Correlation between in vitro and in vivo concentration-effect relationships of naproxen in rats and healthy volunteers

Discovery of a CK2α'-Biased ATP-Competitive Inhibitor from a High-Throughput Screen of an Allosteric-Inhibitor-Like Compound Library

Protein kinase CK2 is a holoenzyme composed of two regulatory subunits (CK2β) and two catalytic subunits (CK2α and CK2α'). CK2 controls several cellular processes, including proliferation, inflammation, and cell death. However, CK2α and CK2α' possess different expression patterns and substrates and therefore impact each of these processes differently. Elevated CK2α participates in the development of cancer, while increased CK2α' has been associated with neurodegeneration, especially Huntington's disease (HD). HD is a fatal disease for which no effective therapies are available. Genetic deletion of CK2α' in HD mouse models has ameliorated neurodegeneration. Therefore, pharmacological inhibition of CK2α' presents a promising therapeutic strategy for treating HD. However, current CK2 inhibitors are unable to discriminate between CK2α and CK2α' due to their high structural homology, especially in the targeted ATP-binding site. Using computational analyses, we found a potential type IV ("D" pocket) allosteric site that contained different residues between CK2α and CK2α' and was distal from the ATP-binding pocket featured in both kinases. We decided to look for allosteric modulators that might interact in a biased fashion with the type IV pocket on both CK2α and CK2α'. We screened a commercial library containing ∼29,000 allosteric-kinase-inhibitor-like compounds using a CK2α' activity-dependent ADP-Glo Kinase assay. Obtained hits were counter-screened against CK2α using the ADP-Glo Kinase assay, revealing two CK2α'-biased compounds. These two compounds might serve as the basis for further medicinal chemistry optimization for the potential treatment of HD.

NSAIDs Naproxen, Ibuprofen, Salicylate, and Aspirin Inhibit TRPM7 Channels by Cytosolic Acidification

Non-steroidal anti-inflammatory drugs (NSAIDs) are used for relieving pain and inflammation accompanying numerous disease states. The primary therapeutic mechanism of these widely used drugs is the inhibition of cyclooxygenase 1 and 2 (COX1, 2) enzymes that catalyze the conversion of arachidonic acid into prostaglandins. At higher doses, NSAIDs are used for prevention of certain types of cancer and as experimental treatments for Alzheimer’s disease. In the immune system, various NSAIDs have been reported to influence neutrophil function and lymphocyte proliferation, and affect ion channels and cellular calcium homeostasis. Transient receptor potential melastatin 7 (TRPM7) cation channels are highly expressed in T lymphocytes and are inhibited by Mg²⁺, acidic pH, and polyamines. Here, we report a novel effect of naproxen, ibuprofen, salicylate, and acetylsalicylate on TRPM7. At concentrations of 3–30mM, they reversibly inhibited TRPM7 channel currents. By measuring intracellular pH with the ratiometric indicator BCECF, we found that at 300μM to 30mM, these NSAIDs reversibly acidified the cytoplasm in a concentration-dependent manner, and propose that TRPM7 channel inhibition is a consequence of cytosolic acidification, rather than direct. NSAID inhibition of TRPM7 channels was slow, voltage-independent, and displayed use-dependence, increasing in potency upon repeated drug applications. The extent of channel inhibition by salicylate strongly depended on cellular PI(4,5)P₂ levels, as revealed when this phospholipid was depleted with voltage-sensitive lipid phosphatase (VSP). Salicylate inhibited heterologously expressed wildtype TRPM7 channels but not the S1107R variant, which is insensitive to cytosolic pH, Mg²⁺, and PI(4,5)P₂ depletion. NSAID-induced acidification was also observed in Schneider 2 cells from Drosophila, an organism that lacks orthologous COX genes, suggesting that this effect is unrelated to COX enzyme activity. A 24-h exposure to 300μM–10mM naproxen resulted in a concentration-dependent reduction in cell viability. In addition to TRPM7, the described NSAID effect would be expected to apply to other ion channels and transporters sensitive to intracellular pH.

Angiogenic Effect of Pravastatin Alone and with Sera from Healthy and Complicated Pregnancies Studied by in vitro Vasculogenesis/Angiogenesis Assay

OBJECTIVE

To determine the direct effect of pravastatin on angiogenesis and to study the interaction between pravastatin and maternal sera from women with early- or late-onset pre-eclampsia (PE), intrauterine growth restriction, or healthy pregnancy.

