Acute toxicity analysis of an inhibitor of BCL2, Disarib, in rats

Apoptosis or programmed cell death is a highly regulated process, which eliminates unwanted and damaged cells. Inhibition of apoptosis is a hallmark of cancer cells. BCL2 family proteins are known to play a vital role in the regulation of apoptosis. Overexpression of BCL2, an antiapoptotic protein, provides the advantage of prolonged survival to cancer cells. Over the years, several BCL2 inhibitors have been investigated extensively for their anticancer potential. However, most of them were abolished before clinical use due to their side effects. Previously, we had identified and characterized a novel BCL2 inhibitor, Disarib, with the potential to eliminate tumor cells in a BCL2 specific manner leading to reduction in tumor burden in multiple mouse models. Notably, a head-to-head comparison of Disarib to ABT199, the only FDA approved BCL2 inhibitor revealed that Disarib is as potent as ABT199. Recent studies using mice revealed that Disarib did not invoke significant side effects in mice. In the present study, we have investigated the acute toxicity of Disarib in Wistar rats. The bioavailability studies following exposure of Disarib in Wistar rats revealed its maximum availability in serum at 24 h following oral administration. Acute toxicity analysis revealed that even a dose as high as 2000 mg/kg of Disarib did not cause significant toxicity in rats. There was no significant variation in blood parameters or kidney and liver functions following administration of Disarib. Histological analysis of different tissues from Disarib treated groups revealed standard architecture with no observable cellular damage. Importantly, exposure to Diasrib did not result in genotoxicity as determined by micronucleus assay. Further, solubility assays revealed that besides DMSO, Disarib is also soluble in alcohol. While the high acidic condition can increase the solubility of Disarib, even a lower percentage of alcohol with acidic conditions can improve its solubility. Thus, the toxicological profile in the current study revealed no significant side effects when Disarib was administered orally to rats.

Design, synthesis, and evaluation of substituted 2-acylamide-1,3-benzo[d]zole analogues as agents against MDR- and XDR-MTB

N-(5-Chlorobenzo[d]oxazol-2-yl)-4-methyl-1,2,3-thiadiazole-5-carboxamideox-amide has been identified as a potent inhibitor of Mtb H37Rv, with a minimum inhibitory concentration (MIC) of 0.42 μM. In this study, a series of substituted 2-acylamide-1,3-zole analogues were designed and synthesized, and their anti-Mtb activities were analyzed. In total, 17 compounds were found to be potent anti-Mtb agents, especially against the MDR- and XDR-MTB strains, with MIC values < 10 μM. These analogues can inhibit both drug-sensitive and drug-resistant Mtb. Four representative compounds were selected for further profiling, and the results indicate that compound 18 is acceptably safe and has favorable pharmacokinetic (PK) properties. In addition, this compound displays potent activity against Gram-positive bacteria, with MIC values in the range of 1.48-11.86 μM. The data obtained herein suggest that promising anti-Mtb candidates may be developed via structural modification, and that further research is needed to explore other compounds.

A Phase 2 Study of AMO-02 (Tideglusib) in Congenital and Childhood-Onset Myotonic Dystrophy Type 1 (DM1)

BACKGROUND

GSK3β is an intracellular regulatory kinase that is dysregulated in multiple tissues in type 1 myotonic dystrophy, a rare neuromuscular disorder that manifests at any age. AMO-02 (tideglusib) inhibits GSK3β activity in preclinical models of type 1 myotonic dystrophy and promotes cellular maturation as well as normalizes aberrant molecular and behavioral phenotypes. This phase 2 study assessed the pharmacokinetics, safety and tolerability, and preliminary efficacy of AMO-02 in adolescents and adults with congenital and childhood-onset type 1 myotonic dystrophy.

METHODS

Sixteen subjects (aged 13 to 34 years) with congenital and childhood-onset type 1 myotonic dystrophy received 12 weeks of single-blind fixed-dose oral treatment with either 400 mg (n = 8) or 1000 mg (n = 8) AMO-02 (NCT02858908). Blood samples were obtained for pharmacokinetic assessment. Safety assessments, such as laboratory tests and electrocardiograms, as well as efficacy assessments of syndromal, cognitive, and muscular functioning, were obtained.

RESULTS

AMO-02 plasma concentrations conformed to a two-compartment model with first-order absorption and elimination, and dose-dependent increases in exposure (area under the curve) were observed. AMO-02 was generally safe and well-tolerated. No early discontinuations due to adverse events or dose adjustments of AMO-02 occurred. The majority of subjects manifested clinical improvement in their central nervous system and neuromuscular symptoms after 12 weeks of treatment compared with the placebo baseline, with a larger response noted at the 1000 mg/day dose level. AMO-02 exposure (cumulative area under the curve) was significantly correlated (P < 0.01) with change from baseline on several key efficacy assessments.

CONCLUSION

AMO-02 has favorable pharmacokinetic and clinical risk/benefit profiles meriting further study as a potential treatment for congenital and childhood-onset type 1 myotonic dystrophy.

First Human Use of RUC-4: A Nonactivating Second-Generation Small-Molecule Platelet Glycoprotein IIb/IIIa (Integrin αIIbβ3) Inhibitor Designed for Subcutaneous Point-of-Care Treatment of ST-Segment-Elevation Myocardial Infarction

Background Despite reductions in door-to-balloon times for primary coronary intervention, mortality from ST-segment-elevation myocardial infarction has plateaued. Early pre-primary coronary intervention treatment of ST-segment-elevation myocardial infarction with glycoprotein IIb/IIIa inhibitors improves pre-primary coronary intervention coronary flow, limits infarct size, and improves survival. We report the first human use of a novel glycoprotein IIb/IIIa inhibitor designed for subcutaneous first point-of-care ST-segment-elevation myocardial infarction treatment. Methods and Results Healthy volunteers and patients with stable coronary artery disease receiving aspirin received escalating doses of RUC-4 or placebo in a sentinel-dose, randomized, blinded fashion. Inhibition of platelet aggregation (IPA) to ADP (20 μmol/L), RUC-4 blood levels, laboratory evaluations, and clinical assessments were made through 24 hours and at 7 days. Doses were increased until reaching the biologically effective dose (the dose producing ≥80% IPA within 15 minutes, with return toward baseline within 4 hours). In healthy volunteers, 15 minutes after subcutaneous injection, mean±SD IPA was 6.9%+7.1% after placebo and 71.8%±15.0% at 0.05 mg/kg (n=6) and 84.7%±16.7% at 0.075 mg/kg (n=6) after RUC-4. IPA diminished over 90 to 120 minutes. In patients with coronary artery disease, 15 minutes after subcutaneous injection of placebo or 0.04 mg/kg (n=2), 0.05 mg/kg (n=6), and 0.075 mg/kg (n=18) of RUC-4, IPA was 14.6%±11.7%, 53.6%±17.0%, 76.9%±10.6%, and 88.9%±12.7%, respectively. RUC-4 blood levels correlated with IPA. Aspirin did not affect IPA or RUC-4 blood levels. Platelet counts were stable and no serious adverse events, bleeding, or injection site reactions were observed. Conclusions RUC-4 provides rapid, high-grade, limited-duration platelet inhibition following subcutaneous administration that appears to be safe and well tolerated. Registration URL: https://www.clini​caltr​ials.gov; Unique identifier: NTC03844191.

