Mycophenolate mofetil in stem cell transplant patients in relation to plasma level of active metabolite

Objectives: To investigate mycophenolate mofetil (MMF) plasma levels and impact on acute graft versus host disease (aGvHD) after stem cell transplantation (SCT). Methods: SCT patients (n = 14) with aGvHD (≥ II) receiving MMF (1–3 g/d) in addition to cyclosporine, prednisolone, and methotrexate for aGvHD prophylaxis were investigated. Plasma levels of mycophenolic acid (MPA) and its glucuronide metabolite (MPAG) were determined by high-performance liquid chromatography. Results: Overall median steady state pre-dose plasma MPA concentration was 0.47 mg/L and increased within 75 min after administration to 1.64 mg/L. In comparison to patients with skin aGvHD, patients with gut aGvHD had lower MPA concentrations, both pre-dose (p = 0.16) and after 75 min, (p = 0.02). All 7 patients with skin aGvHD but only 2 patients with gut aGvHD responded to MMF. Overall, the pre-dose plasma MPA concentration was significantly (p = 0.007) greater in responders (n = 9) than in non-responders (n = 5). Conclusion: MMF seems to be an effective treatment for aGvHD in SCT patients particular in those patients without gut involvement.