Table 2.
Fc binding kinetics to human FcγRIIIa
| pH | Fc variant | FcγRIIIa V158 |
||||
|---|---|---|---|---|---|---|
|
kon ± SD (×105 M–1s–1) |
koff (×10–2 s–1) |
Kd ± SD (nM) |
Kd,SS (nM) |
Chi2Kd,SS (nm2) |
||
| pH 6.5 | Wild-type | 4.5 ± 1.1 | 4.6 ± 1.2 | 102 ± 2.4 | 103 | 0.0303 |
| Acid-Fc | 5.7 ± 1.3 | 7.4 ± 1.1 | 131 ± 9.9 | 115 | 0.0300 | |
| pH 7.4 | Wild-type | 4.9 ± 1.7 | 6.4 ± 1.9 | 134 ± 11.3 | 139 | 0.0384 |
| Acid-Fc | 5.1 ± 1.9 | 11 ± 1.9 | 236 ± 47 | 225 | 0.0297 | |
| pH | Fc variant | FcγRIIIa F158 |
||||
|---|---|---|---|---|---|---|
|
kon ± SD (×105 M–1s–1) |
koff (×10–2 s–1) |
Kd ± SD (nM) |
Kd,SS (nM) |
Chi2Kd,SS (nm2) |
||
| pH 6.5 | Wild-type | 3.0 ± 3.2 | 11.9 ± 1.1 | 401 ± 74 | 418 | 0.0356 |
| Acid-Fc | 3.4 ± 6.7 | 17.7 ± 0.5 | 538 ± 107 | 603 | 0.0298 | |
| pH 7.4 | Wild-type | 2.8 ± 1.9 | 13.4 ± 2.3 | 484 ± 96 | 513 | 0.0445 |
| Acid-Fc | 2.5 ± 4.2 | 22.6 ± 2.2 | 909 ± 154 | 1089 | 0.0347 | |
The association constant(kon), dissociation constant (koff), and equilibrium dissociation constant (Kd = koff/kon) as well as the steady-state dissociation constant (Kd,SS) were determined for hu4D5 antibodies with human IgG1 Fc or acid-Fc and measured by BLI. Mean values and SD (n = 4) are shown, except for Kd,SS values for which the Chi2 values from the fit are shown.