Abstracts

Background: Midostaurin (PKC412) is a FLT3 kinase inhibitorwith activity in acute myeloid leukemia (AML). Hypomethylatingagents play an important role in the treatment of AML and MDS.We investigated the safety (phase I) and clinical activity (phase II) ofcombination of 5-azacytidine (AZA) and PKC412 in pts with R/RAML and MDS. Method: Pts �18 years with MDS, CMML orAML, who failed prior therapies with performance status �2,adequate liver (bilirubin � 2x ULN, ALT � 2.5x ULN) and renal(creatinine � 2x ULN) functions were eligible. Pts received AZA75 mg/m2 subcutaneously or intravenously for 7 days of each cycle(Days 1-7) and PKC412 at 25 mg (cohort 1) and 50 mg (cohort 2;target dose) orally twice daily for 14 days (Days 8-21). Pts plannedto receive up to 12 cycles if benefit from treatment. Supportive carewas standard. Results: 14 pts included in phase I. 1 pt was ineva-luable for DLT (withdrawal before completing cycle#1). 6 ptstreated in cohort 1 and 7 in cohort 2. 1 pt in cohort 2 receivedPKC412 dose as per cohort 1 dose by pt error. Pt characteristics andresponses are summarized in table 1. The overall response rate(ORR) was 3/13(21%) 2 with CRi, 1 pt dropped BM blastsform 27% to 7% after 2 cycles and went to transplant. 1/4 withFLT3-ITD achieved CRi, 2 of the non-responders received priorFLT3 inhibitors (1 had developed FLT3 D835). All toxicities weregrade 1 (nausea 1 pt, vomiting 1 pt, dry skin 1 pt, and rash 1 pt)with no difference between the 2 groups. No DLT was identified.Conclusion: PKC412+AZA is safe and well tolerated at theintended doses with good ORR in high risk pts with R/R AML.Phase II study is enrolling pts with FLT3-ITD. Updated result willbe presented.

Table 1 Patients Characteristics and Responses

Parameter

Number 14

Age, years (range) 61 (38-86)

Median N of prior therapies, N (range) 1 (1-7)

Dose level, N

Cohort 1 6

Cohort 2 7

Inevaluable (cohort 2) 1

Median N of cycles (range) 2 (1-5)

AML history, N (%)

de novo 6 (43)

MDS related 7 (50)

Therapy related AML 1 (7)

Cytogenetic risk group, N (%)

Intermediate 5 (31)

Unfavorable 9 (69)

FLT3-ITD status, N (%)

Positive 4 (29)

Negative 9 (64)

ND 1 (7)

Response rate, N (%)

CRi 2 (14)

PR 1 (7)

SD 3 (21)

504

Phosphorylation of GSK3b is Prognostic forInferior Survival in Acute Myeloid LeukemiaPeter Ruvolo�,1 Gautam Borthakur�,1 YiHua Qiu,1

Kevin Coombes,2 Nianxiang Zhang,2

Marina Konopleva,1 Michael Andreeff,1

Steven Kornblau11Department of Leukemia, The University of Texas MD Anderson

Cancer Center; 2Department of Bioinformatics and Computational

Biology, The University of Texas MD Anderson Cancer Center

Glycogen Synthase Kinase 3b (GSK3b) is a key regulator of cellmetabolism, proliferation, survival, and differentiation. The kinase hasabundant substrates including many proteins in the canonical Wntpathway. Considering that GSK3b phosphorylation of many pro-survival proteins result in their degradation (e.g MYC, MCL-1), it isnot surprising that GSK3b activation by stress challenge results in cellcycle arrest and/or apoptosis. GSK3b is negatively regulated by serine9 phosphorylation mediated by Protein Kinase B (AKT). Since AKTactivation supports survival of AML cells and that inactivation ofGSK3b could suppress stress signaling events, we hypothesize thatserine 9 phosphorylation of GSK3b (p-GSK3b) will be a poorprognostic factor for AML patients. In the current study, weanalyzed GSK3b expression by Reverse Phase Protein Analysis(RPPA) in a cohort of 511 AML patients. GSK3b expression wascorrelated with patient survival data and disease characteristics suchas French-American-British (FAB) classification, cytogenetics, andmutational status. High levels of p-GSK3b were found to correlatewith adverse outcome for survival and complete remission duration(CR) in patients with intermediate cytogenetics but not in thosewith unfavorable cytogenetics. CR was only 45 weeks in the third ofpatients with highest p-GSK3b levels compared to 98 weeks forpatients with low levels (p ¼ 0.0.008; N ¼ 121). Even intermediatecytogentic patients with FLT3 mutation fared better when p-GSK3blevels were lower (50 versus 24 weeks; p ¼ 0.009; N ¼ 35).Consistent with p-GSK3b as an indicator of AKT activation, RPPArevealed p-GSK3b positively correlated with phosphorylation ofAKT (S473), BAD (S136), and P70S6K. These findings suggest thatAKT mediated phosphorylation of GSK3b may be detrimental toAML patients and p-GSK3b may serve as an important prognosticfactor for at least a subset of AML patients.*Both authors contributed equally to the work

