Stemline Therapeutics Research Articles

Clinical Outcomes with Hypomethylating Agents in Patients with Myelodysplastic Syndrome/Myeloproliferative Neoplasm with Ring Sideroblasts and Thrombocytosis (MDS/MPN-RS-T); A Case Series

Clinical Outcomes with Hypomethylating Agents in Patients with Myelodysplastic Syndrome/Myeloproliferative Neoplasm with Ring Sideroblasts and Thrombocytosis (MDS/MPN-RS-T); A Case Series

Mutational Landscape of Relapsed Core-Binding Factor Acute Myeloid Leukemia (CBF-AML)

Mutational Landscape of Relapsed Core-Binding Factor Acute Myeloid Leukemia (CBF-AML)

Distinct Prognostic Effects of TP53 Mutations in Newly Diagnosed Versus Relapsed/Refractory (R-R) Patients (pts) with B-Acute Lymphoblastic Leukemia (ALL) Treated with Mini-Hcvd-Inotuzumab Ozogamicin with or without Blinatumomab Regimens

Distinct Prognostic Effects of TP53 Mutations in Newly Diagnosed Versus Relapsed/Refractory (R-R) Patients (pts) with B-Acute Lymphoblastic Leukemia (ALL) Treated with Mini-Hcvd-Inotuzumab Ozogamicin with or without Blinatumomab Regimens

Thrombotic Events and Mortality Risk in Patients Newly Diagnosed with Intermediate- to High-Risk Essential Thrombocythemia in the United States