Effect of acibenzolar-S-methyl phototransformation on its elicitation activity in tobacco cells

The plant activator acibenzolar-S-methyl (BTH) undergoes phototransformation when exposed to solar radiation. Here we investigated the changes in its elicitation properties on BY-2 tobacco cells at different stages of the photochemical reaction. Both pure BTH and formulated BTH were irradiated in controlled conditions to achieve different extents of conversion. Both pure BTH (900 μM) and Bion® (0.4 g.L-1) induced BY-2 cell death, but BTH photoconverted to an extent of 25 ± 3% lowered the cell death rate. A kinetic study of β-1,3-glucanase and chitinase activities was conducted on BY-2 extracellular medium. Exposure of tobacco cells to either pure BTH or Bion® resulted in a significant increase in the activities of both defense enzymes, which peaked 48 h after the treatment. The pathogenesis-related (PR) protein activities were quantified 48 h after elicitation for a range of phototransformed BTH solutions. The enzyme activities were reduced when BY-2 cells were treated with solutions in which BTH conversion was 22 ± 3%, 42 ± 3% and 100 ± 3%, but were not affected by the solution in which BTH was phototransformed at 60%, suggesting that some of the secondary photoproducts also exhibit eliciting properties. Solar irradiation of BTH thus impairs its elicitation properties, but this impairment depends strongly on the extent of phototransformation.

The NK3 Receptor Antagonist ESN364 Suppresses Sex Hormones in Men and Women

CONTEXT

Women's health disorders are commonly treated by agents that suppress the hypothalamic-pituitary-gonadal axis. NK3 receptor antagonism modulates this axis with distinct pharmacology compared to existing therapies.

OBJECTIVE

The study aim was to evaluate safety, pharmacokinetics, and pharmacodynamics on gonadotropins and sex hormones after single- and multiple-dose administration of an NK3R antagonist to healthy men and women.

DESIGN AND SETTING

This was a first-in-human, double-blind, placebo-controlled, combined single and multiple ascending dose trial.

PARTICIPANTS

Forty-one men and 24 regularly cycling women participated in the study.

INTERVENTION(S)

In part 1 of the study, men received single oral doses of 3-180 mg or placebo. In part 2, men received placebo or 20, 60, or 180 mg each day for 10 days. In part 3, women received placebo or 20, 60, or 180 mg each day for 21 days, where dosing was initiated on day 3 ± 2 after menses.

MAIN OUTCOME MEASURE(S)

Safety, tolerability, pharmacokinetics, and pharmacodynamics on circulating levels of LH, FSH, testosterone, estradiol, and progesterone, in addition to physiological biomarkers of endometrial thickening, follicle growth, and the duration of the menstrual cycle were evaluated.

RESULTS

ESN364 was well-tolerated and rapidly bioavailable with linear pharmacokinetics and no drug accumulation with repeated, daily oral administration. Drug treatment dose-dependently decreased basal LH, but not FSH, and consequently decreased estradiol and progesterone (in women) as well as testosterone (in men). The hormonal changes in women corresponded to delayed ovulation, decreased endometrial thickening, impeded follicular maturation, and prolongation of the menstrual cycle. Drug effects were rapidly reversible.

CONCLUSIONS

Oral administration of the NK3R antagonist, ESN364, suppressed the hypothalamic-pituitary-gonadal axis in healthy volunteers by selective modulation of gonadotropin secretion, leading to a restrained decrease in ovarian hormone levels in women. These results suggest that ESN364 may offer therapeutic benefit in the treatment of women's health disorders with a mitigated risk of menopausal-like adverse events.

Synthesis and biological activities of novel pleuromutilin derivatives with a substituted thiadiazole moiety as potent drug-resistant bacteria inhibitors

A series of novel pleuromutilin derivatives possessing thiadiazole moieties were synthesized via acylation reactions under mild conditions. The in vitro antibacterial activities of the derivatives against methicillin-resistant Staphylococcus aureus, methicillin-resistant Staphylococcus epidermidis, Escherichia coli, and Streptococcus agalactiae were tested by the agar dilution method and Oxford cup assay. The majority of the tested compounds displayed moderate antibacterial activities. Importantly, the three compounds with amino or tertiary amine groups in their side chains, 11, 13b, and 15c, were the most active antibacterial agents. Docking experiments carried out on the peptidyl transferase center (PTC) of 23S rRNA proved that there is a reasonable direct correlation between the binding free energy (ΔGb, kcal/mol) and the antibacterial activity. Moreover, the pharmacokinetic profiles of 11 and 15c in rat were characterized by moderate clearance and oral bioavailability.

Thiadiazolopiperazinyl ureas as inhibitors of fatty acid amide hydrolase

A series of thiadiazolopiperazinyl aryl urea fatty acid amide hydrolase (FAAH) inhibitors is described. The molecules were found to inhibit the enzyme by acting as mechanism-based substrates, forming a covalent bond with Ser241. SAR and PK properties are presented.

Synthesis and identification of [1,2,4]thiadiazole derivatives as a new series of potent and orally active dual agonists of peroxisome proliferator-activated receptors alpha and delta

Cardiovascular disease is the most common cause of morbidity and mortality in developed nations. To effectively target dyslipidemia to reduce the risk of cardiovascular disease, it may be beneficial to activate the peroxisome proliferator-activated receptors (PPARs) PPARalpha and PPARdelta simultaneously through a single molecule. Replacement of the methylthiazole of 5 (the PPARdelta selective agonist) with [1,2,4]thiadiazole gave compound 13, which unexpectedly displayed submicromolar potency as a partial agonist at PPARalpha in addition to the high potency at PPARdelta. Optimization of 13 led to the identification of 24 as a potent and selective PPARalpha/delta dual agonist. Compound 24 and its close analogs represent a new series of PPARalpha/delta dual agonists. The high potency, significant gene induction, excellent PK profiles, and good in vivo efficacies in three animal models may render compound 24 as a valuable pharmacological tool in elucidating the complex roles of PPARalpha/delta dual agonists and as a potential treatment of the metabolic syndrome.

Evaluation of [18F]fluoroxanomeline {5-{4-[(6-[18F]fluorohexyl)oxy]-1,2,5-thiadiazol-3-yl}-1-methyl-1,2,3,6-tetrahydropyridine} in muscarinic knockout mice

INTRODUCTION

We set out to develop a muscarinic M1-selective agonist (based on the structure of the functionally M1-selective xanomeline) that could be radiolabeled with fluorine-18 for use as an imaging agent for positron emission tomography.

METHODS

The radiochemical synthesis was achieved, employing the arts of organic and radiochemical syntheses. Binding selectivity studies employed biodistribution studies, using autoradiography and/or tissue dissection, in wild-type or muscarinic receptor knockout mice.

RESULTS

[(18)F]Fluoroxanomeline shows rather uniform uptake in all mouse brain regions and high specific binding, with a brain-to-blood ratio of 32 at 60 min postinjection. In addition, the specific binding is demonstrated by a 58% to 75% decrease in brain uptake upon coinjection with 5 nmol of unlabeled fluoroxanomeline or xanomeline. Brain uptake studies with [(3)H]xanomeline in muscarinic knockout mice show decreased uptake in M1 (17-34%) and M2 (2-20%) knockout mice compared with control. However, statistical significance was observed in only a few regions. Comparison of [(18)F]fluoroxanomeline in knockout mice showed no difference in M1 or M4 knockout mice but a general decrease in M2 (2-24%) knockout mice. The decrease of [(18)F]fluoroxanomeline uptake in M2 knockout mice reached statistical significance in brain stem, cerebellum, frontal cortex, hippocampus, inferior colliculus and superior colliculus.

