Receptor occupancy and blocking of STAT5 signaling by an anti-IL-7 receptor α antibody in cynomolgus monkeys.
BACKGROUND
Interleukin-7 receptor α (IL-7Rα) is associated with autoimmune disease. Blocking its activation by interleukin-7 (IL-7) with a therapeutic monoclonal antibody may reduce pathogenic T cells and effectively control the autoimmune response in these disorders.


METHODS
Two flow cytometry-based assays were developed and implemented to evaluate the interaction between cell surface IL-7Rα and an anti-IL-7Rα monoclonal antibody (Ab1). The receptor occupancy assay utilized competing and noncompeting commercial detection antibodies for "free" and "total" IL-7Rα, respectively. STAT5 phosphorylation (pSTAT5) was measured as a proximal biomarker of IL-7Rα inhibition by Ab1.


RESULTS
Monkeys administered Ab1 had no free IL-7Rα detectable on the CD3+ T cell surface at 0.25 hours postdose through day 4, in all treatment groups. Ab1 treatment resulted in a significant reduction in total IL-7Rα, dropping to 53%, 44%, and 55% on day 4 at 0.3, 3, and 30 mg/kg, respectively, compared to predose levels. There were treatment-related decreases in the ability of IL-7 to induce STAT5 phosphorylation in both CD4+ and CD8+ T cells in monkey blood samples from all treated animals from 0.25 hours through Day 4 postdose.


CONCLUSIONS
The nonclinical receptor occupancy assay was developed and applied to detect free and total IL-7Rα on the surface of CD3+ T cells in cynomolgus monkeys treated with Ab1. The results showed good correlation with the phosphorylation of STAT5 and serum concentration of Ab1. The approach for IL-7Rα occupancy and pSTAT5 measurements established in monkeys can be utilized in clinical trials for pharmacokinetic/pharmacodynamic evaluation of Ab1 effect in humans.
Pharmacokinetics, Dynamics, and Metabolism, Pfizer, La Jolla, California.
Brent
B
Kern
Pharmacokinetics, Dynamics, and Metabolism, Pfizer, La Jolla, California.
Wenlin
W
Li
Drug Safety Research and Development, Pfizer, Groton, Connecticut.
Christine
C
Bono
Rinat, Experimental Medicine, Pfizer, San Francisco, California.
Li-Fen
LF
Lee
Pharmacokinetics, Dynamics, and Metabolism, Pfizer, La Jolla, California.
Eugenia
E
Kraynov
D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology* / Q000628:therapy; D005434:Flow Cytometry; D006801:Humans; D015851:Interleukin-7 / Q000276:immunology; D008252:Macaca fascicularis / Q000276:immunology; D010766:Phosphorylation; D020395:Receptors, Interleukin-7 / Q000037:antagonists & inhibitors / Q000276:immunology*; D050799:STAT5 Transcription Factor / Q000037:antagonists & inhibitors / Q000276:immunology*
D000911:Antibodies, Monoclonal; D015851:Interleukin-7; D020395:Receptors, Interleukin-7; D050799:STAT5 Transcription Factor
(IL-7Rα); IL-7 receptor α; monoclonal antibody; multiple sclerosis; pSTAT5; receptor occupancy; type I diabetes