ALBERT

Description: Bortezomib (BTZ) was recently evaluated in a randomized Phase 3 clinical trial which compared standard chemotherapy (cytarabine, daunorubicin, etoposide; ADE) to standard therapy with BTZ (ADEB) for de novo pediatric acute myeloid leukemia. While the study concluded that BTZ did not improve outcome overall, we examined patient subgroups benefitting from BTZ-containing chemotherapy using proteomic analyses. The proteasome inhibitor BTZ disrupts protein homeostasis and activates cytoprotective heat shock responses. We measured total heat shock factor 1 (HSF1) and phosphorylated HSF1 (HSF1-pSer326) in leukemic cells from 483 pediatric patients using Reverse Phase Protein Arrays. HSF1-pSer326 phosphorylation was significantly lower in pediatric AML compared to CD34+ non-malignant cells. We identified a strong correlation between HSF1-pSer326 expression and BTZ sensitivity. BTZ significantly improved outcome of patients with low-HSF1-pSer326 with a 5-year event-free survival of 44% (ADE) vs. 67% for low-HSF1-pSer326 treated with ADEB (P=0.019). To determine the effect of HSF1 expression on BTZ potency in vitro, cell viability with HSF1 gene variants that mimicked phosphorylated (S326A) and non-phosphorylated (S326E) HSF1-pSer326 were examined. Those with increased HSF1 phosphorylation showed clear resistance to BTZ vs. those with wild type or reduced HSF1-phosphorylation. We hypothesize that HSF1-pSer326 expression could identify patients that benefit from BTZ-containing chemotherapy.

Description: Our group and others have shown that acute myeloid leukemia (AML) cells have unique mitochondrial characteristics with an increased reliance on oxidative phosphorylation. Through an shRNA screen for new biological vulnerabilities in the mitochondria of AML cells, we identified the mitochondrial protease, neurolysin (NLN). NLN is a zinc metalloprotease whose mitochondrial function is not well understood and whose role in AML growth and viability has not been previously reported. We analyzed the expression of NLN in AML cells and normal hematopoietic cells. By immunoblotting, NLN was overexpressed in 80% of primary AML patient samples compared to normal hematopoietic cells. Likewise, in an analysis of gene expression databases, NLN mRNA was increased in a subset of AML patient samples, compared to normal hematopoietic cells. Next, we assessed the effects of knocking down NLN in AML cell lines (OCI-AML2, NB4, and MV4-11) using three independent shRNAs in lentiviral vectors. Target knockdown was confirmed by immunoblotting. NLN knockdown reduced growth in all three tested cell lines by 50-70%. NLN knockdown also targeted the leukemia initiating cells in vitro and in vivo as NLN knockdown reduced the clonogenic growth of AML cells (40-75%) and the engraftment of TEX cells into immune deficient mice by 85%. Taken together, these data suggest that NLN is necessary for the growth of AML cells. The role of NLN in the mitochondria is not well understood. To gain insight into NLN's mitochondrial function, we investigated NLN's protein interactors using proximity-dependent biotin labeling (BioID). The top hits in the protein-protein interaction screen were mitochondrial matrix proteins and respiratory chain subunits were particularly enriched. Therefore, we measured the effects of NLN knockdown on mitochondrial structure and function. Knockdown of NLN in AML cells reduced basal oxygen consumption without altering reactive oxygen species generation, mitochondrial membrane potential, or mitochondrial mass. No changes were seen in the total levels of respiratory chain complex subunits as measured by immunoblotting on denaturing gels. Respiratory chain complexes assemble into higher order supercomplex structures that maintain the integrity of the mitochondria and promote efficient oxidative metabolism. Therefore, we tested whether NLN is required for the formation of respiratory chain supercomplexes. As measured by blue native polyacrylamide gel electrophoresis, knockdown of NLN impaired the formation of respiratory chain supercomplexes. Through our BioID analysis, we also identified the mitochondrial Ca2+/H+ antiporter, LETM1 (leucine zipper-EF-hand containing transmembrane protein 1) as a top interactor with NLN. LETM1 is a known regulator of respiratory chain supercomplex formation. We showed that knockdown of NLN impaired LETM1 assembly, potentially explaining how NLN regulates supercomplex formation. Finally, we tested if hypoxia influences respiratory chain supercomplex formation and sensitivity to NLN inhibition. OCI-AML2 cells cultured for 72 hours under hypoxic conditions (0.2% O2) showed impaired assembly of respiratory chain supercomplexes, decreased levels of LETM1 protein, and resistance to NLN knockdown. Thus, we discovered that the mitochondrial protease NLN regulates oxidative metabolism by controlling the assembly of respiratory chain supercomplexes. Moreover, we highlight NLN as a potential new therapeutic target for AML. Disclosures Schimmer: Otsuka Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Medivir AB: Research Funding; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees.

