In Vivo and In Vitro Sensitivity of Fasciola hepatica to Triclabendazole Combined with Artesunate, Artemether, or OZ78

Abstract

Triclabendazole resistance is continually documented from livestock, and hence new treatment strategies for Fasciola hepatica infections are needed. We investigated the effect of triclabendazole combined with artesunate, artemether, or OZ78 compared to that of monotherapy against adult and juvenile F. hepatica in rats. In vitro experiments with triclabendazole and its sulfoxide and sulfone metabolites, each in combination with the peroxides, complemented our study. F. hepatica-infected rats were subjected to single drugs or drug combinations 3 to 4 weeks (juvenile flukes) and >8 weeks (adult flukes) postinfection. Negative binomial regressions of worm and egg counts were used to analyze dose-response relationships and whether the effects of drug combinations were synergistic or antagonistic. The in vitro assays were evaluated by means of viability scales based on fluke motility. Fifty percent effective dose values of 113.0, 77.7, 22.9, and 2.7 mg/kg of body weight were calculated for monotherapy with artesunate, artemether, OZ78, and triclabendazole, respectively, against adult F. hepatica. Likelihood ratio tests revealed synergistic interactions (P < 0.05) of combinations of triclabendazole (2.5 mg/kg) plus artesunate or artemether on adult worm burden. Antagonistic effects on the adult burden and egg output were observed when a lower triclabendazole dose (1.25 mg/kg) was combined with the artemisinins. No significant interactions (P ‫؍‬ 0.07) were observed for OZ78 and triclabendazole combinations and between the triclabendazole effect and the effects of the other partner drugs on juvenile worms. Our in vitro studies of adult worms agreed with the in vivo results, while the in vitro analysis of juvenile worms revealed greater interactions than observed in vivo. In conclusion, single-agent triclabendazole demonstrated a more potent in vivo and in vitro fasciocidal activity than the experimental drugs artesunate, artemether, and OZ78. When combined, synergistic but also antagonistic effects depending on the doses administered were observed, which should be elucidated in more detail in future studies.

Activity of OZ78 analogues against Fasciola hepatica and Echinostoma caproni

“…After 72 h, the majority of adult worms incubated in presence of 50 μg/ml MT04 were dead. It is interesting to note that OZ78 and MT04 did not show any effects against juvenile F. hepatica in vitro in line with results obtained with OZ78 in a recent study (Duthaler et al, 2010). Why juveniles are affected in vivo , but not in vitro is not known, but drug metabolism may account for these differences.…”

“…This dose was chosen based on previous findings documented for OZ78 (ED 50 of 23 mg/kg and ED 99 of 99 mg/kg) (Duthaler et al, 2010). In a next step, doses were titrated down to 50 and 25 mg/kg.…”

Human liver flukes

“…Evidence from animal studies suggests triclabendazole resistance may be overcome by coadministration with the enzyme inhibitor ketonazole (123) . The artemisinins artesunate, artethemer, and OZ78 are active against triclabendazole-resistant Fasciola hepatica (124) , and combination therapy may provide a solution to triclabendazole-resistant flukes, although further work is required (125) .…”

A comparative study on the impact of two artemisinin derivatives, artemether and artesunate, on the female reproductive system of Fasciola hepatica

“…More recently, they have received a considerable amount of attention as potential fasciolicides. A number of semi-synthetic and fully-synthetic artemisinin derivatives have been tested against Fasciola hepatica, and activity demonstrated under in vitro conditions and in rodent (rat) infections, even against a TCBZ-resistant isolate of F. hepatica (Keiser et al, 2006a(Keiser et al, ,b, 2007Duthaler et al, 2010Duthaler et al, , 2012Zhao et al, 2010;Kirchhofer et al, 2011Kirchhofer et al, , 2012Wang et al, 2011). This activity has not been fully or consistently translated to infections in larger ruminants such as sheep (Keiser et al, 2008(Keiser et al, , 2010aMeister et al, 2013).…”