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BackgroundAcute myeloid leukemia (AML) stem cells (LSCs) are capable of surviving current standard chemotherapy and are the likely source of deadly, relapsed disease. While stem cell transplant serves as proof-of-principle that AML LSCs can be eliminated by the immune system, the translation of existing immunotherapies to AML has been met with limited success. Consequently, understanding and exploiting the unique immune-evasive mechanisms of AML LSCs is critical.MethodsAnalysis of stem cell datasets and primary patient samples revealed CD200 as a putative stem cell–specific immune checkpoint overexpressed in AML LSCs. Isogenic cell line models of CD200 expression were employed to characterize the interaction of CD200+AML with various immune cell subsets both in vitro and in peripheral blood mononuclear cell (PBMC)–humanized mouse models. CyTOF and RNA-sequencing were performed on humanized mice to identify novel mechanisms of CD200-mediated immunosuppression. To clinically translate these findings, we developed a fully humanized CD200 antibody (IgG1) that removed the immunosuppressive signal by blocking interaction with the CD200 receptor while also inducing a potent Fc-mediated response. Therapeutic efficacy of the CD200 antibody was evaluated using both humanized mice and patient-derived xenograft models.ResultsOur results demonstrate that CD200 is selectively overexpressed in AML LSCs and is broadly immunosuppressive by impairing cytokine secretion in both innate and adaptive immune cell subsets. In a PBMC-humanized mouse model, CD200+leukemia progressed rapidly, escaping elimination by T cells, compared with CD200−AML. T cells from mice with CD200+AML were characterized by an abundance of metabolically quiescent CD8+central and effector memory cells. Mechanistically, CD200 expression on AML cells significantly impaired OXPHOS metabolic activity in T cells from healthy donors. Importantly, CD200 antibody therapy could eliminate disease in the presence of graft-versus-leukemia in immune competent mice and could significantly improve the efficacy of low-intensity azacitidine/venetoclax chemotherapy in immunodeficient hosts.ConclusionsOverexpression of CD200 is a stem cell–specific marker that contributes to immunosuppression in AML by impairing effector cell metabolism and function. CD200 antibody therapy is capable of simultaneously reducing CD200-mediated suppression while also engaging macrophage activity. This study lays the groundwork for CD200-targeted therapeutic strategies to eliminate LSCs and prevent AML relapse.

The inferior cure rate of T-cell acute lymphoblastic leukemia (T-ALL) is associated with inherent drug resistance. The activating NOTCH1 gene mutations have been reported to cause chemoresistance at the stem cell level1. Direct NOTCH1 inhibition has failed in clinical trials due to a narrow therapeutic window but targeting key oncogenic and metabolic pathways downstream of mutated NOTCH1 may offer novel approaches. We previously reported that rapid transformation of thymocytes at the DN3 differentiation stage into preleukemic stem cells (pre-LSC) requires elevated Notch1 in addition to the presence of Scl/Lmo11. Notably, we showed that cellular metabolism of NOTCH1-mutated T-ALLs depends on Oxidative Phosphorylation (OxPhos) and that OxPhos inhibition using the complex I inhibitor IACS-010759 (OxPhos-i) is efficacious in NOTCH1-mutated T-ALL patient derived xenografts (PDXs)2. Here, we investigated the link between NOTCH1-mutated chemoresistance and OxPhos in pre-leukemic and leukemic cells, utilizing comprehensive molecular and functional assays. We hypothesized that chemotherapy aided by OxPhos-i overcomes chemoresistance, depletes LSCs and combats T-ALL. First, we analyzed the role of OxPhos in downstream Notch1 targets at the pre- and leukemic stage considering four stages of thymocyte differentiation (D1-D4), in a mouse model of human T-ALL1. Gene set enrichment analysis (GSEA) implicated increased expression of Notch1 target genes starting at DN1, and OxPhos target genes were the highest-ranked gene set at DN3. Next, activation of Notch1 by its ligand DL4 and inhibition of OxPhos reduced viability of pre-LSCs, indicating that ligand-dependent activation of Notch1 signaling upregulates the OxPhos pathway and sensitizes pre-LSCs to OxPhos-i. To clarify the role of Notch1 signaling, we examined the effect of IACS-010759 on pre-leukemic thymocytes harboring LMO1, SCL-LMO1, NOTCH1, LMO1-NOTCH1 and SCL-LMO1-NOTCH1 with and without DL4 stimulation. We found that in the absence of DL4, only thymocytes harboring the Notch1 oncogene responded to OxPhos-i, whereas all DL4-stimulated thymocytes responded regardless of Notch1 status (Fig. 1a). In addition, at the leukemic stage, we found elevation of the OxPhos pathway driven by oncogenic Notch1 when we compared transcriptomes of SCL-LMO1 induced T-ALL in the presence or absence of the NOTCH1 oncogene. In line with the murine T-ALL NOTCH1 model, we performed transcriptome analysis of two independent T-ALL patient cohorts prior to chemotherapy, COG TARGET ALL (n=263) and AALL1231 (n=75), comparing transcriptomes of NOTCH1-mutated vs NOTCH1-wt T-ALLs. We found co-segregation of NOTCH1 mutations with significant upregulation of OxPhos and TCA cycle genes and downregulation of apoptosis signaling. Aiming to reverse the NOTCH1-controlled anti-apoptotic program and chemoresistance, we next tested the combination of Vincristine, Dexamethasone and L-Asparaginase (VXL) with IACS-010759. When compared to vehicle, OxPhos-i or VXL alone, only the VXL-OxPhos-i treatment caused an energetic crisis indicated by decreased OCR and ECAR (Seahorse), which translated to a profound reduction of viability (CTG, flow cytometry) in T-ALL cell lines (n=9) and primary T-ALL samples (n=5). Additionally, the IACS-VXL combination in vivo resulted in pan-metabolic blockade, which caused metabolic shut-down and triggered early induction of apoptosis in leukemic cells in peripheral blood, spleen and bone marrow (Fig. 1b). Single cell Proteomic analysis (CyTOF) of spleen showed reduced expression of cell proliferation marker -ki67, c-myc, ERK and p38 proteins, and reduction in number of leukemic cells. Finally, this combination therapy resulted in reduced leukemia burden and extension of overall survival across all three aggressive NOTCH1-mutated T-ALL PDX models (p Disclosures Jabbour: Pfizer: Other: Advisory role, Research Funding; Genentech: Other: Advisory role, Research Funding; BMS: Other: Advisory role, Research Funding; Takeda: Other: Advisory role, Research Funding; Amgen: Other: Advisory role, Research Funding; Adaptive Biotechnologies: Other: Advisory role, Research Funding; AbbVie: Other: Advisory role, Research Funding. Teachey:Sobi: Consultancy; Amgen: Consultancy; Janssen: Consultancy; La Roche: Consultancy. Rezvani:Takeda: Other: Licensing agreement; GemoAb: Membership on an entity's Board of Directors or advisory committees; Adicet Bio: Membership on an entity's Board of Directors or advisory committees; Virogen: Membership on an entity's Board of Directors or advisory committees; Pharmacyclics: Other: Educational grant; Affimed: Other: Educational grant; Formula Pharma: Membership on an entity's Board of Directors or advisory committees. Andreeff:Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy; Daiichi-Sankyo; Breast Cancer Research Foundation; CPRIT; NIH/NCI; Amgen; AstraZeneca: Research Funding; Centre for Drug Research & Development; Cancer UK; NCI-CTEP; German Research Council; Leukemia Lymphoma Foundation (LLS); NCI-RDCRN (Rare Disease Clin Network); CLL Founcdation; BioLineRx; SentiBio; Aptose Biosciences, Inc: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding. Lorenzi:Precision Pathways: Consultancy. Konopleva:Calithera: Research Funding; Kisoji: Consultancy; AbbVie: Consultancy, Research Funding; Sanofi: Research Funding; Genentech: Consultancy, Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Cellectis: Research Funding; Rafael Pharmaceutical: Research Funding; Eli Lilly: Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; Agios: Research Funding; AstraZeneca: Research Funding; Ablynx: Research Funding; Forty-Seven: Consultancy, Research Funding; Amgen: Consultancy; Stemline Therapeutics: Consultancy, Research Funding; Ascentage: Research Funding.

Despite the clinical success of T-cell checkpoint blockade, most patients with cancer still fail to have durable responses to immunotherapy. The molecular mechanisms driving checkpoint blockade resistance, whether preexisting or evolved, remain unclear. To address this critical knowledge gap, we treated B16 melanoma with the combination of CTLA-4, PD-1, and PD-L1 blockade and a Flt3 ligand vaccine (≥75% curative), isolated tumors resistant to therapy, and serially passaged them in vivo with the same treatment regimen until they developed complete resistance. Using gene expression analysis and immunogenomics, we determined the adaptations associated with this resistance phenotype. Checkpoint resistance coincided with acquisition of a “hypermetabolic” phenotype characterized by coordinated upregulation of the glycolytic, oxidoreductase, and mitochondrial oxidative phosphorylation pathways. These resistant tumors flourished under hypoxic conditions, whereas metabolically starved T cells lost glycolytic potential, effector function, and the ability to expand in response to immunotherapy. Furthermore, we found that checkpoint-resistant versus -sensitive tumors could be separated by noninvasive MRI imaging based solely on their metabolic state. In a cohort of patients with melanoma resistant to both CTLA-4 and PD-1 blockade, we observed upregulation of pathways indicative of a similar hypermetabolic state. Together, these data indicated that melanoma can evade T-cell checkpoint blockade immunotherapy by adapting a hypermetabolic phenotype.

Metabolic reprogramming is recognized as one of the key hallmarks in acquiring aggressive phenotype and chemoresistance in solid tumors and hematologic malignancies. We have previously demonstrated that T-ALL are characterized by significant dependency on oxidative phosphorylation (OxPhos) with ability to utilize glutamine either in oxidative or reductive directions of TCA cycle, when mitochondria are blocked by Complex I Inhibitor (Baran N, et al. ASH 2020). To survive upon Complex I blockade leukemic cells require functional monocarboxylate transporter MCT1, that enables excretion of lactate and permissive pyruvate flux (Fig.1 a). Here we show that metabolic intervention utilizing OxPhos blockade can be potentiated by targeting MCT1 transporter and propose a novel metabolic synthetic lethality that could be exploited to eradicate T-ALL and other OxPhos-dependent malignancies. We first demonstrated that Complex I inhibition leads to increased MCT1 expression; on the contrary, MCT1 transporter blockade forces cells to increase OxPhos. In turn, the combinatorial therapy with Complex I inhibitor (IACS-010759) and MCT1 inhibitor (AZD3965) causes loss of ATP content (Fig. 1b), significant reduction of cell number and massive induction of apoptosis. Mechanistically, the combination treatment further reduced oxygen consumption rate (OCR) (Fig. 1c) and increased extracellular acidification rate, as measured by Seahorse. In concert with those results, dual inhibition led to TCA blockade, accumulation of intracellular lactate and depletion of glutamine, cystathionine and glutathione, indicating severe disruption of redox balance as measured by mass spectrometry and confirmed by significant accumulation of intracellular and mitochondrial reactive oxygen species (ROS) (Fig. 1d), loss of mitochondrial membrane potential (ΔΨ) (Fig. 1e) and subsequent mitochondria swelling. RNAseq data showed simultaneous upregulation of glycolysis and glutathione-related processes as possible mechanisms of metabolic compensation, yet strong upregulation of genes regulating apoptosis related to mitochondria dysfunction (Fig. 1f). Real-time hyperpolarized MRI based metabolic imaging studies with [1-13C]-pyruvate in patient-derived xenografts in vivo revealed significant decrease of lactate-to-pyruvate ratio in mice treated with AZD3965 or IACS-010759 alone, and in mice treated with drug combination. [13C]-Glucose isotope tracing analysis in patient-derived xenografts in vivo revealed an increased intracellular trapping of lactate as a marker of treatment effectiveness in mice subjected to dual blockade. While MCT1 inhibition induced only moderate reduction of leukemia growth in vitro and tumor burden in vivo, combination with IACS-010759 depleted significantly both, circulating and marrow/spleen/liver resident leukemia cells. Mechanistically, inhibition of MCT1 by AZD3965 therapy in leukemia-bearing mice led to lactate accumulation, OCR increase, moderate ROS production and mitochondrial membrane hyperpolarization, while Complex I blockade resulted in upregulation of MCT-1, reduction of OCR, lactate production and increase of ROS ; consequently, combinatorial therapy caused complete mitochondria shut-down and drastic inhibition of tumor growth both in vitro and in vivo in two xenografts models and led to significant extension of overall survival (p Figure 1 Figure 1. Disclosures Skwarska: Halilovich E, Wang Y, Morris E, Konopleva M, Skwarska A.: Patents & Royalties: Combination of a MCL-1 inhibitor and midostaurin, uses and pharmaceutical composition thereof.. Konopleva: Reata Pharmaceuticals: Current holder of stock options in a privately-held company, Patents & Royalties: intellectual property rights; Rafael Pharmaceuticals: Other: grant support, Research Funding; Stemline Therapeutics: Research Funding; Eli Lilly: Patents & Royalties: intellectual property rights, Research Funding; Ascentage: Other: grant support, Research Funding; Genentech: Consultancy, Honoraria, Other: grant support, Research Funding; Ablynx: Other: grant support, Research Funding; AstraZeneca: Other: grant support, Research Funding; AbbVie: Consultancy, Honoraria, Other: Grant Support, Research Funding; Novartis: Other: research funding pending, Patents & Royalties: intellectual property rights; Cellectis: Other: grant support; Sanofi: Other: grant support, Research Funding; KisoJi: Research Funding; Calithera: Other: grant support, Research Funding; Forty Seven: Other: grant support, Research Funding; Agios: Other: grant support, Research Funding; F. Hoffmann-La Roche: Consultancy, Honoraria, Other: grant support.

Background: Acute myeloid leukemia (AML) stem cells (LSC), the likely source of relapsed disease, are capable of surviving current standard chemotherapy. Therefore, novel therapeutic approaches specifically engineered to eradicate LSCs are critical for curing AML. We previously introduced a novel bioinformatics approach that harnessed publically available AML gene expression datasets and identified CD200 as significantly over-expressed in LSCs when compared to paired blast cells, as well as when compared to their normal hematopoietic stem cell (HSC) counterparts (Fig 1A; Herbrich et al Blood. 2018; 130:3962). CD200 can identify AML cells with LSC activity in vivo (Ho et al Blood. 2016; 128:1705). Functionally, CD200 has been shown to have an immunosuppressive effect on macrophages (Hoek et al Science. 2000; 290:1768) and NK cells (Coles et al Leukemia. 2012; 26:2148), and correlates with a high prevalence of FOXP3+ regulatory T cells (Coles et al Leukemia. 2012; 26:2146). Additionally, CD200 has been implicated as a poor prognostic marker in AML (Damiani et al Oncotarget. 2015; 6:30212). To date, we have screened 40 primary AML patient samples by flow cytometry, 95% of which are positive for CD200. Methods: To study the functional role of CD200 in AML, we generated a CD200 overexpression model in the human OCI-AML3 cell line (with no basal expression) and characterized changes in proliferation, survival, and gene expression. To examine the immune function of CD200 in AML in vitro, we performed a series of mixed lymphocyte reactions with isolated effector immune cells and target isogenic AML cell lines to assess immune cell-mediated apoptosis, proliferation, and cytokine secretion. To understand the contribution of CD200 immune protection in a physiological setting, we developed a peripheral blood mononuclear cell (PBMC)-humanized mouse in which we tracked the engraftment and overall survival of the CD200+/- OCI-AML3 cells. Lastly, the utility of CD200-blockade using a fully humanized anti-CD200 monoclonal antibody (CD200-IgG1) was evaluated both in vitro and in vivo. Results: In vitro, CD200+ AML significantly inhibited the secretion of inflammatory cytokines and cytotoxic enzymes from healthy PBMCs; a phenomenon that could be largely reversed by blocking the CD200/CD200R interaction with the CD200 antibody (Fig 1B). In vivo, OCI-AML3 CD200+/- cells showed no difference in engraftment, progression, and overall survival in immunodeficient NSG mice (Fig 1C). However, when mice were humanized using healthy PBMCs, CD200+ leukemia progressed rapidly, escaping T cell-mediated elimination, compared to CD200- control leukemic cells (Fig 1D). Cytokine production in PBMC-humanized mice was significantly compromised in those with CD200-expressing leukemia. Transcriptome analysis revealed that T cells from humanized mice exposed to CD200 expressing disease were metabolically quiescent. In humanized mice, CD200-IgG1 therapy eliminated CD200+ AML disease (Fig 1E). The novel CD200-IgG1 antibody also induced potent, specific NK cell-mediated antibody dependent cellular cytotoxicity (ADCC) and macrophage-mediated antibody dependent cellular phagocytosis (ADCP; Fig 1F). Conclusion: We have identified CD200 as a putative stem cell-specific immunomodulatory target that aids in establishing an immunosuppressive microenvironment by significantly suppressing cytokine secretion in response to AML. In a PBMC-humanized mouse model, the presence of cell-surface CD200 was sufficient to protect AML cells from immune-mediated clearance and could be reversed using a blocking anti-CD200 mAb. These findings indicate a utility of CD200 as a novel immune checkpoint target for the development of therapeutic strategies in AML. Disclosures Konopleva: Calithera: Research Funding; Kisoji: Consultancy; AbbVie: Consultancy, Research Funding; Reata Pharmaceutical Inc.;: Patents & Royalties: patents and royalties with patent US 7,795,305 B2 on CDDO-compounds and combination therapies, licensed to Reata Pharmaceutical; Ablynx: Research Funding; Genentech: Consultancy, Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Eli Lilly: Research Funding; Cellectis: Research Funding; Amgen: Consultancy; Stemline Therapeutics: Consultancy, Research Funding; AstraZeneca: Research Funding; Sanofi: Research Funding; Agios: Research Funding; Forty-Seven: Consultancy, Research Funding; Rafael Pharmaceutical: Research Funding; Ascentage: Research Funding.

