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Summary There is limited understanding of the impact of frailty on clinical outcomes in patients with myelofibrosis (MF). In this retrospective cohort study on 439 chronic phase MF patients [mean age: 68·7 ± 12 years; median follow‐up: 3·4 years (IQR 0·4–8·6)] from 2004 till 2018, we used a 35‐variable frailty index (FI) to categorise patient’s frailty status as fit (FI

Core-binding factor acute myeloid leukemia is characterized by t(8;21) or inv(16) and the fusion proteins RUNX1-RUNX1T1 and CBFB-MYH11. International guidelines recommend monitoring for measurable residual disease every 3 months for 2 years after treatment. However, it is not known whether serial molecular monitoring can predict and prevent morphological relapse. We conducted a retrospective singlecenter study of 114 patients in complete remission who underwent molecular monitoring with real-time quantitative polymerase chain reaction analysis of RUNX1-RUNX1T1 or CBFB-MYH11 transcripts every 3 months. Morphological relapse was defined as re-emergence of >5% blasts and molecular relapse as ≥1 log increase in transcript level between two samples. Over a median follow-up time of 3.7 years (range, 0.2-14.3), remission persisted in 71 (62.3%) patients but 43 (37.7%) developed molecular or morphological relapse. Patients who achieved

Despite the curative potential of allogeneic hematopoietic cell transplantation (HCT) for myelofibrosis (MF), a significant number of patients with MF do not undergo HCT. Factors influencing treatment preferences in these patients have not been well studied. This study was conducted to identify patient-, disease-, and donor-related factors influencing the decision regarding HCT in patients with MF. A secondary objective was to compare survival between patients who elected upfront HCT and those who opted for nontransplantation therapy. We conducted a retrospective chart review amongst patients meeting criteria for transplant indication, evaluating clinical characteristics, treatment preferences, and outcomes. Of the 183 study eligible patients age70 years, 129 (70%) developed an HCT indication. Age60 years was significantly associated with higher rates of HLA-typing refusal (13 of 72 versus 1 of 44; P = .02). Caucasian ethnicity was significantly associated with an increased rate of identifying well-matched donors compared with non-Caucasian ethnicity (75% versus 48%; P = .02). Of the 69 patients with well-matched donors, 34 (49%) preferred to not pursue upfront HCT despite an indication for transplantation. Patient preference for nontransplantation therapies was the most common reason for declining HCT. We did not find any difference in survival between patients pursuing upfront HCT and those opting for nontransplantation therapies, although more patients in the HCT arm were in remission at the last follow-up. Patients of Caucasian ethnicity were significantly more likely than non-Caucasian patients to identify a well-matched donor. Despite availability of a well-matched donor, a significant proportion of MF patients with an indication for transplantation do not pursue HCT. Patient age, donor type, and patient preference play major roles in the selection of upfront HCT. Although a survival difference was not observed between upfront HCT versus non-transplant therapy, more patients in the HCT arm were in remission at the last follow-up.

