Enzyme linked immunosorbent assay for the quantification of nivolumab and pembrolizumab in human serum and cerebrospinal fluid

•Nivolumab and pembrolizumab levels in cerebrospinal fluid are much lower than in serum.•Validated enzyme-linked immunoassay can quantify those levels up to 2 ng/mL.•The assay is clinically applicable for pharmacokinetics in serum and cerebrospinal fluid. Immunotherapy with monoclonal antibodies targeting the programmed-death-1 (PD-1) receptor has become standard of care for an increasing number of tumor types. Pharmacokinetic studies may help to optimize anti-PD-1 therapy. Therefore, accurate and sensitive determination of antibody concentrations is essential. Here we report an enzyme linked immunosorbent assay (ELISA) capable of measuring nivolumab and pembrolizumab concentrations in serum and cerebrospinal fluid (CSF) with high sensitivity and specificity. The assay was developed and validated based on the specific capture of nivolumab and pembrolizumab by immobilized PD-1, with subsequent enzymatic chemiluminescent detection by anti-IgG4 coupled with horse radish peroxidase (HRP). The lower limit of quantification for serum and CSF was 2 ng/mL for both anti-PD-1 agents. The ELISA method was validated and showed long term sample stability of >1 year. This method is reliable, relatively inexpensive and can be used in serum and CSF from pembrolizumab and nivolumab treated patients.