METHODS

We collected 5 maternal serum samples from each group. The effect of pravastatin on angiogenesis was assessed with and without maternal sera by quantifying tubule formation in a human-based in vitro assay. Pravastatin was added at 20, 1,000, and 8,000 ng/mL concentrations. Concentrations of angiogenic and inflammatory biomarkers in serum and in test medium after supplementation of serum alone and with pravastatin (1,000 ng/mL) were measured.

RESULTS

Therapeutic concentration of pravastatin (20 ng/mL) did not have significant direct effect on angiogenesis, but the highest concentrations inhibited angiogenesis. Pravastatin did not change the levels of biomarkers in the test media. There were no changes in angiogenesis when therapeutic dose of pravastatin was added with maternal sera, but there was a trend to wide individual variation towards enhanced angiogenesis, particularly in the early-onset PE group.

CONCLUSIONS

At therapeutic concentration, pravastatin alone or with maternal sera has no significant effect on angiogenesis, but at high concentrations the effect seems to be anti-angiogenic estimated by in vitro assay.

Simvastatin Inhibits the Malignant Behaviors of Gastric Cancer Cells by Simultaneously Suppressing YAP and β-Catenin Signaling

Background

Statins, which are used to lower blood cholesterol levels by inhibiting HMG-CoA reductase, have shown anticancer effects in many cancer cells. However, the role of statins in gastric cancer remains unclear. This study aims to investigate whether the statins could antagonize progression of gastric cancer cells and tried to find the molecule mechanism.

Methods

Effects of simvastatin on the morphology, proliferation, migration, apoptosis, and invasion of gastric cancer cells were detected and compared. Western blotting, cell viability assay, fluorescence, and transfection were employed to study the molecule mechanism of the effects and the interaction between YAP and β-catenin signaling.

Results

Simvastatin could inhibit proliferation, migration and invasion, and promote the apoptosis in gastric cancer cells. Mechanistic studies showed that simvastatin treatment could inhibit the expression of β-catenin and the activity of YAP and the downstream targets of YAP and β-catenin in gastric cancer cells. Moreover, we found that YAP and β-catenin could form a positive feedback loop in gastric cancer cells. Further investigation revealed that simvastatin mainly acted through by inhibiting the activity of RhoA to inhibit YAP and β-catenin, and the geranylgeranyl pyrophosphate pathway mediated this regulation.

Conclusion

Statins represent a promising therapeutic option for gastric cancer by simultaneously targeting YAP and β-catenin signaling.

Ondansetron blocks wild-type and p.F503L variant small-conductance Ca2+-activated K+ channels

Apamin-sensitive small-conductance Ca2+-activated K+ (SK) current ( IKAS) is encoded by Ca2+-activated K+ channel subfamily N ( KCNN) genes. IKAS importantly contributes to cardiac repolarization in conditions associated with reduced repolarization reserve. To test the hypothesis that IKAS inhibition contributes to drug-induced long QT syndrome (diLQTS), we screened for KCNN variants among patients with diLQTS, determined the properties of heterologously expressed wild-type (WT) and variant KCNN channels, and determined if the 5-HT3 receptor antagonist ondansetron blocks IKAS. We searched 2,306,335 records in the Indiana Network for Patient Care and found 11 patients with diLQTS who had DNA available in the Indiana Biobank. DNA sequencing discovered a heterozygous KCNN2 variant (p.F503L) in a 52-yr-old woman presenting with corrected QT interval prolongation at baseline (473 ms) and further corrected QT interval lengthening (601 ms) after oral administration of ondansetron. That patient was also heterozygous for the p.S38G and p.P2835S variants of the QT-controlling genes KCNE1 and ankyrin 2, respectively. Patch-clamp experiments revealed that the p.F503L KCNN2 variant heterologously expressed in human embryonic kidney (HEK)-293 cells augmented Ca2+ sensitivity, increasing IKAS density. The fraction of total F503L-KCNN2 protein retained in the membrane was higher than that of WT KCNN2 protein. Ondansetron at nanomolar concentrations inhibited WT and p.F503L SK2 channels expressed in HEK-293 cells as well as native SK channels in ventricular cardiomyocytes. Ondansetron-induced IKAS inhibition was also demonstrated in Langendorff-perfused murine hearts. In conclusion, the heterozygous p.F503L KCNN2 variant increases Ca2+ sensitivity and IKAS density in transfected HEK-293 cells. Ondansetron at therapeutic (i.e., nanomolar) concentrations is a potent IKAS blocker. NEW & NOTEWORTHY We showed that ondansetron, a 5-HT3 receptor antagonist, blocks small-conductance Ca2+-activated K+ (SK) current. Ondansetron may be useful in controlling arrhythmias in which increased SK current is a likely contributor. However, its SK-blocking effects may also facilitate the development of drug-induced long QT syndrome.

