Indirect Treatment Comparison of CC-486 Versus Azacitidine (AZA) As Maintenance Therapy for Acute Myeloid Leukemia (AML)

Introduction: For medically fit patients with AML, intensive chemotherapy (IC) is used to induce complete remission (CR). Following CR, some patients may be considered for curative-intent hematopoietic stem cell transplantation. For others, the aim of treatment is to prevent relapse, which usually occurs within 1 year from CR. Post CR, treatment may include consolidation therapy, consisting of chemotherapy given soon after CR is achieved. In addition, maintenance therapy with intravenous (IV) or subcutaneous (SC) injection of AZA has shown evidence of statistically significant improvement in unadjusted time to relapse, though not in unadjusted overall survival (OS), vs placebo (PBO) in randomized controlled trials (RCTs) (Wei. 2019). In the QUAZAR AML-001 trial, maintenance with CC-486, an oral hypomethylating agent, resulted in significant improvements in unadjusted time to relapse and OS vs PBO (Wei et al. 2019). No head-to-head trials have compared CC-486 with AZA. Objective: To assess the relative efficacy of CC-486 compared with AZA. Methods: A systematic literature review was conducted to identify RCTs assessing AML maintenance therapy with AZA, for comparison with CC-486. Bayesian network meta-analysis (NMA) compared endpoints of CC-486 and AZA. Hazard ratios (HR), 95% credible intervals (CrI), and surface under the cumulative ranking curve (SUCRA) values were calculated. The impact of differences in potential treatment-effect-modifying characteristics between populations in the NMA was explored using anchored matching-adjusted indirect comparison (MAIC). The NMA was repeated using CC-486 vs PBO efficacy from the MAIC, to satisfy the assumption of clinical similarity necessary in NMA (Hoaglin et al. 2011). Results: Four RCTs evaluating OS outcomes that could be compared were identified: QUAZAR AML-001 (CC-486) (Wei et al. 2019), HOVON 97 AML (SC AZA) (Huls et al. 2019), UK NCRI AML16 (SC AZA) (Burnett et al. 2015), and QoLESS-AZA-MLE (SC and IV AZA, included in sensitivity analysis) (Oliva et al. 2019). Other efficacy and safety endpoints were not analyzed owing to lack of comparable data among the 4 identified RCTs. Results of the NMA indicated CC-486 was associated with statistically significant improvement in OS vs SC AZA (HR 0.744; CrI 0.557, 0.998); SC AZA was not statistically different from PBO (HR 0.926; CrI 0.771, 1.120). SUCRA values associated CC-486 with the best OS (98.8%). In a sensitivity analysis, CC-486 was associated with statistically significant improvement in OS vs SC or IV AZA (HR 0.741; CrI 0.556, 0.992). In the MAIC, a structured process was used to evaluate the need for adjustment due to differences in trial populations in the NMA. Populations for each trial were compared (Table). Per methodological guidance (Phillippo et al. 2016), the MAIC sought to adjust characteristics with evidence of (a) treatment-effect-modifying status on the scale of parameters entering the NMA and (b) substantial imbalance across populations. Using the QUAZAR individual patient data, univariate analyses were conducted to determine prognostic and effect-modifying status of variables (Table). For each SC AZA trial, a multivariate Cox model was estimated, including all significant prognostic variables reported, and effect modifiers that remained significant when controlling for prognostic variables and improved model fit. Among variables reported for UK NCRI, no effect modifiers enhanced the multivariate model; for HOVON, treatment interactions with age > 81 years (the oldest age in HOVON) and absolute neutrophil count (ANC) did. MAIC was therefore conducted by re-weighting QUAZAR patients to match means/shares of the HOVON patients, adjusting for mean age, % aged > 81 years, % poor cytogenetic risk, and mean ANC. Effective sample size was 411 (−13% vs N = 472 in QUAZAR). Frequency-weighted, unadjusted (including only a treatment covariate) Cox regression was conducted. After adjusting for effect-modifying differences, the OS improvement of CC-486 vs PBO observed in QUAZAR was maintained in the HOVON population. Incorporating the adjusted HR from the MAIC in the NMA, CC-486 continued to be associated with statistically significant improvement in OS vs SC AZA (HR 0.753; CrI 0.563, 0.998). Conclusion: Maintenance CC-486 appears to significantly improve OS compared with SC AZA for patients with AML who have achieved CR after IC, based on a systematic analysis of RCT outcomes. Disclosures Tabah: Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Huggar:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company; Karyopharm Therapeutics: Current equity holder in publicly-traded company; FibroGen: Current equity holder in publicly-traded company. Wang:Medicus Economics: Current Employment; Bristol Myers Squibb: Research Funding. Johnson:Medicus Economics: Current Employment; BMS: Research Funding. Copher:Bristol Myers Squibb: Current Employment. O'Connell:Bristol-Myers Squibb: Consultancy; Other biopharmaceutical manufacturers: Consultancy; Medicus Economics, LLC: Current Employment. Leblanc:AbbVie, Agios, Amgen, AstraZeneca, CareVive, BMS/Celgene, Daiichi-Sankyo, Flatiron, Helsinn, Heron, Otsuka, Medtronic, Pfizer, Seattle Genetics, Welvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; American Cancer Society, BMS, Duke University, NINR/NIH, Jazz Pharmaceuticals, Seattle Genetics: Research Funding; UpToDate: Patents & Royalties: Royalties; Agios, AbbVie, and Bristol Myers Squibb/Celgene: Speakers Bureau; AstraZeneca: Research Funding.

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Glucocorticoid maintenance therapy and severe infectious complications in ANCA-associated vasculitis: a retrospective analysis

Rheumatology International ◽

10.1007/s00296-020-04752-9 ◽

2020 ◽

Author(s):

Claudius Speer ◽

Christine Altenmüller-Walther ◽

Jan Splitthoff ◽

Christian Nusshag ◽

Florian Kälble ◽

...

