Clinical Trial of Expanded and Activated Autologous NK Cells to Treat Multiple Myeloma

Inclusion Criteria: * Subjects between 20 and 80 years old * With multiple myeloma in 2nd or later relapse or showing resistance after 2 treatment lines * Eastern Cooperative Oncology Group (ECOG) ≤ 2 * Life expectancy greater than six months * Creatinine clearance rate more than 30 ml / min * Subjects who have received at least 4 cycles of rescue treatment under the procedures of the 12 de Octubre Hospital (rescue treatment will vary depending on previous anti-myeloma treatment). After treatment, patients must have shown chemosensitivity and disease stabilization. * Will be included subjects with partial response or stable disease (for at least 2 cycles) after 75% of planned rescue treatment or patients at subclinical progression (defined as an increase of monoclonal component ≥ 25%) at any time of rescue treatment. Subjects have to show tolerance to rescue treatment, without G3/4 adverse effects, if G1/2 adverse effects exist they must be analyzed immediately before starting reinfusion program. * Subjects have to agree to participate in the trial and they have to sign informed consent. Exclusion Criteria: * Subjects with clinical progression or complete response will not be included. * Any of the following abnormal laboratory results: Absolute Neutrophil Count \< 1000/ µL Platelets Count \< 50000/ µL in those patients with bone marrow infiltration lower than 50% Measured creatinine clearance \<30 ml/min Hemoglobin level ≤ 8 g/dL Peripheral neuropathy ≥ Grade 2 * Subjects have received allogeneic stem cell transplant. * Subjects with heart disease which compromises patient's life or protocol accomplishment. * Subjects with past clinical history of malignant disease within 3 years (exceptions are squamous or basal cell carcinoma). * Subjects receiving another investigational drug or having received investigational drug within 30 days before screening. * Subjects who require chronic steroid or immunosuppressive treatment. * Any condition, including abnormally laboratory results, that might compromise the patient´s life if he participate in this study. * Any concurrent medical condition, abnormally laboratory results or any psychological disorder that prevent the patient to sign the informed consent. * Pregnant or fertile women. * Patients known to be seropositive for human immunodeficiency virus (VIH) or having active hepatitis A, B or C.