Discovery of new antimalarial chemotypes through chemical methodology and library development

Abstract

In an effort to expand the stereochemical and structural complexity of chemical libraries used in drug discovery, the Center for Chemical Methodology and Library Development at Boston University has established an infrastructure to translate methodologies accessing diverse chemotypes into arrayed libraries for biological evaluation. In a collaborative effort, the NIH Chemical Genomics Center determined IC 50 's for Plasmodium falciparum viability for each of 2,070 members of the CMLD-BU compound collection using quantitative high-throughput screening across five parasite lines of distinct geographic origin. Three compound classes displaying either differential or comprehensive antimalarial activity across the lines were identified, and the nascent structure activity relationships (SAR) from this experiment used to initiate optimization of these chemotypes for further development.T he synthesis of compound libraries embodying structural diversity and complexity is one potential avenue to enabling the discovery of potent and selective bioactive agents (1-3). Synthetic methodology aimed at library design and distribution is the focus of the Center for Chemical Methodology and Library Development at Boston University (CMLD-BU). Currently the CMLD-BU maintains a collection of approximately 2,500 compounds derived from reaction methodologies developed in the Center and associated groups. The CMLD-BU has developed a workflow that leverages focused methodology development (4) and identification of new scaffolds and chemical reactions utilizing multidimensional reaction screening (5) for the synthesis of libraries.In a collaboration between the CMLD-BU and the NIH Chemical Genomics Center (NCGC), an effort to discover unique chemotypes which inhibit the viability of P. falciparum, the causative agent of malaria, is underway. Malaria not only inflicts tremendous suffering and morbidity on the human population, but has dramatically influenced the course of civilization with profound sociological and economic implications (6). In response, there have been significant screening efforts for new antimalarial agents (7,8). Effective treatments continue to be needed in part due to acquired resistance of P. falciparum. Identification of molecular targets affecting the viability of malaria is necessary for efficient drug development as is the discovery of chemotypes active across a variety of geographic isolates. With an aim to improve the process of identifying new compounds and targets, we have used quantitative high-throughput screening (qHTS) to achieve pharmacological fingerprints of chemical libraries (9). This technique tests each compound as a seven point titration covering four orders of magnitude in concentration thus allowing sufficient resolving power by virtue of IC 50 determinations to reveal subtle differences in compound activities between parasite lines. A compound with a differential chemical phenotype (DCP) can enable mapping of target genes using genetic recombination wherein the DCP emerges between two or more...

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