Large neutral amino acid transporter enables brain drug delivery via prodrugs.

The blood-brain barrier efficiently controls the entry of drug molecules into the brain. We describe a feasible means to achieve carrier-mediated drug transport into the rat brain via the specific, large neutral amino acid transporter (LAT1) by conjugating a model compound to L-tyrosine. A hydrophilic drug, ketoprofen, that is not a substrate for LAT1 was chosen as a model compound. The mechanism and the kinetics of the brain uptake of the prodrug were determined with an in situ rat brain perfusion technique. The brain uptake of the prodrug was found to be concentration-dependent. In addition, a specific LAT1 inhibitor significantly decreased the brain uptake of the prodrug. Therefore, our results reveal for the first time that a drug-substrate conjugate is able to transport drugs into the brain via LAT1.

Development and validation of a gas chromatographic-mass spectrometric method for quantitative determination of perphenazine in rabbit plasma after sublingual administration.

Perphenazine is a phenothiazine-type antipsychotic that is a potential candidate for sublingual administration due to its extensive first-pass metabolism. In this study, a gas chromatographic-mass spectrometric method was developed for quantification of perphenazine in rabbit plasma after sublingual administration. The plasma samples were purified by mixed-mode solid phase extraction with good recovery (>83%). The method was linear (r(2)>0.99) over a range of 2-64 ng/ml, with a lower limit of quantification of 2 ng/ml. The accuracy was 100+/-4%, and the within-day and between-day precisions were <6.8% R.S.D. and <14% R.S.D., respectively. Perphenazine was stable in stock solutions and plasma. The method was successfully applied for analysing perphenazine in plasma after sublingual administration to rabbits.

Quantitative analysis of natural cyclodextrins by high-performance liquid chromatography with pulsed amperometric detection: application to cell permeation study.

Simple HPLC-PAD methods were developed for quantitation of cyclodextrins (CDs) in aqueous matrices from in vitro cell permeation studies. C-18 solid-phase extraction was used for sample pretreatment. Samples were analysed using acetonitrile-water mobile phase with post-column alkalization by 0.5M NaOH. Zorbax SB-Aq (for alpha-CD) and Zorbax SB-Phenyl (for beta-CD and gamma-CD) columns gave excellent peak shape and sufficient resolution of CD to glucose (2.7-3.2). The methods showed good concentration-response relationship (r > or = 0.999), precision (RSD% 0.7-5.1), repeatability (RSD% 3.4-13.7) and accuracy (87-107%). The limits of quantitation were 0.78, 0.46 and 0.52 microg/ml for alpha-CD, beta-CD and gamma-CD (RSD% of 10.6, 8.1 and 16.3, respectively).

Effect of N-betainate and N-piperazine derivatives of chitosan on the paracellular transport of mannitol in Caco-2 cells.

The effects of novel quaternary chitosan derivatives on the paracellular transport of mannitol and cell viability were studied in the Caco-2 cell model. The N-betainate derivative with the degree of substitution of 0.05 was very effective at 1.0% (w/v) concentration. The activity decreased as the degree of substitution increased. The cytotoxicity of N-betainates was rather low. The N-piperazines were at least equally effective as the N-betainates with a similar degree of substitution (>0.15). Most of the N-piperazines did not exert toxic effects on the cell monolayers. Overall, the inverse proportionality between the degree of substitution and activity suggests that an intact chitosan backbone is essential for the bioactivity of chitosan derivatives. The quaternary group does not substitute for the activity of the free amine group. In particular, the N-betainate derivatives of chitosan should contain only the minimum number of substituents required for water solubility.

Synthesis, in vitro and in vivo characterization of novel ethyl dioxy phosphate prodrug of propofol.

