Ab-mediated neutralization of hepcidin led to increased serum iron in mice and cynomolgus monkeys. (A) The 12B9m treatment did not increase serum iron in Hep1 mice without inflammation. Intravenous 12B9m was administered (5 mg per mouse) to Hep1 mice, and serum iron was measured in different cohorts of mice at baseline, 4 hours, 1 day, 3 days, and 7 days (n = 3 mice per group per time point). (B) The 12B9m treatment increased serum iron in Hep1 AI mice. Hep1 mice were treated with intraperitoneal BA (2 × 10⁸ particles per mouse) and then 1 week later with intravenous 12B9m. Serum iron was sampled as specified in panel A. (C) Mouse monoclonal anti-mouse hepcidin Ab 2C10 treatment increased serum iron in normal C57BL/6 mice. Intravenous 2C10 was administered (5 mg per mouse) to C57BL/6 mice, and serum iron was measured in different cohorts at baseline and 1, 2, 3, and 4 days after treatment (n = 4 mice per group per time point). (D) The 2C10 treatment increased serum iron in C57BL/6 AI mice. Mice were treated with intraperitoneal BA (5 × 10⁸ particles per mouse) and then 1 week later with 2C10, and serum iron was sampled as specified in panel C (n = 5 mice per group per time point). (E) A single dose of 12B9m elevated serum iron in cynomolgus monkeys prior to saturation of Ab with hepcidin. Male cynomolgus monkeys were treated with intravenous 12B9m (50 mg/kg), and blood was collected at baseline, 0.5 hours, 4 hours, 1 day, 2 days, 4 days, and 7 days and assayed for 12B9m concentration, total hepcidin concentration (dissociated from Ab prior to measurement), and serum iron (n = 3 monkeys per group). Statistical comparisons against baseline serum iron values are shown (1-way ANOVA with Dunnett’s post hoc test). *P < .05; **P < .01. All results are shown as mean ± SEM. (F) Cynomolgus monkeys treated repeatedly with 12B9m showed a similar serum iron response in the fourth cycle of treatment as in the first. Cynomolgus monkeys (n = 10) were administered intravenous 12B9m (5, 40, or 300 mg/kg) once weekly. Blood was collected at 4 hours, 1 day, 2 days, 4 days ,and 7 days after the first injection (cycle 1) and fourth injection (cycle 4) and assayed for serum iron. Statistical comparisons against control-treated animals are shown (repeated measures ANOVA [RMANOVA] with Bonferroni post hoc test; colored dots represent time points). P < .05. All results are shown as mean ± SEM.