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 cytometryand 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 transfusionindependence 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 awritten 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 CTCAEVersion 4.03 (with the exception for alopecia, neuropathy, etc.)

• Patients with inadequate organ function and can't tolerate the study treatmentdetermined 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 institutionalupper limit of normal

• Severe cardiac or pulmonary deficiency

• Graft-versus-host disease(GVHD) grade III or IV (for patients with a priorallogeneic transplant).

• Active acute or chronic GVHD of the liver (for patients with a prior allogeneictransplant)

• 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 toongoing or active infection, symptomatic congestive heart failure, unstable anginapectoris, cardiac arrhythmia, or psychiatric illness/social situations that wouldlimit compliance with study requirements.

• Serologic status reflecting active hepatitis B or C infection. Patients that arepositive for hepatitis B core antibody, hepatitis B surface antigen (HBsAg), orhepatitis C antibody must have a negative polymerase chain reaction (PCR) prior toenrollment. (PCR positive patients will be excluded.)

• Any condition that would, in the investigator's judgment, interfere with fullparticipation in the study, including administration of study drug and attendingrequired study visits; pose a significant risk to the participant; or interfere withinterpretation of study data.

• Known allergies, hypersensitivity, or intolerance to any of the study medications,excipients, or similar compounds