High plasma mycophenolate acid concentration in the early phase of induction therapy predicts good renal outcome in lupus nephritis.

Objectives: To identify the prognostic predictive factor of complete renal response (CR) at week 12 by focusing on the plasma mycophenolic acid (MPA) concentration in induction therapy in lupus nephritis. Methods: We prospectively enrolled patients with biopsy-proven LN class III/IV who were hospitalized between 2016 and 2017. As an induction therapy, mycophenolate mofetil was continuously introduced at 2000 mg/day. We measured the MPA plasma concentration at two time points depending on the induction therapy phase, early (week 4) or middle (week 12). The association between these concentrations and CR rate at week 12 was evaluated. Results: Ten patients were enrolled. A significantly higher AUC(0-12) between 0 and 12 h of MPA at the early phase was observed in the patients with CR at week 12 than in those without (p = .03). All the patients with high MPA-AUC(0-12) (> 40 mg h/L) at the early phase achieved CR at week 12, but no such association was found at the middle phase. The multivariate analysis revealed that MPA-AUC0-12 was selected as an independent predictive factor of CR at week 12 (odds ratio: 1.12; 95% confidence interval: 1.01-1.45, p = .02). Conclusion: The high AUC(0-12) of MPA at the early phase of induction therapy may predict good renal response.