Identification of an Orally Bioavailable, Brain-Penetrant Compound with Selectivity for the Cannabinoid Type 2 Receptor.

Modulation of the endocannabinoid system (ECS) is of great interest for its therapeutic relevance in several pathophysiological processes. The CB2 subtype is largely localized to immune effectors, including microglia within the central nervous system, where it promotes anti-inflammation. Recently, a rational drug design toward precise modulation of the CB2 active site revealed the novelty of Pyrrolo[2,1-c][1,4]benzodiazepines tricyclic chemotype with a high conformational similarity in comparison to the existing leads. These compounds are structurally unique, confirming their chemotype novelty. In our continuing search for new chemotypes as selective CB2 regulatory molecules, following SAR approaches, a total of 17 selected (S,E)-11-[2-(arylmethylene)hydrazono]-PBD analogs were synthesized and tested for their ability to bind to the CB1 and CB2 receptor orthosteric sites. A competitive [3H]CP-55,940 binding screen revealed five compounds that exhibited >60% displacement at 10 µM concentration. Further concentration-response analysis revealed two compounds, 4k and 4q, as potent and selective CB2 ligands with sub-micromolar activities (Ki = 146 nM and 137 nM, respectively). In order to support the potential efficacy and safety of the analogs, the oral and intravenous pharmacokinetic properties of compound 4k were sought. Compound 4k was orally bioavailable, reaching maximum brain concentrations of 602 ± 162 ng/g (p.o.) with an elimination half-life of 22.9 ± 3.73 h. Whether administered via the oral or intravenous route, the elimination half-lives ranged between 9.3 and 16.7 h in the liver and kidneys. These compounds represent novel chemotypes, which can be further optimized for improved affinity and selectivity toward the CB2 receptor.

First In Class (S,E)-11-[2-(Arylmethylene)Hydrazono]-PBD Analogs As Selective CB2 Modulators Targeting Neurodegenerative Disorders.

Newly designed pyrrolo[2,1-c][1,4]benzodiazepines tricyclic skeleton has shown potential clusters of cannabinoid receptors CB1/CB2 selective ligands. CB2 plays a critical role in microglial-derived neuroinflammation, where it modulates cell proliferation, migration, and differentiation into M1 or M2 phenotypes. Beginning with computer-based docking studies accounting the recently discovered X-ray crystal structure of CB2, we designed a series of PBD analogs as potential ligands of CB2 and tested their binding affinities. Interestingly, computational studies and theoretical binding affinities of several selected (S,E)-11-[2-(arylmethylene)hydrazono]-PBD analogs, have revealed the presence of potential selectivity in binding attraction towards CB1 and CB2. Reported here is the discovery of the first representatives of this series of selective binding to CB2. Preliminary data showed that this class of molecules display potential binding efficacy towards the cannabinoid receptors tested. Intriguingly, initial cannabinoid binding assay showed a selective binding affinity of 4g and 4h showed K i of 0.49 and 4.7 µM towards CB2 receptors while no binding was observed to CB1. The designed leads have shown remarkable stability pattern at the physiological pH magnifying their therapeutic values. We hypothesize that the PBD tricyclic structure offers the molecule an appropriate three-dimensional conformation to fit snugly within the active site of CB2 receptors, giving them superiority over the reported CB2 agonists/inverse agonists. Our findings suggested that the attachment of heterocyclic ring through the condensation of diazepine hydrazone and S- or N-heterocyclic aldehydes enhances the selectivity of CB2 over CB1.

An inhibitory compound produced by a soil isolate of Rhodococcus has strong activity against the veterinary pathogen R. equi.

Complete genome sequencing of dozens of strains of the soil bacterium Rhodococcus has revealed the presence of many cryptic biosynthetic gene clusters, presumably dedicated to the production of small molecules. This has sparked a renewed interest in this underexplored member of the Actinobacteria as a potential source of new bioactive compounds. Reported here is the discovery of a potent inhibitory molecule produced by a newly isolated strain of Rhodococcus, strain MTM3W5.2. This small inhibitory molecule shows strong activity against all Rhodococcus species tested, including the veterinary pathogen R. equi, and some closely related genera. It is not active against other Gram positive or Gram negative bacteria. A screen of random transposon mutants identified a gene required to produce this inhibitory compound. This gene is a large multi-domain, type I polyketide synthase that is part of a very large multi-gene biosynthetic gene cluster in the chromosome of strain MTM3W5.2. The high resolution mass spectrum of a major chromatogram peak from a broth culture extract of MTM3W5.2 shows the presence of a compound at m/z 911.5490 atomic mass units. This compound is not detected in the culture extracts from a non-producing mutant strain of MTM3W5.2. A large gene cluster containing at least 14 different type I polyketide synthase genes is proposed to be required to synthesize this antibiotic-like compound.

Synthesis and biological activity of fused tetracyclic Pyrrolo[2,1-c][1,4]benzodiazepines.

Cancer remains the second major cause of death in the world. Thus, there is a pressing need to identify potential synthetic route for the development of novel anticancer agents which will serve as lead compounds to effectively combat this life-threatening epidemic. Pyrrolo[2,1-c][1,4]benzodiazepines (PBDs) have sparked a great interest as lead compounds because of their cancerostatic and anti-infective properties. The twisted molecular structure of PBD analogs provides both helical and chiral elements. In an effort to expand novel PBDs that interact with the key exocyclic amino group of the DNA-guanine base, we hypothesized that construction of a fused cyclic active system, would likely serve as an electrophilic site when compared to traditional electrophilic C11-N10 imine group. To examine our theory, we report herein the synthesis and cell viability/cytotoxicity of a series of PBD analogs using NCI-60 cell lines screening. Thus, compounds 1-13 were synthesized and fully characterized. The selected PBDs were found to have marginal inhibition of growth, up to 30%, for certain cell lines.

