Volume 76, Issue 5

The paper begins with a discussion of the needs and goals of metabolic predictions in early drug research. Major difficulties toward this objective are examined, mainly the various substrate and product selectivities characteristic of drug metabolism. In a second part, we classify and summarize the major in silico methods used to predict drug metabolism. A discrimination is thus made between “local ”and “global ”systems. In the last part of the paper, the program METEOR is presented and evaluated using the published metabolic data of 10 substrates.

Transmissible spongiform encephalopathies (TSEs), currently known as prion diseases, are neurodegenerative disorders of the central nervous system (CNS) caused by an elusive infectious agent called “prion” (proteinaceous infectious particle). These dis orders include: kuru, Creutzfeldt –Jakob disease (CJD) and its variant (vCJD), Gerstmann–Sträussler–Scheinker (GSS) disease and fatal familial insomnia (FFI) in humans, scrapie in sheep and goats, bovine spongiform encephalopathy (BSE) or mad cow disease, and chronic wasting disease (CWD) in cervids. According to the widely accepted “prion hypothesis”, prion is an aggregate of the abnormal isoform of prion protein (PrP Sc ). Prion protein is a cell-derived glycoprotein (this normal isoform is called PrP c ) encoded by a gene on chromosome 20 in humans (PRNP). In familial forms of TSEs, mutations within the ORF of PRNP are linked to the phenotypic expression of the disease. TSEs are important from public health perspective, and “mad cow disease has created the greatest threat to the safety of human food supply in modern times. vCJD threatens the safety of the blood supply worldwide”. Thus, to search for effective therapy is more than an urgent task. In TSEs, aggregates of PrP Sc accumulate in the brain in a form of plaques, or synaptic deposits. The conversion of PrP c into PrP Sc and subsequent deposits of PrP Sc are targets for therapeutic interventions. These include: tricyclic compounds—acridine and phenothiazine derivatives; quinacrine; anti-PrP Sc antibodies; dendrimers; polyethylene antibiotics (amphotericin B, MS-8209); pentosan polysulfate; and dextran sulfate. All these compounds are active in many in vitro and in vivo assays, but not proved definitely active in humans. Thus, albeit interesting and promising, the chemotherapy of TSEs is still in the infant phase.

( S )-Glutamic acid (Glu), the major excitatory neurotransmitter in the central nervous system, operates through ionotropic as well as metabotropic receptors and is considered to be involved in a number of degenerative brain diseases that are currently without any satisfactory therapeutic treatment. Until recently, development of selective Glu receptor agonists had mainly been based on structural optimization of naturally occurring lead compounds structurally related to Glu. Crystallization of the agonist binding domain of the GluR2 subunit of the 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptor subtype of ionotropic Glu receptors (iGluRs) in the presence or absence of an agonist has provided important information about ligand-receptor interaction mechanisms. The availability of such binding domain crystal structures has formed the basis for rational design of ligands, especially for the AMPA subtypes of iGluRs.

The development of new 2-amino-3-(3-hydroxy-5-methyl-4-isoxazolyl)propionic acid (AMPA) receptor (AMPAR) negative modulators has received considerable interest due to their crucial role in specific neurological diseases. In recent years, our research group has been engaged in the development of new AMPAR ligands and chemical and biological studies of various 2,3-benzodiazepin-4-(thi)ones (CFMs) and their analogous cyclofunctionalized have been reported. Electrophysiological experiments confirmed that their effects are mediated through the AMPAR complex in a selective and noncompetitive fashion. Moreover, we carried out computational studies which suggested the possible binding site for noncompetitive antagonists; we also developed a 3D ligand-based pharmacophore model in order to map common structural features of highly potent compounds. Our hypothesis was successfully used as a frame work for the design of a new class of allosteric modulators containing a tetrahydroisoquinoline skeleton and led to the discovery of a very potent AMPAR antagonist with marked antiepileptic effects.

The discovery of numerous endogenous neuropeptides that participate in the formation, transmission, modulation, and perception of pain signals offers numerous strategies for the development of new analgesics. Nevertheless, the same research has not yet replaced opioids as the gold standard of pain treatment. Therefore, one possible avenue of drug development may shift interest from searching for receptor-selective opioids to creating an arsenal of drugs that target multiple opioid and non-opioid sites simultaneously. The presented short review focuses on the development of potential analgesic peptidomimetic compounds based upon opioid neuropeptides and substance P.

