Here we show the data in terms of %restored activity, where no inhibition is 0% and full inhibition is 100%. GC376 was used as a control inhibitor and yielded an IC 50 = 4.2 ± 1.0 µM. Out of all 878 compounds screened, 6 compounds had activity in the high micromolar range, while Nsp5-3 was the best inhibitor with IC 50 = 37 ± 6 µM. Interestingly, the same compound had given negligible activity in the (cell free) Nsp5 cleavage assays (see Figure , purple line).