This study is an open, multicenter, dose-escalation and expanded-enrollment, nonrandomized phase I clinical study to evaluate the safety, tolerability, pharmacokinetic characteristics and preliminary efficacy of BL-M09D1 for injection in patients with locally advanced or metastatic gastrointestinal tumors and other solid tumors.

Inclusion Criteria:

1. Voluntarily sign the informed consent and follow the requirements of the protocol;
2. No gender limit;
3. Age: ≥18 years old and ≤75 years old (phase Ia); ≥18 years old (phase Ib);
4. Expected survival time ≥3 months;
5. Pathologically and/or cytologically confirmed locally advanced or metastatic gastrointestinal tumors and other solid tumors that failed standard treatment;
6. Consent to provide archival tumor tissue samples or fresh tissue samples from primary or metastatic lesions within 2 years;
7. Must have at least one measurable lesion according to RECIST v1.1 definition;
8. ECOG 0 or 1;
9. Toxicity of previous antineoplastic therapy has returned to ≤ grade 1 defined by NCI-CTCAE v5.0;
10. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%;
11. Organ function level must meet the requirements;
12. Coagulation function: international normalized ratio (INR) ≤1.5, and activated partial thromboplastin time (APTT) ≤1.5ULN;
13. Urine protein ≤2+ or ≤1000mg/24h;
14. For premenopausal women with childbearing potential, a pregnancy test must be performed within 7 days before the initiation of treatment, serum pregnancy must be negative, and must be non-lactating; All enrolled patients (regardless of male or female) should use adequate barrier contraception during the whole treatment cycle and for 6 months after the end of treatment;
15. Participants were able and willing to comply with protocol-specified visits, treatment plans, laboratory tests, and other study-related procedures.

Exclusion Criteria:

1. Anti-tumor therapy such as chemotherapy or biological therapy has been used 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. Other malignant tumors diagnosed within 5 years before the first dose;
6. Unstable thrombotic events requiring therapeutic intervention within 6 months before the first dose;
7. Poorly controlled hypertension;
8. Patients with poor glycemic control;
9. History of ILD requiring steroid therapy, or current ILD or ≥ grade 2 radiation pneumonitis;
10. Complicated pulmonary diseases leading to clinically severe respiratory function impairment;
11. Symptoms of active central nervous system metastasis;
12. Patients with a history of allergy to recombinant humanized antibody or human-mouse chimeric antibody or to any of the ingredients of BL-M09D1;
13. Prior organ transplantation or allogeneic hematopoietic stem cell transplantation (Allo-HSCT);
14. Anthracycline cumulative dose > 360 mg/m2 in previous (new) adjuvant therapy;
15. HIV antibody positive, active tuberculosis, active hepatitis B virus infection, or active hepatitis C virus infection;
16. Active infection requiring systemic therapy within 4 weeks before the first dose of study drug; Signs of pulmonary infection or active pulmonary inflammation within 2 weeks before the first dose;
17. Pleural, abdominal, pelvic or pericardial effusion requiring drainage and/or with symptoms within 4 weeks before the first dose of study drug;
18. Use of another clinical trial within 4 weeks or 5 half-lives before the first dose;
19. Pregnant or lactating women;
20. Other conditions for participation in the trial were not considered appropriate by the investigator.