// Rodrigo Jacamo 1 , R. Eric Davis 2 , Xiaoyang Ling 3 , Sonali Sonnylal 1 , Zhiqiang Wang 2 , Wencai Ma 2 , Min Zhang 2 , Peter Ruvolo 1 , Vivian Ruvolo 1 , Rui-Yu Wang 1 , Teresa McQueen 1 , Scott Lowe 4 , Johannes Zuber 5 , Steven M. Kornblau 1 , Marina Konopleva 1 and Michael Andreeff 1 1 Department of Leukemia, Section of Molecular Hematology and Therapy, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 2 Department of Lymphoma and Myeloma, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 3 Department of Neurosurgery, The University of Texas MD Anderson Cancer Center, Houston, TX, USA 4 Department of Cancer Biology and Genetics, Memorial Sloan Kettering Cancer Center, New York, NY, USA 5 Research Institute of Molecular Pathology, Vienna, Austria Correspondence to: Michael Andreeff, email: // Keywords : AML, microenvironment, GEP, stroma, genotype Received : September 23, 2016 Accepted : June 03, 2017 Published : July 06, 2017 Abstract The genetic heterogeneity of acute myeloid leukemia (AML) and the variable responses of individual patients to therapy suggest that different AML genotypes may influence the bone marrow (BM) microenvironment in different ways. We performed gene expression profiling of bone marrow mesenchymal stromal cells (BM-MSC) isolated from normal C57BL/6 mice or mice inoculated with syngeneic murine leukemia cells carrying different human AML genotypes, developed in mice with Trp53 wild-type or nullgenetic backgrounds. We identified a set of genes whose expression in BM-MSC was modulated by all four AML genotypes tested. In addition, there were sets of differentially-expressed genes in AML-exposed BM-MSC that were unique to the particular AML genotype or Trp53 status. Our findings support the hypothesis that leukemia cells alter the transcriptome of surrounding BM stromal cells, in both common and genotype-specific ways. These changes are likely to be advantageous to AML cells, affecting disease progression and response to chemotherapy, and suggest opportunities for stroma-targeting therapy, including those based on AML genotype.

Targeting B-cell receptor (BCR) signaling is a successful therapeutic strategy in mature B-cell malignancies. Precursor BCR (pre-BCR) signaling, which is critical during normal B lymphopoiesis, also plays an important role in pre-BCR+ B cell acute lymphoblastic leukemia (B-ALL). Here, we investigated the activity and mechanism of action of the BTK inhibitor ibrutinib in preclinical models of B-ALL. Pre-BCR+ ALL cells were exquisitely sensitive to ibrutinib at therapeutically relevant drug concentrations. In pre-BCR+ ALL, ibrutinib thwarted autonomous and induced pre-BCR signaling, resulting in deactivation of PI3K/Akt signaling. Ibrutinib modulated the expression of pre-BCR regulators (PTPN6, CD22, CD72, and PKCβ) and substantially reduced BCL6 levels. Ibrutinib inhibited ALL cell migration toward CXCL12 and beneath marrow stromal cells and reduced CD44 expression. CRISPR-Cas9 gene editing revealed that both BTK and B lymphocyte kinase (BLK) are relevant targets of ibrutinib in pre-BCR+ ALL. Consequently, in mouse xenograft models of pre-BCR+ ALL, ibrutinib treatment significantly prolonged survival. Combination treatment of ibrutinib with dexamethasone or vincristine demonstrated synergistic activity against pre-BCR+ ALL. These data corroborate ibrutinib as a promising targeted agent for pre-BCR+ ALL and highlight the importance of ibrutinib effects on alternative kinase targets.

Immune checkpoint blockade represents a major breakthrough in cancer therapy; however, responses are not universal. Genomic and immune features in pretreatment tumor biopsies have been reported to correlate with response in patients with melanoma and other cancers, but robust biomarkers have not been identified. We studied a cohort of patients with metastatic melanoma initially treated with cytotoxic T-lymphocyte–associated antigen-4 (CTLA4) blockade (n = 53) followed by programmed death-1 (PD-1) blockade at progression (n = 46), and analyzed immune signatures in longitudinal tissue samples collected at multiple time points during therapy. In this study, we demonstrate that adaptive immune signatures in tumor biopsy samples obtained early during the course of treatment are highly predictive of response to immune checkpoint blockade and also demonstrate differential effects on the tumor microenvironment induced by CTLA4 and PD-1 blockade. Importantly, potential mechanisms of therapeutic resistance to immune checkpoint blockade were also identified. Significance: These studies demonstrate that adaptive immune signatures in early on-treatment tumor biopsies are predictive of response to checkpoint blockade and yield insight into mechanisms of therapeutic resistance. These concepts have far-reaching implications in this age of precision medicine and should be explored in immune checkpoint blockade treatment across cancer types. Cancer Discov; 6(8); 827–37. ©2016 AACR. See related commentary by Teng et al., p. 818. This article is highlighted in the In This Issue feature, p. 803

Loss of IL-15 expression by colon tumors strongly correlates with classification as microsatellite stable, decreased tumor infiltrating lymphocytes (TILs), increased metastasis, and poor responses to immunotherapy. To better understand how IL-15 expression regulates immune cells in the tumor microenvironment (TME) and identify the importance of IL-15 expressed by tumor cells, we developed a mouse model system to examine this by generating MC-38 tumor cells deficient in IL-15 using CRISPR/Cas9 system. After one round of IL-15 deletion, MC-38 cells that lack one IL-15 allele (i.e IL-15+/− MC-38 cells) were identified and expressed decreased levels of soluble IL-15 complexes. Surprisingly, deletion of one IL-15 allele was sufficient to affect tumor growth as IL-15+/− MC-38 tumors grew faster than Wt MC-38 tumors. IL-15+/− MC-38 tumors had decreased CD8 and NK TILs and increased CD11b+Ly6G+ and CD11b+Ly6ChiLy6G− myeloid cells than Wt tumors. Gene expression analysis of myeloid cells showed that blocking IL-15 in tumors increased expression of CD206, ARG1, and TDO2 and decreased IL-12β and IL-6. A second round of deletion led to complete deletion of IL-15 in MC-38 cells (i.e. IL-15−/− MC-38) and upon implantation developed tumors with further decreases in CD8 and NK TILs. In mice lacking IL-15Rα in the intestinal epithelium, AOM/DSS-induced colon tumors also harbored decreased numbers of CD8 TILs. These results demonstrate that even partially decreasing levels of IL-15 in the TME negatively impacts the numbers of CD8 and NK TILs and skews myeloid cells towards a pro-tumor landscape. Overall, these models that can be used to identify the mechanisms contributing to the poor therapeutic responses observed in human colon carcinomas.

In this issue of Blood, Boudesco et al show that heat shock protein HSP110 (HSPH1) stabilizes wild-type and mutant MYD88, facilitating NF-κB activation in diffuse large B-cell lymphoma (DLBCL).1

Introduction. The combination of rituximab and lenalidomide (R2) is active in patients with untreated indolent lymphoma. Recent randomized trials (RELEVANCE) have demonstrated similar efficacy when compared to standard chemo-immunotherapy backbones. Long term follow up of patients receiving R2 as well as predictors of long term remission and survival have yet to be published. Methods. We prospectively evaluated patients with low grade advanced stage FL who received R2 as initial treatment at our institution between 07/2008 and 10/2014. Lenalidomide was given at 20 mg (day 1-21, in a 28 day cycle) for 6 cycles with rituximab monthly. Lenalidomide starting dose was 10 mg if baseline creatinine clearance was < 60 mL/min. Patients with an objective response continued with 10-20 mg of lenalidomide with rituximab for up to 12 more cycles. Response was evaluated according to 2014 Lugano criteria. Results. One-hundred and one patients were included in the analysis, baseline characteristics are shown in the Table. Median number of provided cycles was 7 (range, 1-20). Median dose of lenalidomide was 20 mg (range, 5-20 mg), and 29 (29%) patients required a dose reduction. Fifty-six (55%) patients experienced grade 3-4 treatment-related toxicities, the most common (> 5%) being neutropenia (39%), skin rash (20%), myalgia (16%) and fatigue (16%). Seven (7%) patients discontinued treatment before completion, after a median time of 4 months (range, 1-10 months): 4 because of toxicity (arterial thrombosis in 2, respiratory failure in 1, and skin rash in 1), and 3 because of progression. Ninety-eight patients were evaluable for response, while 3 patients discontinued treatment because of toxicity before first response assessment. Overall response rate was 98%, CR rate 90% (both achieved after a median of 6 months [range, 3-22 months]), and CR rate at 30 months (CR30) was 80%. Only female sex associated with a higher CR rate (96% vs 83%, p=0.05), while no baseline characteristic associated with CR30 rate. After a median follow-up of 88 months (95% confidence interval, 84-92 months), 31 (31%) patients progressed and/or died, 7-year progression-free survival (PFS) was 63%, and 13% of patients had a PFS < 24 months (PFS24). Failure to achieve CR was the only factor associated with significantly decreased PFS (10 months vs not reached, p At most recent follow-up, transformation was reported in 3 (3%) patients, after 30, 32 and 42 months, respectively. Two (2%) patients have died, 1 of unrelated comorbid health conditions, 1 of progressive disease, and 7-year overall survival was 98%. Second cancers (excluding transformation) were diagnosed in 8 (8%) patients, after a median of 55 months (range, 3-105 months). These included: breast adenocarcinoma (2), melanoma (2), pancreatic adenocarcinoma (1), esophageal adenocarcinoma (1), and therapy-related acute myeloid leukemia. Discussion. Long-term follow-up show very favorable outcomes for patients with advanced stage FL receiving R2 as initial treatment, independent of traditional prognostic factors relevant to patients treated with chemoimmunotherapy, including FLIPI and FLIPI-2 score. Combination strategies, aimed at increasing depth of response to R2, may further improve outcomes observed with this regimen. Table. Disclosures Nastoupil: Bayer: Honoraria; Genentech, Inc.: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Honoraria, Research Funding; Novartis: Honoraria; TG Therapeutics: Honoraria, Research Funding; Spectrum: Honoraria. Westin:Janssen: Other: Advisory Board, Research Funding; Unum: Research Funding; Curis: Other: Advisory Board, Research Funding; 47 Inc: Research Funding; Genentech: Other: Advisory Board, Research Funding; Juno: Other: Advisory Board; Celgene: Other: Advisory Board, Research Funding; MorphoSys: Other: Advisory Board; Novartis: Other: Advisory Board, Research Funding; Kite: Other: Advisory Board, Research Funding. Wang:AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; MoreHealth: Consultancy, Equity Ownership; Acerta Pharma: Consultancy, Research Funding; BioInvent: Consultancy, Research Funding; Pharmacyclics: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Juno Therapeutics: Research Funding; Dava Oncology: Honoraria; Celgene: Honoraria, Research Funding; Aviara: Research Funding; Kite Pharma: Consultancy, Research Funding; Guidepoint Global: Consultancy; VelosBio: Research Funding; Loxo Oncology: Research Funding. Neelapu:Pfizer: Consultancy; Precision Biosciences: Consultancy; Merck: Consultancy, Research Funding; Celgene: Consultancy, Research Funding; Allogene: Consultancy; Novartis: Consultancy; BMS: Research Funding; Kite, a Gilead Company: Consultancy, Research Funding; Cellectis: Research Funding; Acerta: Research Funding; Karus: Research Funding; Poseida: Research Funding; Incyte: Consultancy; Cell Medica: Consultancy; Unum Therapeutics: Consultancy, Research Funding. Fowler:Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; ABBVIE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding. OffLabel Disclosure: lenalidomide and rituximab are not yet FDA-approved as frontline treatment for patients with FL

Introduction: FL, the most common indolent non-Hodgkin lymphoma, is characterized by a defective immune microenvironment that suppresses normal T-cell and natural-killer (NK)-cell activity. The clinical course is often depicted by high initial response rates coupled with a prolonged natural history and repeated relapses with most patients (pts) succumbing to their disease. Effective, well tolerated therapies are desirable. Obinutuzumab (O) is a humanized, type II anti-CD20 monoclonal antibody glycoengineered for enhanced antibody-dependent cellular cytotoxicity (ADCC). Lenalidomide (len) is an immunomodulatory agent that binds the cereblon E3 ubiquitin ligase complex resulting in recruitment, ubiquitination, and degradation of transcription factors Aiolos and Ikaros resulting in T-cell and NK-cell activation. Therefore, combining O with len is anticipated to be synergistic in augmenting the innate and adaptive immune response in FL. The combination has been shown to be well tolerated and effective in relapsed FL (Fowler ICML 2017). Therefore, we sought to explore the efficacy and safety of O-len in previously untreated, high tumor burden FL. Methods: We conducted as single-center, phase 2 study in previously untreated, stage II, III, or IV, high tumor burden (defined by GELF) FL (grade 1, 2 or 3A). Pts received 1000mg of O on days 1, 8, and 15 of cycle 1, day 1 of cycles 2-6, and day 1 of even numbered cycles, cycle 8-30. Cycle length was 28 days. Len was administered as 20mg on days 1-21 of cycles 1-6. Pts in a complete response (CR) after 6 cycles received reduced dose len (10mg on days 1-21) for cycles 7-18. Among pts in a partial response (PR) after 6 cycles, len was continued at 20mg for the next 3-6 cycles or until CR, whichever occurred first, len was then dose reduced to 10mg on days 1-21 for the remainder of 18 cycles. The primary endpoint was progression-free survival (PFS) at 2 years (according to Lugano 2014 criteria). Secondary endpoints included: safety, CR, PR, overall response (ORR), and overall survival (OS). Results: 90 pts with high tumor burden FL were enrolled. Median age was 58 years (range 33-84), 52% (N=47) were male, 67 (74%) had an ECOG performance status of 0, 9 (10%) had stage II, 23 (26%) stage III, and 58 (64%) had stage IV disease. The majority had grade 1/2 FL (80%). Twenty-one percent had low risk FLIPI scores, 37% intermediate risk, and 42% were high risk. With a median follow-up of 22 months (range 1-30 months), the 2-year PFS estimate is 96% (95% CI 92-100%) with only 2 pts experiencing progression to date. The ORR is 98% (85 CR, 1 PR), 92% achieved a CR at the first response assessment (cycle 4, day 1). Correlative studies are underway including serial circulating tumor DNA measurements. No deaths have been observed to date. Eleven pts (12%) discontinued therapy as a result of an adverse event (AE), upper respiratory infection was the most common reason (N=5). Other reasons included bradycardia with sick sinus syndrome, urinary tract infection, constipation, abdominal pain, fatigue, foot neuroma (N=1 for each instance). The most common grade 3 or higher AEs include neutropenia (16%, grade 3 N=5, grade 4 N= 9), rash (10%), lung infection (4%), neutropenic fever (1%). Conclusions: O-Len was associated with very high CR rates and 2-year PFS estimates in untreated, high tumor burden FL. The toxicity profile was manageable. Further study of this effective, immune therapy approach in untreated FL is warranted. Figure Disclosures Nastoupil: Bayer: Honoraria; Celgene: Honoraria, Research Funding; Genentech, Inc.: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Honoraria, Research Funding; Novartis: Honoraria; TG Therapeutics: Honoraria, Research Funding; Spectrum: Honoraria. Westin:Genentech: Other: Advisory Board, Research Funding; Unum: Research Funding; Novartis: Other: Advisory Board, Research Funding; Janssen: Other: Advisory Board, Research Funding; Juno: Other: Advisory Board; 47 Inc: Research Funding; MorphoSys: Other: Advisory Board; Kite: Other: Advisory Board, Research Funding; Curis: Other: Advisory Board, Research Funding; Celgene: Other: Advisory Board, Research Funding. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding. Wang:Pharmacyclics: Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; Acerta Pharma: Consultancy, Research Funding; Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; MoreHealth: Consultancy, Equity Ownership; Kite Pharma: Consultancy, Research Funding; Guidepoint Global: Consultancy; BioInvent: Consultancy, Research Funding; VelosBio: Research Funding; Loxo Oncology: Research Funding; Celgene: Honoraria, Research Funding; Juno Therapeutics: Research Funding; Aviara: Research Funding; Dava Oncology: Honoraria. Neelapu:Acerta: Research Funding; Celgene: Consultancy, Research Funding; Kite, a Gilead Company: Consultancy, Research Funding; Allogene: Consultancy; Cell Medica: Consultancy; Unum Therapeutics: Consultancy, Research Funding; Pfizer: Consultancy; Poseida: Research Funding; Karus: Research Funding; Novartis: Consultancy; Incyte: Consultancy; BMS: Research Funding; Cellectis: Research Funding; Precision Biosciences: Consultancy; Merck: Consultancy, Research Funding. Fowler:ABBVIE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Pharmaceuticals Corporation: Consultancy. OffLabel Disclosure: Lenalidomide in untreated follicular lymphoma

