Proteasome-IN-6 (Compound J-80) inhibits the β5 catalytic subunit of the Trypanosoma brucei 20S proteasome , inibits T. b. brucei , T. b. gambiense and T. b. rhodesiense with EC 50 s of 157 nM, 220 nM and 156 nM, respectively. Proteasome-IN-6 exhibits antitrypanosomal activity in mouse model.