St. John's wort extract with a high hyperforin content does not induce P-glycoprotein activity at the human blood-brain barrier

St. John's wort (SJW) extract, a herbal medicine with antidepressant effects, is a potent inducer of intestinal and/or hepatic cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp), which can cause clinically relevant drug interactions. It is currently not known whether SJW can also induce P-gp activity at the human blood-brain barrier (BBB), which may potentially lead to decreased brain exposure and efficacy of certain central nervous system (CNS)-targeted P-gp substrate drugs. In this study, we used a combination of positron emission tomography (PET) imaging and cocktail phenotyping to gain a comprehensive picture on the effect of SJW on central and peripheral P-gp and CYP activities. Before and after treatment of healthy volunteers (n = 10) with SJW extract with a high hyperforin content (3-6%) for 12-19 days (1800 mg/day), the activity of P-gp at the BBB was assessed by means of PET imaging with the P-gp substrate [11C]metoclopramide and the activity of peripheral P-gp and CYPs was assessed by administering a low-dose phenotyping cocktail (caffeine, omeprazole, dextromethorphan, and midazolam or fexofenadine). SJW significantly increased peripheral P-gp, CYP3A, and CYP2C19 activity. Conversely, no significant changes in the peripheral metabolism, brain distribution, and P-gp-mediated efflux of [11C]metoclopramide across the BBB were observed following the treatment with SJW extract. Our data suggest that SJW does not lead to significant P-gp induction at the human BBB despite its ability to induce peripheral P-gp and CYPs. Simultaneous intake of SJW with CNS-targeted P-gp substrate drugs is not expected to lead to P-gp-mediated drug interactions at the BBB.

Pharmacokinetics and Bioequivalence of Mirogabalin Orally Disintegrating Tablets and Conventional Tablets in Healthy Japanese Participants

This single-center, randomized, open-label, single-dose, 2-group, 2-stage crossover trial evaluated the bioequivalence of 15 mg of mirogabalin as orally disintegrating tablets (ODTs) with conventional mirogabalin tablets in healthy Japanese men. The trial involved two studies: in Study 1, the ODT formulation was taken without water, and in Study 2, the ODT formulation was taken with water. The conventional tablet was taken with water in both studies. We investigated the pharmacokinetic parameters and bioequivalence of the 2 formulations, including the maximum plasma concentration and the area under the plasma concentration-time curve up to the last quantifiable time. The plasma concentrations of mirogabalin were determined by a validated liquid chromatography with tandem mass spectrometry method. A total of 72 participants were enrolled and completed the trial. The geometric least-squares mean ratios of maximum plasma concentration of the ODT formulation to the conventional formulation were within the prespecified bioequivalence range of 0.80-1.25 (Study 1, 0.995; Study 2, 1.009), as was the area under the plasma concentration-time curve up to the last quantifiable time (Study 1, 1.023; Study 2, 1.035). No serious adverse events were observed. In conclusion, mirogabalin 15-mg ODTs, either with or without water, were bioequivalent to conventional 15-mg tablets.

Safety, Tolerability and Pharmacokinetics of Single and Multiple Doses of Mirogabalin in Healthy Chinese Participants: A Randomized, Double-Blind, Placebo-Controlled Study

INTRODUCTION

Mirogabalin is a treatment option for patients with neuropathic pain; however, safety, tolerability, and pharmacokinetics (PK) data specifically for Chinese individuals are limited to a single-dose study. We aimed to assess these for both single- and multiple-dose mirogabalin in healthy Chinese participants.

METHODS

In this randomized, double-blind, placebo-controlled, phase I study, 54 healthy Chinese men and women aged 18-45 years were randomly allocated to receive single- (5, 10, or 15 mg, daily) or multiple-dose (5 mg titrated to 15 mg, twice-daily, over 22 days) oral mirogabalin or placebo. In each of three single-dose groups, 10 participants received mirogabalin and 2 received placebo; in the multiple-dose group, 14 participants received mirogabalin and 4 received placebo. The primary endpoints were PK, safety, and tolerability variables, including treatment-emergent adverse events (TEAEs), laboratory tests, and vital signs. PK data were collected for both single- and multiple-dose cohorts and evaluated by non-compartmental analysis.

RESULTS

Single- and multiple-dose mirogabalin was generally well tolerated with no deaths, serious TEAEs, or TEAEs leading to treatment discontinuation. Frequently reported TEAEs included dizziness, nystagmus, increased blood triglycerides, headache, and increased blood uric acid and creatine phosphokinase. Single-dose mirogabalin was rapidly absorbed (median time to maximum plasma concentration, 1.00 h) and eliminated (mean terminal elimination half-life, 2.57-3.08 h). The exposure was approximately dose-proportional. In the multiple-dose cohort, the trough plasma concentration increased dose-proportionally, and exposure and clearance were comparable to that following a single 15-mg dose. The mean cumulative amount excreted into urine up to 48 h post-dose increased in a dose-proportional manner, the mean cumulative percentage excreted into urine was 61.9%-74.3%, and renal clearance remained relatively constant.

CONCLUSION

Consistent with previous phase I studies in other populations, mirogabalin was safe and well tolerated in healthy Chinese participants at single and multiple doses of up to 15 mg twice-daily.

Coadministration of probenecid and cimetidine with mirogabalin in healthy subjects: A phase 1, randomized, open-label, drug-drug interaction study

AIMS

The primary aim of this study was to assess the individual effects of probenecid and cimetidine on mirogabalin exposure.

METHODS

This phase 1, open-label, crossover study randomized healthy adults to receive three treatment regimens, each separated by ≥5-day washout: a single oral dose of mirogabalin 15 mg on day 2, mirogabalin 15 mg on day 2 plus probenecid 500 mg every 6 h from days 1 to 4, and mirogabalin 15 mg on day 2 plus cimetidine 400 mg every 6 h from days 1 to 4.

RESULTS

Coadministration of mirogabalin with probenecid or cimetidine increased the maximum and total mirogabalin exposure. The geometric mean ratios of Cmax and AUC(0-t) (90% CI) with and without coadministration of probenecid were 128.7% (121.9-135.7%) and 176.1% (171.9-180.3%), respectively. The geometric mean ratios of Cmax and AUC(0-t) (90% CI) with and without coadministration of cimetidine were 117.1% (111.0-123.6%) and 143.7% (140.3-147.2%), respectively. Mean (standard deviation) renal clearance of mirogabalin (l h-1 ) was substantially slower after probenecid [6.67 (1.53)] or cimetidine [7.17 (1.68)] coadministration, compared with mirogabalin alone [11.3 (2.39)]. Coadministration of probenecid or cimetidine decreased mirogabalin mean (standard deviation) apparent total body clearance [10.5 (2.33) and 12.8 (2.67) l h-1 , respectively, vs. 18.4 (3.93) for mirogabalin alone].

CONCLUSIONS

A greater magnitude of change in mirogabalin exposure was observed when coadministered with a drug that inhibits both renal and metabolic clearance (probenecid) vs. a drug that only affects renal clearance (cimetidine). However, as the increase in exposure is not clinically significant (>2-fold), no a priori dose adjustment is recommended.

A Randomized, Placebo-Controlled, Double-Blind Study of the Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of Single and Repeated Doses of Mirogabalin in Healthy Asian Volunteers

Mirogabalin is a novel, preferentially selective α₂ δ-1 ligand under investigation to treat neuropathic pain. The purpose of this study was to evaluate the safety, tolerability, and pharmacokinetics of various doses of mirogabalin in healthy subjects of different ethnicities. This randomized, placebo-controlled, double-blind, sequential, ascending-dose study evaluated single (10-40 mg) and repeated (10, 15 mg twice a day) doses of mirogabalin in Japanese subjects, and a single dose of mirogabalin in Korean, Chinese, and white subjects. Mirogabalin was rapidly absorbed, with a median time to maximum plasma concentration of 1 hour, and rapidly eliminated, with a mean elimination half-life of 2 to 3 hours. Single-dose mirogabalin pharmacokinetic parameters were comparable between Asian and white subjects. Exposure increased proportionally as mirogabalin dose increased in Japanese subjects. Mean mirogabalin steady-state clearance and volume of distribution values were comparable across dose levels. No accumulation of mirogabalin was observed on repeated dosing in Japanese subjects. Mirogabalin had an acceptable safety and tolerability profile in Asian and white subjects at doses up to 15 mg twice a day for 7 days. The most common treatment-emergent adverse events (somnolence, headache, and dizziness) were consistent with the known mechanism of action and safety profile of mirogabalin.

