Carfilzomib, Oral Cyclophosphamide, and Dexamethasone for RRMM (KMM-KCd)

Inclusion Criteria: Subjects aged 19 years or older ECOG performance status 0 to 2 Diagnosed with multiple myeloma by IMWG criteria Subjects previously treated with 1 or more lines of therapy Subjects previously treated with lenalidomide-based combination or sigle drug therapy Subjects with relapsed and/or refractory multiple myeloma Subjects with measurable disease at the time of treatment initiation serum M protein >=0.5 g/dL, or 24h urine M protein >= 200mg/24h serum free light chain difference >=10mg/dL and abnormal FLC ratio Adequate organ function absolute neutrophil count >= 1.0 x 109/L platelelt count >= 50 x 109/L (plasmacytoma in the bone: >=30 x 109/L) Hb >=8g/dL serum creatinine < 3.0mg/dL or CCR >=15mL/min serum AST and ALT <=3 x ULN serum total bilirubin <= 3 x ULN Subjects able to swallow oral drugs Subjects who had experienced toxicities to previous therapies: resolved from previous toxicities or stabilized of the toxicity to grade 1 Subjects who had received allogenetic stem cell transplantation: no acitve graft-versus-host disease Subjects without clinically relevant bleeding Subjects who have informed consent to the study Females of childbearing potential (FCBP) must be negative to pregnancy testing and give consent to practice contraception before and during the treatment Exclusion Criteria: 1. Subjects who were previously exposed to carfilzomib 1. Subjects who were previously exposed to cyclophosphamide 3. Subjects diagnosed with POEMS SD, Waldenstrom macroglobulinemia, Plasma cell leukemia 4. Subjects with concurrent heart conditions Myocardial infarction within 6 months prior to treatment, New York Heart Association class III or IV heart failure, uncontrolled angina, history of severe coronary artery disease, Uncontrolled arrythmias (CVDAE version4 grade 2 or more) or symptomatic EKG abnormalities 12-lead EKG : baseline ATcF > 470msec 2D Echocardiography or MUGA scan : systolic EF < 40% with clinically significant symptoms Uncontrolled hypertension ( with medication: systolic BP >= 160 mmHg or diastolic BP >= 100 mmHg) 5. Chronc obstructive pulmonary disease (FEV1 < 60%), history of asthma within 2 years 6. Surgery under general anesthesia withing 2 weeks 7. Subjects diagnosed with malignancies within 5 years (except for cured skin cancer, cervical cancer, intraepithelial gastrointestinal tract cancer after curative procedures or surgery for more than 3 years) 8. Any other clinically significant medical disease or condition that, in the Investigator's opinion, may interfere with protocol adherence or a subject's ability to give informed consent 9. Pregnant or breatfeeding subjecs