Pharmacological activity of pimecrolimus metabolite pools
The measurements were performed by an IL-2 reporter gene assay. Metabolites were obtained from incubates of [3H]pimecrolimus (10 μM initial concentration) with human liver microsomes (pool from 10 individual livers; 1 mg microsomal protein/ml) for 5, 15, and 60 min. Metabolite pools were isolated by HPLC. The metabolites in fraction 1 (highly polar metabolites) and fraction 2 (moderately polar and nonpolar metabolites but no parent drug) eluted between 0 and approximately 10 min and between approximately 10 and 93 min, respectively, under the chromatographic conditions of the metabolite patterns (cf. Fig. 3).
Incubation Timea | Concentration-Normalized Pharmacological Activity Relative to That of Pimecrolimus | |
|---|---|---|
| min | % | |
| Fraction 1 | 5 | <3 |
| 15 | <1 | |
| 60 | <0.3 | |
| Fraction 2 | 5 | 9 |
| 15 | 4 | |
|
| 60 | 0.5 |
↵ a Conversion of pimecrolimus to metabolites: 59% at 5 min, 84% at 15 min, 100% at 60 min.