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.

Preclinical disposition of MGS0274 besylate, a prodrug of a potent group II metabotropic glutamate receptor agonist MGS0008 for the treatment of schizophrenia.

MGS0274 besylate is an ester-based lipophilic prodrug of a metabotropic glutamate (mGlu) 2 and mGlu3 receptor agonist MGS0008 and being developed for the treatment of schizophrenia. We investigated the disposition of these compounds in rats and monkeys and in vitro metabolism in humans to evaluate whether MGS0274 besylate could be useful as a prodrug in humans. After the oral administration of MGS0274 besylate to monkeys (2.89 mg/kg), MGS0008 was immediately found in plasma, reached a maximum concentration at 4 hours postdose, and decreased with a terminal half-life of 16.7 hours; MGS0274 was barely detectable. The oral bioavailability as MGS0008 was 83.7%, which was approximately 20-fold greater than that after oral dosing of MGS0008 (3.8%). In rats, MGS0008 penetrated the cerebrospinal fluid and was eliminated slower than from plasma. The in vitro metabolism study indicated that MGS0274 was rapidly hydrolyzed to MGS0008, which was not further metabolized. After the intravenous administration of MGS0008 to rats and monkeys, almost all the dose was excreted unchanged in urine. These results suggested that MGS0274 was, as expected, presystemically hydrolyzed to MGS0008 after gastrointestinal absorption and that MGS0008 was distributed throughout the body without further metabolism and ultimately excreted in urine in the animals. Furthermore, the hydrolytic activity against MGS0274 in the human liver S9 fraction was comparable to that in monkeys, suggesting the possibility of the rapid presystemic hydrolysis of MGS0274 to MGS0008 in humans, as it is in monkeys. Consequently, MGS0274 besylate is expected to function as a preferable prodrug in humans.

Effect of coadministration of metformin with mirogabalin: Results from a phase 1, randomized, open-label, drug-drug interaction study
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Mirogabalin, a selective voltage-dependent calcium channel α2δ ligand under development for treatment of neuropathic pain, may be coadministered with metformin in patients with type 2 diabetes mellitus who have diabetic peripheral neuropathic pain. A randomized, open-label, single-dose, 3-treatment, 3-period crossover study evaluated the pharmacokinetics (PK) and safety of mirogabalin and metformin upon coadministration. Eligible subjects received 3 treatments separated by a 7-day washout period: 1 oral dose of mirogabalin 15 mg; 1 oral dose of metformin 850 mg; and coadministration of mirogabalin 15 mg with metformin 850 mg. PK assessments included maximum observed plasma concentration (Cmax); time of maximum plasma concentration; area under the concentration-time curve from time 0 to the last quantifiable concentration, and from 0 to infinity (AUClast and AUC0-inf, respectively). Safety assessments included adverse event (AE) monitoring and physical and clinical laboratory evaluations. 21 healthy men with a mean age of 30.4 years were enrolled and completed the study. Geometric least square means ratios (coadministration vs. alone; 90% confidence interval) for metformin Cmax, AUClast, and AUC0-inf were 1.00 (0.95 - 1.05), 1.04 (1.00 - 1.07), and 1.03 (1.00 - 1.07), respectively; ratios for mirogabalin were 0.94 (0.87 - 1.02), 0.99 (0.95 - 1.04), and 1.00 (0.96 - 1.04), respectively. Three subjects reported treatment-emergent AEs: dyspepsia, headache, and increased hepatic enzymes (resolved upon follow-up without sequelae). There were no deaths, serious AEs, or discontinuations due to AEs. Coadministration of mirogabalin and metformin is well tolerated in healthy subjects with no evidence of a drug-drug interaction.
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Pharmacokinetics, Pharmacodynamics, Safety, and Tolerability of Mirogabalin When Coadministered With Lorazepam, Zolpidem, Tramadol, or Ethanol: Results From Drug-Drug Interaction Studies in Healthy Subjects.