Marine Inspired 2-(5-Halo-1H-indol-3-yl)-N,N-dimethylethanamines as Modulators of Serotonin Receptors: An Example Illustrating the Power of Bromine as Part of the Uniquely Marine Chemical Space.

In previous studies, we have isolated several marine indole alkaloids and evaluated them in the forced swim test (FST) and locomotor activity test, revealing their potential as antidepressant and sedative drug leads. Amongst the reported metabolites to display such activities was 5-bromo-N,N-dimethyltryptamine. Owing to the importance of the judicious introduction of halogens into drug candidates, we synthesized two series built on a 2-(1H-indol-3-yl)-N,N-dimethylethanamine scaffold with different halogen substitutions. The synthesized compounds were evaluated for their in vitro and in vivo antidepressant and sedative activities using the mouse forced swim and locomotor activity tests. Receptor binding studies of these compounds to serotonin (5-HT) receptors were conducted. Amongst the prepared compounds, 2-(1H-indol-3-yl)-N,N-dimethyl-2-oxoacetamide (1a), 2-(5-bromo-1H-indol-3-yl)-N,N-dimethyl-2-oxoacetamide (1d), 2-(1H-indol-3-yl)-N,N-dimethylethanamine (2a), 2-(5-chloro-1H-indol-3-yl)-N,N-dimethylethanamine (2c), 2-(5-bromo-1H-indol-3-yl)-N,N-dimethylethanamine (2d), and 2-(5-iodo-1H-indol-3-yl)-N,N-dimethylethanamine (2e) have been shown to possess significant antidepressant-like action, while compounds 2c, 2d, and 2e exhibited potent sedative activity. Compounds 2a, 2c, 2d, and 2e showed nanomolar affinities to serotonin receptors 5-HT1A and 5-HT7. The in vitro data indicates that the antidepressant action exerted by these compounds in vivo is mediated, at least in part, via interaction with serotonin receptors. The data presented here shows the valuable role that bromine plays in providing novel chemical space and electrostatic interactions. Bromine is ubiquitous in the marine environment and a common element of marine natural products.

Specificity and mechanism of mandelamide hydrolase catalysis.

The best-studied amidase signature (AS) enzyme is probably fatty acid amide hydrolase (FAAH). Closely related to FAAH is mandelamide hydrolase (MAH), whose substrate specificity and mechanism of catalysis are described in this paper. First, we developed a convenient chromogenic substrate, 4-nitrophenylacetamide, for MAH. The lack of reactivity of MAH with the corresponding ethyl ester confirmed the very limited size of the MAH leaving group site. The reactivity of MAH with 4-nitrophenyl acetate and methyl 4-nitrophenyl carbonate, therefore, suggested formation of an "inverse" acyl-enzyme where the small acyl-group occupies the normal leaving group site. We have interpreted the specificity of MAH for phenylacetamide substrates and small leaving groups in terms of its active site structure, using a homology model based on a FAAH crystal structure. The relevant structural elements were compared with those of FAAH. Phenylmethylboronic acid is a potent inhibitor of MAH (Ki = 27 nM), presumably because it forms a transition state analogue structure with the enzyme. O-Acyl hydroxamates were not irreversible inactivators of MAH but some were found to be transient inhibitors.

ß-Peptide coatings by surface-initiated polymerization.

Homopolymers of ß-lactams can be grown by surface-initiated polymerization. These surface-linked ß-peptides are living polymers with the potential to be utilized as tunable, protease-resistant interfaces in multiphase structural composites where the characteristics of the interface influence bulk properties.

4-quinolones as noncovalent inhibitors of high molecular mass penicillin-binding proteins.

Penicillin-binding proteins (PBPs) are important bacterial enzymes that carry out the final steps of bacterial cell wall assembly. Their DD-transpeptidase activity accomplishes the essential peptide cross-linking step of the cell wall. To date, all attempts to discover effective inhibitors of PBPs, apart from ß-lactams, have not led to new antibiotics. Therefore, the need for new classes of efficient inhibitors of these enzymes remains. Guided by a computational fragment-based docking procedure, carried out on Escherichia coli PBP5, we have designed and synthesized a series of 4-quinolones as potential inhibitors of PBPs. We describe their binding to the PBPs of E. coli and Bacillus subtilis. Notably, these compounds bind quite tightly to the essential high molecular mass PBPs.

2-N-Methyl modifications and SAR studies of manzamine A.

Quaternary carbolinium salts have been reported to show improved antimalarial activity and reduced cytotoxicity as compared to electronically neutral beta-carbolines. In this study, mono- and di-methylated quaternary carbolinium cations of manzamine A were synthesized and evaluated for their in vitro antimalarial and antimicrobial activity, cytotoxicity, and also their potential for glycogen synthase kinase (GSK-3beta) inhibition using molecular docking studies. Among the analogs, 2-N-methylmanzamine A (2) exhibited antimalarial activity (IC(50) 0.7-1.0microM) but was less potent than manzamine A. However the compound was significantly less cytotoxic to mammalian kidney fibroblasts and the selectivity index was in the same range as manzamine A.