Pharmacokinetics and Safety of a Single Oral Dose of Mirogabalin in Japanese Subjects With Varying Degrees of Renal Impairment

Mirogabalin (DS-5565) is a novel preferentially selective α2 δ-1 ligand being developed for the treatment of diabetic peripheral neuropathic pain and postherpetic neuralgia. The current multicenter open-label study determined the effect of varying degrees of renal impairment on the pharmacokinetics and safety of a single dose of mirogabalin 5 mg in Japanese subjects. A total of 30 subjects (6 subjects per renal function category [normal, mild, moderate, or severe impairment; and end-stage renal disease (ESRD)]) were enrolled and completed the study. The AUClast increased with severity of renal impairment; the geometric least-squares mean ratios of AUClast compared with subjects with normal renal function were 1.3, 1.9, 3.6, and 5.3 for patients with mild, moderate, and severe impairment and ESRD, respectively. In accordance with this AUClast increase, apparent total body clearance (CL/F), renal clearance (CLr), and the cumulative percentage of mirogabalin dose excreted into urine all decreased with severity of renal impairment. There were no deaths and no severe treatment-related adverse events (TEAEs), serious TEAEs, or TEAEs resulting in study discontinuation. Mirogabalin was well tolerated in Japanese subjects with normal renal function and those with mild to severe renal impairment. It was also tolerated in subjects with ESRD but with a higher incidence of TEAEs. The most frequently reported TEAEs were dizziness (ESRD, n = 3), somnolence (ESRD, n = 2), and vomiting (ESRD, n = 2). Based on these data, a mirogabalin dose adjustment will be considered in Japanese subjects with moderate to severe renal impairment and those with ESRD.

[2.2.1]-Bicyclic sultams as potent androgen receptor antagonists

This letter describes the discovery, synthesis, SAR, and biological activity of [2.2.1]-bicyclic sultams as potent antagonists of the androgen receptor. Optimization of the series led to the identification of compound 25, which displayed robust pharmacodynamic effects in rats after oral dosing.

Novel bicyclo[3.1.0]hexane analogs as antagonists of metabotropic glutamate 2/3 receptors for the treatment of depression

Negative modulators of metabotropic glutamate 2 & 3 receptors demonstrate antidepressant-like activity in animal models and hold promise as novel therapeutic agents for the treatment of major depressive disorder. Herein we describe our efforts to prepare and optimize a series of conformationally constrained 3,4-disubstituted bicyclo[3.1.0]hexane glutamic acid analogs as orthosteric (glutamate site) mGlu_2/3 receptor antagonists. This work led to the discovery of a highly potent and efficacious tool compound 18 (hmGlu₂ IC₅₀ 46±14.2nM, hmGlu₃ IC₅₀=46.1±36.2nM). Compound 18 showed activity in the mouse forced swim test with a minimal effective dose (MED) of 1mg/kg ip. While in rat EEG studies it exhibited wake promoting effects at 3 and 10mg/kg ip without any significant effects on locomotor activity. Compound 18 thus represents a novel tool molecule for studying the impact of blocking mGlu_2/3 receptors both in vitro and in vivo.

Aryl uracil inhibitors of hepatitis C virus NS5B polymerase: synthesis and characterization of analogs with a fused 5,6-bicyclic ring motif

The synthesis and structure-activity relationships of a novel aryl uracil series which contains a fused 5,6-bicyclic ring unit for HCV NS5B inhibition is described. Several analogs display replicon cell culture potencies in the low nanomolar range along with excellent rat pharmacokinetic values.

Selective CB2 agonists with anti-pruritic activity: discovery of potent and orally available bicyclic 2-pyridones

The CB2 receptor has emerged as a potential target for the treatment of pruritus as well as pain without CB1-mediated side effects. We previously identified 2-pyridone derivatives 1 and 2 as potent CB2 agonists; however, this series of compounds was found to have unacceptable pharmacokinetic profiles with no significant effect in vivo. To improve these profiles, we performed further structural optimization of 1 and 2, which led to the discovery of bicyclic 2-pyridone 18e with improved CB2 affinity and selectivity over CB1. In a mouse pruritus model, 18e inhibited compound 48/80 induced scratching behavior at a dose of 100 mg/kg. In addition, the docking model of 18e with an active-state CB2 homology model indicated the structural basis of its high affinity and selectivity over CB1.

Metabolism of procymidone derivatives in female rats

PCM-CH2OH [N-(3,5-dichlorophenyl)-1-hydroxymethyl-2-methylcyclopropane-1,2-dicarboximide] and PA-CH2OH [2-carboxyl-N-(3,5-dichlorophenyl)-1-hydroxymethyl-2-methylcyclopropane-1-carboxamide] are metabolites of the fungicide procymidone [N-(3,5-dichlorophenyl)-1,2-dimethylcyclopropane-1,2-dicarboximide] in rat. The distribution and metabolism of PCM-CH2OH and PA-CH2OH were here clarified by analyzing plasma and tissues (liver, kidney, heart, lung, spleen and ovary) of female rats after single subcutaneous administration of [phenyl-14C]PCM-CH2OH and [phenyl-14C]PA-CH2OH at 62.5 mg/kg, respectively. In both rats dosed with PCM-CH2OH and PA-CH2OH, the radioactivity was similarly distributed into plasma and tissues, and PA-CH2OH was detected as the main metabolite in plasma, whereas PCM-CH2OH predominated in tissues except for kidney at 1 h after administration of PA-CH2OH. Furthermore, the cyclization ratio [PCM-CH2OH/(PCM-CH2OH+PA-CH2OH)] increased in tissues of PA-CH2OH dosed rats with passage of time. Both procymidone and PCM-CH2OH have convertible conformations (closed and open ring forms), so influence of pH conditions to their conversion was examined. Both compounds demonstrated closed rings under acidic conditions, and open rings under alkaline conditions. Generally, intracellar pH is kept at approximately neutral, and extracellular pH is kept at 0.6-0.7 units higher in all the animal species, so that our in vitro results supported in vivo findings.

Pharmacokinetics, Metabolism, and Excretion of the Intestinal Peptide Transporter 1 (SLC15A1)-Targeted Prodrug (1S,2S,5R,6S)-2-[(2′S)-(2-Amino)propionyl]aminobicyclo[3.1.0.]hexen-2,6-dicarboxylic acid (LY544344) in Rats and Dogs: Assessment of First-Pass Bioactivation and Dose Linearity

The peptidyl prodrug (1S,2S,5R,6S)-2-[(2'S)-(2-Amino)propionyl]a-minobicyclo[3.1.0.]hexen-2,6-dicarboxylic acid, also known as LY544344, was discovered to improve the oral bioavailability of the parent drug (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740), a potent group II metabotropic glutamate receptor agonist. This prodrug has been shown to deliver high plasma concentrations of the active drug via intestinal peptide transporter 1 (SLC15A1) (PepT1)-mediated intestinal transport and presystemic hydrolysis in preclinical species. The current data describe the pharmacokinetic behavior of LY544344 and LY354740, with a specific focus on the first-pass activation processes and dose linearity in rats and dogs. The PepT1 transporter makes an attractive prodrug target because of its high capacity and relatively broad substrate specificity. This was demonstrated by the wide dose proportionality observed in both species (up to 1000 mg/kg in rats and 140 mg/kg in dogs). After oral administration of LY544344, absorption and bioactivation were extensive and rapid, with greater than 97% of prodrug hydrolysis occurring before its appearance in the hepatic portal vein. Systemic activation was likewise extensive, with 100% conversion of a 7-mg/kg intravenous dose in dogs. Radiolabeled studies confirmed that hydrolysis to LY354740 was the only metabolic pathway and that the excretion pattern of the active drug was not altered by administration of the prodrug. These results demonstrate the nearly ideal prodrug properties of LY544344 and further validate the utility of the peptide transporter-directed approach to prodrug design.

Pharmacological and pharmacokinetic properties of a structurally novel, potent, and selective metabotropic glutamate 2/3 receptor agonist: in vitro characterization of agonist (-)-(1R,4S,5S,6S)-4-amino-2-sulfonylbicyclo[3.1.0]-hexane-4,6-dicarboxylic acid (LY404039)

Group II metabotropic glutamate (mGlu) receptor agonists, including (1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate monohydrate (LY354740) and (-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate (LY379268), have demonstrated efficacy in animal models of anxiety and schizophrenia, and LY354740 decreased anxiety in human subjects. Herein, we report the in vitro pharmacological profile and pharmacokinetic properties of another potent, selective, and structurally novel mGlu2/3 receptor agonist, (-)-(1R,4S,5S,6S)-4-amino-2-sulfonylbicyclo[3.1.0]hexane-4,6-dicarboxylic acid (LY404039) and provide comparisons with LY354740. Similar to LY354740, LY404039 is a nanomolar potent agonist at recombinant human mGlu2 and mGlu3 receptors (K(i) = 149 and 92, respectively) and in rat neurons expressing native mGlu2/3 receptors (Ki = 88). LY404039 is highly selective for mGlu2/3 receptors, showing more than 100-fold selectivity for these receptors, versus ionotropic glutamate receptors, glutamate transporters, and other receptors targeted by known anxiolytic and antipsychotic medications. Functionally, LY404039 potently inhibited forskolin-stimulated cAMP formation in cells expressing human mGlu2 and mGlu3 receptors. Electrophysiological studies indicated that LY404039 suppressed electrically evoked excitatory activity in the striatum, and serotonin-induced l-glutamate release in the prefrontal cortex; effects reversed by LY341495. These characteristics suggest LY404039 modulates glutamatergic activity in limbic and forebrain areas relevant to psychiatric disorders; and that, similar to LY354740, it works through a mechanism that may be devoid of negative side effects associated with current antipsychotics and anxiolytics. Interestingly, despite the slightly lower potency (approximately 2-5-fold) of LY404039 versus LY354740 in binding, functional, and electrophysiological assays, LY404039 demonstrated higher plasma exposure and better oral bioavailability in pharmacokinetic experiments. Collectively, the current data indicate that LY404039 may be valuable in the treatment of neuropsychiatric disorders, including anxiety and psychosis.