Endomorphins (endomorphin-1,H-Tyr-Pro-Trp-Phe-NH 2 ,endomorphin-2, Tyr-Pro-Phe-Phe-NH 2 ) are potent and selective µ-opioid receptor agonists. In order to improve the affinity and chemical stability of endomorphins, we have designed, synthesized, and characterized novel analogs with unnatural (2 ',6 '-dimethyltyrosine, Dmt) and/or ß-alicyclic amino acids (ACPC and ACHC). Radioligand binding assay indicated that several of the novel analogs exhibit high affinity for both µ-and d-opioid receptors in rat-or mouse-brain membrane preparations. The most promising derivatives—such as Dmt-Pro-Trp/Phe-Phe-NH 2 , Dmt-(1 S ,2 R )-ACPC-Phe-Phe-NH 2 , and Dmt-(1 S ,2 R )-ACHC-Phe-Phe-NH 2 )—were characterized in recombinant cell lines expressing human µ-or d-opioid receptors. Interestingly, while these novel peptides were potent opioid agonists in the functional [ 35 S]GTPgammaS binding assays in Chinese hamster ovary cells expressing the µ-opioid receptors, some behaved as antagonist or inverse agonist in the human d-opioid receptor-expressing CHO cells. Since it has previously been demonstrated that the coadministration of d-antagonists with µ-analgesics attenuates the development of analgesic tolerance, introduction of high-affinity d-antagonist properties into the µ-agonist endomorphins is expected to lead to potent analgesics that produce limited tolerance.

Based on our contemporary studies on the structures of biologically active molecules, we focus our attention on the aliphatic chain and its conformation. That flexible spacer definitely influenced the balanced position of all pharmacophoric points in molecules of biological ligands. The one atomic linker and two or three atomic spacers with one heteroatom X =O, S, CH 2 , NH have been taken into account. The conformational preferences clearly depend on the heteroatom X. In the discussion, we utilize our own X-ray data, computation chemistry methods, population analysis, and statistical data from the Cambridge Structural Database (CSD).

We have synthesized a series of novel hydrazines and hydrazino alcohols that specifically inhibit vascular adhesion protein-1 (VAP-1), a human endothelial cell adhesion molecule with a well documented role in inflammation. VAP-1 is a semicarbazide-sensitive amine oxidase (SSAO), and the enzyme activity has been demonstrated to have a role in VAP-1 function. An indane hydrazino alcohol was able to reduce clinical symptoms of inflammation in experimental arthritis in rodents and has the potential to be a novel anti-inflammatory drug.

The article focuses attention on furoxan derivatives (1,2,5 oxadiazole 2-oxides) as NO donors. Possible mechanisms for NO release from these products in physiological solution and in segments of rabbit femoral artery are briefly considered. The in vitro anti aggregatory activities and the in vitro and in vivo vasodilating properties of a number of furoxans are examined with particular reference to involvement of NO in these actions. The use of the furoxan system to design new NO donor/drug hybrids is discussed in connection with the problem of the balance between NO- and drug dependent activities of the resulting structures. Whether other biological activities (as yet, little studied) of furoxans, such as their antiparasite, antimicrobial, and antitumoral effects, are NO dependent, is a matter still to be explored.

Antibodies are one of the most promising components of the biotechnology repertoire for the purpose of drug delivery. On the one hand, they are proven agents for cell-selective delivery of highly toxic agents in a small but expanding number of cases. This technology calls for the covalent attachment of the cytotoxin to a tumor-specific antibody by a linkage that is reversible under appropriate conditions (antibody conjugate therapy, ACT —“passive delivery”). On the other hand, the linker cleavage can be accomplished by a protein catalyst attached to the tumor-specific antibody (“catalytic delivery”). Where the catalyst is an enzyme, this approach is known as antibody-directed enzyme prodrug therapy (ADEPT). Where the transformation is brought about by a catalytic antibody, it has been termed antibody-directed abzyme prodrug therapy (ADAPT). These approaches will be illustrated with emphasis on how their demand for new biotechnology is being realized by structure-based protein engineering.

