Inhibitory effects of the phytohormone inhibitors fluridone and inabenfide against Babesia gibsoni in vitro

Abstract Pharmacological options to treat canine babesiosis caused by Babesia gibsoni , are limited. To address this challenge, screening for novel drug candidates and drug targets against B. gibsoni is urgently needed. In this study, we explored the inhibitory effects of two phytohormone inhibitors, fluridone (FLU) and inabenfide (INA), against B. gibsoni in vitro . The half-maximal inhibitory concentration (IC 50 ) values of FLU and INA against B. gibsoni were 60.6 ± 3.4 and 4.3 ± 0.3 μM, respectively. Parasitemia and viability at 24, 48, and 72 h after FLU and INA treatments were significantly lower than those in the control group. The cytotoxicity of FLU and INA was evaluated using the dog-derived Madin-Darby canine kidney (MDCK) cell line; both FLU and INA were less toxic to the MDCK cells than to the control cells. The selectivity index of FLU and INA were higher than 16.5 and 232.6, respectively. In summary, the present study demonstrated that FLU and INA were effective against B. gibsoni infection in vitro and that these compounds might have potential as candidate drugs for the treatment of B. gibsoni .