Combinatorial Chemistry & High Throughput Screening - Volume 4, Issue 3, 2001

The homology of peptide sequences selected from a 7mer phage display library with antibodies elicited by the multicelled parasite Taenia solium in cerebrospinal fluid and serum of neurocysticercosis (NCC) patients and by antibodies of uninfected control patients with similar neurological complications of other ethiology (non-NCC) were analyzed using a PILEUP-Tudos sequence alignments program. The analysis generated dendrograms bearing two types of sequence clusters, those containing (1) only NCC patients-derived peptides and (2) both NCC- and control non-NCC - patient derivatives. By using ELISA, peptides that were selected by the antibodies were identified predominantly in the NCC-derived clusters. In repeated analysis in which sequences were added or removed, the first type of clusters maintained their structure, while the second type of clusters were split into many separate homology units dispersed throughout the guide tree. These results are interpreted as the ability of the analysis to segregate NCC-specific peptide sequences from other sequences. Altogether, this study demonstrates the high potential of the PILEUP-Tudos computer program to analyze phagotope collections recovered through biopanning with polyclonal antibodies elicited in patients by complex and as yet unknown multiple pathogenic antigens and to separate all phagotopes that are disease-relevant on the basis of the sequence homology.

A library of 24 glycoconjugates related to glycosylated b-amino acid derivative (I) was been prepared and screened against DNA topoisomerase-II of the filarial parasite S. cervi. Among these, compound 6 was found to be a potent inhibitor of DNA topoisomerase-II with 95percent inhibition at 1.0?mM. Furthermore, compound 6 was at least three times more potent than the lead compound, glycosylated b-amino acid derivative I.

Drug metabolism can have profound effects on the pharmacological and toxicological profile of therapeutic agents. In the pharmaceutical industry, many in vitro techniques are in place or under development to screen and optimize compounds for favorable metabolic properties in the drug discovery phase. These in vitro technologies are meant to address important issues such as (1) is the compound a potent inhibitor of drug metabolising enzymes (DMEs) (2) does the compound induce the expression of DMEs (3) how labile is the compound to metabolic degradation (4) which specific enzyme(s) is responsible for the compound biotransformation and (5) to which metabolites is the compound metabolized Answers to these questions provide a basis for judging whether a compound is likely to have acceptable pharmacokinetic properties in vivo. To address these issues on the increasing number of compounds inundating the drug discovery programs, high throughput assays are essential. A combination of biochemical advances in the understanding of the function and regulation of DMEs (in particular, cytochromes P450, CYPs) and automated analytical technologies are revolutionizing drug metabolism research. Automated LC-MS based metabolic stability, fluorescence, radiometric and LC-MS based CYP inhibition assays are now in routine use. Automatible models for studying CYP induction based on enzyme activity, quantitative RT-PCR and reporter gene systems are being developed. We will review the utility and limitations of these HTS approaches and highlight on-going developments and emerging technologies to answer metabolism questions at the different stages of the drug discovery process.

The ultimate public health aim of genetic screening is prevention. This can be achieved by reducing birth prevalence through primary or secondary methods such as pre-conceptional or antenatal screening. Tertiary prevention by neonatal screening is also an option where there is direct unbiased evidence for a substantial improvement in prognosis. In addition to this, the information provided during screening is also of value, enabling individuals to make choices that otherwise would not have been available. Having elucidated the natural histories and genetic defects underlying two common, serious genetic disorders, cystic fibrosis and fragile X syndrome, considerable efforts have been channelled into ascertaining the most efficacious method of prevention. To date there is only indirect evidence to suggest that neonatal screening improves prognosis in cystic fibrosis. Similarly, treatment for fragile X syndrome is limited and therefore early identification of the disorder by neonatal screening is unlikely to improve long term outlook. Thus the focus of this review is on primary and secondary preventive methods.

The discovery of new reactions and catalysts has always presented an intriguing challenge to scientists. With the rise of combinatorial chemistry, a new method has emerged that holds considerable promise to facilitate the task since it allows for the simultaneous generation and testing of a large number of compounds. The crucial difficulty lies in establishing general technologies for rapid and reliable screening of libraries to determine the catalytic activity of their members. Several recent publications have addressed this question by using infrared thermography, colorimetric assays and fluorescence spectroscopy. These techniques have not only been applied successfully to the high-throughput screening of parallel compound arrays but also to the screening of one-bead-one-compound libraries. This demonstrates that combinatorial chemistry possesses indeed the potential to establish itself as a powerful tool for the discovery of new catalysts. This review describes the methodologies used so far for the detection of catalytic events and will place particular emphasis on the on-bead screening of one-bead-one-compound libraries.

An on-line sample preparation method utilizing a time-programmed autosampler is described for high throughput liquid chromatography / mass spectrometry (LC / MS). This approach is particularly helpful for the LC / MS analysis of samples which require solvents incompatible with HPLC in the sample preparation process. The on-line sample preparation approach minimizes a bottleneck in throughput and improves sample recovery under some circumstances.

The generation of diversity and its further selection by an external system is a common mechanism for the evolution of the living species and for the current drug design methods. This assumption allows us to label the methods based on generation and selection of molecular diversity as Darwinian ones, and to distinguish them from the structure-based, structure-modulation approaches. An example of a Darwinian method is the inverse QSAR. It consists of the computational generation of candidate chemical structures and their selection according to a previously established QSAR model. New trends in the field of combinatorial chemical syntheses comprise the concepts of virtual combinatorial synthesis and virtual or computational screening. Virtual combinatorial synthesis, closely related to inverse QSAR, can be defined as the computational simulation of the generation of new chemical structures by using a combinatorial strategy to generate a virtual library. Virtual screening is the selection of chemical structures having potential desirable properties from a database or virtual library in order to be synthesized and assayed. This review is mainly focused on graph theoretical drug design approaches, but a survey with key references is provided that covers other simulation methods.

The solubility of drugs in water is of central importance in the process of drug discovery and development from molecular design to pharmaceutical formulation and biopharmacy. The ability to estimate the aqueous solubility and other properties of a promising lead compound affecting its pharmacokinetics is a prerequisite to rational drug design, although it has received much less attention than the prediction of drug-receptor interactions. In this review, methods for the estimation of aqueous solubility of organic compounds are described and limited to approaches, which might be used in the early stage of drug design and development.