Mycophenolate mofetil alongside high-dose corticosteroids: optimizing the management of combination immune checkpoint inhibitor-induced colitis.

Immune checkpoint inhibitor (IO) induced colitis is primarily managed with corticosteroids. Most patients have a rapid resolution of symptoms and do not require additional immunosuppressants. Many patients, however, require prolonged corticosteroid courses to maintain control of toxicity. Mycophenolate mofetil (MMF) is the prodrug of mycophenolic acid; which in turn directly inhibits activated T and B lymphocytes. MMF, in addition to corticosteroids, may enable reduction of corticosteroids without precipitating resurgence of colitis. Metastatic melanoma patients between 1 January 2017 and 31 December 2017 with combination IO-induced colitis were managed with a novel treatment algorithm: upfront oral enteric-coated MMF alongside high-dose corticosteroids. Outcome measures included incidence of colitis flare, time to grade 1 colitis, time to patient-reported normal bowel habit and overall cumulative corticosteroid exposure. Thirteen patients developed high-grade combination IO-induced colitis; 11 were managed with the combination of high-dose corticosteroid and MMF. Median patient age was 59 (range: 28-73) years. Four (36%) developed flare of colitis; flares occurred at a median of 11 (interquartile range: 4.5-16.75) days. All colitis flares responded fully to infliximab (5 mg/kg). The remaining seven patients did not develop colitis flare during corticosteroid wean. All patients were successfully weaned from corticosteroids and none had a resurgence of colitis at 8 weeks following discontinuation of MMF. Concomitant enteric-coated MMF alongside high-dose corticosteroids may hasten the improvement of high-grade colitis to normal bowel habit and reduce the incidence of colitis flare.