Infliximab or Vedolizumab in Treating Immune Checkpoint Inhibitor-Related Colitis in Patients With Genitourinary Cancer or Melanoma

PRIMARY OBJECTIVES: I. To compare the efficacy of infliximab and vedolizumab for clinical remission/response of immune-related diarrhea and/or colitis. II. To assess the safety and tolerability of the treatment for immune-mediated diarrhea and/or colitis. SECONDARY OBJECTIVES: I. To assess the efficacy of infliximab and vedolizumab for clinical remission/response of IMC at 4 weeks. II. To assess the success of corticosteroid tapering. III. To measure the recurrence rate after corticosteroid taper. EXPLORATORY OBJECTIVES: I. To assess the efficacy of infliximab and vedolizumab to achieve endoscopic remission of immune-related diarrhea and/or colitis. II. To assess the efficacy of infliximab and vedolizumab to achieve histological remission of immune-related diarrhea and/or colitis. III. To assess the time duration to achieve the clinical remission/response. IV. To assess the long term outcome of cancer. V. To assess immunological, molecular and microbiome changes in tissue/blood/stool. OUTLINE: Patients are randomized to 1 of 2 arms. ARM I: Patients receive infliximab intravenously (IV) over 1 hour once at week 0, 2, 6 for a total of 3 doses in the absence of disease progression or unacceptable toxicity. ARM II: Patients receive vedolizumab IV over 1 hour once at week 0, 2, 6 for a total of 3 doses in the absence of disease progression or unacceptable toxicity. Patients are followed up weekly for 1 month and then at 2 and 3 months after the treatment.