TABLE 1

In vitro interaction of the humanized mAbs with FcRn

mAb	K_d^{^a}	k_off^{^b} (×10⁻⁴) (1/s)	pH₅₀	% Bound at pH 8^{^c}
	nM
A1 WT	65	39.5	6.39	29
A1 V308P	1.5	2.0	6.87	25
A1 T250Q/M428L	2.7	2.7	6.64	17
B1 WT	195	141	6.25	46
B1 V308P	0.5	1.0	6.77	19
B1 T250Q/M428L	1.7	1.9	6.77	22
C1 WT	66	52.5	6.22	41
C1 V308P	0.6	1.0	6.52	12
C1 T250Q/M428L	4.7	4.3	6.41	8
D1 WT	91	5.5	6.36	45
D1 V308P	0.5	1.0	7.10	28
D1 T250Q/M428L	8.5	8.9	6.73	18
E1 WT	160	176	6.39	66
E1 V308P	1.4	3.0	6.71	20
E1 T250Q/M428L	13.4	1.5	6.67	25

↵a K_d (k_off/k_on · 1 × 10⁹); data determined from SPR kinetic analyses at pH 6.0. No direct binding of FcRn to the IgGs was observed at pH 7.4 in SPR experiments at FcRn concentrations as high as 5 μM.
↵b Determined from SPR kinetic analyses at pH 6.0.
↵c Percentage of the total antibody in preformed complexes that remained FcRn-bound at pH 8 as determined by ELISA.