The purpose of this study is to assess the feasibility and efficacy of a novel form of therapy-haploidentical NK cell transplantation-in patients with standard-risk AML. In addition, we will investigate the efficacy of clofarabine + cytarabine (Clo/AraC) in newly diagnosed patients with AML and attempt to optimize outcome through the use of MRD-adapted therapy and further improvements in supportive care.

The overall objective of this protocol is to improve the cure rate of acute myeloid leukemia (AML).

We will compare the immunologic complete response rate after one course of therapy in patients who receive cytarabine + daunorubicin + etoposide (ADE) with that in patients who receive clofarabine + cytarabine (Clo/AraC)

Secondary objectives include

• To estimate the event-free survival (EFS) of standard risk (SR) patients who receive chemotherapy alone and the EFS of SR patients who receive chemotherapy followed by natural killer (NK) cell transplantation.

Exploratory Objectives:

• To genotype natural killer (NK) cell receptors and measure their expressions at diagnosis and after induction therapy, and to explore the associations of these features with treatment outcome
• To assess the prognostic value of levels of minimal residual disease in peripheral blood at day 8 of induction I
• To validate new markers and methods for minimal residual disease (MRD) detection
• To identify new prognostic factors by applying new technologies to study patient material
• To identify pharmacogenetic, pharmacokinetic and pharmacodynamic predictors for treatment-related outcomes in the context of the systemic therapy used in the protocol
• To describe the impact of antibiotic and antifungal prophylaxis on invasive bacterial and fungal infections, febrile neutropenia, hospitalization, and antibiotic resistance.
• To determine the performance characteristics of broad-range, molecular diagnostic methods for detection of bacterial, fungal, and viral agents, in comparison to methods currently in routine clinical use

Treatment will be based on cytogenetic and molecular characteristics, morphology, and response to therapy as assessed by flow cytometry. Risk groups are defined below. The general treatment plan will consist of chemotherapy for LR patients, chemotherapy ± NK cell therapy for SR patients, and chemotherapy + stem cell transplant (SCT) for HR patients. HR patients who do not have a suitable stem cell donor or who decline SCT will be eligible for NK cell therapy.

Low-risk (LR) criteria (not eligible for SCT or NK cell therapy)

• Core binding factor (CBF) leukemia [t(8;21)/AML1-ETO or inv(16)/t(16;16)/CBF-MYH11,] and MRD < 0.1% at day 22,regardless of other genetic features.
• Patients with CBF leukemia who have MRD ≥ to 0.1% at day 22 or who have increasing levels of fusion transcript will be considered SR and thus eligible for NK cell therapy.

Standard-risk (SR) criteria (eligible for NK cell therapy)

• Absence of low-risk or high-risk features.
• CBF leukemia with MRD ≥ 0.1% at day 22 or increasing levels of fusion transcript
• FLT3-ITD and MRD < 0.1% at day 22

High-risk (HR) criteria (candidates for SCT; eligible for NK cell therapy)

Presence of one of the following features:

• t(6;9), t(8;16), t(16;21), -7, -5, or 5q-
• FAB M0 or M6
• FAB M7 without t(1;22)
• Treatment-related (secondary) AML
• RAEB-2 or AML arising from prior MDS
• FLT3-ITD and MRD ≥ 0.1% at day 22
• All other patients with poor response to therapy (must have one of the following features) MRD ≥ to 5% at day 22 MRD ≥ to 0.1% after Induction II

Induction therapy (2 courses)

All patients will receive two courses of induction therapy that will include one course of either high dose cytarabine, daunorubicin, and etoposide (HD-ADE) or one course of clofarabine and cytarabine (Clo/AraC), followed by one course of low dose cytarabine, daunorubicin, and etoposide (LD-ADE). Patients will be randomly assigned to receive one of the following induction regimens.

Induction I: HD-ADE

Cytarabine: 3 g/m2 IV over 3 hours q12 hours x 6 doses (days 1, 3, 5) Daunorubicin: 50 mg/m2 (1.67 mg/kg for patients less than 10 kg) IV over 6 hours on days 2, 4, 6 (3 doses) Etoposide: 100 mg/m2 IV over 4 hours on days 2-6 (5 doses)

Induction I: Clo/AraC

Clofarabine: 52 mg/m2 IV over 2 hours on days 1-5 (5 doses) Cytarabine: 1 gram/m2 IV over 2 hours on days 1-5 (5 doses; each dose to start 4 hours after the start of clofarabine)

Induction II: LD-ADE

Cytarabine: 100 mg/m2 IV over 30 minutes q12 hours on days 1-8 (16 doses), Daunorubicin: 50 mg/m2 (1.67 mg/kg for patients less than 10 kg) IV over 6 hours on days 2, 4, 6 (3 doses) Etoposide: 100 mg/m2 IV over 4 hours on days 1-5 (5 doses)

Induction II for patients with FLT3-ITD: LD-ADE + Sorafenib

Patients with FLT3-ITD will take Sorafenib, 400 mg/m2 per day, orally in two divided doses (200 mg/m2/dose BID) starting one day after the completion of Induction II and continuing for 21 days Patients with FLT3-ITD who do not experience toxicity related to Sorafenib will also receive a 21-day course of Sorafenib after subsequent courses of chemotherapy.

Induction II for other HR patients: LD-ADE + vorinostat

[NOTE: Collaborating institutions may elect to opt out of treatment with vorinostat. If a site opts out, then all applicable patients at that site will receive standard induction therapy with LD-ADE (without vorinostat).]

