Thursday, July 21, 2016

Cryptosporidium and Toxoplasma parasites are inhibited by a benzoxaborole targeting leucyl-tRNA synthetase

2016 Jul 18. pii: AAC.00873-16. [Epub ahead of print]

The apicomplexan parasites Cryptosporidium and Toxoplasma are serious threats to human health. Cryptosporidiosis is a severe diarrheal disease in malnourished children and immunocompromised individuals, with the only FDA approved drug treatment currently being nitazoxanide. The existing therapies for toxoplasmosis, an important pathology in immunocompromised individuals and pregnant women, also have serious limitations. With the aim of developing alternative therapeutic options to address these health problems, we tested a number of benzoxaboroles, boron-containing compounds shown to be active against various infectious agents, for growth inhibition of Cryptosporidium parasites in mammalian cells. A 3-aminomethyl benzoxaborole, AN6426, with activity in the micromolar range and comparable to nitazoxanide, was identified and further characterised using biophysical measurements of affinity and crystal structures of complexes with the editing domain of Cryptosporidium leucyl-tRNA synthetase (LeuRS). The same compound was shown to be active against Toxoplasma parasites, with the activity being enhanced in the presence of norvaline, an amino acid that can be mischarged by LeuRS. Our observations are consistent with AN6426 inhibiting protein synthesis in both Cryptosporidium and Toxoplasma by forming a covalent adduct with tRNALeu in the LeuRS editing active site, which suggest that further exploitation of the benzoxaboroles scaffold is a valid strategy to develop novel, much needed antiparasitic agents.
Copyright © 2016 Palencia et al.
[PubMed - as supplied by publisher]

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