Development of novel therapeutics for a neglected tropical disease leishmaniasis

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DESCRIPTION (provided by applicant): This application in response to RFA-OD-10-005 addresses two thematic areas from the RFA, Global Health and Translating Basic Science Discoveries into New and Better Treatments. Transmitted by sand fly vectors, Leishmania are obligate intracellular parasites that cause a wide range of diseases, including cutaneous (CL), mucocutaneous (MCL) and visceral leishmaniasis (VL). Over 12 million people currently suffer from leishmaniasis, and approximately 2 million new cases occur each year, making it a major global health problem and a WHO classified neglected tropical disease. Recently, this disease is increasingly seen in canine populations in the US, as well as army personnel serving in Leishmania endemic countries such as Iraq and Afghanistan. Antimonials (Glucantime(tm) and Pentostam(tm)), amphotericin B, and miltefosine are used to treat leishmaniasis. Unfortunately these drugs are toxic and have poor patient compliance because many of them require systemic administration for periods ranging from 3-5 wks, and the emergence of drug-resistant strains is rapidly increasing worldwide. Therefore, there is a strong need for new drugs which are safe, cheap and easy to administer with broad-spectrum activity against different species of Leishmania. In the Yucatan Peninsula, Mayan traditional healers have used Pentalinon andrieuxii root for the topical treatment of CL for many years, indicating that P. andrieuxii contains antileishmanial molecules that could represent potential new drugs for leishmaniasis. We have found that a hexane extract of P. andrieuxii root (PARE) has potent antileishmanial activity both in vitro and in vivo. PARE kills Leishmania in vitro as efficiently as Glucantime(tm), and is also effective against intracellular parasites. Our preliminary data show that topical treatment with PARE is also effective in limiting L. mexicana infection in mice. Work on our ongoing R21 project (Isolation of novel antileishmanial molecules from Pentalinon andrieuxii Root; AI07639-01A1; A. Satoskar, investigator, A.D. Kinghorn, Co- investigator) has already led to the identification of several compounds with leishmanicidal activity in PARE, including two novel sterols. More bioactive molecules are expected to be isolated from the plant before the completion of this R21 project in August 2010. This application in response to RFA-OD-10-005 is to expand our ongoing studies and to undertake preclinical testing on antileishmanial molecules isolated from the plant P. andrieuxii and from fungi from Mycosynthetix Inc. In Aim 1, we will isolate antileishmanial molecules from the different components of the plant and identify their source(s). Aim 2 will use animal models to evaluate the safety and efficacy of these plant-derived molecules, as well as fungi-derived molecules, in treatment of different forms of leishmaniasis, as well as VL caused by parasites resistant to conventional drugs. Aim 3 will determine the mechanism(s) of action of molecules that are active in our animal studies. Our team is uniquely poised to perform the studies due to the complementary expertise in leishmaniasis (Satoskar), phytochemistry (Kinghorn), synthetic chemistry (Fuchs), and mycology/endophytic fungi (Pearce). Our studies should determine how bioactive molecules in P. andrieuxii mediate antileishmanial activity and provide information on their safety and efficacy to treat infections caused by Leishmania strains that are resistant to conventional treatment. Together these data will lay the foundation for advancing future clinical studies on these molecules for better treatment of various forms of leishmaniasis. PUBLIC HEALTH RELEVANCE: Infections caused by an intracellular protozoan parasite Leishmania are a major global health problem, and emergence of drug-resistant parasites is rapidly increasing world-wide. The overall goal of this project is to discover novel antileishmanial drugs from the plant Pentalinon andreuxii for treating different forms of leishmaniasis.