Background: Diffuse Large B-cell Lymphoma (DLBCL), the most common lymphoid cancer, is classified by the cell of origin into the germinal and non-germinal center (non-GCB) subtypes. The non-GCB subtype is associated with inferior outcomes with standard therapies, but the BTK inhibitor ibrutinib (I) and immunomodulatory agent lenalidomide (L) have moderate activity as single agents and result in synthetic lethality when combined in non-GCB DLBCL models (Yang, Cancer Cell 2012). When added to chemotherapy for DLBCL as single agents, neither I nor L have significantly improved outcomes over chemotherapy alone as they only result in synthetic lethality with each other. In relapsed non-GCB DLBCL, a phase Ib trial of rituximab (R), L and I resulted in an overall response rate (ORR) of 65% and median duration of response of 15.9 months (Goy, Blood 2019). Both I and L are also immunomodulatory, shifting from a tumor-mediated immune anergy to an anti-tumor immune response. Methods: We conducted an investigator initiated, open-label, single-arm phase 2 study (Smart Start, NCT02636322) of RLI alone in a 2 cycle lead in followed by RLI combined with standard chemotherapy for 6 cycles in newly diagnosed non-GCB DLBCL patients. Patients were eligible if they had newly diagnosed non-GCB DLBCL (Hans method), adequate organ function and performance status, and were aged 18y or greater. The primary objectives were 1A: to determine the ORR of 2 cycles of RLI, and 1B: to determine the complete response rate (CRR) after RLI-chemotherapy (CHOP or dose adjusted EPOCH per treating MD choice). Therapy consisted of R 375 mg/m2 IV day 1, ibrutinib 560 mg oral daily, and lenalidomide 25 mg oral days 1-10 of a 21 day cycle for 2 cycles, followed by 6 additional cycles of RLI with chemotherapy. All patients were required to receive growth factor support, and prophylaxis for venous thromboembolism and pneumocystis. Responses were determined with PET/CT as per the Lugano criteria. Results: The protocol accrued 60 patients from May 2016 - February 2019, with 58 patients evaluable for disease response (2 withdrew consent prior to restaging). The median age was 63.5 years (range: 29-83), 28% were >= 70 years, and 50% were female. 51.7% had poor risk R-IPI, 65% had advanced stage, 77% had a Ki-67 of >= 80%, and 54% of patients with available tissue were "double expressor" (DE, MYC and BCL2 overexpression via IHC). The median time from diagnosis to therapy was 24 days. The chemotherapy received was CHOP in 43%, (n=25), dose adjusted EPOCH in 55% (n = 32), and none in 2% (n=1). Over 90% of planned ibrutinib and lenalidomide was able to be administered. 13 patients received less than 6 cycles of chemotherapy (C0 = 1, C4 = 4, C5 = 8) due to toxicity, treating physician preference, or patient refusal. Adverse events were generally similar to what is expected with chemotherapy, with the exception of rash in 32% (9% grade 3) and CNS aspergillosis (n = 1). 2 patients suffered grade 5 events (CNS aspergillosis, clostridium difficile colitis). The ORR for 2 cycles of RLI alone was 86% (n=50), the CRR was 36% (n=21), and patients achieving a PR had an 81% median tumor reduction from baseline. The end of therapy ORR is 100% (CR: 95%, PR 5%), with none of the PR patients having relapsed to date without further therapy. The median follow-up at abstract submission is 16 months (1 - 33.5m), with 1 year PFS estimate of 92.5% and OS estimate of 96.5%. Response and survival were not different based upon chemotherapy selected, baseline clinical or pathological variables including DE status or Ki-67%, or number of cycles of therapy received. Correlative studies, including circulating tumor DNA assessment at baseline, after 2 cycles of RLI, and at the end of therapy and beyond are ongoing and will be presented at the meeting. Conclusions: The Smart Start trial demonstrates the combination of rituximab 375 mg/m2 IV, ibrutinib 560 mg oral daily, and lenalidomide 25mg oral d1-10 prior to and with chemotherapy results in impressive response rates and survival in newly diagnosed non-GCB DLBCL compared with historical outcomes. Established adverse prognostic variables including non-GCB, high Ki-67%, and double expression of MYC and BCL2 had similar outcomes with other patients with RLI-based therapy. Further studies are planned to expand the lead-in phase with more targeted agents and number of cycles, and to administer fewer cycles of chemotherapy for patients achieving a CR with a targeted therapy lead-in. Figure Disclosures Westin: Curis: Other: Advisory Board, Research Funding; Celgene: Other: Advisory Board, Research Funding; Janssen: Other: Advisory Board, Research Funding; Novartis: Other: Advisory Board, Research Funding; Genentech: Other: Advisory Board, Research Funding; 47 Inc: Research Funding; Juno: Other: Advisory Board; Unum: Research Funding; MorphoSys: Other: Advisory Board; Kite: Other: Advisory Board, Research Funding. Nastoupil:Bayer: Honoraria; Celgene: Honoraria, Research Funding; Gilead: Honoraria; Janssen: Honoraria, Research Funding; Spectrum: Honoraria; TG Therapeutics: Honoraria, Research Funding; Novartis: Honoraria; Genentech, Inc.: Honoraria, Research Funding. Oki:Jazz: Employment. Parmar:Cellenkos Inc.: Equity Ownership, Membership on an entity's Board of Directors or advisory committees, Research Funding. Chuang:Sage Evidence-based Medicine & Practice Institute: Consultancy. Neelapu:Celgene: Consultancy, Research Funding; Unum Therapeutics: Consultancy, Research Funding; BMS: Research Funding; Kite, a Gilead Company: Consultancy, Research Funding; Cellectis: Research Funding; Karus: Research Funding; Novartis: Consultancy; Merck: Consultancy, Research Funding; Acerta: Research Funding; Precision Biosciences: Consultancy; Cell Medica: Consultancy; Allogene: Consultancy; Incyte: Consultancy; Poseida: Research Funding; Pfizer: Consultancy. OffLabel Disclosure: Ibrutinib and lenalidomide are not yet indicated for DLBCL, we will describe our trial

Cellular stress response has dual aspects; cell-protective or lethal. Mitochondria have their unique organellar response termed "mitochondrial unfolded protein response (UPRmt)" induced by damaged mitochondrial (mt) matrix proteins. While recent discoveries have successfully targeted BCL2, a regulator of mt integrity in acute myeloid leukemia (AML), the significance of UPRmt is unknown. We hypothesized that priming UPRmt towards cell death would be a novel therapeutic strategy for AML. UPRmt is generally induced by dysregulation of mt protein pools. Therefore, to test if UPRmt signaling is also operational in AML cells, we selected classical or putative UPRmt inducers; the mt translation inhibitors tetracycline and tigecycline, the mt protein transport inhibitor MitoBlock6, and the mtDNA damaging agent ethidium bromide. In OCI-AML3 and HL60 cells, these agents indeed induced the transcription factor ATF5, which was reported as a central inducer of UPRmt, and its targets (e.g., LonP, HSPA9), triggering apoptosis in AML cells. In addition, we here report imipridones (ONC201 and ONC212), the activators of mt protein degradation, as novel UPRmt inducers. We recently reported that imipridones non-covalently bind the mt protease ClpP and allosterically activate it. They induced prominent apoptosis in primary AML progenitor and leukemia initiating cells (LICs) in vitro and in vivo, but not in normal bone marrow cells, following "mitochondrial proteolysis" with reduction of selective mt matrix proteins (e.g., SDHB, NDUFA12) and resultant inhibition of oxidative phosphorylation (Oxphos) (Ishizawa, Zarabi et al, Cancer Cell 2019). We then postulated that dysregulation of mt protein pools by mitochondrial proteolysis can also induce UPRmt. Indeed, our gene expression profiles of ONC201-treated Z138 and Jeko-1 cells were highly enriched for previously published UPRmt gene signatures, and UPRmt effectors were induced also in AML cells. Of potentially high clinical significance is the finding of synergistic anti-leukemia effects of imipridones when combined with the selective BCL2 inhibitor venetoclax, in vitro and in vivo (Ishizawa et al. Science Signaling 2016, and Nii et al. Blood 2019). However, its underlying molecular mechanism is unclear. Since BCL2 is reported to be induced by UPRmt, we hypothesized that BCL2 is critical for the ClpP-mediated UPRmt to have the cell protective effects, contrary to lethal effects, as dual aspects of stress response. We utilized the tetracycline-inducible system of an activated mutant (Y118A) form of ClpP in OCI-AML3 cells, and demonstrated that venetoclax treatment sensitizes OCI-AML3 cells to genetic activation of ClpP towards apoptosis. Furthermore, other UPRmt inducers (tetracycline, tigecycline, and MitoBlock6) in combination with venetoclax also synergistically induced apoptosis in AML cells, suggesting that BCL2 inhibition and UPRmt induction generally exerts synergistic anti-leukemia effects. We next focused on the enhanced effect observed for the combination of imipridones with venetoclax as compared to other UPRmt inducers, searching for other targets that could further enhance the synergy. We then hypothesized that the synergism between ClpP activation and BCL2 inhibition involves SDHB, a respiratory chain complex II subunit degraded by activated ClpP but not targeted by any of other UPRmt inducers. Consistently, SDHB knockdown sensitized OCI-AML3 cells to venetoclax-induced apoptosis, indicating that SDHB reduction and UPRmt by ClpP activation concomitantly enhance the cell lethality by BCL2 inhibition. Collectively, UPRmt is a new potential therapeutic target for AML, which significantly enhances the cell death effects of BCL2 inhibition on AML cells. In particular, ClpP activation induces UPRmt and, concomitantly, downregulates SDHB, thus targeting the respiratory chain complex II, which results in improved synergistic leukemia cell apoptosis when combined with BCL2 inhibition. Oxphos is also a hallmark of drug resistant AML stem cells, which supports the notion that Oxphos inhibition by this combination targets LICs. Based on promising preclinical anti-tumor efficacy, ONC201 as a single agent is being evaluated in early phase clinical trials, showing clinical responses in AML and midline gliomas. A clinical trial testing the combinatorial strategy of targeting ClpP and Bcl-2 is under development. Disclosures Borthakur: Novartis: Research Funding; NKarta: Consultancy; Eisai: Research Funding; Oncoceutics: Research Funding; BioLine Rx: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cyclacel: Research Funding; Strategia Therapeutics: Research Funding; Eli Lilly and Co.: Research Funding; Arvinas: Research Funding; Merck: Research Funding; AstraZeneca: Research Funding; PTC Therapeutics: Consultancy; Agensys: Research Funding; Argenx: Membership on an entity's Board of Directors or advisory committees; FTC Therapeutics: Membership on an entity's Board of Directors or advisory committees; GSK: Research Funding; Incyte: Research Funding; Janssen: Research Funding; AbbVie: Research Funding; BMS: Research Funding; Oncoceutics, Inc.: Research Funding; Bayer Healthcare AG: Research Funding; BioTheryX: Membership on an entity's Board of Directors or advisory committees; Tetralogic Pharmaceuticals: Research Funding; Cantargia AB: Research Funding; Polaris: Research Funding; Xbiotech USA: Research Funding. Stogniew:Oncoceutics, Inc.: Employment. Oster:Oncoceutics, Inc.: Employment. Kantarjian:BMS: Research Funding; AbbVie: Honoraria, Research Funding; Ariad: Research Funding; Amgen: Honoraria, Research Funding; Jazz Pharma: Research Funding; Pfizer: Honoraria, Research Funding; Cyclacel: Research Funding; Immunogen: Research Funding; Agios: Honoraria, Research Funding; Actinium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding; Takeda: Honoraria; Astex: Research Funding; Daiichi-Sankyo: Research Funding. Schimmer:Novartis Pharmaceuticals: Consultancy; Medivir Pharmaceuticals: Research Funding; Jazz Pharmaceuticals: Consultancy; Otsuka Pharmaceuticals: Consultancy. Andreeff:Eutropics: Equity Ownership; Daiichi Sankyo, Inc.: Consultancy, Patents & Royalties: Patents licensed, royalty bearing, Research Funding; Jazz Pharmaceuticals: Consultancy; Celgene: Consultancy; Aptose: Equity Ownership; Reata: Equity Ownership; 6 Dimensions Capital: Consultancy; AstaZeneca: Consultancy; Amgen: Consultancy; Breast Cancer Research Foundation: Research Funding; CPRIT: Research Funding; NIH/NCI: Research Funding; Center for Drug Research & Development: Membership on an entity's Board of Directors or advisory committees; Cancer UK: Membership on an entity's Board of Directors or advisory committees; NCI-CTEP: Membership on an entity's Board of Directors or advisory committees; German Research Council: Membership on an entity's Board of Directors or advisory committees; Leukemia Lymphoma Society: Membership on an entity's Board of Directors or advisory committees; NCI-RDCRN (Rare Disease Cliln Network): Membership on an entity's Board of Directors or advisory committees; CLL Foundation: Membership on an entity's Board of Directors or advisory committees; BiolineRx: Membership on an entity's Board of Directors or advisory committees; Oncolyze: Equity Ownership; Oncoceutics: Equity Ownership; Senti Bio: Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Ishizawa:Daiichi Sankyo: Patents & Royalties: Joint submission with Daiichi Sankyo for a PTC patent titled "Predictive Gene Signature in Acute Myeloid Leukemia for Therapy with the MDM2 Inhibitor DS-3032b," United States, 62/245667, 10/23/2015, Filed.

Introduction: Despite therapeutic advances, there remains a considerable need for novel therapies for B-cell lymphomas. Although a high proportion of patients (pts) show response to initial therapy, many fail to achieve durable remissions and experience recurrent disease. Agents that target molecular pathways associated with the development and progression of lymphoma are likely to be highly effective and are desirable. The p110δ isoform of the PI3K enzyme is mainly expressed in lymphocytes and has been an attractive therapeutic target, with several PI3Kδ inhibitors demonstrating meaningful efficacy in B-cell lymphomas. Targeting the p110β isoform may further overcome tumor growth and escape mechanisms by mitigating the upregulation of the PI3K/AKT pathway, particularly in PTEN-deficient lymphomas. KA2237 is an oral, potent and selective inhibitor of the PI3K β and δ isoforms. The aim of this first in human, phase I, open-label, single arm study (NCT02679196) was to investigate the safety, tolerability, pharmacokinetic properties and pharmacodynamic effects of KA2237, in order to determine the maximum tolerated dose based on dose limiting toxicity and assess preliminary anti-tumor activity in pts with R/R B-cell lymphoma. Methods: Pts ≥ 18 years (yrs) of age, ECOG ≤ 2, with B-cell lymphoma R/R or intolerant of established therapies (including rituximab) were enrolled using a 3+3 dose escalation (50-400mg) design. KA2237 was given orally on a once daily continuous schedule until progression or unacceptable toxicity. Anti-tumor activity was evaluated by computed tomography and, when available, integrating 18F-FDG positron emission tomography response assessment, at 8, 16 and 24 weeks. Response was assessed according to Lugano 2014 criteria. Pts received PJP prophylaxis. Results: 21 pts with B-cell lymphoma were enrolled (8 DLBCL [diffuse large B-cell], 5 FL [follicular], 3 MCL [mantle cell], 3 CLL/SLL [chronic lymphocytic leukemia/small lymphocytic lymphoma], 1 MZL [marginal zone], 1 WM [Waldenstrom]). Pts received KA2237 at 4 dose levels: 50mg (n=6), 100mg (n=3), 200mg (n=7) and 400mg (n=5) daily; 21 pts were evaluable for safety assessment. Pharmacokinetic profiles were favorable with mean plasma half-life of 17-33 hours, compatible with once daily oral dosing. Median age was 69 yrs (range 48-84) with 76% males; median number of prior therapies was 3 (range 1-6). Median follow up duration was 8.5 months (range 6.9-24.6). Median duration of drug exposure was 82 days (range 10-714 days). 86% of pts experienced treatment-related adverse events (TRAE). 43% of pts experienced a grade ≥ 3 TRAE, with rash (n=3), transaminitis (n=2) and pneumonitis (n=2) occurring in more than 1 pt. 29% discontinued treatment due to a TRAE with pneumonitis (n=2) occurring in more than 1 pt. One grade 5 TEAE (multifocal pneumonia) was observed. 19/21 pts were evaluable for response, ORR was 37% (4 CR, 3 PR). Responses were observed across lymphoma subtypes including DLBCL, FL, CLL and MCL. Responses were often durable (see Figure) and in 2 pts with DLBCL who achieved CR permitted consolidation by autologous stem cell transplantation. Conclusions: KA2237 is an oral, once a day, selective dual inhibitor of PI3K β/δ with a manageable toxicity profile and promising single-agent clinical activity in heavily pretreated R/R B-cell lymphoma. The recommended phase II dose is 200mg daily. The findings of this study support the further evaluation of KA2237. Figure. Disclosures Nastoupil: Novartis: Honoraria; Spectrum: Honoraria; Janssen: Honoraria, Research Funding; Gilead: Honoraria; Genentech, Inc.: Honoraria, Research Funding; Bayer: Honoraria; Celgene: Honoraria, Research Funding; TG Therapeutics: Honoraria, Research Funding. Neelapu:Acerta: Research Funding; Merck: Consultancy, Research Funding; Poseida: Research Funding; Unum Therapeutics: Consultancy, Research Funding; Karus: Research Funding; Kite, a Gilead Company: Consultancy, Research Funding; Incyte: Consultancy; Precision Biosciences: Consultancy; BMS: Research Funding; Allogene: Consultancy; Pfizer: Consultancy; Cellectis: Research Funding; Novartis: Consultancy; Celgene: Consultancy, Research Funding; Cell Medica: Consultancy. Fowler:Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding; ABBVIE: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Westin:Janssen: Other: Advisory Board, Research Funding; Genentech: Other: Advisory Board, Research Funding; Juno: Other: Advisory Board; Unum: Research Funding; Kite: Other: Advisory Board, Research Funding; Novartis: Other: Advisory Board, Research Funding; Curis: Other: Advisory Board, Research Funding; Celgene: Other: Advisory Board, Research Funding; 47 Inc: Research Funding; MorphoSys: Other: Advisory Board. Wang:Janssen: Consultancy, Honoraria, Research Funding, Speakers Bureau; Acerta Pharma: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria, Research Funding, Speakers Bureau; Celgene: Consultancy, Research Funding; MoreHealth: Consultancy, Equity Ownership; BioInvent: Consultancy, Research Funding; Aviara: Research Funding; BeiGene: Research Funding; Loxo Oncology: Research Funding; VelosBio: Research Funding; Pulse Biosciences: Consultancy; Juno Therapeutics: Research Funding; Pharmacyclics: Consultancy, Honoraria, Research Funding; Dava Oncology: Honoraria; Kite Pharma: Consultancy, Research Funding. Beer:Karus therapeutics Ltd.: Employment. Cecil:Karus Therapeutics: Employment. Dow:Karus Therapeutics: Employment. McHale:Karus Therapeutics: Employment. Silva:Karus Therapeutics: Employment. Ward:Karus Therapeutics: Employment. Yavari:Karus Therapeutics: Employment. Shuttleworth:Karus Therapeutics: Employment.