Tricyclic imidazoline derivatives as potent and selective adenosine A1 receptor antagonists

Novel tricyclic imidazoline antagonists of the adenosine A1 receptor are described. For key compounds, the selectivity level over other adenosine receptor subtypes is examined along with their in vivo effects in a rat diuresis model. Compound 14, the (R)-isomer of 7,8-dihydro-8-ethyl-2-(4-bicyclo[2.2.2]octan-1-ol)-4-propyl-1H-imidazo[2,1-i]purin-5(4H)-one, is a particularly potent adenosine A1 receptor antagonist with good selectivity over the other three adenosine receptor subtypes: A1 (human) Ki=22 nM; A2A (human) Ki=4400 nM; A2B (human) Ki=580 nM; A3 (human) Ki>or=10,000 nM. Imidazoline 14 is a competitive adenosine A1 receptor antagonist with a pA2 value of 8.88 and is highly soluble in water (>100 mg/mL). In addition, it has an oral bioavailability of 84% and an oral half-life of 3.8 h in rats. When orally administered in a rat diuresis model, compound 14 promoted sodium excretion (ED50=0.01 mg/kg). This level of efficacy is comparable to that of BG9928, a selective adenosine A1 receptor antagonist that is currently in clinical trials as a treatment for congestive heart failure. Additional modifications to 14 also showed that the bridgehead hydroxyl group could be replaced with a propionic acid (compound 36) without a significant loss in binding affinity or in vivo activity.

Highly constrained bicyclic VLA-4 antagonists

VLA-4 is implicated in several inflammatory and autoimmune disease states. A series of cyclic beta-amino acids (beta-aa) was studied as VLA-4 antagonists. Binding affinity was highly dependent on the dihedral angle (phi) between the amino and the carboxyl termini of the beta-aa. Compound 5 m where the beta-aa is embedded in a bicycle possesses the most preferred phi (120 degrees). It is a potent and bioavailable VLA-4 antagonist (VCAM-Ig alpha4beta1 IC50 = 54 nM, rat po F = 49%).

Hypericum perforatum: a 'modern' herbal antidepressant: pharmacokinetics of active ingredients

Hypericum perforatum (St John's Wort [SJW]) counts among the most favourite herbal drugs, and is the only herbal alternative to classic synthetic antidepressants in the therapy of mild to moderate depression. Several clinical studies have been conducted to verify the effectiveness of ethanolic or methanolic extracts of SJW. Alcoholic SJW extracts are a mixture of substances with widely varying physical and chemical properties and activities. Hyperforin, a phloroglucinol derivative, is the main source of pharmacological effects caused by the consumption of alcoholic extracts of SJW in the therapy of depression. However, several studies indicate that flavone derivatives, e.g. rutin, and also the naphthodianthrones hypericin and pseudohypericin, take part in the antidepressant efficacy. In contrast to the amount of documentation concerning clinical efficacy, oral bioavailability and pharmacokinetic data about the active components are rather scarce. The hyperforin plasma concentration in humans was investigated in a small number of studies. The results of these studies indicate a relevant plasma concentration, comparable with that used in in vitro tests. Furthermore, hyperforin is the only ingredient of H. perforatum that could be determined in the brain of rodents after oral administration of alcoholic extracts. The plasma concentrations of the hypericins were, compared with hyperforin, only one-tenth and, until now, the hypericins could not be found in the brain after oral administration of alcoholic H. perforatum extracts or pure hypericin. Until now, the pharmacokinetic profile of the flavonoids in humans after oral administration of an alcoholic H. perforatum extract has been investigated in only one study. More data are available for rutin and the aglycone quercetin after administration of pure substances or other flavonoid sources.

Multifunctional polymeric nanoparticles from diverse bioactive agents

We present a rational approach for assembling diverse bioactive agents, such as DNA, proteins, and drug molecules, into core-shell multifunctional polymeric nanoparticles (PNPs) that can be internalized in human breast cancer cells. Using ring-opening metathesis polymerization (ROMP), block copolymers containing small-molecule drug segments (>50% w/w) and tosylated hexaethylene glycol segments were prepared and assembled into PNPs that allowed for the surface conjugation of single-stranded DNA sequences and/or tumor-targeting antibodies. The resulting antibody-functionalized particles were readily uptaken by breast cancer cells that overexpressed the corresponding antigens.

Synthesis, in vitro pharmacology, and structure–activity relationships of 2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid derivatives as mGluR2 antagonists

Chemical modification of the bicyclo[3.1.0]hexane ring C-3 position led to the discovery of 3-alkoxy-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid, 3-benzylthio-, and 3-benzylamino-2-amino-6-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid derivatives, metabotropic glutamate receptor 2 (mGluR2) antagonists. In particular, 3-(3,4-dichlorobenzyloxy)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (15ae), (1R,2S,5R,6R)-2-amino-3-(3,4-dichlorobenzylthio)-6-fluorobicyclo[3.1.0]hexane-2,6-carboxylic acid (15at), and (1R,2S,5R,6R)-2-amino-3-(N-(3,4-dichlorobenzylamino))-6-fluorobicyclo[3.1.0]hexane-2,6-carboxylic (15ba) showed high affinity for the mGluR2 receptor (15ae: K(i) = 2.51 nM, 15at: K(i) = 1.96 nM, and 15ba: K(i) = 3.29 nM) and potent antagonist activity for mGluR2 (15ae; IC50 = 34.21 nM, 15at; IC50 = 13.34 nM, and 15ba; IC50 = 35.96 nM). No significant agonist activity for mGluR2 was observed with 15ae, 15at, or 15ba. This paper reports on the synthesis, in vitro pharmacological profile, and structure-activity relationships (SARs) of 3-substituted-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid.

Effect of physicochemical properties of cyclic terpenes on their ex vivo skin absorption and elimination kinetics

BACKGROUND

The terpenes disturb lipid arrangement in the intercellular region of the stratum corneum (SC) that leads to the increased permeability of the skin. This effect is used in technology of transdermal drug forms and depends on physicochemical properties of terpenes and their amounts penetrated to the stratum corneum; however terpenes do not need penetrate into viable skin tissue and this event is not even desired.

OBJECTIVE

To correlate skin absorption and elimination kinetics of four cyclic terpenes, namely alpha-pinene, beta-pinene, eucalyptol and terpinen-4-ol, applied as neat substance with their physicochemical properties.

METHODS

The terpenes were applied onto the human skin in vitro, and after 1-4 h their content in the separated by a tape-stripping method stratum corneum layers and in the epidermis/dermis was determined using GC. Similarly, the amounts of terpenes in the skin were analysed during 4 h following 1 h absorption.

RESULTS

The fastest and progressive penetration into all skin layers was observed for terpinen-4-ol. All studied terpenes are absorbed in the viable epidermis/dermis, however penetration into this layers is time-dependent process, constantly increasing during 4 h. Like for stratum corneum, the largest cumulation in epidermis/dermis was observed for terpinen-4-ol. The elimination of terpenes from the stratum corneum was fast, especially in deeper layers, and much faster if the initial cumulation was small.

CONCLUSION

Investigated cyclic terpenes represent different penetration and elimination characteristics and do not permeate across the skin to the acceptor medium due to large cumulation in the skin tissue. The penetration of terpenes into stratum corneum is greater if their log P-value is close to 3.

St. John's wort (Hypericum perforatum) and breastfeeding: plasma and breast milk concentrations of hyperforin for 5 mothers and 2 infants

BACKGROUND

Herbal preparations for depression, such as St. John's wort, are often preferred over pharmaceutical preparations by mothers and midwives after childbirth because these preparations are available to patients as over-the-counter "natural" treatments and are popularly assumed to be safe. The only existing report on St. John's wort excretion into human milk showed that only 1 active component (hyperforin) was detectable in breast milk, but was not detectable in the infants' plasma. Another report found more cases of minor problems in infants breast-fed by women taking St. John's wort. However, significance was reached only in comparison with disease-matched women (p<.01), not healthy controls (p=.20).