CONCLUSION

Although xanomeline displays highly selective M1 agonist activity in functional assays, little selectivity for muscarinic subtype binding was observed for xanomeline or its fluorine-containing analogue, fluoroxanomeline. This emphasizes the lack of correlation between functional selectivity and binding selectivity.

Carbonic anhydrase inhibitors: X-ray crystallographic studies for the binding of 5-amino-1,3,4-thiadiazole-2-sulfonamide and 5-(4-amino-3-chloro-5-fluorophenylsulfonamido)-1,3,4-thiadiazole-2-sulfonamide to human isoform II

The X-ray crystal structures of 5-amino-1,3,4-thiadiazole-2-sulfonamide (the acetazolamide precursor) and 5-(4-amino-3-chloro-5-fluorophenylsulfonamido)-1,3,4-thiadiazole-2-sulfonamide in complex with the human isozyme II of carbonic anhydrase (CA, EC 4.2.1.1) are reported. The thiadiazole-sulfonamide moiety of the two compounds binds in the canonic manner to the zinc ion and interacts with Thr199, Glu106, and Thr200. The substituted phenyl tail of the second inhibitor was positioned in the hydrophobic part of the binding pocket, at van der Waals distance from Phe131, Val 135, Val141, Leu198, Pro202, and Leu204. These structures may help in the design of better inhibitors of these widespread zinc-containing enzymes.

Novel Selective Inhibitors of Neutral Endopeptidase for the Treatment of Female Sexual Arousal Disorder. Synthesis and Activity of Functionalized Glutaramides

Female sexual arousal disorder (FSAD) is a highly prevalent sexual disorder affecting up to 40% of women. We describe herein our efforts to identify a selective neutral endopeptidase (NEP) inhibitor as a potential treatment for FSAD. The rationale for this approach, together with a description of the medicinal chemistry strategy, lead compounds, and SAR investigations are detailed. In particular, the strategy of starting with the clinically precedented selective NEP inhibitor, Candoxatrilat, and targeting low molecular weight and relatively polar mono-carboxylic acids is described. This led ultimately to the prototype development candidate R-13, for which detailed pharmacology and pharmacokinetic parameters are presented.(1)

Pharmacokinetic studies of a novel 1,2,4-thiadiazole derivative, inhibitor of Factor XIIIa, in the rabbit by a validated HPLC method

Activated Factor XIII (FXIIIa) stabilizes fibrin clot by covalent cross-linking of fibrin strands in the fibrin, making it resistant to physiological and pharmacologically induced fibrinolysis. Inhibition of Factor XIIIa offers a novel approach to treatment of thrombosis. Selected derivatives of 1,2,4-thiadiazoles, presently in discovery and development, may offer new treatment strategies as inhibitors of Factor XIIIa. In order to evaluate its pharmacokinetic (PK) profile and to facilitate the selection of drug candidates for drug discovery and development process, we developed and validated a simple and selective reversed-phase high-performance liquid chromatographic method (RP-HPLC) with UV detection for the determination of N-[6-(imidazo[1,2-d][1,2,4]thiadiazol-3-ylamino)hexyl]-2-nitrobenzensulfonamide (5624) in rabbit plasma. The plasma protein precipitation and sample preparation was achieved by using acetonitrile, followed by organic phase evaporation to dryness and the residue reconstitution in the mobile phase. The 5624 recovery from the plasma was about 90%. Chromatography was performed on a C18 column using a gradient of acetonitrile in water as a mobile phase. A chemically related compound, N-[6-(imidazo[1,2-d][1,2,4]thiadiazol-3-ylamino)hexyl]naphthalene-1-sulfonamide (5422), was used as an internal standard. Limit of detection (LOD), based on signal to noise ratio>3, was 0.2 microM (on-column amount of about 7 ng), while limit of quantification (LOQ), based on signal to noise ratio>10, was 0.5 microM (on-column amount of about 20 ng). The plasma samples for the PK study were collected at defined time points during and after 5624 slow intravenous infusion (25 mg/kg) to male White New Zealand rabbits and analyzed by RP-HPLC method. The PK parameters, such as half-life, volume of distribution, total clearance, elimination rate constant etc., were determined. The PK profile of 5624 offered insights in the design and development of additional new compounds, derivatives of 1,2,4-thiadiazole, with desired PK properties.

Discovery of thiadiazoles as a novel structural class of potent and selective PDE7 inhibitors. Part 2: Metabolism-directed optimization studies towards orally bioavailable derivatives

The synthesis and optimization of pharmacokinetic parameters of structurally novel small PDE7 inhibitors is discussed.

KC 12291: an atypical sodium channel blocker with myocardial antiischemic properties

KC 12291 was designed as a voltage-gated sodium channel (VGSC) blocker with cardioprotective properties. KC 12291 has moderate inhibitory effects on peak (or rapid) Na+ current, and markedly reduces sustained (or slowly or non-inactivating) Na+ current. This distinguishes KC 12291 from conventional VGSC blockers such as local anesthetics or antiarrhythmics, which have little or no cardioprotective properties. Since VGSCs represent the main pathway for ischemic Na+ loading by failing to inactivate fully, KC 12291 exerts pronounced antiischemic activity principally by reducing the amplitude of sustained Na+ current. In isolated atria and Langendorff-perfused hearts, KC 12291 inhibits diastolic contracture, renowned for its resistance to pharmacological inhibition, reduces ischemic Na+ loading and preserves cardiac energy status. KC 12291 exerts oral antiischemic activity in vivo in the absence of major hemodynamic effects. Cardiac VGSC blockers such as KC 12291, which block cardiac VGSCs in atypical fashion by effectively inhibiting the sustained component of Na+ current, represent, therefore, promising potential antiischemic and cardioprotective drugs.

Plasma kinetics and efficacy of oral megazol treatment in Trypanosoma brucei brucei-infected sheep

Experimentally infected sheep have been previously developed as an animal model of trypanosomosis. We used this model to test the efficacy of megazol on eleven Trypanosoma brucei brucei-infected sheep. When parasites were found in blood on day 11 post-infection, megazol was orally administered at a single dose of 40 or 80mg/kg. After a transient aparasitaemic period, all animals except two relapsed starting at day 2 post-treatment, which were considerated as cured on day 150 post-treatment and showed no relapse after a follow-up period of 270 days. In order to understand the high failure of megazol treatment to cure animals, a kinetic study was carried out. Plasma concentrations of megazol determined, by reverse-phase high-performance liquid chromatography at 8h post-treatment in these animals, were lowered, suggesting slow megazol absorption, except in cured animals. However, megazol plasma profiles in uninfected sheep after a single oral dose of megazol showed a fast megazol lowered absorption associated with a short plasma half-life of drug. Inter-individual variation of megazol pharmacokinetic properties was also observed. These findings suggested that the high failure rates of megazol treatment were related to poor drug availability after oral administration in sheep. In conclusion, megazol could cure sheep with T. b. brucei infection but oral administration was not an effective route.

Synthesis and evaluation of iodinated TZTP-derivatives as potential radioligands for imaging of muscarinic M2 receptors with SPET

A series of iodinated thiadiazolyltetrahydro-1-methyl-pyridine (TZTP) compounds was synthesized and evaluated in vitro and in vivo as potential radioligands for imaging of the muscarinic M2 receptor subtype with SPET. One of these compounds, 5-(E)-iodopentenylthio-TZTP, has high in vitro affinity (Ki = 4.9 nM) and moderate selectivity for the muscarinic M2 receptor subtype. Although the uptake pattern in the biodistribution studies in rats is consistent with muscarinic M2 receptor disribution, specific in vivo binding to these receptors could not be demonstrated. The usefulness of this tracer in human SPET imaging may therefore be limited.

