BACKGROUND: Valganciclovir (VGCV) is the first-line drug for preemptive therapy of cytomegalovirus (CMV) infections. However, even when administered at the dose specified in the package insert, there is significant interindividual variability in the plasma concentrations of ganciclovir (GCV). In addition, correlations have been reported between the area under the concentration-time curve and therapeutic efficacy or adverse events. Therefore, therapeutic drug monitoring (TDM) can be used to improve the efficacy and safety of preemptive VGCV therapy.

OBJECTIVE: This study aims to evaluate whether the dosage adjustment of VGCV based on TDM in patients undergoing preemptive therapy for CMV infections is associated with the successful completion rate of treatment without severe hematological adverse effects.

METHODS: This phase II, single-center, single-arm trial aims to enroll 40 patients admitted at the Department of Rheumatology and Clinical Immunology, Kobe University Hospital, who will receive oral VGCV as preemptive therapy for CMV infections. Participants will begin treatment with VGCV at the dose recommended in the package insert, with subsequent dose adjustments based on weekly TDM results. The primary end point will be the proportion of patients who achieve CMV antigenemia negativity within 3 weeks without severe hematological adverse events. The secondary end points will include weekly changes in CMV antigen levels, total VGCV dose, and duration of preemptive therapy. For safety evaluation, the occurrence, type, and severity of VGCV-related adverse events will be analyzed. Additionally, this study will explore the correlations between the efficacy and safety of preemptive therapy and the pharmacokinetic parameters of GCV, CMV-polymerase chain reaction values, and nudix hydrolase 15 (NUDT15) genetic polymorphisms. The correlation between GCV plasma concentrations obtained from regular venous blood and blood concentrations will be examined using dried blood spots.

RESULTS: This study began with patient recruitment in September 2024, with 5 participants enrolled as of June 16, 2025. The target enrollment is 40 participants, and the anticipated study completion is set for July 2027.

CONCLUSIONS: This is the first study to investigate the impact of TDM intervention in patients receiving VGCV as preemptive therapy. The findings are postulated to provide valuable evidence regarding the utility of TDM in patients receiving VGCV as preemptive therapy.

TRIAL REGISTRATION: Japan Registry of Clinical Trials jRCTs051240080; https://jrct.mhlw.go.jp/latest-detail/jRCTs051240080.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/72549.