Safety and efficacy of the bumped kinase inhibitor BKI-1553 in pregnant sheep experimentally infected with Neospora caninum tachyzoites

13 páginas, 2 tablas, 7 figuras.
Neospora caninum is one of the main causes of abortion in cattle, and recent studies have highlighted its relevance as an abortifacient in small ruminants. Vaccines or drugs for the control of neosporosis are lacking. Bumped kinase inhibitors (BKIs), which are ATP-competitive inhibitors of calcium dependent protein kinase 1 (CDPK1), were shown to be highly efficacious against several apicomplexan parasites in vitro and in laboratory animal models. We here present the pharmacokinetics, safety and efficacy of BKI-1553 in pregnant ewes and foetuses using a pregnant sheep model of N. caninum infection. BKI-1553 showed exposure in pregnant ewes with trough concentrations of approximately 4 mu M, and of 1 mu M in foetuses. Subcutaneous BKI-1553 administration increased rectal temperatures shortly after treatment, and resulted in dermal nodules triggering a slight monocytosis after repeated doses at short intervals. BKI-1553 treatment decreased fever in infected pregnant ewes already after two applications, resulted in a 37-50% reduction in foetal mortality, and modulated immune responses; IFN. levels were increased early after infection and IgG levels were reduced subsequently. N. caninum was abundantly found in placental tissues; however, parasite detection in foetal brain tissue decreased from 94% in the infected/untreated group to 69-71% in the treated groups. In summary, BKI-1553 confers partial protection against abortion in a ruminant experimental model of N. caninum infection during pregnancy. In addition, reduced parasite detection, parasite load and lesions in foetal brains were observed.
We gratefully acknowledge Jacobo Sampere from the SALUVETgroup (Complutense University of Madrid, Spain), Teresa Navarro andJosé María González (University of Zaragoza, Spain), Isabel Ayala,Lucas Troya, Clara Colmenero, Dolores González, Natalia Peral,Verónica Pérez, Ignacio Gómez and Isabel Santiago from the Clinical Veterinary Hospital (Complutense University of Madrid, Spain) for their excellent technical assistance, and also Rama Subba Rao Vidadala and Dustin Maly (Department of Chemistry, University of Washington) fortheir assistance in further purification of the study drug. The AnimalExperimentation Service (SEA) at the University of Zaragoza is ac-knowledged for providing their facilities to carry out the reproduction programme. Roberto Sánchez Sánchez is supported by a fellowship from the Spanish Ministry of Education, Culture and Sports (MECD), asa part of the Program of Training of University Teaching Staff (FPU,grant number FPU13/03438). Patricia Vázquez has a Juan de la Cierva-Formación post-doctoral contract (FJCI-2014-20982) from the Spanish Ministry of Economy and Competitiveness (MINECO). Andrew Hemphill is supported by the Swiss National Science Foundation grant(No. 310030 165782). This work was supported by the Public Health Service, National Institutes of Health, Bethesda, MD (grants R01 AI111341 and R01 HD 080670), the U.S. Department of Agriculture(grant 2014-67015-22106) and the Community of Madrid, Spain(PLATESA, S2013/ABI2906).