Involvement of prolactin in the meloxicam-dependent inflammatory response of the gonadotropic axis to prolonged lipopolysaccharide treatment in anoestrous ewes

An immune challenge can affect the reproductive process in females. Peripheral administration of bacterial endotoxin (lipopolysaccharide; LPS) decreases LH secretion and disrupts ovarian cyclicity. The aim of the present study was to determine the effects of a cyclo-oxygenase (COX)-2 inhibitor (meloxicam) on gonadotropin-releasing hormone (GnRH) and LH secretion in anoestrous ewes during systemic inflammation induced by LPS. LPS (400ngkg^-1 per day) suppressed LH release. In three individuals, meloxicam (500μgkg^-1, i.v.) abolished LPS-induced LH suppression. In another three ewes LH was ineffective. Similar changes were observed in hypothalamic GnRH expression. The effect of meloxicam depended on the circulating level of prolactin: meloxicam abolished inflammatory-dependent suppression of GnRH and LH secretion when plasma prolactin levels were similar to those in untreated animals, but was ineffective in those with elevated levels of prolactin. We conclude that COX-2 inhibitors minimise the negative effect of inflammation on the reproductive system but that this effect may be antagonised by prolactin.

Overexpressing cell systems are a competitive option to primary adipocytes when predicting in vivo potency of dual GPR81/GPR109A agonists

Mathematical models predicting in vivo pharmacodynamic effects from in vitro data can accelerate drug discovery, and reduce costs and animal use. However, data integration and modeling is non-trivial when more than one drug-target receptor is involved in the biological response. We modeled the inhibition of non-esterified fatty acid release by dual G-protein-coupled receptor 81/109A (GPR81/GPR109A) agonists in vivo in the rat, to estimate the in vivo EC₅₀ values for 12 different compounds. We subsequently predicted those potency estimates using EC₅₀ values obtained from concentration-response data in isolated primary adipocytes and cell systems overexpressing GPR81 or GPR109A in vitro. A simple linear regression model based on data from primary adipocytes predicted the in vivo EC₅₀ better than simple linear regression models based on in vitro data from either of the cell systems. Three models combining the data from the overexpressing cell systems were also evaluated: two piecewise linear models defining logical OR- and AND-circuits, and a multivariate linear regression model. All three models performed better than the simple linear regression model based on data from primary adipocytes. The OR-model was favored since it is likely that activation of either GPR81 or GPR109A is sufficient to deactivate the cAMP pathway, and thereby inhibit non-esterified fatty acid release. The OR-model was also able to predict the in vivo selectivity between the two receptors. Finally, the OR-model was used to predict the in vivo potency of 1651 new compounds. This work suggests that data from the overexpressing cell systems are sufficient to predict in vivo potency of GPR81/GPR109A agonists, an approach contributing to faster and leaner drug discovery.

High-throughput microarray for antimicrobial susceptibility testing

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Developed a high-throughput microarray for anti-microbial susceptibility testing (AST).

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Demonstrated that the feasibility of the AST against clinical isolates of MRSA.

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Platform is a low sample volume, rapid, high-throughput alternative to traditional assays.

We describe the development of a novel, high-throughput, nano-scale microarray platform for antimicrobial susceptibility testing (AST). The platform allows to process 480 samples at 50 nL volume on a single chip, analyze by fluorescence read-out with an easy dunk-and-rinse step, and the ability to process multiple samples and chips simultaneously. We demonstrate the applicability of this chip for culturing community acquired methicillin resistant Staphylococcus aureus (CA-MRSA), and perform AST against clinical isolates of CA-MRSA. The chip platform holds promise for an impact in microbial biotechnology as an attractive high-throughput, lower sample volume and quicker alternative to conventional AST such as the traditional broth microdilution or the newer automated systems.

Toxicity of nanomaterials found in human environment

The US National Nanotechnology Initiative (NNI) defines nanotechnology as “the understanding and control of matter at dimensions between approximately 1 and 100 nm, where unique phenomena enable novel applications.” Recent scientific reports available in the literature clearly demonstrate the potential benefits of nanotechnology in consumer and industrial products. More and more nanomaterials are expected to be used in consumer products. This is expected to lead to increased human exposure to nanomaterials in their daily lives. Therefore, the effect of nanomaterials present in human environment is an area of increasing scientific interest. The information presented in this review is obtained from the current literature. It indicates that nanomaterials found in human environment may have potential for toxicological effects. However, the current literature on toxicological effects of nanomaterials is diverse. The current data are presented from studies without harmonization. These studies have used different in vitro and in vivo test models, different sources of test nanomaterials, different methods for nanomaterial characterization, and different experimental conditions. Therefore, these data are hard to interpret. More research on nanomaterial characterization, biological interaction, toxicity, and health effects is needed. The test methods need to be validated. Positive and negative controls for nanotoxicity need to be identified. Toxicity data harmonization needs to be done. Therefore, general information is not currently available for risk evaluation of certain nanomaterials that might be present in consumer products or that may enter into the market in future. Standardized and validated methods are necessary for toxicity assessment of nanomaterials. Therefore, in the absence of standardized validated methods any specific regulatory testing requirements for nanomaterials are currently premature. We conclude that the benefits of nanomaterials found currently in human environment are many, but their overall adverse effects on human health are limited.

