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Antimicrobial Agents and Chemotherapy, June 2006, p. 2146-2155, Vol. 50, No. 6
0066-4804/06/$08.00+0     doi:10.1128/AAC.00020-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Antimicrosporidial Activities of Fumagillin, TNP-470, Ovalicin, and Ovalicin Derivatives In Vitro and In Vivo

Divisions of Comparative Pathology,¹ Microbiology, Tulane National Primate Research Center, Tulane University, Covington, Louisiana,² National Institute of Allergy and Infectious Diseases, Bethesda, Maryland,³ Department of Tropical Medicine, School of Public Health and Tropical Medicine, Tulane University, New Orleans, Louisiana⁴

Received 6 January 2006/ Returned for modification 21 February 2006/ Accepted 15 March 2006

Therapies for microsporidiosis in humans are limited, and fumagillin, which appears to be the most broadly effective antimicrosporidial drug, is considered to be moderately toxic. The purpose of this study was to apply an in vitro drug screening assay for Encephalitozoon intestinalis and Vittaforma corneae and an in vivo athymic mouse model of V. corneae infection to assess the efficacy of TNP-470 (a semisynthetic analogue of fumagillin), ovalicin, and eight ovalicin derivatives. TNP-470, ovalicin, and three of the ovalicin derivatives inhibited both E. intestinalis and V. corneae replication by more than 70% in vitro. Another three of the ovalicin derivatives inhibited one of the two microsporidian species by more than 70%. None of the treated athymic mice survived the V. corneae infection, but they did survive statistically significantly longer than the untreated controls after daily treatment with fumagillin administered at 5, 10, and 20 mg/kg of body weight subcutaneously (s.c.), TNP-470 administered at 20 mg/kg intraperitoneally (i.p.), or ovalicin administered at 5 mg/kg s.c. Of two ovalicin derivatives that were assessed in vivo, NSC 9665 given at 10 mg/kg i.p. daily also statistically significantly prolonged survival of the mice. No lesions associated with drug toxicity were observed in the kidneys or livers of uninfected mice treated with these drugs at the highest dose of 20 mg/kg daily. These results thus support continued studies to identify more effective fumagillin-related drugs for treating microsporidiosis.