Description: Immunotherapy targeting individual antigens in acute myeloid leukemia (AML) has shown promise. However, in view of leukemia heterogeneity and the loss of tumor antigen expression by AML, it is unlikely that any single antigen will be consistently expressed by all leukemia cells. This highlights the need to identify additional antigens in AML that can be targeted. Azurophil granule proteases have been shown to be effective immunotherapeutic targets. Proteinase 3 and neutrophil elastase, the parent proteins for the HLA-A2 restricted peptide PR1, have been targeted successfully in myeloid leukemia using immunotherapy. We recently discovered the HLA-A2 restricted peptide CG1 (FLLPTGAEA), which is derived from the azurophil granule protease cathepsin G (CG). We showed that CG is highly expressed by AML blasts and leukemia stem cells in a limited number of AML samples and showed that CG1 can be targeted in vitro using CG-specific cytotoxic T lymphocytes (CTL). We sought to determine whether CG1 can be targeted in vivo and to characterize the expression of CG in a large cohort of AML patients. To assess the efficacy of targeting CG1 in vivo, we used a NOD scid gamma (NSG) mouse model engrafted with the human HLA-A2+ AML cell line U937 (U937-A2), which is known to express CG. Mice were injected with U937-A2 (0.5 x 106) cells and on the following day were treated with either CG1-CTL (0.25 x 106), negative control HIV-CTL expanded from the same donor or were left untreated. Mice treated with CG1-CTL demonstrated a significantly greater reduction in U937-A2 in the bone marrow (BM) (8% residual AML; P

Description: NPM1 mutations are one of the most common alterations observed in acute myeloid leukemia (AML). When coupled with wild type FLT3 status in cytogenetically normal (CN) patients, NPM1 mutations confer favorable prognoses compared with other alterations. However, a subset of CN NPM1Mut :FLT3Wt patients with AML have dismal outcomes, suggesting that uncharacterized alterations influence the outcomes in these patients. To address this, we performed reverse phase protein array (RPPA) analysis on CD34+ bone marrow cells isolated from 43 de novo CN NPM1Mut :FLT3Wt AML patient as well as healthy donor controls. Through these analyses, we observed that overexpression of heterogeneous nuclear ribonucleoprotein K (hnRNP K) associated with extremely poor outcomes within this a priori favorable prognostic group, as almost 90% of patients with increased hnRNP K expression died within 12 months of diagnosis while nearly 40% of individuals with normal hnRNP K expression survived seven years (Figure 1A). hnRNP K is a multifunctional RNA and DNA binding protein whose expression is often altered in cancers. To directly examine the functional relationship between hnRNP K overexpression and mutant NPM1 in hematologic malignancies, we generated tissue-specific transgenic mouse models with the ability to overexpress hnRNP K (hnRNP KTg) in the presence or absence of mutant Npm1 (Npm1Tg). By crossing these mice with Vav-Cre expressing mice, we specifically activated hnRNP K overexpression and mutant NPM1 expression in the hematological compartment. Using Lin-CD117+ hematopoietic stem cells (HSCs) from hnRNP KTg, Npm1Tg, and hnRNP KTg;Npm1Tg mice, we observed significant changes in differentiation and proliferation potential in colony formation assays. Overexpression of hnRNP K alone significantly increased the number of colonies compared to wild type and Npm1Tg HSCs while expression of mutant Npm1Tg resulted in increased numbers of cells compared to wild type and hnRNP KTg HSCs. Importantly, the combination of hnRNP K overexpression and mutant Npm1 resulted in a cumulative increase in both the number of colonies and number of cells, indicating that hnRNP K and mutant NPM1 cooperate to dictate differentiation and proliferation potential in HSCs (Figure 1B). Next, we examined the in vivo impact of hnRNP K overexpression and mutant Npm1 