Paclitaxel has been considered to cause OATP1B-mediated
drug-drug interactions at therapeutic doses; however, its clinical relevance has not been demonstrated. This study aimed to elucidate in vivo inhibition potency of
paclitaxel against OATP1B1 and OATP1B3 using endogenous OATP1B
biomarkers.
Paclitaxel is an inhibitor of OATP1B1 and OATP1B3, with Ki of 0.579 ± 0.107 and 5.29 ± 3.87 μM, respectively. Preincubation potentiated its inhibitory effect on both OATP1B1 and OATP1B3, with Ki of 0.154 ± 0.031 and 0.624 ± 0.183 μM, respectively. Ten patients with
non-small cell lung cancer who received 200 mg/m2 of
paclitaxel by a 3-hour infusion were recruited. Plasma concentrations of 10 endogenous OATP1B
biomarkers-namely,
coproporphyrin I,
coproporphyrin III,
glycochenodeoxycholate-3-sulfate, glycochenodeoxycholate-3-glucuronide, glycodeoxycholate-3-sulfate, glycodeoxycholate-3-glucuronide,
lithocholate-3-sulfate, glycolithocholate-3-sulfate, taurolithocholate-3-sulfate, and chenodeoxycholate-24-glucuronide-were determined in the patients with
non-small cell lung cancer on the day before
paclitaxel administration and after the end of
paclitaxel infusion for 7 hours.
Paclitaxel increased the area under the plasma concentration-time curve (AUC) of the endogenous
biomarkers 2- to 4-fold, although a few patients did not show any increment in the AUC ratios of
lithocholate-3-sulfate, glycolithocholate-3-sulfate, and taurolithocholate-3-sulfate. Therapeutic doses of
paclitaxel for the treatment of
non-small cell lung cancer (200 mg/m2) will cause significant OATP1B1 inhibition during and at the end of the infusion. This is the first demonstration that endogenous OATP1B
biomarkers could serve as surrogate
biomarkers in patients. SIGNIFICANCE STATEMENT: Endogenous
biomarkers can address practical and ethical issues in elucidating transporter-mediated
drug-drug interaction (DDI) risks of anticancer drugs clinically. We could elucidate a significant increment of the plasma concentrations of endogenous OATP1B
biomarkers after a 3-hour infusion (200 mg/m2) of
paclitaxel, a time-dependent inhibitor of OATP1B, in patients with
non-small cell lung cancer. The endogenous OATP1B
biomarkers are useful to assess the possibility of OATP1B-mediated DDIs in patients and help in appropriately designing a dosing schedule to avoid the DDIs.