Potency and equilibrium dissociation constants of test compounds at human recombinant PDE4B1 and the native β2-adrenoceptor in BEAS-2B cells
| Compound | PDE4B1 | β2-Adrenoceptor-Mediated Reporter Activation | [A]50/KIPDE4 | KAβ2/KIPDE4 | ||
|---|---|---|---|---|---|---|
| pIC50 | pKIa | p[A]50b | pKAc | |||
| Indacaterol | ND | ND | 8.55 ± 0.05 (8) | ND | ND | ND |
| β2A | ND | ND | 8.89 ± 0.04 (8) | 7.57 ± 0.05 (12) | ND | ND |
| β2A-S | ND | ND | 9.77 ± 0.07 (8) | 8.44 ± 0.10 (13)* | ND | ND |
| GS-5759 | 8.86 ± 0.06 (3) | 8.94 ± 0.06 (3)d | 10.41 ± 0.07 (8) | 9.12 ± 0.10 (11)* | 0.034 | 0.66 |
| GS-493163 | 6.86 ± 0.05 (3) | 6.88 ± 0.05 (3)d | 9.63 ± 0.11 (7) | 8.43 ± 0.14 (10)* | 0.0018 | 0.028 |
| GSK 256066 | 11.21 ± 0.04 (3) | 11.58 ± 0.09 (3)e | 10.17 ± 0.05 (5) | <5.4f | 25.7 | ≥151315 |
| GSK 256066a | 10.42 ± 0.02 (3) | 10.49 ± 0.02 (3)d | 9.25 ± 0.10 (5) | ND | 17.4 | ND |
ND, not determined; pIC50, log molar concentration of test compund that inhibits PDE4B1 activity by 50%.
↵a pKI values were calculated assuming a KmcAMP for PDE4B1 of 2 µM (Huston et al., 1997).
↵b p[A]50 values were calculated from the graphs in Figs. 4 and 5 (GS-493163 only).
↵c pKA values were calculated from the graphs in Fig. 6.
↵d pKI values were determined by the method of Cheng and Prusoff (1973).
↵e pKI values were determined by the method of Copeland et al. (1995) for a tight-binding inhibitor, where IC50 ≈ [E]. Under this condition, it cannot be assumed that the concentration of free inhibitor in solution and the concentration of inhibitor added are equal because the formation of enzyme-inhibitor complexes becomes significant.
↵f GSK 256066 is >3 × 106-fold selective for PDE4 over the Cerep panel of receptors (Tralau-Stewart et al., 2011).
↵* P < 0.05, pKA values are significantly different from β2A (Student’s unpaired t test).