METHOD

Five mothers who were taking 300 mg of St. John's wort 3 times daily (LI 160 [Jarsin], Lichtwer Pharma GmbH; Berlin, Germany) and their breastfed infants were assessed. Thirty-six breast milk samples (foremilk and hindmilk collected during an 18-hour period) and 5 mothers' and 2 infants' plasma samples were analyzed for hyperforin levels by tandem mass spectrometry (LC/MS/MS; limit of quantification=0.1 ng/mL). Data were gathered from January 2001 to February 2002.

RESULTS

Hyperforin is excreted into breast milk at low levels. However, the compound was at the limit of quantification in the 2 infants' plasma samples (0.1 ng/mL). Milk/plasma ratios ranged from 0.04 to 0.13. The relative infant doses of 0.9% to 2.5% indicate that infant exposure to hyperforin through milk is comparable to levels reported in most studies assessing anti-depressants or neuroleptics. No side effects were seen in the mothers or infants.

CONCLUSION

These results add to the evidence of the relative safety of St. John's wort while breast-feeding found in previous observational studies.

Investigation of pharmacokinetic data of hypericin, pseudohypericin, hyperforin and the flavonoids quercetin and isorhamnetin revealed from single and multiple oral dose studies with a hypericum extract containing tablet in healthy male volunteers

Hypericins, hyperforin and flavonoids are discussed as the main components contributing to the antidepressant action of St. John's wort (Hypericum perforatum). Therefore, the objective of the two open phase I clinical trials was to obtain pharmacokinetic data of these constituents from a hypericum extract containing tablet: hypericin, pseudohypericin, hyperforin, the flavonoid aglycone quercetin, and its methylated form isorhamnetin. Each trial included 18 healthy male volunteers who received the test preparation, containing 900 mg dry extract of St John's wort (STW 3-VI, Laif 900), either as a single oral dose or as a multiple once daily dose over a period of 14 days. Concentration/time curves were determined for the five constituents, for 48 h after single dosing and for 24 h on day 14 at the end of 2 weeks of continuous daily dosing. After single dose intake, the key pharmacokinetic parameters were determined as follows: Hypericin: Area under the curve (AUC(0-infinity)) = 78.33 h x ng/ml, maximum plasma concentration (Cmax) = 3.8 ng/ml, time to reach Cmax (tmax) = 7.9 h, and elimination half-life (t1/2) = 18.71 h; pseudohypericin: AUC(0-infinity) = 97.28 h x ng/ml, Cmax = 10.2 ng/ml, tmax = 2.7 h, t1/2 = 17.19 h; hyperforin: AUC(0-infinity) = 1550.4 h x ng/ml, Cmax = 122.0 ng/ml, tmax = 4.5 h, t1/2 = 17.47 h. Quercetin and isorhamnetin showed two peaks of maximum plasma concentration separated by about 3-3.5 h. Quercetin: AUC(0-infinity) = 417.38 h x ng/ml, Cmax (1) = 89.5 ng/ml, tmax (1) = 1.0 h, Cma (2) = 79.1 ng/ml, tmax (2) = 4.4 h, t1/2 = 2.6 h; isorhamnetin: AUC(0-infinity) = 155.72 h x ng/ml, Cmax (1) = 12.5 ng/ml, tmax (1) = 1.4 h, Cmax (2) = 14.6 ng/ml, tmax (2) = 4.5 h, t1/2 = 5.61 h. Under steady state conditions reached during multiple dose administration similar results were obtained. Further pharmacokinetic characteristics calculated from the obtained data were the mean residence time (MRT), the lag-time, the peak-trough fluctuation (PTF), the lowest observed plasma concentration (Cmin), and the average plasma concentration (Cav). The data obtained for the five consitituents generally corresponded well with values previously published. The trial preparation was well tolerated.

Pharmacological Characterization of (E)-N-(4-Fluorobut-2-enyl)-2β-carbomethoxy-3β-(4′-tolyl)nortropane (LBT-999) as a Highly Promising Fluorinated Ligand for the Dopamine Transporter

In the aim to develop an efficient fluorinated probe for positron emission tomography (PET) exploration of the dopamine transporter (DAT), we studied several in vitro and in vivo characteristics of the phenyltropane derivative (E)-N-(4-fluorobut-2-enyl)-2beta-carbomethoxy-3beta-(4'-tolyl)nortropane (LBT-999). In vitro on rat striatal membrane, [(3)H]LBT-999 bound to a single site with a K(d) of 9 nM, B(max) of 17 pmol/mg protein, and a very high selectivity for the DAT [IC(50) for 1-{2-[bis-(4-fluorophenyl)-methoxy]ethyl}-4-(3-phenylpropyl)piperazine (GBR 12909) and (E)-N-(3-iodoprop-2-enyl)-2beta-carbomethoxy-3beta-(4'-methylphenyl)nortropane (PE2I): 2.4 and 18 nM, respectively; IC(50) for paroxetine, citalopram, N,N-dimethyl-2-(2-amino-4-methylphenyl thio)benzylamine, nisoxetine, and desipramine >1 muM]. In vitro on post-mortem human brain sections, LBT-999 bound with high intensity to the caudate-putamen, weakly to the thalamus, and not in the neocortex and cerebellum. This binding was totally abolished in the presence of PE2I. Ex vivo cerebral biodistribution of [(11)C]LBT-999 in rats showed striatum/cerebellum radioactivity ratios of 18 and 25 at 30 and 60 min postinjection, respectively. This accumulation was strongly prevented by preinjection of GBR 12909, whereas paroxetine and nisoxetine had no effect. An in vivo kinetic PET study in three baboons showed a fast and very high uptake in the striatum, with a plateau at 30 min postinjection and a maximal putamen/cerebellum ratio of 30. Taken together, these findings demonstrate that LBT-999 is a highly promising agent for in vivo exploration of the DAT. This probe is currently labeled with (18)F for further characterizations.

IN VITRO AND IN VIVO EVALUATION OF THE METABOLISM AND BIOAVAILABILITY OF ESTER PRODRUGS OF MGS0039 (3-(3,4-DICHLOROBENZYLOXY)-2-AMINO-6-FLUOROBICYCLO[3.1.0]HEXANE-2,6-DICARBOXYLIC ACID), A POTENT METABOTROPIC GLUTAMATE RECEPTOR ANTAGONIST

MGS0039 (3-(3,4-dichlorobenzyloxy)-2-amino-6-fluorobicyclo-[3.1.0]hexane-2,6-dicarboxylic acid) has been identified as a potent and selective antagonist for metabotropic glutamate receptors. However, the oral bioavailability of MGS0039 is 10.9% in rats, due to low absorption. Several prodrugs, synthesized to improve absorption, exhibited 40 to 70% bioavailability in rats. This study investigated in vitro metabolism using liver S9 fractions from both cynomolgus monkeys and humans and oral bioavailability in cynomolgus monkeys to select the prodrug most likely to exhibit optimal pharmacokinetic profiles in humans. In monkeys, transformation to active substance was observed (5.9-72.8%) in liver S9 fractions, and n-butyl, n-pentyl, 3-methylbutyl, and 4-methylpentyl ester prodrugs exhibited high transformation ratios (>64%). Cmax levels and F values after oral dosing increased to 4.1- to 6.3-fold and 2.4- to 6.3-fold, respectively, and a close relationship between transformation ratios and Cmax and F values was observed, indicating that the hydrolysis rate in liver S9 fractions is the key factor in determining oral bioavailability in monkeys. In humans, n-hexyl, n-heptyl, n-octyl, 5-methylbutyl, and 6-methylpentyl ester prodrugs exhibited high transformation ratios (>65%) in liver S9 fractions. With these prodrugs, n-hexyl, n-heptyl, and 5-methylpentyl ester, almost complete recovery (96-99%) was obtained. Given the transformation ratio, we anticipated that the n-heptyl alkyl ester prodrug would exhibit the highest oral bioavailability of active substances in humans, if the hydrolysis rate in liver S9 fractions is indeed the key factor in determining oral bioavailability in humans. On this basis, MGS0210 (3-(3,4-dichlorobenzyloxy)-2-amino-6-fluorobicyclo[3.1.0]hexane-2,6-dicarboxylic acid n-heptyl ester) seems to be a promising candidate among MGS0039 prodrugs.

