NCT06025682 is a multicenter retrospective observational study of adults with relapsed/refractory CD22+ B‑ALL (including Ph+ after ≥1 TKI) previously treated with inotuzumab ozogamicin (INO). Drug/intervention: INO is an antibody–drug conjugate (immunotherapy) comprising a humanized anti‑CD22 monoclonal IgG4 linked to calicheamicin. Mechanism: INO binds CD22 on B‑lineage blasts, is internalized, and releases calicheamicin, which induces DNA double‑strand breaks leading to apoptosis. Targets: CD22-expressing B‑cell precursors/blasts, cytotoxic effect via DNA damage pathway. Outcome assessed: incidence of bacterial, fungal, and viral infections post‑INO.