Introduction: Acute myeloid leukemia (AML) is driven by a subpopulation of leukemia stem cells (LSCs), which possess properties such as quiescence and self-renewal that are linked to therapy resistance and relapse. The LSC17 score was derived from genes differentially expressed between functionally validated LSC+ and LSC- fractions from 78 AML patients and is strongly associated with survival and response to standard therapy. A critical advantage of the LSC17 test over cytogenetic and molecular analysis is its rapid turnaround time (24-48h on a NanoString platform), providing clinicians with a rapid and powerful tool for upfront risk stratification. We have developed a clinical assay for the LSC17 score validated in a CAP/CLIA-lab setting. Methods: We conducted a prospective, multicenter validation and feasibility study to test the prognostic value of the LSC17 assay under real-world conditions in AML patients treated with curative intent. Patients with a possible new diagnosis of AML were eligible. Patients with a confirmed diagnosis of acute promyelocytic leukemia were excluded from analysis. Standard prognostic markers including cytogenetics, molecular studies and targeted sequencing using a standard AML panel were performed in parallel to the LSC17 score. Treatment was administered according to physician preference, based on patient history and results of standard prognostic assays, when available. Survival data was censored on June 14th, 2020. Results: 381 patients were recruited to the study between June 2016 and March 2020. 4 patients were excluded for quality control reasons (one sample had insufficient RNA and three samples failed quality control checks). 103 were excluded as they had alternative diagnoses. 84 patients were excluded because they did not receive intensive chemotherapy. LSC17 scores ranged from 0 to 1.25, and were classified as high or low according to the median score of 0.51 from a previously validated reference cohort (Ng et al, Nature 2016). Of the 190 patients included in this analysis, 84 had a low LSC17 score and 106 had a high LSC17 score. The median age was 61 years (range 18-79); 86 (45%) were female. When stratified according to ELN 2017 criteria, 48 (27%), 51 (29%), and 77 (44%) patients had favorable, intermediate, and adverse risk disease, respectively. Low LSC17 score was associated with normal cytogenetics (high vs low, 33% vs 58%; P We first considered response to induction chemotherapy (Table 1). 141 patients had standard induction chemotherapy with 3+7, 40 had Flag-IDA and 9 had CPX-351. High score patients had inferior responses to 3+7 with only 59% achieving complete remission (CR) after 1 cycle of chemotherapy compared to 96% of low score patients; responses for LSC17 high score patients were better in the Flag-IDA group with 80% achieving CR after 1 cycle. When considering overall CR rates after 2 cycles of induction, patients with a high LSC17 score were less likely to achieve CR (high vs low, 87% vs 98%; P=0.02). However, this difference was predominantly observed in patients treated with 3+7 (87% vs 99% CR rate in high vs low score patients, respectively); response rates to Flag-IDA were not significantly different between the 2 groups. Measurable residual disease (MRD) monitoring by flow cytometry was performed at the time of CR in 135 (71%) patients enrolled at Princess Margaret Cancer Centre. Patients with a high LSC17 score were significantly more likely to have MRD compared to low score patients (46% vs 10% respectively, P Conclusion: AML patients with a high LSC17 score have inferior outcomes following 3+7 induction chemotherapy. The LSC17 score should be considered as a tool to identify and stratify high-risk patients to alternative upfront therapies such as Flag-IDA. A risk adapted study is planned to validate these results. Disclosures Gupta: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Bristol MyersSquibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Research Funding. Maze:Novartis: Honoraria; Takeda: Research Funding; Pfizer: Consultancy. McNamara:Novartis: Honoraria. Schimmer:Medivir AB: Research Funding; AbbVie Pharmaceuticals: Other: owns stock ; Takeda: Honoraria, Research Funding; Novartis: Honoraria; Jazz: Honoraria; Otsuka: Honoraria. Leber:Takeda/Palladin: Honoraria, Membership on an entity's Board of Directors or advisory committees; Treadwell: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS/Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Abbvie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Otsuka Pharmaceutical: Honoraria, Membership on an entity's Board of Directors or advisory committees; Lundbeck: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Tierens:Amgen: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas Pharma: Membership on an entity's Board of Directors or advisory committees. Wang:Trilium therapeutics: Patents & Royalties: There is an existing license agreement between TTI and University Health Network and J.C.Y.W. may be entitled to receive financial benefits further to this license and in accordance with UHN's intellectual property policies. .

Ruxolitinib is the first available JAK inhibitor (JAKi) therapy for amelioration of constitutional symptoms or splenomegaly in myelofibrosis (MF). Duration of response varies, as patients discontinue ruxolitinib due to disease progression or drug toxicity. Ruxolitinib failure is a poorly defined clinical entity, but may include suboptimal or lost spleen response, worsening cytopenias, accelerated or blast phase (AP/BP) progression, or non-hematologic side effects. It is not clear what other clinical parameters should be considered indicative of JAKi failure. Leukocytosis is a known prognostic factor in MF and is included in various prognostic models. We have observed that some patients on stable doses of JAKi therapy develop progressive leukocytosis in the absence of other signs of MF progression. The significance of this event is not known, and it is not clear whether the onset of leukocytosis should prompt changes in clinical management. To assess the clinical significance of emergent leukocytosis, we evaluated leukocyte counts in our database of MF patients receiving Ruxolitnib or Momelotinib as first-line JAKi therapy. We defined emergent leukocytosis as any of:New onset of WBC ≥25 x 109/L in patients with WBC ≤12.5 x 109/L at JAKi start.Doubling of WBC from the nadir value in patients with WBC >12.5 x 109/L at JAKi start and nadir WBC >12.5 x 109/L.WBC ≥25 x 109/L in patients with WBC > 12.5 x 109/L at JAKi start after attaining a nadir WBC ≤12.5 x 109/L. Leukocytosis had to be sustained over consecutive blood counts at least one month apart and had to occur in the absence of infection, steroid therapy, AP/BP transformation, splenectomy or JAKi dose reduction. Exclusion criteria included concurrent hematologic diagnoses, and splenectomy or AP/BP MF preceding JAKi initiation. Of 290 patients with MF receiving JAKi therapy, 217 met study criteria. Of these 217 patients, 27 developed emergent leukocytosis while receiving JAKi. The cumulative incidence of leukocytosis was 4%, 10% and 15% at 1, 3, and 5 years from the start of JAKi therapy, respectively. Transformation to AP/BP, splenectomy, bone marrow transplant, or death from any cause were considered as competing risks in the calculation of cumulative incidence. In a multivariate analysis, clinical parameters associated with emergent leukocytosis included presence of baseline anemia (HR 4.94 [95% CI, 1.13-21.53]; p = 0.03) or leukocytosis (HR 5.01 [95% CI, 1.44-17.41]; p = 0.01) at JAKi start and female gender (HR 0.21 for male [0.08-0.06]; p=0.002). Baseline leukocytosis as WBC ≥25 x 109/L, and anemia was as a hemoglobin In patients with available targeted sequencing performed prior to JAKi therapy (n=141, 65%), TET2 mutations were associated with increased risk of leukocytosis (HR 5.48 [95% CI, 1.73-17.35]; p=0.004), but JAK2, CALR, MPL or ASXL1 mutations were not. Among 27 patients who experienced emergent leukocytosis, 21 were deceased while 6 are in ongoing follow-up. Median overall survival calculated from the date of leukocytosis was 14 months [95% CI, 8.6-27.9]. Overall, 7 patients transformed to AP/BP, 7 died from progressive MF, 4 underwent transplant, one underwent splenectomy, 6 died of miscellaneous causes and two remain on first-line JAKi without any complicating events. Among 27 patients experiencing leukocytosis, paired samples for molecular analysis at JAKi initiation and at the time of leucocytosis were available in 21 (78%). Results from targeted sequencing of a panel of 49 myeloid genes were available from 4 patients with paired samples (Table 1). New mutations at leukocytosis were seen in NRAS and CEBPA in the first patient, KRAS and SH2B3 in the second, and CBL in the third. The fourth patient acquired no new mutations but demonstrated marked expansion of a dominant clone. The remaining 17 paired samples have been submitted for sequencing with results pending. In summary, MF patients with baseline anemia, leukocytosis, or female gender are at higher risk for emergent leucocytosis while on JAKi therapy. The median overall survival of 14 months in patients who experience emergent leukocytosis is comparable to that observed in patients following ruxolitinib failure. Our data also suggest that onset of leukocytosis may be indicative of underlying clonal evolution, which will need to be confirmed in a larger number of patients. These findings suggest consideration of emergent leukocytosis as a criterion for JAKi failure in MF. Disclosures Maze: Novartis: Honoraria; Pfizer: Consultancy; Takeda: Research Funding. Gupta:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sierra Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bristol MyersSquibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy; Incyte: Honoraria, Research Funding.

