Pharmacokinetics/pharmacodynamics of tebotelimab and receptor occupancy
Serum concentration of tebotelimab over time after doses ranging from 1 mg to 1,200 mg Q2W was analyzed in 46 patients. The assay for the quantification of tebotelimab in human serum samples uses ELISA technology. In brief, the assay plate is coated overnight with the capture antibody 8E7.1, anti-tebotelimab LAG-3 binding domain. After blocking the non-specific sites with PBS containing Tween 20 and bovine serum albumin (BSA), the plate is incubated with tebotelimab standard calibrators, quality controls and test samples. The immobilized 8E7.1 captures the tebotelimab present in the standard calibrators, quality controls and test samples. The captured tebotelimab is detected by the sequential addition of 2A5-biotin (biotinylated anti-EK linker antibody), followed by streptavidin-HRP. The bound HRP activity is quantified by the luminescence light generation by ELISA PICO substrate. The luminescence light intensity is measured as the RLU using a Victor X4 plate reader. The standard curve is generated by fitting the RLU signal from tebotelimab standards with a four-parameter logistic model with 1/Y2 weighting. The concentration of tebotelimab in the serum samples is determined by interpolation from a standard curve relating the light intensity to the concentration of tebotelimab.Peripheral blood flow cytometry analyses of receptor (PD-1 and/or LAG-3) occupancy in CD4 and CD8 T cells after tebotelimab monotherapy was performed at cycle 2, day 1 (Supplementary Fig. 