RecruitingPhase 2Drug trialThe Pediatric Lupus Nephritis Mycophenolate Mofetil (PLUMM) StudyThe 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 \<21 years.