**505

Biological and Clinical Features of Trisomy 21Acute Myeloid LeukemiaPaolo Strati, Hagop Kantarjian, Jorge Cortes,Farhad Ravandi, Naveen Pemmaraju,Guillermo Garcia-Manero, Tapan Kadia, Elias Jabbour,Aziz Nazha, Gautam Borthakur, Stefan Faderl,Alfonso Quintas-Cardama, Naval DaverDepartment of Leukemia, UT MD Anderson Cancer Center,

Houston, TX

Clinical Lymphoma, Myeloma & Leukemia September 2013 - S375

Abstracts

S376

Background: Individuals with congenital Trisomy 21 (+21) have anincreased risk of developing acutemyeloid leukemia (AML). AMLwith+21 has traditionally been regarded as an intermediate risk prognosis.This study focuses on the biological and clinical features of patients (pts)with +21 AML. Methods: We analyzed pts treated at University ofTexas MD Anderson Cancer Center (UTMDACC) between 1995and 2011. Only pts that presented to UTMDACC at initial diagnosiswith no prior therapy were included. Four cytogenetic groups weredefined: +21 alone, +21 plus favorable cytogenetics, +21 plus inter-mediate cytogenetics and +21 plus unfavorable cytogenetics. Time toProgression (TTP) was defined as time from diagnosis to relapse orlast follow up. Survival curves were calculated using Kaplan-Meierestimates. Results: A total of 90 pts harboring +21 aberrations atdiagnosis were identified. Median age was 59 years (range, 18-88),58% were male and 72 (80%) were of white race. At diagnosis,median white cell count was 4.6 (0.6-190) x 109/L, neutrophils14 (0-86)%, hemoglobin 8.6 (3.3-13.4) g/dL, platelets 53 (4-395) x109/L , peripheral blasts 17% (0-96), and bone marrow blasts 48%(0-97). FAB classification: M0-2 64%, M3 1%, M4-5 20%, M610%, M7 4%. Cytogenetics: +21 alone 11 (12%), plus favourable 7(8%), plus intermediate 7 (85), plus unfavourable 65 (72%).Molecular mutations: NPM1 1/25 (4%), NRAS 4/53 (7%), CKIT0/26 (0%), FLT3 4/49 (8%). Induction regimens included: Idar-ubicin+AraC-based 36%, fludarabine-based 24%, clofarabine-based11%, topotecan-based 10%, hypomethylating-based 11%, andmiscellaneous 8%. Overall Response Rate was 54%. Median TTP was11 (2-130) months. Conclusions: Pts with AML harboring +21 haveunique biological and clinical features. It rarely presents as a solelyaberration and mostrly associates with complex cytoenetics. Furtherinvestigation is needed to determine its specific prognostic role.