There is a paucity of data regarding the impact of mutations on outcomes in accelerated-phase (AP) and blast-phase (BP) myeloproliferative neoplasms (MPNs). Moreover, it is unknown whether mutational status affects survival, as seen in chronic-phase MPNs. Therefore, we performed a retrospective analysis of all patients treated at our institution with AP/BP MPNs (N = 122; AP = 14; BP = 108) to comprehensively describe the mutational profile and correlate with clinical outcomes. Targeted sequencing with a 54-gene panel was performed. Forty-four patients were treated with intensive therapy, 27 with nonintensive therapy, and 51 with best supportive care (BSC). The most common mutation was JAK2V617F, occurring in 55% of subjects; CALR was found in 13% of patients and MPL in 6%. Thirty-two (26%) patients were triple negative. Other frequently mutated genes were ASXL1 (30%), TET2 (25%), SRSF2 (22%), RUNX1 (20%), and TP53 (17%). Mutations in 1, 2, 3, and ≥4 genes were seen in 15%, 13%, 25%, and 46% of patients, respectively. There was no difference in survival between patients treated with intensive vs nonintensive therapy, and the benefit of intensive therapy was limited to patients who were able to undergo transplantation. TP53 was the only individual mutation to correlate with shorter overall survival (hazard ratio, 1.89; P = .03). In the multivariate analysis, mutated TP53, ≥4 mutations, low albumin, increased peripheral blood blasts, ≥3 cytogenetic abnormalities, and BSC were associated with shorter survival. In conclusion, mutational data enhance the understanding of patients with AP/BP MPN who are likely to benefit from current therapeutic options.

We evaluated outcomes of 100 patients with high risk AML treated with Ida-FLAG induction as first-line therapy. 72 achieved remission with one cycle; 19 did not. High risk cytogenetics and TP53 mutations were associated with failure to achieve remission. In those reaching remission, allogeneic bone marrow transplantation was associated with better relapse-free and overall survival. Those not achieving remission with induction therapy were extremely unlikely to reach remission with further therapy and had a dismal prognosis. Exploratory molecular analysis confirmed persistence of the dominant genetic mutations identified at diagnosis. Ex vivo chemosensitivity did not demonstrate significant differences between responders and non-responders. Thus, Ida-FLAG induction has a high chance of inducing remission in patients with high risk AML. Those achieving remission require allogeneic transplantation to achieve cure; those not achieving remission rarely respond to salvage chemotherapy and have a dismal outcome. Alternatives to conventional chemotherapy must be considered in this group.

