Have moderate or severe cardiovascular disease: Moderate or severe heart valve function defect including moderate or severe valve stenosis or regurgitation. Have moderate or severe cardiovascular disease. Participants with clinically diagnosed moderate to severe cGvHD according to NIH Consensus Criteria prior to randomization: New onset moderate or severe cGVHD as defined by the NIH Consensus Development Project Criteria Moderate or severe ascites Have moderate or severe cardiovascular disease. Have moderate or severe cardiovascular disease. Have moderate or severe cardiovascular disease: Subjects with moderate-severe renal disease Known severe hypersensitivity to trastuzumab (excluding mild to moderate infusion reactions that are easily managed and do not recur) Pulmonary hypertension moderate to severe by echocardiographic standards or more reported moderate-to-very severe hot flashes per week Moderate or severe ascites. Patients with moderate or severe cardiac disease: Moderate or severe ascites Moderate to severe steroid-refractory cGVHD as defined by all following criteria: Moderate or severe cGvHD diagnosed and staged per National Institutes of Health (NIH) criteria Have moderate or severe cardiac disease: Moderate or severe cardiovascular disease Moderate to severe aortic or mitral stenosis or other valvulopathy (ongoing). Subjects with moderate valvular thickening. Have moderate to severe levels of fatigue No evidence of moderate to severe depression as determined by a HADS depression score of =< Patient has severe disabilities limiting moderate physical activity, such as severe orthopedic conditions Within hours of receiving either metronidazole for mild-moderate disease or vancomycin for severe uncomplicated disease Megacolon or moderate to severe ileus Report moderate-severe fatigue in past week (Fatigue Symptom Inventory [FSI] average rating >= of -) Moderate to severe fatigue (>= on BFI) Moderate or severe ascites Moderate or severe acute illness with or without fever Subject has moderate or severe overlap chronic (c)GVHD according to National Institutes of Health (NIH) criteria Previous documented history of moderate to severe hypersensitivity to Gd contrast agents Moderate to severe sun damage Patients with evidence of moderate or severe cardiac valvular disease on echocardiogram Patients with evidence of moderate or severe pulmonary hypertension on echocardiogram Moderate-to-severe pulmonary fibrosis Moderate or severe depression as measured on the Beck Depression Inventory (BDI) - Short Form; the cut-off score for the BDI will be / Moderate or severe aortic stenosis History of moderate or severe reaction to contrast agent injection Have moderate or severe cardiac disease: Known moderate to severe aortic stenosis, moderate to severe mitral stenosis, or other valvulopathy (ongoing).