506

ARC Is Regulated by MAPK and PI3K and ConfersDrug Resistance and Survival Advantage to AMLin vitro and in vivoPo Yee Mak, Duncan H Mak, Yuexi Shi, Vivian Ruvolo,Rodrigo Jacamo, Michael Andreeff, Bing Z CarterSection of Molecular Hematology and Therapy, Department of

Leukemia, The University of Texas M. D. Anderson Cancer Center,

Houston, TX

ARC (Apoptosis repressor with caspase recruitment domain), aunique antiapoptotic protein suppresses activations of both intrinsicand extrinsic apoptosis. We previously reported that ARC is one ofthe most potent adverse prognostic factors in AML (Carter BZet al., Blood 2011). Here we report how ARC is regulated and itsrole in inhibition of AML apoptosis and in cell survival.We provide evidence that ARC expression is regulated by MAPK

and PI3K signaling. ARC expression in AML cells is upregulated inco-cultures with bone marrow-derived mesenchymal stromal cells(MSCs) and the upregulation is suppressed in the presence ofMAPK or PI3K inhibitors.To investigate the role of ARC in apoptosis resistance in AML, we

generated stableARCoverexpressing (O/E)KG-1 and stableARCknockdown (K/D) OCI-AML3 and Molm13 cells and treated them with

- Clinical Lymphoma, Myeloma & Leukemia September 2013

Ara-C and agents selectively inducing intrinsic (ABT-737) or extrinsic(TRAIL) apoptosis.We found that ARCO/E cells aremore resistant andARC K/D cells more sensitive to Ara-C, ABT-737, and TRAIL.Bone marrow microenvironment is known to play critical roles in

AML disease progression and in protecting leukemia cells fromvarious therapeutic agent-induced apoptosis. Leukemia cells wereco-cultured with MSCs in vitro study to mimic the in vivo condi-tion. ARC was found to be highly expressed in MSCs and stableARC K/D MSCs were generated. AML cell lines and primary pa-tient samples were co-cultured with ARC K/D or control MSCs andtreated with Ara-C, ABT-737, or TRAIL. Interestingly, ARC K/DMSCs lost their protective activity for leukemia cells treated withthese agents.In addition, ARC O/E cells grew faster and ARC K/D cells grew

slower than controls. We injected KG-1 cells into mice and foundthat NOD-SCID mice harboring ARC O/E KG-1 had significantlyshorter survival than mice injected with the control KG-1 (median84 vs. 111 days, P¼0.0002).Collectively, we demonstrate that ARC is regulated by MSCs

through signaling pathways in AML cells. ARC, both in leukemiccells and in microenvironment, confers drug resistance and survivaladvantage to AML in vitro and in vivo suggesting that ARC is apotential target for AML therapy.

507

Antagonizing IAPs by SMAC Mimetic BirinapantInduces Apoptosis in AML Cells Including AMLStem/Progenitor Cells Alone and in CombinationWith Chemotherapy in vitro and in vivoBing Z. Carter,1 Po Yee Mak,1 Duncan H. Mak,1

Yuexi Shi,1 Yihua Qiu,1 Steven Kornblau,1

Teresa McQueen,1 David Weng,2 Jennifer Burns,2

Michael Andreeff11Section of Molecular Hematology and Therapy, Department of

Leukemia, The University of Texas M. D. Anderson Cancer Center,

Houston, TX; 2TetraLogic Pharmaceuticals, Malvern, PA

The antiapoptotic function of the inhibitors of apoptosis familyof proteins (IAPs) is antagonized by SMAC protein. XIAP inhibitsboth intrinsic and extrinsic apoptosis, while cIAPs suppress deathreceptor/caspase-8 mediated extrinsic apoptosis. SMAC mimeticsinduce cIAP1 degradation, suppress XIAP activity, and promoteTRAIL or TNFa-dependent apoptosis in various malignant cells.To assess the therapeutic potential of SMACmimetics in AML, we

determined levels of IAPs, SMAC, and caspase-8 by reverse phaseprotein array in blasts obtained from 511 newly diagnosed AMLpatients and inCD34+38- stem/progenitor cells isolated fromblasts ofthese patients. We found that levels of cIAP1 and caspase-8 weresignificantly higher and SMAC significantly lower inCD34+38- AMLstem/progenitor cells than those in bulk AML cells (P<0.05).Birinapant is a highly potent SMAC mimetic in clinical develop-

ment that promoted rapid degradation of cIAP1 and induced pro-nounced apoptosis in AML cell lines in the presence of TNFa. Celldeath was enhanced by TRAIL, confirming activation of the deathreceptor pathway as a significant mechanism of apoptosis induction.