Inactivated Bacteroides Fragilis for Prevention of Chemotherapy-Induced Diarrhea

Inclusion criteria

• Voluntarily sign the informed consent form, be able to comply with the protocol and have the capacity to complete relevant procedures.
• Aged ≥ 18 years old (based on the date of signing the ICF), regardless of gender.
• Patients with malignant tumors confirmed by pathology or cytology.
• Patients scheduled to receive the following initial treatments at the standard dose specified in the protocol:

• Cohort 1: Patients with advanced colorectal cancer receiving the FOLFIRI regimen (irinotecan + fluorouracil + leucovorin);
• Cohort 2: Patients with breast cancer receiving neratinib treatment.
• ECOG performance status score of 0-1 at the start of the study.
• Expected survival time ≥ 12 weeks.
• Subjects of childbearing potential (including males and females) agree to adopt effective contraceptive measures approved by the investigators (e.g., intrauterine device, contraceptive pills or condoms) during the trial and within 3 months after the trial ends. Female subjects of childbearing potential must have a negative result in serum human chorionic gonadotropin (hCG) test.

Exclusion criteria

• History of altered bowel habits or abnormal stool characteristics prior to screening that, in the investigator's opinion, would preclude subsequent efficacy evaluation; or use of laxatives within 7 days prior to randomization; or use of antidiarrheal agents within 48 hours prior to randomization.
• Complicated with diseases causing diarrhea, including but not limited to inflammatory bowel disease (e.g., ulcerative colitis and Crohn's disease), suspected or confirmed infectious diarrhea, irritable bowel syndrome, celiac disease, etc.
• Receipt of any chemotherapeutic agents or PD-1 antibodies other than the chemotherapy/treatment regimen specified in the protocol during the trial.
• Concurrent abdominopelvic radiotherapy during the trial period; or unresolved radiotherapy-induced enteritis caused by previous abdominopelvic radiotherapy.
• Medical history of chronic use of laxatives (≥ 30 non-consecutive days).
• Need for antibiotic treatment during the trial or long-term use of antibiotics prior to randomization.
• Patients with stomas, including temporary stomas that have not been closed or patients whose bowel function has not recovered after stoma closure.
• Presence of unhealed surgical wounds, ulcers or fractures.
• Known history of human immunodeficiency virus (HIV) infection (positive HIV antibody test).
• History of allergy or suspected allergy to antidiarrheal drugs (e.g., loperamide and its components).
• Suspected or confirmed history of alcohol or drug abuse.
• Pregnant or lactating women.
• Concurrent participation in other clinical trials.
• Other conditions deemed inappropriate for study participation by the investigator.