TABLE 2

Transport kinetics for 6-substituted pyrrolo[3,2-d]pyrimidine analogs compared with MTX, PMX, and AGF94

Transport assays were performed using engineered R2/PCFT4 (expresses PCFT only) and R1-11 RFC2 (expresses RFC only) cells. For determinations of K_m and V_max values by Lineweaver-Burk analysis, concentrations of [³H]AGF347 or [³H]MTX were from 0.02 to 0.5 μM for R2/PCFT4 (at pH 5.5) and from 0.25 to 5 µM for R1-11 RFC2 (at pH 7.2). K_i values for each of the drugs were determined by Dixon analysis over a range of concentrations of nonradioactive competitor from 0 to 500 nM (for R2/PCFT4 at pH 5.5) or 0 to 1 µM (for R1-11 RFC2 at pH 7.2) and 0.5 µM [³H]MTX. Results are presented as geometric mean values (with 95% confidence intervals) from three biologic replicates. Pairwise statistical comparisons were performed against MTX (K_m and V_max) and PMX (K_i) using two-sided, unpaired t test.