Phase II Study of Post-Transplant Low-Dose Inotuzumab Ozogamicin to Prevent Relapse of Acute Lymphoblastic Leukemia

Inclusion Criteria: * Diagnosis of CD22-positive Acute Lymphoblastic Leukemia * Patients who underwent an allogeneic hematopoietic stem cell transplantation(HSCT) from any donor source or auto-HSCT for acute lymphocytic leukemia * Patients who are after T+60 after transplantation * Patients who have/are either: * High risk B-ALL: (1) high white blood cell(WBC) count when newly diagnosed, (2) Poor risk group according to NCCN guideline 2021 of Acute Lymphoblastic * Leukemia * Relapsed or refractory to at least 1 line of treatment * Minimal residual disease(MRD) positive before HSCT, including flow cytometry and cytogenetic test * Patients who have \> 99% donor chimerism after allogeneic transplantation. * Eastern Cooperative Oncology Group(ECOG) Performance status ≤ 2 * Participants must have ANC \> 1,000/µL for 3 days and platelet transfusion independence as defined as a platelet count \> 50,000/µL for 7 days. * ≥ 18 years old, including male and female * Participants must have the ability to understand and the willingness to sign a written informed consent document. Exclusion Criteria: * Patients with evidence of disease progression prior to enrollment * Persistent prior treatment toxicities Grade 2 and above according to NCI CTCAE Version 4.03 (with the exception for alopecia, neuropathy, etc.) * Patients with inadequate organ function and can't tolerate the study treatment determined by investigator as defined by: * Severe renal deficiency, with creatinine clearance \< 50ml/min * Severe hepatic deficiency * Bilirubin, aspartate aminotransferase(AST), and/or ALT(ALT) \> 2X institutional upper limit of normal * Severe cardiac or pulmonary deficiency * Graft-versus-host disease(GVHD) grade III or IV (for patients with a prior allogeneic transplant). * Active acute or chronic GVHD of the liver (for patients with a prior allogeneic transplant) * History of veno-occlusive disease(VOD) * Second active malignancy, other than non-melanoma skin cancer or carcinoma in situ (e.g. cervix, bladder, breast) * Patients with uncontrolled inter-current illness including, but not limited to ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements. * Serologic status reflecting active hepatitis B or C infection. Patients that are positive for hepatitis B core antibody, hepatitis B surface antigen (HBsAg), or hepatitis C antibody must have a negative polymerase chain reaction (PCR) prior to enrollment. (PCR positive patients will be excluded.) * Any condition that would, in the investigator's judgment, interfere with full participation in the study, including administration of study drug and attending required study visits; pose a significant risk to the participant; or interfere with interpretation of study data. * Known allergies, hypersensitivity, or intolerance to any of the study medications, excipients, or similar compounds