Bendamustine and Dexamethasone in Patients With Relapsed AL Amyloidosis

Inclusion Criteria: * Male or female patients aged ≥ 18 years old * Histopathology of amyloidosis or light chain deposition disease based on detection by polarizing microscopy of green bi-refringent material in Congo red-stained tissue specimens or characteristic electron microscopy appearance or immunohistochemical stain with anti-light chain anti-sera * Demonstrate measurable disease as defined by one or more of the following: * Serum monoclonal protein ≥ 0.5 g/dL by serum electrophoresis * Urine monoclonal protein \> 200 mg/dL in a 24 hr urine electrophoresis * Serum immunoglobulin free light chain ≥ 5 mg/dL and abnormal serum immunoglobulin kappa lambda free light chain ratio. The difference between involved and uninvolved free light chains should be ≥ 5 mg/dL (dFLC) * Demonstrate clonal population of plasma cells in the bone marrow or immunohistochemical stain with anti-light chain anti-sera of amyloid fibrils * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 * Patients had at least one prior regimen consisting of at least 1 cycle * If not previously transplanted, patient should be either ineligible for autologous stem cell transplantation (ASCT), or must have declined the option of ASCT. Patients who have previously had ASCT and have subsequently progressed are eligible, provided other entry criteria are met * Ability to provide written informed consent obtained prior to participation in the study and any related procedures being performed Patients must meet the following laboratory criteria: * Absolute neutrophil count (ANC) ≥ 1.5 x 10\^9/L * Hemoglobin ≥ 9 g/dl (May transfuse packed red blood cells (PRBC) to meet parameter) * Platelets ≥ 100x 10\^9/L (Must be independent of platelet transfusion) * Calculated creatinine clearance (CrCl) greater than or equal to 30 mL/min (Cockcroft-Gault Formula ) * Aspartate transaminase (AST) and alanine transaminase (ALT) ≤ 2.5 x upper limit of normal (ULN) * Serum bilirubin \<1.5 x ULN * Serum potassium within normal limits * Total serum calcium (corrected for serum albumin) or ionized calcium ≤ ULN Exclusion Criteria: * Patients meeting the criteria for symptomatic MM: * Lytic lesions on skeletal survey or plasmacytoma Patients meeting International Myeloma Working Group definition of symptomatic myeloma with symptoms only related to associated amyloidosis who would otherwise only meet the criteria for smoldering MM are potentially eligible * Myocardial infarction within 6 months prior to enrollment or has New York Heart Association (NYHA) Class III or IV heart failure uncontrolled angina, severe uncontrolled ventricular arrhythmias, or * electrocardiographic evidence of acute ischemia or active conduction system abnormalities (not including 1st degree atrioventricular (AV)-block, Wenckebach type 2nd degree heart block, or left bundle branch block. Prior to study entry, any electrocardiogram (ECG) abnormality at Screening has to be documented by the investigator or an authorized physician sub-investigator as not medically relevant). Note: There is no lower limit of left ventricular ejection fraction below which patients are excluded from participation. * Patients with N-terminal (NT)-proBNP ≥ 1800nb/L or B-type natriuretic peptide (BNP) ≥ 400 ng/L, abnormal cardiac troponin T (cTnT) or cardiac troponin l (cTnI) * Patient has received other investigational drugs within 14 days prior to enrollment * Any form of secondary / familial amyloidosis * Serious concurrent illness, which in the opinion of the investigator or an authorized physician sub-investigator would interfere with participation in this clinical study, * Known HIV infection. * Inability to provide informed consent or to comply with the schedule of office and treatment visits * Female subject is pregnant or breast-feeding. Confirmation that the subject is not pregnant must be established by a negative serum beta-human chorionic gonadotropin pregnancy test result obtained during screening. Pregnancy testing is not required for post-menopausal or surgically sterilized women(woman not of child-bearing potential is defined as any woman whose menstrual periods have stopped in the past 12 consecutive months or have had a complete hysterectomy or both ovaries surgically removed). * Diagnosed or treated for another malignancy within 3 years of enrollment, with the exception of complete resection of basal cell carcinoma or squamous cell carcinoma of the skin, an in situ malignancy, low-risk prostate cancer, or cancer after curative treatment.