Background: AML is driven by a small subpopulation of leukemia stem cells (LSCs), which possess stem-cell properties such as quiescence and self-renewal that are linked to therapy resistance and relapse. The LSC17 score was derived from genes differentially expressed between functionally validated LSC+ and LSC- cell fractions from 78 AML patients. The LSC17 score was strongly associated with survival in 4 independent cohorts of AML patients treated with curative intent (n = 908), and accurately predicted initial response. Patients with high LSC17 scores had poor outcomes with standard treatment strategies. The LSC17 score remained highly significant in multivariate analyses, independent of commonly used prognostic factors. A critical advantage of the LSC17 test over cytogenetic analysis is its rapid turnaround time (24-48h on a NanoString platform), providing clinicians with a powerful tool for upfront risk stratification. To date, no RNA-based, stem cell-derived score has been transitioned into a Clinical Laboratory Improvement Amendments (CLIA) certified laboratory. Study design and methods: The study consists of 2 phases. Phase 1 aims to validate the assay in a CLIA certified laboratory setting. Phase 2 aims to determine prospectively the feasibility and prognostic power of LSC17 score testing in newly diagnosed AML patients in the real-world setting. Clinical endpoints include primary induction failure rate, relapse free survival and overall survival. All patients with a suspected diagnosis of de novo or secondary AML, who are deemed fit and appropriate by their treating physician to undergo intensive induction chemotherapy, are considered for this study. Patients who received any prior anti-leukemia treatments (except hydroxyurea) and patients with a confirmed diagnosis of acute promyelocytic leukemia are excluded. Current participating centres include Princess Margaret Cancer Centre (Toronto), Juravinski Cancer Centre (Hamilton), and The Ottawa Hospital Cancer Centre (Ottawa). Pre-study sample size analysis suggests that 150 patients will be required to demonstrate a hazard ratio for death of 2.3 between patients with a high and low LSC17 score (α = 0.05, power = 0.8). The survival for the high and low LSC17 score groups will be compared using the Cox proportional hazards model. Traditional risk stratification will also be tested within a Cox proportional hazards model. Phase 1 of the study has been completed and several key quality control measures have been created. Initial derivation and validation of the LSC17 score was performed using standard chemistry on the NanoString platform; for CLIA lab validation, the assay was transitioned to Elements© chemistry, which does not require custom codeset manufacture by NanoString. The original AML reference cohort was retested using Elements© chemistry to derive an absolute median threshold for prospective LSC17 score determination in individual patients. The lab validation process compared and found no difference in LSC17 scores between samples processed by Ficoll or collected in Paxgene for ease of processing. A standardised quality assurance (QA) process was completed to identify optimal sample requirements as well as specimen storage conditions, score stability during sample storage and turnaround time for testing. An algorithm has been created using the laboratory information system to allow standardised and rapid calculation of the LSC17 score from NanoString nCounter output data. The LSC17 score can be tested on peripheral blood or bone marrow, although bone marrow samples are preferred for patients with very low peripheral blast counts. Samples are ideally stored in RNA Paxgene tubes for RNA stability and to maximize RNA yield. The prospective phase of the study (Phase 2) opened in April 2018 and as of June 2019, 233 patients have been enrolled, of which 120 received induction chemotherapy. 54 patients were excluded due to an alternative diagnosis or failed QA. The remaining patients had non-intensive therapy based on patient choice. Standard prognostic markers including cytogenetics, molecular studies and targeted sequencing using a 49-gene AML panel are performed in parallel to the LSC17 score. Treatment was administered according to physician preference, based on patient history and results of standard prognostic assays, when available. The study continues to recruit and is open to collaborations in other centres. Disclosures Ng: Celgene: Research Funding. Leber:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Honoraria, Membership on an entity's Board of Directors or advisory committees; Jazz: Honoraria, Membership on an entity's Board of Directors or advisory committees; Alexion: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Sabloff:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas Pharma Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; ASTX: Membership on an entity's Board of Directors or advisory committees, Research Funding; Jazz Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer Canada: Honoraria, Membership on an entity's Board of Directors or advisory committees; Actinium Pharmaceuticals, Inc: Membership on an entity's Board of Directors or advisory committees; Novartis Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Sanofi Canada: Research Funding. Minden:Trillium Therapetuics: Other: licensing agreement. Wang:NanoString: Other: Travel and accommodation; Trilium therapeutics: Other: licensing agreement, Research Funding; Pfizer AG Switzerland: Honoraria, Other: Travel and accommodation; Pfizer International: Honoraria, Other: Travel and accommodation.

