Mycophenolate mofetil versus cyclophosphamide for remission induction in childhood polyarteritis nodosa: An open label, randomised, Bayesian, non‐inferiority trial

Objective Cyclophosphamide (CYC) is used in clinical practice off-label for induction of remission of childhood polyarteritis nodosa (cPAN). Mycophenolate mofetil (MMF) might offer a less toxic alternative: we explored their relative effectiveness in a randomised controlled trial (RCT). Methods International, open-label, Bayesian, RCT investigating the relative effectiveness of MMF and CYC for remission induction in cPAN. Eleven newly-diagnosed patients were randomised (1:1) to MMF or intravenous-CYC; all received the same glucocorticoid regimen. The primary endpoint was remission within 6-months whilst compliant with glucocorticoid taper. Bayesian distributions for remission rates were established a priori for MMF and CYC by experienced clinicians, and updated to posterior distributions on trial completion. Results Baseline disease activity/features were similar between groups. The primary remission endpoint occurred in 4/6 patients (67%) in the MMF group and 4/5 patients (80%) in the CYC group. Time to remission was shorter in the MMF group (median 7.4 weeks versus 17.5 weeks for CYC). No relapses occurred in either group within 18-months. Two serious infections were probably related to MMF. Physical and psychosocial quality-of-life scores were superior in the MMF group compared to CYC at 6-and 18-months. Combining the prior expert opinion with results from MYPAN provided posterior estimates of remission of 71% (90% CrI 51-83%) for MMF; and 75% (90% CrI 57-86%) for CYC. Conclusion Taking the prior opinion and the study results together, rates of remission induction in cPAN on MMF and CYC are similar, and MMF might be associated with better health-related quality of life than CYC.