Early development experiments informed on biotherapeutic concentrations to test with a variety of molecules. Signal-to-background ratios obtained in a pooled cynomolgus monkey serum spiked with purified cynomolgus monkey anti-human IgG ADAs at 0, 0.5, 1, and 40 μg/mL and with mAb 2 at 0, 20, 40, 100, 200, and 400 μg/mL. The figure shows signal-to-background ratios increase with increasing concentrations of ADA. The highest signal-to-noise was observed at mAb 2 concentration of 20 μg/mL while higher levels of mAb 2 yielded decrease in the signal-to-noise values at all the ADA levels tested. Based on these data, further experiments with a variety of molecules were performed with biotherapeutic levels up to 20 μg/mL. ADAs = anti-drug antibodies; ADC = antibody-drug conjugate; mAb = monoclonal antibody.