Abstract 1368: Population pharmacokinetic-pharmacodynamic analysis of KHK2455 in patients with locally advanced or metastatic solid tumors

BACKGROUND: KHK2455 is an oral selective inhibitor of Indoleamine 2,3-dioxygenase 1 (IDO1) and is being developed as an active immunotherapy to treat advanced or metastatic solid tumors. IDO1 is a rate-limiting enzyme that converts tryptophan (TRP) to kynurenine (KYN) and is linked to immunosuppression. IDO1 inhibition results in immune modulatory effects which may be important in boosting anti-cancer immune responses. The goal of this analysis was to develop a population pharmacokinetics (PK)-pharmacodynamics (PD) model to characterize KHK2455 exposure and its relationship to response in patients with locally advanced or metastatic solid tumors. METHOD: Plasma KHK2455 concentration, plasma KYN and TRP concentration were obtained from 36 subjects with locally advanced or metastatic solid tumors who received KHK2455 at 0.3, 1, 3, 10, 30, or 100 mg QD as a monotherapy run-in followed by combination therapy with anti-CCR4 antibody mogamulizumab in this first in human study of KHK2455. The nonlinear mixed effects modeling approach was used to develop a population PK-PD model using the data from both mono- and combination-therapy. The ratio of KYN to TRP (K:T ratio) was used as a PD marker. RESULTS: The population PK model included one-compartment model with transit compartment absorption, enterohepatic cycling, and linear elimination. The K:T ratio was well described by an indirect response model. Steady state simulations showed that, when compared to baseline, the K:T ratio decreased with increasing KHK2455 dose and reached to a constant nadir at 100 mg dose. CONCLUSIONS: A population PK-PD model was established to characterize the KHK2455 exposure and its relationship to response in patients with locally advanced or metastatic solid tumors. The PK-PD model will enable dose optimization simulations for the planned studies. ACKNOWLEDGEMENTS: We would like to express special appreciation to Dr. Solmaz Sahebjam, MD, for help in publishing this abstract. Citation Format: Krina Mehta, Shoko Koshiba, Maki Hasegawa, Tomonori Tayama, Douglas Marsteller, Floyd Fox, Yi Liu, Sergey Efuni, Denis Healy, Matthew Hruska. Population pharmacokinetic-pharmacodynamic analysis of KHK2455 in patients with locally advanced or metastatic solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1368.