Steensma, David P.

Abstract INTRODUCTION: The majority of patients (pts) with MDS become red blood cell (RBC) transfusion dependent with escalating risk for transfusional hemosiderosis and its adverse effect on morbidity and mortality. The US03 trial is designed to evaluate long-term efficacy and safety of the oral iron chelator, deferasirox (DFX), in pts with lower risk MDS. In this ongoing study 53 pts have completed 12 months’ (mos) treatment. METHODS: US03 is a Phase II, open-label, 3-year trial in pts with Low- or Int-1 IPSS risk MDS and transfusional iron overload (SF ≥1000 μg/L and >20 units RBC transfusions [tx]), with serum creatinine (SCr) ≤2-fold the upper limit of normal (ULN). Initial DFX dose was 20 mg/kg/day and could be increased to 40 mg/kg/day based on tolerability and response. SF was monitored monthly; LPI, the reactive species of non-transferrin-bound iron, was assessed quarterly. BASELINE FEATURES: 176 pts were enrolled at 45 centers. Mean age was 70 years (range, 21−90), including 102 men, 71 women; and IPSS risk groups of Low 46 pts (27%), Int-1 123 (71%), other 4 (2%). Mean baseline iron status: SF 3398 μg/L (range, 863−36,280); LPI 0.4 μmol/L (0.0−3.6); mean lifetime txs prior to study, 63; years of prior tx 3.5 (0−34). MDS therapy at study entry included chemotherapy, 22 pts; growth factors, 46. Estimated creatinine clearance: normal (>80 mL/min), 77 pts; mild (51−80 mL/min), 68; moderate, (30–50 mL/min) 25; severe (<30 mL/min) 2. Over 12 mos the mean dose was 21 mg/kg/day, and the mean tx rate was 4.1 units/mo. Forty percent of pts had elevated LPI at baseline (≥0.5 μmol/L). RESULTS: Mean SF±SD (μg/L) values: baseline 3398±3088; 3 mos 3065±1743; 6 mos 2775±1355; 9 mos 2759±1562; 12 mos 2603±1336. Sustained suppression of mean LPI to the normal range was achieved after 3 mos of treatment. (Figure shows changes in SF and LPI). Hematologic improvement by IWG criteria: 5 pts (6%); erythroid response: 3 (major 1; minor 2); platelet 2 (major); neutrophil 1 (major). SAFETY: Of 165 pts, only 10 (6%) discontinued secondary to suspected adverse events (AEs), and 7 (4%) serious AEs. There were 11 deaths (7%), all unrelated to DFX. Of 140 pts with normal baseline SCr, 35 (25%) increased >ULN (2.2 mg/dL max SCr). SCr increased >33% above baseline in 11 pts (8%) abnormal at baseline. New onset of thrombocytopenia and neutropenia were 52/165 (32%) and 22/165 (13%), respectively. CONCLUSIONS: DFX therapy decreased mean SF over 1 year in this heavily iron-replete MDS population. Trough LPI normalized in 100% of pts over 12 mos, indicating 24-hour sustained suppression. DFX had a manageable safety profile in this population; new cytopenias were consistent with hematologic progression of MDS. Recent reviews show a 30% increase in hazard ratio for every 500 ng/mL increase in SF >1000 ng/mL; NCCN guidelines recommend consideration of iron chelation in iron-overloaded MDS pts. Ongoing assessments evaluating cardiac, hepatic and endocrine function will evaluate the impact of iron reduction on morbidity and mortality in MDS. Figure Figure

Abstract Introduction: The core-binding factor subunit RUNX1/CBFA2/AML1 (Runt-related transcription factor 1, Core-binding factor alpha 2 subunit, Oncogene AML1) is critical for generation of hematopoietic stem cells during embryogenesis and for normal megakaryopoiesis in adults. RUNX1/CBFA2/AML1 has long been recognized as an oncogene, and is frequently involved in leukemia-associated translocations that create aberrant fusion proteins (e.g., AML1-ETO). Recently, acquired somatic point mutations in the RUNX1/CBFA2/AML1 gene have been described in a subset of patients with myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). These point mutations are associated with the loss of normal RUNX1 trans-activation potential and/or altered binding to the non-DNA-binding subunit of core-binding factor, CBFB. Given the importance of core-binding factor in megakaryocytic differentiation and platelet production and the central role of megakaryocytes in the pathophysiology of myelofibrosis with myeloid metaplasia (MMM), and in light of the myelofibrotic phenotype of GATA-1low mice (GATA-1 and RUNX1 are