Keyword(s):

Maintenance Therapy ◽

Kidney Function ◽

Patient Survival ◽

Disease Onset ◽

Infectious Complications ◽

Physical Damage ◽

Anca Associated Vasculitis ◽

Time To Relapse ◽

The Impact ◽

Patient Survival Time

AbstractTo study the impact of glucocorticoid maintenance dose and treatment duration on outcomes in patients with AAV (ANCA-associated vasculitis) with emphasis on infectious complications. A total of 130 AAV patients from two German vasculitis centers diagnosed between August 2004 and January 2019 treated with cyclophosphamide and glucocorticoids for induction therapy and glucocorticoids for maintenance therapy were retrospectively enrolled. We investigated the influence of glucocorticoid maintenance therapy on patient survival, time to relapse, kidney function, infectious complications and irreversible physical damage. The patients were divided into the following groups: patients treated according to the predefined reduction scheme (< 7.5 mg) or patients treated with glucocorticoids ≥ 7.5 mg after 6 months. Compared to patients receiving < 7.5 mg glucocorticoids after 6 months, patients receiving $$\ge $$ ≥ 7.5 mg had an increased rate of infectious episodes per patient (1.7 vs. 0.6; p < 0.001), including urinary tract infection (p = 0.007), pneumonia (p = 0.003), opportunistic pneumonia (p = 0.022) and sepsis (p = 0.008). Especially pneumonia during the first 24 months after disease onset [hazard ratio, 3.0 (95% CI 1.5 − 6.1)] led to more deaths from infection (p = 0.034). Glucocorticoid maintenance therapy after 6 months had no impact on relapse rate or patient survival and decline in kidney function was comparable. Glucocorticoid maintenance therapy with $$\ge $$ ≥ 7.5 mg after 6 months is associated with more severe infectious complications leading to an increased frequency of deaths from infection. Glucocorticoid maintenance therapy has no effect on time to relapse or patient survival and should therefore be critically revised throughout the aftercare of AAV patients.

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Molecular Analysis of Diamond Blackfan Anemia and Genotype-Phenotype Correlation: Experience from the Canadian Inherited Marrow Failure Registry

Blood ◽

10.1182/blood.v126.23.3621.3621 ◽

2015 ◽

Vol 126 (23) ◽

pp. 3621-3621

Author(s):

Omri Avraham Arbiv ◽

Bozana Zlateska ◽

Robert J. Klaassen ◽

Conrad Fernandez ◽

Rochelle Yanofsky ◽

...

Keyword(s):

Ribosomal Protein ◽

Research Funding ◽

Gene Panel ◽

Ribosomal Protein Genes ◽

Severe Phenotype ◽

Hematopoietic Stem ◽

Diamond Blackfan Anemia ◽

Genetic Groups ◽

Number Of Patients ◽

The Impact

Abstract Background/Objectives: Diamond Blackfan anemia (DBA) is an inherited disorder characterized by chronic hypoproductive anemia, physical malformations, and an increased risk of malignancies. At least 12 DBA genes have been identified, which include various ribosomal protein genes and the transcription factor GATA1. The aims of our study were (1) to identify the mutation spectrum of DBA patients, utilizing a cohort of patients enrolled on the Canadian Inherited Marrow Failure Registry (CIMFR) and (2) to determine whether specific hematological abnormalities, malformations, and outcomes are associated with specific mutations. Methods: Patients were enrolled on the CIMFR, which is a multicenter cohort study of inherited bone marrow failure syndromes (IBMFS). Genetic testing was performed using one or more of the following tests: Sanger sequencing, next generation sequencing (NGS) DBA gene panel, a comprehensive NGS IBMFS gene panel developed in our laboratory, or comparative genetic hybridization (CGH). Severity of the hematological disease was dichotomized according to a patient's requirement for chronic treatment: those who were maintained on corticosteroids, blood transfusions, or received a hematopoietic stem cell transplantation were considered to have a more severe phenotype than those who did not require hematological treatment. Chi-square tests with a Fisher's exact test correction were used to compare genetic groups with at least 5 patients on observed phenotypes. Results: 71 patients with DBA have been enrolled in our registry. A causal mutation has been identified in 36 of these patients, with the following rates: RPS19 (n=11), RPL11 (n=7), RPL5 (n=6), RPS26 (n=5), RPL35a (n=2), RPS24 (n=2), and one of each RPS7, RPS29, RPS17. Remarkably, a substantial number of patients in our population-based cohort (19.4%) had mild hematological phenotype requiring no therapy. Patients with RPL11 mutations tended to have a less severe DBA phenotype, while patients with RPS19 mutations tended to have a more severe phenotype (p=0.04). In terms of non-hematological malformations, we found no differences in cardiac, stature and craniofacial malformations across the groups compared (all p>0.1). However, patients with RPL5 mutations had significantly more hand malformations (p=0.02), and patients with RPS26 mutations had more genitourinary malformations (p=0.04). To control for the impact of mutation severity on the observed phenotype, we compared the prevalence of mutations that are predicted to result in truncated or lack of protein from the respective allele (large copy-number variation, nonsense, or indel frameshift) to mutations that are predicted to be hypomorphic or affect function (splicing, indel/inframe and, missense) between mutation categories. There were no differences among genetic groups in the severity of their mutations (p=0.58). Conclusions: Mutations in a wide spectrum of ribosomal protein genes underlie DBA cases in Canada, which approximate those observed by other registries in Western countries. Patients with DBA caused by RPL11 mutations tended to have a milder hematological phenotype, while patients with RPS19 mutation tended to have a more severe phenotype. Mutations in RPS26 and RPL5 are associated with genitourinary and hand malformations, respectively. Our findings may help improve counseling of DBA patients and their family. Future studies are needed to replicate our results and determine whether these findings can help personalize care. Disclosures Lipton: Ariad: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Teva: Consultancy, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Novartis Pharmaceuticals: Consultancy, Research Funding.

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Meta-Analytic Summary of the Burden of Pain and Fatigue in Multiple Myeloma

Blood ◽

10.1182/blood.v124.21.5967.5967 ◽

2014 ◽

Vol 124 (21) ◽

pp. 5967-5967

Author(s):

Peter C. Trask ◽

Mark Atkinson ◽

Bhumi Trivedi ◽

Andrew Palsgrove ◽

William Benton Jones ◽

...

