Antitrypanosomal agent 12 is a C20-phenylthiourea with trypanocidal and cytotoxic activities. Antitrypanosomal agent 12 shows antitrypanosomal activity with 50% growth inhibition (GI 50 ) values of 0.22 μM. Antitrypanosomal agent 12 induces faster cell swelling in bloodstream-form trypanosomes than Salinomycin.