SGC-UNC has developed a potent (IC50 40 nM), selective and cell active inhibitor of CHIKV nsp2 protease (SGC-NSP2PRO-1). Vinyl sulfone SGC-NSP2PRO-1 was identified as a potent inhibitor of the nsP2 cysteine protease (nsP2pro) that reduced viral titer against infectious isolates of Chikungunya and other alphaviruses.
A negative control was obtained by alkylating the amide NH with an isopropyl group to give SGC-NSP2PRO-1N which is relatively inactive (IC50 >10 mM) compared to the probe in the protease inhibition assay.
SGC-NSP2PRO-1 was tested against numerous cysteine proteases and found to be highly selective for CHIKV nsp2 protease.
The covalent nature of the inhibitor was established via kinetic analysis, showing time-dependent inhibition with kinact/Ki = 5950 M-1s-1
The position of covalent modification was established as Cys478 following mass spectral analysis of the peptides derived by trypsin digest after chemical probe treatment.
SGC-NSP2PRO-1 potently inhibited the proliferation of the CHIKV virus using a luciferase reporter assay with EC50 of 50 nM. SGC-NSP2PRO-1N was inactive in this assay.
Anirban Ghoshal, Edwin G. Tse, Mohammad Anwar Hossain, Kesatebrhan Haile Asressu, Eric M. Merten, John D. Sears, Stefanie Howell, Sumera Perveen, Jane Burdick,, Noah L. Morales, Sabian A. Martinez, Isabella Law, Bennett J. Davenport, Thomas E. Morrison, Zachary J. Streblow, Daniel N. Streblow, Angie L. Mordant, Thomas S. Webb, Aurora Cabrera, Laura E. Herring, Cheryl H. Arrowsmith, Kenneth H. Pearce, Nathaniel J. Moorman, Mark T. Heise, Rafael M. Couñago, Peter J. Brown and Timothy M. Willson.
A covalent chemical probe for Chikungunya nsP2 cysteine protease with antialphaviral activity and proteome-wide selectivity. Sci Rep 15, 7264 (2025). https://doi.org/10.1038/s41598-025-91673-x