co-expressed and co-operate in megakaryocytic differentiation), we hypothesized that RUNX1 gene mutations might be common in MMM. In addition, we wanted to know whether patients with MDS-associated acquired alpha thalassemia (i.e., ATMDS), a special MDS subgroup with a very high incidence of point mutations in the X-linked ATRX gene, have an especially high incidence of RUNX1 mutations that might account for the more severe hematopoietic defect found in these patients compared with boys with inherited ATR-X syndrome (detailed in Steensma et al, Blood2004;103:2019). Methods and Results: We analyzed samples from 26 well-characterized patients with MMM and from 52 with MDS (11 RA, 3 RARS, 8 RCMD, 3 RAEB-1, 7 RAEB-2, 2 MDS in transition to AML-M6, 14 atypical/unclassifable MDS, 4 MDS subtype unknown - including 18 with ATMDS) for RUNX1 point mutations by denaturing high-performance liquid chromatography (DHPLC) followed by subcloning and sequencing of samples exhibiting heteroduplex peaks. We found 5 RUNX1 mutations in MDS patients (9.6%), all of whom had RAEB-2 (4 patients) or a history of treated AML (1 patient), but detected no mutations in MMM patients. All patients with RUNX1 mutations progressed to overt leukemia within 1 year. ATMDS patients did not have an increased risk of RUNX1 point mutations (2/18 patients with mutations, 11.1%) when compared with MDS without thalassemia (3/34 patients, 8.8%; p=0.58). Additionally, 1 MDS patient had a clonally restricted mutation in GATA-1 (c.1066 C>T) (also screened by DHPLC), but this is not predicted to change the GATA-1 amino acid sequence and is likely a random event reflecting the genomic instability characteristic of MDS. Conclusion: RUNX1 point mutations are common in high-risk MDS, but not in MMM, and that ATMDS patients do not have a risk of RUNX1 mutations in excess of that expected for MDS in general.

7077 Background: MDS includes a heterogenous group of hematopoietic stem cell malignancies characterized by ineffective hematopoiesis and recurring clonal cytogenetic abnormalities with poorly understood functional consequences. Interstitial deletion of chromosome 5 including band q31 is of special interest currently because of the striking effectiveness of lenalidomide therapy in patients with this lesion. Methods: We reviewed the clinical and pathological features of 175 consecutive patients with 5q31 deletions whose final diagnosis was MDS from 1996 to 2006. Patients not meeting the definition of a clonal chromosomal anomaly (i.e., only 1 abnormal metaphase) and those with >20% marrow blasts (now defined as AML) were excluded. Results: The median age at diagnosis was 73 years old (range 8–91). The 5 most common MDS subtypes (WHO classification) were RAEB2 (38 cases), 5q- syndrome (33 cases), MDS NOS (26 cases), RCMD (22 cases), and RAEB1 (20 cases). Chromosomal breakpoints encountered most frequently were q13q33 (86 cases), q15q33 (38 cases), and q22q33 (14 cases). The 5q deletion was present as a sole cytogenetic anomaly in 31%, was present along with one other anomaly in 10%, and was part of complex karyotype in 59%. Median time to death from confirmation of diagnosis at our institution was only 7.2 months (range 1 month –1.8 years). Survival was greatest in those diagnosed with 5q- syndrome, but the median survival time of 1.8 years (p=0.001) was lower than reported in other series. Survival was also superior in women (7.9 months, versus 6.6 months for men, p=0.05) and those with non-complex cytogenetics (1.44 versus 0.41 years, p<0.001). Poorer survival was noted in those with prior chemotherapy (median 6.6 months versus 7.6 months, p=0.01). Differences in breakpoint (p=0.55) and number of metaphases involved with the 5q abnormality (p=0.08) did not have a statistically significant impact on survival. Conclusion: Classic 5q- syndrome as defined by the WHO represents only a minority of MDS patients with interstitial 5q deletions. Although the short survival in our series compared with previous reports may be due in part to referral bias, it is also possible that deletions of chromosome 5q are less benign than previously suspected. No significant financial relationships to disclose.

