Oral transmucosal delivery of eletriptan for neurological diseases.

Migraine is a highly prevalent neurological disease affecting circa 1 billion patients worldwide with severe incapacitating symptoms, which significantly diminishes the quality of life. As self-medication practice, oral administration of triptans is the most common option, despite its relatively slow therapeutic onset and low drug bioavailability. To overcome these issues, here we present, to the best of our knowledge, the first study on the possibility of oral transmucosal delivery of one of the safest triptans, namely eletriptan hydrobromide (EB). Based on a comprehensive set of in vitro and ex vivo experiments, we highlight the conditions required for oral transmucosal delivery, potentially giving rise to similar, or even higher, drug plasma concentrations expected from conventional oral administration. With histology and tissue integrity studies, we conclude that EB neither induces morphological changes nor impairs the integrity of the mucosal barrier following 4 h of exposure. On a cellular level, EB is internalized in human oral keratinocytes within the first 5 min without inducing toxicity at the relevant concentrations for transmucosal delivery. Considering that the pKa of EB falls within the physiologically range, we systematically investigated the effect of pH on both solubility and transmucosal permeation. When the pH is increased from 6.8 to 10.4, the drug solubility decreases drastically from 14.7 to 0.07 mg/mL. At pH 6.8, EB gave rise to the highest drug flux and total permeated amount across mucosa, while at pH 10.4 EB shows greater permeability coefficient and thus higher ratio of permeated drug versus applied drug. Permeation experiments with model membranes confirmed the pH dependent permeation profile of EB. The distribution of EB in different cellular compartments of keratinocytes is pH dependent. In brief, high drug ionization leads to higher association with the cell membrane, suggesting ionic interactions between EB and the phospholipid head groups. Moreover, we show that the chemical permeation enhancer DMSO can be used to enhance the drug permeation significantly (i.e., 12 to 36-fold increase). Taken together, this study presents important findings on transmucosal delivery of eletriptan via the oral cavity and paves the way for clinical investigations for a fast and safe migraine treatment.

A novel versatile flow-donor chamber as biorelevant ex-vivo test assessing oral mucoadhesive formulations.

Oral transmucosal drug delivery is a non-invasive administration route for rapid therapeutic onset and greater bioavailability avoiding the first-pass metabolism. Mucoadhesive formulations are advantageous as they may retain the drug at the administration site. Proper equipment to assess mucoadhesive properties and corresponding drug absorption is fundamental for the development of novel drug delivery systems. Here we developed a new flow-through donor chamber for well-established diffusion cells, and we tested the effects on drug and formulation retention in situ of adding mucoadhesive polymers or mesoporous silica particles to a reference formulation. Mesoporous silica particles are of particular interest as they may be used to encapsulate and retain drug molecules. Compared to other ex-vivo methods described in literature for assessing mucoadhesive performance and transmucosal drug delivery, this new donor chamber provides several advantages: i) it reflects physiological conditions better as a realistic saliva flow can be provided over the administration site, ii) it is versatile since it can be mounted on any kind of vertical diffusion cell allowing simultaneous detection of drug retention at the administration site and drug permeation through the tissue, and iii) it enables optical quantification of formulations residence time aided by image processing. This new flow-through donor diffusion cell set-up proved sensitive to differentiate a reference formulation from one where 20 %(w/w) Carbomer was added (to further improve the mucoadhesive properties), with respect to both drug and formulation residence times. We also found that mesoporous silica particles, investigated as particles only and mixed together with the reference formulation, gave very similar drug and formulation retention to what we observed with the mucoadhesive Carbomer. However, after some time (>30 min) it became obvious that the tablet excipients in the reference formulation promote particle retention on the mucosa. This work provides a new simple and versatile biorelevant test for the evaluation of oral mucoadhesive formulations and paves the way for further studies on mesoporous silica particles as valuable excipients for enhancing oral mucoadhesion.

Discovery of the Oral Leukotriene C4 Synthase Inhibitor (1S,2S)-2-({5-[(5-Chloro-2,4-difluorophenyl)(2-fluoro-2-methylpropyl)amino]-3-methoxypyrazin-2-yl}carbonyl)cyclopropanecarboxylic Acid (AZD9898) as a New Treatment for Asthma.

