Restrictive Versus Standard Antibiotic Treatment During CAR-T Therapy

The purpose of the CARMic study is to investigate whether a restrictive, microbiome-sparing antibiotic strategy can better preserve the gut microbiota in patients undergoing chimeric antigen receptor T-cell (CAR-T) therapy without compromising infectious safety. This is a randomized, open-label Phase II trial enrolling 150 adults with large B-cell lymphoma or multiple myeloma who are scheduled to receive standard-of-care CAR-T therapy. Participants will be randomly assigned in a 1:1 ratio to either a restrictive antibiotic strategy based on ceftazidime and/or ciprofloxacin or an unrestricted standard-of-care antibiotic strategy. The assigned strategy will apply from randomization until 28 days after CAR-T-cell infusion. Antibiotic treatment may be modified or broadened at any time when clinically indicated. The primary question is whether the restrictive antibiotic strategy results in greater gut microbial diversity 28 days after CAR-T-cell infusion compared with standard-of-care antibiotic treatment. Gut microbial diversity will be assessed in stool samples using the Shannon diversity index. The study will also compare infections, antibiotic exposure, adherence to the assigned strategy, CAR-T-related toxicities, treatment response, relapse, progression-free survival, and overall survival between the two groups. Changes in gut microbiota composition and in blood and stool metabolomic and proteomic profiles will be evaluated over time. Blood and stool samples will be collected at randomization, around the time of CAR-T-cell infusion, 28 days after infusion, and at the end-of-treatment evaluation approximately 3-6 months after infusion.