Improved Bioavailability of the mGlu2/3 Receptor Agonist LY354740 Using a Prodrug Strategy: In Vivo Pharmacology of LY544344

Numerous studies have indicated that selective agonists of group II metabotropic glutamate (mGlu) receptors, such as LY354740 [(1S,2S,5R,6S)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylate monohydrate] and LY379268 [(-)-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate], may be useful in the treatment of many psychiatric disorders, including psychosis, anxiety, and drug withdrawal. Although animal and human studies demonstrate potential therapeutic utility, poor oral bioavailability is a limiting factor in the clinical development of these compounds. Therefore, a novel prodrug approach is being pursued to increase exposure levels of active compound after oral administration. Here, we demonstrate a 10-fold increase in brain, plasma, and cerebrospinal fluid levels of LY354740 after oral prodrug administration. Furthermore, we compare the oral efficacy of the mGlu2/3 receptor agonist LY354740 and its prodrug LY544344 [(1S,2S,5R,6S)-2-[(2'S)-(2'-amino)propionyl]aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid hydrochloride] in rodent models of psychosis and anxiety. Phencyclidine (PCP)-induced hyperlocomotion was dose dependently inhibited in rats receiving oral administration of 30 or 100 mg/kg LY544344, whereas LY354740 did not significantly reverse PCP-mediated behaviors at doses up to 100 mg/kg. Orally administered LY544344 (30 mg/kg) and subcutaneously administered LY354740 (10 mg/kg) attenuated stress-induced hyperthermia in DBA/2 mice, with the prodrug producing anxiolytic effects at lower oral doses than the parent compound. Although oral administration of LY354740 did not significantly affect fear-induced suppression of operant responding in rats, subcutaneously administered LY354740 (10 or 20 mg/kg) and orally administered LY544344 (10 or 30 mg/kg) produced significant anxiolytic effects in this model. The present data confirm that mGlu2/3 receptor agonists produce antipsychotic and anxiolytic effects in animal behavioral models and demonstrate that oral bioavailability of LY354740 was substantially increased using a prodrug strategy.

Dipeptides as effective prodrugs of the unnatural amino acid (+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (LY354740), a selective group II metabotropic glutamate receptor agonist

(+)-2-Aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid (1), also known as LY354740, is a highly potent and selective agonist for group II metabotropic glutamate receptors (mGlu receptors 2 and 3) tested in clinical trials. It has been shown to block anxiety in the fear-potentiated startle model. Its relatively low bioavailability in different animal species drove the need for an effective prodrug form that would produce a therapeutic response at lower doses for the treatment of anxiety disorders. We have investigated the increase of intestinal absorption of this compound by targeting the human peptide transporter hPepT1 for active transport of di- and tripeptides derived from 1. We have found that oral administration of an N dipeptide derivative of 1 (12a) in rats shows up to an 8-fold increase in drug absorption and a 300-fold increase in potency in the fear-potentiated startle model in rats when compared with the parent drug 1.

METABOLISM AND DISPOSITION OF A POTENT GROUP II METABOTROPIC GLUTAMATE RECEPTOR AGONIST, IN RATS, DOGS, AND MONKEYS

Metabolism and disposition of MGS0028 [(1R,2S,5S,6S)-2-amino-6-fluoro-4-oxobicyclo[3.1.0]hexane-2,6-dicarboxylic acid monohydrate], a potent group II metabotropic glutamate receptor agonist, were examined in three preclinical species (Sprague-Dawley rats, beagle dogs, and rhesus monkeys). In rats, MGS0028 was widely distributed and primarily excreted in urine as parent and as a single reductive metabolite, identified as the 4R-isomer MGS0034 [(1R,2S,4R,5S,6S)-2-amino-6-fluoro-4-hydroxybicyclo[3.1.0]-hexane-2,6-dicarboxylic acid]. MGS0028 had a low brain to plasma ratio at efficacious doses in rats and was eliminated more slowly in rat brain than in plasma. Exposure increased proportionally (1--10 mg/kg p.o.) in rats, with bioavailability>60% at all doses. However, bioavailability was only approximately 20% in monkeys, and MGS0034 was found in relatively high abundance in plasma. In dogs, oral bioavailability was >60%, and the metabolite was not detected. In vitro metabolism was examined in liver subcellular fractions (microsomes and cytosol) from rat, dog, monkey, and human. Reductive metabolism was observed in rat, monkey, and human liver cytosol incubations, but not in dog liver cytosol incubations. No metabolism of MGS0028 was detected in incubations with liver microsomes from any species. Similar to in vivo results, MGS0028 was reduced in cytosol stereospecifically to MGS0034. The rank order of in vitro metabolite formation (monkey >> rat approximately human >> dog) was in agreement with in vivo observations in rats, dogs, and monkeys. Based on the observation of species difference in reductive metabolism, rat and monkey were recommended to be the preclinical species for further characterization prior to testing in humans. Finally, allometric scaling predicts that human pharmacokinetic parameters would be acceptable for further development.

High-performance liquid chromatography measurement of hyperforin and its reduced derivatives in rodent plasma

A reverse-phase high-performance liquid chromatography method was developed for the determination of hyperforin and its reduced derivatives octahydrohyperforin and tetrahydrohyperforin in rodent plasma. The procedure includes solid-phase extraction from plasma using the Baker 3cc C8 cartridge, resolution on the Symmetry Shield RP8 column (150 mm x 4.6 mm, i.d. 3.5 microm) and UV absorbance detection at 300 nm. The assay was linear over a wide range, with an overall coefficient of variation less than 10% for all compounds. The precision and accuracy were within acceptable limits and the limit of quantitation was sufficient for studies preliminarily assessing the disposition of tetrahydrohyperforin and octahydrohyperforin in the mouse and rat.

Effects of the mGluR2/3 agonist LY354740 on computerized tasks of attention and working memory in marmoset monkeys

RATIONALE

LY354740 is a recently developed metabotropic glutamatergic receptor 2 and 3 (mGluR2/3) agonist. A high density of mGluR2 has been reported in terminal fields of the perforant path in rodents and humans, suggesting its involvement in cognitive functions mediated by the temporal lobe, including memory. A small number of in vivo studies in rodents have assessed the effects of LY354740 on memory tasks, reporting the induction of impaired memory for spatial orientation in a water maze task and for delayed match and non-match to position in an operant version of these tasks.

OBJECTIVE

In the present primate study, we used radioautography to describe the distribution and intensity of (3)H-LY354740 binding in the hippocampal formation of the common marmoset monkey (Callithrix jacchus) relative to the rat. In the major, in vivo part of the study, the effects of systemic LY354740 on computerized tasks of attention and memory were investigated.

METHODS

Adult common marmosets were trained to perform a five-choice serial reaction time (5-CSRT) task and a concurrent delayed match-to-position (CDMP) task from the Cambridge Neuropsychological Automated test Battery (CANTAB). Filter tests of LY354740 effects on motor dexterity and motivation for reward revealed high inter-individual variation in sensitivity; therefore, on the 5-CSRT, subjects were tested at a dose range of 3--10 mg/kg, and on the CDMP, subjects were tested at 1--3 or 3--10 mg/kg.

RESULTS

Radioautography revealed a relatively low level of (3)H-LY354740 binding in the marmoset hippocampal formation compared to the rat. Despite low binding, LY354740 reduced sustained-attention accuracy in the 5-CSRT, and reduced accuracy in two stages of the CDMP.

CONCLUSIONS

The current study provides novel evidence for the importance of mGluR2/3 in the regulation of primate cognitive functioning.

Investigation of the bioavailability of hypericin, pseudohypericin, hyperforin and the flavonoids quercetin and isorhamnetin following single and multiple oral dosing of a hypericum extract containing tablet

The objective of these two open phase I clinical trials was the investigation of the bioavailability of five constituents from a hypericum extract containing tablet, which are discussed as the components contributing to the antidepressant action. Each trial included 18 healthy male volunteers who received the test preparation, containing 612 mg dry extract of St John's wort (STW-3, Laif 600), either as a single oral dose or as a multiple once daily dose over a period of 14 days. Concentration/time curves were determined for hypericin, pseudohypericin, hyperforin, the flavonoid aglycone quercetin, and its methylated form isorhamnetin for 48 h after single dosing and for 24 h on day 14 at the end of 2 weeks of continuous daily dosing. After single dose intake, the key pharmacokinetic parameters were determined as follows: hypericin: area under the curve (AUC(0-infinity)) = 75.96 h x ng/ml, maximum plasma concentration (Cmax) = 3.14 ng/ml, time to reach Cmax (t(max)) = 8.1 h, and elimination half-life (t1/2) = 23.76 h; pseudohypericin: AUC(0-infinity) = 93.03 h x ng/ml, Cmax = 8.50 ng/ml, t(max) = 3.0 h, t1/2 = 25.39 h; hyperforin: AUC(0-max) = 1009.0 h x ng/ml, Cmax = 83.5 nglml, t(max) = 4.4 h, t1/2 = 19.64 h. Quercetin and isohamnetin showed two peaks of maximum plasma concentration separated by about 4 h. Quercetin: AUC(0-infinity) = 318,7 h x ng/ml, Cmax (1) = 47.7 ng/ml, t(max) (1) = 1.17 h, Cmax (2) = 43.8 ng/ml, t(max) (2) = 5.47 h, t1/2 = 4.16 h; isorhamnetin: AUC(0-infinity) = 98.0 h x ng/ml, Cmax (1) = 7.6 ng/ml, t(max) (1) = 1.53 h, Cmax (2) = 9.0 ng/ml, t(max), (2) = 6.42 h, t1/2 = 4.45 h. Under steady state conditions reached during multiple dose administration similar results were obtained. Further pharmacokinetic characteristics calculated from the obtained data were the mean residence time (MRT), the lag-time, the peak-trough fluctuation (PTF), the lowest observed plasma concentration (Cmin), and the average plasma concentration (Cav). The data obtained for hypericin, pseudohypericin and hyperforin generally corresponded well with values previously published, with some deviations observed for the extent of absorption of hypericin and the time course of absorption and elimination of hyperforin. The kinetic characteristics of the hypericum flavonoids are reported here for the first time. The trial preparation was well tolerated.

