CR13626: a novel oral brain penetrant tyrosine kinase inhibitor that reduces tumor growth and prolongs survival in a mouse model of glioblastoma.

Glioblastoma multiforme (GBM) is the most malignant primary brain cancer. Despite aggressive treatments currently there is no cure for GBM. Many challenges should be considered for the development of new therapeutical agents for glioblastoma, including appropriate target selectivity and pharmacokinetics. Several mutations and alterations of key cellular pathways including tyrosine kinases (TKs) are involved in malignant transformation and tumor progression. Thus, the targeting of multiple pathways and the development of innovative combination drug regimens is expected to yield improved therapies. Moreover, the abilities to cross the blood-brain barrier (BBB) reaching effective concentrations in brain and to remain into this tissue avoiding the effects of efflux transporters are also critical issues in the development of new therapeutics for GBM. CR13626 is a novel brain penetrant small molecule able to potently inhibit in vitro the activity of EGFR, VEGFR2 (aka KDR), Fyn, Yes, Lck, HGK (aka MAP4K4) and RET kinases relevant for GBM development. CR13626 shows good oral bioavailability (72%) and relevant brain penetration (brain/plasma ratio of 1.4). In an orthotopic xenograft glioblastoma mouse model, oral treatment with CR13626 results in a time-dependent reduction of tumor growth, leading to a significant increase of animal survival. The unique properties of CR13626 warrant its further investigation as a potential new drug candidate in glioblastoma.

Pharmacological characterisation of CR6086, a potent prostaglandin E2 receptor 4 antagonist, as a new potential disease-modifying anti-rheumatic drug.

BACKGROUND: Prostaglandin E2 (PGE2) acts via its EP4 receptor as a cytokine amplifier (e.g., interleukin [IL]-6) and induces the differentiation and expansion of inflammatory T-helper (Th) lymphocytes. These mechanisms play a key role in the onset and progression of rheumatoid arthritis (RA). We present the pharmacological characterisation of CR6086, a novel EP4 receptor antagonist, and provide evidence for its potential as a disease-modifying anti-rheumatic drug (DMARD). METHODS: CR6086 affinity and pharmacodynamics were studied in EP4-expressing HEK293 cells by radioligand binding and cyclic adenosine monophosphate (cAMP) production, respectively. In immune cells, IL-6 and vascular endothelial growth factor (VEGF) expression were analysed by RT-PCR, and IL-23 and IL-17 release were measured by enzyme-linked immunosorbent assay (ELISA). In collagen-induced arthritis (CIA) models, rats or mice were immunised with bovine collagen type II. Drugs were administered orally (etanercept and methotrexate intraperitoneally) starting at disease onset. Arthritis progression was evaluated by oedema, clinical score and histopathology. Anti-collagen II immunoglobulin G antibodies were measured by ELISA. RESULTS: CR6086 showed selectivity and high affinity for the human EP4 receptor (Ki = 16.6 nM) and functioned as a pure antagonist (half-maximal inhibitory concentration, 22 nM) on PGE2-stimulated cAMP production. In models of human immune cells in culture, CR6086 reduced key cytokine players of RA (IL-6 and VEGF expression in macrophages, IL-23 release from dendritic cells, IL-17 release from Th17 cells). In the CIA model of RA in rats and mice, CR6086 significantly improved all features of arthritis: severity, histology, inflammation and pain. In rats, CR6086 was better than the selective cyclooxygenase-2 inhibitor rofecoxib and at least as effective as the Janus kinase inhibitor tofacitinib. In mice, CR6086 and the biologic DMARD etanercept were highly effective, whereas the non-steroidal anti-inflammatory drug naproxen was ineffective. Importantly, in a study of CR6086/methotrexate, combined treatment greatly improved the effect of a fully immunosuppressive dose of methotrexate. CONCLUSIONS: CR6086 is a novel, potent EP4 antagonist showing favourable immunomodulatory properties, striking DMARD effects in rodents, and anti-inflammatory activity targeted to immune-mediated inflammatory diseases and distinct from the general effects of cyclooxygenase inhibitors. These results support the clinical development of CR6086, both as a stand-alone DMARD and as a combination therapy with methotrexate. The proof-of-concept trial in patients with RA is ongoing.