Effect of nanonization on absorption of 301029: ex vivo and in vivo pharmacokinetic correlations determined by liquid chromatography/mass spectrometry

PURPOSE

To compare Caco-2 monolayer permeability and in vivo bioavailability of microparticle with nanoparticle 301029, a thiadiazole derivative, and to determine whether nanonization could improve oral bioavailability of the poorly soluble compound.

METHODS

The mean particle size of 301029 was reduced from 7 microm to 280 nm by pearl milling. In the ex vivo assay, both microparticle and nanoparticle 301029 at the same concentration were separately added to apical side and were collected from basolateral side of Caco-2 monolayer. In the bioavailability study, the two particle sizes of 301029 were orally administered to rats, respectively, and blood samples were collected. Nanoparticle 301029 in culture medium and rat serum was detected by a liquid chomatography-mass spectrometer (LC/MS) coupled with atmospheric pressure chemical ionization (APCI).

RESULTS

Permeability rate and permeated amounts of nanoparticle 301029 across the Caco-2 monolayer were about four times higher than those of microparticle 301029. In a pharmacokinetic study, nanoparticle 301029 showed Tmax about 1 h, whereas the microparticle 301029 showed Tmax at 4 h. The Cmax and AUC of nanoparticle 301029 were 3- to 4-fold greater than those of microparticle 301029, resulting in a significant increase in oral bioavailability of 301029 as compared with microparticle 301029. The ex vivo permeability and in vivo pharmacokinetic data indicate that nanoparticle formulation improves both absorption rate and absorption extent of the poorly soluble drug.

CONCLUSIONS

Nanoparticle formulation enhances both Caco-2 monolayer permeability and rat oral bioavailability of the poorly soluble 301029. The result also demonstrates a close correlation between ex vivo Caco-2 permeability model and in vivo gastrointestinal absorption.

Liquid chromatography-mass spectrometry assay of a thiadiazole derivative in mice: application to pharmacokinetic studies

Modern atmospheric pressure ionization (API) ion-trap mass spectrometry in connection with fast chromatographic separations using a short narrow-bore C8 column was developed to determine 5-phenyl-3-thioureido-1,2,4-thiadiazole (301029), a novel virus inhibitor in serum. Both 301029 and an internal standard (I.S.) were separated from serum samples by acetonitrile deproteinization and extraction without time-consuming reconstitution. The chromatographic separation was achieved on a C8 reversed-phase narrow-bore column using acetonitrile-water-acetic acid (90:10:0.01, v/v/v) as a mobile phase. The mass spectrometric analysis was performed by atmospheric pressure chemical ionization (APCI) mode with positive ion detection. Single ion monitoring (SIM) scan mode of m/z 237 and 158 was used to quantitatively determine 301029 and I.S., respectively. The low limit of quantitation was 25 ng/ml. The assay exhibited a linear range of 25-2500 ng/ml. Recovery from serum proved to be 100-113%. The precision (C.V.) and accuracy (RE) of the method were 2-12% and 94-112%, respectively. The present method was applied to determine the pharmacokinetic parameters of 301029 following oral administration of the agent to mice at 5 g/kg. The results revealed that the elimination half-life of 301029 was 413 min and the area under serum concentration-time curve was 354 microg/ml/min.

Persistence and translocation of a benzothiadiazole derivative in tomato plants in relation to systemic acquired resistance against Pseudomonas syringae pv tomato

A reproducible and accurate procedure, based on HPLC analysis, has been developed to determine simultaneously acibenzolar-S-methyl (CGA 245 704) and its acid derivative (CGA 210 007) in tomato leaves. The limit of detection and quantification of the method are 0.015 and 0.15 mg litre-1 for CGA 245 704 and 0.030 and 0.30 mg litre-1 for CGA 210 007. In tomato plants treated with 250 microM CGA 245 704, it was found that the inducer rapidly translocates from treated leaves (cotyledons, 1st and 2nd) to untreated leaves (3rd to 5th), with the maximum translocation (40% of the total quantity found) occurring 8 h after the treatment. CGA 245 704 residues decreased as time elapsed in both treated and untreated tomato leaves, reaching negligible values 72 h after treatment. The acid derivative, CGA 210 007, was formed in tomato plants as early as 2 h after CGA 245 704 treatment, albeit only in the treated leaves. CGA 210 007 residues decreased in treated tomato leaves with a trend similar to that observed for CGA 245 704. Treatment of tomato plants with CGA 245 704 or CGA 210 007 at 250 microM systemically protected the plants against Pseudomonas syringae pv tomato attacks, the causal agent of bacterial speak disease. Evidence of this were reductions in the degree of infection, the bacterial lesion diameter and the bacterial growth in planta. Since neither CGA 245 704 nor CGA 210 007 inhibited bacterial growth in vitro and the protection against bacterial speak of tomato was observed when the two compounds were completely degraded, the protection must be due to the activation of the plant's defence mechanisms.

Uptake and mode of action of drugs used against sleeping sickness

Sleeping sickness is resurgent in Africa. Adverse side-effects and drug-resistance are undermining the few drugs currently licensed for use against this disease, which is caused by parasitic protozoa of the Trypanosoma brucei group. Pentamidine and suramin are used before parasites become manifest in the central nervous system, after which the organic arsenical melarsoprol is used. Eflornithine is also useful in late-stage disease. A mode of action has been elucidated only for the ornithine decarboxylase inhibitor eflornithine. Both uptake and potential intracellular targets need to be considered when contemplating modes of action. The melaminophenyl arsenicals are accumulated via an unusual amino-purine transporter termed P2, which also seems to have a role in the uptake of the diamidine class of drugs to which pentamidine belongs. Since loss of this transporter leads to drug-resistance, other uptake mechanisms also need to be considered in generating novel trypanocides. Some nitroheterocyclic drugs have prolific activity against trypanosomes, although the fact that they are mutagenic in Ames' tests is acting as a barrier to further development. New drugs are urgently needed and the advent of genome sequencing and target validation using genetic modification will hopefully accelerate this process.

Pharmacokinetics, metabolism and excretion of megazol in a Trypanosoma brucei gambiense primate model of human African trypanosomiasis. Preliminary study

The pharmacokinetics of megazol (2-amino-5-(1-methyl-5-nitro-2-imidazolyl)-1,3,4-thiadiazol, CAS 19622-55-0) was investigated after a 100 mg/kg oral administration to six primates infected with Trypanosoma brucei gambiense. The plasma levels of megazol were between 0.2 microgram/ml and 46 micrograms/ml 24 h after dosing in all animals. In animals with prolonged infection, megazol absorption was accelerated (Tmax was 4 h compared with 8 h, for day 53 and day 39 post inoculation) but the amount absorbed was not modified. The megazol concentrations in the cerebrospinal fluid represented between 5.5% and 10.6% of the plasma levels at the same times. Unchanged megazol was eliminated predominantly via the kidneys: 46-96% of the ingested dose was recovered in the urine, compared with 0-5% in the faeces. Furthermore, this urinary elimination of megazol was altered in animals with prolonged infections. In the urine, 4 unknown metabolites were observed, unchanged megazol was characterized by LC-MS/MS. This study indicates that megazol crosses the blood-brain barrier after oral administration. Prolonged infections affect the absorption of megazol and its urinary elimination.

