Description:

This phase I trial tests the safety, side effects, and best dose of actinium Ac 225-DOTA-daratumumab (225Ac-DOTA-daratumumab) in combination with daratumumab and indium In 111-DOTA-daratumumab (111In-DOTA-daratumumab) in treating patients with multiple myeloma that does not respond to treatment (refractory) or that has come back (recurrent). Daratumumab is a monoclonal antibody that may interfere with the ability of cancer cells to grow and spread. 111In-DOTA-daratumumab and 225Ac-DOTA-daratumumab are forms of radioimmunotherapy in which a monoclonal antibody, daratumumab, has been linked to a radiotracer to allow for targeted delivery of the treatment to cancer cells. Giving all three together may kill more cancer cells.