Keyword(s):

Multiple Myeloma ◽

Sensitivity Analysis ◽

Research Funding ◽

Meta Analysis ◽

Clinical Group ◽

Common Symptom ◽

Newly Diagnosed ◽

Eortc Qlq C30 ◽

Eortc Qlq ◽

The Impact

Abstract Aims: Multiple myeloma (MM) is a hematologic malignancy of plasma cells. Bone disease is a characteristic symptom of MM, and pain is one of its most distressing features. Anemia is also a common symptom and is manifested as fatigue and tiredness among MM patients. We conducted a systematic review and meta-analysis of the EORTC QLQ-C30 pain and fatigue scales in two clinical MM populations (one with newly-diagnosed MM and a second undergoing medical management with re-emergent or advanced myeloma) to more precisely quantify the burden of pain and fatigue in MM. Methods: Studies assessing pain and fatigue in MM were identified through a search of specific terms in the medical-subject headings and keywords in PubMed. Inclusion criteria were English-language studies published between January 1, 1996, and July 1, 2014; diagnosis of MM; and availability of data on pain and/or fatigue as measured by the EORTC QLQ-C30. Full-text articles from germane abstracts were retrieved for eligibility assessment, and 27 articles were selected for inclusion in the analysis. Two groups of peer-reviewed articles were created: one consisting of publications that focused on newly-diagnosed MM and the other consisting of articles involving MM patients with advanced conditions, including those who had a disease recurrence or were receiving autologous bone marrow transplantation. The mean values and standard deviations (SDs) were recorded across all publications irrespective of sex, age, and stage of illness. Of the 27 studies, 17 did not report standard error (SE) or SD values associated with EORTC QLQ-C30 pain and fatigue scales. These missing values were estimated using the overall average of SDs for that scale observed across all studies within the publication group (either newly-diagnosed or recurrent/advanced disease). A sensitivity analysis was conducted to compare the pooled mean and SEs associated with results obtained with and without the SD imputation procedure. The means and SDs from the two sets of publications were entered into Comprehensive Meta-analysis™ with both scales (pain or fatigue) and existing or imputed SDs as grouping variables. The summary means and confidence intervals for each scale by clinical group were computed by weighting the individual studies by sample size and were statistically summarized based on a fixed-effect model. Results: The EORTC QLQ-C30 fatigue and pain scales range from 0-100 with higher scores indicating greater symptoms (i.e., more fatigue and pain). The overall mean across the 27 publications was 47.1 for fatigue and 48.2 for pain for MM patients compared to scores of 25.0 and 16.9 for a general population. The results of the sensitivity analysis indicated that estimation of the SDs for those studies missing the statistic did not have a significant effect on the summary mean estimate. In most cases, the inclusion of additional means with estimated SDs reduced the summary SE estimate associated with the summary mean. Overall, the scores for fatigue and pain across research articles involving newly-diagnosed patients (fatigue=48.5 and pain=49.1) were statistically higher (indicating worse pain and fatigue) than among patients who were recurrent or receiving more aggressive treatments (fatigue=39.9 and pain=38.7). Conclusions: The burden of pain and fatigue in MM is substantial and is different between newly-diagnosed and more advanced MM patients. Pain and fatigue can be easily quantified using standardized health-related quality of life instruments. Pivotal clinical trials in MM need to assess the impact of novel treatments on pain and fatigue. Disclosures Trask: Sanofi: Employment. Atkinson:Sanofi: Research Funding. Trivedi:Sanofi: Research Funding. Palsgrove:Sanofi: Research Funding. Jones:Sanofi: Employment. McHorney:Sanofi: Research Funding.

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Impact of Lenalidomide Maintenance Therapy on Immune Polarization and Activation in Multiple Myeloma

Blood ◽

10.1182/blood.v126.23.2966.2966 ◽

2015 ◽

Vol 126 (23) ◽

pp. 2966-2966 ◽

Cited By ~ 1

Author(s):

Manisha Bhutani ◽

David Foureau ◽

Tammy Cogdill ◽

Kyle Madden ◽

Qing Zhang ◽

...

Keyword(s):

Multiple Myeloma ◽

T Cells ◽

T Cell ◽

Maintenance Therapy ◽

T Cell Activation ◽

Research Funding ◽

Cell Activation ◽

Lymphoid Cells ◽

Relative Distribution ◽

The Impact

Abstract BACKGROUND: Lenalidomide is an immunomodulatory drug (IMiD) with co-stimulatory effects on immune effector cells in vitro and is an approved treatment for multiple myeloma (MM), although its mode of action in patients is not well defined. We studied the impact of lenalidomide maintenance therapy, following autologous stem cell transplant (ASCT), on NK and NK-T polarization (i.e. activating or inhibitory molecules) and, T cell activation (early vs. late activation) in patients with multiple myeloma. PATIENTS AND METHODS: In this ongoing prospective study with a targeted enrollment of 28 newly diagnosed multiple myeloma patients, blood samples are being collected at 2 to 3 months post ASCT, before starting lenalidomide maintenance therapy (baseline), and serially after 1, 3 and 6 months of treatment (T+1mo, T+3mo, T+6mo). Using a 9 color flow cytometry panel, peripheral blood samples were analyzed for expression of CD3 and CD56 to define NK (CD56+ CD3-), NKT (CD56+ CD3+), and T cell (CD56- CD3+) subsets. Killer 'inhibitory' Ig-like receptors, (KiR2DS4, KiR3DL1) natural killer group 2 proteins (NKG2a, NKG2D) and natural killer p46 protein (NKp46) expression were quantified to assess polarization of NK, and NK-T cells. Programmed death receptor 1 (PD-1) and T-cell Ig and mucin receptor 3 (Tim3) expression was quantified to assess T cell activation state. Flow cytometry data were acquired on a BD FACSAria II, and analyzed using FlowJo version X software. RESULTS: Samples from 11 patients have been collected and analyzed so far (11 baseline, 6 T+1mo, 4 T+3mo). At baseline lymphoid cells represent 12-46% of white blood cells (WBC), this heterogeneity being mainly driven by a wide range of T cell relative distribution among patients (30-74 % lymphoid cells). Phenotypically, NK cells at baseline mainly express natural cytotoxicity receptors (NKp46 and NKG2D), whereas NK-T cell also express NKG2D but approximately 1/3 also express PD-1 indicating they may be functionally defective. T cells at baseline express early T cell activation markers NKG2D and approximately 1/3 also stained positive for late T cell activation marker PD-1. Lymphoid cells relative distribution among WBC tends to normalize at T+1mo of treatment (15 to 35 % of WBC) before expanding at T+3mo (35 to 43 % of WBC). Phenotypically, across the 27 immune variables analyzed, each multiple myeloma patient displayed high level of immune homeostasis after 1 or 3 months of lenalidomide treatment. Noticeably, Nkp46 expression by NK cell and PD-1 expression by NK-T cells decreased in 4/6 patients and, NKG2D expression by T cell decreased in all but one patient during lenalidomide therapy. CONCLUSION: To our knowledge, this is the first study examining the influence of lenalidomide maintenance on the comprehensive immune repertoire in the post-ASCT setting in MM patients. The wide heterogeneity of NK, NK-T and T cell distribution observed at baseline among lymphoid cells indicates the potential effect of post-ASCT immune reconstitution and immunomodulatory the impact of lenalidomide. The capacity of lenalidomide to mediate effects on several immune cells raises the question as to which, if any, of these changes correlate with clinical responses. In our study, serially collected data from each patient, when completed would determine the impact of lenalidomide immunomodulatory effect of therapeutic efficacy and PFS duration in relation to immune reconstitution stage. Disclosures Cogdill: Millennium: Speakers Bureau; Onyx: Speakers Bureau; Celgene: Speakers Bureau; Novartis: Speakers Bureau. Ghosh:Celgene: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pharmacyclics: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Usmani:Sanofi: Honoraria, Research Funding; Millennium: Honoraria, Speakers Bureau; Onyx: Honoraria, Research Funding, Speakers Bureau; Pharmacyclics: Research Funding; Celgene: Honoraria, Speakers Bureau; Janssen Oncology: Honoraria, Research Funding; Array BioPharma: Honoraria, Research Funding.

