This study evaluates the dose safety and efficacy of serine in combination with fluoropyrimidine-based therapies. Primary objective: To determine the safety of oral serine administration.
Secondary objectives: 1. To assess the preliminary efficacy of serine in the study population. 2. To establish the recommended Phase 2 dose for oral serine.
Age ≥ 18 years (inclusive), male or female;
Patients with advanced colorectal cancer confirmed by histopathological or cytological examination, eligible for standard first-line treatment with fluorouracil-containing regimens.
Patients must have at least one measurable lesion.
ECOG performance status ≤ 2.
Trial Participation Restrictions: Currently participating in or having received investigational drug/device treatment within the past 4 weeks;
Prior Fluorouracil-Based Therapy Restrictions: History of ≥Grade 3 toxicity (e.g., myelosuppression, gastrointestinal toxicity) following prior fluorouracil-based therapy, deemed unsuitable for re-administration by the investigator;
Recent Surgery Restriction: Undergone major surgery (excluding diagnostic biopsy) within 28 days prior to first dosing, or scheduled for surgery during the study period;
Metabolic and Nutritional Status Restriction: Presence of severe malnutrition (BMI < 18.5 or serum albumin < 30 g/L), or inability to supplement serine orally (e.g., malabsorption syndrome, short bowel syndrome); Known serine metabolism disorders (e.g., PHGDH/PSAT1 gene mutation-related diseases);