Development, Internal and External Validation of Naproxen Sodium Sustained Release Formulation: an Level A In Vitro-In Vivo Correlation

Objectives

The aim of the present study was to develop and validate an in vitro-in vivo correlation (IVIVC) for naproxen sodium-sustained release tablets and to compare their plasma concentrations over time with the immediate-release tablets.

Materials and Methods

In vitro release rate data were obtained for each tablet by using the USP Apparatus II, paddle stirrer at 50 rpm in pH 7.4 phosphate buffer. A four-way crossover study was conducted in 6 healthy subjects by administering naproxen sodium sustained release 375 mg and 500 mg of immediate release tablets. Series of blood samples were collected over 24 hours and estimated by using the validated liquid chromatography tandem-mass spectrometry method.

Results

The similarity factor was calculated and it was found that values between, 50 and 100 indicates similarity of the profiles. Assessment of predicted and observed bioavailability was performed and prediction errors (PE) % calculated, as per the Food Drug Administration guidelines, the average absolute PE% of C_max and AUC of individual formulation was found below 15% for establishment of IVIVC, based on internal prediction strongly suggesting that the naproxen sodium IVIVC models are valid. During external validation the predicted curve for the naproxen sodium sustained-release tablets was found to be identical to immediate release tablets and considered as valid.

Conclusion

IVIVC can serve as a surrogate for in vivo bioavailability study and supports biowaivers, supports and validates the dissolution methods and specification settings and assists in quality control during scale-up and post-approval changes. It may be used to predict the variation in site change, process changes and to predict the absorption performance of naproxen sodium products with different release rates.

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.

Modeling Sex Differences in Pharmacokinetics, Pharmacodynamics, and Disease Progression Effects of Naproxen in Rats with Collagen-Induced Arthritis

Naproxen (NPX) is a frequently used nonsteroidal anti-inflammatory drug for rheumatoid arthritis (RA). Lack of quantitative information about the drug exposure-response relationship has resulted in empirical dosage regimens for use of NPX in RA. Few studies to date have included sex as a factor, although RA predominates in women. A pharmacokinetic, pharmacodynamic, and disease progression model described the anti-inflammatory effects of NPX in collagen-induced arthritic (CIA) male and female rats. Three groups of rats were included for each sex: healthy animals, CIA controls, and CIA rats given a single 50-mg/kg dose of NPX intraperitoneally. Paw volumes of healthy rats indicated natural growth, and disease status was measured by paw edema. An innovative minimal physiologically based pharmacokinetic (mPBPK) model incorporating nonlinear albumin binding of NPX in both plasma and interstitial fluid (ISF) was applied. Arthritic rats exhibited lower plasma and ISF albumin concentrations and reduced clearances of unbound drug to explain pharmacokinetic profiles. The unbound ISF NPX concentrations predicted by the mPBPK model were used as the driving force for pharmacological effects of NPX. A logistic growth function accounting for natural paw growth and an indirect response model for paw edema and drug effects (inhibition of k_in) was applied. Female rats showed a higher incidence of CIA, earlier disease onset, and more severe symptoms. NPX had stronger effects in males, owing to higher unbound ISF NPX concentrations and lower IC₅₀ values. The model described the pharmacokinetics, unbound NPX in ISF, time course of anti-inflammatory effects, and sex differences in CIA rats.

Optimization of human dose prediction by using quantitative and translational pharmacology in drug discovery

In this perspective article, we explain how quantitative and translational pharmacology, when well-implemented, is believed to lead to improved clinical candidates and drug targets that are differentiated from current treatment options. Quantitative and translational pharmacology aims to build and continuously improve the quantitative relationship between drug exposure, target engagement, efficacy, safety and its interspecies relationship at every phase of drug discovery. Drug hunters should consider and apply these concepts to develop compounds with a higher probability of interrogating the clinical biological hypothesis. We offer different approaches to set an initial effective concentration or pharmacokinetic-pharmacodynamic target in man and to predict human pharmacokinetics that determine together the predicted human dose and dose schedule. All concepts are illustrated with ample literature examples.

