Pharmacokinetic-toxicodynamic Modeling to Elucidate the Involvement of Dorsal Root Ganglion Neuron in Oxaliplatin-induced Peripheral Neuropathy.

Background/aim: Oxaliplatin (L-OHP)-induced peripheral neuropathy (OIPN) limits L-OHP dosage due to nerve cell damage in the dorsal root ganglion (DRG) caused by platinum (Pt). Despite various recommended approaches for OIPN management, no effective approach has been established. The aim of this study was to evaluate Pt distribution into DRG after repeat administrations of L-OHP in rats and to develop a pharmacokinetic-toxicodynamic (PK-TD) model using Pt concentrations in DRG to predict neuropathy severity.

Materials And Methods: Male Wistar rats were administered L-OHP (3, 5, or 8 mg/kg i.v.) once weekly. Blood and DRG samples were collected following L-OHP administration. For toxicodynamic (TD) study, OIPN was evaluated using the von Frey test. Plasma and DRG Pt concentrations and thresholds values in von Frey test were used for PK-TD modeling using Phoenix WinNonlin version 8.3 software.

Results: Pt concentration in the DRG increased with repeated administration of L-OHP in a dose-dependent manner, indicating Pt accumulation in DRG following multiple administrations. The PK-TD model, consisting of an indirect response model and a transit compartment model with the DRG compartment, adequately described the temporal changes in OIPN with reliable TD parameters (≤36.4% with coefficient of variation). The maximum drug inhibition model could be employed to establish a quantitative correlation between the Pt content present in the DRG and the toxic potency resulting in OIPN.

Conclusion: The utility of the PK-TD model for predicting neuropathy outcomes was established, suggesting that models composed of the DRG compartment contribute to determining an optimal dosing strategy for reducing OIPN.