Introduction Core-binding factor (CBF) acute myeloid leukemias (AML) are characterized by the chromosomal abnormalities t(8;21) or inv(16)/t(16;16) and their fusion proteins RUNX1/RUNX1T1 and CBFB-MYH11, respectively. Despite their relatively favorable prognosis, it has been reported that up to 45% of patients with CBF-AML relapse. Current guidelines recommend monitoring the peripheral blood (PB) or bone marrow (BM) for molecular evidence of residual disease (RD) every 3 months for 2 years following remission. By monitoring patients for rising molecular transcripts, those at risk of impending relapse can be identified and treated prior to the emergence of overt disease. However, the relapse kinetics of CBF-AML are poorly-understood, and it is unknown if serial RD monitoring can detect molecular relapses with sufficient lead-time to intervene and prevent morphologic relapse. Methods After local REB approval, we identified patients with CBF-AML treated at the Princess Margaret Cancer Centre in Toronto, Canada between 2000 and 2017. Patients underwent induction and consolidation chemotherapy according to standard protocols followed by RD monitoring with polymerase chain reaction (qPCR) of RUNX1/RUNX1T1 or CBFB-MYH11 transcripts in a CAP/CLIA certified lab every 3 months for a median of 1.2 years (range 0-5.3). RD assessment was performed on BM aspirates, but PB could be tested in patients who could not tolerate repeat BM aspirates. Morphologic relapse was defined as emergence of >5% blasts in the PB or BM, and molecular relapse as a positive transcript PCR (if previous PCR measurements were undetectable) or an increase by 1 log (if previous PCR measurements were detectable) on 2 successive samples without morphologic relapse. Rapid relapse was defined as Results We included 114 patients with CBF-AML. Median age was 46.5 years (range 18-79). t(8;21) was present in 59% and inv(16)/t(16;16) in 41% of patients. All patients achieved remission with 7+3 induction chemotherapy. Over a median follow-up time of 3.7 years (range 0.2-14.3), RD measurements were performed a mean of 5 times per patient with mean sampling interval of 103±54 days. Remission was maintained in 71 (62%) patients but 43 (38%) developed morphological (n=34) or isolated molecular relapse (n=9), with median time to relapse of 4.4 months (range 1.4-31.4). Patients with relapsed disease were significantly less likely to have achieved ≥3 log reduction in RUNX1/RUNX1T1 or CBFB-MYH11 BM transcripts at the end of consolidation chemotherapy compared to patients who remained in remission (75% vs 90%, p=0.046). Of the 43 patients who relapsed, the majority (74.4%, n=32) had rapid relapse kinetics. Of these 43 patients, 25 received reinduction chemotherapy with achievement of CR2, 6 had refractory disease or death, 1 was lost to follow-up, and 17 went on to receive allotransplantation. RD monitoring enabled timely detection of impending relapse and permitted intervention prior to morphologic relapse in only 11 patients (25.6%). Among these 11 patients with slower relapse kinetics, 6 received reinduction chemotherapy with achievement of CR2, 2 received reinduction chemotherapy with refractory disease, and 8 went on to receive allotransplantation. Median overall survival was 20 months (range 3-128) for patients with rapid relapse kinetics and 28 months (range 14-166) for patients with slow relapse kinetics (p=0.02). Clinical features, BM vs PB RD measurements, additional molecular mutations, and cytogenetic abnormalities did not distinguish patients with rapid vs slow relapse kinetics. Conclusions Current guidelines recommend molecular RD monitoring every 3 months for CBF-AML. However, in the majority of patients who relapsed at our institution, RD monitoring every 3 months provided insufficient lead-time to identify molecular relapses prior to morphologic relapse. Further research is warranted to identify the patients with CBF at the highest risk of relapse and the best strategies to monitor these patients over time. Disclosures Gupta: Novartis: Consultancy, Honoraria, Research Funding; Incyte: Research Funding. Maze:Novartis: Consultancy, Honoraria. Schuh:Celgene: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; Jazz: Consultancy; Amgen Inc.: Consultancy; Shire: Consultancy; Teva: Consultancy; Otsuka: Consultancy. Yee:Celgene, Novartis, Otsuka: Membership on an entity's Board of Directors or advisory committees; Agensys, Astex, GSK, Onconova, Genentech/Roche: Research Funding. Schimmer:Otsuka Pharmaceuticals: Consultancy; Jazz Pharmaceuticals: Consultancy; Medivir AB: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees.