expression by analyzing the bone marrows of Npm Tg, hnRNP KTg, and Npm1Tg;hnRNP KTg mice. Within the first six months of life, these mice rapidly developed significant myeloid hyperplasias as determined by flow cytometry and pathologic analyses (Figure 1C). Together, our findings reveal that mutant Npm1 and hnRNP K overexpression result in similar myeloid phenotypes. However, these genetic alterations are also cooperative, suggesting both increased hnRNP K expression and mutant NPM1 synergize to impact hematopoietic phenotypes and drive AML progression through similar pathways but potentially via unique molecular processes. Currently, we are investigating the direct interaction and global relationship between hnRNP K and mutant Npm1 in regulating tumor suppressor and oncogenic programs (e.g.; p53- and c-Myc pathways). Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Description: Abstract 1026 Poster Board I-48 Background: FLT3 mutations (ITD or D835 point mutation) are frequently observed in patients (pts) with AML and they confer an adverse prognosis, particularly among pts with diploid karyotype. This has made FLT3 an important target for drug development in AML. Several FLT3 inhibitors are currently being developed (eg, sorafenib, PKC-412, AC-220, CEP-701, IMC EB10, sunitinib). Results from early trials with many of these agents suggest they have clinical activity in the treatment of MDS and AML, although most responses are represented by a marked decrease in blast counts, with few complete remissions(CR). Whether these responses ultimately improve long-term outcome of pts, and whether they may be particularly beneficial for pts with FLT3 mutations compared to those with FLT3 wild-type (WT) is being investigated. Aims: To ascertain outcomes of patients given treatment with FLT3 inhibitors, alone or in combination with other therapies, and to compare outcomes in those patients with FLT3 mutations (ITD or D835) versus those with FLT3-WT. Methods: We reviewed the records of patients with MDS and AML who were enrolled on clinical trials with FLT3 inhibitors at our institution. We compared patient outcomes in those who received a FLT3 inhibitor in both FLT3 positive and FLT3 negative patients. Pts were classified as receiving FLT3 inhibitors 1) as part of their initial therapy, 2) as first salvage, or 3) as second salvage or beyond. Results: A total of 128 pts were included: 51 (40%) with FLT3-WT, 56 (44%) with FLT3-ITD, 11 (9%) with D835, and 10 (8%) had both FLT3-ITD and D835. The overall median age was 62 yrs (range, 17-88); by FLT3 status, median age was 70 yrs (35-88) for FLT3-WT pts and 58 yrs (17-81) for FLT3 mutated. Sixty-four pts (50%) were female. Twenty-three (18%) pts received FLT3 inhibitors as part of their induction therapy (18 FLT3-WT, 5 FLT3 mutated; median age 74 yrs); 22 (17%) as first salvage (4 FLT3-WT, 18 mutated; median age 67 yrs); and 83 (65%) as second or later salvage (29 FLT3-WT, 54 mutated; median age 59 yrs). Nine pts overall, all of whom were FLT3 mutated, achieved either CR (n=6) or CRp (n=3) with FLT3 inhibitors. Eight of the nine CR/CRp have been lost with a median CR duration of 8 months (mo) (3-12+). After a median follow-up of 3.5 mo, 115 (90%) pts have died, including 47 (92%) FLT3-WT, and 68 (88%) FLT3 mutated. The median survival is 3.8 mo for the total population. Survival by mutation status and timing of FLT3 inhibitor therapy is presented in table 1. Conclusions: Despite the inferior outcome expected for pts with FLT3 mutations, and the low rate of CR/CRp with FLT3 inhibitors, these results suggest that therapy with FLT3 inhibitors has the potential to improve the outcome of pts with FLT3 mutations. Additional studies incorporating these agents in AML therapy are warranted. Disclosures: Off Label Use: Sorafenib has not been FDA approved for use in MDS and AML. Kantarjian:Novartis: Research Funding. Cortes:Ambit: Research Funding; Novartis: Research Funding; ImClone: Research Funding.