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Results of Salvage Autologous Stem Cell Transplantation (ASCT) for Relapsed Multiple Myeloma (MM) in the Era of Novel Agents: Outcome of Patients (Pts) Receiving Prior Bortezomib (BTZ)-Based Therapy

Blood ◽

10.1182/blood.v128.22.5821.5821 ◽

2016 ◽

Vol 128 (22) ◽

pp. 5821-5821 ◽

Cited By ~ 2

Author(s):

Sara Farshchi Zarabi ◽

Esther Masih-Khan ◽

Christine Chen ◽

Vishal Kukreti ◽

Anca Prica ◽

...

Keyword(s):

Maintenance Therapy ◽

Induction Therapy ◽

Research Funding ◽

Chemotherapeutic Agents ◽

Novel Agents ◽

Remission Induction ◽

Group A ◽

Group B ◽

Relapsed Disease ◽

The Impact

Abstract Background: A second (salvage) ASCT has frequently been offered to MM patients with relapsed disease who experience benefit from the first procedure. We have previously reported that pts undergoing a salvage ASCT in the era of VAD or thalidomide (thal) have a median progression-free survival (PFS) of 19 months (mos). The best results were observed in pts who experienced ≥ 2 year benefit after their first ASCT (Jimenez-Zepeda VH et al. Biol Blood Marrow Transplant 2012; 18: 773-9). However, the utility of this approach after the introduction of novel chemotherapeutic agents--such as bortezomib (BTZ)--remains unclear. Initially, provincial funding for BTZ in Ontario was provided only for relapsed disease. However, in 2007, the combination of either BTZ + dexamethasone (BTZ-dex) or cyclophosphamide, BTZ + dex (CyBorD) was adopted as the standard induction regimen for newly diagnosed pts before ASCT performed as part of first-line therapy. We now examine the results of salvage ASCT in our centre after the availability of BTZ. Methods: We used the Princess Margaret Myeloma Database to identify and characterize patients with relapsed MM who had received a bortezomib (BTZ)-based regimen for remission induction prior to their first ASCT or for re-induction before salvage ASCT. A retrospective chart review was performed to investigate the PFS and overall survival (OS) outcomes of these pts. Results: Between 01/2005 and 07/2015, 64 pts with MM who had previously received BTZ-based therapies underwent salvage ASCT for relapsed disease at our centre (Table 1). Median age was 56.9 yrs (range 37-67.3); 37 (58%) were male. ISS stage was 1 in 32 (50%), 2 in 16 (25%), 3 in 14 (22%) and NA in 2 (3%). The median interval between first and salvage ASCT for all pts was 48.6 mos (range 26.9-130.3), reflecting our policy of preferentially offering salvage ASCT to pts with at least a 2-yr benefit from the first transplant; the median time between re- induction therapy and salvage ASCT was 6.3 mos (range 0.3-95.9). Group A pts (n=27) had received BTZ-based therapy before their first ASCT; 48% of these also received BTZ-based regimens again prior to salvage ASCT. Pts in Group B (n=37) received BTZ-based regimens before the salvage transplant only, while induction therapy before the first ASCT consisted of VAD (21), dex alone (8), thal + dex or other regimens (5). Twenty-two (34%) of the pts received maintenance therapy between the first and salvage ASCT (most often thal-based), while 35 (55%) of the pts received maintenance therapy following salvage ASCT (most frequently lenalidomide [len]-based). The survival outcomes are summarized in Table 2. Median duration of follow-up (F/U) following salvage ASCT was 19.1 mos (range 0.8-96.4). One patient (1.6%) died several days following salvage ASCT. No other transplant-related mortality occurred. The median PFS following salvage ASCT was 19.1 mos (range 0.8- 87.5) with a median OS of 26.5 mos (range 0.8-101.9) in all pts. The median PFS after salvage ASCT was 15.8 mos for Group A and 25.2 mos for Group B pts. Conclusions: Even in the era of novel agents, salvage ASCT may provide PFS benefit to pts with relapsed MM who were previously treated with a BTZ-based regimen. However, the details of the optimal approach in this setting are not certain, including the impact of maintenance therapy given after the first and/or salvage ASCT. We are performing additional analyses of this population to try to identify factors associated with the best outcomes. Disclosures Kukreti: Celgene: Honoraria; Lundbeck: Honoraria; Amgen: Honoraria. Prica:Janssen: Honoraria. Tiedemann:Novartis: Honoraria; Celgene: Honoraria; Takeda Oncology: Honoraria; BMS Canada: Honoraria; Amgen: Honoraria; Janssen: Honoraria. Trudel:Celgene: Honoraria; Novartis: Honoraria; Glaxo Smith Kline: Honoraria, Research Funding; Oncoethix: Research Funding. Reece:Merck: Research Funding; Takeda: Consultancy, Honoraria, Research Funding; BMS: Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Otsuka: Honoraria, Research Funding; Novartis: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding.

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The Impact of Age in Allogeneic Stem Cell Transplantation with Thiotepa Busulfan and Fludarabine (TBF) for Myelofibrosis : A Retrospective Analysis

Blood ◽

10.1182/blood-2021-145711 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 4858-4858

Author(s):

Federica SORA ◽

Patrizia Chiusolo ◽

Sabrina Giammarco ◽

Idanna Innocenti ◽

Francesco Autore ◽

...