Background: Heterozygous somatic mutations in the genes encoding RNA splicing factors SF3B1, U2AF1, SRSF2 or ZRSR2 induce aberrant splicing in cancer cells and are among the most common mutations in patients with MDS, AML or CMML. H3B-8800 is an orally available small molecule that binds to the SF3b complex and induces alternative splicing changes in cells. Because splicing factor mutant cells depend on residual wild-type function of splicing factors for survival, we hypothesized that H3B-8800 would induce preferential cell killing of mutant cells by further perturbing splicing to synthetic lethality. In pre-clinical models, H3B-8800 preferentially kills spliceosome mutant cells and induces antitumor activity in xenograft leukemia models with core spliceosome mutations (Seiler M et al Nature Medicine 2018). Therefore, we conducted a phase I clinical trial (NCT02841540) of H3B-8800 in patients with MDS, AML or CMML. Here we describe the safety profile and clinical outcomes of the dose escalation cohorts in this phase I trial. Methods: This phase I trial explored the safety, pharmacokinetics (PK), and pharmacodynamics (PD) of H3B-8800 in patients with myeloid cancers. Dose escalation cohorts, employing a standard 3+3 design, examined 2 different once daily dosing regimens (schedule I: 5 days on/9 days off; schedule II: 21 days on/7 days off) in a 28-day cycle, with stratification based on lower-risk (LR) versus higher-risk (HR) myeloid neoplasms. Results: As of June 16th, 2019, 84 patients were enrolled at 24 centers in the US and Europe. Dose ranged from 1-40 mg among 65 patients on schedule I, while 19 patients were enrolled with dose ranging from 7-20 mg on schedule II. The patient population included AML (n=38), CMML (n=4), HR-MDS (n=20), LR-MDS (n=21) and 1 MDS with unknown risk level. Most patients (88%) had spliceosome mutations of interest. The most common mutations were in SRSF2 (p.P95H in 17, p.P95L in 9, p.P95_R102Del in 4), SF3B1 (p.K700E in 11, p.R625C in 4), and U2AF1 (p.Q157P in 6, p.S34F in 4). Patients remained on treatment from 7 to 819 days; 25 patients (30%) had time on treatment greater than 180 days, 20% more than 1 year and 2% over 2 years. The median therapy duration for LR-CMML/MDS, HR-CMML/MDS, and AML patients were 216, 62, and 47 days respectively. Most observed treatment related treatment-emergent adverse events (TEAEs) were Grade 1 or 2. The most common treatment-related (as judged by the investigator, &gt;10% frequency) TEAEs in the patients treated on schedule I were diarrhea (75%), nausea (37%), fatigue (28%) and vomiting (27%). The most common treatment-related TEAEs in the patients treated on schedule II were diarrhea (68%), vomiting (42%), QTc prolongation (21%), nausea (16%), and fatigue (16%). The most common dose limiting toxicity was prolongation of the QTcF interval &gt;500 msec (n=2, 40 mg on schedule I and n=1, 20 mg on schedule II, all ≥Grade 3) and bradycardia without other arrhythmias (n=1, 14 mg on schedule II, ≥Grade 3). No ophthalmic AEs were observed; 1 patient (LR-MDS) experienced durable marrow aplasia. The maximum tolerated dose (MTD) has not been confirmed for either Schedule I or Schedule II. PK analysis indicates that H3B-8800 is rapidly absorbed and exhibits dose-proportional increase in plasma exposure. Consistent dose-dependent target engagement (i.e., alteration in mature mRNA transcripts) was observed in blood mononuclear cells from patients enrolled in the 2 mg up to 40 mg dose cohorts on both schedules. Despite this splicing modulation, no objective complete responses (CR) or partial responses (PR) meeting International Working Group criteria were observed. One patient with CMML had a durable platelet response that began in Cycle 1 and persisted through Cycle 13. Nine red blood cell (RBC) transfusion-dependent patients with MDS or CMML and 2 patients with AML did not require RBC transfusions for ≥8 weeks (up to 28 