Background Essential thrombocythemia (ET) is a myeloproliferative neoplasm (MPN) associated with an increased risk of thrombotic events (TEs), which represent a substantial cause of mortality in this population. There is limited contemporary, real-world evidence exploring the effect of TEs on mortality in patients with ET. The aim of this analysis was to compare risk of mortality among patients newly diagnosed with intermediate- or high-risk ET who experienced a TE vs those who did not experience a TE. Study Design and Methods All data from the Medicare Fee-for-Service (FFS) claims database (Parts A/B/D) from January 2010-December 2017 were used to identify patients with an ET diagnosis (all intermediate or high risk based on cohort age ≥65 years) with ≥1 inpatient or ≥2 outpatient claims. The index date was the date of the first qualifying ET claim. Patients with an ET diagnosis, use of hydroxyurea, or use of ruxolitinib within 12 months before the index date and patients with a myelofibrosis diagnosis during the study period were excluded. A minimum of 12 months of continuous medical and pharmacy enrollment pre-index was required. The study sample was categorized into TE and non-TE groups based on the occurrence of any of the following events during follow-up: deep vein thrombosis, pulmonary embolism, ischemic stroke, acute myocardial infarction, transient ischemic attack, peripheral arterial thrombosis, or superficial thrombophlebitis. TEs were evaluated from the index date to the end of follow-up. Cox regression analyses with time-varying effects were used to assess mortality risk among patients with ET with post-index TE as a time-dependent variable, stratified by pre-index TE, and adjusting for patient demographic characteristics and comorbid conditions. Results A total of 143,588 Medicare FFS beneficiaries with a diagnosis of ET met the study inclusion criteria; median age was 76.0 years, 68.1% were female, and 84.2% were white. Pre-index TE was reported in 37,284 patients (26.0%). In the follow-up period, 49,497 patients (34.5%) had a TE and 94,091 patients (65.5%) did not have a TE. In the comparison between the TE vs non-TE groups, the median (range) age (77 [65-107] vs 75 [65-110] years, respectively), mean (SD) Charlson comorbidity index score (4.8 [3.5] vs 3.8 [3.5]), and percentage of patients with a history of bleeding (27.0% vs 22.2%), anemia (64.7% vs 55.9%), or a cardiovascular event (45.8% vs 33.5%) were higher (Table 1). The median time from ET diagnosis to first TE in the follow-up period was 2.8 months for all patients, 0.5 months for patients with pre-index TE, and 8.0 months for those without pre-index TE. The most common types of first TE in the follow-up period were ischemic stroke (37.3%), acute myocardial infarction (23.2%), and transient ischemic attack (22.6%). The risk of mortality was increased for patients who experienced a TE compared with those who did not (hazard ratio [HR; 95% CI], 11.2 [10.6-11.8]; P<0.001), including for both those with pre-index TE (HR [95% CI], 9.3 [8.6-10.1]; P<0.001) and those without pre-index TE (HR [95% CI], 15.4 [14.2-16.8]; P<0.001). Conclusions In this contemporary, real-world analysis, approximately one-third of patients with newly diagnosed intermediate- to high-risk ET experienced a TE. Elderly patients with ET who experienced a TE had an approximately 11-fold increased risk of mortality vs those who did not experience a TE, highlighting a continued unmet need in this population. Further efforts are needed to better define and mitigate TE risk in patients with ET, particularly in those with prior TE. Disclosures Pemmaraju: Daiichi Sankyo: Research Funding; Cellectis: Research Funding; Plexxikon: Research Funding; Blueprint Medicines: Honoraria; AbbVie: Honoraria, Research Funding; Samus Therapeutics: Research Funding; Affymetrix: Other: Grant Support, Research Funding; Roche Diagnostics: Honoraria; Stemline Therapeutics: Honoraria, Research Funding; Pacylex Pharmaceuticals: Consultancy; Incyte Corporation: Honoraria; Novartis: Honoraria, Research Funding; LFB Biotechnologies: Honoraria; MustangBio: Honoraria; Celgene: Honoraria; DAVA Oncology: Honoraria; SagerStrong Foundation: Other: Grant Support. Gerds:Gilead Sciences: Research Funding; Incyte Corporation: Consultancy, Research Funding; Roche/Genentech: Research Funding; AstraZeneca/MedImmune: Consultancy; Imago Biosciences: Research Funding; Sierra Oncology: Research Funding; Celgene: Consultancy, Research Funding; Apexx Oncology: Consultancy; CTI Biopharma: Consultancy, Research Funding; Pfizer: Research Funding. Yu:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Parasuraman:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Shah:Avalere Health: Current Employment. Xi:Incyte Corporation: Other: Avalere Health is a paid consultant of Incyte Corporation; Avalere Health: Current Employment. Kumar:Incyte Corporation: Other: Avalere Health is a paid consultant of Incyte Corporation; Avalere Health: Current Employment. Scherber:Incyte Corporation: Current Employment, Current equity holder in publicly-traded company. Verstovsek:CTI Biopharma Corp: Research Funding; Protagonist Therapeutics: Research Funding; Roche: Research Funding; Incyte Corporation: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; PharmaEssentia: Research Funding; Sierra Oncology: Consultancy, Research Funding; Blueprint Medicines Corp: Research Funding; Genentech: Research Funding; AstraZeneca: Research Funding; ItalPharma: Research Funding; Promedior: Research Funding; Gilead: Research Funding; Celgene: Consultancy, Research Funding; NS Pharma: Research Funding.

Long-Term Follow-up of the Combination of Low-Intensity Chemotherapy Plus Inotuzumab Ozogamicin with or without Blinatumomab in Patients with Relapsed-Refractory Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia: A Phase 2 Trial

Long-Term Follow-up of the Combination of Low-Intensity Chemotherapy Plus Inotuzumab Ozogamicin with or without Blinatumomab in Patients with Relapsed-Refractory Philadelphia Chromosome-Negative Acute Lymphoblastic Leukemia: A Phase 2 Trial

BCL2A1: A Novel Target in Refractory Acute Myeloid Leukemia with FLT3-ITD/D835 Dual Mutations