Keyword(s):

Stem Cell ◽

Stem Cell Transplantation ◽

Total Dose ◽

Cell Transplantation ◽

Older Patients ◽

Research Funding ◽

Acute Gvhd ◽

Conditioning Regimen ◽

Hematopoietic Stem ◽

The Impact

Abstract Allogeneic hematopoietic stem-cell transplantation (HSCT) currently remains the only curative therapy for intermediate or high risk disease.myelofibrosis (MF). We are reporting 56 patients (pts) who underwent an allogeneic HSCT in our Centre between 2016 and 2020, and assessed factors predictive of outcome. The median age was 59 years (36-72). Most patients (72%) were JAK2+ and had int2-high DIPSS (92%). The conditioning regimen consisted of thiotepa, busulfan , fludarabine (TBF). All pts received thiotepa 10 mg/kg and fludarabine 150 mg/m^2. The dose of busulfan was adjusted considering the age and the comorbidity score. One pt received 3 days of busulfan (total dose 9.6 mg/kg); 47 received 2 days (total dose 6.4 mg/kg) and 8 received one day of busulfan iv (3.2 mg/kg). Donor was an identical sibling in 13 pt, haploidentical in 18, matched unrelated donor (UD) in 18 and a mismatchedUD in 7. Thus we had 31 HLA matched and 25 HLA mismatched grafts. Fortytwo patients received post-transplant cyclophosphamide (PTCy)-based GVHD (Graft versus host disease ) prophylaxis with cyclosporine and mycophenolate mofetil , and 14 patients received a standard GvHD prophylaxis (CSA+MTX+ATG). The 2 year survival (OS) was 73 % and disease free survival (DFS) was 66 % and the cumulative incidence (CI) of TRM was 23% and of relapse 11%. The incidence of acute GvHD grade II-IV was 22% in HLA matched and 50% in HLA mismatched pts (p=0.022), grade III-IV was 6% and 25% respectively (p=0.042) . The incidence of moderate-severe chronic GvHD was 25% in HLA matched and 36% in HLA mismatched grafts (p=0.36). HLA had a major impact on survival : 85% vs 49% survival for matched vs mismatched patients (p=0.01). Patients age >60 years had a major impact on outcome, with a 2 year survival of 51% vs 88% in patients over (n=24) or under 60 years of age (n=32) (p=0.007; the DFS was 46 % and 80% respectively and the CI of TRM was 42% vs 9% (p=0.003). As to the total dose of busulfan, we found 26% TRM in patients receiving busulfan for 2 days (total doe 6.4 mg/kg) (n=47) and 0% in older patients receiving 1 day only (total dose 3.2 mg/kg) (n=8) ; relapse rate was 10% and 20% respectively. In multivariate cox analysis including age, spleen size ,DIPSS score, number of transfusion received and donor type, only HLA matching influenced the incidence of acute GvHD; transfusion burden and age plays a role in NRM and OS; DIPSS predicts relapse . In conclusion: older patients with MF have a high NRM and need to be prepared with a milder conditioning regimen. Disclosures Laurenti: Janssen: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; AbbVie: Consultancy, Honoraria, Research Funding; Roche: Honoraria, Research Funding; Gilead: Honoraria; BeiGene: Honoraria. Sica: Pfizer: Honoraria.

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A Phase I Trial of the Antibody-Cytokine Fusion Protein F16IL2 in Combination with Anti-CD33 Immunotherapy for Posttransplant AML Relapse

Blood ◽

10.1182/blood-2021-145859 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2345-2345

Author(s):

Andrew F. Berdel ◽

Christoph Rollig ◽

Martin Wermke ◽

Linus Angenendt ◽

Leo Ruhnke ◽

...

Keyword(s):

