SG-2918

Phase Ib Study: 1. Primary Objectives: 1) Safety and tolerability; 2. Secondary Objectives: 1) To evaluate the PK and PD characteristics of SG2918 in patients with relapsed/refractory multiple myeloma; 2) To evaluate the immunogenicity of SG2918; 3) To evaluate the preliminary antitumor efficacy of SG2918 in the treatment of patients with relapsed/refractory multiple myeloma. Phase II Study: 1. Primary Objectives: 1) Safety and tolerability; 2) To determine the RP2D of SG2918 in patients with relapsed/refractory multiple myeloma; 3) To evaluate the preliminary antitumor activity of SG2918 as monotherapy in patients with relapsed/refractory multiple myeloma. 2. Secondary objectives: 1) To evaluate the efficacy of SG2918 in the treatment of patients with relapsed/refractory multiple myeloma (PFS, MRD negativity rate, etc.); 2) To assess the pharmacokinetic (PK) and PD characteristics of SG2918 in patients with relapsed/refractory multiple myeloma; 3) To assess the immunogenicity of SG2918.