Alkyne derivatives of SARS-CoV-2 main protease inhibitors including nirmatrelvir inhibit by reacting covalently with the nucleophilic cysteine by Brewitz, L, Dumjahn, L, Zhao, Y, Owen, CD, Laidlaw, SM, Malla, TR, Nguyen, D, Lukacik, P, Salah, E, Crawshaw, AD, Warren, AJ, Trincao, J, Strain-Damerell, C, Carroll, MW, Walsh, MA, Schofield, CJ