Four randomized, double-blind, placebo-controlled, 4-period drug-drug interaction studies were conducted in healthy subjects to evaluate the pharmacokinetic and pharmacodynamic (PD) interactions between mirogabalin and commonly used central nervous system depressants. Mirogabalin or placebo was administered alone or with single-dose lorazepam, zolpidem, tramadol, ethanol, or interacting drug placebo. Safety was assessed and serial samples for pharmacokinetic parameters were collected for up to 48 hours postdose. PD assessments included body sway (except tramadol), digit symbol substitution test, vertigo symptom scale short form, brief ataxia rating scale, and the Bond and Lader visual analog scale. Coadministration of mirogabalin with any of the 4 drugs did not cause any clinically relevant pharmacokinetic interactions. Peak mirogabalin concentration decreased by 28% (least squares mean ratio, 0.72; 90% confidence interval, [CI] 0.67, 0.76) following tramadol coadministration, and increased by 20% (least squares mean ratio, 1.20; 90%CI, 1.12, 1.28) following ethanol coadministration. Mirogabalin alone had little to no effect on PD parameters, but coadministration of mirogabalin with either lorazepam or ethanol increased the PD effects in body sway and digit symbol substitution test assays. Mirogabalin/lorazepam and mirogabalin/zolpidem increased occurrence of somnolence. Increased incidence of nausea and headache was noted with mirogabalin/tramadol and mirogabalin/ethanol, respectively.

Identification of Metabolism and Excretion Differences of Procymidone between Rats and Humans Using Chimeric Mice: Implications for Differential Developmental Toxicity.

A metabolite of procymidone, hydroxylated-PCM, causes rat-specific developmental toxicity due to higher exposure to it in rats than in rabbits or monkeys. When procymidone was administered to chimeric mice with rat or human hepatocytes, the plasma level of hydroxylated-PCM was higher than that of procymidone in rat chimeric mice, and the metabolic profile of procymidone in intact rats was well reproduced in rat chimeric mice. In human chimeric mice, the plasma level of hydroxylated-PCM was less, resulting in a much lower exposure. The main excretion route of hydroxylated-PCM-glucuronide was bile (the point that hydroxylated-PCM enters the enterohepatic circulation) in rat chimeric mice, and urine in human chimeric mice. These data suggest that humans, in contrast to rats, extensively form the glucuronide and excrete it in urine, as do rabbits and monkeys. Overall, procymidone's potential for causing teratogenicity in humans must be low compared to that in rats.

Development and validation of a high-performance liquid chromatography-tandem mass spectrometry method to quantify LY-354,740 in rat and marmoset plasma.

LY-354,740 (eglumegad) is a selective and potent agonist of the metabotropic glutamate group II receptors (mGluR2,3) that has already entered clinical trials as a potential anti-psychotic agent and therefore has well-documented pharmacokinetic (PK), safety and tolerability profiles in human. Whereas its development as an anti-psychotic agent has not been pursued, LY-354,740 may have potential in other neuroscience-related fields, notably anxiety and neuro-protection. The common marmoset is a small primate that has long been used in neuroscience. However, given its small size and small circulating blood volume, conducting PK studies to determine the therapeutic effectiveness of LY-354,740 at clinically-relevant doses is challenging. Here, we have developed and validated a simple, sensitive and selective analytical method that enables quantification of LY-354,740 using a small volume of plasma. The analytical method consisted of protein precipitation followed by high-performance liquid chromatography with heat assisted electrospray ionisation mass spectrometry (UHPLC-HESI-MS/MS). The chromatographic separation was achieved using gradient elution with a mobile phase consisting of acetonitrile and 10mM ammonium formate (pH 3) on a Thermo Scientific Acclaim Trinity P1 analytical column (100x3.0mm I.D., 3µm) operating at 45°C and at a flow rate of 900µl/min. The method displays a linear relationship ranging from 20.0 to 5000ng/ml. Intra- and inter-day relative standard deviations are less than 5.7% and 7.0%, respectively and the accuracy ranged from 91.0 to 106.0%. The UHPLC-HESI-MS/MS analytical method we describe here is simple, sensitive, specific and capable of quantifying LY-354,740 in both rat and marmoset plasma, and is suitable to conduct PK studies after a single sub-cutaneous dose of 1.0mg/kg or lower in both species.

