Mycophenolate Mofetil Therapy in Children With Idiopathic Nephrotic Syndrome: Does Therapeutic Drug Monitoring Make a Difference?

Background: Idiopathic nephrotic syndrome (INS) necessitates administration of corticosteroids or corticoid-sparing agents in 60% of the cases for prolonged periods resulting in serious adverse effects. Methods: To avoid these complications, we investigated the efficacy and safety of mycophenolate mofetil (MMF) in our retrospective single-center study with 15 patients presenting with complicated courses of INS and aspired to estimate a cutoff level for mycophenolic acid-area under the curve (MPA-AUC) values, which can predict relapses with high sensitivity. Results: Seven of 15 patients stayed in remission while receiving MMF. Average frequency of relapses was 1.39 (0.28-2.5) per year. In case of relapses, patients had lower predose and estimated AUC(0-12) levels of MPA (P = 0.02 and 0.001, respectively). Based on the results of receiver operating characteristic analysis, we consider an estimated MPA-AUC(0-12) lower than 44.6 mg.h.L-1 as a risk factor for future relapses (91% sensitivity, 57% specificity, P = 0.06) because the prevalence of relapse is significantly lower (0.07 versus 0.5, P = 0.02), if the estimated MPA-AUC(0-12) is >44.6 mg.h.L-1. During MMF administration, we did not detect any adverse event requiring discontinuation of treatment. Conclusions: In conclusion, we demonstrate MMF as an alternative treatment for children with complicated INS to maintain remission without serious side effects. Furthermore, we propose a higher therapeutic target range of MPA-AUC(0-12) (>45 mg.h.L-1) than used in transplanted children underlining the crucial role of therapeutic drug monitoring