A, single-step mechanism for simple, reversible, slow binding inhibition. B, ordinary differential equations governing the single-step mechanism of inhibition. C, nonlinear regression for transient dynamics of CID 23631927 using code written in MATLAB to fit in a five-parameter inhibition kinetic model. Reaction progress curves (●) are shown for 8.7 ng/ml human cathepsin L enzyme and 1 μM Z-Phe-Arg-AMC substrate with varying concentrations of CID 23631927 inhibitor.