Notch1-mutated T-ALL is an aggressive hematologic malignancy lacking targeted therapeutic options. Genomic alterations in Notch1-gene and its activated downstream pathways are associated with metabolic stress response and heightened glutamine (Gln) utilization to fuel oxidative phosphorylation (OxPhos) (Kishton at al., Cell Metabolism 2016, 23:649, Herranz at al., Nat Med, 2015, 21(10): 1182-1189). Hence, targeting NOTCH1-associated OxPhos and/or Gln dependency could constitute a plausible therapeutic strategy for T-ALL. In this study we examined metabolic vulnerabilities of NOTCH1-driven T-ALL and tested pre-clinical efficacy of novel mitochondrial complex I (OxPhosi) IACS-010759 and of glutaminase inhibitor CB-839 (GLSi) in T-ALL models including Notch1-mutated T-ALL cell lines, patient-derived xenograft (PDX) and primary T-ALL cells. We have previously reported and confirmed in this expanded study the anti-leukemia efficacy of IACS-010759 (EC50s 0.1-15 nM) (Molina at al., Nat Med, 2018, 24: 1036; Baran at al., Blood, 2018, 132:4020). Metabolic characterization demonstrated that OxPhosi caused striking dose-dependent decrease in basal and maximal oxygen consumption rate (OCR), ATP and NADH generation in T-ALL cell lines and primary T-ALL samples (p OxPhosi, similar to knockout of complex I subunit NDUFS4 using CRISPR-CAS9, induced profound changes in T-ALL mitochondria, with induction of mitochondrial reactive oxygen species (ROS), DNA damage, activation of AMPK and inhibition of mTOR pathway. OxPhosi altered cellular energy homeostasis by reduction of TCA cycle intermediates, glutathione and reduction of intracellular nucleotides ATP, CTP, GTP, and UTP, translating into inhibition of DNA and RNA synthesis (p To confirm that blockade of Gln entry into TCA cycle with GLSi synergistically reduced viable ALL cell numbers, we studied potential synergy of OxPhosi and GLSi. The key role of Gln in maintaining energy production and cell proliferation via OxPhos in Notch1-mutated T-ALL cells was confirmed by the findings that Gln starvation or pharmacological GLS inhibition by CB-839 reduced ATP production and OCR and decreased cell proliferation by more than 50% in vitro (Fig.2, Fig.3). Dual blockade of OxPhos together with GLS induced DNA damage response via accumulation of ROS upon glutathione deprivation, induced AMPK signaling through profound reduction of all adenosine related intermediates and inhibited mTOR signaling. This translated into significant reduction of leukemia burden and extension of overall survival in vivo (p In summary, our findings indicate that dual blockade of metabolic processes by inhibiting complex I of mitochondria and restricting Gln utilization results in metabolic catastrophe in Notch1-mutated T-ALL associated with energy depletion and oxidative stress, which combined severely inhibit T-ALL growth and survival. We postulate that targeting this unique metabolic vulnerability of Notch1-mutated T-ALL cells constitutes a novel therapeutic modality in this aggressive malignancy. Disclosures Kuruvilla: The University of Texas M.D.Anderson Cancer Center: Employment. Jabbour:AbbVie: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Cyclacel LTD: Research Funding; Takeda: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Adaptive: Consultancy, Research Funding; Amgen: Consultancy, Research Funding. Konopleva:Agios: Research Funding; Stemline Therapeutics: Consultancy, Honoraria, Research Funding; Calithera: Research Funding; Astra Zeneca: Research Funding; Kisoji: Consultancy, Honoraria; Ascentage: Research Funding; Genentech: Honoraria, Research Funding; F. Hoffman La-Roche: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria; Eli Lilly: Research Funding; Cellectis: Research Funding; Forty-Seven: Consultancy, Honoraria; Ablynx: Research Funding; Reata Pharmaceuticals: Equity Ownership, Patents & Royalties; AbbVie: Consultancy, Honoraria, Research Funding.

Three proteasome inhibitors have garnered regulatory approvals in various multiple myeloma settings; but drug resistance is an emerging challenge, prompting interest in blocking upstream components of the ubiquitin-proteasome pathway. One such attractive target is the E1 ubiquitin-activating enzyme (UAE); we therefore evaluated the activity of TAK-243, a novel and specific UAE inhibitor. TAK-243 potently suppressed myeloma cell line growth, induced apoptosis, and activated caspases while decreasing the abundance of ubiquitin-protein conjugates. This was accompanied by stabilization of many short-lived proteins, including p53, myeloid cell leukemia 1 (MCL-1), and c-MYC, and activation of the activating transcription factor 6 (ATF-6), inositol-requiring enzyme 1 (IRE-1), and protein kinase RNA-like endoplasmic reticulum (ER) kinase (PERK) arms of the ER stress response pathway, as well as oxidative stress. UAE inhibition showed comparable activity against otherwise isogenic cell lines with wild-type (WT) or deleted p53 despite induction of TP53 signaling in WT cells. Notably, TAK-243 overcame resistance to conventional drugs and novel agents in cell-line models, including bortezomib and carfilzomib resistance, and showed activity against primary cells from relapsed/refractory myeloma patients. In addition, TAK-243 showed strong synergy with a number of antimyeloma agents, including doxorubicin, melphalan, and panobinostat as measured by low combination indices. Finally, TAK-243 was active against a number of in vivo myeloma models in association with activation of ER stress. Taken together, the data support the conclusion that UAE inhibition could be an attractive strategy to move forward to the clinic for patients with relapsed and/or refractory multiple myeloma.

Targeting the stromal cell-derived factor 1α (SDF-1α)/C-X-C chemokine receptor type 4 (CXCR4) axis has been shown to be a promising therapeutic approach to overcome chemoresistance in acute myeloid leukemia (AML). We investigated the antileukemia efficacy of a novel peptidic CXCR4 antagonist, LY2510924, in preclinical models of AML. LY2510924 rapidly and durably blocked surface CXCR4 and inhibited stromal cell-derived factor 1 (SDF-1)α-induced chemotaxis and prosurvival signals of AML cells at nanomolar concentrations more effectively than the small-molecule CXCR4 antagonist AMD3100. In vitro, LY2510924 chiefly inhibited the proliferation of AML cells with little induction of cell death and reduced protection against chemotherapy by stromal cells. In mice with established AML, LY2510924 caused initial mobilization of leukemic cells into the circulation followed by reduction in total tumor burden. LY2510924 had antileukemia effects as monotherapy as well as in combination with chemotherapy. Gene expression profiling of AML cells isolated from LY2510924-treated mice demonstrated changes consistent with loss of SDF-1α/CXCR4 signaling and suggested reduced proliferation and induction of differentiation, which was proved by showing the attenuation of multiple prosurvival pathways such as PI3K/AKT, MAPK, and β-catenin and myeloid differentiation in vivo. Effective disruption of the SDF-1α/CXCR4 axis by LY2510924 may translate into effective antileukemia therapy in future clinical applications.

Immunotherapeutic strategies are promising approaches for the treatment of follicular lymphoma (FL). However, their efficacy may be limited by immunosuppressive elements in the immune system and tumor microenvironment. Therefore, strategies to reverse the effects of the immunosuppressive elements are needed. We observed that regulatory T cells (Tregs) were increased in the peripheral blood at diagnosis and persisted in high numbers after induction of clinical remission with a cyclophosphamide and doxorubicin-containing chemotherapy regimen in FL patients. High levels of peripheral blood Tregs prior to therapy were associated with decreased progression-free survival in FL patients treated with either chemotherapy or combination immunotherapy that targeted CD20 and PD-1 with monoclonal antibodies rituximab and pidilizumab, respectively. Intratumoral and peripheral blood Tregs potently suppressed autologous antitumor effector T cells in FL. However, the effects of FL Tregs could be reversed by triggering Toll-like receptors (TLR) with TLR ligands Pam3 CSK4 (TLR 1/2), flagellin (TLR 5), and CpG-B (TLR 9), and/or OX40. The TLR ligands synergized with each other as well as OX40 signaling to inhibit Tregs. Furthermore, they restored the function of FL tumor-specific effector T cells. Our results suggest that a state of tolerance exists in FL patients at diagnosis and after induction of clinical remission, and agents that activate TLRs 1/2, 5, and 9, and OX40 may serve as adjuvants to enhance the efficacy of antitumor immunotherapeutic strategies and preventive vaccines against infectious diseases in these patients.

We used clustered regularly interspaced short palindromic repeats/Cas9-mediated genomic modification to investigate B-cell receptor (BCR) signaling in cell lines of diffuse large B-cell lymphoma (DLBCL). Three manipulations that altered BCR genes without affecting surface BCR levels showed that BCR signaling differs between the germinal center B-cell (GCB) subtype, which is insensitive to Bruton tyrosine kinase inhibition by ibrutinib, and the activated B-cell (ABC) subtype. Replacing antigen-binding BCR regions had no effect on BCR signaling in GCB-DLBCL lines, reflecting this subtype's exclusive use of tonic BCR signaling. Conversely, Y188F mutation in the immunoreceptor tyrosine-based activation motif of CD79A inhibited tonic BCR signaling in GCB-DLBCL lines but did not affect their calcium flux after BCR cross-linking or the proliferation of otherwise-unmodified ABC-DLBCL lines. CD79A-GFP fusion showed BCR clustering or diffuse distribution, respectively, in lines of ABC and GCB subtypes. Tonic BCR signaling acts principally to activate AKT, and forced activation of AKT rescued GCB-DLBCL lines from knockout (KO) of the BCR or 2 mediators of tonic BCR signaling, SYK and CD19. The magnitude and importance of tonic BCR signaling to proliferation and size of GCB-DLBCL lines, shown by the effect of BCR KO, was highly variable; in contrast, pan-AKT KO was uniformly toxic. This discrepancy was explained by finding that BCR KO-induced changes in AKT activity (measured by gene expression, CXCR4 level, and a fluorescent reporter) correlated with changes in proliferation and with baseline BCR surface density. PTEN protein expression and BCR surface density may influence clinical response to therapeutic inhibition of tonic BCR signaling in DLBCL.

Introduction Anti-apoptotic Bcl2 family members mediate resistance to therapies in acute myeloid leukemia (AML)1. The small molecule Bcl2 inhibitor ABT-199 (venetoclax) promotes mitochondria driven intrinsic apoptosis, and in combination with hypomethylating agents or chemotherapy, has been highly promising in the clinic as treatment of AML2-4. The response rate to ABT-199 is very impressive, but acquired resistance is a major problem. Compensatory upregulation of Mcl1 is an important mechanism of such acquired resistance to mitochondrial apoptosis5. Autophagy is vital for mitochondrial health, mediates resistance to apoptosis and is induced by Bcl2 inhibition6. We performed mechanistic studies to address our hypothesis that disabling autophagy by targeting the apical autophagy kinase ULK1 can reverse resistance to ABT-199. Methods ULK1 was genetically modified in OCIAML3 (human AML cell line), by shRNA knockdown (KD) or CRISPR-Cas9 knockout (KO). In addition, AML cell lines (including ABT-199 resistant) and patient samples were treated with ABT-199 and ULK1 inhibitor SBI-02069657. Combination index (CI) for drug synergy was calculated based on Chou-Talalay method8. Drug-treated or genetically manipulated cells were profiled by reverse phase protein array (RPPA), mass cytometry (CyTOF) and gene expression profiling (GEP). Autophagy was detected by LC3 quantification by western blot (WB) and flow cytometry, and monodansylcadaverine assay. Mitochondrial functions were analyzed by Seahorse Cell Mito Stress test, and MTG, TMRE and ROS assays (flow cytometry). For in vivo studies ULK1 KO and corresponding control cells were injected in NSG mice and monitored by bioluminescent imaging (BLI) and quantification of human CD45 cells. Results ABT-199 induced autophagy in OCIAML3 (increase by 175±27%, p=0.01 - LC3 flow; 4X increase in LC3 II/I ratio - WB). Apoptosis induction by ABT-199 was enhanced by ULK1 KD (36±1.9% over control, p Mcl1 was significantly downregulated by ULK1 inhibitor alone and in combination with ABT-199. ULK1 inhibition lowered Mcl1 transcription, as measured by qRT-PCR: 43±0.03% with SBI-0206965 and 63±0.3% in KO cells (both p Since ABT-199 modulates mitochondrial function, we examined the effect of inhibiting ULK1 in this context. By Seahorse assay, the combination decreased basal OCR and ATP production by 62 and 58% respectively, p Corroborating our earlier data, the ABT-199 resistant cells (OCIAML2R & MOLM13R) show enhanced autophagy as compared to parental cells (OCIAML2: 83%, MOLM13: 35% increase; p=0.001 & 0.009). SBI-0206965 reversed ABT-199 induced autophagy and restored ABT-199 sensitivity in these cells (Fig 4). In a pilot in vivo experiment control and ULK1 KO cells were injected in NSG mice and leukemia engraftment was markedly delayed in the ULK1 KO group (Fig 5). The therapeutic combination study is ongoing. Conclusion Results indicate concomitant targeting of autophagy by ULK1 inhibition and Bcl2 inhibition by ABT-199 can overcome acquired resistance to ABT-199. Hence, with the emergence of Bcl2 inhibitors in frontline therapy for AML and efforts at developing ULK1 inhibitors, this study informs the development of novel apoptosis/autophagy targeting approaches to improve AML therapy. Disclosures Konopleva: Stemline Therapeutics: Research Funding; abbvie: Research Funding; Immunogen: Research Funding; cellectis: Research Funding. Andreeff:Daiichi-Sankyo: Consultancy, Patents & Royalties: MDM2 inhibitor activity patent, Research Funding; United Therapeutics: Patents & Royalties: GD2 inhibition in breast cancer ; Aptose: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Research Funding; Jazz Pharma: Consultancy; SentiBio: Equity Ownership; Oncolyze: Equity Ownership; Celgene: Consultancy; Reata: Equity Ownership; Oncoceutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Eutropics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Research Funding.

