Infectious Complications and Antimicrobial Resistance Across Cancer Immunotherapies

A narrative review synthesizing clinical trials, observational studies, and guidance through October 2026 evaluated infectious complications, antimicrobial resistance (AMR), and multidrug-resistant (MDR) colonization across cancer immunotherapies, including chimeric antigen receptor (CAR) T-cell therapies, bispecific antibodies (BsAbs), and immune checkpoint inhibitors (ICIs). Infection risk varies based on treatment platform, target antigen, lymphodepletion regimens, immune reconstitution kinetics, concomitant immunosuppression, and supportive care. Severe infectious complications are frequent with BCMA-directed BsAbs, with grade 3–4 infections documented in 39.8% of elranatamab recipients in the MagnetisMM-3 trial and 55.3% of patients in a pooled global teclistamab cohort, estimates that were study-specific and partly influenced by COVID-19. Direct evidence of AMR is concentrated in CAR-T and broader cellular-therapy populations, whereas data for BsAbs and ICIs remain limited. Although associations between broad-spectrum antibiotic exposure, microbiome disruption, and CAR-T clinical outcomes are clinically important, they remain vulnerable to confounding. The authors note that infection prevention and stewardship must rely on individualized parameters—such as patient immune status, previous microbiology, prior antimicrobial exposure, and institutional resistance patterns—rather than assuming risk based on the immunotherapy platform alone.