Evaluation of single and multiple doses of a novel mGlu2 agonist, a potential antipsychotic therapy, in healthy subjects.

AIMS: The safety, tolerability, pharmacokinetics (PK) and pharmacodynamics of single and multiple doses of a novel mGlu2 agonist were assessed in healthy males. METHODS: In two, Phase 1 investigator- and subject-blind, placebo-controlled studies, oral doses of prodrug LY2979165 were evaluated: single doses (20-150 mg, N = 30) and multiple once-daily (QD) doses (20-400 mg; N = 84), using a titration regimen. The plasma and urine PK of LY2979165 and active moiety, 2812223, were measured. Cerebrospinal fluid (CSF) was collected to determine PK and neurotransmitter levels. Safety parameters were assessed throughout. RESULTS: Nausea and vomiting were dose limiting following single doses; dose titration allowed higher doses to be tested over 14 days. The most common adverse events related to LY2979165 were dizziness, vomiting, nausea, somnolence and headache. The plasma PK of 2812223 were approximately linear with minimal accumulation with QD dosing. Conversion of LY2979165 to 2812223 was extensive, with minimal LY2979165 measurable in plasma. There was no effect of food on the PK of LY2979165 and 2812223. After 60 mg LY2979165 single-dose, 2812223 exposure in CSF was approximately 2-6% and plasma exposure and peak concentrations were approximately four-fold higher than the mGlu2 agonist in vitro EC50 value. No consistent effects were observed on CSF neurotransmitter levels. CONCLUSIONS: Oral doses of LY2979165 up to 60 mg as a single dose and up to 400 mg given as multiple QD doses, using a titration regimen, were well tolerated with linear PK. Overall, these data support further clinical evaluation of LY2979165.

Population pharmacokinetic modeling and simulation for assessing renal impairment effect on the pharmacokinetics of mirogabalin.

A population pharmacokinetic model was developed to describe plasma concentrations of mirogabalin and lactam metabolite, obtained following a single oral dose of 5 mg mirogabalin to subjects with varying degrees of renal function.A 2-compartment model was used for both mirogabalin and lactam metabolite. Body weight was a significant covariate on volume of distribution of mirogabalin and lactam metabolite, whereas creatinine clearance significantly affected both renal and nonrenal clearance of mirogabalin. The total clearance of mirogabalin was decreased by 25%, 54%, and 76% in subjects with mild, moderate, and severe renal impairment, respectively, relative to normal controls. Simulation results showed that in comparison with the normal renal function group receiving mirogabalin 15 mg once or twice daily, dose reduction by 50% or 75% in subjects with moderate or severe renal impairment would produce similar AUCss values, but 37%-43% or 28%-32% lower Cmax,ss of mirogabalin. Predicted mirogabalin AUCss was 26% higher, whereas Cmax,ss was similar in subjects with mild renal impairment compared with those having normal renal function taking the same dose. Results support a dose reduction by 50% or 75% in subjects with moderate or severe renal impairment. No dose adjustment seemed necessary for subjects with mild renal impairment.

Metabolism and disposition of ABT-894, a novel α4ß2 neuronal acetylcholine receptor agonist, in mice and monkeys.

1. Metabolism and disposition of ABT-894 was investigated in hepatocytes, in mice and monkeys receiving [(14)C]ABT-894. 2. In hepatocytes, turnover rate of ABT-894 was slow in all species with more than 90% of parent remaining. M3 (carbamoyl glucuronide) and M6 (mono-oxidation) were detected across species. 3. ABT-894 showed species-specific disposition profiles. ABT-894 was primarily eliminated by renal secretion in mice. Whereas, monkey mainly cleared ABT-894 metabolically. 4. ABT-894 underwent two primary routes of metabolism in monkeys: N-carbamoyl glucuronidation to form M3 and oxidation product M1. M3 was the major metabolite in monkey excreta. M3 was observed in mice urine. Circulating levels of M3 in terms of M3/ABT-894 ratios were essentially absent in mice, but were high in monkeys. 5. Understanding the species difference in the clearance mechanism is the key to the accurate projection of the human clearance and preclinical safety assessment. Lack of species difference in the metabolism of ABT-894 in hepatocytes certainly creates a challenge in predicting its metabolism and pharmacokinetics in human. Based on available metabolism and pharmacokinetic data of ABT-894 in human, monkey is the preferred species in predicting human clearance since it presents a similar clearance mechanism from that observed in human.

