This is an open label phase II study that will enroll patients with relapsed and refractory multiple myeloma after four or more lines of therapy who received idecabtagene vicleucel as standard of care.

The research involves study visits and receiving the study drug. Participants will receive the study drug, elranatamab, for up to 6 months and will be followed for as long as they remain in the study, until confirmed progressive disease (disease worsening), or until initiation of other myeloma treatment.

Elranatamab is a type of antibody (a protein produced by the body's immune system when it detects harmful substances) that works by binding to both T-cells (part of the immune system) and myeloma cells. The drug then activates T-cells to kill the myeloma cells. In this study we are researching whether multiple myeloma progresses after elranatamab administration. The U.S. Food and Drug Administration (FDA) has not approved elranatamab as a treatment for any disease.

It is expected that about 32 people will take part in this research study.