Description: Clofarabine (CLO) is a second-generation nucleoside analog with activity in acute leukemias. Whereas it has received FDA approval in children with relapsed acute lymphoblastic leukemia, the focus of clinical research in adults has shifted to AML. To improve single agent activity, various CLO combinations are being studied. Here we present the results of two dose-finding phase I studies, exploring combinations of CLO with idarubicin (IDA) [CI] and CLO+IDA+Ara−C [CIA] in patients (pts) with relapsed or refractory AML and high-risk MDS. Eligibility for CI required previous Ara-C and primary refractory disease, or relapsed AML with first remission duration (CRD1) 〈 12 mos. Eligibility for CIA required either no previous Ara-C or Ara-c with CRD1 ≥ 12 mos. Maximum tolerated dose (MTD) was determined by “3+3” method. Forty-four pts (CI 23; CIA 21) have been accrued and are evaluable. The median age of pts on CI was 56 yrs (range 24–71), 9 were primary refractory and 14 in first relapse (median CRD1 2 mos. [0–9]). Fifteen pts had abnormal cytogenetics (including 6 with -5, -7, or 11q23). Sixteen pts had intermediate- or high-dose Ara-C-based prior therapy, 2 relapsed from allogeneic transplant (SCT). The median age of pts on CIA was 56 yrs (23–78), 8 were primary refractory and 13 in first relapse (median CRD1 9 mos [0–61]). Twelve pts had an abnormal karyotype (-5, -7, or 11q23 in 6 pts). Twelve pts received intermediate dose Ara-C-based prior therapy and 2 failed unrelated donor SCT. The starting dose level of the CI group was CLO 22.5 mg/m2 iv daily x 5d and IDA 12 mg/m2 iv daily x 3d. Three DLTs occurred (diarrhea, rash, ↑ bilirubin) requiring dose de-escalation to CLO 15 mg/m2/d x 5d and IDA 8 mg/m2/d x 3d. Gradual re-escalation led to CLO 30 mg/m2/d x 5d and IDA 10 mg/m2/d x 3d where 2/5 pts experienced DLTs (↑ SGPT, ↑ bilirubin, headache). MTD was defined by the next lower dose level: CLO 22.5 mg/m2/d x 5d and IDA 10 mg/m2/d x 3d. Three (13%) CR occurred. The CIA group started at CLO 22.5 mg/m2/d x 5d, IDA 8 mg/m2/d x 3d, and Ara-C 1g/m2/d x 5d. Two pts developed DLTs (diarrhea, ↑ bilirubin, renal failure) requiring de-escalation to CLO 15 mg/m2/d x 5d, IDA 6 mg/m2/d x 3d, and Ara-C 0.75 g/m2/d x 5d. Re-escalation to CLO 30mg/m2/d x 5d, IDA 6mg/m2/d x 3d, and Ara-C 0.75 g/m2/d x 5d revealed DLTs in 2/6 pts (diarrhea, mucositis, ↑ bilirubin). MTD was thus defined at next lower dose level of CLO 22.5 mg/m2/d x 5d, IDA 6 mg/m2/d x 3d, and Ara-C 0.75 g/m2/d x 5d. Ten (48%) responses (9 CR, 1 CRp) occurred. The higher response rate of CIA may be due to the difference in pt characteristics between the two trials. A phase II study is now in progress adaptively randomizing patients with AML relapse to CI versus CIA versus CLO (40 mg/m2/d x 5d) plus Ara-C (1 g/m2/d x 5d) (as established in an earlier study) to assess activity of the combinations.