The Pros and the Cons for the Use of Silybin-Rich Oral Formulations in Treatment of Liver Damage (NAFLD in Particular).

The increasing prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD) worldwide is becoming a challenge for the modern global care system. The lipotoxic process is characterized by an oxidative stress followed by a burst of the inflammatory response, prompting the wound healing process (fibrosis), which can ultimately lead to the development of cirrhosis and the subsequent complications. There is no consensus concerning an effective pharmacological treatment. Therefore, there is a need for effective therapeutic compounds. Silibinin the major active compound of Milk Thistle may be a potential candidate mainly due to its anti-oxidant, anti-inflammatory, and anti-fibrotic properties. In spite of the large number of data obtained in experimental models, the translation of the evidence in clinical setting is far to be conclusive. The aim of this paper is to critically review the aspects of the use of the different formulations of Silibinin in several experimental and clinical settings and to provide hints on the needed future studies.

Development and validation of two liquid chromatography-tandem mass spectrometry methods for the determination of silibinin and silibinin hemisuccinate in human plasma.

To investigate the pharmacokinetics of silibinin and silibinin hemisuccinate in human plasma, two high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) methods were developed and validated. The methods require a small volume of sample (100µL), and the recovery of the analytes was complete with a good reproducibility (CV% 1.7-9.5), after a simple protein precipitation. Naringenin was used as internal standard. The chromatographic methods provided a good separation of diastereoisomers A and B of both silibinin and silibinin hemisuccinate onto a Chromolith Performance RP18e 100mm×3mm column, with a resolution of peaks from plasma matrix in less than 6min. The methods precision values expressed as CV% were always ≤6.2% and the accuracy was always well within the acceptable 15% range. Quantification was performed on a triple-quadrupole tandem mass spectrometer by Selected Reaction Monitoring (SRM) mode, in a negative ion mode, via electrospray ionization (ESI). The lower limit of quantitation was set at 5.0ng/mL (silibinin) and 25.0ng/mL (silibinin hemisuccinate), and the linearity was validated up to 1000.0 and 12,500.0ng/mL, for silibinin and silibinin hemisuccinate, respectively, with correlation coefficients (R(2)) of 0.991 or better. The methods were suitable for pharmacokinetic studies and were successfully applied to human plasma samples from subjects treated intravenously with Legalon(®) SIL at the dose of 20mg/kg, expressed as silibinin.

Enhancing the pharmacodynamic profile of a class of selective COX-2 inhibiting nitric oxide donors.

We report herein the development, synthesis, physicochemical and pharmacological characterization of a novel class of pharmacodynamic hybrids that selectively inhibit cyclooxygenase-2 (COX-2) isoform and present suitable nitric oxide releasing properties. The replacement of the ester moiety with the amide group gave access to in vivo more stable and active derivatives that highlighted outstanding pharmacological properties. In particular, the glycine derivative proved to be extremely active in suppressing hyperalgesia and edema.

Silibinin hemisuccinate binding to proteins in plasma and blood cell/plasma partitioning in mouse, rat, dog and man in vitro.

BACKGROUND: The determination of plasma protein binding and blood cell/plasma partitioning is important when prescribing silibinin hemisuccinate to patients concomitantly receiving other drugs and to estimate the safety margins of exposure at the no observed adverse events levels determined from toxicity studies conducted in rats and dogs. METHODS: Protein binding of [3'-14C]silibinin hemisuccinate (1, 10, 100, 1000 and 4000 µM) was evaluated in human, dog, rat and mouse plasma by ultrafiltration. Blood cell/plasma partitioning in all these species was also determined. RESULTS: Silibinin hemisuccinate is highly bound to plasma proteins with percentage binding ranging from 94.3% to 97.8%. Its association with blood cells was negligible (<7%) in all species. The degree of protein binding was concentration independent up to the pharmacologically effective concentration of 100 µM. The blood cell/plasma partitioning indicates that distribution into blood cells is not an important feature for the disposition of silibinin hemisuccinate. CONCLUSIONS: No corrections for fraction unbound are needed when comparing human and preclinical pharmacokinetic and pharmacodynamic data at pharmacological doses, and it is appropriate to analyze plasma as opposed to whole blood for the determination of silibinin hemisuccinate concentrations.

