Azathioprine or mycophenolate mofetil for pediatric autoimmune cytopenia: a propensity score-matched study

Data on the immunosuppressants azathioprine (AZA) and mycophenolate mofetil (MMF) in autoimmune cytopenia (AIC) are limited, and no direct comparison exists. We analyzed the failure-free survival (FFS; time from AZA/MMF initiation to another non-first-line treatment, or death) of both treatments in the prospective nationwide pediatric OBS'CEREVANCE cohort. We included 343 patients (chronic immune thrombocytopenia, n = 161; autoimmune hemolytic anemia, n = 74; Evans syndrome, n = 108). They received AZA (n = 276) or MMF (n = 104; 37 sequentially received both) as monotherapy for a median duration of 11.3 (range, 0.01-149.0) months. Older age was associated with higher FFS for AZA, whereas secondary AIC was associated with higher FFS for MMF. AIC type had no effect. In a propensity score (PS)-matched cohort, AZA and MMF showed similar FFS (adjusted hazard ratio, 0.91; 95% confidence interval, 0.54-1.52; P = .71), with 1-year FFS rates of 73% and 76%, respectively. In subgroup analyses, AZA was associated with higher FFS in PS-matched patients diagnosed at an age of ≥10 years, whereas MMF was associated with higher FFS in PS-matched patients diagnosed at an age of <10 years and in those with confirmed secondary AIC (although with suboptimal matching). Rates of grade ≥3 infection were similar between the 2 drugs, at ∼2% new cases per year. In summary, AZA and MMF demonstrated comparable overall FFS and infection risk. However, our data suggest that AZA may be more beneficial in children diagnosed at an age of ≥10 years, whereas MMF may be more beneficial in those diagnosed at an age of <10 years and possibly in patients with secondary AIC.