Pharmacokinetics of Ganciclovir Following Oral Valganciclovir Versus Intravenous Ganciclovir in Allogeneic Hematopoietic Stem-Cell Transplant Patients with Stable Graft-Versus-Host Disease of the Gastrointestinal Tract.

Cytomegalovirus (CMV) disease can be effectively prevented in allogeneic hematopoietic stem cell transplant (HSCT) patients by ganciclovir (GCV) given as prophylaxis or preemptive therapy. Due to the low bioavailability of oral GCV capsules, GCV is usually administered intravenously (IV) to HSCT patients. Valganciclovir (VGCV) is the valine ester prodrug of ganciclovir. In healthy subjects, HIV-infected patients, and solid-organ transplants, the oral bioavailability of VGCV is about 60%, or 10-fold higher than oral GCV capsules. The bioavailability and total GCV exposure provided by oral VGCV relative to IV GCV in HSCT patients with gastrointestinal (GI) GHVD has not been established. METHODS: HSCT patients were eligible for the study if the following criteria were satisfied: 1) ≥16 years of age; 2) biopsy-proven GHVD of GI tract with nausea and/or diarrhea (300–1500 ml/day) or proven GVHD of skin or liver plus diarrhea with no other explanation; 3) no active CMV infection or disease; 4) neutrophil count ≥1000/μL; 5)creatinine clearance >60 ml/min. Following a standardized breakfast, eligible patients were randomized to receive a single dose of open-label study drug (900 mg of oral VGCV or 5 mg/kg of IV GCV). After a minimum 48 hr. washout period, patients were crossovered to alternate study drug. Blood for levels of GCV and VGCV were obtained predose and then over the 24 hours after dosing. Pharmacokinetic (PK) parameters were derived by noncompartmental methods. RESULTS: Data from 16 patients are currently available. Patient demographics include mean age 45 yrs (range 23 to 58 yrs); males 13, females 3; mean weight 80kg (range 52 to 107 kg); mean creatinine clearance 96 ml/min (range 62 to 184 ml/min). Median time after transplant for study was 303 days (range 102 to 988 days). Mean GCV PK parameters are summarized in the following table. Mean GCV Value (Coefficient of variation in %) Oral VGCV-900 mg IV GCV-5mg/kg Parameter N = 16 N = 16 AUC o -τ (μg•hr/mL) 43.58 (37) 46.74 (40) AUC o-∞ (μg•hr/mL) 46.03 (41) 48.89 (43) C(max) μg/mL) ( 6.45 (30) 12.53 (30) T max (hr) 3.13 (22) 0.97 (8) T½ (hr) 4.97 (31) 5.09 (29) GCV AUC values were similar, although maximum GCV concentrations were higher and acheived earlier with IV GCV. Terminal elimination half-life of GCV with oral VGCV and IV GCV were similar. After 900 mg of oral VGCV, mean plasma Cmax for VGCV was low (0.22 μg/mL), which is consistent with rapid and almost complete metabolism of VGCV to GCV. CONCLUSION: These preliminary results suggest that systemic exposure to GCV after 900 mg of oral VGCV is comparable to that achieved with IV GCV in HSCT patients with stable GI GVHD. Oral VGCV could be a useful alternative to IV GCV in certain HSCT patients requiring prophylaxis or preemptive therapy for CMV.