weeks) while on study. One platelet transfusion-dependent patient with LR-MDS did not require platelet transfusions for ≥8 weeks. Conclusion: Results from this first-in-human multicenter prospective clinical trial of a splicing modulator in myeloid neoplasms demonstrate dose-dependent target engagement and predictable PK profile of H3B-8800, and safety even with prolonged dosing. Although no objective CR or PR were achieved, decreased RBC or platelet transfusion requirements were observed in 12 (14%) of enrolled patients. Disclosures Steensma: H3 Biosciences: Other: Research funding to institution, not investigator.; Pfizer: Consultancy; Aprea: Research Funding; Stemline: Consultancy; Arrowhead: Equity Ownership; Summer Road: Consultancy; Astex: Consultancy; Onconova: Consultancy. Wermke:Novartis: Honoraria, Research Funding. Greenberg:Notable Labs: Research Funding; Celgene: Research Funding; Genentech: Research Funding; H3 Biotech: Research Funding; Aprea: Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees. Font:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Komrokji:Agios: Consultancy; JAZZ: Speakers Bureau; DSI: Consultancy; JAZZ: Consultancy; Incyte: Consultancy; Novartis: Speakers Bureau; celgene: Consultancy; pfizer: Consultancy. Yang:Agios: Consultancy; AstraZeneca: Research Funding. Brunner:Astra Zeneca: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Forty Seven Inc: Membership on an entity's Board of Directors or advisory committees; Jazz Pharma: Membership on an entity's Board of Directors or advisory committees; Novartis: Research Funding. Ades:Agios: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Jazz: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Silence Therapeutics: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Helsinn Healthcare: Membership on an entity's Board of Directors or advisory committees. Al-Kali:Astex Pharmaceuticals, Inc.: Research Funding. Coombs:H3 Biomedicine: Research Funding. Foran:Agios: Honoraria, Research Funding. Garcia-Manero:Helsinn: Research Funding; Novartis: Research Funding; AbbVie: Research Funding; Celgene: Consultancy, Research Funding; Amphivena: Consultancy, Research Funding; Astex: Consultancy, Research Funding; Onconova: Research Funding; H3 Biomedicine: Research Funding; Merck: Research Funding. Micol:AbbVie: Consultancy; Jazz Pharmaceuticals: Consultancy. Perez De Oteyza:Celgene: Speakers Bureau. Wang:Abbvie: Other: Advisory role; Kite: Other: Advisory role; Jazz: Other: Advisory role; Astellas: Other: Advisory role, Speakers Bureau; celyad: Other: Advisory role; Pfizer: Other: Advisory role, Speakers Bureau; Stemline: Other: Advisory role, Speakers Bureau; Daiichi: Other: Advisory role; Amgen: Other: Advisory role; Agios: Other: Advisory role. Watts:Pfizer: Membership on an entity's Board of Directors or advisory committees; Jazz Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Takeda: Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees. Buonamici:H3 Biomedicine: Employment. Kim:H3 Biomedicine: Employment. Gourineni:H3 Biomedicine: Employment. Marino:H3 Biomedicine: Employment. Rioux:H3 Biomedicine: Employment. Schindler:H3 Biomedicine: Employment. Smith:H3 Biomedicine: Employment. Yao:H3 Biomedicine: Employment. Yuan:Eisai: Employment. Yu:H3 Biomedicine: Employment. Platzbecker:Abbvie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding. OffLabel Disclosure: H3B-8800 (experimental, unapproved)

