FlipGFP protease assay for evaluating in vitro inhibitory activity against SARS-CoV-2 M^pro and PL^pro

FlipGFP assay characterizes the intracellular drug target engagement to M^pro and PL^pro and can be performed in the biosafety level 1/2 settings. Here, we provide the detailed protocol for the cell-based FlipGFP assay to identify and characterize SARS-CoV-2 M^pro and PL^pro inhibitors. We describe steps for cell passage and seeding, transfection, addition of compounds, and their incubation and timing. We then detail the quantification of the fluorescence signal of the assay For complete details on the use and execution of this protocol, please refer to Ma et al.¹