A Study of BL-M24D1 in Patients With Relapsed or Refractory Multiple Myeloma and Other Hematologic Malignancies

Inclusion Criteria: 1. Voluntarily sign the informed consent form and comply with the protocol requirements; 2. Gender is not restricted; 3. Age: ≥18 years and ≤75 years (Phase Ia); ≥18 years (Phase Ib); 4. Expected survival time ≥3 months; 5. Histologically and/or cytologically confirmed multiple myeloma or other hematologic malignancies that have failed standard treatment or for which no standard treatment currently exists; 6. Must have measurable indicators as defined by the protocol; 7. Physical condition score ECOG 0 or 1; 8. Toxicity from previous antitumor treatments has recovered to ≤ Grade 1 as defined by NCI-CTCAE v5.0; 9. No severe cardiac dysfunction, left ventricular ejection fraction ≥50%; 10. Organ function levels must meet the requirements; 11. Coagulation function: International Normalized Ratio (INR) ≤1.5, and activated partial thromboplastin time (APTT) ≤1.5 × ULN; 12. For premenopausal women with childbearing potential, a pregnancy test must be conducted within 7 days before starting treatment, the serum pregnancy test must be negative, and they must not be breastfeeding; all enrolled patients (regardless of gender) should adopt adequate barrier contraception throughout the treatment cycle and for 6 months after the end of treatment. Exclusion Criteria: 1. Subjects with central nervous system involvement, etc.; 2. Use of chemotherapy, biologics, immunotherapy, etc., within 4 weeks prior to the first dose or within 5 half-lives; 3. History of severe heart disease; 4. QT interval prolongation, complete left bundle branch block, third-degree atrioventricular block; 5. Active autoimmune diseases and inflammatory diseases; 6. Diagnosis of other malignancies within 5 years prior to the first dose; 7. Hypertension poorly controlled by two antihypertensive medications; 8. Patients with poorly controlled blood glucose; 9. Unstable thrombotic events requiring therapeutic intervention within 6 months prior to the first dose; 10. Lung diseases defined as ≥ Grade 3 according to CTCAE v5.0; history of interstitial lung disease requiring hormone treatment, etc.; 11. Patients with peripheral neuropathy ≥ Grade 3 or persistent ≥ Grade 2 peripheral neuropathy with pain; 12. Patients with a history of allergy to recombinant humanized antibodies or human-mouse chimeric antibodies, or allergy to any excipient component of BL-M24D1; 13. Previous organ transplantation or allogeneic hematopoietic stem cell transplantation (Allo-HSCT); 14. Human immunodeficiency virus antibody positivity, active tuberculosis, active hepatitis B virus infection, or active hepatitis C virus infection; 15. Active infection requiring systemic treatment within 4 weeks prior to the first study drug administration, etc.; 16. Pleural, abdominal, pelvic, or pericardial effusion requiring drainage and/or accompanied by symptoms within 4 weeks prior to the first study drug administration; 17. Subjects with clinically significant bleeding or obvious bleeding tendency within 4 weeks prior to the first study drug administration; 18. Participation in another clinical trial within 4 weeks prior to the first dose; 19. Pregnant or breastfeeding women; 20. Patients who received live vaccines within 30 days prior to the first dose; 21. Other conditions deemed by the investigator as unsuitable for participation in this clinical trial.