Antileishmanial agent-21 (compound 4e) is an antileishmanial agent that targets the Leishmania pteridine reductase 1 (Lm-PTR1). Antileishmanial agent-21 has an anti-folate mechanism, and folic acid and leucovorin can reverse the anti-leishmanial activity of Antileishmanial agent-21. Antileishmanial agent-21 inhibits the Chloroquine -resistant strain of Plasmodium falciparum (RKL9) with an IC 50 of 0.0198-0.096 μM.