Background: Persistence of leukemia initiating cells (LIC) in T acute lymphoblastic leukemia (T-ALL) results in relapse in 20- 25% of pediatric and over 50% of adult patients1. LIC are characterized by high CD44 expression and low reactive oxygen species (ROS) levels 2, 3. T-ALL LIC maintain low ROS by cystine/glutamate anti-porter complex of which CD44 is a key component 2, 4. CD44 also interacts with microenvironmental components; hyaluronic acid, osteopontin, fibronectin etc. NOTCH1 transcriptionally upregulates CD44/MYC by binding the upstream 'super-enhancer' sites. BRD4, a member of the bromodomain and extra terminal domain (BET) family, is a critical scaffold of super-enhancer complexes that binds acetylated histones (3 and 4) and drives NOTCH1 mediated MYC/CD44 transcription 5, 4, 1. We hypothesized that degradation of BRD4 with hetero-bifunctional PROteolysis TArgeting Chimera (PROTACTM) such as ARV-825, will lead to efficient and sustained downregulation of NOTCH1/MYC /CD44 transcription and disrupt cell intrinsic and extrinsic pathways for persistence of T-ALL LIC. Methods: We confirmed the anti-leukemia effect of ARV-825 (IC50 pico to low nanomolar) against T-ALL cells including early T-cell phenotype (ETP) and Gamma-secretase inhibitor (GSI) resistant T-ALL8. To confirm disruption of NOTCH1/MYC/CD44 axis in-vivo, we specifically tested the impact of BRD4 degradation on NOTCH1 and its target genes including MYC, CD44 and as functional readout, intra-cellular ROS, in a T-ALL/ patient-derived xenograft (PDX) mouse model of disseminated leukemia possessing a constitutively active NOTCH1 mutation. Mass cytometry based proteomic analysis (CyTOF) studies were done to quantitatively assess T-ALL LICs and suppression of NOTCH1-MYC-CD44 axis, and secondary transplantation was carried out into sub-lethally irradiated mouse recipients to functionally evaluate LIC elimination. Results: ARV-825 mediated sustained BRD4 degradation resulted in profound down-regulation of MYC, CD98, CD44 and its variants (CD44v). Moreover, we observed down-regulation of cell intrinsic anti-apoptotic proteins Bcl-2, Bcl-XL. As a functional correlate of down-regulation of CD98/CD44/CD44v (glutathione anti-porter system), flow cytometry confirmed increased intracellular ROS and decreased reduced glutathione (GSH). In a PDX mouse model of human T-ALL, ARV-825 treatment improved survival compared to mice treated with vehicle (P=0.002) (Fig.1). CyTOF analysis of mouse bone marrow cells showed quantitative reduction of phenotypically defined LIC (CD4+CD8+CD7+ CD19- ) 6,7 with down regulation of the NOTCH1-MYC-CD44 axis along with oncogenic molecules (transcription factors Myc and NFkB, cell cycle regulators, activated PI3K/Akt, and anti-apoptotic Bcl2 family proteins) in mice treated with ARV-825 (Fig.2). Finally, secondary transplantation of equal number of human CD45+ cells from Vehicle and ARV-825 treated mice in to NSG mice led to delayed leukemia development and extended survival of mice engrafted from ARV-825 treated mice (Vehicle:38 days Vs ARV-825: 58 days P=0.0001/ Vehicle:36.5 days Vs ARV-825: 50 days P=0.0001) (Fig.3), providing functional confirmation of LIC elimination. Conclusion: Degradation of BRD4 with PROTAC (ARV-825), modulates the NOTCH1/MYC/CD44 axis and has the potential of therapeutically targeting the LIC in T-ALL. Reference Pui CH, Carroll WL, Meshinchi S, Arceci RJ. Journal of clinical oncology 2011; 29(5): 551-565. Ishimoto T, Nagano O, Yae T, Tamada M, Motohara T, Oshima H et al.Cancer cell 2011; 19(3): 387-400. Diehn M, Cho RW, Lobo NA, Kalisky T, Dorie MJ, Kulp AN et al.Nature 2009; 458(7239): 780-783. Garcia-Peydro M, Fuentes P, Mosquera M, Garcia-Leon MJ, Alcain J, Rodriguez A et al.The Journal of clinical investigation 2018. doi: 10.1172/JCI92981 Sanchez-Martin M, Ferrando A. Blood 2017; 129(9): 1124-1133. Cox CV, Martin HM, Kearns PR, Virgo P, Evely RS, Blair A. Blood 2007; 109(2): 674-682. Gerby B, Clappier E, Armstrong F, Deswarte C, Calvo J, Poglio S et al.Leukemia 2011; 25(8): 1249-1258. Sujan Piya, Hong Mu, Seemana Bhattacharya, Teresa McQueen, R. Eric Davis, Vivian Ruvolo, Natalia Baran, Yimin Qian, Craig M. Crews, M. James You , Patrick Zweider-McKay, Marina Konopleva, Hagop Kantarjian , Michael Andreeff1, Gautam Borthakur. 59 th Annual Meeting &Exposition, Atlanta GA: December 9-12, 2017. Disclosures Qian: Arvinas LLC Inc: Employment. Raina:Arvinas LLC Inc: Employment. Konopleva:Stemline Therapeutics: Research Funding. Andreeff:Aptose: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Oncoceutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Reata: Equity Ownership; SentiBio: Equity Ownership; Oncolyze: Equity Ownership; Eutropics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Astra Zeneca: Research Funding; Daiichi-Sankyo: Consultancy, Patents & Royalties: MDM2 inhibitor activity patent, Research Funding; United Therapeutics: Patents & Royalties: GD2 inhibition in breast cancer ; Jazz Pharma: Consultancy; Celgene: Consultancy; Amgen: Consultancy, Research Funding.

Introduction: Optimal CB unit selection guidelines recommend consideration of CD34+ cell dose & 8-allele donor-recipient HLA-match. How graft characteristics for these parameters vary by patient (pt) race/ ethnicity, however, is not known. Methods: We analyzed the infused graft & back-up unit cryopreserved total nucleated cell (TNC) x 107 & CD34+ x 105 cell content, the cell dose (incorporating pt weight), & 4-6/6 & 8-allele HLA-match by pt ancestry in CB transplant (CBT) recipients transplanted 1/2014-6/2018. Units were chosen based on banking practices (e.g. RBC depleted, standard cryo volumes), TNC & CD34+ dose & 4-6/6 & 8-allele HLA-match with dose usually taking priority over match given pt size at our center. The analysis included transplanted units (considered the best choice) & the next best high resolution typed back-up units (reserved but not shipped). Pt racial/ ethnic origins were prospectively obtained by detailed family history & grouped as previously described (Barker J. et al. BBMT 2010). Results: The characteristics of 513 units chosen for 136 CBT recipients by pt ancestry are shown (Table 1). Pts had highly diverse origins including 70 (51%) non-Europeans. The 513 units included 270 units infused as the graft (134 doubles & 2 singles) & 243 back-up units (109 pts had 2 back-ups, 25 pts had one & 2 had none). Thus, 4 best units were analyzed in 109 pts (all double unit recipients), 3 best in 25 pts (all doubles), & 1 unit in 2 pts (both singles). The median weight of the 136 pts was 81 kg. Asian pts (median 68 kg) had a lower weight than other groups. The median TNC content of units for the 66 European pts was higher than that for the 70 Non-Europeans (218 vs 196, p = 0.004). Units chosen for Northwestern (NW) Europeans had the highest median TNC content (235) with lower TNC content in units for Southern Europeans (202), Asian (193), African (191) & White Hispanic (189) pts. Units chosen for European pts also had a higher median CD34+ cell content (162) than Non-Europeans (138), p = 0.004. NW Europeans had units with a higher median CD34+ content (198) & the lowest CD34+ content were those for African (124) & Middle Eastern pts (124). When patient weight was considered, median TNC/kg dose per unit was similar in European and Non-European pts (2.7 vs 2.6, p = NS). Units for NW Europeans had the highest median TNC dose (3.0) whereas those for African pts had the lowest TNC dose (2.4). Units for Europeans had a higher median CD34+ dose (2.0) than Non-Europeans (1.7) although this difference was not significant (p = 0.15). Additionally, similar to TNC dose, median CD34+ dose was highest in units for NW European pts (2.2) & lowest in units chosen for African pts (1.5). 89% of chosen units were 4/6 HLA-matched with no differences between Europeans & non-Europeans. Furthermore, the median 8 allele HLA-match was 5/8 (range 2-8/8) with no overall differences between units for Europeans and Non-Europeans (p = NS). When only transplanted units were analyzed (Table 2), the median TNC & CD34+ contents were significantly lower in non-Europeans than Europeans (238 vs 216, p = 0.01 & 184 vs 160, p = 0.016). Overall, however, units received by Europeans vs non-European pts had similar TNC & CD34+ doses (p = NS). However, differences in the CD34+ content combined with differences in pt weights resulted in disparities in CD34+ doses by ancestry sub-group. NW Europeans (high weight, high CD34+ content) received the best CD34+ doses; lower CD34+ content in Asian pts was compensated for by their lower weight. African pts (high weight, low CD34+ content) received the lowest CD34+ doses. The median 8 allele HLA-match for all was 5/8 (range 3-8/8) with the exception of African pts [median 4/8 (range 3-7/8)]. Moreover, while 108 (40%) of transplanted units were 3-4/8 HLA-matched overall, there were marked differences between pt sub-groups with only 23% of units for NW Europeans being 3-4/8 vs 42% for southern Europeans, 46% for white Hispanics & 53% for Africans. Conclusions: While CB significantly extends transplant access to racial & ethnic minorities, differences in cellular content translates to many minority pts receiving lower dosed units. There are also marked racial/ ethnic differences in HLA-match grade with African pts the most likely to receive highly mismatched units. This data supports ongoing funding of public CB banks to further increase the inventory of high dosed & better matched units for all but especially racial & ethnic minority pts. Disclosures Shah: Janssen: Research Funding; Amgen: Research Funding. Kernan:National Cancer Institute: Research Funding.

Acute myeloid leukemia (AML) stem cells (LSC) are an extremely rare fraction of the overall disease (likely We previously introduced a novel bioinformatics approach that harnessed publically available AML gene expression data to identify genes significantly over-expressed in LSCs when compared to their normal hematopoietic stem cell (HSC) counterparts (Herbrich et al Blood 2017 130:3962). These datasets contain gene expression arrays on human AML patient samples sorted by leukemia stem, progenitor, and blast cells (with normal hematopoietic cell subsets for comparison). We have since expanded our statistical model to identify targets that are both significantly overexpressed in AML LSCs when compared to HSC as well as LSCs compared to their corresponding, more differentiated blast cells. Instead of traditional methods for multiple testing corrections, we looked at the intersection of genes that met the above criteria in 3 independently generated datasets. This resulted in a list of 30 genes, 28 of which appear to be novel markers of AML LSCs. From this list, we first chose to focus on CD200, a type-1 transmembrane glycoprotein. CD200 is broadly expressed on myeloid, lymphoid, and epithelial cells, while the CD200 receptor (CD200R) expression is strictly confined to myeloid and a subset of T cells. CD200 has been shown to have an immunosuppressive effect on macrophages and NK cells and correlates with a high prevalence FOXP3+ regulatory T cells (Coles et al Leukemia 2012; 26:2146-2148). Additionally, CD200 has been implicated as a poor prognostic marker in AML (Damiani et al Oncotarget 2015; 6:30212-30221). To date, we have screened 20 primary AML patient samples by flow cytometry, 90% of which are positive for CD200. Expression is significantly enriched in the CD34+/CD123+ stem cell compartment. To examine the role of CD200 in AML, we established two in vitro model systems. First, we used CRISPR/Cas9 to knockout the endogenous CD200 protein in Kasumi-1. Further, we induced CD200 in the OCI-AML3 cell line that had no expression at baseline. Both cell lines did not express the CD200 receptor before or after manipulation, negating any autocrine signaling. In both systems, CD200 manipulation did not affect the proliferation rate or viability of the cells. To examine the immune function of CD200 in AML, we performed a series of mixed lymphocyte reactions. We cultured normal human peripheral blood mononuclear cells (PBMCs) with the CD200+ or CD200- cells from each line both. Cells were incubated in the culture media for 4-48 hours before being harvested and measured by flow cytometry for apoptosis or intracellular cytokine production. The presence of CD200 on the cell surface reduced the rate of immune-specific apoptosis among these leukemia cells. The difference in cell killing was most likely attributable to a CD200-specific suppression of CD107a, a surrogate marker or cytotoxic activity. In the OCI-AML3 model, PBMCs co-cultured with CD200+ cells produced approximately 40% less CD107a when compared to the CD200- co-culture. Additionally, we characterized our new cell lines using RNA sequencing. By comparing the CD200+ to the CD200- cells within each line, we observed that CD200+ cells significantly downregulate genes involved in defining an inflammatory response as well as genes regulated by NF-κB in response to TNFα. This indicates that CD200 may have an undiscovered intrinsic role in suppressing the immune microenvironment of AML LSCs. In conclusion, we have expanded our novel bioinformatics approach for robustly identifying AML LSC-specific targets. Additionally, we have shown that one of these markers, CD200, has a potential role as a stem cell-specific immunosuppressive target by reducing immune-mediated apoptosis and transcriptionally suppressing inflammatory cell processes. We are extending our study to explore CD200 in primary patient samples using a CD200-blocking antibody. Disclosures Andreeff: SentiBio: Equity Ownership; Amgen: Consultancy, Research Funding; Oncolyze: Equity Ownership; Reata: Equity Ownership; United Therapeutics: Patents & Royalties: GD2 inhibition in breast cancer ; Jazz Pharma: Consultancy; Astra Zeneca: Research Funding; Aptose: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Consultancy, Patents & Royalties: MDM2 inhibitor activity patent, Research Funding; Eutropics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Oncoceutics: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy. Konopleva:Stemline Therapeutics: Research Funding.

Adult T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy characterized by limited therapeutic options and a high rate of treatment failure due to chemoresistance. T-ALL is largely driven by activating NOTCH1 mutations, where oncogenic NOTCH1 facilitates glutamine oxidation, induces metabolic stress, and facilitates reliance on oxidative phosphorylation (OXPHOS)1. In other malignancies, the shift toward OXPHOS-dependent high-energy status is associated with acquired chemoresistance. In this study, we found that the novel inhibitor of mitochondrial complex I (OXPHOSi) IACS-0107592 has preclinical activity in NOTCH1-mutated T-ALL; we also characterize the cellular and metabolic responses to OXPHOS inhibition and propose that an OXPHOSi be incorporated into standard-of-care therapy to improve outcomes in patients harboring NOTCH1-mutated T-ALL. Exposure to IACS-010759 (0-370 nM) in vitro drastically reduced T-ALL viability, with EC50 ranging from 0.1-10 nM for cell lines (n=7) and from 13-60 nM for patient-derived xenograft (PDX)-derived and primary T-ALL cells (n=10) (Fig.1). Oral administration of IACS-010759 (7.5 mg/kg/day) significantly reduced leukemia burden and extended overall survival (p In summary, our findings indicate that OXPHOSi, alone and particularly in combination with standard chemotherapy and GLS inhibition, constitutes a novel therapeutic modality that targets a unique metabolic vulnerability of NOTCH1-mutated T-ALL cells. References:Kishton RJ, Barnes CE, Nichols AG at al., AMPK Is Essential to Balance Glycolysis and Mitochondrial Metabolism to Control T-ALL Cell Stress and Survival, Cell Metabolism, 2016, 23(4):649-62Molina JR, Sun Y, Protopopova M et al., An inhibitor of oxidative phosphorylation exploits cancer vulnerability, Nat Med, 2018, 24: 1036-1046 Disclosures Lorenzi: NIH: Patents & Royalties; Erytech Pharma: Consultancy. Konopleva:Stemline Therapeutics: Research Funding.

Introduction: We have previously reported the results of cohort A from a single arm, phase II clinical trial of lenalidomide with rituximab (R2) as frontline treatment for patients with previously untreated follicular lymphoma (FL), Fowler N et al Lancet Oncology 2014. Recent randomized studies (RELEVANCE) did not demonstrate superiority of either R2 or R-Chemo in untreated, high GELF FL, but follow up is short. We now report outcomes of an additional extended dosing cohort (12 mo of R2) and the long term follow up of the both dosing schedules in untreated FL. Methods: A total of 154 pts were included in the original clinical trial (FL, n=80; MZL, n=31; SLL, n=43). Characteristics were collected at the time of starting R2 treatment. Patients received lenalidomide 20 mg/day on days 1-21 of each 28-day cycle and rituximab 375 mg/m2 on day 1 of each cycle (6 cycles; schedule A) and lenalidomide 20 mg/day on days 1-21 of each 28-day cycle for cycles 1-6 then lenalidomide 10 mg/day on days 2-22 for cycles 7-12 with rituximab 375mg/m2 IV x1 weekly on cycle 1 and day 1 of every subsequent cycle (12 cycles; schedule B). Responders continued treatment for at least 6 but up to 12 cycles. The primary endpoint was overall response rate (ORR); secondary endpoints were complete and partial response (CR, PR), safety, and progression free survival (PFS). PFS was defined as time from starting treatment to disease progression or death, event free survival included time from starting treatment to discontinuation due to any cause and overall survival (OS) was defined from the time of initial diagnosis of FL to death/last follow up. Results: Eighty pts with FL were enrolled in study and followed a median of 86 months. Median age was 58 years (range, 29 to 84); 50% were males. 61% pts had grade 1 FL and 39% had grade 2 FL. Schedule A was administered in 50 pts and schedule B in 30 pts. Seventy seven pts were evaluable for initial response assessment and 76 (98%) responded. The best response rate was 95% (87% CR/CRu). At the time of last follow up, 23 patients experienced disease progression, 13 lost to follow up (all had CR as best response and had completed tx), 4 came off study due to pt choice/financial and 4 due to intolerance (2 arterio-thrombotic event, 1 respiratory failure, 1 intolerance) during therapy. After a median follow up of 86 mo, 23 pts (29%) progressed, 5 yr PFS was 75%. Five yr PFS was 70% and 82% for pts on cohort A vs B respectively (P=.30). Overall, 2 pts died, with a 5 year survival 97%, Figure-1 (A-B). The median event free survival in pts with FL was 85 months with a 5 year EFS of 59%. Subgroup analysis showed no statistically significant difference in PFS with FLIPI score, bulky disease and by initial bone marrow involvement. Pts who achieved CR had significantly longer PFS compared to those who did not achieve CR (not reached vs 78 months; p = 0.004), however the OS was not significantly different between the two groups Figure-1 (C-F). Grade 3 or 4 hematologic AEs included neutropenia (28%), thrombocytopenia (3%), and no anemia. Count recovery occurred in all pts with follow up and/or dose modification. Nine pts developed second primary cancers, including one melanoma in-situ, 3 localized skin cancers, and 2 secondary hematologic malignancies. Conclusions: A combination of lenalidomide with rituximab produced durable responses in pts with FL. At a follow up of 7 years, the majority of pts remain in remission and patients who achieved CR had the best outcomes. Five year PFS may be longer in pts who received 12mo of therapy, but will need larger analysis to confirm. Further studies are ongoing to analyze mutation dynamics and genomic profile to identify molecular biomarkers. Disclosures Fowler: Janssen: Consultancy, Research Funding; Pharmacyclics: Consultancy, Research Funding. Nastoupil:Novartis: Honoraria; Juno: Honoraria; Gilead: Honoraria; TG Therappeutics: Research Funding; Spectrum: Honoraria; Janssen: Research Funding; Merck: Honoraria, Research Funding; Karus: Research Funding; Genentech: Honoraria, Research Funding; Celgene: Honoraria, Research Funding. Westin:Apotex: Membership on an entity's Board of Directors or advisory committees; Celgen: Membership on an entity's Board of Directors or advisory committees; Kite Pharma: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees. Wang:Kite Pharma: Research Funding; Novartis: Research Funding; Pharmacyclics: Honoraria, Research Funding; Dava Oncology: Honoraria; Juno: Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; AstraZeneca: Consultancy, Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; MoreHealth: Consultancy; Acerta Pharma: Honoraria, Research Funding. Samaniego:ADC Therapeutics: Research Funding.

