These compounds having excellent in vitro activity were evaluated in vivo in the STIB900 mouse model of African trypanosomiasis. The screening was conducted using intraperitoneal dosing at 20 mg/kg daily for four days. The compounds 12, 62 and 64 showed very poor in vivo activity, whereas compound 32 and 66 exhibited excellent in vivo efficacies in the acute mouse model of trypanosomiasis, providing cures of all infected animals.