Subjects will be randomized 1:1 to receive blinded treatment with MMFPK or MMFBSA for up to 53 weeks. The primary endpoint, clinical remission of LN, is measured at the end of Part 1 at week 26. Subjects in the MMFBSA arm who have only partial renal response (PRR) at the end of Part 1 will newly receive MMFPK upon entering Part 2 of the study (week 26 - 53). Subjects with complete renal responses (CRR) at the end of Part 1 will continue the same dosing regimen of MMF (MMFBSA or MMFPK) in Part 2 as was given in Part 1 of the study. Subjects in the MMFPK arm with PRR at the end of Part 1 will enter Part 2 and continue in the MMFPK arm.~Subjects who are LN non-responders by the end of Part 1 at week 26 will be considered treatment failures and discontinued from the study intervention. All subjects who are discontinued from the study intervention for reasons of efficacy or safety will receive LN treatment and monitoring as per the treating physician's decision. However, these subjects will be asked to participate in study visits at weeks 26 and 53/End of Study.
The study is a 1-year 2-part double-blinded placebo controlled 2-arm clinical trial. Treatment arms are (1) MMF dosed as per body-surface area (MMFBSA; 600mg/m2 body surface area per dose about every 12 hours) and (2) pharmacokinetically-guided precision-dosing of MMF (MMFPK; MMF dosed twice daily to achieve an area under the concentration-time curve (AUC0-12h) of MPA >60-70 mg*h/L. The study goal is to determine the safety and efficacy of MMFPK compared to MMFBSA for the treatment of proliferative LN in subjects 8 to <18 years.