Crystalline glucosamine sulfate in the management of knee osteoarthritis: efficacy, safety, and pharmacokinetic properties.

Glucosamine is an amino monosaccharide and a natural constituent of glycosaminoglycans in articular cartilage. When administered exogenously, it is used for the treatment of osteoarthritis as a prescription drug or a dietary supplement. The latter use is mainly supported by its perception as a cartilage building block, but it actually exerts specific pharmacologic effects, mainly decreasing interleukin 1-induced gene expression by inhibiting the cytokine intracellular signaling cascade in general and nuclear factor-kappa B (NF-kB) activation in particular. As a whole, the use of glucosamine in the management of osteoarthritis is supported by the clinical trials performed with the original prescription product, that is, crystalline glucosamine sulfate. This is the stabilized form of glucosamine sulfate, while other formulations or different glucosamine salts (e.g. hydrochloride) have never been shown to be effective. In particular, long-term pivotal trials of crystalline glucosamine sulfate 1500 mg once daily have shown significant and clinically relevant improvement of pain and function limitation (symptom-modifying effect) in knee osteoarthritis. Continuous administration for up to 3 years resulted in significant reduction in the progression of joint structure changes compared with placebo as assessed by measuring radiologic joint space narrowing (structure-modifying effect). The two effects combined may suggest a disease-modifying effect that was postulated based on an observed decrease in the risk of undergoing total joint replacement in the follow up of patients receiving the product for at least 12 months in the pivotal trials. The safety of the drug was good in clinical trials and in the postmarketing surveillance. Crystalline glucosamine sulfate 1500 mg once daily is therefore recommended in the majority of clinical practice guidelines and was found to be cost effective in pharmacoeconomic analyses. Compared with other glucosamine formulations, salts, or dosage forms, the prescription product achieves higher plasma and synovial fluid concentrations that are above the threshold for a pharmacologically relevant effect, and may therefore justify its distinct therapeutic characteristics.

Identification and quantification of glucosamine in rabbit cartilage and correlation with plasma levels by high performance liquid chromatography-electrospray ionization-tandem mass spectrometry.

A new HPLC-ESI-MS/MS method for the determination of glucosamine (2-amino-2-deoxy-d-glucose) in rabbit cartilage was developed and optimized. Glucosamine was extracted from cartilage by cryogenic grinding followed by protein precipitation with trichloroacetic acid. The HPLC separation was achieved with a polymer-based amino column using a mobile phase composed of 10mM ammonium acetate (pH 7.5)-acetonitrile (20:80%, v/v) at 0.3 mL min flow rate. d-[1-(13)C]Glucosamine was used as internal standard. Selective detection was performed by tandem mass spectrometry with electrospray source, operating in positive ionization mode and in multiple reaction monitoring acquisition (m/z 180→72 and 181→73 for glucosamine and internal standard, respectively). Limit of quantification was 0.045 ng injected, corresponding to 0.25 µg g⁻¹ in cartilage. Linearity was obtained up to 20 µg g⁻¹ (R(2)>0.991). Precision values (%R.S.D.) were <10%. Accuracy (% bias) ranged from -6.0% to 12%. Mean recoveries obtained at 3 concentration levels were higher than 81% (%R.S.D.≤8%). The method was applied to measure glucosamine levels in rabbit cartilage and plasma after single oral administration of glucosamine sulfate at a dose of 98 mg kg⁻¹(n=6). Glucosamine was present in cartilage in physiological condition before the treatment. After dosing, mean concentration of cartilage glucosamine significantly increased from 461 to 1040 ng g⁻¹. Cartilage glucosamine levels resulted to be well correlated with plasma concentrations, which therefore are useful to predict the target cartilage concentration and its pharmacological activity.

