Biomarker Analyses in Patients With Advanced Solid Tumors Treated With the LAT1 Inhibitor JPH203.

Background/Aim: Amino acids are among the most important nutrients for supplying energy and building protein blocks in cancers. L-type amino acid transporter (LAT) 1 is known to play a critical role in cancer growth. We have completed the first-in-human phase I study using the LAT1-specific inhibitor JPH2O3. Patients and Methods: We evaluated plasma free amino acids (PFAAs), body mass index (BMI), and efficacy of JPH2O3 in patients enrolled in the phase I study. Results: LAT1-substrate PFAAs and branched chain amino acids (BCAAs) were higher in patients with biliary tract cancer (BTC) than in those with other cancers. High inhibition of uptake of LAT1-substrate PFAAs was associated with survival. BM1 of more than the median was associated with disease control and survival. BCAAs tended to be associated with BMI. Conclusion: BCAAs and BMI are useful predictors of the efficacy of JPH2O3, which shows promising activity against BTC.