Fusion Protein ◽

Nk Cells ◽

Board Of Directors ◽

Dose Escalation ◽

Research Funding ◽

Human Antibody ◽

Publicly Traded ◽

Advisory Committees ◽

Hematopoietic Stem ◽

Dose Levels

Abstract Introduction Natural killer (NK) cells are key effectors in cancer immunosurveillance and posttransplant immunity, but shortage of environmental growth factors and deficient recognition of malignant cells may limit their anticancer efficacy. We hypothesized that the antibody-mediated anchoring of interleukin-2 (IL-2) to the leukemia-modified extracellular matrix (ECM) would increase NK cell abundance and activity to potentiate antibody-dependent cellular cytotoxicity (ADCC) against acute myeloid leukemia (AML) blasts. In this novel-novel combination dose-escalation phase 1 trial, we enrolled patients with AML relapse after allogeneic hematopoietic stem cell transplantation (HSCT) to evaluate the safety, pharmacokinetics, pharmacodynamics, and preliminary activity of F16IL2, an antibody-cytokine fusion protein composed of the human antibody fragment scFv(F16) in diabody format and two molecules of human IL-2, in combination with the Fc-optimized, ADCC-mediating anti-CD33 monoclonal antibody BI 836858. F16 specifically targets the A1 domain of the ECM protein tenascin C (TnC), which is spliced into the TnC molecule during active angiogenesis and tissue remodeling while it is virtually absent in normal tissues. Methods F16IL2 (10 - 20 Mio IU IV) was administered on days 1, 8, 15 and 22 of 28-day cycles, followed by administration of BI 836858 (10 - 40 mg IV) two days after each F16IL2 infusion. Dose escalation was performed over 4 dose levels (DL). Cohort 1 (10 Mio IU F16IL2 and 10 mg BI 836858, n = 5), cohort 2 (10 Mio IU F16IL2 and 20 mg BI 836858, n = 3), cohort 3 (20 Mio IU F16IL2 and 20 mg BI 836858, n = 4), cohort 4 (20 Mio IU F16IL2 and 40 mg BI 836858, n = 3). Safety and tolerability, pharmacodynamics and -kinetics, clinical efficacy and immune effector cell dynamics were investigated. This trial was registered at EudraCT as #2015-004763-37. Results Between December 2016 and March 2020, 15 patients with a median age of 50 years (range, 20 - 68) were enrolled and treated across 4 dose levels. Six patients (40%) had received two or more prior HSCT. The most frequent drug-related AEs (F16IL2 or BI 836858 or combination) were pyrexia (n = 13, 87%), chills (n = 12, 80%) and infusion-related reactions (n = 9, 60%), consistent with the expected toxicity profile of cytokine-armed or naked mAbs. These events were generally manageable, transient and of grade ≤ 2. One dose-limiting toxicity occurred at each of DL 3 (pulmonary edema) and 4 (acute GVHD). No patient died within the first 30 days of treatment initiation. Whereas no formal maximum tolerated dose (MTD) was reached, the maximum tested dose of 20 Mio IU F16IL2 and 40 mg BI 836858 was considered the recommended dose (RD). Three objective responses (1 CR, 1 CRi, 1 PR in extramedullary AML) were observed among 7 patients treated at the two higher DL, whereas no responses occurred at the two starting DL. Median OS among all 15 patients was 4.8 months (1.5 - 12.9), with a 6- and 12-month OS of 40% and 27%, respectively. Among those 7 patients whose AML was at least temporarily controlled with study treatment (CR/CRi, PR, SD), 12-month OS was 67% vs. 0% in non-responders. Combination therapy stimulated the expansion and activation of NK cells in bone marrow and peripheral blood. Conclusions To the best of our knowledge, this is the first study demonstrating that the strategy of potentiating ADCC with tumor-targeted immunocytokines is feasible in humans. In the difficult-to-treat situation of posttransplant AML relapse, responses were observed at higher DL, even in patients with extramedullary disease. The antibody-mediated targeted delivery of IL-2 to the ECM combined with anti-CD33 immunotherapy represents an innovative experimental approach associated with acceptable safety and encouraging biologic and clinical activity in posttransplant AML relapse. Disclosures Wermke: Novartis, Roche, Pfizer, BMS: Consultancy, Honoraria, Research Funding. Hemmerle: Philogen S.p.A.: Current Employment. Schäfers: Philogen S.p.A.: Research Funding. Rossig: BMS and Celgene: Honoraria; Pfizer: Honoraria; Novartis: Honoraria; AdBoards by Amgen: Honoraria. Stelljes: Pfizer: Consultancy, Research Funding, Speakers Bureau; Kite/Gilead: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; MSD: Consultancy, Speakers Bureau; Celgene/BMS: Consultancy, Speakers Bureau; Medac: Speakers Bureau; Amgen: Consultancy, Speakers Bureau. Rueter: Boehringer Ingelheim Pharma GmbH & Co. KG: Current Employment. Neri: Philogen S.p.A.: Current Employment, Current equity holder in publicly-traded company, Divested equity in a private or publicly-traded company in the past 24 months, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties: Multiple patents on vascular targeting; ETH Zurich: Patents & Royalties: CD117xCD3 TEA. Berdel: Philogen S.p.A.: Consultancy, Current equity holder in publicly-traded company, Honoraria, Membership on an entity's Board of Directors or advisory committees. Schliemann: Roche: Consultancy; Philogen S.p.A.: Consultancy, Honoraria, Research Funding; Astellas: Consultancy; Pfizer: Consultancy; BMS: Consultancy, Other: travel grants; Boehringer-Ingelheim: Research Funding; Novartis: Consultancy; Jazz Pharmaceuticals: Consultancy, Research Funding; AstraZeneca: Consultancy; Abbvie: Consultancy, Other: travel grants.

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Donor Genetic Determinant of Thymopoiesis rs2204985 Impacts Clinical Outcome after Single HLA Mismatched HSCT

Blood ◽

10.1182/blood-2021-144748 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3903-3903

Author(s):

Chrysanthi Tsamadou ◽

Sowmya Gowdavally ◽

Uwe Platzbecker ◽

Elisa Sala ◽

Thomas Valerius ◽

...

Keyword(s):

T Cell ◽

Research Funding ◽

Genetic Variant ◽

Chronic Gvhd ◽

Disease Free Survival ◽

Multivariate Models ◽

Common Genetic Variant ◽

Hematopoietic Stem ◽

Genotype Frequencies ◽

The Impact

Abstract Introduction: A common genetic variant within the TCRA-TCRD locus has been recently identified as a predictive factor of thymic function and T cell repertoire diversity (Clave et al., 2018). Specifically it was shown in a mouse model that transplantation of rs2204985 AA human hematopoietic stem cells (HSC) into immunodeficient mice led to lower thymocyte counts and poorer TCR diversity. T cell mediated pathways are known to play a significant role in immunological processes affecting HSCT outcome like GvL, GvH and infection. Aim of this study was to investigate the potential impact of donor rs2204985 genotype on patient's outcome after unrelated HSCT. Methods: The study included 2,016 adult patients with hematologic malignancies who received their first unrelated (10/10 or 9/10 HLA matched) graft between 2000 and 2013 in a German transplant center. Patients with refractory disease at time of transplantation were excluded from the analysis. Both donors and patients were retrospectively genotyped for the TCRA-TCRD rs2204985 polymorphism by next generation sequencing using a validated protocol on an Illumina Miseq platform. Overall survival (OS), disease free survival (DFS), relapse (RI), non-relapse mortality (NRM), acute GvHD (aGvHD) and chronic GvHD (cGvHD) were evaluated; p<0.05 was considered significant and donor rs2204985 GG/AG genotype was set as reference vs the AA genotype. Stratification for diagnosis was performed and a backward stepwise model finding approach was used to select variables related to a given outcome with a threshold of 0.10 for retention in the model. Results: The rs2204985 genotype frequencies found in both patients and donors were in line with those previously reported for Caucasian populations indicating a codominance of the two alleles (i.e. A and G). Regarding the impact of this genetic variation on outcome, multivariate analysis of the combined cohort indicated different risk estimates in 10/10 and 9/10 HLA matched transplantations, therefore subanalysis on account of HLA incompatibility was performed. Analysis in the subgroup of single HLA mismatched cases (n=624) revealed that donor AA genotype associated with markedly inferior OS (55.1% vs 70.6%, p=0.004, Fig. 1) and DFS (47.6% vs 63.4%, p=0.002, Fig. 2) one year after HSCT as compared to the donor AG/GG genotypes. These results were confirmed in the corresponding multivariate models (OS HR: 1.48, p=0.003; DFS HR: 1.50, p=0.001) which are visually displayed as forest plots in Fig. 3 and Fig 4, respectively. The adverse effect of donor AA genotype on survival appears to be driven by a combined higher risk of RI (1Y after HSCT: 29.3% vs 18.3%, p=0.048; HR: 1.38, p=0.035) and NRM (1Y after HSCT: 28.6% vs 19.9%, p=0.043; HR: 1.38, p=0.042) as shown by both the univariate and multivariate analyses for the two respective endpoints. No association was found between donor rs2204985 genotype and risk of acute or chronic GvHD. The donor rs2204985 genotype had also no significant impact on any outcome endpoint in the 10/10 HLA matched subgroup. Last, no significant interactions were observed between this variable and the other adjusted covariates in the multivariate models. Conclusion: To our knowledge this is the first study to date investigating the potential effect of donor's genotype regarding a common genetic variant within the TCRA-TCRD locus on the outcome of patients receiving unrelated HSC grafts. Our data suggest that donor rs2204985 AA genotype in combination with single HLA mismatches may adversely affect the outcome of HSC transplanted patients and should therefore be avoided. It is of note that one in four unrelated donors of Caucasian origin is expected to carry the AA genotype. A weaker relapse and -presumably- infection control, especially in the early post-transplantation period, due to compromised T cell reconstitution as a result of the unfavorable donor AA genotype may account for these findings. Confirmatory studies in larger independent cohorts are warranted before final conclusions are drawn. Figure 1 Figure 1. Disclosures Platzbecker: Geron: Honoraria; Janssen: Honoraria; Takeda: Honoraria; AbbVie: Honoraria; Novartis: Honoraria; Celgene/BMS: Honoraria. Sala: Celgene/BMS: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Gilead: Consultancy, Honoraria; Jazz: Consultancy, Honoraria. Wulf: Gilead: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Clinigen: Consultancy, Honoraria. Kroeger: Celgene: Honoraria, Research Funding; Riemser: Honoraria, Research Funding; Gilead/Kite: Honoraria; AOP Pharma: Honoraria; Novartis: Honoraria; Jazz: Honoraria, Research Funding; Sanofi: Honoraria; Neovii: Honoraria, Research Funding. Einsele: Janssen, Celgene/BMS, Amgen, GSK, Sanofi: Consultancy, Honoraria, Research Funding. Hertenstein: Novartis: Honoraria; Sanofi: Honoraria; Celgene: Honoraria; BMS: Honoraria. Schrezenmeier: Alexion, AstraZeneca Rare Disease: Honoraria, Other: Travel support, Research Funding; Roche: Honoraria; Novartis: Honoraria; Apellis: Honoraria; Sanofi: Honoraria.