Relationship among pharmacokinetics and pharmacodynamics of fenretinide and plasma retinol reduction in neuroblastoma patients.

PURPOSE: Fenretinide (4-HPR), a synthetic retinoid currently used in clinic for cancer therapy and prevention, markedly lowers plasma retinol levels, an effect associated with nyctalopia. Our aim was to investigate the relationship between 4-HPR pharmacokinetics, plasma retinol reduction and incidence of nyctalopia. PATIENTS AND METHODS: Children with neuroblastoma, participating in a phase I trial, were treated with oral 4-HPR, once a day for 28-day courses followed by a 7-day drug interruption, with escalating dose levels from 100 to 4,000 mg/m(2) per day. Blood samples were collected at baseline and up to 48 h after the 1st (50 patients) and 28th (41 patients) administration, and the plasma concentrations of 4-HPR and retinol were measured by HPLC. RESULTS: After the first administration, nadir retinol concentrations were reached at 16-20 h post-dosing; the extent of retinol reduction was related to 4-HPR dose and plasma concentrations as well as to pretreatment retinol concentrations. After repeated treatments, nadir retinol concentrations (10-20% of baseline values) were maintained during the 24 h dosing interval and were similar at all doses; the extent of retinol reduction was significantly (r = 0.97, P < 0.0001) related to pretreatment retinol concentrations. After a single dose, the relationship between 4-HPR pharmacokinetics and pharmacodynamics indicated a counterclockwise hysteresis suggesting the presence of an effect compartment. At steady state, the hysteresis collapsed suggesting that the 4-HPR concentrations in plasma and in the effect compartments were in equilibrium. Nyctalopia was not related to the administered dose, but was significantly associated (P = 0.05) with lower nadir retinol concentrations (0.11 +/- 0.012 vs. 0.17 +/- 0.015 microM). CONCLUSIONS: During 4-HPR chronic treatment, plasma retinol reduction is not proportional to the dose. Plasma retinol levels of 0.11 microM could be considered as a safety biomarker in children with neuroblastoma. Finally, since initial retinol levels strongly predict the extent of retinol reduction, retinol decrease could be used to monitor 4-HPR compliance.

In vitro study of the inhibition and induction of human cytochromes P450 by crystalline glucosamine sulfate.

The induction and inhibition of human hepatic cytochrome P450 (CYP) isoforms by crystalline glucosamine sulfate (CGS) was investigated in vitro. Inhibition of CYP1A2, CYP2E1, CYP2C19, CYP2C9, CYP2D6, and CYP3A4 by CGS was assessed using recombinant human enzymes incubated with CGS (up to 3 mM expressed as free base). Induction of CYP1A2, CYP2B6, CYP2C9, CYP2C19 and CYP3A4 by CGS (0.01, 0.3 and 3 mM) was evaluated in cryopreserved human hepatocytes, by determining CYP mRNA expression using quantitative RT-PCR. CGS produced no inhibition or induction of any the CYP enzymes tested at concentrations hundred folds higher than the steady state peak plasma concentrations (approximately 10 microM) observed in man after therapeutic doses of CGS of 1500 mg once a day. Therefore, no clinically relevant metabolic interactions are expected between CGS and co-administered drugs that are substrates of the CYP enzymes investigated.

Glucosamine binding to proteins in plasma and synovial fluid and blood cell/plasma partitioning in mouse and man in vitro.

Protein binding of [14C]glucosamine (400, 1000 and 4000 ng/ml) was evaluated in human and mouse plasma and in human synovial fluid. Blood cell/plasma partitioning in human and mouse was also determined. There was no measurable protein binding of [14C]glucosamine. Its association with human and mouse blood cells ranged from 43-47% and from 27-29%, respectively. Therefore, the unbound (pharmacologically active) fraction of glucosamine in plasma and at the site of action (the joint) is the same. Protein binding displacement drug-drug interactions are unlikely during the clinical use of crystalline glucosamine sulfate. No corrections are needed, either for unbound fraction when comparing human and mouse pharmacokinetic data or for blood cell/plasma partitioning to assess glucosamine total blood clearance from plasma data in these two species.

