Table 1.
NKTR-358 demonstrates attenuated affinity for IL-2Rβ compared with rhIL-2. Human IL-2Rα-Fc chimera, IL-2Rβ-Fc chimera, or both were captured on a Biacore surface plasmon resonance sensor chip and challenged with 3-fold dilutions of IL-2 and NKTR-358. Binding affinities to the IL-2Rα and IL-2Rβ subunits and the heterodimeric IL-2Rαβ were determined by surface plasmon resonance using both kinetic and steady-state measurements [22]. The KD values from both methods were in close agreement, and therefore, analysis was based on average KD values from both measurements. The ratio between kd and ka were used to calculate the KD values. Table shows ratios of KD values. ka, association rate constant; kd, dissociation rate constant; KD, equilibrium dissociation constant.
| Receptor | rhIL-2 (KD, nM) | NKTR-358 (KD, nM) | Ratio NKTR-358/rhIL-2 |
|---|---|---|---|
| α | 4.3 | 7300 | 1700 |
| β | 530 | 88,000 | 170 |
| αβ | 0.071 | 1700 | 24,000 |