Internal tandem duplications in the juxtamembrane domain of FMS-like tyrosine kinase 3 gene (FLT3-ITD) and missense mutations in the gene's tyrosine-kinase domain (FLT3-TKD) play critical roles in the pathophysiology of acute myeloid leukemia (AML). Recent study revealed that AML cells resistant to quizartinib, a type II TKI, consist of heterogeneous clonal populations harboring wild-type FLT3 as well as FLT3-ITD, FLT3-TKD and FLT3-ITD/TKD mutations, and on- and off-target mechanisms may contribute to the resistance to TKIs. To overcome the heterogeneous resistance mechanisms of FLT3-ITD and TKD mutations, various combinatorial therapies have been investigated. For example, BCL-2 inhibition in the presence of TKIs increased survival a murine FLT3-ITD AML model, and a phase Ib/II clinical trial of a combination of quizartinib with venetoclax, a BCL2 inhibitor is ongoing in relapsed/refractory FLT3-mutant AML patients (NCT03735875). To dissect underlying mechanisms of drug-resistance and exploring new targets in refractory AML with FLT3-ITD and TKD mutations, we investigated alterations of transcriptome signatures by analyzing AML samples with FLT3-ITD/D835 dual mutations. Previously, we reported BCL2A1 transcriptomes were upregulated in primary AML cells with FLT3-ITD/D835 dual mutations compared to cells with FLT3-ITD mutations only. This was recapitulated in the MV4-11 cells harboring FLT3-ITD/D835 dual mutations after 6 month-exposure to quizartinib. The MV4-11 cells with the FLT3-ITD/D835 dual mutations became resistant to quizartinib, and the cells also became resistant to venetoclax, a BCL2 inhibitor (Yamatani et al. ASH 2019). In this study, we further investigated BCL2A1 as new target in refractory AML with FLT3-ITD/D835 dual mutations. First, we examined whether overexpression of BCL2A1 induces drug-resistance in MV4-11 and Molm13 cell lines with FLT3-ITD. While parental MV4-11 and Molm13 cells are sensitive to venetoclax and quizartinib, MV4-11 and Molm13 cells transfected with lentivirus carrying BCL2A1 became resistant to venetoclax (IC50: MV4-11 with BCL2A1 over-expression >1000 nM vs. mock vector 0.71 nM; Molm13 with over-expression >1000 nM vs. mock vector 0.38 nM, 72h). In contrast, the sensitivity to quizartinib was retained in the BCL2A1 overexpressing MV4-11 and Molm13 cells. These findings indicate that the overexpression of BCL2A1 could play a role in the acquired resistance to venetoclax, but not to quizartinib. Bromodomain-containing protein 4 (BRD4), a family member of bromodomain and extra-terminal motif (BET) is known to transcriptionally modulate BCL2A1 gene expression. Next, we examined effects of CPI-0610, a BET inhibitor, on MV4-11 cells with FLT3-ITD or the FLT3-ITD/D835 dual mutation. CPI-0610 inhibited cell growth of MV4-11 cells by inducing apoptosis irrespective of co-existing FLT3 mutations (IC50: FLT3-ITD/D835, 255 nM vs. FLT3-ITD, 191 nM, 72h). Immunoblotting analyses confirmed that BET inhibition by CPT-0610 decreased the expression of BCL2A1 in MV4-11 cells FLT3-ITD/D835. WIn conclusion, transcriptome analysis and molecular pharmacological approaches identified alterations in the anti-apoptotic BCL2 family proteins in double-mutant FLT3 leukemias. BCL2A1 upregulation might be involved in drug resistance of FLT3-ITD/D835 dual mutant AML cells, and could be a promising new target in refractory AML with FLT3-ITD/D835 dual mutations. Disclosures Konopleva: Cellectis: Research Funding; Eli Lilly: Research Funding; Calithera: Research Funding; Sanofi: Research Funding; Ascentage: Research Funding; AstraZeneca: Research Funding; Agios: Research Funding; Stemline Therapeutics: Consultancy, Research Funding; Kisoji: Consultancy; Genentech: Consultancy, Research Funding; F. Hoffmann La-Roche: Consultancy, Research Funding; Forty-Seven: Consultancy, Research Funding; 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; Rafael Pharmaceutical: Research Funding; Ablynx: Research Funding; Amgen: Consultancy. Carter:Syndax: Research Funding; AstraZeneca: Research Funding; Amgen: Research Funding; Ascentage: Research Funding. Andreeff: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; Daiichi-Sankyo; Jazz Pharmaceuticals; Celgene; Amgen; AstraZeneca; 6 Dimensions Capital: Consultancy.

