A Safety Study of SGN-CD33A in AML Patients

This study will explore SGN-CD33A as a monotherapy and in combination with a hypomethylating
agent (HMA; i.e., azacitidine or decitabine). Initial study treatment with SGN-CD33A includes
a maximum of 2 cycles of treatment for monotherapy and 4 cycles for combination cohorts.
Patients who achieve documented CR or CRi (Monotherapy) or clinical benefit (Combination)
during the first part of the study are eligible to continue treatment.

Additional monotherapy cohorts may include patients with relapsed acute promyelocytic
leukemia, relapsed patients with nucleophosmin-1 gene mutation (absence of fms-like tyrosine
kinase 3 mutation) (NPM1-mutated, FLT-3 wild type), alternate dosing schedules (fractionated
dosing on Days 1 and 4), treatment naive patients with AML who declined intensive therapy,
and patients who have relapsed after post-allogeneic stem cell transplant.

Patients in the combination cohort will be treated with azacitidine or decitabine per
institutional practice prior to SGN-CD33A dosing. Expansion cohorts may be added for further
evaluation of safety, pharmacokinetics, pharmacodynamics, and antitumor activity.

Inclusion Criteria:

- Acute myeloid leukemia, positive for CD33

- Eastern Cooperative Oncology Group status of 0 or 1

- Adequate baseline renal and hepatic function

- Central venous access

- Either achieved complete remission (greater than 12 weeks in duration) with initial
induction/consolidation and have experienced relapse of disease or declined treatment
with high-dose induction/consolidation

- Bone marrow blasts greater than or equal to 5% for relapsed patients, or greater than
or equal to 20% for untreated patients

Exclusion Criteria:

- Inadequate lung function

- Prior allogeneic stem cell transplant, except for a specific cohort

- High-dose chemotherapy within 4 weeks of study drug

- Antileukemia treatment within 14 days of study drug (other than hydroxyurea or
6-mercaptopurine)