Background: Current treatment options for red blood cell (RBC) transfusion-dependent (TD) patients with lower risk (LR) myelodysplastic syndromes (MDS) relapsed after or refractory to erythropoiesis-stimulating agents (ESAs) have limited efficacy and durability; new approaches are needed. Imetelstat is a 13-mer lipid-conjugated oligonucleotide that targets the RNA template of human telomerase and is a competitive inhibitor of telomerase enzymatic activity (Asai et al, Cancer Res 2003; Herbert et al, Oncogene 2005). Preclinical, in vivo xenograft models (Dikmen et al, Cancer Res 2005; Hochreiter et al, Clin Cancer Res 2006) and preliminary clinical data from a pilot study conducted at Mayo Clinic (Tefferi et al, Blood Cancer Journal 2016) supported initiation of a study in TD LR MDS patients. A Phase 2 study of imetelstat, IMerge, demonstrated an 8-week RBC transfusion independence (RBC-TI) rate of 42%, 24-week RBC-TI rate of 29%, and 68% erythroid hematologic improvement (HI-E) rate in 38 heavily TD patients (median prior RBC transfusion burden 8 units / 8 weeks over the 16 weeks pre-study period) with LR MDS. Responses were durable with median duration of 8-week RBC-TI of 85.9 weeks by Kaplan Meier estimates (range 8.0-140.9) (Steensma ASH 2018, Fenaux EHA 2019). These Phase 2 results provided further evidence of potential clinical benefit of imetelstat treatment in TD LR MDS, and supported initiation of a Phase 3 trial. Methods: IMerge is two-part, Phase 2/3 study (ClinicalTrials.gov: NCT02598661). The Phase 2 portion of the study described above is closed for enrollment. The Phase 3 portion of the study is open for enrollment of adult patients with International Prognostic Scoring System (IPSS) low or intermediate-1 risk, non-del(5q) MDS, who are TD, are relapsed after or refractory to ESAs, and have not received treatment with lenalidomide or hypomethylating agents. The study is a randomized (2:1) double-blind, placebo-controlled trial to compare efficacy of imetelstat vs. placebo that will enroll approximately 170 patients and will be conducted at approximately 90 centers in North America, Europe, Asia and Middle East. Imetelstat will be administered as 2-hour IV infusion every 4 weeks at 7.5 mg/kg. The primary endpoint of the study is to assess the rate of RBC-TI lasting ≥8 weeks. Secondary endpoints include safety, rate of RBC-TI ≥24 weeks, time to RBC-TI start, RBC-TI duration, rate of HI-E, the amount and relative change in RBC transfusions, rate of CR or PR, overall survival, progression of MDS, pharmacokinetics and effect of treatment on quality of life. Biomarkers relevant to the mechanism of action of imetelstat will be assessed to demonstrate target inhibition and their association with clinical responses. Cytogenetics and mutation analyses will be performed to evaluate the impact of imetelstat on reduction/depletion of malignant clones leading to disease modification. Disclosures Platzbecker: Novartis: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria. Steensma:Astex: Consultancy; Arrowhead: Equity Ownership; Summer Road: Consultancy; Onconova: Consultancy; Aprea: Research Funding; Pfizer: Consultancy; Stemline: Consultancy; H3 Biosciences: Other: Research funding to institution, not investigator.. Santini:Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Johnson & Johnson: Honoraria; Acceleron: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; Menarini: Membership on an entity's Board of Directors or advisory committees. Germing:Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Jazz Pharmaceuticals: Honoraria; Amgen: Honoraria. Font:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pfizer: Membership on an entity's Board of Directors or advisory committees. Díez-Campelo:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Patnaik:Stem Line Pharmaceuticals.: Membership on an entity's Board of Directors or advisory committees. Sherman:Geron Corporation: Employment, Equity Ownership. Dougherty:Geron Corporation: Employment, Equity Ownership. Feller:Geron Corporation: Employment. Sun:Geron Corporation: Employment, Equity Ownership. Wan:Geron Corporation: Employment, Equity Ownership. Huang:Geron Corporation: Employment, Equity Ownership. Rizo:Geron Corporation: Employment, Equity Ownership. Fenaux:Celgene Corporation: Honoraria, Research Funding; Aprea: Research Funding; Astex: Honoraria, Research Funding; Jazz: Honoraria, Research Funding.

