This is a randomised, open label, controlled non-inferiority phase III multicentre trial. As primary objective, the study aims to demonstrate that a regimen free of additional oral corticosteroids but with obinutuzumab (and MMF) is non-inferior to a regimen based on oral corticosteroids and MMF in achieving the primary outcome of complete renal response at week 52 without receiving corticosteroids above a prespecified dose. As secondary objectives, the study aims: * To compare the efficacy of the treatments in both arms in terms of: * partial plus complete renal response at week 52; * proteinuria \< 0.8g/g at week 52; * extrarenal flares; * response as defined by a \>4 points reduction in SELENA-SLEDAI score at week 52. * To compare the safety of the treatments in both arms in terms of occurrence of: * toxicity of corticosteroids; * serious Adverse Events; * serious Infectious Episodes; * new damage. * To compare the number of patients with non-adherence to treatment in both arms. * To estimate the efficiency of obinutuzumab in this indication. The ancillary studies will allow: * To implement a biobank (serum, plasma, DNA, cells and urine) and a bank of renal biopsies for studies that will be part of separate research funding bids (patients will be informed that their samples and data may be used for subsequent studies and offered to consent or not). * To identify which target therapeutic levels of MMF best predicts response with least toxicity (ancillary study). * To have long term data on renal function and damage.