In Vitro and In Vivo Activities of E5700 and ER-119884, Two Novel Orally Active Squalene Synthase Inhibitors, against Trypanosoma cruzi

Abstract

Chagas' disease is a serious public health problem in Latin America, and no treatment is available for the prevalent chronic stage. Its causative agent, Trypanosoma cruzi, requires specific endogenous sterols for survival, and we have recently demonstrated that squalene synthase (SQS) is a promising target for antiparasitic chemotherapy. E5700 and ER-119884 are quinuclidine-based inhibitors of mammalian SQS that are currently in development as cholesterol-and triglyceride-lowering agents in humans. These compounds were found to be potent noncompetitive or mixed-type inhibitors of T. cruzi SQS with K i values in the low nanomolar to subnanomolar range in the absence or presence of 20 M inorganic pyrophosphate. The antiproliferative 50% inhibitory concentrations of the compounds against extracellular epimastigotes and intracellular amastigotes were ca. 10 nM and 0.4 to 1.6 nM, respectively, with no effects on host cells. When treated with these compounds at the MIC, all of the parasite's sterols disappeared from the parasite cells. In vivo studies indicated that E5700 was able to provide full protection against death and completely arrested the development of parasitemia when given at a concentration of 50 mg/kg of body weight/day for 30 days, while ER-119884 provided only partial protection. This is the first report of an orally active SQS inhibitor that is capable of providing complete protection against fulminant, acute Chagas' disease.Chagas' disease, a parasitic disease caused by the kinetoplastid protozoan Trypanosoma (Schizotrypanum) cruzi, is still one of the most serious public health problems in Latin America, despite recent advances in the control of the vectorial and transfusional transmission of the parasite (36). There are ca. 18 million people currently infected with T. cruzi, most of them in the chronic phase, which can lead to severe heart and gastrointestinal lesions (36). Current chemotherapy, based on the nitrofuran nifurtimox (Bayer) and the nitroimidazole benznidazole (Roche), is unsatisfactory as these compounds are effective only for recent infections and have frequent toxic side effects (21,24,28). Studies have shown that T. cruzi has a strict requirement for specific endogenous sterols (ergosterol and analogs) for survival and growth and cannot use the abundant supply of cholesterol present in its mammalian host (21)(22)(23)25). Ergosterol biosynthesis inhibitors with potent in vitro activity and special pharmacokinetic properties in mammals (large volumes of distribution and long half-lives) can induce the radical cure of parasitic infection in experimental animal models of both acute and chronic 25). Squalene synthase (SQS; EC 2.5.1.21) catalyzes a head-to-head reductive dimerization of two molecules of farnesyl pyrophosphate (FPP) in a two-step reaction to form squalene (Fig.

Quinuclidine Derivatives as Potential Antiparasitics

“…Furthermore, quinuclidine derivatives developed by Eisai Company, Ltd. (Tokyo, Japan) as cholesterol and triglyceride-lowering agents (E5700 and ER119884; Fig. 1) have been shown to have activity against T. cruzi in vitro, and one derivative was able to prevent the development of parasitemia and induced full survival in a rodent model of acute Chagas' disease (36) (Fig. 1).…”

“…Encouragingly, a number of enzymes in the sterol biosynthetic pathway have been studied as potential drug targets in these organisms and have shown great promise. Thus, 14␣-demethylase (9, 17-20, 29, 30, 38, 41, 42, 45), sterol 24-methyltransferase (9, 20-24, 32, 44, 46, 48), 3-Hydroxy-3-methyl-glutaryl coenzyme A reductase (8, 40), squalene epoxidase (18, 39), squalene synthase (SQS) (7,31,33,36,37), and farnesyl pyrophosphate synthase (25-27, 50) have been studied both individually and in combination, with various degrees of success.The enzyme SQS, which catalyzes the condensation of two molecules of farnesyl pyrophosphate to produce squalene, has been identified as a potential drug target for the inhibition of cholesterol biosynthesis in humans (5). The activities of a variety of compounds, including bisphosphonates, benzylamines, squalestatins, and quinuclidines, against mammalian enzymes have been investigated.…”

New Treatments for Chagas Disease and the Relationship between Chagasic Patients and Cancers

“…In fact, these drugs exhibited IC50 values of 4.3 µM (meta-substituted) and 3.7 µM (para-substituted), respectively being 4-fold more potent than the well-known antiparasitic agent WC-9 (lead compound), used as a positive control, under the same assay conditions. The same behavior was observed against the epimastigote form of T. cruzi where the analogs were more potent than WC-9 but in a lesser extent than against amastigotes [72]. After analyzing the structure-activity relationship of WC-9 and its fluorine-containing analogues has become possible to observe that the increase of Log P values optimizes the efficiency of the lead compound.…”

“…In addition, it was demonstrated that aryloxyethyl thiocyanate derivatives are potent inhibitors of T. cruzi proliferation [72]. It has been found that growth inhibition of T. cruzi epimastigotes induced by 4-Phenoxyphenoxyethyl thiocyanate also known as WC-9 was associated with a reduction in the content of the parasite's endogenous sterols due to a specific blockade of their de novo synthesis at the level of squalene synthase [73].…”

“…[152]. Thiocyanate derivatives have also proved effective against the proliferation of T. cruzi, although their mechanism of action has not yet been determined [72].…”