Application of a Plug-and-Play Immunogenicity Assay in Cynomolgus Monkey Serum for ADCs at Early Stages of Drug Development

Table 6

Postbaseline ADA positive responses in cynomolgus monkey Study 1 as detected in the biotin-DIG ELISA and the plug-and-play assay. In Study 1, the biotin-DIG ELISA detected ADAs in two cynomolgus monkeys, one of them dosed with ADC A and the second one with mAb A. These two animals also had positive signals in the plug-and-play assay with good agreement between the ADA titer determined in the biotin-DIG ELISA and the relative ADA level by the ratios calculated in the plug-and-play assay (Figure 8). However, the plug-and-play assay detected ADA responses in animal 1 dosed with mAb A earlier (day 15) than the biotin-DIG ELISA. The plug-and-play assay identified positive responses in 3 additional monkeys, one dosed with mAb A and two dosed with ADC A.

Molecule	Animal	Time point	Biotin-DIG ELISA		Plug-and-play assay
			Screening result (positive/negative)	AU or titer	Screening result (positive/negative)	AU or ratio
mAb A	1	Baseline	Negative	0.054 AU	Negative	0.067 AU
		D15	Negative	0.067 AU	Positive	Ratio of 37.9
		D44	Positive	Titer of 3.99	Positive	Ratio of 42.9
mAb A	2	Baseline	Negative	0.057 AU	Negative	0.196 AU
		D15	Negative	0.065 AU	Positive	Ratio of 2.5
		D44	Negative	0.061 AU	Positive	Ratio of 12.3
ADC A	3	Baseline	Negative	0.065 AU	Negative	0.117 AU
		D15	Negative	0.057 AU	Positive	Ratio of 1.5
		D44	Negative	0.052 AU	Positive	Ratio of 1.3
ADC A	4	Baseline	Negative	0.060 AU	Negative	0.149 AU
		D15	Negative	0.053 AU	Negative	0.119 AU
		D44	Positive	Titer of 1.79	Positive	Ratio of 18.0
ADC A	5	Baseline	Negative	0.065 AU	Negative	0.128 AU
		D15	Negative	0.052 AU	Negative	0.119 AU
		D44	Negative	0.061 AU	Positive	Ratio of 3.5

ADAs = anti-drug antibodies; ADC = antibody-drug conjugate; AU = absorbance units; D = days after dosing or after baseline; mAb = monoclonal antibody; R = ratio.
Ratio = (postbaseline AU/baseline AU).