Exploring the structural requirements of fluorinated benzylidene-thiazolidinediones for selective antitrypanosomal activity.

Human and animal African trypanosomiasis remain serious parasitic diseases requiring the development of new therapeutics with improved efficacy and safety profiles. In this study, a series of novel heterocyclic derivatives based on previously identified thiazolidinedione scaffolds were designed, synthesized, and evaluated for their antitrypanosomal activity against Trypanosoma brucei brucei and T. b. gambiense. Moreover, the synthesized compounds were evaluated for in vitro cytotoxicity against MRC-5 fibroblasts and THP-1-derived macrophages. Several newly investigated thiazolidinedione derivatives demonstrated pronounced activity against both parasite subspecies, with compounds 5c, 5d, and 5e displaying submicromolar potency while maintaining low cytotoxicity toward mammalian cells. The previously reported hit 5a, re-evaluated under the same experimental conditions as a reference compound, remained the most potent derivative. In contrast, replacement of the thiazolidinedione core or extensive structural modifications generally led to reduced activity, highlighting the importance of the original scaffold for antitrypanosomal potency. Additional microsomal and plasma stability studies conducted for selected compounds revealed limitations in metabolic stability despite promising biological activity. Overall, this study expands the structure-activity relationship insights into fluorinated benzylidene-thiazolidinediones and identifies several antitrypanosomal hit compounds suitable for further optimization toward the development of novel agents against African trypanosomiasis.