Table 2. Aldehyde Tag Insertion and Payload Conjugation Minimally Affect Antibody FcRn Binding Characteristics, and Show Improved Dissociation at pH 7.3 Relative to α-HER2-DM1.

measured value	α-HER2 untagged	α-HER2 CH1 tag	α-HER2 CT tag	α-HER2 LC tag	α-HER2 CH1 ADC	α-HER2 CT ADC	α-HER2 LC ADC	α-HER2-DM1 ADC
KDa (association [nM] at pH 6.0)	5.2 ± 1.3	5.2 ± 1.9	5.8 ± 0.7	4.7 ± 1.2	4.8 ± 1.0	4.4 ± 1.1	4.8 ± 1.0	5.0 ± 0.2
% Bound after 5 s at pH 7.3	8.6 ± 0.8	9.9 ± 1.0	9.9 ± 1.7	11.0 ± 1.2	9.5 ± 0.9	12.0 ± 1.4b	10.9 ± 0.6b	14.9 ± 0.8c

^aMean K_D values are not statistically significantly different as determined by one way ANOVA.

^bSignificantly different from αHER2 untagged, p < 0.03, Two-tailed t-test.

^cSignificantly different from all of the other analytes, p < 0.04, Two-tailed t-test.