Discovery of Anticancer Drugs from Cyanophytes

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DESCRIPTION (provided by applicant): The overall goal of this project is the discovery and development of new anticancer drugs with solid tumor selectivity from leads obtained from collected and cultured marine cyanobacteria and marine microalgae. The need for new and effective anticancer drugs is critical given the paucity of ones active against the major solid tumors in people. Over the course of this grant, 450 taxonomically diverse samples are proposed to be obtained as a source of novel natural products. Micro-elicitation culture methods will be employed on a set of these samples to thoroughly query their secondary metabolomes. Nine fractions plus crude extract are produced from each organism for the anticancer screen (over 900 test samples per year). We employ a unique and novel disk diffusion assay to both identify solid tumor selectivity in the initial extracts and also to direct the isolation of the putative anticancer agent. The assay has been expanded to examine the 7 major solid tumor types in vitro and then in vivo. We expect to both functionally and structurally identify about 6 solid tumor selective compounds per year. While many of the leads will be novel structures, some of the leads may be known compounds or analogues of known compounds; however, very few of these latter compounds will have been evaluated for anticancer activity either in vitro or in vivo. We expect to take all of our lead compounds through a drug development paradigm so as to determine whether they have clinical potential. The first step of drug development requires 15 mg of pure compound to produce in vitro IC50 values and concentration-survival clonogenic studies; and, in vivo maximum tolerated dose and pharmacokinetic information (plasma and tumor levels). The drug is formulated for intravenous administration and an HPLC assay is developed to monitor serum and tissue levels. We expect that all 6 of the yearly discovered in vitro lead compounds will be examined in this pharmacologic phase. These data will be analyzed to determine whether the more expensive efficacy trials in tumor-bearing mice should be undertaken. We expect 3 drugs per year will go to therapeutic efficacy trial in at least one xenograft model. Such a trial will likely require a further collection, culturing or synthetic efforts to gain sufficient material, estimated at 50 - 200 mg. We expect to find one compound per year that has efficacy in the xenograft models, and this lead structure will be chemically explored through synthesis of simple analogs and synthetic modification of the natural product. Therapeutically active drugs will be pursued further in preclinical and clinical development outside of this application.