Description: Introduction: Approximately 77% of younger pts and 49% of older pts with newly diagnosed AML achieve CR after induction chemotherapy (chemo). The majority of pts who achieve CR eventually relapse, with only approximately 30% of pts maintaining CR for 3 yrs or longer. Long-term outcomes in pts maintaining 1st CR for at least 3 yrs (AML survivors) remain largely unknown. The purpose of this study was to investigate long-term outcomes in this subset of pts. Methods: We performed a chart review of pts with AML treated at our institution from 2000-2015 who achieved CR for at least 3 yrs after their initial chemo ± allogeneic stem cell transplant (ASCT) to analyze their long-term outcomes. Results: 2779 pts with AML were treated between 2000 and 2015 at our institution with 1686 (61%) pts achieving CR. Among them, 455 (27%; 16% of all treated) maintained 1st CR for at least 3 years and constitute the focus of this analysis. Among them 309 received chemo alone and 146 chemo followed by ASCT. The median time from the initiation of induction chemo to the first CR was 29 days [10-207] for the entire cohort, and it was similar for pts treated with chemo only versus those who later received ASCT. Baseline characteristics for AML survivors were as follows: hypertension (HTN) in 27% of pts; dyslipidemia (DLD) in 16%; pulmonary disease in 10%; cardiac disease in 9%; diabetes mellitus (DM) in 9%; depression in 5%, renal disease in 5%; gastroesophageal reflux disease (GERD) in 5%; hypothyroidism in 5%; anxiety in 4%; osteopenia/osteoporosis in 1%. Late relapses (i.e., after 3 years in CR) occurred in 11% of pts - 14% treated with chemo alone and 6% treated with ASCT. Such relapses occurred after a median CR duration of 6 yrs (3-12) and 7 yrs (4-12) respectively. A change in karyotype compared to the original karyotype was seen in 51% of relapsed chemo pts and 56% of relapsed ASCT pts. The most common new cytogenetic abnormalities were 7q del (22%), Trisomy 8 (11%), and 5q del (7%). The two most common mutational status changes seen in relapsed pts were FLT3-ITD appearing in 5% of chemo pts while disappearing in 11% of ASCT pts and FLT3-D835 appearing in 5% of chemo pts while disappearing in 2% of chemo pts. Patients treated with ASCT did not display a change in FLT3-D835. At relapse, TP53 mutation was seen in 7% of pts; however, TP53 status at the time of diagnosis was unknown. A 2nd complete remission (CR2) was achieved in 54% of late relapse pts: 51% of chemo only pts and 67% of ASCT pts. The median CR2 duration was 18 months (mo) [3-127] and 15 [7-23] respectively. The median survival after relapse was 10 mo in chemo only pts and 14 mo in ASCT pts. Of chemo pts who relapsed, 30% underwent an ASCT and 4 ASCT pts received a 2nd ASCT. New comorbidities that were present at or after the 3 yr mark included: HTN in 15%; osteopenia/osteoporosis in 15%; renal disease in 14%; pulmonary disease in 11%; hematologic complications in 11%; DLD in 9%; GERD in 8%; cardiac ailments in 7%; depression and anxiety in 7% and 6% respectively; DM in 6%; hypothyroidism in 4%. Osteopenia/osteoporosis was seen in 39% of ASCT pts and 3% of chemo pts. Renal disease was seen in 23% of ASCT pts and 10% of chemo pts. Pulmonary disease was seen in 16% of ASCT pts and 9% of chemo pts. Second malignancies occurred in 17% of pts with the most common being skin cancer (7%), prostate cancer (2%), breast cancer (1%), and lymphoma (1%). Skin cancer occurred in 12% of ASCT pts and 5% of chemo pts. The median survival for the entire cohort starting from 3 yrs in CR is 10.7 yrs (0.1-14.3) with chemo pts having a median survival of 10.7 yrs (0.1-14.3) and 12.7 yrs (0.1-12.7) for ASCT pts (Fig 1). The most common causes of death (COD) for relapse ASCT pts was relapsed AML (33%), complications secondary to 2nd ASCT (22%), and infection (11%); the most common COD for relapse chemo pts was relapsed AML (47%), complications secondary to ASCT (14%), and second malignancy (2%). The most common COD for CR1 ASCT pts was ASCT-related complications (2%), malignancy (

Description: BCR-ABL1-like B-progenitor acute lymphoblastic leukemia (B-ALL) accounts for 10-15% of childhood B-ALL and is characterized by alteration of IKZFI, a gene expression profile similar to BCR-ABL1 ALL and poor outcome. Using next-generation sequencing, we have shown that BCR-ABL1-like ALL patients harbor genetic alterations activating kinase pathways that are sensitive to tyrosine kinase inhibitors (TKIs), and have shown that refractory BCR-ABL1-like ALL is responsive to TKIs in vivo (Weston et al., J. Clin. Oncol 2013). Furthermore, the outcome of ALL in adolescent and young adult (AYA) patients is inferior to children, yet the genetic basis underlying treatment failure is poorly understood. To define the frequency and genomic landscape of BCR-ABL1-like ALL in children, adolescents, and young adults we have extended our studies to include 665 high-risk childhood (