Acute myeloid leukemia (AML) is a clinically and biologically heterogeneous disease. Traditionally, cytogenetic analysis has been the backbone for prognostication and treatment decisions. Outcomes vary between age groups with older adults generally having a poorer prognosis. Next Generation Sequencing (NGS) has expedited the discovery of novel genetic lesions in AML to better predict response to intensive chemotherapy and overall survival (OS). The aims of our study were to describe the genetic profile of older adults with AML and to determine its impact on treatment response and survival. We included all new patients with a diagnosis of AML (≥20% blasts in peripheral blood or bone marrow; acute promyelocytic leukemia and myeloid sarcoma were excluded), treated at Princess Margaret Cancer Centre between February 2015 and August 2017. NGS was performed on DNA isolated from peripheral blood or bone marrow samples at diagnosis. Analysis was performed using the TruSight Myeloid Sequencing Panel (Illumina; San Diego, CA) on the MiSeq benchtop genome sequencer (Illumina). Of the 54 genes included in the panel, the complete coding region was sequenced in 15, with hotspot region coverage provided for 39. Demographic and clinical data were obtained from the Princess Margaret Cancer Centre Registry. We identified 454 patients with a new diagnosis of AML in whom frontline NGS was performed. Of these, 300 were 60 years (range 60-92) or older. Demographic and clinical data are shown in Table 1. The median age overall at presentation was 67 yrs (range 18-92) and 57% were male. de novo AML was diagnosed in 329 patients (72%), secondary AML in 17%, and therapy related myeloid neoplasm in 11%. Secondary AML (sAML) was more frequently seen in the ≥60 vs the In total 283 patients (62%) received intensive chemotherapy (95% in the younger group and 45% in the older cohort). 216 patients (76%) achieved a response (CR/CRi/morphologic leukemia free state). No statistically significant difference was seen between age groups (P=0.73) NGS detected 1655 variants. Of these, 1353 classified as oncogenic and 302 as variants of unknown significance (the latter were excluded from subsequent analysis). 14 patients had no mutations identified by NGS. Forty three genes were recurrently mutated in the study cohort: 36 were mutated in >1% of patients, and 11 genes were mutated in >10% of patients. The most commonly mutated genes included DNMT3A (25%), NPM1 (21%), TET2 (19%), RUNX1 (16%), TP53 (16%), ASXL1 (15%), IDH2 (15%), SRSF2 (15%), NRAS (12%), and IDH1 (11%). Older patients had a greater number of mutations overall compared to younger adults (median: 3 vs 2; P = 0.001). In total 986 oncogenic variants were identified in the older group (median 3, range 1-12), while 367 oncogenic variants (median 0, range 0-2) were present in patients < 60 years old (P < 0.001). The older group more commonly harbored mutations in TET2 (25 vs 10%), ASXL1 (21 vs 4%), RUNX1 (20 vs 8 %), SRFS2 (20 vs 6 %), STAG2 (11 vs 6%) and U2AF1 (8 vs 2%). Patients with PTPN11 and NPM1 mutations had longer OS, while patients carrying mutations in ASXL1, JAK2, RUNX1, TP53 and SRSF2 had a shorter OS (Table 2). No differences in OS between age groups (P= 0.2). Multivariate Cox regression analysis showed that male sex (P= 0.0057), sAML (P We then analyzed the correlation between mutations and response rate in patients receiving intensive treatment. PTPN11 and NPM1 mutations were associated with a greater likelihood of achieving a response, while patients with mutations in BCOR, TP53, SF3B1 and U2AF1 had a lower chance of response. Multivariate Cox regression analysis of mutations known to affect response did not show any differences by age, gender, or diagnosis. Mutations in BCOR (P= 0.045), TP53 (P= 0.032) and U2FA1 (P=0.019) were significantly associated with primary induction failure. Overall, older AML patients harbored a greater number of mutations than did their younger counterparts. No age-related differences were observed in mutations known to affect response and/or OS. TP53 mutations, adverse cytogenetics and sAML, were poor prognostic factors regardless of age. Disclosures Schimmer: Medivir AB: Research Funding; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Consultancy; Otsuka Pharmaceuticals: Consultancy. Yee:Agensys, Astex, GSK, Onconova, Genentech/Roche: Research Funding; Celgene, Novartis, Otsuka: Membership on an entity's Board of Directors or advisory committees. Gupta:Novartis: Consultancy, Honoraria, Research Funding; Incyte: Research Funding. Maze:Novartis: Consultancy, Honoraria. Schuh:Novartis: Consultancy; Otsuka: Consultancy; Pfizer: Consultancy; Teva: Consultancy; Celgene: Consultancy; Amgen Inc.: Consultancy; Shire: Consultancy; Jazz: Consultancy.

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease. Multiple genetic and environmental factors contribute to the pathogenesis of this disease. Recent genome-wide association studies have added substantially to the number of genes associated with SLE. To replicate some of these susceptibility loci, single-nucleotide polymorphisms reported to be associated to SLE were evaluated in a cohort of 245 well-phenotyped Canadian SLE trios. Our results replicate previously reported associations to alleles of interferon regulatory factor 5 (IRF5), major histocompatibility complex (MHC), tumor necrosis factor (ligand) superfamily member 4 (TNFSF4), Kell blood group complex subunit-related family member 6 (XKR6), B-cell scaffold protein with ankyrin repeats 1 (BANK1), protein tyrosine phosphatase non-receptor type 22 (PTPN22), ubiquitin-conjugating enzyme E2L 3 (UBE2L3) and islet cell autoantigen 1 (ICA1). We also identify putative associations to cytotoxic T-lymphocyte-associated protein 4 (CTLA4), a gene associated with several autoimmune disorders, and ERBB3, a locus on 12q13 that was previously reported to be associated with type 1 diabetes. This study confirms the existence of multiple genetic risk factors for SLE, and supports the notion that some risk factors for SLE are shared with other inflammatory disorders.

