Oral clioquinol is effective in the treatment of a fly model of Candida systemic infection.

Background: Clioquinol was used in the 1950s-1970s as antimicrobial but its oral formulations were withdrawn from the market due to suspected neurotoxicity. Currently, there is possibility of repositioning of oral clioquinol formulations.

Objectives: To evaluate the antifungal activity and toxicological parameters of clioquinol and the other two 8-hydroxyquinoline derivatives using alternative animal models and to study the interaction dynamic of clioquinol with Candida albicans.

Methods: We used Toll-deficient Drosophila melanogaster to test the protective effect of 8-hydroxyquinolines against C. albicans infection. Toxicological parameters were investigated in chicken embryo. A mathematical model-based analysis of the time-kill data of clioquinol was performed to obtain pharmacodynamic characteristics.

Results: Clioquinol fully protected D. melanogaster from the infection. The 8-hydroxyquinolines did not cause changes in opening of the beak and movement of the chicken embryo; however, clioquinol and compound 2 increased arterial pulsation. Compound 3 was lethal at 1 mg mL . Effective concentration found in modelling indicated that clioquinol was highly effective against C. albicans (0.306 μg mL ) in easily achievable serum levels; clioquinol rapidly achieved kill rate reaching the maximum effect after 13 hours.

Conclusions: These results support the potential of clioquinol to be used as a systemic antifungal agent.