HP-001 Plus Dexamethasone for Relapsed/Refractory Multiple Myeloma With Extramedullary Disease

Inclusion Criteria 1. Age ≥18 years at the time of signing informed consent; male or female. 2. ECOG performance status of 0-2. 3. Diagnosis of multiple myeloma according to IMWG criteria, with relapsed/refractory disease after at least 1 prior systemic treatment regimen; disease progression or failure to achieve a response after the most recent line of therapy; and extramedullary disease confirmed by imaging, defined as at least 1 soft-tissue extramedullary lesion ≥2 cm, at least 1 paramedullary lesion ≥5 cm, or \>2 lesions. 4. With or without measurable hematologic disease at screening. Measurable disease, if present, is defined as serum M-protein ≥1.0 g/dL, urine M-protein ≥200 mg/24 hours, or serum free light chain ≥10 mg/dL with an abnormal free light chain ratio. 5. Adequate organ function, including ANC ≥1.0 × 10⁹/L, hemoglobin ≥60 g/L, platelet count ≥50 × 10⁹/L, creatinine clearance ≥30 mL/min, total bilirubin ≤2 × ULN (≤3 × ULN for Gilbert syndrome), AST and ALT ≤2.5 × ULN, and INR or aPTT ≤1.5 × ULN. 6. Willing and able to comply with study procedures and follow-up. Exclusion Criteria 1. Smoldering multiple myeloma, monoclonal gammopathy of undetermined significance, Waldenström macroglobulinemia, POEMS syndrome, amyloidosis, or primary/secondary plasma cell leukemia. 2. Central nervous system involvement or clinical evidence of meningeal involvement. 3. Severe or uncontrolled cardiovascular disease, including unstable angina, symptomatic congestive heart failure, myocardial infarction within 6 months before enrollment, severe uncontrolled arrhythmia, or other cardiovascular/cerebrovascular conditions considered unsuitable by the investigator. 4. Major surgery within 4 weeks before the first dose or planned major surgery during the study. 5. Active infection, including HIV infection, active hepatitis B (HBV-DNA positive), active hepatitis C (HCV-RNA positive), active or latent syphilis, active tuberculosis, or other active infections considered unsuitable by the investigator. 6. Concurrent malignancy or other serious concomitant disease that may compromise participant safety or completion of the study. 7. Pregnant or breastfeeding women. 8. History of severe allergy or hypersensitivity to any component of the study treatment. 9. Any other condition that, in the investigator's judgment, makes the participant unsuitable for enrollment.