Chimeric antigen receptor (CAR)-modified T-cell therapy targeting CD19 induces high response rates in patients with relapsed or refractory B-cell lymphomas. However, about 60% of patients experience primary or secondary resistance after CD19-targeted CAR T-cell therapy and a major of cause of failure appears to be due to loss of CD19 expression on the tumor. Therefore, novel targets for adoptive T-cell therapeutic approaches are needed to further improve clinical outcome in these patients. T-cell leukemia/lymphoma antigen1 (TCL1) is an oncoprotein that is overexpressed in multiple B-cell malignancies including follicular lymphoma (FL), mantle cell lymphoma (MCL), diffuse large B-cell lymphoma (DLBCL), and chronic lymphocytic leukemia (CLL). Importantly, it has restricted expression in only a subset of B cells among normal tissues. We previously identified a TCL1-derived HLA-A2-binding epitope (TCL170-79 SLLPIMWQLY) that can be used to generate TCL1-specific CD8+ T cells from peripheral blood mononuclear cells of both HLA-A2+ normal donors and lymphoma patients. More importantly, we showed that the TCL1-specific CD8+ T cells lysed autologous primary lymphoma cells but not normal B cells (Weng et al. Blood 2012). To translate the above discovery into clinic, we cloned the T-cell receptor (TCR) alpha and beta chains from a TCL1-specific CD8+ T-cell clone and showed that this TCL1-TCR could be transduced into polyclonal donor T cells using a lentiviral system with a transduction efficiency of >40% as determined by TCL170-79 tetramer positive T cells. Furthermore, we demonstrated that the TCL1-TCR-transduced T cells recognized T2 cells pulsed with TCL170-79 peptide producing IFN- γ >8 ng/ml and IL-2 >350 ng/ml but were not reactive to control HIV-Gag peptide (IFN- γ 10 ng/ml) suggesting it has moderate to high avidity. Importantly, TCL1-TCR-transduced T cells lysed HLA-A2+ (up to 43% lysis of Mino and 25% lysis of Jeko-1 at 40:1 Effector:Target ratio) but not HLA-A2- lymphoma cell lines (5.5% lysis of HLA A2- Raji and 2.3% lysis of Daudi at 40:1 Effector:Target ratio). TCL1-TCR-transduced T cells were also cytotoxic to HLA-A2+ primary lymphoma tumor cells (up to 48% lysis of CLL, 43% lysis of FL, 41% lysis of DLBCL, 46% lysis of splenic marginal zone lymphoma, and 11% lysis of MCL at 40:1 Effector:Target ratio) but not normal B cells derived from the same patients. Lastly, TCL1-TCR transduced T cells showed high efficacy in in vivo models. Adoptive transfer of the TCL1-TCR-tranduced T cells significantly reduced lymphoma tumor growth and extended survival in Mino mantle cell lymphoma cell line xenograft model (48% survival in TCL1-TCR-T treated group vs. 12.5% survival in control group at 10 weeks n=7-8 mice/group; P=0.02). Collectively, our data suggest that the high expression in B-cell tumors, restricted expression in normal tissues, and presence of an immunogenic CD8 T-cell epitope, make TCL1 a target for T cell-based therapeutic approaches in multiple B-cell malignancies. Our results also demonstrate that the TCL1-specific TCR-transduced T cells may serve as a novel adoptive immunotherapy approach for the treatment of patients with various B-cell malignancies (including FL, MCL, DLBCL, CLL). Acknowledgments: This study is supported by MD Anderson Moon Shot Program and CPRIT and the National Natural Science Foundation of China Grant (No. 81570189) Disclosures Neelapu: Kite/Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cellectis: Research Funding; Poseida: Research Funding; Merck: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Research Funding; Karus: Research Funding; Bristol-Myers Squibb: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees; Unum Therapeutics: Membership on an entity's Board of Directors or advisory committees.

The microenvironment of human follicular lymphoma (FL), an incurable B cell non-Hodgkin’s lymphoma, is thought to play a major role in its pathogenesis and course. Microenvironmental cells of likely importance include follicular Th cells (TFH) and regulatory T cells (Tregs), and understanding their interactions with FL tumor cells is necessary to develop novel therapeutic strategies. We found that IL-4 and CD40L are expressed by intratumoral TFH and induce production of CCL17 and CCL22 by FL tumor cells. IL-4 alone induces only CCL17 but enhances stimulation by CD40L of both CCL17 and CCL22. Consistent with our in vitro results, mRNA transcripts of IL-4 correlated with CCL17, but not CCL22, in gene expression profiling studies of FL biopsies, whereas CD40L correlated with both CCL17 and CCL22. Tumor supernatants induced preferential migration of Tregs and IL-4–producing T cells rather than IFN-γ–producing T cells, and Abs to CCR4 significantly abrogated the migration of Tregs. Our results suggest that through two distinct mechanisms, intratumoral TFH induce production of CCL17 and CCL22 by FL tumor cells and facilitate active recruitment of Tregs and IL-4–producing T cells, which, in turn, may stimulate more chemokine production in a feed-forward cycle. Thus, TFH appear to play a major role in generating an immunosuppressive tumor microenvironment that promotes immune escape and tumor survival and growth. Our results provide novel insights into the cross talk among TFH, tumor cells, and Tregs in FL, and offer potential targets for development of therapeutic strategies to overcome immune evasion.

Chromosomal region maintenance 1 (CRM1) is a nuclear export receptor recognizing proteins bearing a leucine-rich nuclear export signal. CRM1 is involved in nuclear export of tumor suppressors such as p53. We investigated the prognostic significance of CRM1 in acute myeloid leukemia (AML) and effects of a novel small-molecule selective inhibitor of CRM1. CRM1 protein expression was determined in 511 newly diagnosed AML patients and was correlated with mouse double minute 2 (MDM2) and p53 levels. High CRM1 expression was associated with short survival of patients and remained an adverse prognostic factor in multivariate analysis. CRM1 inhibitor KPT-185 induced mainly full-length p53 and apoptosis in a p53-dependent manner, whereas inhibition of proliferation was p53 independent. Patient samples with p53 mutations showed low sensitivity to KPT-185. Nuclear retention of p53 induced by CRM1 inhibition synergized with increased levels of p53 induced by MDM2 inhibition in apoptosis induction. KPT-185 and Nutlin-3a, alone and in combination, induced synergistic apoptosis in patient-derived CD34(+)/CD38(-) AML, but not in normal progenitor cells. Data suggest that CRM1 exerts an antiapoptotic function and is highly prognostic in AML. We propose a novel combinatorial approach for the therapy of AML, aimed at maximal activation of p53-mediated apoptosis by concomitant MDM2 and CRM1 inhibition.

Proteasome inhibition with bortezomib is a validated approach to the treatment of multiple myeloma, but drug resistance often emerges and limits its utility in the retreatment setting. To begin to identify some of the mechanisms involved, we developed bortezomib-resistant myeloma cell lines that, unlike previously reported models, showed no β5 subunit mutations. Instead, up-regulation of the insulin-like growth factor (IGF)–1 axis was identified, with increased autocrine and paracrine secretion of IGF-1, leading to increased activation of the IGF-1 receptor (IGF-1R). Exogenous IGF-1 reduced cellular sensitivity to bortezomib, whereas pharmacologic or small hairpin RNA–mediated IGF-1R suppression enhanced bortezomib sensitivity in cell lines and patient samples. In vitro studies with OSI-906, a clinically relevant dual IGF-1R and insulin receptor inhibitor, showed it acted synergistically with bortezomib, and potently resensitized bortezomib-resistant cell lines and patient samples to bor-tezomib. Importantly, OSI-906 in combination with bortezomib also overcame bor-tezomib resistance in an in vivo model of myeloma. Taken together, these data support the hypothesis that signaling through the IGF-1/IGF-1R axis contributes to acquired bortezomib resistance, and provide a rationale for combining bortezomib with IGF-1R inhibitors like OSI-906 to overcome or possibly prevent the emergence of bortezomib-refractory disease in the clinic.

Autophagy is a cellular adaptive mechanism to stress, including that induced by chemotherapeutic agents. Reverse phase protein array suggested that high expression of the essential autophagy-related protein, Atg7, was associated with shorter remission in newly diagnosed acute myeloid leukemia (AML) patient samples, indicating a role in chemoresistance. Knockdown of Atg7 in AML cells using short hairpin RNA markedly increased apoptosis and DNA damage following treatment with cytarabine and idarubicin. Interestingly, coculture of AML cells with stromal cells increased autophagy and chemoresistance in the AML cells exposed to chemotherapeutic agents, and this was reversed following Atg7 knockdown. This effect was further enhanced by concomitant knockdown of Atg7 in both AML and stromal cells. These findings strongly suggest that Atg7, and likely microenvironment autophagy in general, plays an important role in AML chemoresistance. Mechanistic studies revealed that Atg7 knockdown induced a proapoptotic phenotype in AML cells, which was manifested by an increased NOXA expression at the transcriptional level. Finally, in a mouse model of human leukemia, Atg7 knockdown extended overall survival after chemotherapy. Thus, the inhibition of Atg7 appears to be a valid strategy to enhance chemosensitivity, and it could indeed improve outcomes in AML therapy.

Modulating aberrant transcription of oncogenes is a relatively unexplored opportunity in cancer therapeutics. In approximately 10% of multiple myelomas, the initiating oncogenic event is translocation of musculoaponeurotic fibrosarcoma oncogene homolog (MAF), a transcriptional activator of key target genes, including cyclinD2. Our prior work showed that MAF is up-regulated in an additional 30% of multiple myeloma cases. The present study describes a common mechanism inducing MAF transcription in both instances. The second mode of MAF transcription occurred in myelomas with multiple myeloma SET domain (MMSET) translocation. MMSET knockdown decreased MAF transcription and cell viability. A small-molecule screen found an inhibitor of mitogen-activated protein kinase kinase (MEK), which activates extracellular signal-regulated kinase (ERK)-MAP kinases, reduced MAF mRNA in cells representing MMSET or MAF subgroups. ERK activates transcription of FOS, part of the AP-1 transcription factor. By chromatin immunoprecipitation, FOS bound the MAF promoter, and MEK inhibition decreased this interaction. MEK inhibition selectively induced apoptosis in MAF-expressing myelomas, and FOS inactivation was similarly toxic. Reexpression of MAF rescued cells from death induced by MMSET depletion, MEK inhibition, or FOS inactivation. The data presented herein demonstrate that the MEK-ERK pathway regulates MAF transcription, providing molecular rationale for clinical evaluation of MEK inhibitors in MAF-expressing myeloma.

Adoptive T cell therapy (ACT) has produced impressive responses in a subset of patients with advanced malignancies. However, majority of patients still failed to respond. Thus, there is an urgent need to understand the resistant mechanisms in non-responders and develop more effective ACT strategies. Here, we employed two independent and unbiased approaches to identify novel molecular determinants of immune resistance. We generated gene expression profiles on an immune resistant melanoma cell line to identify alternative immunosuppressive mechanisms. In addition, we utilized a new high-throughput shRNA screening platform developed by our group to functionally interrogate immune resistance in patient-derived melanoma cells. Results from both analyses implicated tumor-associated glycolysis as a critical pathway that enables tumor cells to evade T cell-mediated antitumor activity. By using samples from melanoma and non-small cell lung cancer patients, we showed that increased expression of glycolysis-related genes is associated with poor T cell infiltration of tumors. Moreover, we found that increasing tumor glycolysis impaired T cell killing of melanoma cells, while inhibiting glycolysis restored T cell-mediated apoptosis of tumor cells. More importantly, from two non-overlapping ACT-treated patient cohorts, we discovered that tumor glycolytic activity in patients who experienced disease progression following ACT was significantly higher compared to those patients who were responsive to therapy. Taken together, our results demonstrate that tumor glycolytic metabolism is associated with the efficacy of ACT and identify glycolysis as a candidate target for combinatorial therapeutic intervention.

Fludarabine, the current standard treatment for B-cell chronic lymphocytic leukemia (CLL), can induce apoptosis in CLL cells in vitro, and a number of molecular mechanisms contribute to its cytotoxicity. Using gene expression profiling, we investigated the molecular consequences of fludarabine treatment of patients with CLL in vivo. In 7 patients with CLL, a consistent gene expression signature of in vivo fludarabine exposure was identified. Many of the fludarabine signature genes were known p53 target genes and genes involved in DNA repair. In vitro treatment of CLL cells with fludarabine induced the same set of genes as observed in vivo, and many of these genes were also induced by in vitro exposure of CLL cells to ionizing radiation. Using isogenic p53 wild-type and null lymphoblastoid cell lines, we confirmed that many of the fludarabine signature genes were also p53 target genes. Because in vivo treatment with fludarabine induces a p53-dependent gene expression response, fludarabine treatment has the potential to select p53-mutant CLL cells, which are more drug resistant and associated with an aggressive clinical course. These considerations suggest that fludarabine treatment should be given in strict accordance to the current National Cancer Institute (NCI) guidelines that have established criteria of disease activity that warrant treatment.

The presence or absence of somatic mutations in the expressed immunoglobulin heavy chain variable regions (IgVH) of chronic lymphocytic leukemia (CLL) cells provides prognostic information. Patients whose leukemic cells express unmutated IgVH regions (Ig-unmutated CLL) often have progressive disease, whereas patients whose leukemic cells express mutated IgVH regions (Ig-mutated CLL) more often have an indolent disease. Given the difficulty in performing IgVH sequencing in a routine diagnostic laboratory, this prognostic distinction is currently unavailable to most patients. Pilot gene expression profiling studies in patients with CLL identified genes that were differentially expressed between the Ig-unmutated and Ig-mutated CLL subtypes. Here, we have profiled an expanded cohort of 107 patients and show that ZAP-70 is the gene that best distinguishes the CLL subtypes. Ig-unmutated CLL expressed ZAP-70 5.54fold more highly than Ig-mutated CLL (P < 10-21). ZAP-70 expression correctly predicted IgVH mutation status in 93% of patients. ZAP-70 expression and IgVH mutation status were comparable in their ability to predict time to treatment requirement following diagnosis. In 7 patients, ZAP-70 expression and IgVH mutation status were discordant: 4 Ig-mutated CLLs had high ZAP-70 expression and 3 Igunmutated CLLs had low ZAP-70 expression. Among these ZAP-70 “outliers,” those with Ig-mutated CLL had clinical features that are uncharacteristic of this CLL subtype: 2 required early treatment and 2 used a mutated VH3-21 gene, an IgVH gene that has been associated with progressive disease. We developed reverse transcriptase‐polymerase chain reaction and immunohistochemical assays for ZAP-70 expression that can be applied clinically and would yield important prognostic information for patients with CLL. (Blood. 2003;101:4944-4951)

Gene expression profiling using DNA microarrays has great potential to improve the understanding, diagnosis, and management of lymphomas, leukemias, and other malignancies. Gene expression profiling studies of diffuse large B-cell lymphoma (DLBCL) have shown that this diagnostic category encompasses at least two molecularly distinct diseases, differing in differentiation stage (cell of origin), oncogenic mechanisms, and clinical outcome. Gene expression profiling revealed that the antiapoptotic NF-kappaB pathway is constitutively active in one DLBCL subgroup, termed activated B cell-like DLBCL, and subsequent studies validated NF-kappaB as a therapeutic target in this type of lymphoma. DNA microarray studies of chronic lymphocytic leukemia (CLL) have led to a gene expression-based predictor that identifies two subtypes of CLL that differ with respect to clinical course and presence of immunoglobulin gene mutations in the CLL cells. These findings underscore the value of gene expression profiling in defining subtypes within the lymphoid malignancies that are molecularly and clinically distinct and argue that this genomic technology should become an integral part of prospective clinical trials.

Leukemia cells are protected from chemotherapy-induced apoptosis by their interactions with bone marrow mesenchymal stromal cells (BM-MSCs). Yet the underlying mechanisms associated with this protective effect remain unclear. Genome-wide gene expression profiling of BM-MSCs revealed that coculture with leukemia cells upregulated the transcription of genes associated with nuclear factor (NF)-κB signaling. Moreover, primary BM-MSCs from leukemia patients expressed NF-κB target genes at higher levels than their normal BM-MSC counterparts. The blockade of NF-κB activation via chemical agents or the overexpression of the mutant form of inhibitor κB-α (IκBα) in BM-MSCs markedly reduced the stromal-mediated drug resistance in leukemia cells in vitro and in vivo. In particular, our unique in vivo model of human leukemia BM microenvironment illustrated a direct link between NF-κB activation and stromal-associated chemoprotection. Mechanistic in vitro studies revealed that the interaction between vascular cell adhesion molecule 1 (VCAM-1) and very late antigen-4 (VLA-4) played an integral role in the activation of NF-κB in the stromal and tumor cell compartments. Together, these results suggest that reciprocal NF-κB activation in BM-MSCs and leukemia cells is essential for promoting chemoresistance in the transformed cells, and targeting NF-κB or VLA-4/VCAM-1 signaling could be a clinically relevant mechanism to overcome stroma-mediated chemoresistance in BM-resident leukemia cells.

