Exploiting the 2-Amino-1,3,4-thiadiazole Scaffold To Inhibit <i>Trypanosoma brucei </i>Pteridine Reductase in Support of Early-Stage Drug Discovery

Pteridine reductase-1 (PTR1) is a promising drug target for the treatment of trypanosomiasis. We investigated the potential of a previously identified class of thiadiazole inhibitors of Leishmania major PTR1 for activity against Trypanosoma brucei (Tb). We solved crystal structures of several TbPTR1-inhibitor complexes to guide the structure-based design of new thiadiazole derivatives. Subsequent synthesis and enzyme- and cell-based assays confirm new, mid-micromolar inhibitors of TbPTR1 with low toxicity. In particular, compound 4m, a biphenyl-thiadiazole-2,5-diamine with IC50 = 16 μM, was able to potentiate the antitrypanosomal activity of the dihydrofolate reductase inhibitor methotrexate (MTX) with a 4.1-fold decrease of the EC50 value. In addition, the antiparasitic activity of the combination of 4m and MTX was reversed by addition of folic acid. By adopting an efficient hit discovery platform, we demonstrate, using the 2-amino-1,3,4-thiadiazole scaffold, how a promising tool for the development of anti-T. brucei agents can be obtained

Zika antiviral chemotherapy: identification of drugs and promising starting points for drug discovery from an FDA-approved library

Submitted by Adagilson Silva ([email protected]) on 2017-05-11T17:39:14Z No. of bitstreams: 1 27909576 2016 pas-zik.pdf: 4873876 bytes, checksum: 69eb4a73b3e93bb76910afeeda15c7a7 (MD5)Approved for entry into archive by Adagilson Silva ([email protected]) on 2017-05-11T17:39:32Z (GMT) No. of bitstreams: 1 27909576 2016 pas-zik.pdf: 4873876 bytes, checksum: 69eb4a73b3e93bb76910afeeda15c7a7 (MD5)Made available in DSpace on 2017-05-11T17:39:32Z (GMT). No. of bitstreams: 1 27909576 2016 pas-zik.pdf: 4873876 bytes, checksum: 69eb4a73b3e93bb76910afeeda15c7a7 (MD5) Previous issue date: 2016Centro Nacional de Pesquisa em Energia e Materiais. Laboratório Nacional de Biociências. Campinas, SP, Brazil / Instituto Butantan. São Paulo, SP, Brazil.BIOASTER. Paris, France.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Recife, PE, Brasil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Recife, PE, Brasil.Centro Nacional de Pesquisa em Energia e Materiais. Laboratório Nacional de Biociências. Campinas, SP, Brazil / Instituto Butantan. São Paulo, SP, Brazil.Background The recent epidemics of Zika virus (ZIKV) implicated it as the cause of serious and potentially lethal congenital conditions such microcephaly and other central nervous system defects, as well as the development of the Guillain-Barré syndrome in otherwise healthy patients. Recent findings showed that anti-Dengue antibodies are capable of amplifying ZIKV infection by a mechanism similar to antibody-dependent enhancement, increasing the severity of the disease. This scenario becomes potentially catastrophic when the global burden of Dengue and the advent of the newly approved anti-Dengue vaccines in the near future are taken into account. Thus, antiviral chemotherapy should be pursued as a priority strategy to control the spread of the virus and prevent the complications associated with Zika. Methods Here we describe a fast and reliable cell-based, high-content screening assay for discovery of anti-ZIKV compounds. This methodology has been used to screen the National Institute of Health Clinical Collection compound library, a small collection of FDA-approved drugs. Results and conclusion From 725 FDA-approved compounds triaged, 29 (4%) were found to have anti-Zika virus activity, of which 22 had confirmed (76% of confirmation) by dose-response curves. Five candidates presented selective activity against ZIKV infection and replication in a human cell line. These hits have abroad spectrum of chemotypes and therapeutic uses, offering valuable opportunities for selection of leads for antiviral drug discovery

In Vitro and In Vivo Trypanocidal Effects of the Cyclopalladated Compound 7a, a Drug Candidate for Treatment of Chagas' Disease ▿

Chagas' disease, a neglected tropical infection, affects about 18 million people, and 100 million are at risk. The only drug available, benznidazole, is effective in the acute form and in the early chronic form, but its efficacy and tolerance are inversely related to the age of the patients. Side effects are frequent in elderly patients. The search for new drugs is thus warranted. In the present study we evaluated the in vitro and in vivo effect of a cyclopalladated compound (7a) against Trypanosoma cruzi, the agent of Chagas' disease. The 7a compound inhibits trypomastigote cell invasion, decreases intracellular amastigote proliferation, and is very effective as a trypanocidal drug in vivo, even at very low dosages. It was 340-fold more cytotoxic to parasites than to mammalian cells and was more effective than benznidazole in all in vitro and in vivo experiments. The 7a cyclopalladate complex exerts an apoptosis-like death in T. cruzi trypomastigote forms and causes mitochondrion disruption seen by electron microscopy

Novel structural CYP51 mutation in Trypanosoma cruzi associated with multidrug resistance to CYP51 inhibitors and reduced infectivity.

Ergosterol biosynthesis inhibitors, such as posaconazole and ravuconazole, have been proposed as drug candidates for Chagas disease, a neglected infectious tropical disease caused by the protozoan parasite Trypanosoma cruzi. To understand better the mechanism of action and resistance to these inhibitors, a clone of the T. cruzi Y strain was cultured under intermittent and increasing concentrations of ravuconazole until phenotypic stability was achieved. The ravuconazole-selected clone exhibited loss in fitness in vitro when compared to the wild-type parental clone, as observed in reduced invasion capacity and slowed population growth in both mammalian and insect stages of the parasite. In drug activity assays, the resistant clone was above 300-fold more tolerant to ravuconazole than the sensitive parental clone, when the half-maximum effective concentration (EC50) was considered. The resistant clones also showed reduced virulence in vivo, when compared to parental sensitive clones. Cross-resistance to posaconazole and other CYP51 inhibitors, but not to other antichagasic drugs that act independently of CYP51, such as benznidazole and nifurtimox, was also observed. A novel amino acid residue change, T297M, was found in the TcCYP51 gene in the resistant but not in the sensitive clones. The structural effects of the T297M, and of the previously described P355S residue changes, were modelled to understand their impact on interaction with CYP51 inhibitors