In this article, an overview of the most common ligand-based in silico screening techniques is given together with an example on the recent successful application of combined use of pharmacophore modeling, database mining, and biological assays. Additionally, a new approach for structure-based high-throughput pharmacophore model generation is presented. The LigandScout program contains an automated method for creating pharmacophore models from experimentally determined structure data, e.g., publicly available from the Brookhaven Protein Databank (PDB). In a first step, known algorithms were implemented and improved to extract small-molecule ligands from the PDB including assignment of hybridization states and bond orders. Second, from the interactions of the interpreted ligands with relevant surrounding amino acids, pharmacophore models reflecting functional interactions like H-bonds or ionic transfer interactions were created. These models can be used for screening molecular databases for similar modes of actions on the one hand, or for screening one single compound for potential side-effects (reversed screening) on the other hand. The implementation was done using the ilib framework, which also formed the basis of the software tool Comb i Gen, a fragment-based virtual combinatorial library generation program enabling the user to obtain in silico compound collections with high drug-likeness.

Inhibition of drug efflux pumps such as P-glycoprotein represents a versatile approach for overcoming multidrug resistance in tumor therapy. Although numerous compounds have been identified as being able to inhibit P-glycoprotein, only little is known on the molecular basis of the drug–protein interaction. This article gives an overview of the different pharmacoinformatic approaches we used to develop new propafenone-type modulators of P-glycoprotein. These include 2D-and 3D-QSAR studies, artificial neural networks, and photoaffinity labeling studies.

Flaviviridae are an important family of viruses, responsible for widely spread diseases such as dengue and West Nile fever and hepatitis C. Despite the severity of the related diseases, no effective antiviral treatments for infection are available. Following our discovery of adenosine-hindered analogs as potent antiflaviviridae agents, we have continued our investigation on guanosine and inosine derivatives, which were evaluated for activity against BVDV, YFV, DENV, and WNV viruses in cell-based assays. The present study allowed us to identify some newer features that led to improve the antiviral potency (down to the µM range) and to selectively inhibit BVDV and YFV viruses. The molecular modeling results were consistent with the hypothesis that test analogs act as RNA-dependent RNA polymerase (RdRp) inhibitors by interacting with a surface allosteric binding pocket.

With the emergence of high-throughput screening in the pharmaceutical industry over a decade ago, synthetic chemists were faced with the challenge of preparing large collections of molecules to satisfy the demand for new screening compounds. The unique exploratory power of multicomponent reactions such as the Biginelli three-component reaction was soon recognized to be extremely valuable to produce compound libraries in a time- and cost-effective manner. The present review summarizes synthetic advances from our laboratories for the construction of Biginelli libraries via solution-and solid-phase strategies that are amenable to a high-throughput or combinatorial format.

The total synthesis of (−)-cabenegrin A-I was achieved via (−)-6a R ,11a R maackiain, which was obtained by optical resolution of racemic maackiain using S -(−)-alpha-methylbenzyl isocyanate. The synthesis of rac -maackiain was performed both with the Heck oxyarylation of 7-benzyloxy-2 H -chromene and the BF 3 OEt 2 mediated ring closure of isoflavan-4-ol derivatives, the latter of which provided much higher yields. The first enantioselective synthesis of trans -6a S ,11a R -pterocarpan and its conversion to cis -6a S ,11a S -ptarocarpan was also presented starting from racemic 2'-benzyloxyflavanone. Their stereochemistry was deduced by circular dichroism (CD) as well as by X-ray analysis of the ketal intermediate.

This glossary contains definitions of 365 terms frequently used in the multidisciplinary field of toxicokinetics. The glossary is compiled primarily for chemists who find themselves currently working in toxicology and requiring a knowledge of the expressions used in toxicokinetics,especially in relation to hazard and risk assessment. Some medical terms are included, where relevant, because of their frequent occurrence in the toxicological literature and because chemists would not normally be expected to be familiar with them. There are three annexes,one containing a list of abbreviations and acronyms used in toxicokinetics, one containing a list of abbreviations and acronyms of names of international bodies and legislation that are relevant to toxicology and chemical safety, and one giving sources for further reading.