For example, prophylactic treatment with the minimally absorbed antibiotic rifaximin is under investigation to assess the reduction of anticancer treatment-associated gastrointestinal toxicity and diarrhea in colon adenocarcinoma (NCT04003181), colorectal cancer (NCT03563586), and stage I-III human epidermal growth factor receptor 2 (HER2)-positive breast cancer (NCT04249622) [97]. Here, ERBB2 is linked to breast cancer.