Project Summary The long-term objective of the proposed research is to develop a new drug for Chagas disease, an infectious disease caused by the parasite Trypanosoma cruzi. Chagas disease is estimated to effect 6-8 million people, mainly in Latin America. The work is motivated by the inadequacy of current therapies with respect to their poor efficacy and tolerability. In this new application we will focus on two chemical scaffolds that were discovered in the hit-to-lead project from a previous NIH supported project. The current lead compounds have potent anti-trypanosomal activity (single or double-digit nanomolar range), good metabolic stability, wide-therapeutic window, and chemical tractability. Safety screens have been reassuring. With further optimization, the goal is to identify at least one final candidate to nominate for clinical development for Chagas disease. In the research plan, the two compound series will have specific issues addressed such as improving solubility, metabolic stability, or other characteristics. The approach will employ classic medicinal chemistry and iterative rounds of compound design, synthesis, and testing. With >200 compounds already made for each of the scaffolds, we have detailed structure activity relationships (SAR) to guide ongoing work. The target is known for one of the compound series (the trypanosome proteasome), and two experimental approaches are planned to identify the target of the other compound series. Compound testing will include in vitro assays for anti-trypanosomal activity, mammalian cell cytotoxicity, solubility, mouse pharmacokinetics, and murine efficacy models following a screening cascade with defined go/no-go criteria. Safety studies and rat toxicology studies will be done towards the end of the funding period on the final lead candidates. At the end of this four-year project, at least one drug candidate will be selected for late-stage preclinical development for Chagas disease.