A novel ethyl dioxy phosphate prodrug of propofol (3) was synthesized and characterized in vitro and in vivo as safer alternative for phosphonooxymethyl prodrugs. The synthesis of 3 was achieved via vinyl and 1-chloroethyl ether intermediates, followed by addition of phosphate group. Aqueous solubility and chemical stability of 3 was determined in buffer solutions and the bioconversion of 3 to propofol was determined in vitro and in vivo. The results show that 3 greatly enhanced the aqueous solubility of propofol (solubility over 10 mg/mL) and the stability in buffer solution (t1/2=5.2+/-0.2 days at pH 7.4, r.t.) was sufficient for i.v. administration. The enzymatic hydrolysis of 3 to propofol was extremely rapid in vitro (t1/2=21+/-3s) and 3 was readily converted to propofol in vivo in rats. During bioconversion, 3 releases acetaldehyde, a less toxic compound than the formaldehyde released from the phosphonooxymethyl prodrug of propofol (Aquavan), currently undergoing clinical trials. The maximum plasma concentration of propofol, 3.0+/-0.2 microg/mL, was reached within 2.1+/-0.8 min after the i.v. administration of 3. The present study indicates that ethyl dioxy phosphate represents a potentially useful water-soluble prodrug structure suitable for i.v. administration.

Design, synthesis, and in vitro evaluation of carbamate derivatives of 2-benzoxazolyl- and 2-benzothiazolyl-(3-hydroxyphenyl)-methanones as novel fatty acid amide hydrolase inhibitors.

Fatty acid amide hydrolase (FAAH) is an intracellular serine hydrolase, which catalyzes the hydrolysis of the endocannabinoid N-arachidonoylethanolamide to arachidonic acid and ethanolamine. FAAH also hydrolyzes another endocannabinoid, 2-arachidonoylglycerol (2-AG). However, 2-AG has been assumed to be hydrolyzed mainly by monoacylglycerol lipase (MAGL) or a MAGL-like enzyme. Inhibition of FAAH or MAGL activity might lead to beneficial effects in many physiological disorders such as pain, inflammation, and anxiety due to increased endocannabinoid-induced activation of cannabinoid receptors CB1 and CB2. In the present study, a total of 34 novel compounds were designed, synthesized, characterized, and tested against FAAH and MAGL-like enzyme activity. Altogether, 16 compounds were found to inhibit FAAH with half-maximal inhibition concentrations (IC50) between 28 and 380 nM. All the active compounds belong to the structural family of carbamates. Compounds 14 and 18 were found to be the most potent FAAH inhibitors, which may serve as lead structures for novel FAAH inhibitors.

URB754 has no effect on the hydrolysis or signaling capacity of 2-AG in the rat brain.

Previous studies indicate that in brain tissue the endocannabinoid 2-AG is inactivated by monoglyceride lipase (MGL)-catalyzed hydrolysis, and a recent report has indicated that MGL activity could be specifically inhibited by URB754 . In the present study, URB754 failed to inhibit 2-AG hydrolysis in rat brain preparations. In addition, brain cryosections were employed to assess whether URB754 could facilitate the detection of 2-AG-stimulated G protein activity. Nevertheless, whereas pretreatment with PMSF readily allowed detection of 2-AG-stimulated G protein activity, URB754 was ineffective. In contrast to previous claims, brain FAAH activity was also resistant to URB754. Thus, in our hands URB754 was not able to block the endocannabinoid-hydrolyzing enzymes and cannot serve as a lead structure for future development of MGL-specific inhibitors.

Precipitation complexation method produces cannabidiol/beta-cyclodextrin inclusion complex suitable for sublingual administration of cannabidiol.

In the present study, the precipitation complexation method was used to prepare a complex of cannabidiol (CBD) with beta-CD. The effect of beta-CD-complexation on the sublingual absorption of CBD was studied in rabbits. A solid CBD/beta-CD inclusion complex was prepared by precipitation and the effect of complex formation on the dissolution rate of CBD was studied. The absorption of CBD (a 250 microg/kg dose of CBD in all formulations) after sublingual administration of solid CBD/beta-CD complex and ethanolic CBD solution, and after oral administration of ethanolic CBD solution, was studied in vivo in rabbits. The dissolution rate of solid CBD/beta-CD complex in vitro was significantly (p<0.05) higher than that of plain CBD. The absorption of CBD (AUC0-300 min) decreased in the following order: sublingual ethanolic CBD solution (420+/-120 ngxmin/mL; mean+/-SD; n=4)>sublingual solid CBD/beta-CD complex (270+/-120 ngxmin/mL)>oral ethanolic CBD solution (concentrations in plasma below the quantitation limit). The results demonstrate that sublingual administration of a solid CBD/beta-CD complex enhances the absorption of CBD in rabbits when compared to oral administration of ethanolic CBD. Furthermore, the solid CBD/beta-CD complex may provide an alternative formulation for sublingual administration of CBD.

