Figure 3.

Correlation of serum concentrations, PD activity, and anti-product antibody responses following a single 10 mg/kg IV dosage of anti-IL-21R antibody Ab-01 to cynomolgus monkeys. Each pre-dose (day -13 for animal 1 and day 1 for animals 2 and 3) and post-dose whole blood sample was divided into four aliquots. The first and second aliquots were treated with either rhuIL-21 (filled circle) or vehicle (a calibrator for RQ calculations), respectively, and were used to assess whether circulating test article affected ex vivo rhuIL-21-induced IL-2RA gene expression (i.e. PD activity). The third aliquot (filled square) was treated with rhuIL-21 and Ab-01, except for day -13 samples for which Ab-02 was used. The fourth aliquot (open triangle) was treated with rhuIL-21 and an IgG control antibody (negative control for the third treatment). Ab-01 serum concentrations (filled diamonds) were measured by a specific ELISA up to days 148, 50, and 92 for animals 1, 2, and 3, respectively; data points with serum concentrations below the LOQ (30 ng/mL) are not shown. Anti-Ab-01 antibodies (neutralizing and non-neutralizing) were assessed by bead-based immunoassay; positive result indicated by "A".