Nanobody-based microfluidic human Fc assay for preclinical plasma quantification of IgG1/1.1 and IgG1-Fc-conjugates

Background: Therapeutic antibodies and Fc-conjugates are becoming increasingly popular for disease management and accurate and sensitive pharmacokinetic measurements are critical in lead candidate selection in preclinical drug discovery. Methods and study design: Human Fc-specific intact monoclonal antibodies, polyclonal antibodies, Fab fragments, aptamers, affibodies and nanobodies were screened for potential as biotinylated capture moieties in a microfluidic assay. Test compounds were Bevacizumab, Rituximab, Infliximab as well as an in-house IgG1.1 and an IgG1-drug conjugate. Results: Capture molecules were tested for specificity in plasma matrices from beagle dog, rat, mouse, pig, rhesus monkey and cynomolgus monkey. We find that the llama nanobody provides the best selectivity across across species. The assay usability were verified in cynomolgus monkey pharmacokinetic studies of in-house IgG1.1 and IgG1-fusion molecules. Conclusion: The presented generic nanobody-based assay may find relevance in preclinical testing of future human Fc-containing drug conjugates devoid of Fab fragments and intact monoclonal antibodies.