Open-label Study of IMGN779 in Adult Patients With Relapsed/Refractory CD33-positive Acute Myeloid Leukemia

In the Dose Escalation Phase, patients will be assigned to one of three schedules. The MTD
for all schedules will be determined from the assessment of Dose Limiting Toxicities (DLTs).
The Dose Expansion Phase will consist of one cohort based on patients response to prior
therapy according to the MTD selected.

Inclusion Criteria:

- Dose Escalation: Patients with relapsed or refractory AML

- Dose Expansion: Patients with relapsed AML or patients who refuse, or are not suitable
candidates for induction therapy

Exclusion Criteria:

- Dose Escalation: Acute Promyelocytic Leukemia

- Any concurrent anti-cancer therapy including chemotherapy, immunotherapy,
radiotherapy, biologic or any investigational agents (with the exception of
hydroxyurea or leukapheresis for control of hyperleukocytosis) within 14 days or five
half-lives of drugs, whichever is shorter, prior to Cycle 1 Day 1

- AML patients with known, active leptomeningeal/central nervous system (CNS)
involvement

- Prior treatment with IMGN779

- Women who are pregnant or breast feeding