A Study of Vadastuximab Talirine Given Prior to or After Allogeneic Hematopoietic Stem Cell Transplant in AML Patients

Inclusion Criteria:

- Relapsed/refractory acute myeloid leukemia (AML) except for acute promyelocytic
leukemia

- Eastern Cooperative Oncology Group status of 0 or 1

- Adequate baseline renal and hepatic function

- For Pre-allo Part A (before stem cell transplant): Relapsed or refractory AML (greater
than 5% blasts)

- For Pre-allo Part A (before stem cell transplant): Availability of an HLA matched
related or unrelated donor

- For Pre-allo Part A (before stem cell transplant): Eligible for an allogeneic
hematopoietic stem cell transplant

- For Post-allo Part B: Transplant must have been performed with active AML (greater
than 5% blasts) using a conventional conditioning regimen and have achieved CR or CRi
post-alloSCT (with ANC greater than or equal to 1,000 and platelet greater than or
equal to 50,000)

- For Post-allo Part B: Treatment must begin at least 42 days, but no more than 100 days
post-transplant.

Exclusion Criteria:

- Inadequate heart function

- Inadequate lung function

- Previous central nervous system leukemia

- Any history of another metastatic malignancy

- Anti-leukemia treatment within14 days of study drug (other than hydroxyurea or
6-mercaptopurine), immunosuppressive therapy (except for GVHD treatment/prophylaxis in
Part B), or investigational agents

- For Pre-allo Part A (before stem cell transplant): Partially matched donors (related
or unrelated) and umbilical cord blood cells are excluded as the source of
hematopoietic stem cells

- For Pre-allo Part A (before stem cell transplant): Prior alloSCT

- For Post-allo Part B: Active GVHD Grade 2 or higher

- For Post-allo Part B:History of veno-occlusive disease requiring defibrotide

- For Post-allo Part B: History of Grade 2 or higher hepatic GVHD

- For Post-allo Part B: Concurrent use of corticosteroids equivalent of prednisone at a
dose of greater than 0.5 mg/kg