Fig. 6.

Administered tocilizumab can dominate the IgG1 serum profile but is rapidly cleared.A, deconvoluted Fab mass profiles of P24 at three consecutive sampling points. Each peak represents a unique Fab (based on their unique mass and retention time), and the peak height indicates the clonal concentration. Colored peaks represent tocilizumab, and all other peaks are endogenous IgG1 clones. The pie chart shows the contribution of tocilizumab to the total IgG1 repertoire (based on concentrations). B, monitoring tocilizumab clearance and determination of its half-life in patient serum. T1 was normalized to concentration of 1 and set to day 0. Samples T2 and T3 were normalized to T1. An exponential decay curve was fitted using a nonlinear least squares fit. From this curve, the half-life was determined to be ∼5.9 days for each of the four patients to which tocilizumab had been administered.