Introduction: Little is known about the relationship between exposure levels of mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil (MMF), and comorbidities of systemic lupus erythematosus (SLE) in children. This study aims to explore this association.
Methods: Longitudinal data from SLE children, who were taking MMF for immunosuppression and under therapeutic drug monitoring (TDM), were retrospectively collected. Area under the concentration-time curve of mycophenolic acid (MPA) over 24 hours (AUC0-24h) was estimated with Bayesian methods. Logistic regression and random forest models were used to explore the association between comorbidities and MPA exposure levels.
Results: This study included 107 children with 358 times of follow-up (median age 169.02 months). The incidence of diabetes, acute kidney injury (AKI), or pneumonia was significantly associated with AUC0-24h (odds ratio [OR] 0.991, 95% confidence interval [CI] 0.982-0.999), SLE duration (OR 1.012, 95% CI 1.002-1.022), lymphocyte percentage (OR 0.959, 95% CI 0.925-0.991), plasma albumin levels (OR 0.891, 95% CI 0.843-0.940), use of aspirin (OR 0.292, 95% CI 0.126-0.633) and hydroxychloroquine (OR 0.407, 95% CI 0.184-0.906). The random forest model showed that albumin and AUC0-24h were two important predictors. The case group (with the three comorbidities) had a mean AUC0-24h of 73.63 mg · h/L, while the control group had a mean AUC0-24h of 100.39 mg · h/L.
Conclusions: Increased levels of MPA exposure are associated with decreased incidence odds of diabetes, AKI or pneumonia in SLE children. An AUC0-24h of 100.39 mg · h/L or an AUC0-12h of 50.20 mg · h/L could be used as the targeted exposure level for clinical practice.
Keywords: Systemic lupus erythematosus; children; comorbidities; exposure; mycophenolic acid.