To Evaluate the Safety of SG2918 in Patients With Relapsed/Refractory Multiple Myeloma

Inclusion Criteria: 1. Age ≥ 18 years and ≤ 80 years. 2. Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2. 3. Life expectancy ≥ 3 months. 4. Documented diagnosis of multiple myeloma. 5. Measurable disease at screening (per IMWG criteria). 6. Relevant laboratory values obtained within 7 days prior to the first dose must meet protocol-specified thresholds. 7. Resolution of adverse events related to prior antineoplastic therapy to Grade ≤ 1 or baseline (CTCAE v6.0). 8. Female participants of childbearing potential and male participants whose partners are of childbearing potential must use at least one acceptable method of contraception during study treatment and for at least 7 months after the last dose. 9. Male participants must refrain from sperm donation from the signing of the Informed Consent Form (ICF) until at least 7 months after the last study dose. Exclusion Criteria: 1. Patients with primary refractory multiple myeloma. 2. Presence of non-bone-related extramedullary soft tissue plasmacytoma at screening. 3. known meningeal or Central Nervous System involvement of multiple myeloma, or high suspicion of unconfirmed meningeal or Central Nervous System involvement. 4. History of peripheral neuropathy of Grade ≥ 2. 5. Active infection requiring systemic therapy within 2 weeks prior to the first dose. 6. Hypertension that was not effectively controlled by standardized antihypertensive treatment within 2 weeks prior to the first dose, as judged by the investigator 7. History of hypertensive crisis or hypertensive encephalopathy. 8. Poorly controlled diabetes mellitus. 9. Severe cardiovascular or cerebrovascular disease within 6 months prior to the first dose. 10. Active hepatitis B or hepatitis C infection. 11. Known history of active tuberculosis or active syphilis. 12. Known hypersensitivity to any component of the investigational product. 13. history of Grade 3-4 allergic reaction or life threatening hypersensitivity to any biological product. 14. Received any of the following therapies or surgeries. 1. Prior treatment with LILRB4 targeted therapy; or severe adverse reaction to prior MMAE containing therapy. 2. Immunotherapy, macromolecular targeted therapy, or other antineoplastic biologic therapy within 28 days prior to the first dose. 3. Cytotoxic chemotherapy or small molecule therapy within 14 days prior to the first dose. 4. Modernized traditional Chinese herbal medicine with approved antineoplastic indications within 7 days prior to the first dose. 15. Requirement for systemic corticosteroids (equivalent to \> 10 mg prednisone per day) or other immunosuppressive agents within 14 days prior to the first dose or during the study. 16. Administration of any live or live attenuated vaccine within 28 days prior to the first dose. 17. Administration of other vaccines (e.g., inactivated COVID-19 vaccine) within 14 days prior to the first dose. 18. Immune related toxicity during prior antineoplastic immunotherapy that resulted in permanent treatment discontinuation. 19. Current or previous idiopathic pulmonary fibrosis or idiopathic pneumonia; 20. Current acute pulmonary disease, interstitial lung disease, or pneumonia. 21. Any other malignancy diagnosed within 5 years prior to the first dose. 22. Documented history of neurological or psychiatric disorder. 23. Any other condition that, in the opinion of the investigator, may render the participant unsuitable for study participation.