Additionally, in order to minimize the interfering effect of promiscuous inhibitors acting via colloidal aggregate formation [34],[35], we included detergent in the assay buffer

Additionally, in order to minimize the interfering effect of promiscuous inhibitors acting via colloidal aggregate formation [34],[35], we included detergent in the assay buffer. Throughout the entire screen, the assay performed in a robust manner, yielding an average Z value of 0.76. rates derived from a kinetic read were utilized instead of end-point measurements. Actives identified from the screen, along with previously untested analogues, were subjected to confirmatory experiments using the screening assay and subsequently against the individual targets in secondary assays. Several novel active series were identified which inhibited TGR at a range of potencies, with IC50s ranging from micromolar to the assay response limit (25 nM). This is, to our knowledge, the first report of a large-scale HTS to identify lead compounds for a helminthic disease, and provides a paradigm that can be used to jump-start development of novel therapeutics for other neglected tropical diseases. Author Summary Schistosomiasis, also known as bilharzia, is a tropical disease associated with high morbidity and mortality, currently affecting over 200 million people worldwide. Praziquantel is the only drug used to treat the disease, and with KPLH1130 its increased use the probability of developing resistance has grown significantly. The parasites can survive FUT3 for up to decades in the human host due in part to a unique set of antioxidant enzymes that continuously degrade the reactive oxygen species produced by the host’s innate immune response. Two principal components of this defense system, thioredoxin/glutathione reductase KPLH1130 (TGR) and peroxiredoxin (Prx2), have been recently identified and validated as targets for anti-schistosomiasis drug development. In search of inhibitors of this critical redox cascade, we optimized and performed a highly miniaturized automated screen of 71,028 compounds arrayed as 7- to 15-point dilution sets. We identified novel structural series of TGR inhibitors, several of which are highly potent and should serve both as mechanistic tools for probing redox pathways in and as starting points for developing much-needed new treatments for schistosomiasis. The paradigm presented here effectively bridges the gap between academic target identification and the first steps of drug development, and should be applicable to a variety of other important neglected diseases. Introduction Schistosomiasis, also known as bilharzia, a debilitating disease resulting from the infection by the trematode parasite ssp. (and is exceedingly complex, with the parasite going through a number of stages both outside and inside the human host. Once inside humans, it can survive for years, even decades [4]. The need to control schistosomiasis is acute and efforts have been ongoing for years on three main fronts: prevention (via establishment and maintenance of sources of safe potable water), development of a vaccine, and use of drugs to treat the infection [1]. Although the number of schistosomiasis cases worldwide is indeed stunning, the number of drugs available to treat the disease is surprisingly small. Earlier in the 20th century, schistosomiasis was treated with highly toxic antimonial compounds, of which the most common was potassium antimonyl tartrate (PAT, tartar emetic). During the past three decades the only drug used against the infection is praziquantel, which is administered orally, is stable, effective against all major schistosome species in a single dose, and relatively inexpensive [5],[6]. However, because of high reinfection rates, praziquantel must be administered on an annual or semi-annual basis. While its exact mechanism of action is unclear, praziquantel is thought to affect the parasites by disrupting calcium homeostasis [7],[8]. Preliminary reports of praziquantel-resistant KPLH1130 cases, and the generation of praziquantel-resistant parasites in the laboratory [9]C[11] highlight the need for new drugs to treat the disease. Artemisinin has shown promise as a KPLH1130 new drug for schistosomiasis [12] although its use for schistosomiasis may be restricted in areas of malaria transmission so that its use as an antimalarial is not put at risk. Simplified derivatives of artemisinin, the 1,2,4-trioxolanes, show promise and potential selectivity, but these, like the parent compound, are significantly less active against adult schistosome parasites [13]. Oxamniquine, used extensively in Brazil in the past, is effective only against and resistance has been reported further reducing its potential value in schistosomiasis control [10]. Studies of the schistosome life cycle have focused on the fact it can survive for decades in the blood stream of the human host without being severely affected by the immune system and the associated assault by various reactive oxygen species (ROS). Since schistosomes do not have catalase to degrade hydrogen peroxide [14], other mechanisms must exist within the.