Carbonic anhydrase inhibitors. Synthesis of water-soluble, topically effective, intraocular pressure-lowering aromatic/heterocyclic sulfonamides containing cationic or anionic moieties: is the tail more important than the ring?

Reaction of several aromatic/heterocyclic sulfonamides containing a free amino, imino, hydrazino, or hydroxyl group, with 2, 3-pyridinedicarboxylic anhydride or 2,6-pyridinedicarboxylic acid in the presence of carbodiimide derivatives, afforded two series of water-soluble (as hydrochloride, triflate, or carboxylate salts) compounds. The new derivatives were assayed as inhibitors of the zinc enzyme carbonic anhydrase (CA) and more precisely of three of its isozymes, CA I, II (cytosolic forms), and IV (membrane-bound form), involved in important physiological processes. Efficient inhibition was observed against all three isozymes, but especially against CA II and IV (in nanomolar range), the two isozymes known to play a critical role in aqueous humor secretion within the ciliary processes of the eye. Some of the best inhibitors synthesized were applied as 2% water solutions directly into the eye of normotensive and glaucomatous albino rabbits. Very strong and long-lasting intraocular pressure (IOP) lowering was observed with many of them. This result prompted us to reanalyze the synthetic work done by other groups for the design of water-soluble, topically effective antiglaucoma sulfonamides. According to these researchers, the IOP-lowering effect is due to the intrinsic nature of the specific heterocyclic sulfonamide considered, among which the thienothiopyran-2-sulfonamide derivatives represent the best-studied case. Indeed, the first agents developed for topical application, such as dorzolamide, are derivatives of this ring system. To prove that the tail (in this case the pyridinecarboxylic moieties) conferring water solubility to a sulfonamide CA inhibitor is more important than the ring to which the sulfonamido group is grafted, we also prepared dorzolamide derivatives incorporating such moieties. These new compounds possess good water solubility as hydrochloride or carboxylate salts, balanced by a relatively modest lipid solubility. They are strong CA II inhibitors and are able to lower IOP in experimental animals more than the parent derivatives. Our conclusion is that the tail conferring water solubility to such an enzyme inhibitor is more important for topical activity as an antiglaucoma drug, than the heterocyclic/aromatic ring to which the sulfonamido moiety is grafted.

1-(1,2,5-Thiadiazol-4-yl)-4-azatricyclo[2.2.1.0(2,6)]heptanes as new potent muscarinic M1 agonists: structure-activity relationship for 3-aryl-2-propyn-1-yloxy and 3-aryl-2-propyn-1-ylthio derivatives

Two new series of 1-(1,2,5-thiadiazol-4-yl)-4-azatricyclo[2.2.1.0(2, 6)]heptanes were synthesized and evaluated for their in vitro activity in cell lines transfected with either the human M1 or M2 receptor. 3-Phenyl-2-propyn-1-yloxy and -1-ylthio analogues substituted with halogen in the meta position showed high functional potency, efficacy, and selectivity toward the M1 receptor subtype. A quite unique functional M1 receptor selectivity was observed for compounds 8b, 8d, 8f, 9b, 9d, and 9f. Bioavailability studies in rats indicated an oral bioavailability of about 20-30%, with the N-oxide as the only detected metabolite.

Pharmacokinetics, metabolism and excretion of megazol, a new potent trypanocidal drug in animals

The pharmacokinetics of megazol (CAS 19622-55-0) was investigated after intraperitoneal and oral administration of the drug (80 mg/kg) to mice. The plasma levels were significantly higher after oral administration of drug than after intraperitoneal route (33.8 micrograms/ml compared with 19.0 micrograms/ml for Cmax, 158714 micrograms.h/l compared with 96057 micrograms.h/l for AUC). When suramin (CAS 145-63-1) was administered 24 h before oral administration of megazol, megazol absorption was accelerated (2 h compared with 4 h for Tmax) but the amount absorbed was lower (19.9 micrograms/ml compared with 33.8 micrograms/ml for Cmax and 95547 micrograms.h/l vs 158714 micrograms.h/l for AUC). In the infected mice previously treated with suramin, all estimated pharmacokinetic parameters of plasma megazol were significantly modified, in particularly an increase in the apparent volume of distribution (5.6 l/kg compared with 0.9 l/kg) with a prolongation of the elimination half-life (3 h compared with 0.7 h) of megazol. Excretion of the total radioactivity of megazol was also evaluated after oral administration of 3H-megazol to rats. Total radioactivity was eliminated predominantly via the urinary route (80%) vs. 10.5% in the faeces, 9.5% remaining in the body 8 days after dosing. When unlabelled megazol was orally administered to rats with absence or presence of suramin, megazol recovered in urine and faeces 72 h dosing was: 55.7%/2% vs 20.6%/1.6%, respectively. In the urine, unchanged megazol was present as characterized by LC-MS/MS as well as 4 unknown metabolites. This study indicates that suramin significantly affects the pharmacokinetics of megazol and its elimination.

Enzymatic reduction studies of nitroheterocycles

The nitroimidazole derivative Megazol is a highly active compound used against several strains of Trypanosoma cruzi, the causative agent of Chagas' disease (American trypanomiasis). With the aim of gaining an insight into the probable mode of action, the interaction of Megazol with different redox enzymes was studied in comparison to that of Nifurtimox and Metronidazole. The three nitroaromatic compounds are reduced by L-lactate cytochrome c-reductase, adrenodoxin reductase, and NADPH:cytochrome P-450 reductase (EC 1.6.2.4), the efficiencies of the enzymatic reductions being roughly related to the reduction potentials of these pseudo-substrates. As the enzyme responsible for the reduction of Megazol within the parasite has not yet been identified, the nitroimidazole was assayed with T. cruzi lipoamide dehydrogenase and trypanothione reductase. Megazol did not inhibit the physiological reactions but proved to be a weak substrate of both flavoenzymes. The single electron reduction of the compound by NADPH:cytochrome P-450 reductase, by rat liver as well as by trypanosome microsomes was confirmed by ESR experiments. As shown here, Megazol interferes with the oxygen metabolism of the parasite, but its extra activity when compared to Nifurtimox may be related to other features not yet identified.

Quantitative whole-body autoradiography in pregnant rabbits to determine fetal exposure of potential teratogenic compounds

Whole-body autoradiography (WBA) allows the determination of sites of accumulation and differential distribution of radiolabeled compounds within organs. WBA is routinely conducted in pregnant rats to evaluate placental transfer and fetal distribution of potential developmental toxins. This technique has recently been adapted to evaluate tissue distribution in the pregnant rabbit, which may be a more appropriate model for some pharmaceutical candidates. A preliminary WBA study was conducted on New Zealand white (NZW) rabbits at gestation day 18, 1 h following a single oral dose of 14C-glucose. The purpose of this study was to validate the use of WBA techniques in assessing the placental transfer of compounds in pregnant rabbits. Antiviral compound LY217896 sodium demonstrated developmental toxicity in the pregnant NZW rabbit following multiple oral doses of 10 mg/kg on gestation days 6 through 18. WBA techniques were used to determine the distribution of radiocarbon 30 minutes following a single oral 10-mg/kg dose of 14C-LY217896 sodium in pregnant NZW rabbits on gestation day 18.