In vitro and in vivo activities of novel 6-methylidene penems as beta-lactamase inhibitors

Novel penem molecules with heterocycle substitutions at the 6 position via a methylidene linkage were investigated for their activities and efficacy as beta-lactamase inhibitors. The concentrations of these molecules that resulted in 50% inhibition of enzyme activity were 0.4 to 3.1 nM for the TEM-1 enzyme, 7.8 to 72 nM for Imi-1, 1.5 to 4.8 nM for AmpC, and 14 to 260 nM for a CcrA metalloenzyme. All the inhibitors were more stable than imipenem against hydrolysis by hog and human dehydropeptidases. Piperacillin was combined with a constant 4-microg/ml concentration of each inhibitor for MIC determinations. The combinations reduced piperacillin MICs by 2- to 32-fold for extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli and Klebsiella pneumoniae strains. The MICs for piperacillin-resistant (MIC of piperacillin, >64 microg/ml) strains of Enterobacter spp., Citrobacter spp., and Serratia spp. were reduced to the level of susceptibility (MIC of piperacillin, < or =16 microg/ml) when the drug was combined with 4, 2, or 1 microg of these penem inhibitors/ml. Protection against acute lethal bacterial infections with class A and C beta-lactamase- and ESBL-producing organisms in mice was also demonstrated with piperacillin plus inhibitor. Median effective doses were reduced by approximately two- to eightfold compared to those of piperacillin alone when the drug was combined with the various inhibitors at a 4:1 ratio. Pharmacokinetic analysis after intravenous administration of the various inhibitors showed mean residence times of 0.1 to 0.5 h, clearance rates of 15 to 81 ml/min/kg, and volumes of distribution between 0.4 and 2.5 liters/kg. The novel methylidene penem molecules inhibit both class A and class C enzymes and warrant further investigation for potential as therapeutic agents when used in combination with a beta-lactam antibiotic.

Multidrug resistance protein 4 (MRP4/ABCC4) mediates efflux of bimane-glutathione

Multidrug resistance proteins (MRPs) are ATP-dependent export pumps that mediate the export of organic anions. ABCC1 (MRP1), ABCC2 (MRP2) and ABCC3 (MRP3) are all able to facilitate the efflux of anionic conjugates including glutathione (GSH), glucuronide and sulfate conjugates of xenobiotics and endogenous molecules. Earlier studies showed that ABCC4 functions as an ATP-driven export pump for cyclic AMP and cyclic GMP, as well as estradiol-17-beta-D-glucuronide. However, it was unclear if other conjugated metabolites can be transported by ABCC4. Hence in this study, a fluorescent substrate, bimane-glutathione (bimane-GS) was used to further examine the transport activity of ABCC4. Using cells stably overexpressing ABCC4, this study shows that ABCC4 can facilitate the efflux of the glutathione conjugate, bimane-glutathione. Bimane-glutathione efflux increased with time and >85% of the conjugate was exported after 15min. This transport was abolished in the presence of 2.5microM carbonylcyanide m-chlorophenylhydrasone (CCCP), an uncoupler of oxidative phosphorylation. Inhibition was also observed with known inhibitors of MRP transporters including benzbromarone, verapamil and indomethacin. In addition, 100microM methotrexate, an ABCC4 substrate or 100microM 6-thioguanine (6-TG), a compound whose monophosphate metabolite is an ABCC4 substrate, reduced efflux by >40%. A concentration-dependent inhibition of bimane-glutathione efflux was observed with 1-chloro-2,4-dinitrobenzene (CDNB) which is metabolized intracellularly to the glutathione conjugate, 2,4-dinitrophenyl-glutathione (DNP-GS). The determination that ABCC4 can mediate the transport of glucuronide and glutathione conjugates indicates that ABCC4 may play a role in the cellular extrusion of Phase II detoxification metabolites.

Chelerythrine stimulates GSH transport by rat Mrp2 (Abcc2) expressed in canine kidney cells

Rat multidrug resistant protein 2 (Mrp2; Abcc2), an ATP-driven pump located on the canalicular domain of hepatocytes, exports glutathione S-conjugates (GS-X) and GSH among its wide variety of substrates. Previous studies have shown that chelerythrine (CHEL), a quaternary benzophenanthridine cation, reacts with GSH to form a reversible adduct under physiological conditions. Here we report that CHEL can strongly stimulate GSH efflux by Mrp2, when it is constitutively expressed in polarized canine kidney cells, thereby leading to the depletion of cellular GSH. Transepithelial transport experiments indicate that Mrp2 transports GSH and CHEL with a 1:1 stoichiometry, which can be readily inhibited by GS-bimane, a GS-X substrate for Mrp2. Moreover, CHEL can block Mrp2-mediated leukotriene C4 uptake by membrane vesicles with an IC50 approximately 100 microM in the presence of GSH, but not S-methyl GSH or ophthalmic acid. Thus the thiol group of GSH is required for inhibition of Mrp2 in the presence of CHEL. Our results suggest that CHEL stimulates GSH efflux by forming a reversible GS-CHEL adduct, which is transported by Mrp2 and dissociates extracellularly.

Radiolabeling and biodistribution of methyl 2-(methoxycarbonyl)-2-(methylamino) bicyclo[2.1.1] -hexane -5-carboxylate, a potential neuroprotective drug

Methyl 2-(methoxycarbonyl) -2-(methylamino) bicyclo[2.1.1] -hexane -5-carboxylate (MMMHC) is developed as a potential neuroprotective drug. It was labeled with C-11 from the desmethyl precursor methyl 2-(methoxycarbonyl)-2-amino bicyclo[2.1.1]-hexane-5-carboxylate with [11C]methyl triflate in acetone solution at 60 degrees C with labeling yield of 69% and with radiochemical purity of >99%. Positron Emission Tomography (PET) studies in a normal rat showed that Methyl 2-(methoxycarbonyl)-2-([11C]methylamino)bicyclo[2.1.1]-hexane-5-carboxylate ([11C] MMMHC) accumulated mainly in the cortical brain areas after iv administration. Frontal cortex/cerebellum ratios in a rat brain were 8.0/6.0, 6.8/4.2, 6.3/4.3, 5.5/4.2 and 5.2/4.5 percent of the injected dose in 100 ml at 2 min, 5 min, 10 min, 20 min and 40 min respectively after i.v. injection. During 20-40 min, 2.9+/-0.4% of the total activity stayed in the brain. These results showed that MMMHC could be labeled with C-11 with high yield, and it passed the brain-blood barrier and accumulated in several brain regions.

Metallothionein induction related to hepatic structural perturbations and antioxidative defences in roach (Rutilus rutilus) exposed to the fungicide procymidone

A variety of stresses, hormones, glucocorticoids and cytokines are known to induce metallothioneins (MTs) in animals. The aim of this study was to investigate the effects of chemical stress induced by the dicarboximide fungicide procymidone on hepatic structure, MT content and antioxidative defences (catalase and glutathione reductase activities and glutathione content) in the common fish Rutilus rutilus. Catalase and glutathione reductase activities remained stable throughout the experiment. Four days of exposure to 0.2 or 0.4 mg l(-1) of procymidone induced an obvious increase in liver MT content, perturbation of metal MT contents, and an increase in hepatic glutathione content. After 14 days' exposure, obvious and large structural alterations of the hepatic parenchyma occurred simultaneously with a decrease in MT and glutathione content. These events were interpreted as degeneration of the liver. Fish exposed for 14 days to procymidone and then placed for 14 days in clean water showed nearly complete decontamination of the liver, but MT concentrations remained high. The toxicological significance of these events is discussed.

LY-354740 (Eli Lilly)

Lilly is developing LY-354740, the lead compound in a series of derivatives of the metabotropic glutamate receptor group II agonist L-CCG-1, for the potential treatment of anxiety [212536], [276941], [276942].

