Lintuzumab-Ac225 in Combination With CLAG-M Chemotherapy in Patients With Relapsed/Refractory Acute Myeloid Leukemia

Relapsed/refractory acute myeloid leukemia (RR-AML) in adults is an important therapeutic
challenge. Nearly 60% of AML patients ultimately relapse or have refractory disease, and
failure to achieve remission in this population is almost universally fatal. Therefore, a
critical need exists for the development of novel therapies.

Currently, for RR-AML, many institutions utilize the chemotherapy regimen of CLAG-M
(cladribine, cytarabine, G-CSF, mitoxantrone) based on a reported morphological complete
remission (CR) rate of 58% in prospective clinical trials. Because of this, and its favorable
performance when compared with outcomes reported for other regimens utilized in RR-AML, we
believe enhancing the efficacy of CLAG-M is a rational approach to improve therapy in RR-AML.

A promising approach that could enhance the clearance of leukemic blasts when added to CLAG-M
chemotherapy is a monoclonal antibody radioconjugate directed against markers expressed in
leukemic cells. Radiation has known cytotoxic properties in chemo-resistant AML. The benefit
of an antibody radioconjugate would be leukemic specific delivery of potent radiotherapy with
potentially minimal systemic off-target side-effects. One such antibody radioconjugate is
Lintuzumab-Ac225, a highly cytotoxic alpha radiation emitter that targets the CD33 cell
surface antigen, which is expressed on leukemic cells.

In this novel study, we aim to add the radioconjugated antibody Lintuzumab-Ac225 to salvage
CLAG-M chemotherapy in order to improve the treatment response for patients with RR-AML.

Inclusion Criteria:

1. Age ≥18 years at the time of informed consent.

2. Morphologically documented primary AML or secondary AML [from prior conditions such as
Myelodysplastic Syndrome (MDS), myeloproliferative neoplasm (MPN)] or therapy related
AML (t-AML), as defined by World Health Organization (WHO) criteria.

3. In first or subsequent relapse or refractory status after prior therapy, with or
without prior hematopoietic stem cell transplant (HSCT). Patients with MDS and
progression to AML on hypomethylating agents will also be included.

4. Eastern Cooperative Oncology Group (ECOG) performance score 0-2.

5. Greater than 25% of blasts must be CD33 positive on flow cytometry using Phycoerythrin
(PE) labeled anti-CD33 antibody.

6. Patients must meet the following clinical laboratory criteria:

- Total bilirubin ≤ 2 x the upper limit of the normal range (ULN)

- Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 5 x ULN.

- Calculated creatinine clearance ≥ 50 mL/min

- Resting LVEF > 40%

7. Female patients must agree to avoid becoming pregnant, and male patients should avoid
impregnating a female partner.

Exclusion Criteria:

1. Acute Promyelocytic Leukemia.

2. Active severe infection not well controlled by antibacterial or antiviral therapy.

3. Known infection with human immunodeficiency virus.

4. Patients with documented pulmonary disease, with a DLCO and/or FEV1<65%, or history of
dyspnea at rest, or requiring oxygen.

5. Pregnant or breast feeding women.

6. Prior chemotherapy or radiotherapy within 14 days of study entry unless fully
recovered from adverse effects due to treatment, at investigator's discretion.

7. Active malignancy within 2 years of entry, except previously treated melanoma grade 2
or less, non-melanoma skin cancer, carcinoma in situ, or cervical intraepithelial
neoplasia, and organ confined prostate cancer with no evidence of progressive disease
based on PSA levels and are not on active therapy. Active malignancy is malignancy
receiving treatment.