Abstract BACKGROUND: Patients with TD lower-risk (LR)-MDS relapsed or refractory to ESA have limited treatment options. Imetelstat is a first-in-class telomerase inhibitor that targets cells with short telomere lengths and active telomerase, characteristics observed in some MDS patients. IMerge is an ongoing global study of imetelstat in RBC TD patients with LR-MDS (IPSS Low or Int-1). In the first 32 patients enrolled, 8-week TI rate was 34%, with 24-week TI of 16%, and HI-E of 59%. The most frequently reported adverse events were reversible grade ≥3 cytopenias (Fenaux et al EHA 2018 Abstr S1157). Higher response rates were observed in patients (n=13) who were LEN and HMA naïve without del(5q). We report here results in an additional 25 LEN and HMA naïve patients without del(5q), with longer term follow-up of the 13 initial patients meeting the same criteria. METHODS: IMerge is a phase 2/3 trial (NCT02598661) that includes LR-MDS patients with a high transfusion burden (≥4 units / 8 weeks) who are relapsed/refractory to ESA or have sEPO >500 mU/mL. The additional 25 were required to be LEN and HMA naïve and lack del(5q). Imetelstat 7.5 mg/kg was administered IV every 4 weeks. In addition to the key endpoints noted above, secondary endpoints include safety, time to and duration of TI. Biomarkers are also being explored, including telomerase activity, hTERT, telomere length, and genetic mutations. RESULTS: Overall, for the 38 LEN/HMA naïve and non-del(5q) patients, median age was 71.5 years and 66% were men. 63% of patients were IPSS Low and 37% Int-1. Median prior RBC transfusion burden was 8.0 (range 4-14) U, and 71% had WHO 2008 RARS or RCMD-RS. 9/37 (24%) patients with evaluable sEPO levels had baseline level >500 mU/mL. As of July 2018, with a median follow-up of 25.8 months for the initial 13 patients, and 5.2 months for the 25 recently included patients, the 8-week RBC-TI rate was 37% (14/38). Durability of 24-week TI responses was demonstrated, with a median duration of 10 months and the longest ongoing response now >2 years. Among the patients achieving durable TI, all showed a Hb rise of ≥3.0 g/dL compared to baseline during the transfusion-free interval. Response rates were similar in RARS/RCMD-RS (33% [9/27]) and other patients (27% [3/11]), and those with baseline EPO levels >500 mU/mL (33% [3/9]) and ≤500 mU/mL (32% [9/28]). Reversible grade ≥3 neutropenia and thrombocytopenia were each reported in 58% of the patients. Liver function test (LFT) elevations were mostly grade 1/2. Reversible grade 3 LFTelevations were observed in 3 (8%) patients on study. An independent Hepatic Review Committee deemed the observed LFT elevations were not imetelstat-related hepatic toxicities. SUMMARY / CONCLUSIONS: In this cohort of 38 non-del(5q) LR-MDS patients with a high RBC transfusion burden who were ESA relapsed/refractory and naïve to LEN/HMA, single-agent imetelstat yielded a TI rate of 37%, with a median duration of 10 months and limited side effects. Durable responses were characterized by transfusion independence >24 weeks and accompanied by Hb rise. Updated data will be presented. Disclosures Steensma: Takeda: Consultancy; Syros: Research Funding; Otsuka: Membership on an entity's Board of Directors or advisory committees; Onconova: Consultancy; Novartis: Membership on an entity's Board of Directors or advisory committees; Kura: Research Funding; Janssen: Consultancy, Research Funding; H3 Biosciences: Research Funding; Celgene: Research Funding; Amphivena: Membership on an entity's Board of Directors or advisory committees; Acceleron: Consultancy. Platzbecker:Celgene: Research Funding. Van Eygen:Janssen: Consultancy, Research