Topical buparvaquone formulations for the treatment of cutaneous leishmaniasis.

As the part of a study to develop buparvaquone (BPQ) formulations for the treatment of cutaneous leishmaniasis, the topical delivery of BPQ and one of its prodrugs from a range of formulations was evaluated. In previous studies, BPQ and its prodrugs were shown to be potent antileishmanials in-vitro, with ED50 values in the nanomolar range. 3-Phosphono-oxymethyl-buparvaquone (3-POM-BPQ) was the most potent antileishmanial and was chosen, together with the parent drug, for further investigation. The ability of the parent and prodrug formulations to cross human and murine skin was tested in-vitro using the Franz diffusion cells. Formulations intended for topical application containing either BPQ or 3-POM-BPQ were developed using excipients that were either acceptable for topical use (GRAS or FDA inactive ingredients) or currently going through the regulatory process. BPQ was shown to penetrate both human epidermal membranes and full thickness BALB/c skin from a range of formulations (gels, emulsions). Similarly, 3-POM-BPQ penetrated full-thickness BALB/c skin from several gel formulations. In-vitro binding studies showed that BPQ bound melanin in a dose-dependent manner and preferably bound to delipidized skin over untreated BALB/c skin (on a weight to weight basis). The results confirm that BPQ and its prodrug 3-POM-BPQ can penetrate the skin from several formulations, making them potentially interesting candidates for further investigation of topical formulations using in-vivo models of cutaneous leishmaniasis.

Fatty acid amide hydrolase inhibitors from virtual screening of the endocannabinoid system.

The endocannabinoid system consists of two cannabinoid receptors (CB1 and CB2), endogenous ligands (endocannabinoids), and the enzymes involved in the metabolism of the endocannabinoids, including fatty acid amide hydrolase (FAAH) and monoglyceride lipase (MGL). In the present study, virtual screening of MGL inhibitors was performed by utilizing a comparative model of the human MGL enzyme. All hit molecules were tested for their potential MGL inhibitory activity, but no compounds were found capable of inhibiting MGL-like enzymatic activity in rat cerebellar membranes. However, these compounds were also tested for their potential FAAH inhibitory activity and five compounds (2-6) inhibiting FAAH were found with IC50 values between 4 and 44 microM. In addition, the hit molecules from the virtual screening of CB2 receptor ligands (reported previously in Salo et al. J. Med. Chem. 2005, 48, 7166) were also tested in our FAAH assay, and four active compounds (7-10) were found with IC50 values between 0.52 and 22 microM. Additionally, compound 7 inhibited MGL-like enzymatic activity with an IC50 value of 31 microM.

Synthesis and SAR studies of 2-oxoquinoline derivatives as CB2 receptor inverse agonists.

The highly CB2 selective cannabinoid receptor inverse agonist, 7-methoxy-2-oxo-8-pentyloxy-1,2-dihydroquinoline-3-carboxylic acid N-benzo[1,3]dioxol-5-ylmethyl)amide (JTE-907; 9b), served as the lead compound for investigating the structure-activity relationships of its analogues and in the search for more potent and effective CB2 receptor inverse agonists. A series of aromatic amides of 7-methoxy-2-oxo-8-pentyloxy-1,2-dihydroquinoline-3-carboxylic acid 6 was synthesized, and the CB2 receptor activities of the compounds were determined by a [35S]GTPgammaS-binding assay using membranes of CHO cells stably transfected with the human CB2 receptor. As a result, all the compounds were defined as full CB2 receptor inverse agonists, and additionally, except for two 3,4-dihydroxyphenylalkylamides, they were found to be equally potent as SR144528.

3D-QSAR studies on cannabinoid CB1 receptor agonists: G-protein activation as biological data.

