Hypoxemia and pulmonary infiltrates during T-cell-engaging bispecific antibody therapy: A pulmonary and critical care framework

T-cell-engaging bispecific antibodies (BsAbs) have rapidly expanded treatment options for relapsed or refractory multiple myeloma, B-cell lymphomas, and small-cell lung cancer. Their off-the-shelf availability, step-up dosing, repeated administration, and migration into outpatient and community settings distinguish them from autologous chimeric antigen receptor (CAR) T-cell therapy. These same features increasingly bring patients to pulmonary and critical care teams. Patients receiving BsAbs may present with fever, hypoxemia, pulmonary infiltrates, pneumonia, cytokine release syndrome (CRS), secondary antibody deficiency, Pneumocystis jirovecii pneumonia (PJP), cytomegalovirus (CMV) infection, respiratory viral disease, pulmonary edema, pulmonary embolism, malignant pulmonary involvement, or suspected drug-induced lung injury. Existing guidelines provide essential CRS grading, rechallenge, and infection-prevention recommendations but do not fully address the bedside pulmonary differential diagnosis, indications for bronchoscopy, ventilatory escalation, or intensive care unit (ICU) triage. This focused narrative review synthesizes pivotal trials, current prescribing information, consensus statements, real-world studies, and pulmonary literature. We emphasize two overlapping risk windows: early step-up dosing, in which CRS and infection must be evaluated and treated in parallel, and later or prolonged therapy, in which infection, target-specific immune deficits, and noninfectious mimics become dominant considerations. A timed approach using oxygen trajectory, computed tomography pattern, host immune deficits, microbiologic data, and selective bronchoscopy may reduce diagnostic anchoring and improve multidisciplinary care.