Subcutaneous Daratumumab, Once Weekly Carfilzomib, and Dexamethasone (DKd) in Patients With High-Risk Smoldering Multiple Myeloma

Background: Multiple myeloma (MM) is a tumor in which malignant plasma cells accumulate in the bone marrow. It can cause organ damage and is not curable. Researchers want to see if a combination drug treatment can help. Objective: To try to prevent or slow down developing MM and its associated organ damage by treating it while still in the smoldering phase with a mix of drugs known as DKd. Eligibility: People ages 18 and older with smoldering MM that is at high risk of converting to symptomatic MM. Design: Participants will be screened with: Medical history Physical exam Blood and urine tests Bone survey (x-rays of their bones) Spinal magnetic resonance imaging Bone marrow biopsy (a needle is used to remove bone marrow from their hipbone) Electrocardiogram (to check heart function) Lung function tests Treatment will be given in 28-day cycles. Participants will get daratumumab by injection under the skin. They will get carfilzomib intravenously (IV) through a tube inserted in a vein. They will get dexamethasone as oral tablets or as an IV. They will get all 3 drugs for 8 or 12 cycles. Then they will get daratumumab alone for up to 24 cycles. They may have stem cells collected. Participants will have frequent study visits. At these visits, they will repeat some screening tests. They will complete questionnaires. They will have imaging scans. For these scans, they may receive an oral or IV contrast. Participants will have a follow-up visit 30 days after treatment ends. Then they will have visits every 3-12 months. They will be followed on this study for life.