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Targeting the Inflammatory Niche in MDS By Tasquinimod Restores Hematopoietic Support and Suppresses Immune-Checkpoint Expression in Vitro

Blood ◽

10.1182/blood-2021-150455 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 2596-2596

Author(s):

Manja Wobus ◽

Ekaterina Balaian ◽

Uta Oelschlaegel ◽

Russell Towers ◽

Kristin Möbus ◽

...

Keyword(s):

Bone Marrow ◽

Mrna Expression ◽

Immunohistochemical Staining ◽

Research Funding ◽

Fold Increase ◽

Low Risk ◽

Hematopoietic Stem ◽

Healthy Donors ◽

The Impact

Abstract Introduction Myelodysplastic syndromes (MDS) belong to the most common hematological neoplasms in the elderly population, characterized by ineffective hematopoiesis, peripheral cytopenia and the risk of transformation into acute myeloid leukemia. There is increasing evidence that an aberrant innate immune response and a proinflammatory bone marrow (BM) microenvironment play a critical role in the pathogenesis of MDS. The alarmin S100A9, a key player for regulation of inflammatory responses, has been shown to be elevated in MDS patients. It directs an inflammatory cell death (pyroptosis) by increased NF-kB mediated transcription and secretion of proinflammatory, hematopoiesis-inhibitory cytokines and production of reactive oxygen species. Tasquinimod (TASQ, Active Biotech) is a novel, oral small molecular drug with S100A9 inhibitory activity and it is currently investigated in a phase Ib/IIa trial in relapsed/refractory multiple myeloma (NCT04405167). TASQ has demonstrated anti-angiogenic, antitumor and immunomodulatory properties in a broad range of preclinical solid tumor models; however, little is known about its effects in myeloid malignancies. Aim We investigated the role of S100A9 in cellular models of MDS and the potential of TASQ to target S100A9 within the MDS stroma in vitro. Methods Immunohistochemical staining of S100A9, CD271+ mesenchymal stromal cells (MSCs), CD68+ macrophages and CD66b+ neutrophils in BM tissues from MDS patients and healthy donors was performed with multiplex immunohistochemistry and analyzed with the VECTRA imaging system. MSCs from patients with either low-risk MDS, CMML or age-adjusted healthy donors were exposed to S100A9 (1.5µg/ml) in the presence or absence of TASQ (10µM). Subsequently, TLR4 downstreaming molecules such as IRAK1, gasdermin and NF-kB-p65 were analyzed by Western blot. Moreover, the mRNA expression of further proinflammatory molecules (IL-1b, IL-18, caspase1) and PD-L1 was quantified by real-time PCR. To study the impact on the hematopoietic support, MSCs were pre-treated for one week with S100A9 ± TASQ before CD34+ hematopoietic stem and progenitor cells (HSPCs) were seeded on the stromal layer. The colony formation (CAF-C) was analyzed weekly followed by a CFU-GEMM assay in methylcellulose medium. Additionally, PD-1 mRNA expression was quantified in cocultured HSPCs. Results Immunohistochemical staining of BM tissue demonstrated S100A9 expression mainly by CD66b+ neutrophils and with less extent by CD68+ macrophages. In line with this, we could not detect relevant S100A9 mRNA expression in cultured MDS or healthy MSCs in vitro. Exposure of MDS and healthy MSCs with S100A9 induced TLR4 downstream signalling as demonstrated by increased expression of IRAK1 and NF-kB-p65. We further detected a higher expression of gasdermin, an inductor of pyroptosis, in S100A9 exposed MSCs. Addition of TASQ abolished these effects and inhibited the expression of the mentioned proteins, indicating an alleviation of inflammation. Furthermore, we detected a 2-fold increase of mRNA expression of the proinflammatory cytokines IL-1b and IL-18 as well as a 5-fold increase of their activator caspase 1 in MSCs after treatment with S100A9, which could be prevented by TASQ. Interestingly, PD-L1 as a potential downstream target was induced by S100A9 by 2.5-fold and could be suppressed by TASQ to about 50%. To evaluate the impact on the hematopoietic support of MSCs, we analysed MSC/HSPC cocultures after treatment with S100A9. We observed a decreased number of cobblestone area forming cells (CAF-C) as well as reduced numbers of colonies (CFU) in a subsequent clonogenic assay, indicating a disturbed hematopoietic support by S100A9 treated MSCs. Interestingly, both the number of CAF-C and CFU could be increased by TASQ pre-treatment. Finally, the PD-1 expression in co-cultured HSPCs was regulated in the same way as its ligand in treated MSCs, nominating this interaction as a potential target of S100A9/TASQ in the MDS BM. Conclusion In summary, we provide evidence that the pathological inflammasome activation in the myelodysplastic bone marrow can be rescued by TASQ at least in part by inhibition of the S100A9 mediated TLR4 downstream signalling including NF-kB-p65 transcription and PD-L1 expression. These effects result in an improved hematopoietic support by MSCs, suggesting a potential efficacy to improve cytopenia in low-risk MDS patients. Disclosures Balaian: Novartis: Honoraria. Törngren: Active Biotech: Current Employment. Eriksson: Active Biotech: Current Employment. Platzbecker: AbbVie: Honoraria; Takeda: Honoraria; Celgene/BMS: Honoraria; Novartis: Honoraria; Janssen: Honoraria; Geron: Honoraria. Röllig: Novartis: Honoraria, Research Funding; Jazz: Honoraria; Janssen: Honoraria; Bristol-Meyer-Squibb: Honoraria, Research Funding; Amgen: Honoraria; AbbVie: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding; Roche: Honoraria, Research Funding.

