A Study of BL-M08D1 in Patients With Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma and Other Solid Tumors

1. Voluntarily sign the informed consent form and agree to comply with the requirements of the protocol;
2. No gender restriction;
3. Age: ≥18 years and ≤75 years;
4. Expected survival time ≥3 months;
5. Diagnosed with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) and other solid tumors;
6. Agree to provide archived tumor tissue specimens or fresh tissue samples from the primary or metastatic lesions obtained within 3 years;
7. Must have at least one measurable lesion as defined by RECIST v1.1;
8. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, with no deterioration within 2 weeks prior to the first dose;
9. Toxicities from prior anti-tumor therapy have recovered to ≤ Grade 1 as defined by NCI-CTCAE v6.0;
10. No severe cardiac dysfunction; left ventricular ejection fraction (LVEF) ≥50%;
11. Organ function levels must meet the protocol-specified requirements;
12. Coagulation function: international normalized ratio (INR) ≤1.5, and activated partial thromboplastin time (aPTT) ≤1.5 × upper limit of normal (ULN);
13. Urine protein ≤1+ or ≤1000 mg/24h;
14. For premenopausal women of childbearing potential, a serum pregnancy test must be performed within 7 days prior to the start of treatment, with a negative result, and must be non-lactating; all trial participants (both male and female) must agree to use adequate barrier contraceptive measures throughout the entire treatment period and for 6 months after the completion of treatment;
15. Participants must be capable of and willing to comply with the scheduled visits, treatment plan, laboratory tests, and other study-related procedures as required by the protocol.

Exclusion Criteria:

1. Received chemotherapy, biotherapy, immunotherapy, or other anti-tumor therapies within 4 weeks or 5 half-lives prior to the first dose;
2. History of severe cardiac or cerebrovascular disease;
3. Prolonged QTc interval, complete left bundle branch block, third-degree atrioventricular block, or frequent and uncontrolled arrhythmias;
4. Active autoimmune diseases and inflammatory diseases;
5. Diagnosed with another malignant tumor within 5 years prior to the first dose;
6. Unstable thrombotic events requiring therapeutic intervention within 6 months prior to the first dose;
7. Hypertension poorly controlled by antihypertensive medication;
8. Poorly controlled blood glucose;
9. History of interstitial lung disease (ILD) requiring corticosteroid therapy, or currently diagnosed with ILD, or grade ≥2 radiation pneumonitis;
10. Severe impairment of respiratory function;
11. Active central nervous system (CNS) metastases;
12. Prior or concurrent central nervous system lesions;
13. Participants with a history of allergy to recombinant humanized antibodies or human-mouse chimeric antibodies, or allergy to any excipient component of BL-M08D1;
14. Prior history of organ transplantation or allogeneic hematopoietic stem cell transplantation (Allo-HSCT);
15. Positive for human immunodeficiency virus (HIV) antibody, active tuberculosis, active hepatitis B virus (HBV) infection, or active hepatitis C virus (HCV) infection;
16. Active infections requiring systemic therapy within 4 weeks prior to the first dose of study drug;
17. Pleural, peritoneal, or pericardial effusion requiring drainage and/or accompanied by symptoms within 4 weeks prior to the first dose of study drug;
18. Imaging findings suggest tumor invasion or encasement of abdominal, thoracic, or other major vessels;
19. Received another investigational drug within 4 weeks or 5 half-lives prior to the first dose;
20. Pregnant or breastfeeding women;
21. Other conditions deemed by the investigator to be unsuitable for participation in this clinical trial.