Affinity estimates and the M3 selectivity ratio for tiotropium and NVA237 at M1–5 receptor under physiological conditions
The M3 selectivity ratio defines muscarinic receptor subtype selectivity as a ratio of the Ki of the individual subtypes over the Ki at M3 receptor. Data are presented as the mean ± S.E. from a representative of three or more experiments.
| Receptor | pKi | M3 Selectivity Ratio | ||
|---|---|---|---|---|
| Tiotropium | NVA237 | Tiotropium | NVA237 | |
| M1 | 10.34 ± 0.04 | 9.60 ± 0.03 | 1.07 | 0.98 |
| M2 | 10.05 ± 0.03 | 8.70 ± 0.04 | 2.09 | 7.76 |
| M3 | 10.37 ± 0.04 | 9.59 ± 0.05 | 1.00 | 1.00 |
| M4 | 10.18 ± 0.07 | 9.06 ± 0.01 | 1.55 | 3.39 |
| M5 | 9.76 ± 0.07 | 8.91 ± 0.04 | 4.07 | 4.79 |