Human African trypanosomiasis (HAT), also known as sleeping sickness, is a parasitic disease that causes significant mortality in sub- Saharan Africa. A previous publication from IRBM laboratory reported the identification of 2-(1H-imidazo-2-yl)piperazines as a new series of potent T. brucei growth inhibitors. This work describes the structure–activity relationship (SAR) around the hit compound 1, which led to the identification of the optimized compound 18, a single digit nanomolar inhibitor, not cytotoxic and with optimal in vivo profile that made it a suitable candidate for efficacy studies in animal models mimicking the second stage of disease.