Synthesis and Structure−Activity Relationship Study of Potent Trypanocidal Thio Semicarbazone Inhibitors of the Trypanosomal Cysteine Protease Cruzain

• Published in: Journal of medicinal chemistry Vol. 45; no. 13; pp. 2695 - 2707
• Main Authors: Du, Xiaohui, Guo, Chun, Hansell, Elizabeth, Doyle, Patricia S, Caffrey, Conor R, Holler, Tod P, McKerrow, James H, Cohen, Fred E
• Format: Journal Article
• Language: English
• Published: WASHINGTON American Chemical Society 20.06.2002; Amer Chemical Soc
• Subjects: Animals; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antiparasitic agents; Biological and medical sciences; Chemistry, Medicinal; Cysteine Endopeptidases; Cysteine Proteinase Inhibitors - chemical synthesis; Cysteine Proteinase Inhibitors - chemistry; Cysteine Proteinase Inhibitors - pharmacology; Life Sciences & Biomedicine; Medical sciences; Models, Molecular; Pharmacology & Pharmacy; Pharmacology. Drug treatments; Protozoan Proteins - antagonists & inhibitors; Science & Technology; Structure-Activity Relationship; Thiosemicarbazones - chemical synthesis; Thiosemicarbazones - chemistry; Thiosemicarbazones - pharmacology; Trypanocidal Agents - chemical synthesis; Trypanocidal Agents - chemistry; Trypanocidal Agents - pharmacology; Trypanosoma cruzi - enzymology; ARREST; DESIGN; VINYL SULFONES; SPECIFICITY; DETERMINANTS; CHAGAS-DISEASE; ANTICONVULSANT ACTIVITIES; 5-NITRO-2-FURALDEHYDE; AGENTS; DERIVATIVES; Nitrogen heterocycle; Cysteine endopeptidases; Active site; Furan derivatives; Non peptide compound; Oxygen heterocycle; Modeling; Pyrrole derivatives; Antiprotozoal agent; Thiophene derivatives; Structure activity relation; Parasiticid; Molecular model; Chemical synthesis; Halogen Organic compounds; Kinetoplastida; Protozoa; Thiosemicarbazone; Enzyme; Benzene derivatives; Enzyme inhibitor; Inhibitor enzyme complex; In vitro; Naphthalene derivatives; Trypanosoma cruzi; Peptidases; Sulfur heterocycle; Hydrolases; Indole derivatives
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/jm010459j

American trypanosomiasis, or Chagas' disease, is the leading cause of heart disease in Latin America. Currently there is an urgent need to develop antitrypanosomal therapy due to the toxicity of existing agents and emerging drug resistance. A novel series of potent thio semicarbazone small-molecule inhibitors of the Trypanosoma cruzi cysteine protease cruzain have been identified. Some of these inhibitors have been shown to be trypanocidal. We initially discovered that 3‘-bromopropiophenone thio semicarbazone (1i) inhibited cruzain and could cure mammalian cell cultures infected with T. cruzi. 3‘-Bromopropiophenone thio semicarbazone showed no toxicity for mammalian cells at concentrations that were trypanocidal. Following this lead, more than 100 compounds were designed and synthesized. A specific structure−activity relationship (SAR) was established, and many potent analogues with IC50 values in the low nanomolar range were identified. Eight additional analogues were trypanocidal in a cell culture assay, and this indicates that aryl thio semicarbazone is a productive scaffold for killing the parasites. Kinetic studies show that these are time-dependent inhibitors. Molecular modeling studies of the enzyme−inhibitor complex have led to a proposed mechanism of interaction as well as insight into the SAR of the thio semicarbazone series. The nonpeptide nature of this series, small size, and extremely low cost of production suggest this is a promising direction for the development of new antitrypanosome chemotherapy.