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A Transgenic Murine Model Expressing Hyperactive STAT3 Recapitulates the Features of MDS/AML

Blood ◽

10.1182/blood-2021-151691 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 3308-3308

Author(s):

Bianca L Rivera ◽

Shanisha Gordon ◽

Srinivas Aluri ◽

Yang Shi ◽

Samarpana Chakraborty ◽

...

Keyword(s):

Stem Cells ◽

Transgenic Mice ◽

Rna Sequencing ◽

Murine Model ◽

Research Funding ◽

Publicly Traded ◽

Gfp Expression ◽

Hematopoietic Stem ◽

Myeloid Malignancies ◽

Stop Cassette

Abstract Myelodysplastic syndromes (MDS) are clonal, myeloid malignancies that emerge and progress due to the expansion of disease-initiating aberrant hematopoietic stem cells that can evolve into Acute Myeloid Leukemia (AML). FDA approved therapies such as the recently approved Bcl-2 inhibitor venetoclax, FLT3 inhibitors, among others, have moved the field forward in newly diagnosed MDS/AML. However, relapsed/refractory (R/R) disease, as well as leukemic transformation post-MDS continues to have a poor prognosis. A pool of hematopoietic stem and progenitor cells (HSPCs) escape chemotherapy, proliferate during disease remission, and causes relapse partly in effect due to signaling effector mutations. It is imperative, for future therapeutic agents, to target these HSPCs populations to achieve a durable remission for aggressive myeloid malignancies. There is an urgent need to develop mouse models that recapitulate human disease for the study of pathogenesis and drug development in these disorders. Signal transducer and activator of transcription 3 (STAT3) belongs to the STAT family of transcription factors that are inappropriately activated in several malignancies. Our preliminary data indicates that STAT3 is overexpressed in MDS and AML stem cells and is associated with an adverse prognosis in a large cohort of patients. (Shastri et al, JCI 2018). We have successfully demonstrated that a selective antisense oligonucleotide inhibitor of STAT3, Danvatirsen, is rapidly incorporated into MDS/AML HSPCs and induces selective apoptosis and downregulation of STAT3 in these cells in comparison with healthy control HSPCs. To determine the role of STAT3 in the initiation of myeloid malignancies, a murine model was generated by crossing R26STAT3C stopfl/fl mice with vavCre transgenic mice. In this model, a hyperactive version of STAT3, STAT3C, is knocked into the Rosa26 locus with an upstream floxed stop cassette (R26STAT3C stopfl). Excision of the stop cassette by Cre recombinase leads to expression of a flag-tagged STAT3C protein and concomitant expression of EGFP in hematopoietic cells. GFP expression allows tracking of cells in which the floxed stop/Neo cassette is deleted and STAT3C is expressed. STAT3C-vavCre double transgenic mice were validated by GFP expression in HSPCs and differentiated hematopoietic cells. The STAT3C-vavCre mice developed ruffled fur, a hunched phenotype and weight-loss by five months of age. CBC analysis of STAT3C-vavCre mice shows a proliferative phenotype reminiscent of high-risk MDS/AML with higher WBC & platelet counts and lower hemoglobin (Figure 1A). Review of the peripheral smear showed an increase in granulocytic precursors that are likely leukemic blasts (Fig 1E). In addition, STAT3C-vavCre mice developed massive splenomegaly (Figure 1B). HSC lineage analysis by FACS showed the presence of GFP positive cells (Figure 1C) with increased expansion of the MPP and HSC compartment compared to controls, suggesting a stem and progenitor phenotype (Figure 1D). Murine myeloid colony assays showed larger colonies in the STAT3C-vavCre mice compared to controls. At this time, single cell RNA sequencing, and bulk RNA sequencing are being performed and will be used to further characterize the phenotype of the STAT3C-vavCre transgenic mice in addition to bone marrow and splenic aspirates & biopsies. Through the generation of a STAT3C-vavCre mouse model, that recapitulates the features of MDS/AML, we aim to further our understanding of the molecular mechanisms and pathways that play an important role in MDS to AML transformation and will help us identify downstream mediators of this event that can be therapeutically targeted. We would also like to use this murine model as an ideal substrate for preclinical studies of STAT3 targeting therapies in hematologic malignancies such as previously reported antisense inhibitors of STAT3 and STAT3 degraders. Figure 1 Figure 1. Disclosures Frank: Roche Genentech: Research Funding; Kymera: Consultancy, Research Funding; Revitope: Consultancy; Vigeo: Consultancy. Verma: Throws Exception: Current equity holder in publicly-traded company; BMS: Research Funding; GSK: Research Funding; Acceleron: Consultancy; Incyte: Research Funding; Stelexis: Current equity holder in publicly-traded company; Medpacto: Research Funding; Curis: Research Funding; Eli Lilly: Research Funding; Celgene: Consultancy; Stelexis: Consultancy, Current equity holder in publicly-traded company; Novartis: Consultancy. Shastri: Kymera Therapeutics: Research Funding; GLC: Consultancy; Guidepoint: Consultancy; Onclive: Honoraria.

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