Pilot Trial of Fecal Microbiota Transplantation for Lymphoma Patients Receiving Axicabtagene Ciloleucel Therapy.

This trial is testing whether a fecal microbiota transplant (FMT) — transferring healthy gut bacteria from a donor — can restore a patient's gut microbiome after antibiotic treatment and improve outcomes for lymphoma patients receiving a specific CAR-T cell therapy called axicabtagene ciloleucel (axi-cel). Disruption of gut bacteria by antibiotics may reduce CAR-T effectiveness. **You may be eligible if...** - You are 18 or older with a confirmed B-cell lymphoma - You are scheduled to receive the axi-cel CAR-T therapy as standard care - You have received broad-spectrum antibiotics for at least 2 days in the past 6 months before your CAR-T infusion - Your blood counts and organ function meet study minimums **You may NOT be eligible if...** - You have severe immune system suppression or active graft-versus-host disease - You have active, uncontrolled infection - You received a live vaccine within the past 30 days - You received a stem cell transplant recently (within 3–6 months) - You have serious bowel disease that would make an FMT unsafe Talk to your doctor to see if this trial is right for you.