Synthesis and Biological Evaluation of Prazosin-Derived Antitrypanosomal Agents Putatively Targeting FAZ1

Abstract Current therapeutic interventions for Human African Trypanosomiasis (HAT) are severely limited by emerging drug resistance and profound systemic toxicity, necessitating the urgent development of novel chemotypes. Building upon our previous identification of the alpha-adrenoceptor antagonist Prazosin as a scaffold with off-target activity against Trypanosoma bruceibrucei (T. b. brucei), we have targeted the Flagellum Attachment Zone 1 (FAZ1) filament. As a parasite-specific protein, FAZ1 presents an ideal target for achieving high selectivity and minimizing host toxicity. In this study, we designed and synthesized a series of Prazosin derivatives and characterized their Structure–Activity Relationship (SAR) through biological evaluation against T. b. brucei and mammalian cell lines (HEK293 and RAW264.7). Several derivatives exhibited potent antitrypanosomal activity with IC50 values below 50 nM and a selectivity index exceeding 500-fold relative to mammalian cells. Crucially, these candidates demonstrated negligible affinity for alpha-adrenoceptors at their effective antiparasitic concentrations. Molecular docking simulations, utilizing AlphaFold-generated FAZ1 structures, suggest that these candidates interact specifically with the FAZ1 N-terminal domain. Furthermore, in vivo studies indicated that the lead derivatives extended the lifespan of T. b. brucei-infected mice without the marked toxicity observed with the parent compound, Prazosin. These findings identify prazosin-derived compounds as promising antitrypanosomal agents and suggest FAZ1 as a potential target for future mechanistic validation, warranting further optimization as safer, more effective alternatives for the treatment of HAT.