Results of the intact mass LC-FTMS analysis of antibody-payload conjugates.

Peptide conjugates	Antibody	DoC mAb	Labeled mAb	Selectivity Fc/F(ab')2	DoC Fc	DoC F(ab')2
DOTA-PEG10-Fc-III	Trastuzumab	1.20	72%	4.1	0.90	0.22
DOTA-PEG10-Fc-III	Atezolizumab	1.07	70%	5.5	0.90	0.16
DFO-PEG10-Fc-III	Trastuzumab	0.47	39%	0.4 (2.4b)	0.05 (0.33b)	0.14
DFO-PEG10-Fc-IIIa	Trastuzumab	1.52	79%	1.3 (9.2b)	0.20 (1.37b)	0.15
DTPA-PEG10-Fc-III	Trastuzumab	0.87	63%	3.7	0.37	0.10

^a6eq. of DFO-PEG₁₀-Fc-III were used.

^bFc loading was extrapolated.