Suppressed circulating bicyclo-PGE2 levels and leukocyte COX-2 transcripts in children co-infected with P. falciparum malaria and HIV-1 or bacteremia.

In holoendemic Plasmodium falciparum transmission regions, malarial anemia is a leading cause of childhood morbidity and mortality. Identifying biomarkers of malaria disease severity is important for identifying at-risk groups and for improved understanding of the molecular pathways that influence clinical outcomes. We have previously shown that decreased cyclooxygenase (COX)-2-derived prostaglandin E2 (PGE2) levels are associated with enhanced clinical severity in cerebral malaria, malarial anemia, and malaria during pregnancy. Since children with malaria often have increased incidence of additional infections, such as bacteremia and HIV-1, we extend our previous findings by investigating COX-2 and PGE2 in children with falciparum malaria and co-infection with either bacteremia or HIV-1. Plasma bicyclo-PGE2/creatinine levels and peripheral blood COX-2 transcripts were significantly reduced in co-infected children relative to those with malaria mono-infection. Furthermore, suppression of circulating bicyclo-PGE2 was significantly associated with reduced hemoglobin levels in both mono- and co-infected children with malaria, suggesting that bicyclo-PGE2 may represent both a marker and mediator of malaria pathogenesis.

Bicyclization and tethering to albumin yields long-acting peptide antagonists.

Proteolytically stable peptide architectures are required for the development of long-acting peptide therapeutics. In this work, we found that a phage-selected bicyclic peptide antagonist exhibits an unusually high stability in vivo and subsequently deciphered the underlying mechanisms of peptide stabilization. We found that the bicyclic peptide was significantly more stable than its constituent rings synthesized as two individual macrocycles. The two rings protect each other from proteolysis when linked together, conceivably by constraining the conformation and/or by mutually shielding regions prone to proteolysis. A second stabilization mechanism was found when the bicyclic peptide was linked to an albumin-binding peptide to prevent its rapid renal clearance. The bicyclic peptide conjugate not only circulated 50-fold longer (t(1/2) = 24 h) but also became entirely resistant to proteolysis when tethered to the long-lived serum protein. The bicyclic peptide format overcomes a limitation faced by many peptide leads and appears to be suitable for the generation of long-acting peptide therapeutics.

PET imaging-based evaluation of hepatobiliary transport in humans with (15R)-11C-TIC-Me.

UNLABELLED: It is well accepted that drug transporters play a pivotal role in hepatobiliary excretion of anionic drugs, in which drug-drug interactions and genetic polymorphisms are known to cause variations. However, PET probes for in vivo functional characterization of these transporters have not been established yet. We used PET to investigate hepatic uptake and subsequent canalicular efflux of (11)C-labeled (15R)-16-m-tolyl-17,18,19,20-tetranorisocarbacyclin methyl ester [(15R)-(11)C-TIC-Me)] in healthy subjects. METHODS: Serial PET scans of the abdominal region in healthy male subjects were obtained with or without the organic anion-transporting polypeptide (OATP) inhibitor rifampicin after intravenous injection of (15R)-(11)C-TIC-Me as a radiotracer. Venous blood samples and PET images were obtained at frequent intervals up to 30 min after administration of the PET tracer. Dynamic imaging data were evaluated by integration plots of data collected for 2-10 min and for 10-30 min after tracer administration for the determination of tissue uptake clearance and biliary efflux clearance, respectively. RESULTS: After rapid hydrolysis in blood, the acid form-(11)C-labeled (15R)-16-m-tolyl-17,18,19,20-tetranorisocarbacyclin [(15R)-(11)C-TIC]-accumulated in the liver (37% of the dose by 17 min), and the radioactivity was then excreted into the bile (6.2% by 30 min). Rifampicin (600 mg by mouth), a potent OATP inhibitor, significantly reduced the radioactivity excreted into the bile (by 44%) by inhibiting both uptake (by 45%) and subsequent canalicular efflux (by 62%). (15R)-(11)C-TIC is an in vitro substrate of OATP1B1 and OATP1B3, and clinically relevant concentrations of rifampicin inhibited uptake by OATP1B1 and OATP1B3. These results demonstrated that in humans, (15R)-(11)C-TIC-associated radioactivity is excreted into the bile by organic anion transport systems. CONCLUSION: We demonstrated that PET image analysis with (15R)-(11)C-TIC-Me is useful for investigating variations in OATP function in the human hepatobiliary transport system.