Novel Activities of Select NSAID R-Enantiomers against Rac1 and Cdc42 GTPases

Rho family GTPases (including Rac, Rho and Cdc42) collectively control cell proliferation, adhesion and migration and are of interest as functional therapeutic targets in numerous epithelial cancers. Based on high throughput screening of the Prestwick Chemical Library^® and cheminformatics we identified the R-enantiomers of two approved drugs (naproxen and ketorolac) as inhibitors of Rac1 and Cdc42. The corresponding S-enantiomers are considered the active component in racemic drug formulations, acting as non-steroidal anti-inflammatory drugs (NSAIDs) with selective activity against cyclooxygenases. Here, we show that the S-enantiomers of naproxen and ketorolac are inactive against the GTPases. Additionally, more than twenty other NSAIDs lacked inhibitory action against the GTPases, establishing the selectivity of the two identified NSAIDs. R-naproxen was first identified as a lead compound and tested in parallel with its S-enantiomer and the non-chiral 6-methoxy-naphthalene acetic acid (active metabolite of nabumetone, another NSAID) as a structural series. Cheminformatics-based substructure analyses—using the rotationally constrained carboxylate in R-naproxen—led to identification of racemic [R/S] ketorolac as a suitable FDA-approved candidate. Cell based measurement of GTPase activity (in animal and human cell lines) demonstrated that the R-enantiomers specifically inhibit epidermal growth factor stimulated Rac1 and Cdc42 activation. The GTPase inhibitory effects of the R-enantiomers in cells largely mimic those of established Rac1 (NSC23766) and Cdc42 (CID2950007/ML141) specific inhibitors. Docking predicts that rotational constraints position the carboxylate moieties of the R-enantiomers to preferentially coordinate the magnesium ion, thereby destabilizing nucleotide binding to Rac1 and Cdc42. The S-enantiomers can be docked but are less favorably positioned in proximity to the magnesium. R-naproxen and R-ketorolac have potential for rapid translation and efficacy in the treatment of several epithelial cancer types on account of established human toxicity profiles and novel activities against Rho-family GTPases.

Model-based prediction of the acute and long-term safety profile of naproxen in rats

BACKGROUND AND PURPOSE

Despite the increasing importance of biomarkers as predictors of drug effects, toxicology protocols continue to rely on the experimental evidence of adverse events (AEs) as a basis for establishing the link between indicators of safety and drug exposure. Furthermore, biomarkers may facilitate the translation of findings from animals to humans. Combined with a model-based approach, biomarker data have the potential to predict long-term effects arising from prolonged drug exposure. Here, we used naproxen as a paradigm to explore the feasibility of a biomarker-guided approach for the prediction of long-term AEs in humans.

EXPERIMENTAL APPROACH

An experimental toxicology protocol was set up for evaluating the effects of naproxen in rats, in which four active doses were tested (7.5, 15, 40 and 80 mg·kg(-1) ). In addition to AE monitoring and histology, a few blood samples were also collected for the assessment of drug exposure, TXB2 and PGE2 levels. Non-linear mixed effects modelling was used to analyse the data and identify covariate factors on the incidence and severity of AEs.

KEY RESULTS

Modelling results showed that besides drug exposure, maximum PGE2 inhibition and treatment duration were also predictors of gastrointestinal ulceration. Although PGE2 levels were clearly linked to the incidence rates, it appeared that ulceration severity is better predicted by measures of drug exposure.

CONCLUSIONS AND IMPLICATIONS

These results show that the use of a model-based approach provides the opportunity to integrate pharmacokinetics, pharmacodynamics and toxicity data, enabling optimization of the design, analysis and interpretation of toxicology experiments.

The impact of composite AUC estimates on the prediction of systemic exposure in toxicology experiments

Current toxicity protocols relate measures of systemic exposure (i.e. AUC, C_max) as obtained by non-compartmental analysis to observed toxicity. A complicating factor in this practice is the potential bias in the estimates defining safe drug exposure. Moreover, it prevents the assessment of variability. The objective of the current investigation was therefore (a) to demonstrate the feasibility of applying nonlinear mixed effects modelling for the evaluation of toxicokinetics and (b) to assess the bias and accuracy in summary measures of systemic exposure for each method. Here, simulation scenarios were evaluated, which mimic toxicology protocols in rodents. To ensure differences in pharmacokinetic properties are accounted for, hypothetical drugs with varying disposition properties were considered. Data analysis was performed using non-compartmental methods and nonlinear mixed effects modelling. Exposure levels were expressed as area under the concentration versus time curve (AUC), peak concentrations (C_max) and time above a predefined threshold (TAT). Results were then compared with the reference values to assess the bias and precision of parameter estimates. Higher accuracy and precision were observed for model-based estimates (i.e. AUC, C_max and TAT), irrespective of group or treatment duration, as compared with non-compartmental analysis. Despite the focus of guidelines on establishing safety thresholds for the evaluation of new molecules in humans, current methods neglect uncertainty, lack of precision and bias in parameter estimates. The use of nonlinear mixed effects modelling for the analysis of toxicokinetics provides insight into variability and should be considered for predicting safe exposure in humans.

