Chemical structures of sunitinib, olaparib, mitoxantrone, and bicalutamide (a). MERS protease inhibition by sunitinib, olaparib, mitoxantrone, and bicalutamide (b). Dose response curve B. Percent inhibition, dose response curve of MERS-CoV Plpro inhibition identified from the IC50 protease inhibition assay with dissociation of RLRGG-AMC substrate. Values represent the average ±standard deviation of three replicates.