New therapeutics to combat malaria are desperately needed. Here we show that the enzyme protein farnesyltransferase (PFT) from the malaria parasite Plasmodium falciparum (P. falciparum) is an ideal drug target. PFT inhibitors (PFTIs) are well tolerated in man, but are highly cytotoxic to P. falciparum. Because of their anticancer properties, PFTIs comprise a highly developed class of compounds. PFTIs are ideal for the rapid development of antimalarials, allowing "piggy-backing" on previously garnered information. Low nanomolar concentrations of tetrahydroquinoline (THQ)-based PFTIs inhibit P. falciparum PFT and are cytotoxic to cultured parasites. Biochemical studies suggest inhibition of parasite PFT as the mode of THQ cytotoxicity. Studies with malaria-infected mice show that THQ PFTIs dramatically reduce parasitemia and lead to parasite eradication in the majority of animals. These studies validate P. falciparum PFT as a target for the development of antimalarials and describe a potent new class of THQ PFTIs with antimalaria activity.

Mortality from prostate cancer is associated with progression of tumors to androgen-independent growth and metastasis. Eicosanoid products of both the cyclooxygenase (COX) and lipoxygenase (LOX) pathways are important mediators of the proliferation of prostate cancer cells in culture and regulate tumor vascularization and metastasis in animal models. Pharmacologic agents that block either COX or LOX products effectively reduce the size of prostate cancer xenografts. Phospholipase A 2 (PLA 2 ) enzymes regulate the provision of arachidonic acid to both COX-and LOX-derived eicosanoids, and a secreted form of the enzyme (sPLA 2 -IIA) is elevated in prostate cancer tissues. Here, we show by immunohistochemistry, in patients receiving androgen ablation therapy, that sPLA 2 -IIA remains elevated in remaining cancer cells relative to benign glands after treatment. Furthermore, sPLA 2 -IIA expression seen in benign glands is substantially decreased after androgen depletion, whereas cytosolic PLA 2 -␣ (cPLA 2 -␣) levels are unchanged. sPLA 2 -IIA mRNA expression is detectable and inducible by androgen (0.01-10 nmol

The role of a cytosolic phospholipase A 2 -α (cPLA 2 -α) in neutrophil arachidonic acid release, plateletactivating factor (PAF) biosynthesis, NADPH oxidase activation, and bacterial killing in vitro, and the innate immune response to bacterial infection in vivo was examined. cPLA 2 -α activity was blocked with the specific cPLA 2 -α inhibitor, Pyrrolidine-1 (human cells), or by cPLA 2 -α gene disruption (mice). cPLA 2 -α inhibition or gene disruption led to complete suppression of neutrophil arachidonate release and PAF biosynthesis but had no effect on neutrophil NADPH oxidase activation, FcγII/III or CD11b surface expression, primary or secondary granule secretion, or phagocytosis of Escherichia coli in vitro. In contrast, cPLA 2 -α inhibition or gene disruption diminished neutrophil-mediated E. coli killing in vitro, which was partially rescued by exogenous arachidonic acid or PAF but not leukotriene B 4 . Following intratracheal inoculation with live E. coli in vivo, pulmonary PAF biosynthesis, inflammatory cell infiltration, and clearance of E. coli were attenuated in cPLA 2 -α (−/−) mice compared with wild type littermates. These studies identify a novel * This work was supported by grants from The Physicians of Ontario through The P.S.I. Foundation (Grant 01-12 (to B. B. R.) and 98-049

The post-translational farnesylation of proteins serves to anchor a subset of intracellular proteins to membranes in eukaryotic organisms and also promotes protein-protein interactions. Inhibition of protein farnesyltransferase (PFT) is lethal to the pathogenic protozoa Plasmodium falciparum. Parasites were isolated that were resistant to BMS-388891, a tetrahydroquinoline (THQ) PFT inhibitor. Resistance was associated with a 12-fold decrease in drug susceptibility. Genotypic analysis revealed a single point mutation in the ␤ subunit in resistant parasites. The resultant tyrosine 837 to cysteine alteration in the ␤ subunit corresponded to the binding site for the THQ and peptide substrate. Biochemical analysis of Y837C-PFT demonstrated a 13-fold increase in BMS-388891 concentration necessary for inhibiting 50% of the enzyme activity. These data are consistent with PFT as the target of BMS-388891 in P. falciparum and suggest that PFT inhibitors should be combined with other antimalarial agents for effective therapy.Malaria causes about 300 million infections annually.1 Approximately 90% of the deaths occur in Africa, with falciparum malaria a major contributor. For decades, malaria chemotherapy has relied on a limited number of drugs. Acquisition and spread of resistance to these drugs is largely responsible for a recent increase in malaria-related mortality (2, 3). This increasing burden caused by drug-resistant parasites has led investigators to seek out novel antimalarial drug targets. Among these are enzymes necessary for cellular division and differentiation. Previous work has demonstrated that the enzyme protein farnesyltransferase (PFT) 2 is a viable drug target for pathogenic protozoa, including the malaria parasite Plasmodium falciparum (4 -8).3 PFT inhibitors (PFTIs) have been developed by the pharmaceutical industry because of their anti-cancer properties (9 -11). Utilizing this existing resource, we have been able to demonstrate that low nanomolar concentrations of tetrahydroquinoline (THQ)-based PFTIs inhibit P. falciparum PFT (PfPFT) and are cytotoxic to parasites both in vitro and in vivo. 3PFT in eukaryotic cells catalyzes the transfer of a 15-carbon isoprenoid lipid unit, a farnesyl group, from farnesyl pyrophosphate (FPP) to the C terminus of a specific set of proteins, including the Ras superfamily G-proteins (12). In addition to the Ras superfamily proteins, which are involved in the cell cycle, another protein that has been shown to be farnesylated is CENP-E, a centromere-associating protein, which plays a critical role in cell cycle progression during the M-phase (13). However, the identification of farnesylated proteins in P. falciparum and their role in mediating PFTI toxicity are currently under investigation.Because of the enzymatic nature of the drug target, we have begun to investigate potential P. falciparum resistance to PFTIs. The THQ PFTI used in this work, BMS-388891 (Fig. 1), is a potent inhibitor of parasite proliferation and causes severe defects in maturation.3 In addition, w...