Bridged bicyclic vasopressin receptor antagonists with V(2)-selective or dual V(1a)/V(2) activity

The synthesis and biological testing of a novel series of nonpeptide vasopressin receptor antagonists, containing a bridged bicyclic nucleus, are reported. Variation of substituents (R(1)-R(3)) in general formula 3, and the configuration of the stereocenter, resulted in potent V(2)-selective (e.g., 5) and balanced dual V(1a)/V(2) (e.g., 10) compounds. Data from receptor binding, cell-based functional, and in vivo assays are presented [corrected]

Non-covalent thrombin inhibitors featuring P3-Heterocycles with P1-Bicyclic arginine surrogates

Novel, potent, and highly selective classes of thrombin inhibitors were identified, which resulted from judicious combination of P4-aromatics and P2-P3-heterocyclic dipeptide surrogates with weakly basic (calcd pKa approximately non-basic-8.6) bicyclic P1-arginine mimics. The design, synthesis, and biological activity of achiral, non-covalent, orally bioavailable inhibitors NC1-NC44 featuring P1-indazoles, benzimidazoles, indoles, benzotriazoles, and aminobenzisoxazoles is disclosed.

AH-1058: a novel cardioselective Ca2+ channel blocker

The pharmacologic profile of a cyproheptadine-related compound, 4-(5H-dibenzo[a,d]cyclohepten-5-ylidene)-1-[(E)-3-(3-methoxy-2-nitro)phenyl-2-propenyl]piperidine hydrochloride (AH-1058), was assessed in various in vivo and in vitro models. In guinea pig cardiomyocytes, AH-1058 effectively suppressed L-type Ca2+ channel currents without affecting other ion channel or ion exchange currents. In rat cerebral cortical membranes AH-1058 appears to bind preferentially to L-type Ca2+ channels at phenylalkylamine- and benzothiazepine-binding sites. In canine isolated, blood-perfused heart preparations, AH-1058 exerted negative inotropic, dromotropic, and chronotropic and weak coronary vasodilator effects. In halothane-anesthetized dogs, AH-1058 suppressed ventricular contractility and decreased blood pressure and cardiac output. Total peripheral vascular resistance was hardly affected by the drug, suggesting that in vivo AH-1058 can selectively suppress cardiac, as compared to peripheral vascular, function. In conscious dogs, by intravenous administration AH-1058 reduced systolic blood pressure and maximal upstroke velocity of the left ventricular pressure, while it increased heart rate in a dose-dependent manner. The drug did not affect diastolic blood pressure, which is quite different from cardiovascular properties of well-known Ca2+ channel blockers, verapamil and diltiazem. This unique cardiovascular profile of AH-1058 is expected to be useful in the treatment of certain pathological processes such as the obstructive hypertrophic cardiomyopathy, vasovagal syncope, dissecting aortic aneurysm, and ventricular arrhythmias, in which selective inhibition of the ventricular Ca2+ channels is essential for drug therapy.

The disposition, metabolism, and pharmacokinetics of a selective metabotropic glutamate receptor agonist in rats and dogs

Compound LY354740 [(+)-2-aminobicyclo[3.1.0]hexane-2,6-dicarboxylic acid], an analog of glutamic acid, is a selective group 2 metabotropic glutamate receptor agonist in clinical development for the treatment of anxiety. Studies have been conducted to characterize the absorption, disposition, metabolism, and excretion of LY354740 in rats and dogs after intravenous bolus or oral administration. Plasma concentrations of LY354740 were measured using a validated gas chromatography/mass spectrometry assay. In rats, LY354740 demonstrated linear pharmacokinetics after oral administration from 30 to 1000 mg/kg. The oral bioavailability of LY354740 was approximately 10% in rats and 45% in dogs. In the dog, food decreased the mean area under the plasma concentration-time curve value by approximately 34%, hence, decreasing the oral bioavailability of the compound. Excretion studies in both rats and dogs indicate that the absorbed drug is primarily eliminated via renal excretion. In addition, tissue distribution in rats showed that the highest levels of radioactivity were in the kidney and gastrointestinal tract, which is consistent with the excretion studies. Metabolism of LY354740 was evaluated in vitro using rat and dog liver microsomes and rat liver slices. In addition, urine and fecal samples from rat and dog excretion studies were profiled using HPLC with radio-detection. These evaluations indicated that neither rats nor dogs metabolized LY354740. In summary, LY354740 is poorly absorbed in rats, moderately absorbed in dogs, and rapidly excreted as unchanged drug in the urine.

Species differences in beta-oxidative metabolism of a thromboxane A2-receptor antagonist [(+)-S-145] in rat, dog and monkey

1. The formation of beta-oxidized metabolites from (+)-S-145 [(+)-(Z)-7-[(1R, 2S, 3S, 4S)-3-(benzenesulphonamide)bicyclo-[2.2.]-hept-2-yl]-5-heptenoic acid] by liver homogenates were compared between rat, dog and monkey. Species differences were found in hepatic beta-oxidation capacities. The results agree with the qualitative and quantitative differences in beta-oxidized metabolite proportions among these species observed in vivo. 2. The activities of microsomal (+)-S-145-CoA synthesis, the initial step of the beta-oxidation, were determined. Species differences in their intrinsic clearances primarily agreed with those of the beta-oxidized metabolite formation. 3. (+)-S-145-CoA oxidation activities towards (+)-S-145-CoA by liver homogenates were much higher than the beta-oxidized metabolite formation in all species, indicating that formed (+)-S-145-CoA was immediately beta-oxidized in peroxisomes. The species differences were inconsistent with those of beta-oxidized metabolite formation in vitro. 4. Therefore, quantitative differences of hepatic (+)-S-145 beta-oxidation capacity in rat, dog and monkey were considered to be mainly due to the species difference in (+)-S-145-CoA formation.

Residue levels, decline curves, and plantation distribution of procymidone in green beans grown in greenhouse

Residue levels and degradation rates of procymidone residues were studied in green beans grown in a greenhouse. Experiments were planned to also assess the influence of planting density on the behavior of procymidone residues on this type of crop. The study was carried out in four random blocks considering three sub-blocks of different planting densities into each block. Plants were sprayed with Sumisclex 50 WP (1077.5 g of ai/ha) 52 days after the transplantation, and sampling was carried out daily during two different periods of 6 and 5 consecutive days, respectively, around the two harvest days (days 12 and 28 after the treatment). Residue levels of procymidone were determined by using the Luke extraction method and GC-NPD. The average residue levels of procymidone in the overall planting (mean of 12 determinations) were below 2 mg/kg (European maximum residue limit) for all the sampling days, obtaining values of 1.01 +/- 0.55 and 0.37 +/- 0.10 mg/kg, respectively, at the two harvest days. The decline behavior of procymidone residues in the overall plantation and in each block could be described as a pseudo-first-order reaction, obtaining half-life values (t(1/2)) of 10-11 days in all cases. The calculated residue level at the preharvest time (5 days) in the overall plantation was 1.7 mg/kg, but this value in the blocks depended on the block position along the greenhouse and ranged from 2.3 to 0.9 mg/kg. In this work, additional data on the residual behavior of the fungicide pyrazophos in green beans were also obtained.

Synthesis and biological activity of the metabolites of N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-2-nitroaniline fumarate (SK-946)

Three metabolites of N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-2-nitroaniline fumarate (SK-946), a novel central muscarinic cholinergic receptor agonist, were prepared to confirm their proposed structures, and tested for muscarinic receptor affinity in vitro.

Transfected rat cMOAT is functionally expressed on the apical membrane in Madin-Darby canine kidney (MDCK) cells

PURPOSE

The purpose of the present study is to investigate the expression of canalicular multispecific organic anion transporter (cMOAT) by its cDNA transfection in polarized Madin-Darby canine kidney cells (MDCK).

METHODS

MDCK cells were transfected with an expression vector (pCXN2) containing the rat cMOAT cDNA with lipofectamine to obtain the stable transfectant under G418. Cells from a single colony whose cMOAT expression was the highest were seeded to form a tight epithelial monolayer on microporous membrane filters. Export of glutathione S-bimane (GS-B) from monolayers was determined after preloading its precursor, monochloro bimane (MCB).

RESULTS

A comparable amount of GS-B was excreted to the apical and basal compartments in the vector-transfected cells. In contrast, in cMOAT-transfected cells, the amount apically excreted was approximately twice that excreted into the basal compartment. Cyclosporin A (CsA) (30 microM), an inhibitor of cMOAT at higher concentrations, inhibited the preferential apical export of GS-B from cMOAT-transfected cells.

CONCLUSIONS

Rat cMOAT is functionally expressed on the apical membrane of MDCK cells after transfection.

Effect of food intake on pharmacokinetics and effects of a new thromboxane A2 receptor antagonist, S-1452

OBJECTIVE

To examine the effect of food ingestion on the pharmacokinetics of a new thromboxane A2 (TXA2) receptor antagonist, S-1452, and the inhibitory effect on platelet aggregation.

METHODS

Fifty milligrams of S-1452 was given orally to eight healthy subjects with or without food. Blood samples for determinations of plasma drug concentrations and of its effects on platelet aggregation were taken for a 12-h post-drug period.

RESULTS

The maximum plasma concentration of S-1452 was reduced by 47% and the time to maximum concentration was prolonged from 0.5 to 1.9 h after dosing with food. The inhibitory effect of S-1452 on platelet aggregations induced by U-46619, a TXA2 receptor agonist, and collagen persisted up to 9 h after dosing with and without food. The degrees of inhibition in the two trials did not differ significantly at any point.

