Fig. 4.

The pharmacokinetic properties of a cytokine can be regulated through switchable association with an antibody Fc-domain. (A) Schematic of a protein design to enable switchable association of an antibody Fc-domain and the cytokine IL-2. (B) An AZ21-IL2 fusion (Ab03) exhibited no detectable binding (ND) to BCL-2 in the absence of venetoclax, as measured by BLI. (C) Ab03 showed potent binding to BCL-2 in the presence of venetoclax. (D) Ab03 was capable of driving signaling downstream of the IL-2 receptor, as indicated by phosphorylation of STAT5 in human T cells. Phospho-STAT5 was measured by intracellular flow cytometry after 15 min of treatment. The experiment was performed once without technical replicates. (E) The plasma clearance rate of Ab03 was slowed in mice that received Ab03, Ab04, and venetoclax. All mice were dosed intravenously at T = 0 h with Ab03 (0.15 mg/kg) and Ab04 (5 mg/kg). One group received venetoclax (5 mg/kg) by oral gavage (once daily starting at T = −2 h), and one group received vehicle control (error bars SEM; n = 5 per group; unpaired two-tailed t test ****P < 0.0001).