3.5 Effects of ningetinib and gefitinib on M1 mediated by efflux
transporters.
M1 exhibited a longer plasma elimination half-life than the parent drug
in ICR mice and in NSCLC patients, possibly because the efflux pathway
of M1 was likely to be blocked. The influence of efflux transporters on
the disposition of ningetinib and M1 was further studied.
To determine whether ningetinib or M1 was a substrate of efflux
transporters, the MDCKII cells stable-overexpressed with human P-gp
(MDCKII-MDR1), BCRP (MDCKII-BCRP) or MRP2 (MDCKII-MRP2) were used for
substrate screening (Table 3). The ER values of ningetinib/M1 were all
greater than 2 apart from that of ningetinib in MDCKII-MRP2 cells. Then
the addition of GF120918 (P-gp inhibitor), KO143 (BCRP inhibitor) and
TAK875 (MRP2 inhibitor) markedly reduced the ER values of M1 in
MDCKII-MDR1, MDCKII-BCRP and MDCKII-MRP2 cells, respectively, while
ningetinib displayed a similar result except for that in MDCKII-MRP2
cells. Thus, both ningetinib and M1 were substrates of P-gp and BCRP.
MRP2 mediated the efflux of M1 but not of ningetinib.
The inhibitory effect of ningetinib and gefitinib on P-gp, BCRP and
MRP2-mediated M1 efflux was further investigated. The logarithm
concentration of ningetinib or gefitinib was plotted on the abscissa,
and the remaining activity of P-gp, BCRP or MRP2 (percentage of efflux
ratio in the inhibitor group to that in the control group) was plotted
on the ordinate, as shown in Fig. 6. Ningetinib displayed a
concentration-dependent inhibition on P-gp-, BCRP- and MRP2-mediated M1
efflux with IC50 values of 0.413 (0–100 μM), 18.7 μM
(0–100 μM) and 3.06 μM (0–30.0 μM), respectively. Similarly, gefitinib
exhibited a weak concentration-dependent inhibition on P-gp- and
BCRP-mediated M1 efflux with IC50 of 5.40 (0–100 μM)
and 9.09 μM (0–30.0 μM), respectively, but showed no inhibition on
MRP2-mediated M1 efflux (0-100 μM). These results, especially the P-gp
inhibition phenomenon, indicated that the parent drug ningetinib could
potently inhibit the canalicular efflux of its metabolite M1 and thereby
elevate its plasma exposure. The inhibitory effect of gefitinib on M1
efflux was significantly weaker than that of ningetinib.