CONCLUSION

These results suggest that although the absorption of S-1452 is delayed and, consequently, its plasma concentration is decreased after dosing with food, the inhibitory effect on platelet aggregation is not significantly influenced after 50 mg of the drug.

Sex differences in the metabolism of (+)-S-145, a novel thromboxane A2 receptor antagonist in rat

1. After the oral administration of 5 mg/kg S-1452 to rat, the plasma levels of (+)-S-145 were similar between the male and female, but there were sex differences in the profiles of its beta-oxidized and hydroxylated metabolites in plasma. 2. beta-Oxidation of (+)-S-145 determined in vitro was slightly higher in the female than in the male, and agreed with the plasma levels of the beta-oxidized metabolites. 3. 5-Hydroxylation activities of (+)-S-145 and beta-oxidized metabolites by rat liver microsomes were significantly higher in the male than in the female, but marked sex differences were not observed in 6-hydroxylation activities. These results revealed that differences in monooxygenase activities directly account for the sex differences in the plasma level of 5-hydroxylated metabolites, and that the peroxisomal beta-oxidation enzyme system also affected the plasma level of 6-hydroxylated metabolites. 4. Biliary excretion was higher in the male than in the female, and quantitative identification of metabolites in bile indicated that this was based on the prominent excretion of taurine conjugates in the male rat. This conclusion was supported by the fact that taurine conjugation activity was higher in male liver homogenates than in the female.

Transport of glutathione S-conjugates in the yeasts Saccharomyces cerevisiae

Transport of 2,4-dinitrophenyl-S-glutathione (DNP-SG) and a fluorescent glutathione S-conjugate, bimane-S-glutathione (B-SG) was studied in the baker's yeasts (S. cerevisiae). Both conjugates were exported from the cells; the transport was inhibited by fluoride and vanadate like in mammalian cells. B-SG was also found to be accumulated in the vacuoles. The transport rate of DNP-SG outside the cell was higher in a vacuolar-deficient strain. A significant ATP-dependent uptake of (3H)-DNP-SG by vacuoles was found. These results indicate that S. cerevisiae transport glutathione S-conjugates both outside the cells and into the vacuoles.

Pharmacokinetics of a new thromboxane A2 receptor antagonist, S-1452, and its effect on platelet aggregation in healthy volunteers

To study the pharmacokinetics of a new thromboxane A2 (TXA2) receptor antagonist, S-1452, eight healthy volunteers were given placebo or S-1452 orally on four occasions in step-wise increasing doses of 10 mg, 25 mg, and 50 mg separated by 2-week intervals. Blood samples for measurement of plasma concentrations of the drug and of its inhibitory effect on platelet aggregation were obtained for 24 hours after administration. Bleeding time after administration was measured. S-1452 was rapidly absorbed, with a peak plasma concentration at 30 minutes after administration. Thereafter, the drug was rapidly eliminated (elimination half-life, 0.4-0.5 hours), and no drug was detected at 6 hours. The inhibitory effect of S-1452 on platelet aggregation, which was stimulated by the TXA2 receptor agonist U-46619, persisted more than 6 hours after drug administration. Bleeding time was slightly prolonged after a single dose of S-1452. These results suggest that although S-1452 is rapidly eliminated in plasma, its inhibitory effects on platelet aggregation persist for a longer period. Careful observations are needed to prevent potential bleeding episodes during repeated treatment with the drug.

Microsomal metabolism of the 5-lipoxygenase inhibitor L-739,010: evidence for furan bioactivation

The novel 5-lipoxygenase inhibitor [1S,5R]-3-cyano-1-(3-furyl)-6-(6-[3-(3 alpha-hydroxy-6,8-dioxabicyclo[3.2.1]octanyl)]pyridin-2-yl- methoxyl)naphthalene (L-739,010), when administered to rats and rhesus monkeys, was found to produce metabolites which appeared to be covalently bound to plasma proteins. Incubation of [14C]L-739,010 with rat liver microsomes did not yield appreciable amounts of soluble metabolites but resulted in covalent binding to microsomal proteins. The covalent binding was NADPH-dependent and was enhanced by 1.5- and 2-fold in liver microsomes from rats, pretreated with phenobarbital and dexamethasone, respectively. Addition of triacetyloleandomycin and diethyldithiocarbamate to the incubation mixture inhibited the covalent binding by 60% and 46%, respectively. These findings suggest that the cytochrome P450 3A family of enzymes play an important role in the bioactivation of L-739,010. The presence of GSH attenuated the covalent binding by 50%, while methoxylamine, an aldehyde trapping agent, blocked the covalent binding completely and, concurrently, produced several soluble metabolic adducts. Subsequently, major methoxylamine adducts were identified by LC-MS/MS and NMR as O-methyloximes of the ring-opened furan moiety of L-739,010. Incubation of L-739,010 with methoxylamine and hepatic microsomes from dog, rhesus monkey, and human produced similar metabolic adducts as those formed by rat liver microsomes. Therefore, under these experimental conditions, the furan moiety, which undergoes oxidative cleavage to the highly reactive 2-butene-1,4-dialdehyde, represents the major site of L-739,010 biotransformation. This putative reactive intermediate could react with microsomal proteins in vitro and physiological proteins in vivo. Since furan bioactivation is believed to be responsible for the toxicity of many furan-containing compounds, the furan moiety of L-739,010 may be regarded as undesirable.

Characterization of (+/-)(-)[3H]epibatidine binding to nicotinic cholinergic receptors in rat and human brain

Epibatidine is an alkaloid that was first isolated from the skin of the Ecuadoran frog Epipedobates tricolor by Daly et al. [J. Am. Chem. Soc. 102:803-836 (1980)] and was found to have very high affinity for neuronal nicotinic receptors, where it acts as a potent agonist. Here we have measured and characterized the binding of (+/-)(-)[3H]epibatidine to nicotinic receptors in rat brain. In rat forebrain homogenates, (+/-)(-)[3H]epibatidine binds to two sites, with apparent affinities of 15 pM and 360 pM. Both of these binding sites have pharmacological profiles consistent with neuronal nicotinic receptors and a similar brain regional distribution. (+/-)(-)[3H]Epibatidine also binds to sites in rat adrenal gland, suggesting that it can label a subtype of nicotinic receptor found in peripheral ganglia as well as the subtype that predominates in brain. In human cerebral cortex as well, (+/-)(-)[3H]epibatidine binds two sites, one of which appears to have an affinity of < 1 pM. We conclude that (+/-)(-)[3H]epibatidine should be a very useful new tool for characterizing the properties and regulation of neuronal nicotinic receptors, including those not easily measurable with other radioligands.

Pharmacokinetics and plasma protein binding of the new potent class III antiarrhythmic agent 3-[4-(1H-imidazol-1-yl)benzoyl]-7-isopropyl-3, 7-diazabicyclo[3.3.1]nonane dihydroperchlorate

GLG-V-13 (3-[4-(1H-imidazol-1-yl)benzoyl]-7-isopropyl-3,7-diazabicyclo [3.3.1] nonane dihydroperchlorate, CAS 155029-33-7) has been shown to be a potent class III antiarrhythmic agent. The oral and intravenous pharmacokinetics and plasma protein binding of GLG-V-13 in dogs and in rabbits have now been investigated. Plasma GLG-V-13 concentration-time profiles, following an i.v. bolus dose of 6 mg/kg, were fitted to a 2-compartment model. The volume of distribution at steady state (Vd(ss)), the total systemic (ClB), and the elimination half-life (t1/2 beta) were 4.441 l/kg, 1.113 l/h/kg, and 2.485 h in dogs and 3.723 l/kg, 1.548 l/h/kg, and 1.401 h in rabbits. Following i.v. dosing, approximately 9.38% of the parent compound was excreted in dogs urine (0-72 h). Changes in plasma GLG-V-13 concentrations, after oral administration of GLG-V-13 (6 mg/kg), were best described by the 1-compartment pharmacokinetic model. The tmax and Cmax were 1.69 h, 0.54 mg/l in dogs and 1.44 h, 0.35 mg/l in rabbits. On oral administration, GLG-V-13 was moderately eliminated (t1/2kel' 1.867 h-1 in dogs and 3.961 h-1 in rabbits, respectively). Oral bioavailability was estimated to be 53.2% +/- 11.3% in dogs and 66.7% +/- 7.7% in rabbits. About 8.74% of the oral dose (6 mg/kg) was excreted via the dog urine (0-72 h). In vitro binding of GLG-V-13 to dog plasma protein was 29.4 +/- 9.90% (from 0.5 to 4 mg/l). Ex vivo binding of GLG-V-13 to dog plasma protein was 10.4 +/- 7.20%.(ABSTRACT TRUNCATED AT 250 WORDS)