5-strain Probiotic Formulation in HR-positive Breast Cancer Receiving Aromatase Inhibitor to Prevent Bone Loss

PRIMARY OBJECTIVE: I. To evaluate the median percent change from baseline (prior to the start of an aromatase inhibitor \[AI\]) at 15 months in C-terminal telopeptide of type 1 collagen (CTx) in early-stage breast cancer patients who receive WBF-038 treatment for 12 months starting at 3 months post-baseline. SECONDARY OBJECTIVES: I. To evaluate the median percent change from baseline (prior to the start of an AI) at 15 months in the lumbar spine and hip bone mineral density in early-stage breast cancer patients who receive WBF-038 treatment for 12 months starting at 3 months post-baseline. II. To evaluate safety and risk of fracture associated with WBF-038. EXPLORATORY OBJECTIVES: I. To evaluate changes from baseline (prior to the start of an AI) over time in CTx, alkaline phosphatase (ALK), fasting blood sugar (FBS), hemoglobin A1C (HbA1C), and Procollagen I Intact N-Terminal (P1NP) at 3, 6, 15, and 18 months post-baseline. II. To evaluate changes from baseline (prior to the start of an AI) over time in weight and waist circumference at 3, 6, 15, and 18 months post-baseline. III. To evaluate changes in the cytokine profile over time. IV. To evaluate the association between stool microbiome, stool short-chain fatty acid (SCFA), and serum SCFA and changes over time in CTx and lumbar spine and hip bone mineral density. V. To evaluate changes over time in AI-associated musculoskeletal symptoms (AIMSS) with patient-reported outcomes (PRO) using the Stanford Health Assessment Questionnaire (HAQ) and pain visual analog scale (VAS). OUTLINE: Patients receive WBF-038 orally (PO) once daily (QD) for 365 days in the absence of disease progression or unacceptable toxicity. Patients also undergo blood sample collection and bone mineral density (BMD) test at screening and on study. After completion of study intervention, patients are followed up at 90 days.