Description: Abstract 3625 Background: SL-401 is a novel biologic targeted therapy, comprised of human IL-3 coupled to a truncated diphtheria toxin payload that inhibits protein synthesis, directed at the interleukin-3 receptor (IL-3R). IL-3R is overexpressed on leukemia blasts and cancer stem cells (CSCs) relative to normal hematopoietic cells. Since SL-401 uniquely targets both the leukemia blasts (tumor bulk) and CSCs, it would be expected to induce tumor regression (anti-tumor bulk effect), as well as inhibit tumor repopulation (anti-CSC effect), thereby improving survival. SL-401 has been evaluated in a Phase 1/2 clinical trial in patients with advanced hematologic cancers. In this study, SL-401 has demonstrated objective clinical responses, including durable complete responses (CRs) and protracted overall survival (OS) in patients with heavily pretreated AML. The current report is a final analysis of the patients with AML or MDS. Study Design: Seventy-eight patients with advanced hematologic cancers, including relapsed or refractory AML (n = 59), de novo AML unfit for chemotherapy (n = 11), high-risk MDS (n = 7), and other (n = 1), were enrolled in a multicenter study. Among the patients with relapsed or refractory AML, the numbers of patients receiving SL-401 as 2nd, 3rd, or 〉3rd line therapy were 24, 16, and 19, respectively. The median (range) age for AML patients was 65 (7, 84) years. Patients received SL-401 as a 15-minute intravenous infusion in one of two dosing regimens for a single cycle to determine the maximum tolerated dose (MTD) and assess antitumor activity. In Regimen A, 45 patients received doses ranging from 4 to 12.5 μg/kg every other day for up to 6 doses. In Regimen B, 33 patients received doses ranging from 7.1 to 22.1 μg/kg daily for up to 5 doses. Results: A single cycle of SL-401 demonstrated single agent activity in patients with relapsed or refractory AML, including 2 durable CRs of 8 and 〉25 months duration and 5 partial responses (PRs). OS was also notable among patients who received one cycle of SL-401 as ≥3rd line therapy for AML; the median OS was 3.6 (2.3, 6.1) months. Moreover, at therapeutically relevant doses, defined as the MTD or one or two dose levels below the MTD (9.4, 12.5, or 16.6 μg/kg/day), the median OS among AML patients who received SL-401 as ≥3rdline therapy (n = 16) was 5.6 (2.5, 10.8) months. These OS values compared favorably to historical results of 1.5 months for patients treated with standard chemotherapy. SL-401 was well tolerated. The MTD was not achieved with Regimen A, whereas the MTD for Regimen B was 16.6 μg/kg/day, with manifestations of capillary leak syndrome, including hypoalbuminemia and edema, as the dose-limiting toxicity (DLT) at the 22.1 μg/kg/day dose level. Transient (i.e., lasting ≤2 weeks) transaminase elevations were among the most common ≥Grade 3 AEs. Notably, there was no evidence of treatment-related bone marrow suppression. Conclusion: SL-401 demonstrated single agent anti-tumor activity and was well tolerated in patients with advanced AML. Improved survival was observed among patients who received a single cycle of SL-401 as ≥3rd line treatment, a disease setting in which there is no standard therapy. SL-401 may be an attractive treatment option for these patients given their tendency to be myelosuppressed and therefore are often poor candidates for myelosupressive therapies that have limited benefit on clinical response and survival in this setting. Based on these positive findings, SL-401 will be advanced into a randomized Phase 2b trial to treat patients with AML in the 3rd line setting. Patients will be randomized to treatment with either multiple cycles of SL-401 or physician's choice, which will consist of available standard therapeutic agents. In addition, the efficacy and safety of SL-401-based combination therapy will also be studied in earlier lines of AML given the lack of overlapping toxicities with existing hematologic cancer therapies. Disclosures: Konopleva: Stemline Therapeutics: Research Funding. Cirrito:Stemline Therapeutics: Employment, Equity Ownership, Patents & Royalties. Hoberman:Stemline Therapeutics: Employment, Equity Ownership. Szarek:Stemline Therapeutics: Consultancy, Equity Ownership. Rowinsky:Stemline Therapeutics: Employment, Equity Ownership. Bergstein:Stemline Therapeutics: Employment, Equity Ownership, Patents & Royalties. Frankel:Stemline Therapeutics: Research Funding.

