Evaluation of efficacy of synthesized compounds and dipeptides. Degradation of Arg-nsP4 (A) and Tyr-nsP4 (B) was monitored in the lysates in the presence of RF-C11 and other compounds (0.5, 1, 5, 10, 25, 50, 75, 100, 150, and 250 μM). IC50 values are indicated.