HACS1 is a Src homology 3 and sterile alpha motif domain–containing adaptor that is preferentially expressed in normal hematopoietic tissues and malignancies including myeloid leukemia, lymphoma, and myeloma. Microarray data showed HACS1 expression is up-regulated in activated human B cells treated with interleukin (IL)-4, CD40L, and anti–immunoglobulin (Ig)M and clustered with genes involved in signaling, including TNF receptor–associated protein 1, signaling lymphocytic activation molecule, IL-6, and DEC205. Immunoblot analysis demonstrated that HACS1 is up-regulated by IL-4, IL-13, anti-IgM, and anti-CD40 in human peripheral blood B cells. In murine spleen B cells, Hacs1 can also be up-regulated by lipopolysaccharide but not IL-13. Induction of Hacs1 by IL-4 is dependent on Stat6 signaling and can also be impaired by inhibitors of phosphatidylinositol 3-kinase, protein kinase C, and nuclear factor κB. HACS1 associates with tyrosine-phosphorylated proteins after B cell activation and binds in vitro to the inhibitory molecule paired Ig-like receptor B. Overexpression of HACS1 in murine spleen B cells resulted in a down-regulation of the activation marker CD23 and enhancement of CD138 expression, IgM secretion, and Xbp-1 expression. Knock down of HACS1 in a human B lymphoma cell line by small interfering ribonucleic acid did not significantly change IL-4–stimulated B cell proliferation. Our study demonstrates that HACS1 is up-regulated by B cell activation signals and is a participant in B cell activation and differentiation.

Recent studies have demonstrated that the malignant Reed-Sternberg cells of Hodgkin’s lymphoma (HL) secrete and are responsive to interleukin (IL)-13. We hypothesized that overexpression of a soluble IL-13 decoy receptor (sIL-13Rα2) via adenoviral-mediated gene transfer would inhibit IL-13-induced Reed-Sternberg cell proliferation. Western blot and ELISA analysis verified expression of sIL-13Rα2 in cell lysates and supernatants of AdsIL-13Rα2-transduced COS-7 cells. Treatment of two IL-13-responsive HL-derived cell lines, HDLM-2 and l-1236, with AdsIL-13Rα2-conditioned medium, resulted in the inhibition of cell proliferation, and down-regulated the phosphorylation of signal transducer and activator of transcription 6 (STAT6), an important mediator of IL-13 signaling. i.v. delivery of AdsIL-13Rα2 in NOD/SCID mice with s.c. implanted HDLM-2 cells delayed tumor onset and growth while enhancing survival compared with control mice. Intratumoral administration of AdsIL-13Rα2 led to the regression or stabilization of established tumors and was associated with diminished STAT6 phosphorylation. Our data demonstrate that AdsIL-13Rα2 can suppress HL growth in vitro and in vivo.

SH3 and SAM domains are protein interaction motifs that are predominantly seen in signaling molecules, adaptors, and scaffold proteins. We have identified a novel family of putative adaptor genes that includes HACS1. HACS1 encodes a 441 amino acid protein that is differentially expressed in hematopoietic cells and has restricted expression in human tissues. Its SH3 domain is most similar to the same motif in Crk and its SAM domain shares homology with a family of uncharacterized putative scaffold and adaptor proteins. HACS1 maps to human chromosome 21q11.2 in a region that is frequently disrupted by translocation events in hematopoietic malignancies. Polyclonal antibodies against HACS1 recognized a 49.5 kDa protein whose mRNA is expressed in human immune tissues, bone marrow, heart, lung, placenta and brain. Cell lines and primary cells from acute myeloid leukemias and multiple myeloma patients express HACS1. Immunostaining and cellular fractionation studies localized the HACS1 protein predominantly to the cytoplasm.