Activation of α7 nicotinic receptors improves phencyclidine-induced deficits in cognitive tasks in rats: implications for therapy of cognitive dysfunction in schizophrenia.

RATIONALE: Nicotinic α7 acetylcholine receptors (nAChRs) have been highlighted as a target for cognitive enhancement in schizophrenia. AIM: To investigate whether the deficits induced by sub-chronic phencyclidine (PCP) in reversal learning and novel object recognition could be attenuated by the selective α7 nAChR full agonist, PNU-282987. METHODS: Adult female hooded-Lister rats received sub-chronic PCP (2mg/kg) or vehicle i.p. twice daily for 7days, followed by 7 days washout. In cohort 1, PCP-treated rats then received PNU-282987 (5, 10, 20mg/kg; s.c.) or vehicle and were tested in the reversal-learning task. In cohort 2, PCP-treated rats received PNU-282987 (10mg/kg; s.c.) or saline for 15days and were tested in the novel object recognition test on day 1 and on day 15, to test for tolerance. RESULTS: Sub-chronic PCP produced significant deficits in both cognitive tasks (P<0.01-0.001). PNU-282987 attenuated the PCP-induced deficits in reversal learning at 10mg/kg (P<0.01) and 20mg/kg (P<0.001), and in novel object recognition at 10mg/kg on day 1 (P<0.01) and on day 15 (P<0.001). CONCLUSIONS: These data show that PNU-282987 has efficacy to reverse PCP-induced deficits in two paradigms of relevance to schizophrenia. Results further suggest that 15-day once daily dosing of PNU-282987 (10mg/kg s.c.) does not cause tolerance in the rat. This study suggests that activation of α7 nAChRs, may represent a suitable strategy for improving cognitive deficits of relevance to schizophrenia.

Evaluation of cynomolgus monkey pregnane X receptor, primary hepatocyte, and in vivo pharmacokinetic changes in predicting human CYP3A4 induction.

Monkeys have been proposed as an animal model to predict the magnitude of human clinical drug-drug interactions caused by CYP3A4 enzyme induction. To evaluate whether the cynomolgus monkey can be an effective in vivo model, human CYP3A4 inducers were evaluated both in vitro and in vivo. First, a full-length pregnane X receptor (PXR) was cloned from the cynomolgus monkey, and the sequence was compared with those of rhesus monkey and human PXR. Cynomolgus and rhesus monkey PXR differed by only one amino acid (A68V), and both were highly homologous to human PXR (approximately 96%). When the transactivation profiles of 30 compounds, including known inducers of CYP3A4, were compared between cynomolgus and human PXR, a high degree of correlation with EC(50) values was observed. These results suggest that cynomolgus and human PXR respond in a similar fashion to these ligands. Second, two known human CYP3A4 inducers, rifampicin and hyperforin, were tested in monkey and human primary hepatocytes for induction of CYP3A enzymes. Both monkey and human hepatocytes responded similarly to the inducers and resulted in increased RNA and enzyme activity changes of CYP3A8 and CYP3A4, respectively. Lastly, in vivo induction of CYP3A8 by rifampicin and hyperforin was shown by significant reductions of midazolam exposure that were comparable with those in humans. These results show that the cynomolgus monkey can be a predictive in vivo animal model of PXR-mediated induction of human CYP3A4 and can provide a useful assessment of the resulting pharmacokinetic changes of affected drugs.

