As the existing therapeutic modalities for the treatment of cryptococcal meningitis (CM) have suboptimal efficacy, repurposing existing drugs for the treatment of CM is of great interest. The FDA-approved anthelmintic benzimidazoles, albendazole, mebendazole, and flubendazole, have demonstrated potent but variable in vitro activity against Cryptococcus neoformans, the predominant fungal species responsible for CM. We performed molecular docking studies to ascertain the interaction of albendazole, mebendazole, and flubendazole with a C. neoformans β-tubulin structure, which revealed differential binding interactions and explained the different in vitro efficacies reported previously and observed in this investigation. Despite their promising in vitro efficacy, the repurposing of anthelmintic benzimidazoles for oral CM therapy is significantly hampered due to their high crystallinity, poor pharmaceutical processability, low and pH-dependent solubility, and drug precipitation upon entering the intestine, all of which result in low and variable oral bioavailability. Here, we demonstrate that the anthelmintic benzimidazoles can be transformed into partially amorphous low-melting ionic liquids (ILs) with a simple metathesis reaction using amphiphilic sodium docusate as a counterion. In vitro efficacy studies on a laboratory reference and a clinical isolate of C. neoformans showed 2- to 4-fold lower IC90 values for docusate-based ILs compared to the pure anthelmintic benzimidazoles. Furthermore, using a C. neoformans strain with green fluorescent protein (GFP)-tagged β-tubulin and albendazole and its docusate IL as model candidates, we showed that the benzimidazoles and their ILs reduce the viability of C. neoformans by interfering with its microtubule assembly. Unlike pure anthelmintic benzimidazoles, the docusate-based ILs showed excellent solubility in organic solvents and >30-fold higher solubility in bioavailability-enhancing lipid vehicles. Finally, the docusate ILs were successfully incorporated into SoluPlus, a self-assembling biodegradable polymer, which upon dilution with water formed polymeric micelles with a size of <100 nm. Thus, the development of docusate-based ILs represents an effective approach to improve the physicochemical properties and potency of anthelmintic benzimidazoles to facilitate their repurposing and preclinical development for CM therapy.
Bibliographical noteFunding Information:
We would like to thank BASF Corporation (SoluPlus), Gattefosse USA (Capryol 90 and Labrasol), Croda Chemicals (Cithrol GMO), and IOI Oleo GmbH (Miglyol 812) for providing the gift samples. We would also like to thank Lukasz Kozubowski for the β-tubulin C. neoformans strain (LK126), J. Marina Yoder and Dr. Mallique Qader for helpful discussions and manuscript support and UH Hilo Analytical Lab for the ICP-OES analysis. A.A.D. would like to acknowledge support from a Hawaii Community Foundation Grant (Grant Number 19ADVC-95449) and an IDeA Networks of Biomedical Research Excellence (INBRE) IV Junior Investigator Award (NIGMS grant number P20GM103466). Additional research support came from R01AI134636 and R01NS118538 to K.N. S.A. was supported by a Training Research Educators in Minnesota IRADCA K12GM119955 Fellowship. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
© 2021 American Chemical Society.
- Capryol 90