- Six weeks must have elapsed since any prior antibody therapy including anti-cytotoxic T-lymphocyte antigen 4 (CTLA4) antibody therapy that could affect any anti-cancer immune response, at the time the patient receives the preparative regimen to allow antibody levels to decline. NOTE: patients who have previously received ipilimumab and have documented gastrointestinal (GI) toxicity must have a colonoscopy with normal colonic biopsies.)