Screening the pandemic response box identified benzimidazole carbamates, Olorofim and ravuconazole as promising drug candidates for the treatment of eumycetoma

Eumycetoma is a chronic subcutaneous neglected tropical disease that can be caused by more than 40 different fungal causative agents. The most common causative agents produce black grains and belong to the fungal orders Sordariales and Pleosporales. The current antifungal agents used to treat eumycetoma are itraconazole or terbinafine, however, their cure rates are low. To find novel drugs for eumycetoma, we screened 400 diverse drug-like molecules from the Pandemic Response Box against common eumycetoma causative agents as part of the Open Source Mycetoma initiative (MycetOS). 26 compounds were able to inhibit the growth of Madurella mycetomatis, Madurella pseudomycetomatis and Madurella tropicana, 26 compounds inhibited Falciformispora senegalensis and seven inhibited growth of Medicopsis romeroi in vitro. Four compounds were able to inhibit the growth of all five species of fungi tested. They are the benzimidazole carbamates fenbendazole and carbendazim, the 8-aminoquinolone derivative tafenoquine and MMV1578570. Minimal inhibitory concentrations were then determined for the compounds active against M. mycetomatis. Compounds showing potent activity in vitro were further tested in vivo. Fenbendazole, MMV1782387, ravuconazole and olorofim were able to significantly prolong Galleria mellonella larvae survival and are promising candidates to explore in mycetoma treatment and to also serve as scaffolds for medicinal chemistry optimisation in the search for novel antifungals to treat eumycetoma. Author summaryMycetoma is a neglected tropical disease characterised by the formation of tumorous swellings and the presence of grains. In fungal mycetoma (eumycetoma), the most common causative agents produce black grains although genetically, these fungi can be very different. Madurella mycetomatis, Madurella pseudomycetomatis and Madurella tropicana belong to the fungal order Sordariales, while Falciformispora senegalensis and Medicopsis romeroi belong to the order Pleosporales. Treatment for eumycetoma is challenging and antifungal therapy with itraconazole or terbinafine is combined with surgery. Unfortunately, cure rates of only 26% are obtained and amputation of the affected area is often needed. Despite the urgent need to find new antifungals for the treatment of eumycetoma, only fosravuconazole is in the pipeline to treat mycetoma. To discover novel compounds with activity against eumycetoma causative agents, the Open Source Mycetoma (MycetOS) initiative was founded. As part of this initiative, we previously tested 800 compounds from the Pathogen Box and Stasis box for their efficacy against M. mycetomatis. In this study, we have tested 400 compounds from the Pandemic Response Box against Madurella mycetomatis, Madurella pseudomycetomatis, Madurella tropicana, Falciformispora senegalensis and Medicopsis romeroi. We have identified four compounds that were able to inhibit all five fungi species in vitro, namely fenbendazole, carbendazim, tafenoquine and MMV1578570. Fenbendazole, MMV1782387, ravuconazole and olorofim were also able to significantly prolong larvae survival in our in vivo Galleria mellonella model. This study showed benzimidazole carbamates as promising candidates to further explore for eumycetoma treatment.

Automated summary

Eumycetoma is a chronic subcutaneous neglected tropical disease caused by various fungal agents. Current antifungal drugs have low cure rates, and there is a need for novel treatments. In this study, four compounds (fenbendazole, carbendazim, tafenoquine, and MMV1578570) were found to inhibit the growth of five species of fungi that cause eumycetoma. These compounds showed promising results in in vivo experiments as well.