While bronchodilators and inhaled corticosteroids are the mainstay of asthma treatment, up to 50% of asthmatics remain uncontrolled. Many studies show that the cysteinyl leukotriene cascade remains highly activated in some asthmatics, even those on high-dose inhaled or oral corticosteroids. Hence, inhibition of the leukotriene C4 synthase (LTC4S) enzyme could provide a new and differentiated core treatment for patients with a highly activated cysteinyl leukotriene cascade. Starting from a screening hit (3), a program to discover oral inhibitors of LTC4S led to (1S,2S)-2-({5-[(5-chloro-2,4-difluorophenyl)(2-fluoro-2-methylpropyl)amino]-3-methoxypyrazin-2-yl}carbonyl)cyclopropanecarboxylic acid (AZD9898) (36), a picomolar LTC4S inhibitor (IC50 = 0.28 nM) with high lipophilic ligand efficiency (LLE = 8.5), which displays nanomolar potency in cells (peripheral blood mononuclear cell, IC50,free = 6.2 nM) and good in vivo pharmacodynamics in a calcium ionophore-stimulated rat model after oral dosing (in vivo, IC50,free = 34 nM). Compound 36 mitigates the GABA binding, hepatic toxicity signal, and in vivo toxicology findings of an early lead compound 7 with a human dose predicted to be 30 mg once daily.

Hepatitis C virus NS3 protease inhibitors comprising a novel aromatic P1 moiety.

Inhibition of the hepatitis C virus (HCV) NS3 protease has emerged as an attractive approach to defeat the global hepatitis C epidemic. In this work, we present the synthesis and biochemical evaluation of HCV NS3 protease inhibitors comprising a non-natural aromatic P(1) moiety. A series of inhibitors with aminobenzoyl sulfonamides displaying submicromolar potencies in the full-length NS3 protease assay was prepared through a microwave-irradiated, palladium-catalyzed, amidocarbonylation protocol.

Structure-activity relationships of HCV NS3 protease inhibitors evaluated on the drug-resistant variants A156T and D168V.

BACKGROUND: HCV infections are a serious threat to public health. An important drug target is the NS3 protease, for which several inhibitors are in clinical trials. Because of the high mutation rate of the virus, resistance against any HCV-specific drug is likely to become a substantial problem. Structure-activity data for the major resistant variants are therefore needed to guide future designs of protease inhibitors. METHODS: The inhibitory potency of tripeptide NS3 protease inhibitors, with either a P2 proline or phenylglycine, in combination with different P3 and P1-P1' groups, was assessed in enzyme activity assays using the full-length NS3 protein with known resistance-conferring substitutions A156T or D168V. The results obtained from these variants were compared with the inhibition of the wild-type enzyme. Molecular modelling was used to rationalize the biochemical results. RESULTS: Inhibitors combining the P2 proline and P1 (1R,2S)-1-amino-2-vinylcyclopropyl-carboxylic acid (vinylACCA) lost much of their potency on the resistant variants. Exchange of the P2 proline for phenylglycine yielded inhibitors that were equipotent on the wild-type and on the A156T and D168V variants. The same result was obtained from the combination of either the P2 residue with a norvaline or an aromatic scaffold in the P1 position. CONCLUSIONS: The combination of a substituted P2 proline and P1 vinylACCA appears to be the main problem behind the observed resistance. Molecular modelling suggests an enforced change in binding conformation for the P2 proline-based inhibitors, whereas the phenylglycine-based inhibitors retained their wild-type binding conformation in the substituted forms of the enzyme.

Hepatitis C virus NS3 protease inhibitors: large, flexible molecules of peptide origin show satisfactory permeability across Caco-2 cells.

The purpose of this study was to investigate the intestinal absorption of tripeptide-based compounds intended for treatment of hepatitis C virus (HCV) infection. The intestinal permeability of 11 HCV NS3 protease inhibitors (Mw 687-841, ClogD(pH 7.4) 1.2-7.3 and 10-13 hydrogen bond donors/acceptors) was measured using Caco-2 cells. Each compound was investigated in the apical to basolateral (a-b) and basolateral to apical (b-a) direction at pH 7.4. For compounds displaying efflux the experiment was repeated in the presence of 1 microM GF120918 to investigate possible involvement of P-glycoprotein (Pgp; ABCB1). All compounds displayed intermediate to high permeability. Seven of them showed extensive efflux, with 31-114-fold higher permeability in the b-a direction than the a-b direction. Addition of the Pgp inhibitor GF120918 reduced the b-a transport rate for the effluxed compounds. However, for inhibitors with a C-terminal carboxylic acid and the acidic bioisosteres thereof the efflux was still significant. Hence, the negative charge resulted in efflux by other ABC-transporters than Pgp. From this study it can be concluded that small changes in the overall structure can lead to a large variation in permeability and efflux as shown by the inhibitors herein, properties that also may influence the resulting inhibition potency of the compounds when performing cell-based pharmacological assays.

