CS1-CAR T Therapy Following Chemotherapy in Treating Patients With Relapsed or Refractory CS1 Positive Multiple Myeloma

This trial is testing a new cell therapy approach for multiple myeloma (a blood cancer of plasma cells) that has come back or stopped responding to treatment — using the patient's own immune T cells that are genetically engineered to find and destroy myeloma cells carrying a protein called CS1. **You may be eligible if...** - You have been diagnosed with active multiple myeloma - Your myeloma tests positive for the CS1 protein - Your myeloma has relapsed or is refractory (stopped responding) after at least 3 prior treatment regimens, including an immunomodulatory drug, a proteasome inhibitor, and an anti-CD38 antibody - You are generally in acceptable health (Karnofsky performance status at least 70%) - Your life expectancy is at least 16 weeks **You may NOT be eligible if...** - Your myeloma does not express the CS1 protein - You have not received the required prior treatments - You have had a prior autologous stem cell transplant within 90 days before enrollment - You have serious liver, heart, or kidney problems - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.