Pharmacokinetics of oral fenretinide in neuroblastoma patients: indications for optimal dose and dosing schedule also with respect to the active metabolite 4-oxo-fenretinide.

PURPOSE: Pharmacokinetic data on fenretinide (4-HPR) are scant, thus limiting the rational use of the drug. We investigated the pharmacokinetics of 4-HPR and its active metabolite 4-oxo-fenretinide (4-oxo-4-HPR). EXPERIMENTAL DESIGN: Pharmacokinetics were assessed in 18 children (3 for each dose) with neuroblastoma who received oral 4-HPR once daily for 28 days at the doses of 100, 300, 400, 600, 1,700 and 4,000 mg/m(2)/day. 4-HPR and 4-oxo-4-HPR were determined by HPLC in plasma collected up to 48 h after the first and 28th administration. RESULTS: After single administration, 4-HPR mean C (max) ranged from 0.9 to 6.6 microM and these concentrations roughly doubled at steady state (range 1.6-14.5 microM). 4-HPR mean t (1/2) was 22 h. 4-HPR pharmacokinetics were linear in the dose range 100-1,700 mg/m(2); less than dose-proportional increase in exposure was found at 4,000 mg/m(2). At steady state, pharmacologically relevant plasma concentrations (range 0.7-10 microM and 0.4-5 microM for 4-HPR and 4-oxo-4-HPR, respectively) were maintained during the 24 h dosing interval in the dose range 300-4,000 mg/m(2). CONCLUSIONS: 4-HPR pharmacokinetics supports once-daily dosing. Steady state concentrations of 4-HPR and 4-oxo-4-HPR in children with neuroblastoma are in line with those found to have in vitro growth inhibitory effects in neuroblastoma cells.

Pharmacokinetic profile of dexloxiglumide.

Dexloxiglumide is a potent and selective cholecystokinin type 1 (CCK1) receptor antagonist currently under development in a variety of diseases affecting the gastrointestinal tract such as gastro-oesophageal reflux disease, irritable bowel syndrome (IBS), functional dyspepsia, constipation and gastric emptying disorders. In female patients with constipation-predominant IBS, clinical efficacy has been demonstrated following administration of dexloxiglumide 200 mg three times daily. Dexloxiglumide is rapidly and extensively absorbed after single oral administration in humans with an absolute bioavailability of 48%. The incomplete bioavailability is due to both incomplete absorption and hepatic first-pass effect. Following multiple-dose administration of 200 mg three times daily, the accumulation is predictable, indicating time-independent pharmacokinetics. In addition, dexloxiglumide pharmacokinetics are dose-independent after both single and repeated oral three-times-daily doses in the dose range 100-400 mg. Dexloxiglumide absorption window extends from the jejunum to the colon and the drug is a substrate and a weak inhibitor of P-glycoprotein and multidrug resistance protein 1. Plasma protein binding of dexloxiglumide is 94-98% and the drug has a moderate to low volume of distribution in humans. Systemic clearance of dexloxiglumide is moderate and cytochrome P450 (CYP) 3A4/5 and CYP2C9 have been implicated in the metabolism of dexloxiglumide to produce O-demethyl dexloxi-glumide. This metabolite is further oxidised to dexloxiglumide carboxylic acid. These two major metabolites (accounting for up to 50% of dexloxiglumide elimination) have been identified. However, in human plasma the unchanged drug represents the major (up to 91%) component of the metabolic profile. The parent drug is believed to be the major contributor to the efficacy of the compound, since its major metabolites are pharmacologically inactive. In addition, the drug is a single isomer chiral drug (eutomer) that does not undergo chiral inversion into its pharmacologically inactive enantiomer (distomer). After oral administration of (14)C-dexloxiglumide, radioactivity is mainly excreted in bile and in faeces (74% of dose) with much lower excretion in urine (20% of dose). Renal excretion of unchanged dexloxiglumide is low (7% of dose in urine and faeces, 1% of dose in urine) and is dose-independent in the dose range 100-400 mg. As the kidney is a minor contributor to the elimination of dexloxiglumide and/or its metabolites in humans, the pharmacokinetics of the drug should not be affected in patients with renal insufficiency. The pharmacokinetics of dexloxiglumide are also not affected by age, sex and administration with a high-fat breakfast. Mild and moderate liver impairment do not affect the pharmacokinetics of dexloxiglumide but severe liver impairment causes increases in systemic exposure to dexloxiglumide and O-demethyl dexloxiglumide. Thus, the drug should be prescribed with caution in patients with severe hepatic impairment even though no dose adjustment is warranted. The results of different drug interaction studies have indicated that no clinically relevant metabolic and concomitant drug-drug interactions are expected during the clinical use of dexloxiglumide.

