The purpose of this study was to evaluate the pharmacokinetics (PK) of anti-oncostatin M (OSM) IgG1 monoclonal antibodies, CNTO 1119 and its Fc variant (CNTO 8212), which incorporates the LS(Xtend) mutation to extend terminal half-life (T ), after a single intravenous (IV) or subcutaneous (SC) administration in cynomolgus monkeys, and to predict human PK. In study 1, single doses of CNTO 1119 and CNTO 8212 were administered IV or SC at 3 mg/kg to cynomolgus monkeys (n = 3 per group). In study 2, single doses of CNTO 8212 were administered IV at 1, 5 or 20 mg/kg, or SC at 5 mg/kg to cynomolgus monkeys (n = 5 per group). Serial blood samples were collected for assessment of serum concentrations of CNTO 1119 and/or CNTO 8212. A two-compartment population PK model with first-order elimination was utilized to simultaneously describe the serum concentrations of CNTO 1119 and CNTO 8212 over time after IV and SC administration in cynomolgus monkeys. The typical population PK parameter estimates for CNTO 1119 in cynomolgus monkeys were clearance (CL) = 2.81 mL/day/kg, volume of distribution of central compartment (V ) = 31.3 mL/kg, volume of distribution of peripheral compartment (V ) = 23.3 mL/kg, absolute bioavailability (F) = 0.84 and T = 13.4 days. In comparison, the typical population PK parameter estimates for CNTO 8212 in cynomolgus monkeys were CL = 1.41 mL/day/kg, V = 39.8 mL/kg, V = 32.6 mL/kg, F = 0.75 and T = 35.7 days. The mean CL of CNTO 8212 was ~50% lower compared with that for CNTO 1119 in cynomolgus monkeys. The overall volume of distribution (V +V ) for CNTO 8212 was about 32% larger compared with that for CNTO 1119, but generally similar to the vascular volume in cynomolgus monkeys. The T of CNTO 8212 was significantly (p < 0.05) longer by about 2.7-fold than that for CNTO 1119 in cynomolgus monkeys. Thus, the modification of the Fc portion of an anti-OSM IgG1 mAb for higher FcRn binding affinity resulted in lower systemic clearance and a longer terminal half-life in cynomolgus monkeys. CNTO 8212 demonstrated linear PK after a single IV dose (1-20 mg/kg) in cynomolgus monkeys. The predicted human PK parameters suggest that CNTO 8212 is likely to exhibit slow clearance and long terminal half-life in human beings and may likely allow less frequent dosing in the clinical setting.