This is a first-in-human, multicenter, open-label Phase I/II study evaluating the safety, tolerability, pharmacokinetics, pharmacodynamics, and preliminary antitumor activity of oral Zn-Telomir monotherapy in adults with advanced or metastatic triple-negative breast cancer. Phase I uses a modified 3+3 dose-escalation design to determine safety, tolerability, maximum tolerated dose, and recommended Phase II dose. Phase II uses a Simon two-stage expansion design at the recommended Phase II dose to evaluate preliminary antitumor activity, including objective response rate per Response Evaluation Criteria in Solid Tumors.

Inclusion Criteria:

1. Clinically defined histologically or cytologically confirmed triple-negative breast cancer (TNBC)
2. Locally advanced unresectable or metastatic disease
3. Must have completed prior anticancer therapy discontinued for a least 28 days
4. Disease progression after prior systemic therapy for advanced/metastatic TNBC
5. At least one measurable lesion (tumor)
6. Age ≥18 years
7. Life expectancy ≥12 weeks
8. Agreement to use highly effective contraception during study and for 3 months after treatment
9. Ability to understand and sign informed consent

Exclusion Criteria:

1. HER2-positive or hormone receptor-positive breast cancer
2. Active leptomeningeal disease
3. Uncontrolled, symptomatic CNS metastases
4. Concurrent participation in another interventional clinical trial
5. Clinically significant cardiovascular disease
6. Uncontrolled infection requiring systemic therapy
7. Known Human Immunodeficiency Virus (HIV) with detectable viral load >400 copies/mL
8. Active hepatitis B virus (HBV) infection or active hepatitis C virus (HCV)
9. Significant Gastrointestinal (GI) disorders
10. Active bleeding disorders or coagulopathy
11. Pregnancy or breastfeeding