Purpose:We assessed the relationship between cluster of differentiation-22 (CD22) expression and outcomes of inotuzumab ozogamicin versus standard of care (SC) in INO-VATE (NCT01564784).Patients and Methods:Adults with relapsed/refractory B-cell precursor CD22-positive (by local or central laboratory) acute lymphoblastic leukemia were randomized to inotuzumab ozogamicin (n = 164) or SC (n = 162). Outcomes were analyzed by baseline CD22 positivity (percentage of leukemic blasts CD22 positive, ≥90% vs. Results:Most patients had high (≥90%) CD22 positivity per central laboratory. The response rate was significantly higher with inotuzumab ozogamicin versus SC. Minimal/measurable residual disease negativity, duration of remission (DoR), progression-free survival, and overall survival (OS) were significantly better with inotuzumab ozogamicin versus SC in patients with CD22 positivity ≥90%. Fewer patients had CD22 positivity Conclusions:Inotuzumab ozogamicin demonstrated a favorable benefit–risk profile versus SC in patients with higher and lower CD22 expression. Patients with high CD22 expression and normal cytogenetics benefited the most from inotuzumab ozogamicin therapy.