New developments in the discovery of agents to treat hepatitis C.

Hepatitis C virus (HCV) has deceived researchers for seventeen years now and although the current therapy regimen has been optimized by the development of pegylated interferon-alpha and the addition of ribavirin, no new agent to treat HCV infected patients has yet reached the market. A new era is approaching the HCV research due to new developments for the propagation of the virus in a cell-based system, which may lead to new drug innovations. Efforts in the search of new treatments for HCV infected patients are either focused on direct antiviral drugs, targeting the structural components or enzymes encoded by the virus, or indirect antiviral drugs, targeting host cell components (immunomodulators etc.). An inspection of the drug pipeline for HCV reveals representatives from both classes and of different mechanisms of action. Among the direct acting antiviral agents, inhibitors of the NS3 protease, the NS5B polymerase, and the viral RNA are the most intensively explored. However, there is also on-going and promising preclinical research, in different stages, on other potential targets as the structural protein E2 (for cell-entry inhibitors), the NS3 helicase, the p7 ion-channel, and the multifunctional NS5A protein. The combat of HCV will certainly require a combination of drugs of different mechanisms in order to reduce the emergence of resistance. The latest developments in the discovery of agents to treat HCV are reviewed, with special focus on direct small-molecule antiviral drugs, from a medicinal chemistry perspective.

Evaluation of a diverse set of potential P1 carboxylic acid bioisosteres in hepatitis C virus NS3 protease inhibitors.

There is an urgent need for more efficient therapies for people infected with hepatitis C virus (HCV). HCV NS3 protease inhibitors have shown proof-of-concept in clinical trials, which make the virally encoded NS3 protease an attractive drug target. Product-based NS3 protease inhibitors comprising a P1 C-terminal carboxylic acid have shown to be effective and we were interested in finding alternatives to this crucial carboxylic acid group. Thus, a series of diverse P1 functional groups with different acidity and with possibilities to form a similar, or an even more powerful, hydrogen bond network as compared to the carboxylic acid were synthesized and incorporated into potential inhibitors of the NS3 protease. Biochemical evaluation of the inhibitors was performed in both enzyme and cell-based assays. Several non-acidic C-terminal groups, such as amides and hydrazides, were evaluated but failed to produce inhibitors more potent than the corresponding carboxylic acid inhibitor. The tetrazole moiety, although of similar acidity to a carboxylic acid, provided an inhibitor with mediocre potencies in both assays. However, the acyl cyanamide and the acyl sulfinamide groups rendered compounds with low nanomolar inhibitory potencies and were more potent than the corresponding carboxylic acid inhibitor in the enzymatic assay. Additionally, results from a pH-study suggest that the P(1) C-terminal of the inhibitors comprising a carboxylic acid, an acyl sulfonamide or an acyl cyanamide group binds in a similar mode in the active site of the NS3 protease.

Exploration of acyl sulfonamides as carboxylic acid replacements in protease inhibitors of the hepatitis C virus full-length NS3.

The hepatitis C virus (HCV) NS3 protease has emerged as a promising anti-HCV drug target. Herein, we present an investigation of NS3 inhibitors comprising the acyl sulfonamide functionality. A series of tetra- and tripeptide based acyl sulfonamide inhibitors and their structure-activity relationships from both enzymatic and cell-based in vitro assays are presented. In summary, the acidity of the acyl sulfonamide functionality, the character of the P1 side chain, and the acyl sulfonamide substituent were found to be important for the inhibitory potencies.

Easy-to-execute carbonylations: microwave synthesis of acyl sulfonamides using Mo(CO)(6) as a solid carbon monoxide source.

The development of a robust palladium-catalyzed amidocarbonylation protocol for the preparation of aromatic acyl sulfonamides utilizing high-density microwave heating is described. This synthetic approach employs Mo(CO)(6) as a convenient CO-releasing reagent and allows for the direct preparation of acyl sulfonamides from both aryl iodides and aryl bromides. The reactions can be performed under air, employing only 15 min of microwave irradiation, to produce acyl sulfonamide derivatives in good to excellent yields. To illustrate the usefulness of this method, we reported the synthesis of a novel hepatitis C virus NS3 protease inhibitor.