Introduction: The advent of next generation sequencing (NGS) has brought intense interest to the complex genetic landscape of myeloproliferative neoplasms (MPN). However, data regarding clinical outcomes in the context of novel MPN therapies such as JAK inhibitors are scarce. Limited data indicate that high molecular risk signature (HMR, presence of at least one mutation in ASXL1, EZH2, IDH1/2, SRSF2) or multiple mutations may be associated with decreased spleen response and a shorter time to discontinuation of Ruxolitinib in myelofibrosis (Patel et al, Blood 2015). Methods: All myelofibrosis patients seen in the MPN program at Princess Margaret Hospital between November 2009 and May 2016 and treated with JAK1/2 inhibitor therapy were identified. NGS molecular profiling of 54 genes (39 hotspot region; 15 complete coding region coverage) was performed on peripheral blood or bone marrow samples using the TruSight Myeloid Sequencing Panel. Reporting was restricted to well-covered, exonic nonsynonymous, intronic splice site, and known pathogenic synonymous variants. Variants with global mean allele frequency >1% were identified using multiple population databases (1000 genomes, ESP, ExAC) and excluded. The primary endpoint was time from start of JAK1/2 inhibitor therapy to treatment failure (TTF) defined as treatment discontinuation, progression to accelerated phase or leukemic transformation, spleen progression or death. Secondary endpoints included best spleen, anemia and IWG response achieved by 48 weeks of treatment and overall survival. Response was assessed according to the 2013 revised IWG-MRT criteria. Transfusion dependency was assessed as any transfusion in 12 weeks prior to treatment or being identified as transfusion dependent in medical history. Results: Of 159 patients treated with JAK1/2 inhibitors at our institution, 102 met the inclusion criteria (see Table 1). Patients were excluded if; no sample was available for analysis (19), short use of JAK inhibitor prior to transplant (9), active clinical trial (5), in accelerated phase/acute leukemia (4) and others (20). First JAK inhibitor used was ruxolitinib in 77 patients and momelotinib in 25. At least one mutation was identified in every patient. Twenty (20%) patients had one mutation, 32 (31%) had 2 mutations and 50 (49%) patients had ≥ 3 mutations. Eighty (82%) patients had the JAK2V617F mutation, 15 (15%) had mutations in CALR, 4 (4%) had MPL mutations and one patient was triple negative. One patient had mutations in both CALR and JAK2 while another had mutations in MPL and CALR. Forty-eight (47%) patients had mutations consistent with HMR profile. Mutation profile is summarized in Table 2. With median follow-up of 2.5 years, 51 (50%) patients experienced treatment failure. On univariate analysis, TTF was associated with DIPSS, pre-treatment transfusion status and Hb Conclusions: In this study of myelofibrosis patients treated with JAK inhibitors, EZH2 and CBL mutated patients had shorter TTF. We did not find any association between TTF and number of mutations or other high risk mutations such as ASXL1/SRSF2. Anemia was the only significant independent predictor of shorter TTF. Our findings highlight the need for multicenter collaborative studies on a large number of patients and cautious use of mutation profiling results in routine clinical decision making with current treatment approaches. Spiegel and McNamara are co-primary authors. Disclosures Panzarella: Cellgene: Consultancy. Schimmer:Novartis: Honoraria. Schuh:Amgen: Membership on an entity's Board of Directors or advisory committees. Yee:Novartis Canada: Membership on an entity's Board of Directors or advisory committees, Research Funding. Kamel-Reid:BMS: Research Funding. Gupta:Novartis: Consultancy, Honoraria, Research Funding; Incyte Corporation: Consultancy, Research Funding.

Neurofibromatosis type 2 (NF2) is an autosomal dominant genetic disorder characterized by the development of bilateral vestibular schwannomas, meningiomas, ependymomas and juvenile lens opacities. The NF2 gene encodes a tumor suppressor protein, schwannomin (or merlin), with sequence homology to erythrocyte band 4.1, talin, ezrin, moesin and radixin. Using an antibody that recognizes the carboxy-terminal epitope of isoform 1 of schwannomin, we looked at its expression in lens and Schwann cells, two cell-types affected by the NF2 phenotype. Schwannomin was detected as an approximately 80 kDa protein in both cytoplasmic and cytoskeleton fractions. Indirect immunofluorescence localized schwannomin to the cytoplasm and was frequently observed in dynamic cellular regions such as leading edges and ruffling membranes. Its level of expression in the lens inversely correlates with the degree of lens cell differentiation suggesting a role for schwannomin in differentiation-specific events.

Neurofibromatosis type 2 (NF2) is an autosomal dominant disease in which loss of function mutations of the NF2 gene lead to the development of schwannomas, meningiomas and juvenile cataracts. We studied the mouse NF2 homologue (Nf2) to determine its precise pattern of mRNA and protein expression. In situ hybridization showed that Nf2 is expressed in neuronal cells as well as in epithelial and fibre cells of the lens. The Nf2 protein, schwannomin, is expressed as a single protein isoform of approximately 80 kDa in neuronal and non-neuronal tissues. In Purkinje cells of the cerebellum and motor neurones of the spinal cord, the protein is in the cytoplasm. In non-neuronal tissues immunostaining showed expression in cells of the tunica intima of blood vessels. We conclude that there is a widespread but cell type-specific expression of schwannomin.