G-protein activation via the CB1 receptor was determined for a group of various CB1 ligands and utilized as biological activity data in subsequent CoMFA and CoMSIA studies. Both manual techniques and automated docking at CB1 receptor models were used to obtain a common alignment of endocannabinoid and classical cannabinoid derivatives. In the final alignment models, the endocannabinoid headgroup occupies a unique region distinct from the classical cannabinoid structures, supporting the hypothesis that these structurally diverse molecules overlap only partially within the receptor binding site. Both CoMFA and CoMSIA produce statistically significant models based on the manual alignment and a docking alignment at one receptor conformer. Leave-half-out cross-validation and progressive scrambling were successfully used in assessing the predictivity of the QSAR models.

Evaluation of hydroxyimine as cytochrome P450-selective prodrug structure.

Hydroxyimine derivatives of ketoprofen (1) and nabumetone (2) were synthesized and evaluated in vitro and in vivo as cytochrome P450-selective intermediate prodrug structures of ketones. 2 released nabumetone in vitro in the presence of isolated rat and human liver microsomes and in different recombinant human CYP isoforms. Bioconversion of 2 to both nabumetone and its active metabolite, 6-methoxy-2-naphthylacetic acid (6-MNA), was further confirmed in rats in vivo. Results indicate that hydroxyimine is a useful intermediate prodrug structure for ketone drugs.

N,N'-Bisbenzylidenebenzene-1,4-diamines and N,N'-Bisbenzylidenenaphthalene-1,4-diamines as Sirtuin Type 2 (SIRT2) Inhibitors.

A series of N,N'-bisbenzylidenebenzene-1,4-diamine and N,N'-bisbenzylidenenaphthalene-1,4-diamine derivatives were synthesized as inhibitors for human sirtuin type 2 (SIRT2). The design of the new compounds was based on two earlier reported hits from molecular modeling and virtual screening. The most potent compound was N,N'-bis(2-hydroxybenzylidene)benzene-1,4-diamine, which was equipotent with the most potent hit compound and well-known SIRT2 inhibitor sirtinol.

Cerebrospinal fluid distribution of ketoprofen after intravenous administration in young children.

OBJECTIVE: The purpose of this study was to evaluate the cerebrospinal fluid (CSF) distribution of an NSAID, ketoprofen, in children. Ketoprofen concentrations were determined from the CSF, plasma and protein-free plasma samples. METHODS: Children (n = 21), aged 13-94 months, were given intravenous ketoprofen (1 mg/kg) prior to surgery under spinal anaesthesia. Single venous blood and CSF samples from each patient were collected simultaneously 7-67 minutes after the drug administration. Ketoprofen concentrations in the samples were determined using gas chromatography-mass spectrometry. RESULTS: Ketoprofen entered the CSF and was detectable in all samples. However, CSF delivery was limited; the ratio of ketoprofen concentration in CSF to plasma remained below 0.006 at all times. Ketoprofen was highly bound (> 98%) to plasma proteins. The free ketoprofen fraction was not in equilibrium with the CSF, and no clear peak drug concentration in the CSF was observed. CONCLUSION: This study shows that ketoprofen is able to enter the CSF of children, which enables central analgesic effects of ketoprofen. However, the slow distribution of ketoprofen into the CSF and the apparently low absolute concentrations has to be taken into account when central analgesic effects are desired.

Characterization of the sulfhydryl-sensitive site in the enzyme responsible for hydrolysis of 2-arachidonoyl-glycerol in rat cerebellar membranes.

We have previously reported that the endocannabinoid, 2-arachidonoyl-glycerol (2-AG), is hydrolyzed in rat cerebellar membranes by monoglyceride lipase (MGL)-like enzymatic activity. The present study shows that, like MGL, 2-AG-degrading enzymatic activity is sensitive to inhibition by sulfhydryl-specific reagents. Inhibition studies of this enzymatic activity by N-ethylmaleimide analogs revealed that analogs with bulky hydrophobic N-substitution were more potent inhibitors than hydrophilic or less bulky agents. Interestingly, the substrate analog N-arachidonylmaleimide was found to be the most potent inhibitor. A comparison model of MGL was constructed to get a view on the cysteine residues located near the binding site. These findings support our previous conclusion that the 2-AG-degrading enzymatic activity in rat cerebellar membranes corresponds to MGL or MGL-like enzyme and should facilitate further efforts to develop potent and more selective MGL inhibitors.

