Inclusion Criteria:

          1. Adult patients (≥ 18 years old)

          2. Documented MM in relapse according to standard criteria and requiring initiation of a
             first line salvage therapy.

          3. Subject must have received one prior line of therapy for MM.

          4. Subject must have achieved a response (PR or better) to the prior regimen.

          5. Subject must have an ECOG Performance Status score of 0, 1, or 2.

          6. For subjects experiencing toxicities resulting from previous therapy (including
             peripheral neuropathy), the toxicities must have been resolved or stabilized.

          7. Signed informed consent

          8. Affiliation to a social security system or equivalent (recipient or assign)

          9. Effective method of contraception for the duration of treatment and 3 months after the
             last dose for women of childbearing age and men with a partner of childbearing age:

               -  Progestin-only pill associated with inhibition of ovulation

               -  Hormonal methods of contraception, including oral contraceptive pills containing
                  a combination of estrogen + progesterone, vaginal ring, injectables, implants and
                  intrauterine devices (IUDs)

               -  non-hormonal IUD

               -  Bilateral tubal occlusion

               -  Vasectomized partner with documented azoospermia 90 days after procedure and who
                  received a medical assessment of surgical success

               -  Intrauterine hormone release system (IUS)

               -  Complete Abstinence: Complete abstinence is defined as the complete avoidance of
                  heterosexual intercourse. Complete abstinence is an acceptable form of
                  contraception for all study drugs and must be used throughout the duration of the
                  study and for the duration of time as specified above. It is not necessary to use
                  any other method of contraception when complete abstinence is elected. Acceptable
                  alternate methods of highly effective contraception must be discussed in the
                  event that the subject chooses to forego complete abstinence.

        Exclusion Criteria:

          1. Evidence of refractoriness or intolerance to lenalidomide and/or daratumumab (or
             another anti CD38 monoclonal antibody). If previously treated with a lenalidomide or
             daratumumab-containing regimen, the subject is excluded if he or she:

               -  Discontinued due to any severe adverse event related to prior lenalidomide and/or
                  daratumumab (or another anti CD38 monoclonal antibody) treatment, or

               -  If, at any time point, the subject was refractory to any dose of lenalidomide
                  and/or daratumumab (or another anti CD38 monoclonal antibody). Refractoriness to
                  lenalidomide and/or daratumumab (or another anti CD38 monoclonal antibody) is
                  defined either as:

                    -  Subjects whose disease progressed within 60 days of lenalidomide and/or
                       daratumumab (or another anti CD38 monoclonal antibody) administration; or

                    -  Subjects whose disease is nonresponsive while on lenalidomide and/or
                       daratumumab (or another anti CD38 monoclonal antibody). Nonresponsive
                       disease is defined as either failure to achieve at least a minimal response
                       or development of progressive disease while on lenalidomide and/or
                       daratumumab (or another anti CD38 monoclonal antibody).

          2. Subject has received an allogenic stem cell transplant (regardless of timing).

          3. Subjects planning to undergo a stem cell transplant prior to progression of disease on
             this study, ie, these subjects should not be enrolled in order to reduce disease
             burden prior to transplant.

          4. Subject has a history of malignancy (other than MM) within 3 years before the date of
             randomization (exceptions are squamous and basal cell carcinomas of the skin,
             carcinoma in situ of the cervix, or malignancy that in the opinion of the investigator
             is considered cured with minimal risk of recurrence within 3 years).

          5. Subject has known MM meningeal involvement.

          6. Subject has plasma cell leukemia (>2.0 × 109/L circulating plasma cells by standard
             differential) or Waldenström's macroglobulinemia or POEMS syndrome (polyneuropathy,
             organomegaly, endocrinopathy, monoclonal protein, and skin changes) or amyloidosis.

          7. Subject has any concurrent medical condition or disease (eg, active systemic
             infection) that is likely to interfere with study procedures or results, or that, in
             the opinion, of the investigator would constitute a hazard for participating in this
             study.

          8. Subject has known uncontrolled chronic obstructive pulmonary disease (COPD)

          9. Subject has clinically significant cardiac disease.

         10. Subject is known to be seropositive for human immunodeficiency virus (HIV), hepatitis
             B or hepatitis C.

         11. Creatinine clearance ≤30 mL/min (MDRD method) (lenalidomide dose adjustment will be
             considered for subjects with creatinine clearance 30-60 mL/min).

         12. Hypersensitivity to the active substance or to any of the excipients

         13. Pregnancy or lactation women