Dose Schedule Study of BCMA Bispecific Antibody, Elranatamab, for Newly Diagnosed Immunoglobulin Light Chain (AL) Amyloidosis

Inclusion Criteria: * Newly diagnosed Immunoglobulin Light Chain (AL) amyloidosis who have not received any prior therapy. * Participants must have a tissue biopsy demonstrating Congo red positivity with characteristic birefringence on polarized microscopy and immunohistochemistry or mass spectrometry confirming light chain type. * Participants must not have any evidence of myeloma defining events based on the International Myeloma Working Group (IMWG) myeloma diagnostic criteria (SLIM-CRAB). This excludes the light chain ratio criteria of involved versus uninvolved free light chains (FLC) over 100 in the absence of CRAB criteria. * Age ≥ 18 years * Eastern Cooperative Oncology Group (ECOG) performance status ≤2 * Participants must meet the following organ and marrow function as defined below: Absolute neutrophil count ≥1,000/mcL, Absolute platelet count ≥50,000/mcL, Direct bilirubin ≤1.5 × institutional upper limit of normal (ULN) AST(SGOT)/ALT(SGPT) ≤3 × institutional ULN. * Participants must have a clonal plasma cell burden of less than 40%. * For participants with evidence of chronic hepatitis B virus (HBV) infection, the HBV viral load must be undetectable on suppressive therapy, if indicated. * Participants with a history of hepatitis C virus (HCV) infection must have been treated and cured. For participants with HCV infection who are currently on treatment, they are eligible if they have an undetectable HCV viral load. * AL Amyloidosis Cardiac stage I, II or IIIa disease based on the 2015 European Modification of the 2004 Standard Mayo Clinic Staging in participants with advanced cardiac involvement (Dispenzieri et al., 2004; Wechalekar et al., 2013) (NT-proBNP \<8500 ng/L and troponin criteria per staging system). * The effects of Elranatamab on the developing human fetus are unknown. Based on the mechanism of action, Elranatamab may cause fetal harm when administered to a pregnant woman and therefore should not be used during pregnancy. For this reason, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation and until 90 days since the last dose of Elranatamab. Should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately. Men treated or enrolled on this protocol must also agree to use adequate contraception prior to the study, for the duration of study participation, and 90 days after completion of Elranatamab administration. * Ability to understand and the willingness to sign a written informed consent document. * Willingness to undergo study procedures, including bone marrow biopsies as detailed in the schedule of events. Exclusion Criteria: * Participants who are receiving any other investigational agents for this condition. * Participants with Stage IIIB Amyloidosis as defined by the Europeans Revised 2004 Mayo Clinic Criteria. * Participants with an active malignancy (including lymphoma) with the following exceptions: adequately treated basal cell carcinoma, squamous cell carcinoma, or in situ cervical cancer; adequately treated stage I cancer from which the participant is currently in remission and has been for over 2 years; low-risk prostate cancer with a Gleason score \< 7 and prostate specific antigen \< 10ng/mL; other localized, indolent and/or low risk cancer may be permitted. * Women who are pregnant, breastfeeding, or planning to become pregnant while enrolled in this study or 4 months following discontinuation of Elranatamab, whichever is longer. Pregnant women are excluded from this study because Elranatamab is an agent with the potential for teratogenic or abortifacient effects. Because there is an unknown but potential risk for adverse events in nursing infants secondary to treatment of the mother with Elranatamab, breastfeeding should be discontinued if the mother is treated with Elranatamab. * Have any other medical, social or psychological factors that could affect the participant's safety or ability to consent personally or comply with study procedures. * Participants with active clinically significant autoimmune diseases. * Participants seropositive for the human immunodeficiency virus (HIV). * Severe, uncontrolled orthostatic hypotension resulting in syncopal/pre-syncopal events despite optimized medical management (e.g., midodrine, pyridostigmine) and in the absence of volume depletion. * Plan for autologous stem cell transplant or solid organ transplant during the first 6 months of protocol therapy. * History of acute coronary syndrome or uncontrolled ventricular arrhythmias within 3 months prior to screening. * Evidence of Left Ventricular (LV) systolic dysfunction as defined by Left Ventricular Ejection Fraction (LVEF) is \< 30% by echocardiogram at Screening per site cardiology interpretation. * Have history of sustained ventricular tachycardia or aborted ventricular fibrillation or a history of atrioventricular nodal or sinoatrial nodal dysfunction if a permanent pacemaker (PPM) or implantable cardioverter-defibrillator (ICD) is not placed. * QT corrected by Fridericia (QTcF) is \> 550 msec on Screening ECG unless they have a PPM/ICD implanted. * Screening EKG showing acute myocardial ischemia or active conduction system abnormalities with the exception of any of the following: First degree atrioventricular block; Second degree atrioventricular block Type 1 (Mobitz Type 1/Wenckebach type); Right or left bundle branch block (e.g., Left Bundle Branch Block, Right Bundle Branch Block, Left Anterior Fascicular Block, or Left Posterior Fascicular Block); Atrial fibrillation with a controlled ventricular rate; Bifascicular block assessed as benign by the Investigator * Major surgery that required general anesthesia within 4 weeks of randomization or is planning major surgery during the study. * NYHA class IV symptoms * Participants with a Glomerular Filtration Rate (GFR) \<20, unless stable on dialysis for at least 3 months