Simple high-performance liquid chromatographic method to analyse megazol in human and rat plasma

A simple and sensitive high-performance liquid chromatographic method has been developed to measure megazol in human plasma. The method was optimized and validated according to the Washington Concensus Conference on the Validation of Analytical Methods (V.P. Shah et al., Eur. J. Drug Metab. Pharmacokinet., 15 (1991) 249). The criteria of complete validation were specificity, linearity, precision, analytical recovery, dilution and stability. It involved extraction of the plasma with dichloromethane, followed by reversed-phase high-performance liquid chromatography using a Kromasil C8 column and UV detection at 360 nm. The retention times of the internal standard (tinidazol) and megazol were 6.10 and 9.60 min, respectively. The standard curve was linear from 2 ng ml-1 (limit of quantification) to 2000 ng ml-1. The coefficients of variation for all the criteria of validation were less than 6%; 85 to 92% extraction efficiencies were obtained. Megazol was stable during the storage period (one month at -20 degrees C) in plasma and for two months at 25 degrees C in standard solution. The method was tested by measuring the plasma concentration following oral administration to rat and was shown to be suitable for pharmacokinetic studies.

Thiadiazole derivatives: highly potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) replications in vitro

We have recently reported that thiadiazole (TDA) derivatives are highly potent inhibitors of human immunodeficiency virus type 1 (HIV-1) replication. These compounds belong to the family of nonnucleoside reverse transcriptase inhibitors (NNRTIs). In an attempt to develop more effective and pharmacologically favorable compounds, novel TDA derivatives have been synthesized and examined for their anti-HIV-1 activity in vitro. Among them, RD4-2217 was found to be the most potent inhibitor of HIV-1 replication. It inhibited replication of the HTLV-IIIB strain in MT-4 cells at a concentration of 6 nM. RD4-2217 was also inhibitory to clinical isolates and zidovudine-resistant mutants of HIV-1. The combination of RD4-2217 with zidovudine or the protease inhibitor A-75925 synergistically inhibited HIV-1 replication. Studies on the emergence of drug-resistant mutants revealed that, although much higher concentrations (1-10 microM) were required, RD4-2217 completely suppressed the breakthrough of HIV-1 in the supernatants during long-term culturing of infected cells. Furthermore, RD4-2217 at low concentrations (10 or 100 nM), in combination with zidovudine, also completely inhibited viral breakthrough. In addition, RD4-2217 had lower lipophilicity and improved protein binding as compared to its congener RD4-2024 and loviride. These results suggest that RD4-2217, one of the TDA derivatives, is worth pursuing as a candidate drug for the treatment of HIV-1 infections.

PET study of the M1-agonists [11C]xanomeline and [11C]butylthio-TZTP in monkey and man

Xanomeline, a substituted TZTP, is a new M1 selective muscarinic agonist in clinical trials for Alzheimer's disease. The brain uptake of [11C]xanomeline and the analog [11C]butylthio-TZTP was examined by positron emission tomography (PET). Radioactivity accumulated most markedly in the neocortex and the striatum. Pharmacological characterization in vitro and in cynomolgus monkeys in vivo by PET indicated specific [11C]butylthio-TZTP binding to muscarinic receptors and to sigma-1 recognition sites. More than 5% of the radioactivity was in the human brain 5 min after i.v. injection of [11C]xamomeline or [11C]butylthio-TZTP. This high brain uptake may be clinically advantageous in the sense that substituted TZTP may induce central muscarinic agonist effects at a dose level for which there is a low risk of peripheral side-effects.

High-performance liquid chromatographic assay for xanomeline, a specific M-1 agonist, and its metabolite in human plasma

A reversed-phase high-performance liquid chromatographic assay (HPLC) was utilized for monitoring xanomeline (LY246708/NNC 11-0232) and a metabolite, desmethylxanomeline, in human plasma. Xanomeline, desmethylxanomeline and internal standard were extracted from plasm with hexane at basic pH. The organic solvent extract was evaporated to dryness with nitrogen and the dried residue was reconstituted with 0.2 M HCl-methanol (50:50, v/v). A Zorbax CN 150 x 4.6 mm I.D., 5-microns column and mobile phase consisting of 0.5% (5 ml/l) triethylamine (TEA) adjusted to pH 3.0 with concentrated orthophosphoric acid-tetrahydrofuran (THF) (70:30, v/v) produced consistent resolution of analytes from endogenous co-extracted plasma components. Column effluent was monitored at 296 nm/0.008 a.u.f.s. and the assay limit of quantification was 1.5 ng/ml. A linear response of 1.5 to 20 ng/ml was sufficient to monitor plasma drug/metabolite concentrations during clinical trials. HPLC assay validation as well as routine assay quality control (QC) samples indicated assay precision/accuracy was better than +/- 15%.

Determination of xanomeline (LY246708 tartrate), an investigational agent for the treatment of Alzheimer's disease, in rat and monkey plasma by capillary gas chromatography with nitrogen-phosphorus detection

A GC method is described for the determination of xanomeline (LY246708 tartrate) and selected metabolites in rat and monkey plasma. The analytes, including an internal standard, were extracted from plasma at basic pH with hexane. The organic extract was evaporated to dryness and the residue was reconstituted in hexane. The analytes were separated from metabolites and endogenous substances using a DB1701 capillary column. The analytes were detected using nitrogen-phosphorus detection (NPD). The limit of quantitation was determined to be 8 ng/ml, and the response was linear from 8 to 800 ng/ml. The method has been successfully applied to rat and monkey samples pursuant to the development of xanomeline as an agent for the symptomatic treatment of Alzheimer's disease.

Uptake and biodisposition of 2-ylcyanamide-1,3,4-thiadiazole (LY217896) by red blood cells

In man, 14C-2-ylcyanamide-1 3 4-thiadiazole (LY217896) accumulates into red blood cells (RBCs) where it is rapidly metabolized. Both in man and ex vivo, within a few hours of administration of 14C-LY217896 at least two intracellular metabolites were detected within the RBCs using HPLC. These metabolites were never detected extracellularly. After 24 h no detectable radioactivity was found in the plasma and all the radioactivity was detected within the cellular fraction. All radioactivity was identified as a single peak within the RBCs, indicating the metabolite(s) to be highly polar compared to LY217896. Parent LY217896 was never detected within the RBCs at any time point, suggesting transport, either by diffusion or a carrier mediated mechanism, was the rate limiting step. Due to the nature of the preparation it was impossible to separately characterize uptake and biotransformation. Nevertheless, uptake/biotransformation was found to be temperature sensitive, sodium independent, and energy dependent. Both niacin and vitamin B6, but not nicotinamide, competitively blocked the uptake and subsequent intracellular metabolism of LY217896.

Determination of xanomeline in human plasma by ion-spray tandem mass spectrometry

Xanomeline is a muscarinic receptor agonist currently in phase II clinical trials for the treatment of Alzheimer's disease. A fast, sensitive and specific assay has been developed to determine xanomeline plasma concentrations using ion-spray tandem mass spectrometry. Xanomeline and a structural analog, LY282122, were extracted from basifed plasma into hexane. The dried hexane extracts were reconstituted and injected onto a 10 x 1 mm C18 reversed-phase column. A mobile phase of 33 mM ammonium acetate and 0.33% acetic acid in 30/70 (v/v) water-acetonitrile was pumped through the column at 50 microliters min-1. The mobile phase eluant was introduced directly into the ion-spray interface. The mass spectrometer was operated in the positive ion mode for specific detection of the product ions of xanomeline and the internal standard. The method has a linear range of 0.075-5.0 ng xanomeline per milliliter of plasma. Sample run times were 2.5 min from one injection to the next.

