ADA detection by a bridging MSD assay
In the screening assay, human plasma samples are incubated for 1 h with a sulfo-tagged MH1 reagent (MH1 is the anti-mesothelin sdAb used in the gavo-cel TRuC) and then added onto a streptavidin plate coated with biotinylated MH1. After 1 h of incubation, the plate is washed to remove unbound material and read on the MSD Imager. The imager reads the ECL signal generated by the sulfo-tagged MH1 reagent and converts it to a relative light unit (RLU). The RLU level is directly proportional to the amount of anti-MH1 antibody in the plasma sample. If samples are found to be negative in the screening assay, testing is complete. Samples found to be positive in the screening assay are tested in a confirmatory assay in the presence/absence of MH1 to confirm specificity. If samples are negative in the confirmatory assay, testing is complete. Samples found to be positive in the confirmatory assay are tested in a titration assay to determine the titer at which positive detection is lost.