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.

The effect of St. John's wort on the pharmacokinetics, metabolism and biliary excretion of finasteride and its metabolites in healthy men.

The aim of this study was to investigate what the consequences of induced drug metabolism, caused by St. John's wort (SJW, Hypericum perforatum) treatment, would have on the plasma, biliary and urinary pharmacokinetics of finasteride and its two previously identified phase I metabolites (hydroxy-finasteride and carboxy-finasteride). Twelve healthy men were administered 5mg finasteride directly to the intestine via a catheter with a multi-channel tubing system, Loc-I-Gut, before and after 14 days SJW (300mg b.i.d, hyperforin 4%) treatment. Bile samples were withdrawn via the Loc-I-Gut device from the proximal jejunum. LC-ESI-MS/MS was used to analyze finasteride and its metabolites in plasma, bile and urine. HPLC-UV was used to analyze hyperforin in plasma. The herbal treatment significantly reduced the peak plasma concentration (C(max)), the area under the plasma concentration-time curve (AUC(0-24h)) and the elimination half-life (t(1/2)) of finasteride. The geometric mean ratios (90% CI) were 0.42 (0.36-0.49), 0.66 (0.56-0.79) and 0.54 (0.48-0.61), respectively. Finasteride was excreted unchanged to a minor extent into bile and urine. Hydroxy-finasteride was not detected in plasma, bile or urine. Carboxy-finasteride was quantified in all three compartments and its plasma pharmacokinetics was significantly affected by SJW treatment. Hyperforin concentration in plasma was 21+/-7ng/ml approximately 12h after the last dose of the 14 days SJW treatment. In conclusion, SJW treatment for 2 weeks induced the metabolism of finasteride and caused a reduced plasma exposure of the drug. New knowledge was gained about the biliary and urinary excretion or the drug and its metabolites.

Efficacy and tolerability of an mGlu2/3 agonist in the treatment of generalized anxiety disorder.

LY354740, a potent and selective mGlu (metabotropic glutamate receptor)2/3 agonist, has shown efficacy in the treatment of generalized anxiety disorder (GAD). LY544344 is a LY354740 prodrug that increases LY354740 bioavailability. This 8-week study was designed to evaluate the efficacy, safety, and tolerability of LY544344 in the treatment of GAD. Participants had a diagnoses of GAD, baseline Hospital Anxiety and Depression Scale anxiety subscale scores > or = 10, and moderate illness severity. Patients were randomized to double-blind treatment with LY544344 16 mg b.i.d. (n = 28), LY544344 8 mg b.i.d. (n = 36), or placebo (n = 44). LY544344 16 mg b.i.d.-treated patients showed significantly greater improvement from baseline in Hamilton Anxiety and Clinical Global Impression-Improvement scores, as well as response and remission rates compared with placebo-treated patients. LY544344 was well tolerated and there were no significant differences in the incidence of treatment-emergent adverse events among the three treatment groups. However, the trial was discontinued early based on findings of convulsions in preclinical studies. In conclusion, the findings of this study support the potential efficacy of mGlu2/3 receptor agonist agents in the treatment of GAD. Additional studies will be needed to further assess the toxicological and clinical profile of LY354740/LY544344.

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.

Cycloisomerization of activated (2E,4Z)-heptatrienoate and its relevance to crispatene (bio)synthesis. A case of concerted and stepwise uncertainty.

A single transition structure was located on the potential energy surface of the cycloisomerization of protic and Lewis acid activated (2E,4Z)-heptatrienal and the corresponding methyl ester to provide the bicyclo[3.1.0]hexene derivatives, the central skeleton of the crispatene natural products. A two-dimensional scan of the C-C bond-forming reactions revealed a barrierless cyclopropane closure following the pentadienyl cycloisomerization, with preservation of the stereochemical information.

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.