Structure–activity relationships of fenarimol analogues with potent in vitro and in vivo activity against Madurella mycetomatis, the main causative agent of eumycetoma

The fenarimol analogue EPL-BS1246 was previously discovered to be potent against Madurella mycetomatis, the causative agent of the neglected tropical disease eumycetoma. Further evaluation of a small set of fenarimol analogues in vivo revealed a correlation between efficacy and the lipophilicity (logD) of the analogues. To explore both this correlation and the series structure-activity relationship (SAR), we have evaluated a total of 185 fenarimol analogues derived from five different daughter chemotypes. Potent (MIC50 < 9 μM) in vitro activity was found for 22 analogues, five of which gave promising results in an in vivo larval survival assay. Again, a trend towards prolonged larval survival (better in vivo activity) was noted in analogues with logD values < 2.5. Insights into the SAR could be gleaned that suggested optimal substituents for the rings forming the fenarimol core.