Strategies to assess the drug interaction potential in translational medicine.

Translational medicine is the drug development phase in which preclinical and clinical applied research is conducted to aid dose and disease selection with great financial impact. Thus, during this phase, early discontinuation of a drug that will later fail due to drug interactions is a must for a proper resource allocation. It is not only important to identify a potential interaction, but also to be able to differentiate between detectable interactions and clinically relevant interactions. Due to the scientific advancement, the prediction of drug interactions during translational medicine has shifted from empirical/observational to rational based. These investigations are thus in line with the FDA's Critical Path Initiative and are facilitated by the availability of mature technologies and by current European and US guidelines for both in vitro and in vivo studies. Because drug interactions must be evaluated in a multidisciplinary fashion, even if these studies are contracted externally, pharmaceutical companies should be directly involved in the conduction of such studies to fully exploit their potential and to allow a better and faster interpretation of the results.

Development and validation of a sensitive HPLC-ESI-MS/MS method for the direct determination of glucosamine in human plasma.

A sensitive and specific HPLC-ESI-MS/MS method for the direct determination of glucosamine in human plasma has been developed and validated. Plasma samples were analyzed after a simple, one-step protein precipitation clean-up with trichloroacetic acid using a polymer-based amino high-performance liquid chromatography (HPLC) column and a water/acetonitrile mobile phase elution gradient, with d-[1-(13)C]glucosamine as the internal standard. Detection was performed by mass spectrometry, using an electrospray source and employing multiple reaction monitoring to separately monitor glucosamine and the internal standard. The limit of quantification of the method was 10ng/ml of glucosamine and the calibration curve showed a good linearity up to 1000ng/ml. The precision (R.S.D.) and the accuracy (bias) of the method at the limit of quantification were 13.8 and 4.0%, respectively, and the mean recovery of glucosamine at three concentration levels was 101.6+/-5.7%. The method was applied for the determination of glucosamine concentrations in human plasma samples collected from untreated healthy volunteers and, in a separate bioavailability study, to evaluate plasma glucosamine pharmacokinetics profiles after oral administration of crystalline glucosamine sulfate.

Effect of azole antifungals ketoconazole and fluconazole on the pharmacokinetics of dexloxiglumide.

AIMS: Dexloxiglumide is a new CCK(1) receptor antagonist under investigation for treatment of functional gastrointestinal disorders and is metabolized by CYP3A4 and CYP2C9. The objectives of these two separate randomized, two-period, two-treatment crossover studies were to investigate the effects of steady-state ketoconazole, a model CYP3A4 inhibitor (Study 1), and steady-state fluconazole, a model CYP2C9 inhibitor (Study 2), on the pharmacokinetics of dexloxiglumide in healthy subjects. METHODS: Plasma samples were analysed for dexloxiglumide and its primary metabolites: O-demethyl dexloxiglumide (ODM; Study 1 and 2) and dexloxiglumide carboxylic acid (DCA; Study 2). RESULTS: Following ketoconazole coadministration, dexloxiglumide C(max) increased by 32% (90% confidence intervals (CI) 112-154), with unchanged ODM C(max); AUC of dexloxiglumide and ODM increased by 36% (90% CI 124-140 and 128-142, respectively). No changes were observed in dexloxiglumide or ODM t((1/2)). Fluconazole coadministration caused a 77% increase (90% CI 154-204) in dexloxiglumide C(max), no change in ODM C(max) and a 32% decrease (90% CI 62-75) in DCA C(max). Fluconazole coadministration resulted in a 2.5-fold increase (90% CI 235-267) in dexloxiglumide AUC, 40% increase (90% CI 136-156) in ODM AUC and an 18% decrease (90% CI 82-94) in DCA AUC. The t((1/2)) of all three analytes increased by approximately 2-fold with fluconazole coadministration (P-value < 0.05). CONCLUSIONS: Ketoconazole caused a minimal increase while fluconazole caused a moderate increase in dexloxiglumide systemic exposure with no change in the adverse event profile of dexloxiglumide.