Neurochemical effects of the M1 muscarinic agonist xanomeline (LY246708/NNC11-0232)

Xanomeline [3(3-hexyloxy-1,2,5-thiadiazol-4-yl)-1,2,5,6-tetrahydro-1-me thylpyridine)] was evaluated in vivo in rat brain for effects on neurotransmitter turnover and inhibition of ex vivo binding of muscarinic radioligands. Xanomeline produced dose-related increases in the metabolite of dopamine, dihydroxyphenylacetic acid (DOPAC), in striatum. The increases in striatal DOPAC levels produced by xanomeline were antagonized by the relatively selective M1 antagonist trihexyphenidyl, suggesting that xanomeline interacts with M1 heteroreceptors on dopamine nerve terminals. Xanomeline produced small increases in striatal acetylcholine levels and did not antagonize the large increases in acetylcholine produced by the nonselective muscarinic agonist oxotremorine, indicating that xanomeline did not block M2 autoreceptors. Xanomeline inhibited ex vivo binding of muscarinic radioligands to homogenates of brain and the inhibition of ex vivo binding occurred in the same dose range as increases in DOPAC levels. Xanomeline did not appreciably induce salivation or antagonize oxotremorine-induced salivation indicating that xanomeline does not interact with M3 receptors. The effects of xanomeline on ex vivo binding and DOPAC levels lasted for about 3 hr and were evident after oral administration. An analog of xanomeline with similar in vivo effects did not inhibit acetylcholinesterase or choline acetyltransferase and inhibited choline uptake only at concentrations much higher than those required to inhibit binding. These data indicate xanomeline is selective agonist for M1 over M2 and M3 receptors in vivo in rat. It is not known whether xanomeline interacts with m4 or m5 receptors in vivo.

Pharmacokinetics, acid-base balance and intraocular pressure effects of ethyloxaloylazolamide--a novel topically active carbonic anhydrase inhibitor

Studies evaluated a novel series of biscarbonylamides of 2-amino-1,3,4-thiadiazole-5-sulfonamide (2-ATS) for topical use as ocular hypotensive carbonic anhydrase inhibitors (CAI). Transcorneal accession rate constants (k(in)) for ethyloxaloylazolamide (EtOxAz), ethylsuccinylazolamide (EtSuxAz) and ethyladipoylazolamide (EtAdipAz), and activity against carbonic anhydrase (CA) were determined in vitro by an enzymatic assay and High Performance Liquid Chromatography (HPLC). The ocular hypotensive effect was measured by pneumatonometry on conscious normotensive New Zealand White (NZW) rabbits, using masked, randomly assigned paired-eye design for treatment vs. control. At various time points following treatment, aqueous humor, ciliary processes and corneal buttons were collected and assayed for drug concentrations using enzymatic assay and HPLC. Transcorneal accession rates for the novel compounds were 1.5 to 18 times that of the parent compound, acetazolamide (Actz). The activity factor for EtOxAz was 72.8 x 10(3) hr-1 of 23 times that of Actz. The activity factors for EtSuxAz and EtAdipAz were 6.8 and 1.1 x 10(3) hr-1, respectively. Subcutaneous administration of EtOxAz. EtSuxAz, and EtAdipAz, in 225 mumol kg-1 concentrations, induced a significant decrease in the intraocular pressure (IOP) at 1 hr post injection of 4, 5.8 and 6 mmHg for EtOxAz, EtSuxAz and EtAdipAz, respectively (P < 0.05 for each). Topical application of 75 mM EtOxAz lowered the IOP by 3.0 mmHg (P < 0.05). This effect was maximal after 60 min and persisted for at least 5 hr. EtSuxAz and EtAdipAz did not alter the IOP significantly when given topically. Subcutaneous administration of the three compounds was associated with acidosis (pH as low as 7.21). Topical application did not cause any changes in the acid-base balance. There was a direct correlation between the amount of drug delivered to the ciliary process and the magnitude of ocular hypotensive effect. Following topical application EtOxAz reached the ciliary epithelium in concentrations sufficient to inhibit more than 99.95% of the ciliary carbonic anhydrase (> 8 microM), while plasma drug concentrations were below the limit of detection by the assay (< 0.2 microM). Within the first hour after topical application, half of the EtOxAz was eliminated from the anterior uvea. In summary, EtOxAz is a topically effective CAI. Structural modifications of thiadiazole sulfonamides, with the increase of both water and lipid solubilities, improved the transcorneal accession while preserving sufficient CA inhibitory activity, resulting in a significant IOP decrease following topical application of EtOxAz.(ABSTRACT TRUNCATED AT 250 WORDS)

Subacute and subchronic toxicology studies of CI-986, a novel anti-inflammatory compound

CI-986 (5-[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-1,3,4-thiadiazole-2(3H)- thione-2-hydroxy-N,N,N-trimethylethanaminium salt) is a novel anti-inflammatory compound classified as a dual inhibitor of cyclooxygenase and 5-lipoxygenase. Studies were undertaken to characterize the preclinical toxicology of the compound. CI-986 was administered to rats for 2 weeks (0, 50, 250, 750, and 1500 mg/kg) or 13 weeks (0, 20, 250, 500, and 1000 mg/kg), dogs for 2 weeks (0, 50, 150, and 500 mg/kg) or 13 weeks (0, 20, 100, and 200 mg/kg), and to monkeys for 2 weeks (0, 50, 250, and 1000 mg/kg). No drug-related deaths resulted. Mild clinical signs of toxicity were noted in rats given doses of 250 mg/kg and above. Drug-related emesis and diarrhea were absent at the low dose in the dog and monkey but increased in incidence and severity at higher doses. Severe clinical signs in monkeys (emesis and diarrhea) necessitated the lowering of the top dose to 500 mg/kg/day (administered b.i.d.) during the second week of the monkey study. Slight decreases (< 23%) in serum protein and/or albumin were noted in all studies at the higher doses. A dose-related increase in alkaline phosphatase was noted in both dog studies, with no other drug-related effect on clinical pathology parameters. A gastric ulcer occurred in one rat administered 500 mg/kg CI-986 for 13 weeks. Gastrointestinal ulcers were not noted at any other dose in rats or at any dose in dogs or monkeys. A dose-related eosinophilia of glandular stomach submucosa was noted in rats after 2 and 13 weeks of drug administration but not in dogs or monkeys. In the 2-week rat study, mean combined sex plasma drug concentrations monitored 2 hr after dose on Day 14 were 0.59, 1.10, 2.64, and 3.43 micrograms/ml for the 50, 250, 750, and 1,500 mg/kg dose groups, respectively. In the 2-week dog studies, maximum plasma drug concentrations on Day 10 or Day 11 were achieved within 2 hr of dose with mean combined sex Cmax values of 0.73, 2.05, and 2.62 micrograms/ml for the 50, 250, and 750 mg/kg groups, respectively. Hepatic microsomal induction characterized by increased microsomal protein, increased microsomal cytochrome P450 content, and increased p-nitroanisole O-demethylation activity was noted in dogs and monkeys but not rats. CI-986 was well tolerated in rats and dogs at the doses employed and in monkeys at doses up to 500 mg/kg (b.i.d.).(ABSTRACT TRUNCATED AT 250 WORDS)

Sensitive liquid chromatographic method for the determination of a specific M1 agonist, LY246708, an investigational agent with potential for the treatment of Alzheimer's disease, in human plasma

A reversed-phase HPLC method is reported for the determination of a new M1 agonist, LY246708, in human plasma. The compound and an internal standard were extracted from plasma with hexane at basic pH. The organic extract was evaporated to dryness and the residue was reconstituted with mobile phase [0.5% diethylamine (pH 3, adjusted with phosphoric acid)-acetonitrile (70:30, v/v)]. The analytes were separated from endogenous substances on a Zorbax CN column; the effluent was monitored by measuring its absorbance at 296 nm. The limit of quantification was determined at 1.5 ng/ml and the response was linear from 1.5 to 20 ng/ml. Validation studies showed the method to be both repeatable and reproducible. Its robustness was demonstrated by transfer between analytical laboratories and continued use in support of pharmacokinetic studies and therapeutic monitoring of the compound.

