BiRd regimen consisting of clarithromycin and Rd is safe and effective in NDMM. It can significantly increase ORR (up to 90.3%) , relief depth (≥VGPR), and prolong PFS to 43 months. In our previous study, thirty RRMM patients treated with BiRd regimen in 6 centers in China benefited.It suggested that BiRd regimen may not only improve overall efficacy of RRMM , especially long-term benefits, but also reverse Rd resistance in patients who fail to achieve any remission after multiline therapy.The study is a Prospective, Multicenter, Single Arm, Phase II Clinical Trial, which intend to recruit first relapse MM patients over 18 years old. Once included, patients will receive the treatment of Clarithromycin Lenalidomide Dexamethasone (BiRd) Regimen. (Clarithromycin 500mg，po，bid，d1-21; Lenalidomide 25mg，po，daily，d1-21 (dose according to creatinine clearance rate); Dexamethasone 20mg，po，daily，d1-2, 8-9,15-16, 22-23) And we will evaluate efficacy and adverse events of the BiRd regimen at a point of time predetermined.

Inclusion Criteria:

1. diagnosed as symptomatic multiple myeloma.
2. the first relapse/progression with thalidomide, bortezomib or lenalidomide based current first-line treatment or resistance to the first-line treatment (previous treatment line number =1).
3. there must be measurable lesions to determine disease progression (PD): according to the IMWG 2016 efficacy evaluation criteria.
4. the expected survival time is longer than 3 months.
5. ECOG score less than 2 points.
6. the serum AST/ALT level <3 times higher than the normal value; the serum total bilirubin level<2 times of the normal value; creatinine clearance rate was ≥30ml/mi.
7. neutrophil count >1000/mm3 ; platelet count >75000/mm3 (if bone marrow plasma cell <50%) or >30000/mm3 (if the plasma cells in the bone marrow is not less than 50%).
8. women of childbearing age were negative for pregnancy before admission, and agreed to carry out pregnancy screening during the study (once a month until 4 weeks after the last dose), and agreed to use contraceptive measures within 3 months after the study and the last dose.
9. all patients were required to sign informed consent.

Exclusion Criteria:

1. under the age of 18
2. ECOG score >2
3. non secretory myeloma, defined as serum protein M < 1g/dL, urinary M protein < 200mg/24h and sFLCR ≤100mg/L
4. there is growing demand, pregnant or lactating women within one year
5. HIV infection
6. activity of HBV or HCV infection
7. 4 weeks before entering the group of thromboembolic events
8. not signed informed consent