Long-lasting Inhibition of L-type Amino Acid Transporter 1 by Nanvuranlat is Associated with Prolonged Cellular Retention Counteracted by Cancer-type OATP1B3 in Cholangiocarcinoma Cells.

PURPOSE: Nanvuranlat (JPH203, NVL) is a selective L-type amino acid transporter 1 (LAT1) inhibitor that shows antitumor activity despite rapidly declining blood concentrations. This study investigated whether its long-lasting inhibition of LAT1 is associated with its cellular retention in HuCCT-1 cells, a human cholangiocarcinoma cell line.

METHODS

After NVL exposure and washout, LAT1 activity was evaluated by [14C]leucine uptake, and cell-associated NVL was quantified. The role of cancer-type OATP1B3 (Ct-OATP1B3) was examined using siRNA-mediated knockdown. Tumor retention was assessed in mice bearing HuCCT-1 xenografts.

RESULTS

Following preincubation with 100 µM NVL and a 4-h washout, [14C]leucine uptake was 60.4% of control. Cell-associated NVL amounts were negatively correlated with [14C]leucine uptake in preincubation and washout experiments, suggesting that retained NVL contributes to long-lasting LAT1 inhibition. Ct-OATP1B3 knockdown increased NVL retention after washout and enhanced LAT1 inhibition without affecting initial accumulation. In HuCCT-1 xenografts mice, NVL was retained in tumor tissue despite a rapid decline in plasma concentrations after intravenous administration.

CONCLUSIONS

Prolonged cellular retention of NVL contributes to long-lasting LAT1 inhibition in HuCCT-1 cells. Tumor retention of NVL may partly explain the discrepancy between plasma exposure and antitumor efficacy. Ct-OATP1B3 may modulate NVL retention and sustained pharmacological activity in HuCCT-1 cells.