Human therapeutic antibodies have become increasingly common components of early drug discovery and development portfolios in the pharmaceutical and biotech industries. As part of preclinical toxicology assessment of these agents, they are routinely tested in non-human primates, primarily in rhesus or cynomolgus monkeys. In order to assess the pharmacokinetics of the human antibodies in monkey serum, it is necessary to have an assay that is capable of distinguishing the experimentally-introduced human IgG from the endogenous monkey IgG. Cayman's IgG4 (human) Pharmacokinetic ELISA Kit is an immunometric assay which can be used to measure human IgG4 in monkey or rodent plasma and serum without prior sample purification. The standard curve spans the range of 7.8-500 ng/ml, with an LLOQ of 7.8 ng/ml. The assay has been validated in serum from cynomolgus monkeys.