Cysteine protease inhibitor-3 (Compound 15) is a Cysteine protease inhibitor. Cysteine protease inhibitor-3 inhibits Pf3D7, PfW2, PfFP2 and PfFP3 with IC 50 s of 0.74 μM, 1.05 μM, 3.5 μM, and 4.9 μM, respectively. Cysteine protease inhibitor-3 has anti-plasmodial efficacy against both drug-sensitive and drug-resistant parasites.