibited polarized morphology, retention of differentiation markers [E-cadherin and hepatocyte nuclear factor-4α (HNF-4α)], the canalicular transporter [multidrug-resistant protein-2 (Mrp-2)], and significantly higher levels of liver function compared with nonflow cultures over 2 wk (albumin ~4-fold and urea ~5-fold). Gene expression of cytochrome P450 (CYP) enzymes was significantly higher (fold increase over nonflow: CYP1A1: 53.5 ± 10.3; CYP1A2: 64.0 ± 15.1; CYP2B1: 15.2 ± 2.9; CYP2B2: 2.7 ± 0.8; CYP3A2: 4.0 ± 1.4) and translated to significantly higher basal enzyme activity (device vs. nonflow: CYP1A: 6.26 ± 2.41 vs. 0.42 ± 0.015; CYP1B: 3.47 ± 1.66 vs. 0.4 ± 0.09; CYP3A: 11.65 ± 4.70 vs. 2.43 ± 0.56) while retaining inducibility by 3-methylcholanthrene and dexamethasone (fold increase over DMSO: CYP1A = 27.33 and CYP3A = 4.94). These responses were observed at concentrations closer to plasma levels documented in vivo in rats. The retention of in vivo-like hepatocyte phenotype and metabolic function coupled with drug response at more physiological concentrations emphasizes the importance of restoring in vivo physiological transport parameters in vitro.

Prediction of hepatic plasma clearance in vivo from gel-entrapped rat and human hepatocytes

This paper aimed to evaluate the applicability of gel-entrapped rat and human hepatocytes in the prediction of hepatic plasma clearance (CLh,plasma) in vivo. The in vitro intrinsic clearances (CLint,in vitro) for the selected compounds were determined from the substrate disappearance rate, and further used to predict CLh,plasma using 3 classical mathematical models (well-stirred, parallel-tube, and dispersion) and disregarding drug binding. As a result, the predicted values from gel-entrapped rat hepatocytes were mostly within 2 SE of the literature data with a high correlation coefficient (R2) of 0.88–0.91. The predicted data with human hepatocytes also fitted well with the clinical data, indicating a high accuracy in prediction of in-vivo clearance. With respect to the mathematical model for predicting CLh,plasma, the parallel-tube and dispersion models produced a better prediction than the well-stirred model, and we suggest using the parallel-tube model because it is less complex mathematically. In conclusion, gel-entrapped hepatocytes predicted the drug clearance well and seemed to be a useful tool in the process of drug discovery.

A mechanism-based pharmacokinetic/pharmacodynamic model for CYP3A1/2 induction by dexamethasone in rats

AIM

To develop a pharmacokinetic/pharmacodynamic (PK/PD) model describing the receptor/gene-mediated induction of CYP3A1/2 by dexamethasone (DEX) in rats.

METHODS

A group of male Sprague-Dawley rats receiving DEX (100 mg/kg, ip) were sacrificed at various time points up to 60 h post-treatment. Their blood sample and liver were collected. The plasma concentration of DEX was determined with a reverse phase HPLC method. CYP3A1/2 mRNA, protein levels and enzyme activity were measured using RT-PCR, ELISA and the testosterone substrate assay, respectively. Data analyses were performed using a first-order conditional estimate (FOCE) with INTERACTION method in NONMEM version 7.1.2.

RESULTS

A two-compartment model with zero-order absorption was applied to describe the pharmacokinetic characteristics of DEX. Systemic clearance, the apparent volume of distribution and the duration of zero-order absorption were calculated to be 172.7 mL·kg(-1)·h(-1), 657.4 mL/kg and 10.47 h, respectively. An indirect response model with a series of transit compartments was developed to describe the induction of CYP3A1/2 via PXR transactivation by DEX. The maximum induction of CYP3A1 and CYP3A2 mRNA levels was achieved, showing nearly 21.29- and 8.67-fold increases relative to the basal levels, respectively. The CYP3A1 and CYP3A2 protein levels were increased by 8.02-fold and 2.49-fold, respectively. The total enzyme activities of CYP3A1/2 were shown to increase by up to 2.79-fold, with a lag time of 40 h from the Tmax of the DEX plasma concentration. The final PK/PD model was able to recapitulate the delayed induction of CYP3A1/2 mRNA, protein and enzyme activity by DEX.

CONCLUSION

A mechanism-based PK/PD model was developed to characterize the complex concentration-induction response relationship between DEX and CYP3A1/2 and to resolve the drug- and system-specific PK/PD parameters for the course of induction.