Off-target thiol alkylation by the NADPH oxidase inhibitor 3-benzyl-7-(2-benzoxazolyl)thio-1,2,3-triazolo[4,5-d]pyrimidine (VAS2870)

► VAS2870 suppresses production of ROS in skeletal muscle sarcoplasmic reticulum. ► O2-coupled redox regulation of RyR1 by Nox4 is thereby abrogated. ► VAS2870 directly modifies Cys thiols within RyR1. ► Mass spectrometric analysis demonstrates thiol alkylation by VAS2870. ► Off-target effects of VAS2870 may replicate redox effects of ROS.