Modulation of the cAMP response by Gαi and Gβγ: a computational study of G protein signaling in immune cells

Cyclic AMP is important for the resolution of inflammation, as it promotes anti-inflammatory signaling in several immune cell lines. In this paper, we present an immune cell specific model of the cAMP signaling cascade, paying close attention to the specific isoforms of adenylyl cyclase (AC) and phosphodiesterase that control cAMP production and degradation, respectively, in these cells. The model describes the role that G protein subunits, including Gαs, Gαi, and Gβγ, have in regulating cAMP production. Previously, Gαi activation has been shown to increase the level of cAMP in certain immune cell types. This increase in cAMP is thought to be mediated by βγ subunits which are released upon Gα activation and can directly stimulate specific isoforms of AC. We conduct numerical experiments in order to explore the mechanisms through which Gαi activation can increase cAMP production. An important conclusion of our analysis is that the relative abundance of different G protein subunits is an essential determinant of the cAMP profile in immune cells. In particular, our model predicts that limited availability of βγ subunits may both (i) enable immune cells to link inflammatory Gαi signaling to anti-inflammatory cAMP production thereby creating a balanced immune response to stimulation with low concentrations of PGE2, and (ii) prohibit robust anti-inflammatory cAMP signaling in response to stimulation with high concentrations of PGE2.

Model-based analysis of thromboxane B₂ and prostaglandin E₂ as biomarkers in the safety evaluation of naproxen

The assessment of safety in traditional toxicology protocols relies on evidence arising from observed adverse events (AEs) in animals and on establishing their correlation with different measures of drug exposure (e.g., Cmax and AUC). Such correlations, however, ignore the role of biomarkers, which can provide further insight into the underlying pharmacological mechanisms. Here we use naproxen as a paradigm drug to explore the feasibility of a biomarker-guided approach for the prediction of AEs in humans. A standard toxicology protocol was set up for the evaluation of effects of naproxen in rat, in which four doses were tested (7.5, 15, 40 and 80 mg/kg). In addition to sparse blood sampling for the assessment of exposure, thromboxane B₂ and prostaglandin E₂ were also collected in satellite groups. Nonlinear mixed effects modelling was used to evaluate the predictive performance of the approach. A one-compartmental model with first order absorption was found to best describe the pharmacokinetics of naproxen. A nonlinear relationship between dose and bioavailability was observed which leads to a less than proportional increase in naproxen concentrations with increasing doses. The pharmacodynamics of TXB₂ and PGE₂ was described by direct inhibition models with maximum pharmacological effects achieved at doses >7.5 mg/kg. The predicted PKPD relationship in humans was within 10-fold of the values previously published. Moreover, our results indicate that biomarkers can be used to assess interspecies differences in PKPD and extrapolated data from animals to humans. Biomarker sampling should be used systematically in general toxicity studies.

In vitro-in vivo correlation for low-clearance compounds using hepatocyte relay method

In vitro-in vivo correlation (IVIVC) of intrinsic clearance in preclinical species of rat and dog was established using the hepatocyte relay method to support high-confidence prediction of human pharmacokinetics for low-clearance compounds. Good IVIVC of intrinsic clearance was observed for most of the compounds, with predicted values within 2-fold of the observed values. The exceptions involved transporter-mediated uptake clearance or metabolizing enzymes with extensive extrahepatic contribution. This is the first assay available to address low clearance challenges in preclinical species for IVIVC in drug discovery. It extends the utility of the hepatocyte relay method in addressing low clearance issues.

Pharmacokinetic-pharmacodynamic modeling of diclofenac in normal and Freund's complete adjuvant-induced arthritic rats

AIM

To characterize pharmacokinetic-pharmacodynamic modeling of diclofenac in Freund's complete adjuvant (FCA)-induced arthritic rats using prostaglandin E(2) (PGE(2)) as a biomarker.

