Table 2.
Kinetic Inhibition Analysis of 6-Substituted Pyrrolo[2,3-d]pyrimidine Analogues Compared to PMX in R2/PCFT4 Cellsa
| substrate | 2′/3′-F | Ki |
|---|---|---|
| PMX | − | 0.12(0.03) |
| 1 | − | 0.14(0.02) |
| 2 | − | 0.46(0.05) |
| 8 | + | 0.17(0.01)* |
| 3 | − | 0.63(0.13) |
| 9 | + | 0.26(0.01)* |
| 4 | − | 0.24(0.02) |
| 10 | + | 0.46(0.06)* |
| 5 | − | 0.36(0.03) |
| 11 | + | 0.25(0.01)* |
| 6 | − | 0.28(0.07) |
| 12 | + | 0.07(0.04)* |
a
[3H]MTX uptake was assayed at using R2/PCFT4 cells at pH 5.5 over 2 min at 37 °C. To determine Ki values, cells were incubated with 0.5 μM [3H]MTX with pyrrolo[2,3-d]pyrimidine antifolates as competitors from 0.05 to 0.5 μM, with results analyzed by Dixon plots. Data are presented as mean values ± standard errors (in parentheses) from four independent experiments. For the fluorinated antifolates (8–12), values significantly different from those of the corresponding non-fluorinated antifolates (2–6, respectively) are marked with * (p < 0.05).