A Study of CT0596 in Relapsed/Refractory Multiple Myeloma and Relapsed/ Refractory Plasma Cell Leukemia

This study is testing a CAR-T cell therapy called CT0596 in patients with relapsed or refractory multiple myeloma (a blood cancer that has come back or stopped responding to treatment) or plasma cell leukemia. CAR-T therapy involves engineering a patient's own immune cells to attack cancer. **You may be eligible if...** - You are 18 or older - You have relapsed or refractory multiple myeloma and have already received at least 3 prior treatment regimens (including a proteasome inhibitor and an immunomodulatory drug), OR you have plasma cell leukemia that has received at least 1 prior treatment - Your disease is measurable and has progressed during or after your most recent treatment - You are in good general health (ECOG 0-1) - You are willing to use contraception for 1 year after treatment and have no plans for sperm/egg donation during that period **You may NOT be eligible if...** - You are pregnant or breastfeeding - You have HIV, active hepatitis B or C, or active tuberculosis - You have uncontrolled infection or significant unresolved side effects from prior treatment - You received an allogeneic (donor) stem cell transplant, or an autologous transplant within the past 12 weeks - You have active autoimmune disease, certain heart conditions, or severe lung problems - You have another active cancer - You have active brain involvement from the disease Talk to your doctor to see if this trial is right for you.