METHODS

The pharmacokinetics of diclofenac was investigated using 20-day-old arthritic rats. PGE(2) level in the rats was measured using an enzyme immunoassay. A pharmacokinetic-pharmacodynamic (PK-PD) model was developed to illustrate the relationship between the plasma concentration of diclofenac and the inhibition of PGE(2) production. The inhibition of diclofenac on lipopolysaccharide (LPS)-induced PGE(2) production in blood cells was investigated in vitro.

RESULTS

Similar pharmacokinetic behavior of diclofenac was found both in normal and FCA-induced arthritic rats. Diclofenac significantly decreased the plasma levels of PGE(2) in both normal and arthritic rats. The inhibitory effect on PGE(2) levels in the plasma was in proportion to the plasma concentration of diclofenac. No delay in the onset of inhibition was observed, suggesting that the effect compartment was located in the central compartment. An inhibitory effect sigmoid I(max) model was selected to characterize the relationship between the plasma concentration of diclofenac and the inhibition of PGE(2) production in vivo. The I(max) model was also used to illustrate the inhibition of diclofenac on LPS-induced PGE(2) production in blood cells in vitro.

CONCLUSION

Arthritis induced by FCA does not alter the pharmacokinetic behaviors of diclofenac in rats, but the pharmacodynamics of diclofenac is slightly affected. A PK-PD model characterizing an inhibitory effect sigmoid I(max) can be used to fit the relationship between the plasma PGE(2) and diclofenac levels in both normal rats and FCA-induced arthritic rats.

Randomized trial of sumatriptan and naproxen sodium combination in adolescent migraine

BACKGROUND

Treatment of adolescent migraine remains a significant unmet medical need. We compared the efficacy and safety of 3 doses of sumatriptan and naproxen sodium (suma/nap) combination tablets to placebo in the acute treatment of adolescent migraine.

METHODS

This randomized, parallel group study in 12 to 17 year olds required 2 to 8 migraines per month (typically lasting >3 hours untreated) for ≥ 6 months. Subjects entered a 12-week run-in phase, treating 1 moderate-to-severe migraine (attack 1) with single-blind placebo. Subjects reporting headache pain 2 hours after dosing were randomly assigned into a 12-week double-blind phase, treating 1 moderate-to-severe migraine (attack 2) with placebo (n = 145), suma/nap 10/60 mg (n = 96), 30/180 mg (n = 97), or 85/500 mg (n = 152). The primary end point was the percentage of subjects pain-free at 2 hours.

RESULTS

The attack 2 adjusted (age; baseline pain severity) 2-hour pain-free rates were higher with suma/nap 10/60 mg (29%; adjusted P = .003), 30/180 mg (27%; adjusted P = .003), and 85/500 mg (24%; adjusted P = .003) versus placebo (10%). Posthoc primary end-point analyses did not demonstrate differences among the 3 doses or an age-by-treatment interaction. Statistically significant differences were found for 85/500 mg versus placebo for sustained pain-free 2 to 24 hours (23% vs 9%; adjusted P = .008), 2-hour photophobia-free (59% vs 41%; adjusted P = .008), and 2-hour phonophobia-free (60% vs 42%; adjusted P = .008). Analyses of other pain, associated symptoms, rescue medication use, and health outcome end points supported higher efficacy for active doses versus placebo. All active doses were well tolerated.

CONCLUSIONS

All doses of suma/nap were well tolerated, providing similarly effective acute treatment of adolescent migraine pain and associated symptoms, as compared with placebo.

Pharmacokinetic-pharmacodynamic modeling of the inhibitory effects of naproxen on the time-courses of inflammatory pain, fever, and the ex vivo synthesis of TXB2 and PGE2 in rats

PURPOSE

To quantify and compare the time-course and potency of the analgesic and antipyretic effects of naproxen in conjunction with the inhibition of PGE(2) and TXB(2).

METHODS

Analgesia was investigated in a rat model with carrageenan-induced arthritis using a gait analysis method. Antipyretics were studied in a yeast-induced fever model using telemetrically recorded body temperature. Inhibition of TXB(2) and PGE(2) synthesis was determined ex vivo. Pharmacokinetic profiles were obtained in satellite animals. Population PKPD modeling was used to analyze the data.

RESULTS

The IC(50) values (95% CI) of naproxen for analgesia (27 (0-130) μM), antipyretics (40 (30-65) μM) and inhibition of PGE(2) (13 (6-45) μM) were in similar range, whereas inhibition of TXB(2) (5 (4-8) μM) was observed at lower concentrations. Variability in the behavioral measurement of analgesia was larger than for the other endpoints. The inhibition of fever by naproxen was followed by an increased rebound body temperature.

