Supplementary Material for: Population Pharmacokinetics and Dose Optimization of Valganciclovir and Ganciclovir in Lung Transplant Recipients

Objective: The primary goal of this study was to evaluate the pharmacokinetics (PK) of ganciclovir and its prodrug valganciclovir in a large cohort of lung transplant recipients. The secondary goal was to determine the probability of target attainment (PTA) for different pharmacokinetic/pharmacodynamic (PK/PD) targets.
Subject and Methods: A population PK analysis was carried out using NONMEM version 7.4.0. In total, 379 ganciclovir concentrations (194 and 185 concentrations sampled after valganciclovir and ganciclovir administration, respectively) were obtained from 110 patients and were included in the analysis. Monte Carlo simulations (MCS) were performed to assess PTA for (AUC24h) >50 mg·h/L, and AUC24h of 80-120 mg·h/L.
Results: Estimated glomerular filtration rate (eGFR) was found to be the only significant covariate for ganciclovir/valganciclovir clearance. Standard prophylactic and therapeutic ganciclovir/valganciclovir dosing regimens lead to underdosing in patients with reduced eGFR values, particularly below 60 mL/min/1.73 m² for valganciclovir and 70 mL/min/1.73 m² for ganciclovir. For patients with higher eGFR levels, PTA levels are higher (21–35% in therapy and 44-50% in prophylaxis), but the pharmacokinetics show substantial variability, making individual dosing difficult.
Conclusions: Standard prophylactic and therapeutic ganciclovir/valganciclovir dosing regimen leads to underexposure in patients with low eGFR but may be appropriate for patients with higher eGFR values. However, substantial variability in ganciclovir/valganciclovir exposure makes it challenging to achieve efficacy targets in individuals. For this reason, therapeutic drug monitoring (TDM) should be considered. Our model can be integrated into TDM software and, alongside a TDM sample, be used for dosing guidance.