Description: Background: Patients (pt) with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) who are elderly, or have secondary AML (sAML), or relapsed/refractory (R/R) disease have poor outcomes. Venetoclax (VEN), an oral BCL2 inhibitor, has shown activity in R/R AML as single-agent and in combination with hypomethylating agents (HMA) in newly diagnosed unfit AML. We designed a phase II trial to evaluate the safety and efficacy of VEN with 10-days (D) of decitabine (DEC) in AML and high risk MDS. Methods: Eligible AML pts included those who had failed prior therapy, or were newly diagnosed (ND) elderly pts (〉60 years), or had sAML. ECOG score ≤3, WBC count ≤10 x109/L, and adequate organ function were required. VEN was given on day 1-28 in cycle (cy) 1 and D1-21 in cy 2 onwards; and was interrupted on C1D21 if the 21D bone marrow showed clearance of blasts, until count recovery. VEN was dosed 200 mg PO daily (50% dose reduction) in pts needing CYP3A4 inhibitors. DEC was given 20 mg/m2 IVdaily on D1-10 until CR/CRi, followed by 5-day cycles. Hydroxyurea or ara-C could be used for cytoreduction prior to starting therapy. Prophylactic antimicrobials were used until neutrophil recovery. Tyrosine kinase inhibitors could be used in applicable patients. Primary objective was to determine overall response rate (ORR) including complete remission (CR), CR with incomplete blood count recovery (CRi), partial remission (PR), and morphologic leukemia-free state in pts with AML. Secondary objectives were to determine safety of the combination; duration of response (DOR), disease-free survival (DFS) and overall survival (OS). Results: 48 pts were enrolled between January and May 2018 (Table 1). 24 pts (50%) had ND AML, 7 pts (15%) had sAML, and 16 pts (33%) had R/R AML. Prior therapies are listed in Table 1. The overall CR/CRi rate was 71% (34/48). CR/CRi rate for ND, sAML and R/R AML were 92%, 71% and 44%, respectively (Table 2). Negative minimal residual disease (MRD-) by flow cytometry at the time of response was achieved in 16/33 responding pts (49%). CR/CRi with MRD- was achieved in 11/21 pts with ND AML (52%), 2/5 pts with sAML (40%), and 3/6 pts w R/R AML (50%). CR/CRi rate in TP53 mutated pts was 67% (8/12, Table 2). Additional therapies included ponatinib in 1 pt with AML and t(9;22) who achieved a CRi; and sorafenib in 5 pts (4 FLT3-ITD, 1 FLT3 S749L variant) of which 2 ITD pts achieved CRi and 3 pts did not respond. Median time to first response was 43D (range 20-110) with a median of 1 cy to best response (range 1-3). At a median follow-up of 2.3 months (mo; range 1.4-5.7), pts had received a median of 2 cy (range 2-5) and 32 pts continue on study. Reasons for discontinuation are shown in Table 3. Median OS has not been reached (NR) for ND and sAML pts (NR, range 1.8 mo-NR) and R/R AML (NR, range 0.4 mo-NR, Fig 1a). Median DFS (Fig 1b) and DOR for ND and sAML pts are also NR (range 0.9 mo-NR). Median DFS and DOR for R/R AML pts were 3.3 mo (range 0.5-NR). 10 pts received GCSF. 59 treatment-emergent adverse events (TEAE) occurred in 31 pts, out of which 48 were grade (gr) 3/4. The most frequent gr 3/4 TEAE were infections, with gr 3/4 neutropenia (53%), febrile neutropenia (14%), and tumor lysis syndrome (TLS, n=2, 4%). 1 pt with WBC count 12 x109/L developed TLS on C1D2 which resolved with rasburicase and holding VEN; another pt with WBC count 28 x109/L developed TLS on C1D2 needing hemodialysis for 12 days, prompting study amendment to the current baseline WBC≤10 x109/L. Time to blood count recovery are shown in Table 4. There were total 6 deaths, all in pts with R/R AML (n=5) and treated sAML (n=1), including 3 deaths in hospice, 2 early deaths in relapsed AML pts due to infection; and 1 early death in a relapsed MDS pt due to pneumonia and acute kidney injury unrelated to therapy. There were no deaths in the ND AML pts. 30D and 60D mortality rates were 8% and 10%, respectively. Preliminary BH3 profiling data in R/R cohort showed BCL-2 priming (by assessing cytochrome C release to recombinant BAD peptide and ABT-199) in 7/8 pts irrespective of their response; however, pts who failed to achieve CR/CRi demonstrated co-dependence on other anti-apoptotic proteins MCL-1, BCL-XL and A1 (Fig 2). Additional BH3 profiling and CyTOF analyses are ongoing. Conclusion: The DEC10-VEN regimen had an acceptable safety profile and excellent response rates with CR/CRi of 92% in ND AML, 71% in sAML, and 44% in R/R AML with MRD- in 52% of ND AML, 40% of sAML and 50% of R/R