CONCLUSION

Due to better sensitivity and similar drug-induced inhibition, the biomarker PGE(2) and the antipyretic effect would be suitable alternative endpoints to the analgesic effects for characterization and comparisons of potency and time-courses of drug candidates affecting the COX-2 pathway and to support human dose projections.

Use of sensory methods for detecting target engagement in clinical trials of new analgesics

The translation of analgesic efficacy seen in preclinical pain models into the clinic is problematic and is associated with a number of factors that may result in the failure of clinical trials to detect the effect of investigational therapeutic agents. The use of translational pain biomarkers in phase I trials can potentially reduce some of these risks by measuring the interaction between the drug and its target (termed target engagement) in humans. To serve this purpose, sensory tests and other measures of pharmacological activity in nociceptive pathways need to be identified, based on the preclinical profile of the drug being tested and the feasibility of human assessments. Here we discuss some examples to assess the utility of sensory and related pain biomarkers in the early phase of evaluation of novel analgesics for confirmation of target engagement in humans. The emphasis is on the TRPV1 antagonists, but some other target mechanisms are also discussed in examining the validity of this approach.

Impact of chronic inflammation on the pharmacokinetic-pharmacodynamic relationship of naproxen

OBJECTIVES

The use of biomarkers for predicting the clinical doses of analgesic drugs relies on the understanding of the relationship between drug exposure and response under disease conditions. In this study, we demonstrate the relevance of such a relationship for COX-inhibitors by modelling the effect of naproxen on prostaglandin E2 (PGE(2)) and thromboxane B2 (TXB(2)) in a chronic inflammation model in rats.

METHODS

Rats were treated with Freund's complete adjuvant (FCA) by intraplantar injection. On post-inoculation days (PID) 7-21, animals received single or chronic (qd until day 21) doses of naproxen (10mg/kg). Blood samples were collected at various intervals after dosing to characterise naproxen pharmacokinetics and its effects on PGE(2) and TXB(2) production. PK-PD modelling was performed using nonlinear mixed effects in NONMEM.

RESULTS

The inhibition of PGE(2) and TXB(2) could be described by a sigmoid E(max) model. A decrease in the potency estimates of both biomarkers was observed under chronic inflammation, as compared to healthy animals. IC(50) values for PGE(2) inhibition showed a shift from 2840+/-510 to 4000+/-677ng/ml(mean+/-SD), whilst IC(50) values for TXB(2) inhibition increased from 1180+/-323 to 3360+/-453ng/ml in healthy and FCA-inoculated animals, respectively.

CONCLUSIONS

Our results show that chronic inflammation causes a significant change in the potency estimates for COX-inhibition. These findings illustrate the implications of pathophysiological processes on pharmacodynamics and consequently on the required exposure levels for achieving response during chronic treatment.

Pharmacological characterization of a selective COX-2 inhibitor MF-tricyclic, [3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl)phenyl)-2-(5H)-furanone], in multiple preclinical species

Selective type 2 cyclooxygenase (COX-2) inhibitors are often used in preclinical studies without potency and selectivity data in the experimental species. To address this issue, we assessed a selective COX-2 inhibitor MF-tricyclic in four commonly used species, namely mice, rats, guinea pigs and rabbits, in the present study. In both the guinea pig and rabbit whole blood assay, the compound inhibited lipopolysaccharide (LPS)-induced PGE(2) production with an IC(50) (COX-2) of 0.6 and 2.8 microM, respectively. By comparison, the compound displayed a much weaker activity on clot-induced formation of thromboxane with an IC(50) (COX-1) of >10 microM (guinea pigs) and 23 microM (rabbits). In keeping with the in vitro potency data, the compound significantly inhibited interleukin-1 beta (IL-1beta) -induced PGE(2) formation in the rabbit synovium at plasma concentrations near the whole blood assay IC(50) for COX-2 but much lower than that for COX-1. MF-tricyclic was also potent and selective toward COX-2 in mice, inhibiting carrageenan-induced PGE(2) accumulation in the air pouch dose-dependently (ED(50)=0.5 mg/kg) without affecting stomach PGE(2) levels. In rats, MF-tricyclic was found to be effective in three standard in vivo assays utilized for assessing COX-2 inhibitors, namely, LPS-induced pyresis, carrageenan-induced paw edema and adjuvant-induced arthritis at the doses that did not inhibit stomach PGE(2) levels. Similar to that in rats, the compound displayed pharmacological efficacy in mice, guinea pigs and rabbits when tested in the LPS pyresis model. Our data reveal that MF-tricyclic has the desired biochemical and pharmacological properties for selective COX-2 inhibition in all four test species.