Optimal exposure of mycophenolic acid for induction therapy of childhood lupus nephritis patients: an observational cohort study.

OBJECTIVES: Mycophenolic acid (MPA) is recommended for lupus nephritis (LN) treatment, but with large inter-individual variability in pharmacokinetics (PK). The aim of this study is to reveal the relationship between MPA exposure and disease response and adverse drug reactions in pediatric LN patients.

METHOD: This was a population-based observational cohort study. A total of 86 pediatric LN patients treated with mycophenolate mofetil (MMF) for induction therapy were enrolled. The area-under the concentration-time curve (AUC) was calculated using MPA concentrations according to a limited sampling strategy. Receiver operating characteristic analysis was performed to assess the MPA-AUC threshold values. The cumulative incidence of renal remission and inactive SLE over time was evaluated by Kaplan-Meier's analysis.

RESULTS: MPA-AUC was identified as an independent factor associated with renal remission and lupus activity at 6 and 12 months after MMF treatment, and the improved renal remission rates was correlated with higher MPA-AUC, with thresholds of 29.81 and 30.63 μg·h·mL - 1 at 6 and 12 months, respectively. Furthermore, the thresholds for maintaining the hypoactive state of LN were 30.96 and 31.19 μg·h·mL - 1at 6 months and 12 months, respectively. Patients reaching target thresholds for MPA-AUC achieved renal response or stable disease earlier. In addition, the MPA-AUC threshold for decreasing MMF-related adverse reactions was 50.80 μg·h·mL - 1.

CONCLUSION: The initial and long-term treatments of pediatric LN patients with MMF should be individualized according to the MPA-AUC, and the recommended MPA exposure is 31.19-50.80 μg·h·mL - 1.