High-throughput screening for inhibitors of SARS-CoV-2 nsp13 helicase.
(A) Logistics of the HTS. A custom compound library was screened in 384-well plate format for inhibitors of nsp13 using the FRET-based helicase assay. A nsp13 solution was dispensed into compound-containing plates. After 10 min, reactions were started by addition of a substrate solution and fluorescence readings were taken in 90 s intervals. (B,C) Results of the screens performed at 1.25 µM (B) and 6.25 µM (C) compound concentration. Initial reaction velocity was corrected for well-position and plotted against compound number. (D) Kinetic curves of compounds that showed at least 20% reduction in corrected velocity were inspected manually. As example, time-course data for the compound suramin in the 6.25 µM screen is shown (red curve, data from 20 surrounding wells in black). (E) Summary of HTS results. The process of hit selection for further validation is shown.