Characteristics and Outcome of Myelofibrosis Patients on Long-Term Ruxolitinib Therapy (≥3 years)

Characteristics and Outcome of Myelofibrosis Patients on Long-Term Ruxolitinib Therapy (≥3 years)

The Addition of Navitoclax to Ruxolitinib Demonstrates Efficacy within Different High-Risk Populations in Patients with Relapsed/Refractory Myelofibrosis

The Addition of Navitoclax to Ruxolitinib Demonstrates Efficacy within Different High-Risk Populations in Patients with Relapsed/Refractory Myelofibrosis

Development of TP53 Mutations over the Course of Acute Myeloid Leukemia Therapy

Development of TP53 Mutations over the Course of Acute Myeloid Leukemia Therapy

Single-Cell Characterization of Acute Myeloid Leukemia (AML) and Its Microenvironment Identifies Signatures of Resistance to PD-1 Blockade Based Therapy

Single-Cell Characterization of Acute Myeloid Leukemia (AML) and Its Microenvironment Identifies Signatures of Resistance to PD-1 Blockade Based Therapy

IDH Mutations Are Associated with an Increased Risk of Coronary Artery Disease and Cardiotoxicity in Patients with Established AML

Introduction: Clonal hematopoiesis initiated by acquired somatic mutations in hematopoietic cells has been identified as an independent driver of increased all-cause mortality, risk of coronary artery disease and heart failure. Oncogenic mutations in isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2) lead to conversion of αKG to R-2-hydroxyglutarate (R-2HG), which is a competitive inhibitor of TET2 and a known oncometabolite. Oncometabolite R-2HG (produced by IDH mutant cells) has been implicated in pathological cardiac remodeling and dysfunction in preclinical studies. Whether IDH mutant leukemic cells in patients with established AML are also associated with the development of cardiovascular diseases or exacerbate cardiotoxicity during anthracycline containing chemotherapy is still unknown. Methods: In this observational study, a propensity score-based analysis was performed in 363 adult AML patients being stratified by mutation status in the IDH gene. To analyze whether the IDH mutation status in AML patients was associated with increased cardiotoxicity, we analyzed echocardiographic left ventricular ejection fraction (LVEF) in the control group (AML patients without IDH mutation) and the exposed group (AML patients with IDH mutation) at baseline and at different time points during AML therapy. Results: IDH 1 and IDH2 mutations occurred in 26 (7.2%) and 39 adult AML patients (10.7%), respectively. The median age of the total population was 60 years. The estimated 2-year relapse-free survival and overall survival rates in the overall study cohort were 49.4% (5-year RFS 38.9%) and 59.2% (5-year OS 43.1%) during a median follow-up of 7.6 years. IDH1 mutant AML patients exhibited a significantly higher prevalence of coronary artery disease (26.1% vs. 6.4%, p=0.002). A propensity score analysis by inverse probability-weighting was performed based on the 295 patients who received intensive cytarabine and anthracycline-containing chemotherapy. This analysis revealed an increased risk for a declining cardiac function during AML treatment in IDH1/2 mutated compared to IDH1/2 wild type patients [LVEF pretreatment compared to 10 months after diagnosis: 59.2% to 41.9% (P<0.001) vs 58.5% to 55.4% (P=0.27), respectively], suggesting that the IDH mutations in AML patients were associated with a declining cardiac function during AML therapy, which was independent of measured baseline characteristics. To validate whether the oncometabolite R-2HG drives vulnerability of cardiac cells in patients with IDH mutant AML, human iPS-derived cardiomyocytes were exposed to R-2HG (or control) during anthracycline treatment. Indeed, an exaggerated sarcomere disarray when R-2HG was added to anthracycline treatment was identified by immunostaining in human induced pluripotent stem cell (hIPS) derived cardiomyocytes. By RNA sequencing of R-2HG exposed hiPS-derived cardiomyocytes during anthracycline treatment, we demonstrate the transcriptomic basis for putative biological processes mediating the increased cardiotoxicity. Conclusion: The presence of an IDH mutation in adult AML was associated with a higher prevalence of coronary artery disease and an exacerbated cardiotoxicity during anthracycline treatment, which was at least in part mediated by the oncometabolite R-2HG. Disclosures Thol: Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees. Ganser:Novartis: Consultancy; Celgene: Consultancy. Heuser:BerGenBio ASA: Research Funding; Roche: Research Funding; Astellas: Research Funding; Janssen: Consultancy; Abbvie: Consultancy; Pfizer: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Amgen: Research Funding; PriME Oncology: Honoraria; Daiichi Sankyo: Consultancy, Research Funding; Stemline Therapeutics: Consultancy; Bayer: Consultancy, Research Funding; Karyopharm: Research Funding.