Background: Diffuse large B cell lymphoma (DLBCL) is the most common subtype of non-Hodgkin lymphoma (NHL) and approximately 30% of the patients develop relapsed/refractory disease that becomes a major cause of mortality and morbidity. Several reports indicated that the BTK inhibitor ibrutinib successfully blocks B-cell receptor signaling and shows clinical benefit in leukemia and lymphomas, including mantle cell lymphoma [23422267] and DLBCL [26193343], for which ibrutinib is FDA-approved. In phase I/II clinical trials, ibrutinib elicited an overall response rate of 68% in patients with relapsed/refractory MCL. However, in spite of these encouraging results, responses are variable and generally incomplete, acquired resistance is common, and recurrence is anticipated [26430726]. We undertook a study of factors underlying acquired ibrutinib resistance (IR) in initially ibrutinib-sensitive DLBCL cell lines. Methods: IR DLBCL cell lines were generated by continuous culture of parental (PT) cell lines in increasing concentrations of ibrutinib, up to a maximum concentration of 10µM. Once established, IR cell lines were removed from ibrutinib, expanded, and cultured under the same conditions as the PT cell lines for further experiments. Gene expression profiling (GEP) of IR and PT populations was performed on Agilent 4 x 44K gene microarrays. Results: Of five ABC DLBCL cell lines tested, two (OCI-LY3, U2932) were initially resistant to ibrutinib (IC50>10µM).Three (TMD8, OCI-LY10, HBL1) were initially sensitive (IC50 < 10 nM), but chronic exposure to ibrutinib generated syngeneic versions with IC50 > 5µM. In comparison to PT versions of these cell lines, IR cells did not form clumps in suspension cultures, displayed irregular cell morphology, elevated colony formation ability in methylcellulose matrix, and had higher proliferation rate. Western blots and GEP data showed increased expression by IR cell lines of IAP family members survivin, cIAP2, and oncogenic BCL2 and BCL6. Reduced B-cell receptor signaling, and enhanced PI3K-Akt activity was identified in IR cell lines. Analysis of PI3K isoforms revealed up-regulation of PI3Kα and PI3Kβ with decreased expression of PI3Kδ and PTEN (PI3K negative regulator). Given the enhanced PI3K isoform expression with IR, we treated cell lines with KA2237, a PI3Kβ/δ isoform targeting drug, and observed reduced metabolic activity (survival) of IR cells compared to PT cell lines. Conclusion: This study highlights that changes in a regulator (PTEN) and mediator (p110β) of PI3K/AKT signaling have important roles in the development of ibrutinib resistance in DLBCL. Treatment with KA2237 may provide a better outcome for ibrutinib-resistant DLBCL. Disclosures Samaniego: Karus Therapuetics: Research Funding.

Background: Molecular characterization of tumors currently relies in large part on invasive tissue biopsies, which can often be unavailable or limiting. For example, while biological heterogeneity between diffuse large B-cell lymphoma (DLBCL) patients can be stratified using classification of cell-of-origin (COO), current methods relying on tumor gene expression profiles (GEP) or multi-parametric immunohistochemistry (IHC) require adequate tissue, and can be hampered by modest accuracy and reproducibility. Circulating tumor DNA (ctDNA) is an emerging noninvasive biomarker for tumor detection with potential for DLBCL disease monitoring. Here, we evaluated the utility ofctDNA for COO classification of patients with DLBCL. Methods: We previously built and trained a novel DLBCL COO Naive Bayesian classifier, using somatic alterations in 32 genes and associated with COO subtypes that were previously classified by Affymetrix mRNA GEP of frozen tumors (n=142 Training; Scherer et al., ASH Annual Meeting 2015 / ASCO Annual Meeting 2016). Here, we applied CAPP-Seq, a capture-based targeted high-throughput sequencing (HTS) method (Newman et al., Nat Med 2014), to genetically profile and classify 146 DLBCL patients in independent cohorts. We employed a test/validation framework (n=76 Test, n=70 Validation) to classify patients diagnosed and treated at Stanford University, MD Anderson Cancer Center, or at the University of Eastern Piedmont, Italy. We compared COO classification from pre-treatment plasma samples (n=119), tumor biopsy tissues (n=82, of which 71% were from FFPE), or both (n=41) against the current clinical standard immunohistochemistry method (Hans algorithm, n=117). Kaplan Meier analyses and Cox proportional-hazard models were used to assess clinical utility of biopsy-free and tumor genotyping for prediction of clinical outcomes from time of DLBCL diagnosis. Results: Genotyping of both test and validation cohorts using either tumor or plasma samples allowed COO classification in 100% of patients (GCB=77 / non-GCB=69) with 77% overall concordance to blinded and centralized Hans IHC classification. As expected, histologically transformed (tFL/DLBCL) and double-hit DLBCLs (MYC and BCL2/BCL6 translocated) were strongly biased toward GCB DNA subtype (26/29, 90%), while primary central nervous system lymphomas were almost invariably classified as ABC/non-GCB by ctDNA (6/7, 87%). The concordance between DNA-based COO classification from tumor vs. plasma was 88% (36/41). In the test cohort, COO classification by genotyping from either tissue or plasma was significantly associated with PFS (P=0.003 and 0.02, respectively, Cox proportional-hazard), while classification by Hans criteria failed to show a significant survival difference (P=0.25). The superior outcome of patients with GCB DNA COO subtype was validated when extended to the full cohort (P=0.02, Cox proportional-hazard; P=0.03, log-rank (Figure 1)). We observed a similar, albeit not significant, trend for overall survival. Conclusions: DLBCL COO subtypes can be accurately classified using somatic alterations detectable as circulating tumor DNA. We envision that this approach might help overcome some of the limitations of mRNA GEP and protein/IHC-based methods, including the requirement for invasive biopsies, tissue availability, and suboptimal assay performance. Furthermore, this strategy could support future clinical trials in helping to identify poor-risk groups at diagnosis, to guide future therapy selection, and to improve treatment decisions for patients with DLBCL. Figure 1. Figure 1. Disclosures Newman: Roche: Consultancy. Lovejoy:Roche: Employment. Levy:Kite Pharma: Consultancy; Five Prime Therapeutics: Consultancy; Innate Pharma: Consultancy; Beigene: Consultancy; Corvus: Consultancy; Dynavax: Research Funding; Pharmacyclics: Research Funding. Gaidano:Janssen: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau; Morphosys: Consultancy, Honoraria; Karyopharm: Consultancy, Honoraria; Roche: Consultancy, Honoraria, Speakers Bureau. Diehn:Roche: Consultancy; Novartis: Consultancy; Quanticel Pharmaceuticals: Consultancy; Varian Medical Systems: Research Funding. Alizadeh:Gilead: Consultancy; Celgene: Consultancy; Genentech: Consultancy; Roche: Consultancy.

Introduction: Diffuse large B-cell Lymphoma (DLBCL) is the most common lymphoid cancer in the United States with 30K diagnoses each year. The standard therapy for all newly diagnosed patients is rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone (RCHOP) which cures ~60% of patients. Lenalidomide (L) and obinutuzumab (O) have both shown promising efficacy and acceptable toxicity in DLBCL patients. Obinutuzumab, a humanized CD20 monoclonal antibody with increased pre-clinical affinity to the FcGRIIIa receptor in comparison to rituximab, may have increased antibody dependent cell-mediated cytotoxicity (ADCC). Lenalidomide, a potent immunomodulatory, is toxic to DLBCL via interferon signaling stimulation. As single agents, O and L achieve overall response rates (ORR) of 32% and 28%, respectively, in patients with relapsed DLBCL (Morschhauser, 2013, Hernandez-Ilizaliturri, 2011). The addition of L to RCHOP may overcome adverse outcomes of the non-germinal center (non-GCB) subtype of DLBCL. Randomized phase III clinical trials evaluating RCHOP +/- Len in non-GCB DLBCL are highly anticipated. The GOYA study found RCHOP was as effective as OCHOP in patients with unselected newly diagnosed DLBCL. We hypothesize the combination of OL-CHOP will result in enhanced NK cell-mediated cytotoxicity, down-regulation of interferon regulatory factor 4, and a complete response (CR) rate ≥ to OCHOP (57% in GOYA trial, Vitolo et al, ASH 2016). Methods: Newly diagnosed, CD20+ DLBCL patients were eligible if they have measurable disease, age ≥18 years, and adequate organ function. In the Phase Ib trial, Obinutuzumab was dosed at 1000mg IV days (d) 1, 8, and 15 during cycle 1, and d 1 on cycles 2-6. Lenalidomide dose was 15mg d 1 - 14 cycles 1 - 6 in the first cohort, with lower dose cohorts if toxicities occurred, using a 3+3 design. CHOP was dosed in standard fashion. Once the maximum tolerated dose (MTD) was identified, phase II was initiated with a planned total of at least 50 evaluable patients at the MTD. The primary objectives of this phase Ib/II trial were to determine the MTD and efficacy of LOCHOP. Correlative studies, including minimal disease assessment, cell of origin determination, and immune profiling are planned on blood and tumor samples. Results: Fifty three patients were enrolled, 6 in Phase Ib trial, 47 in Phase II with all evaluable for safety and 51 for efficacy. Two patients withdrew consent after 1 cycle of therapy. The median age was 62 years (26-83), with 42% males and a median IPI of 2 and NCCN IPI of 3. Five patients had double hit DLBCL, 5 patients had Double Expressor DLBCL, and 21 patients were non-GCB DLBCL. No dose limiting toxicities were identified in in Phase Ib. Toxicities encountered in PhIb include neutropenia (Grade 3: 50%, Grade 4 33%), thrombocytopenia (grade 3: 17%), and rash (grade 2: 17%), with similar findings in PhII. All six patients in PhIb achieved a complete response (CR). In the Phase II trial, 50 patients have end of therapy response assessment as of 8/2/17, with 45 with CR, 4 with partial response, 1 with progression. In the combined evaluable patients, the overall response rate is 98%, with CR of 90%. The CR rate was 90% in non-GCB and 92% in GCB. The median follow up 11 months and the median progression free and overall survival are not reached. There have been no deaths. Additional follow up and analyses will be presented at the meeting. Conclusions: The combination of Obinutuzumab, Lenalidomide, and CHOP is well tolerated, with no dose limiting toxicity encountered in the phase Ib trial, and efficacy is impressive in this single center single arm Phase Ib/II trial. Adverse events do not appear to be different than expected with standard RCHOP. Final results and correlative analyses will be presented at the ASH meeting Disclosures Westin: Apotex: Membership on an entity9s Board of Directors or advisory committees; Novartis Pharmaceuticals Corporation: Membership on an entity9s Board of Directors or advisory committees; Kite Pharma: Membership on an entity9s Board of Directors or advisory committees; Celgene: Membership on an entity9s Board of Directors or advisory committees. Nastoupil: TG Therapeutics: Honoraria, Research Funding; Gilead: Honoraria; Abbvie: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Genentech: Honoraria, Research Funding; Karus Therapeutics: Research Funding; Celgene: Honoraria, Research Funding. Neelapu: Merck: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Research Funding; Poseida Therapeutics, Inc: Research Funding; Cellectis Inc.: Research Funding; Kite Pharma: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Research Funding; Bristol-Myers Squibb: Research Funding; Karus: Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity9s Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity9s Board of Directors or advisory committees, Research Funding. Lee: KITE PHARMA: Consultancy.

Background: Diffuse large B cell lymphoma (DLBCL) is a clinically heterogeneous disease, where almost half of patients fail to fully respond to therapy and have poor outcomes. Prognostic molecular markers, including translocations in BCL2, BCL6, and MYC, can help identify patients at high risk for treatment failure. However, these markers rely on diagnostic tumor samples which must be obtained invasively and are not universally available. Circulating tumor-specific DNA (ctDNA) could provide a source of material for detection of these translocations directly from the blood. We sought to examine the performance for detection of these translocations from ctDNA, as well as their association with eventual clinical outcomes. Methods: We profiled tumor and plasma samples from patients with DLBCL receiving combination immunochemotherapy at Stanford University and MD Anderson Cancer Center. As the clinical gold standard, tumor samples were assessed with break-apart fluorescence in situ hybridization (FISH) to detect breaks in BCL2, BCL6, and MYC. DNA from tumor and plasma samples was then sequenced using CAPP-Seq, a targeted next-generation sequencing based method for detection of ctDNA (Newman AM et al, Nature Medicine 2014). Translocations were identified from paired-end reads using FACTERA (Newman AM et al, Bioinformatics 2014). We compared the technical performance of our sequencing-based approach to FISH from tumor samples. Finally, we assessed the prognostic value of our method in relation to clinical outcomes. Results: We prospectively enrolled 86 patients with DLBCL as two cohorts, either at Stanford University (n=40) or at MD Anderson Cancer Center (n=46). We first profiled tumor samples from 40 patients (Stanford cohort) for translocations using FISH as part of the clinical standard of care, identifying 24 translocations in total (12 in BCL2, 7 in BCL6, and 5 in MYC). All patients had tumor and plasma available for sequencing. By analyzing DNA from tumor samples with CAPP-Seq, we identified 92% of all translocations previously identified by FISH (11/12 BCL2, 7/7 BCL6, 4/5 MYC). Furthermore, without prior knowledge of tumor genotypes, we were able to identify 79% (19/24) translocations directly from the plasma (10/12 BCL2, 4/7 BCL6, 5/5 MYC). The performance of genotyping translocations from ctDNA improved with increasing tumor burden, such that 95% (19/20) of translocations were detected in samples with >16pg/mL (e.g. 5 genome equivalents/mL) of ctDNA. We next validated the performance of noninvasive genotyping for translocations in an independent cohort of 46 pretreatment plasma samples (MD Anderson Cancer Center cohort). In patients with detectable ctDNA, we successfully identified 78% (18/23) of translocations previously seen by FISH. Furthermore, in two patients, we detected translocations previously missed by FISH from FFPE tissue specimens (BCL6-IGH and MYC-IGH). In addition to known translocation partners, we observed several novel partner genes for MYC (e.g. PTMA and 7p15.2) and BCL6 (e.g. IRF1). Importantly, across both cohorts, we identified 82% (9/11) of patients with both MYC and BCL2/BCL6 translocations (double-hit lymphoma, DHL) directly from the plasma without knowledge of the tumor. Moreover, DHL detected noninvasively significantly predicted both progression-free and overall survival (p Conclusions: Identification of translocations from plasma without tissue samples is feasible with high sensitivity for all clinically relevant genes. Detection of translocations from plasma is prognostic of eventual outcomes, including overall survival. This technique has potential clinical utility in patients without easily accessible tissue, as well as for monitoring evolution of tumor genotypes over time. Disclosures Newman: Roche: Consultancy. Levy:Kite Pharma: Consultancy; Five Prime Therapeutics: Consultancy; Innate Pharma: Consultancy; Beigene: Consultancy; Corvus: Consultancy; Dynavax: Research Funding; Pharmacyclics: Research Funding. Westin:Celgene: Membership on an entity's Board of Directors or advisory committees; Chugai: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; ProNAi: Membership on an entity's Board of Directors or advisory committees. Diehn:Roche: Consultancy; Novartis: Consultancy; Quanticel Pharmaceuticals: Consultancy; Varian Medical Systems: Research Funding.

Background: Prompt access tosuitable hematopoietic stem cells is a prerequisite for effective allograft. Availability of HLA-matched URD &CB graftscan be a major barrier to allogeneic transplantation for minority patients. Whether this limitation is improving with increasing registry size & CB inventory is not established. Methods: From 10/2005-5/2016, we prospectively evaluated the availability of 7-8/8 HLA-allele matched URDs or 4-6/6 HLA-A,-B antigen, -DRB1 allele matched CB grafts by recipient ancestry in patients with hematologic malignancies without HLA-identical related donors. At our center, 8 HLA-allele matched URDs are given priority if available; otherwise HLA-mismatched URDs or CB grafts (predominantly double-unit) are chosen. Acceptable CB grafts have a TNC dose > 1.5 x 107/kg/unit (> 2.5 x 107/kg for single unit grafts) & 4-6/6 donor-recipient HLA-match. Results: Of the 1,112 patients, 597 (54%) received 8/8 URD & 182 (16%) received a 7/8 URD transplant, 281 (25%) underwent CB transplant (278 with double-unit grafts) & 52 (5%) had no 7-8/8 URD or CB graft. The distribution of 1,112 8/8 URD, 7/8 URD, CB transplants & no 7-8/8 URD/ CB grafts by recipient ancestry is shown (Figure). The majority (66%) of Europeans received an 8/8 URD whereas the majority of non-Europeans (60%) received either a mismatched URD or CB graft. Southern Europeans were less likely to have an 8/8 URD than other Europeans (38% vs 71%, p < 0.001). Only one-third (36%) of non-European, non-African patients had an 8/8 URD & only 12% of African ancestry patients did (p < 0.001). CB significantly extended transplant access to all patients especially southern & non-Europeans. However, over the decade,24% of African patients had no graft as compared to only 1% of European patients (p < 0.001) and 6% of non-European non-African patients (p < 0.001).When the origin of CB grafts was analyzed, we found that 68% of CB units for European ancestry patients were from domestic U.S. banks whereas in non-European non-African & African patients 72% & 84% of CB units were obtained from the US inventory, respectively (p = 0.006). To determine if donor access is improving, we then analyzed transplant type (or no URD/CB graft) by recipient ancestry in the last 4 years (recent period 5/2012-5/2016, n = 521) vs the earlier time period (10/2005-4/2012, n = 591) (Table). For this analysis, all non-southern Europeans were grouped. In recent years, disparity in graft access between ancestry groups persists. For example, in recent patients 40% of southern Europeans, 78% of other Europeans, 41% of non-African non-Europeans & only 19% of Africans received an 8/8 URD transplant (p < 0.001). Furthermore, recent no URD/CB graft rates were < 2% in all Europeans, 5% in non-European non-Africans but remained 19% in African patients (p < 0.001). Finally, comparing the recent 4 years to the earlier period, the decrease in the no URD/CB graft rate for African patients (19% vs 29%) was not significant (p = 0.212). Conclusion: Despite increasing URD registry/ CB inventory size, significant racial disparity persists in access to matched URDs. CB significantly extends transplant access especially to southern & non-European patients. In recent years, however, while 46% of African patients have received a CB graft, a significant number of these patients remain without a 7-8/8 URD or CB graft. Whilehaplo-identical donors offer an additional alternative graft source, the extension of minority patient transplant access using domestic CB units supports the importance of public CB bank funding especially for African patients and those without suitablehaplo-identical donors. Figure Distribution of 7-8/8 URD & CB transplants & no 7-8/8 URD/ CB grafts by patient ancestry. Figure. Distribution of 7-8/8 URD & CB transplants & no 7-8/8 URD/ CB grafts by patient ancestry. Table Transplant type according to patient ancestry by time period: 10/2005-4/2012 (early period) vs 5/2012-5/2016 (recent period). Table. Transplant type according to patient ancestry by time period: 10/2005-4/2012 (early period) vs 5/2012-5/2016 (recent period). Disclosures No relevant conflicts of interest to declare.

