Inclusion Criteria:

• Age ≥ 18 years.
• Clinically confirmed diagnosis of Multiple Myeloma (MM) per IMWG diagnostic criteria.
• Patients who have relapsed after or are refractory to at least 1 prior line of therapy. Patients must have progressed or been refractory to last line of treatment.
• Patients must meet one or more of the following IMWG clinical relapse criteria as direct indicator of progressive disease and/or end-organ dysfunction:
  • Definitive increase in the size of existing plasmacytomas or bone lesions;
  • Hypercalcemia (>11 mg/dL);
  • Decrease in hemoglobin of >2 g/dL not related to therapy or other non-myeloma related conditions;
  • Rise in serum creatinine by 2 mg/dL or more from the start of the therapy and attributable to myeloma;
  • Hyperviscosity related to serum protein.
• Increase of 25% from the lowest confirmed response value in one or more of the following criteria:
  • serum M-protein (increase must be at least 0.5 g/dL);
  • urine M-protein (increase must be at least 200 mg/24 hours);
  • the difference between involved and uninvolved free light chain levels (increase must be >10 mg/dL).
• Patients who have started treatment with daratumumab monotherapy or daratumumab combination regimens as second line treatment or beyond within the 1 month prior to enrollment. Daratumumab use will according to the locally approved label.
• Patients who have received prior autologous stem cell transplant and are beyond day +100 are allowed to participate.
• Prior radiation therapy to symptomatic lesions is allowed provided 10 days have elapsed between the completion of radiation therapy and enrollment.
• Prior systemic glucocorticoid use for the treatment of non-malignant disorders is permitted. Prior or concurrent topical or localized glucocorticoid therapy to treat non-malignant comorbid disorders is permitted.
• ECOG performance status 0, 1, or 2 (PS 3 allowed if secondary to pain).
• Patients with history of prior daratumumab or another anti-CD38 monoclonal antibody treatment who were not refractory or intolerant to such therapy will be able to participate in this study.

Exclusion Criteria: 

• Patients with monoclonal gammopathy of undetermined significance or asymptomatic multiple myeloma.
• Patients with a history of another active malignancy requiring treatment.
• Patients with prior history of malignancy treated with curative intent and not requiring active therapy are allowed to participate. Patients treated for basal cell, squamous cell carcinoma of the skin, or carcinoma in situ of the cervix or of the breast are not excluded.
• Patients actively receiving other investigational agents throughout the duration of this study are excluded.
• Treatment by localized radiotherapy is not an exclusion criterion.