Next-Generation Sequencing (NGS)-Based Measurable Residual Disease (MRD) Monitoring in Acute Myeloid Leukemia with FLT3 Internal Tandem Duplication (FLT3-ITD+ AML) Treated with Additional Midostaurin

Next-Generation Sequencing (NGS)-Based Measurable Residual Disease (MRD) Monitoring in Acute Myeloid Leukemia with FLT3 Internal Tandem Duplication (FLT3-ITD+ AML) Treated with Additional Midostaurin

Prognostic Significance of Genetic Alterations in Patients with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia Treated with Hyper-CVAD Plus Dasatinib or Hyper-CVAD Plus Ponatinib

Prognostic Significance of Genetic Alterations in Patients with Philadelphia Chromosome-Positive Acute Lymphoblastic Leukemia Treated with Hyper-CVAD Plus Dasatinib or Hyper-CVAD Plus Ponatinib

Higher Dose of CPX-351 Is Associated with Prolonged Hematologic Recovery: Results from an Interim Safety Analysis of the Randomized, Phase III AMLSG 30-18 Trial

Higher Dose of CPX-351 Is Associated with Prolonged Hematologic Recovery: Results from an Interim Safety Analysis of the Randomized, Phase III AMLSG 30-18 Trial

Long-Term Outcome of Low-Dose Hypomethylating Agents in Lower-Risk Myelodysplastic Syndromes: A Randomized Phase 2 Study

Long-Term Outcome of Low-Dose Hypomethylating Agents in Lower-Risk Myelodysplastic Syndromes: A Randomized Phase 2 Study

Activity of Decitabine (DAC) Combined with All-Trans Retinoic Acid (ATRA) in Oligoblastic AML: Subgroup Analysis of a Randomized 2x2 Phase II Trial

Activity of Decitabine (DAC) Combined with All-Trans Retinoic Acid (ATRA) in Oligoblastic AML: Subgroup Analysis of a Randomized 2x2 Phase II Trial

CD22 Expression Level As a Predictor of Survival in Patients (Pts) with Relapsed/Refractory (R-R) Acute Lymphoblastic Leukemia (ALL) Treated with Inotuzumab Ozogamicin (INO) in Combination with Low-Intensity Chemotherapy (mini-hyper-CVD) with or without Blinatumomab: Results from a Phase 2 Study

CD22 Expression Level As a Predictor of Survival in Patients (Pts) with Relapsed/Refractory (R-R) Acute Lymphoblastic Leukemia (ALL) Treated with Inotuzumab Ozogamicin (INO) in Combination with Low-Intensity Chemotherapy (mini-hyper-CVD) with or without Blinatumomab: Results from a Phase 2 Study

Immunophenotypic Lineage Assessment By Multiparameter Flow Cytometry Provides More Precise MDS Prognosis