Studies of carbonic anhydrase inhibitors: physicochemical properties and bioactivities of new thiadiazole derivatives

A series of thiadiazole derivatives of carbonic anhydrase inhibitors were prepared and their physicochemical properties and pharmacological activities such as corneal permeabilities, inhibition of carbonic anhydrase activities were evaluated. The solubilities and pKa values were determined in varied pH of phosphate buffers at 35 degrees C after equilibrium. Intrinsic solubility and pKa value were calculated from the plot of solubility versus the reciprocal of hydrogen ion concentration. The distribution coefficient was determined in the system of octanol/pH 7.65 phosphate buffer. As a result, the sigma (Hammett constant) and pi (hydrophobic substituent constant) values of substituents were found to be correlated to the logarithm of Ka and partition coefficient. Corneal permeabilities of the analogue were determined in a specially designed diffusion cell using excised rabbit cornea, which ranged from 1.32 x 10(-5) (compound II) to 3.48 x 10(-7) cm/sec (compound VI). Compound with high permeability might be expected to be absorbed well after topical administration into the eye. The methodology of pH-stat was used to determine the inhibition of the carbonic anhydrase activity of the analogue. The IC50 values of the analogue around 10(-8) M as determined were less than that of acetazolamide. The results suggest that the analogue had good pharmacological activity. Finally, an equation for quantitative structure-activity relationship was established for the analogue, which is as follows: [formula: see text]

Biotransformation of the antiviral agent 1,3,4-thiadiazol-2-ylcyanamide (LY217896) and characteristics of a mesoionic ribose metabolite

The biotransformation of the antiinfluenza agent 1,3,4-thiadiazol-2-ylcyanamide (LY217896, I) was studied. In addition to a urea metabolite (II) formed by transformation of the cyanamide functionality, another highly polar metabolite was found in mouse urine and in BSC-1, MDCK, and other cell culture incubations of [14C]LY217896. Using 13C-labeled LY217896 together with NMR and MS techniques, this highly polar metabolite was identified as a ribose derivative (III), which apparently exists in a mesoionic form (i.e. positive and negative charges within the same ring system). It was also found that this ribose is formed from LY217896 and ribose-1-phosphate in a reaction catalyzed by the enzyme purine nucleoside phosphorylase, but that the reverse reaction (cleavage of the ribose) is not observed under the conditions used. When tested in vitro using the same assay as that used to measure the antiviral activity of LY217896, this ribose and the urea metabolite exhibit essentially no activity. The presence of a ribose has been implicated in the activity of antiviral compounds such as ribavirin and anticancer agents like 2-aminothiadiazole and tiazofurin, which are structurally similar to LY217896. These activities have been postulated to involve either mono- or triphosphorylated forms, or NAD-type analogs. Possible implications of the formation of this mesoionic ribose metabolite for the mechanism of antiviral activity of LY217896 are discussed.

Preferential biliary elimination of FPL 63547, a novel inhibitor of angiotensin-converting enzyme, in the rat

1. The route of elimination of FPL 63547, a novel inhibitor of angiotensin-converting enzyme (ACE), has been investigated in the anaesthetized rat. Comparisons have been made with other ACE inhibitors. 2. Bile and urine samples were collected over a 5 hour period following a single i.v. dose of ACE inhibitor (2 mumol kg-1). Samples were bioassayed for ACE inhibitory activity using affinity-purified rabbit lung ACE and the amounts of the active form of inhibitor present in each sample were calculated by comparison with a standard curve. 3. FPL 63547 was rapidly and extensively excreted as the diacid in the bile but appeared in the urine in negligible amounts. The bile:urine ratio was 21.4:1 indicating a marked preference for the biliary route. A similar elimination profile was observed when the compound was dosed in its active form (FPL 63547 diacid), 87.9% of which was found in the bile over the 5 h collection period, with a bile: urine ratio of 14.6:1. 4. The marked preference of FPL 63547 for biliary elimination was not shared by the other ACE inhibitors tested in this study. Lisinopril demonstrated the opposite pattern, being excreted almost exclusively by the kidney (bile:urine ratio 0.06:1). Enalapril was eliminated in approximately equal amounts in bile and urine (ratio 0.7:1) while spirapril diacid showed a slight preference for the bile (ratio 2.6:1). 5. The physical chemical properties of FPL 63547 diacid may be responsible for its unusual preference for biliary elimination. In particular, the amphipathic character and strong acid functionality of the compound are thought to favour transport into the bile. 6. Elimination by the biliary route will be preferred in patients whose renal function is impaired as a result of disease or age. In such patients the elimination of renally-excreted ACE inhibitors is known to be compromised, resulting in compound accumulation and the need for closer monitoring. Therefore, the elimination profile of FPL 63547, if confirmed in man, may prove to be clinically advantageous.

Inhibition of factor XIIIa in a canine model of coronary thrombosis: effect on reperfusion and acute reocclusion after recombinant tissue-type plasminogen activator

The effect of inhibition of factor XIIIa with 2-(l-acetonylthio)-5-methylthiazolo[2,3-b]1,3,4-thiadiazo lium perchlorate (L-722,151) on coronary thrombolysis and reocclusion was studied in an acute dog model of electrically induced coronary thrombosis. L-722,151 (0.1 mg/kg/min intravenously [IV] or placebo was administered 15 minutes before current initiation (150 microA) and for the duration of the experiment (270 minutes). Fifteen minutes after thrombus formation, heparin (300 U/kg, IV) was administered, followed 45 minutes later by recombinant tissue-type plasminogen activator (tPA) (10 micrograms/kg/min, IV for 90 minutes). Placebo-treated animals thrombosed at 48.9 +/- 8.1 minutes (mean +/- SEM) and reperfused in response to tPA at 49.1 +/- 9.3 minutes. L-722,151 pretreated animals thrombosed at 44.4 +/- 9.7 minutes and reperfused in response to tPA at 16.4 +/- 2.8 minutes (P less than .05 v vehicle). Furthermore, residual thrombus mass was reduced by L-722,151 from 6.9 +/- 1.9 mg in placebo-treated animals to 1.7 +/- 0.6 mg (P less than .05 v vehicle). Acute reocclusion occurred in 86% of placebo and in 75% of L-722,151-treated animals. The incidence of tPA-induced reperfusion in L-722,151-treated dogs was 100% (8 of 8), whereas only 70% (7 of 10) of placebo-treated dogs reperfused. These results demonstrate that pretreatment with L-722,151 hastens reperfusion time threefold and reduces residual thrombus mass. These effects occurred with no change in systemic blood pressure in response to L-722,151. When L-722,151 was administered 15 minutes after thrombus formation in a separate group of dogs (n = 5), no beneficial effect on thrombolysis time or thrombus mass was observed. Thus, the specific factor XIIIa catalyzed crosslinking reaction(s), which may determine(s) resistance to plasmin-mediated fibrin degradation, occur(s) rapidly. Inhibition of this crosslinking by pretreatment with L-722,151 promotes tPA-induced thrombolysis.