Patients with M7 AML without t(1;22) and other HR patients without FLT3-ITD will be treated with a combination of vorinostat and LD-ADE. Vorinostat will be given orally for 3 days (Days -2, -1, 0) prior to the initiation of Induction II chemotherapy.

Special subgroup HR patients with MRD < 0.1% may proceed directly to SCT after Induction I if a suitable donor is available and the transplant can be performed without delay.

Consolidation I:

Mitoxantrone: 12 mg/m2 (0.4 mg/kg for patients less than 10 kg) IV over 1 hour on days 3-5 (3 doses) Cytarabine: 1 g/m2 IV over 2 hours every 12 hours on days 1-4 (8 doses)

Consolidation II:

Cytarabine 3 g/m2 IV over 3 hours every 12 hours on days 1, 2, 8, 9 (8 doses). Erwinia Asparaginase 25,000 Units/m2 (833 Units/kg for infants < 1 month of age, or for infants < 3 months of age who were born significantly prematurely defined as < 36 weeks gestation) IM or IV over 1 hour, 3 hours after the 4th and 8th doses of cytarabine.

NK cell therapy Standard risk patients who have a KIR-mismatched family member who is greater than 18 years old will undergo NK cell transplantation. In addition, HR patients who do not have a suitable stem cell donor or who decline SCT will be eligible for NK cell therapy if they have a KIR-mismatched family member.

Treatment schema Day -7: Cyclophosphamide 60 mg/kg IV over 1 hour. Mesna 15 mg/kg/dose IV Days -6 through -2: Fludarabine 25 mg/m2/day IV over 30 minutes (5 doses) Days -1, +1, +3, +5, +7, +9: IL-2 1 million units/m2 given subcutaneously Day -1: Donor pheresis Day 0: NK cell infusion

No steroids, including the use of hydrocortisone as pre-medication, may be given to patients during the 3 days prior to the NK cell infusion or during the first 7 days after the infusion.

CNS therapy

Triple intrathecal therapy with methotrexate, hydrocortisone, and cytarabine (MHA) will be used for all CNS therapy at the doses:

< 1 year methotrexate 6 mg, hydrocortisone 12 mg, cytarabine 18 mg, 1-2 years methotrexate 8 mg, hydrocortisone 16 mg, cytarabine 24 mg, 2-3 years methotrexate 10 mg, hydrocortisone 20 mg, cytarabine 30 mg, > 3 years methotrexate 12 mg, hydrocortisone 24 mg, cytarabine 36 mg

Leucovorin rescue (5 mg/m2 per dose; 5 mg maximum per dose) will be given orally or intravenously at 24 and 30 hours after each IT MHA treatment.

Patients with no evidence of CNS disease \[(i.e., no leukemic blast cells on cerebrospinal fluid (CSF) cytospin] will receive 4 total doses of intrathecal therapy, given at approximately one month intervals or at the beginning of each of the first 4 courses of chemotherapy.IT therapy will not be given before NK cell therapy.

Patients with overt CNS leukemia (less than or equal to 5 leukocytes per l of CSF and the presence of leukemic blast cells on CSF cytospin) will receive weekly intrathecal therapy until the CSF is free of blast cells (minimum number of doses, 4). These patients will then receive 4 additional doses of intrathecal therapy (minimum total number of doses, 8) at approximately 1-month intervals (generally given with each subsequent course of chemotherapy).IT therapy will not be given before NK cell therapy.

Patients with < 5 leukocytes per mul of CSF and the presence of leukemic blast cells on CSF cytospin (CNS2)will receive weekly intrathecal therapy until the CSF is free of blast cells. These patients will then receive 4 additional doses of intrathecal therapy at approximately 1-month intervals (generally given with each subsequent course of chemotherapy).IT therapy will not be given before NK cell therapy.

Patients who are unable to undergo lumbar puncture and receive intrathecal therapy prior to starting induction I should be treated as CNS2 unless they have overt CNS leukemia (CNS3).

Inclusion Criteria:

• Age less than or equal to 21 years at time of study entry.
• No prior therapy for this malignancy except for one dose of intrathecal therapy and the use of hydroxyurea or low-dose cytarabine (100-200 mg/m2 per day for one week or less ) for hyperleukocytosis.
• Written informed consent according to institutional guidelines
• Female patients of childbearing potential must have a negative serum pregnancy test within 2 weeks prior to enrollment
• Male and female participants must use an effective contraceptive method during the study and for a minimum of 6 months after study treatment.

Exclusion Criteria:

• Down syndrome
• Acute Promyelocytic Leukemia (APL)
• Juvenile Myelomonocytic Leukemia (JMML)
• Fanconi anemia (FA)
• Kostmann syndrome
• Shwachman syndrome
• Other bone marrow failure syndromes
• Use of concomitant chemotherapy, radiation therapy, or immunotherapy other than as specified in the protocol.
• Use of investigational agents within 30 days or any anticancer therapy within 2 weeks before study entry with the exception of IT therapy, hydroxyurea, or low-dose cytarabine as stated above. The patient must have recovered from all acute toxicities from any previous therapy.
• Systemic fungal, bacterial, viral, or other infection not controlled (defined as exhibiting ongoing signs/symptoms related to the infection and without improvement, despite appropriate antibiotics or other treatment).
• Pregnant or lactating patients.
• Any significant concurrent disease, illness, or psychiatric disorder that would compromise patient safety or compliance, interfere with consent, study participation, follow up, or interpretation of study results.