Antimicrobial Resistance and Infectious Complications in Cancer Immunotherapy: CAR-T Cells, Bispecific Antibodies and Immune Checkpoint Inhibitors

Cancer immunotherapies, including chimeric antigen receptor (CAR) T-cell therapies, bispecific antibodies (BsAbs), and immune checkpoint inhibitors (ICIs), have improved outcomes across hematologic and solid malignancies. Infection risk remains heterogeneous and depends on treatment platform, target antigen, lymphodepletion, immune reconstitution, concomitant immunosuppression, and supportive care. This narrative review synthesizes clinical trials, observational studies, and guidance identified through PubMed/MEDLINE, reference screening, and a targeted literature update through October 2026. It focuses on infection incidence, microbiological spectrum, antimicrobial resistance (AMR), multidrug-resistant (MDR) colonization and infection, antimicrobial exposure, prevention, and stewardship. Severe infections can be frequent with BCMA-directed BsAbs: the MagnetisMM-3 study reported grade 3–4 infections in 39.8% of elranatamab-treated patients, while a pooled global teclistamab cohort reported grade 3–4 infections in 55.3%; these estimates are study-specific and are influenced in part by COVID-19. Direct AMR evidence is concentrated in CAR-T and broader cellular-therapy cohorts, while comparable data for BsAbs and ICIs remain limited. Associations between broad-spectrum antibiotic exposure, microbiome disruption, and CAR-T outcomes are clinically important but remain vulnerable to confounding. Prevention should integrate immune status, prior microbiology, antimicrobial exposure, and local resistance patterns rather than infer resistance risk from treatment platform alone. Prospective studies using harmonized outcomes are needed to improve individualized infection prevention and antimicrobial stewardship.