A Study of the Efficacy and Safety of Monotherapy With BCD-264 and Darzalex in Subjects With Relapsed and Refractory Multiple Myeloma

Inclusion Criteria:

1. Signed informed consent form.
2. Age ≥ 18 years at the time of signing of the informed consent form.
3. Documented diagnosis of multiple myeloma according to IMWG criteria
4. Measurable disease at screening:
5. M-protein in serum ≥ 1.0 g/dL (10 g/L) or in 24-hour urine ≥ 200 mg; or
6. light chain myeloma: serum "involved" FLC level ≥ 10 mg/dL (100 mg/L) andabnormal κ/λ FLC ratio .
7. At least a partial response according to IMWG criteria to at least 1 prior line oftherapy.
8. Subjects with relapsed and refractory multiple myeloma who previously received therapywith proteasome inhibitors and immunomodulatory drugs, and who had disease progressionon prior therapy
9. ECOG score 0-2.
10. Not pregnant and willing to use contraception.
11. Consent to bone marrow biopsy in the study.

Exclusion Criteria:

1. Prior treatment with daratumumab or other anti-CD38 therapy.
2. Prior treatment for multiple myeloma within 2 weeks or 5 half-lives before the date ofrandomization, except for a short course of glucocorticoids
3. Autologous hematopoietic stem cell transplantation within 12 weeks prior to the dateof randomization.
4. Allogeneic hematopoietic stem cell transplantation, regardless of timing.
5. Scheduled hematopoietic stem cell transplantation prior to progressive disease duringthis study.
6. Plasma cell leukemia, POEMS syndrome or amyloidosis.
7. Waldenstrom macroglobulinemia or other concomitant diseases with hyperproduction ofmonoclonal IgM (M-protein) in the absence of clonal proliferation of plasma cells withlytic bone involvement.
8. A history of other malignancies within the last 5 years, with the exception ofsquamous cell and basal cell skin cancer, cervical, breast carcinoma in situ, or othernon-invasive malignancies that, in the Investigator's opinion are considered to havebeen adequately treated and have a minimal risk of recurrence for 5 years.
9. Plasmapheresis within 28 days prior to randomization.
10. Clinical signs of meningeal involvement of multiple myeloma.
11. Pregnancy or breastfeeding, as well as planning pregnancy throughout the study andwithin 3 months after the last dose of daratumumab; for male subjects, planning toconceive a child throughout the study and within 3 months after the last dose ofdaratumumab.