AML. Trial is continuing to accrue (NCT03404193). Disclosures Maiti: Celgene Corporation: Other: Research funding to the institution. DiNardo:AbbVie: Consultancy, Other: Advisory role; Agios: Consultancy, Other: Advisory role; Bayer: Other: Advisory role; Celgene: Other: Advisory role; Medimmune: Other: Advisory role; Karyopharm: Other: Advisory role. Cortes:Novartis: Consultancy, Research Funding; Arog: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Astellas Pharma: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding. Pemmaraju:plexxikon: Research Funding; novartis: Research Funding; Affymetrix: Research Funding; samus: Research Funding; cellectis: Research Funding; celgene: Consultancy, Honoraria; SagerStrong Foundation: Research Funding; abbvie: Research Funding; daiichi sankyo: Research Funding; stemline: Consultancy, Honoraria, Research Funding. Kadia:Celgene: Research Funding; Amgen: Consultancy, Research Funding; Jazz: Consultancy, Research Funding; Takeda: Consultancy; BMS: Research Funding; BMS: Research Funding; Pfizer: Consultancy, Research Funding; Amgen: Consultancy, Research Funding; Novartis: Consultancy; Celgene: Research Funding; Abbvie: Consultancy; Jazz: Consultancy, Research Funding; Abbvie: Consultancy; Novartis: Consultancy; Takeda: Consultancy; Pfizer: Consultancy, Research Funding. Ravandi:Amgen: Honoraria, Research Funding, Speakers Bureau; Abbvie: Research Funding; Bristol-Myers Squibb: Research Funding; Jazz: Honoraria; Sunesis: Honoraria; Abbvie: Research Funding; Xencor: Research Funding; Sunesis: Honoraria; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Macrogenix: Honoraria, Research Funding; Orsenix: Honoraria; Astellas Pharmaceuticals: Consultancy, Honoraria; Xencor: Research Funding; Astellas Pharmaceuticals: Consultancy, Honoraria; Jazz: Honoraria; Bristol-Myers Squibb: Research Funding; Amgen: Honoraria, Research Funding, Speakers Bureau; Macrogenix: Honoraria, Research Funding; Orsenix: Honoraria. Short:Takeda Oncology: Consultancy. Daver:BMS: Research Funding; ImmunoGen: Consultancy; Incyte: Consultancy; Otsuka: Consultancy; Daiichi-Sankyo: Research Funding; Incyte: Research Funding; Novartis: Consultancy; Sunesis: Research Funding; Karyopharm: Research Funding; Pfizer: Research Funding; Alexion: Consultancy; Karyopharm: Consultancy; Pfizer: Consultancy; Sunesis: Consultancy; Kiromic: Research Funding; ARIAD: Research Funding; Novartis: Research Funding. Sasaki:Otsuka Pharmaceutical: Honoraria. Thompson:Gilead Sciences: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Research Funding; AbbVie: Honoraria, Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jain:Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; Servier: Research Funding; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Research Funding; ADC Therapeutics: Research Funding; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Research Funding; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees; Cellectis: Research Funding; Pharmacyclics: Research Funding; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Research Funding; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Research Funding; Infinity: Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novimmune: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologioes: Research Funding; Genentech: Research Funding; Verastem: Research Funding; Servier: Honoraria, Membership on an entity's Board of Directors or advisory committees; BMS: Research Funding; ADC Therapeutics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Research Funding; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Verastem: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Research Funding; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; ADC Therapeutics: Research Funding; Pharmacyclics: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologioes: Research Funding; Pfizer: Research Funding; Cellectis: Research Funding; Verastem: Research Funding; BMS: Research Funding; Servier: Research Funding; Infinity: Research Funding; Astra Zeneca: Research Funding; Celgene: Research Funding; Genentech: Research Funding; Incyte: Research Funding; Abbvie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Honoraria, Membership on an entity's Board of Directors or advisory committees. Jabbour:Pfizer: Consultancy, Research Funding; Novartis: Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Abbvie: Research Funding. Andreeff:AstraZeneca: Research Funding. Konopleva:Stemline Therapeutics: Research Funding.