Sublingual administration of Delta9-tetrahydrocannabinol/beta-cyclodextrin complex increases the bioavailability of Delta9-tetrahydrocannabinol in rabbits.

The bioavailability of Delta(9)-tetrahydrocannabinol (THC) was determined after its sublingual administration as solid THC/beta-cyclodextrin (THC/beta-CD) complex, and was compared to oral administration of ethanolic THC, in rabbits. The absolute bioavailability of THC after sublingual administration of solid THC/beta-CD complex powder (16.0 +/- 7.5%; mean +/- SD; n = 4) is higher than the bioavailability of THC after oral administration of ethanolic THC solution (1.3 +/- 1.4%; mean +/- SD; n = 4). The results suggest that sublingual administration of THC/beta-CD complex is a useful tool in improving absolute bioavailability of THC.

Preparation of budesonide/gamma-cyclodextrin complexes in supercritical fluids with a novel SEDS method.

The aim was to investigate if solid drug/cyclodextrin complexes could be produced in a single-step process with a solution enhanced dispersion by supercritical fluids (SEDS) method. Budesonide and gamma-cyclodextrin (CD) solutions (50% or 99.5% ethanol) were pumped from the same (conventional method) or separate (modified method) containers together with supercritical carbon dioxide through a coaxial nozzle into a particle formation chamber. The pressure was maintained at 100, 150 or 200 bar with a temperature of 40, 60 or 80 degrees C. SEDS-processed powders were characterised with HPLC, DSC and XRPD for budesonide content, complexation and crystallinity. The budesonide dissolution rate was determined in 1% gamma-CD aqueous solution. Solid, white budesonide/gamma-CD complex particles were formed using the conventional and modified SEDS processes. The complexation efficiency was dependent on the processing conditions. For example, with the conventional method (100 bar, 60 degrees C) the yield of the powder was 65+/-12% with 0.14+/-0.02 mg budesonide/mg powder, corresponding to 1:2 drug:CD molar ratio. The dissolution rate of this complexed budesonide (93+/-2% after 15 min) was markedly higher compared to unprocessed micronised budesonide (41+/-10%) and SEDS-processed budesonide without CD (61+/-3%). As a conclusion, SEDS is a novel method to produce solid drug/CD complexes in a single-step process.

Novel water-soluble quaternary piperazine derivatives of chitosan: synthesis and characterization.

Novel synthesis methods for the preparation of quaternary piperazine derivatives of chitosan were developed. Quaternary ammonium moiety can be selectively inserted into either one or both of the piperazine nitrogens, yielding structurally uniform chitosan derivative structures. Water-soluble end products were thoroughly characterized with FT-IR, 1H NMR, 13C NMR and 2D 1H-13C HSQC NMR. The molecular weights of the end products were determined by GPC with triple detection.

Cannabinoids in the treatment of glaucoma.

The leading cause of irreversible blindness is glaucoma, a disease normally characterized by the development of ocular hypertension and consequent damage to the optic nerve at its point of retinal attachment. This results in a narrowing of the visual field, and eventually results in blindness. A number of drugs are available to lower intraocular pressure (IOP), but, occasionally, they are ineffective or have intolerable side-effects for some patients and can lose efficacy with chronic administration. The smoking of marijuana has decreased IOP in glaucoma patients. Cannabinoid drugs, therefore, are thought to have significant potential for pharmaceutical development. However, as the mechanism surrounding their effect on IOP initially was thought to involve the CNS, issues of psychoactivity hindered progress. The discovery of ocular cannabinoid receptors implied an explanation for the induction of hypotension by topical cannabinoid applications, and has stimulated a new phase of ophthalmic cannabinoid research. Featured within these investigations is the possibility that at least some cannabinoids may ameliorate optic neuronal damage through suppression of N-methyl-D-aspartate receptor hyperexcitability, stimulation of neural microcirculation, and the suppression of both apoptosis and damaging free radical reactions, among other mechanisms. Separation of therapeutic actions from side-effects now seems possible through a diverse array of novel chemical, pharmacological, and formulation strategies.