ABSTRACT
Available treatments for Chagas' disease and visceral leishmaniasis are inadequate, and there is a pressing need for new therapeutics. Drug discovery efforts for both diseases principally rely upon phenotypic screening. However, the optimization of phenotypically active compounds is hindered by a lack of information regarding their molecular target(s). To combat this issue we initiate target deconvolution studies at an early stage. Here, we describe comprehensive genetic and biochemical studies to determine the targets of three unrelated phenotypically active compounds. All three structurally diverse compounds target the Qi active-site of cytochrome b, part of the cytochrome bc1 complex of the electron transport chain. Our studies go on to identify the Qi site as a promiscuous drug target in Leishmania donovani and Trypanosoma cruzi with a propensity to rapidly mutate. Strategies to rapidly identify compounds acting via this mechanism are discussed to ensure that drug discovery portfolios are not overwhelmed with inhibitors of a single target.
Subject(s)
Antiparasitic Agents/pharmacology , Cytochromes b/antagonists & inhibitors , Drug Discovery , Leishmania donovani/drug effects , Leishmania donovani/genetics , Trypanosoma cruzi/drug effects , Trypanosoma cruzi/genetics , Antiparasitic Agents/chemistry , Antiparasitic Agents/isolation & purification , Chagas Disease/drug therapy , Cytochromes b/genetics , High-Throughput Screening Assays , Humans , Leishmaniasis, Visceral/drug therapyABSTRACT
Acylaminobenzothiazole hits were identified as potential inhibitors of Trypanosoma cruzi replication, a parasite responsible for Chagas disease. We selected compound 1 for lead optimization, aiming to improve in parallel its anti-T. cruzi activity (IC50 = 0.63 µM) and its human metabolic stability (human clearance = 9.57 mL/min/g). A total of 39 analogues of 1 were synthesized and tested in vitro. We established a multiparametric structure-activity relationship, allowing optimization of antiparasite activity, physicochemical parameters, and ADME properties. We identified compound 50 as an advanced lead with an improved anti-T. cruzi activity in vitro (IC50 = 0.079 µM) and an enhanced metabolic stability (human clearance = 0.41 mL/min/g) and opportunity for the oral route of administration. After tolerability assessment, 50 demonstrated a promising in vivo efficacy.
Subject(s)
Chagas Disease/drug therapy , Trypanocidal Agents/chemistry , Trypanocidal Agents/pharmacology , Trypanosoma cruzi/drug effects , Administration, Oral , Animals , Benzothiazoles/chemical synthesis , Benzothiazoles/chemistry , Chlorine/chemistry , Dogs , Female , High-Throughput Screening Assays , Humans , Madin Darby Canine Kidney Cells , Male , Mice , Mice, Inbred C57BL , Mice, Inbred Strains , Microsomes, Liver/drug effects , Parasitic Sensitivity Tests , Structure-Activity Relationship , Trypanocidal Agents/administration & dosage , Trypanocidal Agents/pharmacokineticsABSTRACT
The leishmaniases are diseases that affect millions of people across the world, in particular visceral leishmaniasis (VL) which is fatal unless treated. Current standard of care for VL suffers from multiple issues and there is a limited pipeline of new candidate drugs. As such, there is a clear unmet medical need to identify new treatments. This paper describes the optimization of a phenotypic hit against Leishmania donovani, the major causative organism of VL. The key challenges were to balance solubility and metabolic stability while maintaining potency. Herein, strategies to address these shortcomings and enhance efficacy are discussed, culminating in the discovery of preclinical development candidate GSK3186899/DDD853651 (1) for VL.