Background: Mixed phenotype acute leukemia is a rare disease characterized by an expanded blast population exhibiting multiple lineage features. It is a diagnosis of exclusion, and we and others have observed that AML-MRC or therapy-related AML cases may also exhibit similar features. We therefore sought to determine whether multi-lineage expression is present in de-novo and therapy-related MDS and whether it has an impact on clinical outcomes. Methods: We reviewed pathology, flow cytometry, cytogenetic, and molecular reports from patients seen at Memorial Sloan Kettering Cancer Center between 1996 and 2020 and identified 472 patients diagnosed with MDS using a combination of custom natural language processing tools and manual review. Cox proportional hazards modeling was performed to assess the contribution of patient characteristics, pathology, flow cytometric, cytogenetic, and molecular characteristics to overall survival (OS). Fisher's exact testing was used to assess the association of individual features. Results: We found that an abnormal myeloid lineage signature was associated with poorer OS after adjusting for age, cytogenetics, and molecular features (HR=2.3, p<0.01). In contrast, an abnormal plasma cell signature was associated with better OS (HR=0.3, p<0.01) (Figure A). Other abnormal lineages did not contribute significantly to OS although there were relatively few cases with abnormal T-cell markers (n=19). Mutations in TP53, IDH1, and EZH2 were associated with poorer OS (TP53: HR=1.5, p<0.01; IDH1: HR=2.3, p<0.01, EZH2: HR=1.9, p<0.01) and mutations in SF3B1 and IDH2 were associated with better OS (SF3B1: HR=0.35, p<0.01; IDH2: HR=0.6, p=0.05) (Figure B). TP53 mutation was enriched among patients with intermediate and poor risk cytogenetic groups (OR=11.3, p<0.01), consistent with higher risk therapy-related disease. IDH2, TET2, and ASXL1, which have been associated with clonal hematopoiesis, were enriched in the good and intermediate risk cytogenetic groups (IDH2: OR=4.3; p=0.03, TET2: OR=3.7, p<0.01; ASXL1: OR=4.3, p<0.01), although only IDH2 had a significant association with OS. Interestingly, there was a significant association of plasma cell lineage abnormalities with SRSF2 mutation (OR=3.5, p=0.05), but SRSF2 mutation was not an independent contributor to the global survival model (Figure C). Conclusion: Routine flow cytometric and molecular assessment of diagnostic bone marrows can provide added prognostic value in MDS. Identification of an abnormal myeloid lineage is associated with higher risk disease, while identification of abnormal plasma cell features is associated with lower risk disease. SRSF2 mutation is also associated with abnormal plasma cell features, but does not contribute independently to OS. Abnormal T-cell features may also provide prognostic value, although assessment in a larger cohort will be necessary. We confirm previous findings indicating that TP53 mutation is associated with higher risk disease while SF3B1 mutation is associated with better outcomes characteristic of MDS-RARS. In addition, our data suggests that IDH1 and EZH2 are associated with poorer outcomes and that IDH2 is associated with lower risk disease. Figure 1 Disclosures Tallman: Bioline rx: Membership on an entity's Board of Directors or advisory committees; Delta Fly Pharma: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Abbvie: Research Funding; Cellerant: Research Funding; Orsenix: Research Funding; ADC Therapeutics: Research Funding; BioSight: Membership on an entity's Board of Directors or advisory committees, Research Funding; Glycomimetics: Research Funding; Rafael: Research Funding; Oncolyze: Membership on an entity's Board of Directors or advisory committees; UpToDate: Patents & Royalties; Novartis: Membership on an entity's Board of Directors or advisory committees; Roche: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Daiichi-Sankyo: Membership on an entity's Board of Directors or advisory committees; KAHR: Membership on an entity's Board of Directors or advisory committees; Rigel: Membership on an entity's Board of Directors or advisory committees. Levine:Morphosys: Consultancy; Astellas: Consultancy; Janssen: Consultancy; Lilly: Consultancy, Honoraria; Isoplexis: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; C4 Therapeutics: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Imago: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Loxo: Current equity holder in private company, Membership on an entity's Board of Directors or advisory committees; Qiagen: Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees; Prelude Therapeutics: Research Funding; Gilead: Honoraria; Novartis: Consultancy; Amgen: Honoraria; Roche: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding. Xiao:Stemline Therapeutics: Research Funding. Glass:Gerson Lehman Group: Consultancy.

LSD1 Inhibitor CPI-482 Shows Efficacy and Prolongs Survival in Mouse Models of AML and Post-MPN AML in the Context of Constitutive JAK-STAT Pathway Activation

LSD1 Inhibitor CPI-482 Shows Efficacy and Prolongs Survival in Mouse Models of AML and Post-MPN AML in the Context of Constitutive JAK-STAT Pathway Activation

Overexpression of CD200 Is a Stem Cell-Specific Mechanism of Immune Escape in AML

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.