Background: NIVO and IPI are approved as monotherapy and in combination for treatment of MEL. These treatments are associated with select (potentially immune-related) adverse events (AEs) of the GI tract, most commonly diarrhea and colitis. We describe the management of GI toxicity in patients (pts) treated with NIVO+IPI or IPI from phase II (CheckMate 069) and III (CheckMate 067) trials. Methods: Pts received NIVO 1 mg/kg + IPI 3 mg/kg Q3W x 4, followed by NIVO 3 mg/kg Q2W until progression or unacceptable toxicity, or IPI 3 mg/kg Q3W x 4, followed by placebo. Minimum follow-up was 2 yrs for CheckMate 069 and 18 months for CheckMate 067. Results: Of 407 pts treated with NIVO+IPI, 195 (48%) experienced any grade select GI AEs, and of 357 pts treated with IPI, 132 (37%) experienced any grade select GI AEs. Grade 3/4 select GI AEs were reported in 67 (16%) pts treated with NIVO+IPI and in 41 (11%) pts treated with IPI; median time to onset was 7.1 weeks (range 0.9-48.9) with NIVO+IPI and 7.3 weeks (range 0.6-14.9) with IPI. To manage these AEs, immune-modulating medications (IMM) were used in 61/67 (91%) pts in the NIVO+IPI group and in 41/41 (100%) in the IPI group. Corticosteroids (CS) were used in 61/67 (91%) and 41/41 (100%) pts, and infliximab (IFX) was used in 21/67 (31%) and 14/41 (34%) pts in the NIVO+IPI and IPI groups, respectively. In the NIVO+IPI group, the resolution rate of grade 3/4 select GI AEs was 96%, 97%, and 95% with a median time to resolution of 3.3, 3.0, and 3.9 weeks in all treated pts, CS, and CS+IFX managed pts, respectively; 88%, 92%, and 79% resolved with a median time to resolution of 3.9, 2.4, and 7.8 weeks in the IPI group, respectively. Objective response rates (ORR) were unchanged in the presence of any grade select GI AEs, or by using CS or CS+IFX (Table). Conclusions: NIVO+IPI or IPI alone is associated with a high incidence of GI select AEs, but most are effectively managed by IMMs, which do not appear to inhibit tumor response. Clinical trial information: NCT01844505; NCT01927419