This study is an open-label, multicenter, non-randomized Phase I clinical trial to evaluate the safety, tolerability, pharmacokinetic profile, and preliminary efficacy of Lutetium [177Lu] BL-ARC001 in patients with locally advanced or metastatic solid tumors.

The study is divided into two phases: a dose escalation phase (Phase Ia) and a cohort expansion phase (Phase Ib).

Inclusion Criteria:

1. Voluntarily sign the informed consent form and comply with the protocol requirements;
2. Gender: no restriction;
3. Age: ≥18 years and ≤75 years (Phase Ia); ≥18 years (Phase Ib);
4. Expected survival time ≥3 months;
5. Locally advanced or metastatic solid tumors;
6. Agree to provide archived tumor tissue specimens or fresh tissue samples from primary or metastatic lesions within the past 3 years;
7. Must have at least one measurable lesion meeting the RECIST v1.1 criteria;
8. ECOG performance status score of 0 or 1;
9. Toxicities from prior antitumor therapy have recovered to ≤ Grade 1 as defined by NCI-CTCAE v5.0;
10. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%;
11. Organ function levels must meet the requirements;
12. Coagulation function: international normalized ratio ≤1.5, and activated partial thromboplastin time ≤1.5 × ULN;
13. Urine protein ≤2+ or ≤1000mg/24h;
14. For premenopausal women with childbearing potential, a pregnancy test must be performed within 7 days before starting treatment, serum pregnancy must be negative, and must not be breastfeeding; all enrolled patients (regardless of gender) should use adequate barrier contraception throughout the treatment cycle and for 6 months after treatment ends.

Exclusion Criteria:

1. Use of chemotherapy, biotherapy, or immunotherapy within 4 weeks or 5 half-lives (whichever is shorter) prior to the first dose;
2. History of severe heart disease;
3. QT interval prolongation, complete left bundle branch block, or third-degree atrioventricular block;
4. Active autoimmune or inflammatory diseases;
5. Diagnosis of other malignancies within 5 years prior to the first dose;
6. Hypertension poorly controlled by two antihypertensive medications;
7. History of interstitial lung disease (ILD) requiring steroid treatment, current ILD, or ≥ Grade 2 radiation pneumonitis;
8. Symptoms of active central nervous system metastases;
9. History of allergy to recombinant humanized or chimeric antibodies, or allergy to any excipient of Lutetium [177Lu] BL-ARC001;
10. Previous organ transplantation or allogeneic hematopoietic stem cell transplantation;
11. Cumulative dose of anthracyclines > 360 mg/m² in previous (neo)adjuvant anthracycline therapy;
12. Positive human immunodeficiency virus antibody, active tuberculosis, active hepatitis B virus infection, or active hepatitis C virus infection;
13. Active infection requiring systemic treatment;
14. Participation in another clinical trial within 4 weeks prior to the first dose;
15. Pregnant or lactating women;
16. Any other condition deemed by the investigator as unsuitable for participation in this clinical trial.