A Study Comparing QLS32015 Monotherapy Versus Pomalidomide, Dexamethasone (Pd) or Selinexor, Dexamethasone (Sd) in Participants With Relapsed or Refractory Multiple Myeloma

Inclusion Criteria: * Age ≥18 years old, regardless of gender. * Subjects should be willing and able to comply with the study schedule and protocols. * Documented initial diagnosis of multiple myeloma according to International Myeloma Working Group (IMWG) diagnostic criteria.Must have measurable disease as defined by the following: Serum M-protein greater than or equal to 0.5 g/dL; OR Urine M-protein greater than or equal to 200 mg/24 hours; OR Serum free light chain (FLC) assay; involved FLC level greater than or equal to 10 mg/dL provided the serum FLC ratio is abnormal. * Received at least 3 prior lines of therapy, including a proteasome inhibitor (PI), an immunomodulatory drug, and an anti-CD38 monoclonal antibody (mAb). Exclusion Criteria: * Known hypersensitivity to any of the ingredients of this product. * Diagnosis of active plasma cell leukemia or systemic light chain amyloidosis. * Has any active severe mental illness, medical illness, or other symptoms/conditions that may affect treatment, compliance, or the ability to provide informed consent, as determined by the investigator. * Disease is considered refractory to pomalidomide and selinexor.