Head-to-head comparison of PDE5-specific inhibitor potencies (affinities)
Student's t tests indicated that KD values for each unlabeled inhibitors were significantly different from each other with the exception of the KD value of sildenafil obtained from ½ EC50, which was significantly different (p < 0.05) from all other KD and IC50 values for sildenafil. The IC50 value for vardenafil was significantly different (p < 0.05) from all KD values for vardenafil.
| IC50 | KD from Isotherm | KD from ½ EC50 | KD from Exchange-Dissociation Average | IC50 from Literature | |
|---|---|---|---|---|---|
| nM | nM | nM | nM | nM | |
| Sildenafil | 3.7 ± 1.4 | 4.8 ± 0.8 | 11.6 ± 0.7 | 3.1 ± 0.29 | 1-9 |
| Tadalafil | 1.8 ± 0.4 | 2.4 ± 0.6 | 2.72 ± 0.3 | 1.7 ± 0.37 | 1-7 |
| Vardenafil | 0.091 ± 0.031 | 0.38 ± 0.07 | 0.42 ± 0.1 | 0.32 ± 0.01 | 0.1-0.8 |