Effect of multiple-dose dexloxiglumide on the pharmacokinetics of oral contraceptives in healthy women.

This study was undertaken to evaluate the effect of dexloxiglumide, a selective cholecystokinin receptor antagonist, on the pharmacokinetics of a combination oral contraceptive (OC). A single-blind, placebo-controlled, 2-period crossover study was conducted in 24 healthy young female subjects who received Ortho Tri-Cyclen containing ethinyl estradiol (EE, 0.035 mg) and norgestimate (NE, 0.180 mg/0.215 mg/0.250 mg per 7-day phase, respectively) for 5 days (days 17-21) concurrently with either 200 mg dexloxiglumide (3 times a day on days 17-20, followed by a single dose on day 21) or matching placebo during 2 consecutive 28-day OC dosing cycles. Plasma was sampled up to 24 hours for the determination of EE, NE, and 17-deactyl norgestimate (17-DNE, a rapidly formed pharmacologically active metabolite of NE). The geometric mean ratios (GMRs, dexloxiglumide/placebo) of the plasma concentration-time curve over 24 hours with corresponding 90% confidence intervals (CIs) for EE and 17-DNE were 1.21 (1.17-1.26) and 0.92 (0.89-0.95), respectively. The GMRs (90% CI) of C(max) for EE and 17-DNE were 1.15 (1.09-1.20) and 0.93 (0.90-0.96), respectively. Coadministration of OC and dexloxiglumide was well tolerated and safe. Comparable systemic exposure of EE and 17-DNE in the presence and absence of dexloxiglumide suggests that dexloxiglumide treatment is unlikely to interfere with the safety and efficacy of oral contraceptives based on the analysis of the resulting pharmacokinetic profile.

Interaction of dexloxiglumide, a cholecystokinin type-1 receptor antagonist, with human cytochromes P450.

Dexloxiglumide (DEX) is a cholecystokinin type-1 receptor antagonist under development for the treatment of constipation-predominant irritable bowel syndrome. Studies of the potential interaction of DEX with human cytochromes P450 (CYPs) were conducted in vitro. DEX (300 micro M), both with and without a 15-min pre-incubation, was incubated with pooled human liver microsomes and substrates selective for each of eight CYPs. This resulted in >30% inhibition of tolbutamide 4-methyl-hydroxylase (CYP2C9/10) and lauric acid 11-hydroxylase (CYP2E1) activities. Mean K(i) (SD) for CYP2C9/10 and CYP2E1 were 69.0 (24.3) and 426 (60) microM, respectively. Incubations of [(14)C]DEX with pooled human liver microsomes produced one major phase I metabolic fraction, with V(max)=131 pmol/min/mg protein and K(m)=23.7 microM. Further incubations with (i) liver microsomes from 16 individual donors (correlation analysis), (ii) Supersomes trade mark and (iii) selective chemical inhibitors, implicated CYP3A4/5, CYP2B6 and CYP2C9 in the formation of this component. Thus, DEX interacts with CYP2C9 both as inhibitor (K(i)=69.0 microM) and as substrate in vitro. However, based on the maximum concentration (27 microM) after repeated oral doses of 200 mg t.i.d. and the unbound fraction (0.03) of DEX in human plasma, no clinically relevant metabolic interactions with other CYP substrates are predicted.