Therapeutic drug monitoring of mycophenolate mofetil for the treatment of severely active lupus nephritis

Background Plasma mycophenolic acid (MPA) concentrations may predict therapeutic response in active lupus nephritis (LN). We determined the efficacy and safety of a concentration-controlled MPA regime in the treatment of severely active LN. Methods In this prospective study, 19 biopsy-proven class III/IV LN patients were treated with mycophenolate mofetil (MMF) for 48 weeks. The MMF dosage was based on maximal plasma MPA concentration at 1-hour post dose (MPA-C1). All patients had plasma MPA-C1 levels monitored weekly until achieving the targeted level of >13 mg/L. A low-dose steroid protocol was started at 0.5 mg/kg/day and rapidly tapered to 5 mg/day. Therapeutic response was evaluated at week 24 and week 48. MPA area-under-the curve (MPA-AUC(0-12h)) was measured at week 12 to verify the optimum dosage. Results No death or end-stage kidney disease occurred in this study. Seventeen patients (89%) responded to therapy at week 24 with four (21%) patients having complete response. There was no renal relapse at week 48 and four more patients had converted from partial response to complete response. Seventy eight percent of patients achieved the recommended MPA-AUC(0-12h) level. No association between plasma MPA concentrations and adverse reactions or infections was found. Conclusions MPA-C1 may be a practical monitoring of MPA levels in patients with LN. It is convenient to monitor and may facilitate an optimum estimate of MPA exposure.