This study is an open, multicenter, increasing dose and dose extension nonrandomized phase I clinical study to evaluate the safety, tolerance, pharmacokinetic characteristics and preliminary effectiveness of BL-B16D1 in recurrent or metastatic head and neck squamous cell carcinomas and other solid tumors.

Inclusion Criteria:

1. Sign the informed consent form voluntarily and follow the protocol requirements;
2. Gender is not limited;
3. Age: ≥18 years old and ≤75 years old (phase Ia); ≥18 years old (phase Ib);
4. Expected survival time ≥3 months;
5. Patients with pathologically and/or cytologically confirmed recurrent or metastatic head and neck squamous cell carcinoma and other solid tumors who failed or could not receive standard treatment;
6. Agreed to provide primary tumors or metastases 3 years archive of tumor tissue samples or fresh tissue samples;
7. Must have at least one accord with RECIST v1.1 define measurable lesions;
8. ECOG physical status 0 or 1;
9. The toxicity of previous antineoplastic therapy has returned to ≤ grade 1 as defined by NCI-CTCAE v5.0;
10. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%;
11. The organ function level must meet the requirements if the patient has not received blood transfusion or hematopoietic stimulating factor therapy within 14 days before screening;
12. Blood coagulation function: international standardization ratio (INR) 1.5 or less, and the part activated clotting time (APTT) live enzymes ULN 1.5 or less;
13. Urinary 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 the patient must not be lactating; All the patients (no matter male or female) shall be 6 months after the end of the treatment period and adequate precautions.

Exclusion Criteria:

1. Antineoplastic therapy within 4 weeks or 5 half-lives before the first dose; Mitomycin and nitrosoureas were administered within 6 weeks before the first dose; Oral drugs such as fluorouracil;
2. History of severe heart disease;
3. QT prolongation, complete left bundle branch block, III degree atrioventricular block;
4. Active autoimmune and inflammatory diseases;
5. Before the first delivery within 5 years diagnosed as other malignant tumor;
6. Hypertension poorly controlled by two antihypertensive drugs (systolic blood pressure > 150 mmHg or diastolic blood pressure > 100 mmHg);
7. Patients with poor glycemic control;
8. Present with grade ≥1 radiation pneumonitis according to the RTOG/EORTC definition; Previous history of ILD or current ILD, or suspicion of such disease during screening;
9. Complicated with pulmonary diseases leading to clinically severe respiratory function impairment;
10. There is activity of the central nervous system symptoms;
11. Patients with a history of allergy to recombinant humanized or human-mouse chimeric antibodies or to any of the excipients of BL-B16D1;
12. Before transplant or allogeneic hematopoietic stem cell transplantation (Allo - HSCT);
13. Previous anthracycline-based adjuvant therapy (new), the cumulative dose anthracycline-based drugs > 360 mg/m2;
14. Human immunodeficiency virus antibody positive, active tuberculosis, active hepatitis B virus infection or active hepatitis C virus infection;
15. Severe infection occurred within 4 weeks before the first dose; Signs of pulmonary infection or active pulmonary inflammation within 2 weeks before the first dose;
16. Patients with massive or symptomatic effusions or poorly controlled effusions;
17. Had participated in another clinical trial within 4 weeks before the first dose (calculated from the time of the last dose);
18. Had the following ocular diseases: a. active infection or corneal ulcer; b. monocular vision; c. a history of corneal transplantation; d. Contact lens dependence; e. Uncontrolled glaucoma; f. Uncontrolled or progressive retinopathy, wet macular degeneration, etc.;
19. Other circumstances that the investigator deemed inappropriate for participation in the trial.