Introduction: Multiple Myeloma is a heterogeneous cancer that affects the bone marrow. Given this heterogeneity, we aimed to elucidate the role of gene expression profiling (GEP) in identifying different MM subtypes and explore their relationship to clinical outcomes in a standard of care setting. Methods: We retrospectively analyzed all NDMM patients with baseline GEP analysis. 55 patients from April 2014 until March 2016 were identified and included in our analysis. GEP was performed using CD138+ cells from bone marrow samples through MyPRS® (Signal Genetics, Little Rock, AR). Fisher's exact test was used to evaluate the associations between two categorical variables. The Wilcoxon rank sum test was used to evaluate the difference in continuous variables between patient groups. Kaplan-Meier method was used to estimate the time to event endpoints including relapse free survival (RFS) and overall survival. The log-rank test was used to evaluate the differences in the time to event endpoints between/among patient groups. Univariate Cox proportional hazards model was used to evaluate the association between a continuous variable and relapse free survival. Results: Median age was 61 (38-76). Patients presented with lytic lesions (80%), anemia (78%), kidney dysfunction (24%) and hypercalcemia (31%). One patient did not meet CRAB criteria, but had 60% plasma cells in the bone marrow and an involved/uninvolved sFLC ratio of 199. All patients were treated with bortezomib (88%) or carfilzomib (12%) initial therapy in combination with lenalidomide (83%) or cyclophosphamide (17%). All patients received triple therapy as initial treatment, with 60% of patients receiving an upfront autologous transplant. With median follow-up of 12 months (1.64-24.54 months) 75% of patients had not relapsed and median overall survival had not been reached. 13 (24%) patients were characterized as high risk (HR) by GEP. GEP risk category predicted RFS (p=0.0014) in this series of patients (Fig. 1). Table 1 shows GEP risk subtypes with clinical outcomes and association to FISH abnormalities. We previously reported that HR FISH abnormalities are present in GEP low risk (LR) patients. LR GEP patients with CKS1B gene gain by FISH (n=9, 23%) had 100% RFS at 21 months, while 60% of HR GEP patients with CKS1B gene gain had relapsed by 24 months (p=0.0297, Fig. 2). All patients with HR GEP and 17p deletion relapsed by 14 months whereas only one patient with LR GEP and 17p deletion died 1 year from diagnosis, with an unknown cause of death (p=0.18, Fig. 3). Conclusion: Cytogenetics and FISH are still the current standard of care to predict prognosis in NDMM, direct care and inclusion in clinical trials. This study in a standard of care setting shows that GEP further refines prognosis in patients with HR FISH abnormalities. Future studies in larger cohorts of patients are warranted to confirm our findings. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

Background: Diffuse large B cell lymphoma (DLBCL) is the most common type of non Hodgkin lymphoma (NHL).Nearly 50% of high-risk DLBCL patients are not cured with standard rituximab, cyclophosphamide, doxorubicin, vincristine and prednisone (RCHOP). High risk DLBCL may be defined as double hit lymphoma (DHL, translocation of MYC and BCL2 or BCL6), double expressor lymphoma (DEL, over expression of MYC and BCL2), high risk international prognostic index (IPI) of 3-5, high Ki-67, and non-germinal center subtype (non-GCB). The majority of DHL cases occur in the GCB subtype, as opposed to the majority of DEL cases which occur in non-GCB. Hence we sought to compare different high risk subsets treated with dose-adjusted etoposide, doxorubicin, cyclophosphamide, vincristine, prednisone and rituximab (DA) EPOCH-R. In single arm phase II clinical trials, dose adjusted (DA) EPOCH-R has shown promising results, with potential greater efficacy in the GCB subtype in subset analyses (Wilson et al, Hematologica 2012). A randomized phase III study comparing RCHOP with (DA) EPOCH-R in newly diagnosed DLBCL has completed accrual, with highly anticipated results due in late 2016. Methods: We conducted a retrospective reviewof all consecutive, newly diagnosed DLBCL patients treated with (DA) EPOCH-R at MD Anderson Cancer Center from 2010 to 2014. Eligible patients were 18 years or greater, had high-risk DLBCL as determined by the treating physician, and had available data of treatment and response. The cell of origin subtype was determined by immunohistochemistry using Hans algorithm, and MYC and BCL2 positivity were defined as BCL2 positive in at least 70% and MYC positive in at least 40% of cells. DHL was defined as rearrangement of MYC and BCL2 or BCL6 by fluorescent in situ hybridization. The objectives were to analyze demographic, prognostic, and treatment variables in comparison with clinical response and survival outcomes in three sub groups which included 1. DHL (GCB) 2. DLBCL without MYC and BCL2 expression (GCB), and 3. DEL (GCB and non GCB). Complete response (CR), overall survival (OS) and progression free survival (PFS) were calculated using standard methods. Statistical analysis was done using Fishers exact test or Chi-square test / Kruskal-Wallis test. Kaplan-Meier method was used for time-to-event analysis including overall survival and progression free survival. The Log-rank test was used to evaluate the difference in time-to-event endpoints between patient groups. Results: We identified 233 high risk DLBCL patients treated with (DA) EPOCH-R. After filtering the data to identify patients which were included in our three groups, we identified 22 patients with DHL (GCB), 46 patients with non DEL (GCB), and 16 with DEL. The demographic features and outcomes are mentioned in the table 1 below. The DHL group had more frequent bone marrow (BM) involvement, and the DHL and DEL groups were more frequently age >60 years and high IPI in comparison to the non DEL GCB group. The CR rate, OS and PFS at 1 year were not significantly different between these three groups. Figure 1 highlights the OS (A) and PFS (B) results of each group. Conclusions: (DA) EPOCH-R is highly effective in patients with subsets of patients with high-risk DLBCL and may be able to overcome prognostic factors which have been shown to be adverse with RCHOP therapy. The results of this retrospective study suggest that OS in DHL, DEL and non DEL (GCB) are not statistically different. Hence, intensive chemotherapy with (DA) EPOCH-R could be considered as a frontline treatment option for patients with high risk DLBCL, pending further confirmation in randomized trials. Disclosures Oki: Novartis: Research Funding. Fowler:Infinity: Consultancy, Research Funding; Roche: Consultancy, Research Funding; TG Therapeutics: Consultancy; Celgene: Consultancy, Research Funding; Jannsen: Consultancy, Research Funding; Gilead: Research Funding. Wang:Pharmacyclics: Research Funding; Juno Therapeutics: Research Funding; Acerta Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Research Funding; BeiGene: Research Funding; Kite Pharma: Research Funding; Onyx: Research Funding; Asana BioSciences: Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Fayad:Seattle Genetics: Consultancy, Research Funding. Westin:ProNAi: Membership on an entity's Board of Directors or advisory committees; Spectrum: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Chugai: Membership on an entity's Board of Directors or advisory committees.

Background: Mutational or non-mutational epigenetic events that aberrantly modify the chromatin regulatory machinery to enhance oncogene expression are a hallmark of myeloid malignancies. BRD4, a member of the bromodomain and extra terminal domain (BET) family, is a transcriptional coactivator that co-occupies super enhancer complexes associated with transcription of oncogenes (MYC, SOX2, NF-kB etc.) - and apoptosis regulators (Bcl-2, Bcl-XL, etc.) and has been validated as a target in AML therapy1. ARV-825 is a hetero-bifunctional PROteolysis TArgeting Chimera (PROTAC) that recruits BRD4 to the E3 ubiquitin ligase cereblon and leads to efficient and sustained degradation of BRD4 resulting in down-regulation of MYC2. Objectives: We examined the anti-leukemic effect of ARV-825 against AML cell lines, primary AML blasts and a mouse model of disseminated leukemia. Since tumor-stroma interactions driven by oncogene activation play a major role in resistance to AML therapy, we tested whether ARV-825 could overcome stroma-mediated drug resistance. As MYC harmonizes nutrient acquisition by cancer cells through regulation of the metabolites antiporter systems (SLC7A11, SLC5A5) 3, we profiled changes in a few important amino acids and organic acids in AML cell in response to ARV-825. Results : The IC50s for all tested cell lines and primary AML cells at 72 hours were in the low nanomolar range (2-50 nM) and 10-100 times lower than JQ1, a small molecule BRD4 inhibitor. ARV-825 induces sustained BRD4 degradation accompanied by down-regulation of targets such as MYC, anti-apoptotic BCL-2 family molecules and an increase in apoptosis and DNA damage4. In an in vitro tumor-stroma co-culture model including hypoxic conditions, bone marrow derived mesenchymal stromal cells (MSCs) protected OCI-AML3 cells from cytarabine ( 55.4% apoptosis with vs. 35.0% without MSCs in normoxia and 50.6% vs. 32.8%, respectively, in hypoxia), but no such protection was observed against ARV-825 (58.7% apoptosis vs. 55.2% in normoxia and 57.4% vs. 58.3%, respectively, in hypoxia). Mass cytometry based proteomic analysis (CyTOF) (Fig. 1), immunoblotting and flow cytometry showed that among apoptotic, cell adhesion and signaling proteins, MYC, CD44 and surface CXCR4 were the most down-regulated proteins in AML cells. The functional relevance of surface CXCR4 down regulation was confirmed in migration assays against the CXCR4 ligand SDF-1. Phosphorylation of CXCR4 by PIM1 kinase is necessary for surface expression of CXCR4, ARV-825 treatment reduced PIM1 levels and phosphorylation of CXCR4 in AML cells while overexpression of PIM1 or Myc reversed the phenomena. Quantitative PCR and immunoblotting analysis confirmed the transcriptional down regulation of total CD44 and CD44 variants 8-10 (2-fold change treated vs. untreated). As a functional correlate of CD44 variants, mass spectrometry based intracellular metabolomics and flow cytometry confirmed reduction in cysteine uptake and increased reactive oxygen species (ROS) generation (Fig. 2). Additional metabolic readouts using the Sea horse system revealed inhibition of mitochondrial respiration as indicated by decreased in oxygen consumption rate and production of ATP upon treatment of ARV-825. Furthermore, array based gene expression profiling showed down-regulation of additional amino acid transporters and the Wnt/β-catenin pathway. Finally, in a mouse model of human leukemia, the leukemia burdens were significantly lower in the ARV-825 treated mice as confirmed by luciferase imaging, flow cytometry, spleen size and survived longer compared to control mice (p=0.0005) (Fig.3). Conclusion : ARV-825 has substantial, broad anti-AML activity and importantly modulates the tumor microenvironment and metabolism to overcome stroma-mediated drug resistance. Together, our data suggest that ARV-825 is an effective in targeting BET family of proteins for the treatment of AML Reference: 1. Nature 2011; 478(7370): 524-528. doi: 10.1038/nature10334 2. Chem Biol 2015; 22(6): 755-763. doi: 10.1016/j.chembiol.2015.05.009 3. Cancer Res 2015; 75(9): 1782-1788. doi: 10.1158/0008-5472.CAN-14-3745 4. 604(675): ASH 2015,San franscisco,USA. Disclosures Lorenzi: Erytech Pharma: Consultancy, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: NIH-held patent related to L-asparaginase. Qian:Arvinas, LLC: Employment. Kantarjian:Bristol-Myers Squibb: Research Funding; ARIAD: Research Funding; Amgen: Research Funding; Pfizer Inc: Research Funding; Delta-Fly Pharma: Research Funding; Novartis: Research Funding.

Development of MDM2 inhibitors enabled successful induction of p53-mediated apoptosis in tumor cells without a risk of DNA damage. Early clinical trials of MDM2 inhibitors demonstrated proof-of-concept (Andreeff et al., Clin Can Res, 2015). However, a clinical challenge is that not all the tumors bearing wild-type TP53 are sensitive to MDM2 inhibition. We here discovered novel gene profiling-based algorithms for predicting tumor sensitivity to MDM2 inhibition, using DS-3032b, a novel potent MDM2 inhibitor, which is currently in early clinical trials. In vitro inhibitory effects of DS-3032b on MDM2-p53 interaction was demonstrated using the homogeneous time resolved fluorescence (HTRF) assay (IC50 5.57 nM). DS-3032b treatment (30-1000 nM) indeed increased p53 protein in a dose-dependent manner, and also the p53 targets MDM2 and p21, in cancer cell lines with wild-type TP53 (SJSA-1, MOLM-13, DOHH-2, and WM-115), showing around 10-fold potent growth inhibition effects compared to Nutlin-3a (Table 1). The xenograft mouse models with SJSA-1 and MOLM-13 cells showed > 90% reduction in tumor growth with oral administrations of 25 and 50 mg/kg/day. For discovering predictive gene signatures, we performed two different approaches. In the first approach, 240 cell lines available as OncoPanel were treated with DS-3032b, another prototypic MDM2 inhibitor DS-5272, and Nutlin-3a, and determined 62 sensitive and 164 resistant lines, based on GI50s. Using gene expression profiling (GEP) publicly available for all the cell lines, we selected 175 top-ranked genes with highest expression in the 62 sensitive cell lines. We thus defined the average of Z-scores of the 175 gene expression as "sensitivity score". To validate the 175-gene signature, we evaluated in vivo anti-tumor activities of DS-3032b in 13 patient-derived tumor xenografts (melanoma, NSCLC, colorectal and pancreatic cancers). The prediction accuracy, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) were 85, 88, 88 and 80% respectively. As another validation set, 41 primary AML samples were treated with DS-3032b to define the top and bottom one-third most sensitive or resistant samples (14 each), and GEP was performed in every sample. TP53 mutations were detected in 8 specimens by next generation sequencing and confirmed by Sanger sequencing. The 175-gene signature was applied to the AML dataset, and the accuracy, sensitivity, PPV and NPV to predict the 14 sensitive or resistant samples were 79, 93, 72 and 90% respectively. Importantly, this signature was more predictive than the TP53 mutation status alone applied (68, 93, 62 and 86%). (Table 2A-B) In contrast to the cell line-based approach, the second approach defined an AML-specific gene signature. Specifically, we used the same dataset of 41 primary AML samples described above as training and validation set, by performing random forest methods with cross validation. Using a routine way in bioinformatics analysis of classifying gene signature, we first selected the 1500 top-ranked genes with highest expression variance among all the specimens. In addition, p53-related 32 genes that potentially have predictive values were also selected based on the previous reports. Classification was performed using the random forest method to identify a predictive algorithm with the 1500-gene set, 32-gene set or combined 1525-gene set (7 genes were overlapped), thus we found that the 1525-gene set had highest performance than each gene set alone. However, applying this method to all the 41 samples showed inferior predictive performance than applied only to the 33 wild-type TP53 samples (the prediction accuracy, sensitivity, PPV and NPV were 68, 72, 67 and 69%, vs. 77, 82, 75 and 80%).(Table 2C) Finally, we combined each of the two algorithms (Table 2B-C) with TP53 mutation status. Specifically, the samples with TP53 mutations were predicted as resistant, then either of gene signatures was applied to the rest of the samples with wild-type TP53. Predictive performance (Table 2D-E) was improved in both signatures compared to the others, especially showing the highest PPVs (80 and 82%, respectively). Taken together, gene signatures discovered in the present study, by combining with TP53 mutation status, provided new highly predictive algorithms for therapy of MDM2 inhibition. Our findings will be tested in ongoing clinical trials of DS-3032b. Disclosures Nakamaru: Daiichi Sankyo Co., Ltd: Employment. Seki:2Daiichi Sankyo Co., Ltd.: Employment. Tazaki:2Daiichi Sankyo Co., Ltd.: Employment. DiNardo:Celgene: Research Funding; Novartis: Other: advisory board, Research Funding; Abbvie: Research Funding; Agios: Other: advisory board, Research Funding; Daiichi Sankyo: Other: advisory board, Research Funding. Tse:Daiichi Sankyo, Inc.: Employment.