Rapid Affinity Maturation of Novel Anti-PD-L1 Antibodies by a Fast Drop of the Antigen Concentration and FACS Selection of Yeast Libraries

Table 4

Apparent affinity and rate constants of anti-PD-L1 IgG bivalent binding to rhPD-L1-Fc.

mAb	ka (1/Ms)^a	kd (1/s)^a	KD2 (nM)^a	KD2 fold change
Wild type	(1.09 ± 0.19) × 10^6	(1.28 ± 0.16) × 10^−3	1.2 ± 0.22	1
3_3	(1.14 ± 0.20) × 10^6	(1.93 ± 0.38) × 10^−4	0.174 ± 0.048	6.89
3_7	(1.03 ± 0.21) × 10^6	(2.87 ± 0.53) × 10^−4	0.287 ± 0.079	4.18
3_14	(1.05 ± 0.20) × 10^6	(1.76 ± 0.39) × 10^−4	0.172 ± 0.049	6.97
3_17	(1.01 ± 0.20) × 10^6	(1.59 ± 0.17) × 10^−4	0.165 ± 0.050	7.27
10_3	(1.10 ± 0.23) × 10^6	(1.48 ± 0.34) × 10^−4	0.139 ± 0.043	8.63
10_12	(1.07 ± 0.20) × 10^6	(2.32 ± 0.39) × 10^−4	0.223 ± 0.058	5.38

^aKinetic (k_a and k_d) and apparent affinity (K_D2) constants for bivalent complexes were calculated by fitting binding curves (Figures 4(h)–4(n)) to the 1 : 1 Langmuir binding model. The apparent affinity constants (K_D2) were calculated from the relationship K_D = k_d/k_a. The reported constants are average values obtained from at least three independent analyses using different biosensors, sample preparations, ligand densities and analyte concentration gradients on the flow cell surfaces. Data are reported with standard deviation. K_D2 fold changes compared to wild type are reported.