Funding; Roche: Research Funding; Amgen: Research Funding. Raza:Kura Oncology: Research Funding; Onconova: Research Funding, Speakers Bureau; Celgene: Research Funding; Novartis: Speakers Bureau; Geoptix: Speakers Bureau; Janssen: Research Funding; Syros: Research Funding. Santini:Amgen: Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria; AbbVie: Membership on an entity's Board of Directors or advisory committees; Otsuka: Consultancy; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Research Funding. Germing:Celgene: Honoraria, Research Funding; Janssen: Honoraria; Novartis: Honoraria, Research Funding. Font:Celgene: Membership on an entity's Board of Directors or advisory committees. Samarina:Janssen: Research Funding. Díez-Campelo:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Bussolari:Janssen: Employment, Equity Ownership. Sherman:Janssen: Employment, Equity Ownership. Sun:Janssen: Employment, Equity Ownership. Varsos:Janssen: Employment, Equity Ownership. Rose:Janssen: Employment, Equity Ownership. Fenaux:Roche: Honoraria; Otsuka: Honoraria, Research Funding; Jazz: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Celgene: Honoraria, Research Funding.

Abstract Background. Gene mutation profiling is increasingly employed for diagnosis, risk stratification, and clinical management in patients with MDS. However, current World Health Organization MDS classification is still based on histologic findings (with the exception of SF3B1 for MDS-RS), and guidelines generally suggest that clinical decisions be guided by clinico-pathologic risk stratification tools such as Revised International Prognostic Scoring System (IPSS-R). We sought to study beliefs and patterns of practice with respect to gene mutation profiling among health care providers who manage patients with MDS. Methods. A link to a 23-question web-based survey was emailed to members of the Eastern Cooperative Oncology Group (ECOG)-ACRIN Cancer Research Group, Alliance for Clinical Trials in Oncology (Alliance), and the Southwest Oncology Group (SWOG), and the Cancer Trials Support Unit (CTSU) on 5/1/2018 with 6 subsequent weekly reminders. The Qualtrics survey platform was used to record anonymous responses. We used descriptive statistics to analyze the data. No incentive was provided for responses. Results. Of 371 received responses, 262 were received from providers who did not manage MDS patients or lacked analyzable data and therefore were excluded. Of 109 eligible responses, 108 responders were from institutions representing 31 US states (one respondent was from South America). Median age of respondents was 48 years (range, 33-75); 43 (39%) were women. A third of responders (32%) worked at a university hospital, while 25%, 17%, and 5% worked at a community hospital, private practice, or other settings, respectively. While 37% of participants worked at institutions with guidelines for clinical care of MDS patients, 28% reported that their institutional guidelines recommended MDS-specific gene mutation profiling. Such testing was performed at institutions of 13% participants; institutions of 26% of responders tested a general AML panel that included MDS-specific genes. The total number of respondents whose institutions sent out either an MDS-specific gene panel or a general AML gene panel with MDS-specific genes was similar, 25% and 12%, respectively (Fig. 1). Of those who routinely perform molecular testing, 94% do so at diagnosis, 56% at relapse, 33% during preparation for stem cell transplant, 31% after the failure of hypomethylating agents (HMA), 24% during screening for a clinical trial, and 15% at initial treatment (Fig. 2). MDS gene mutation profiling was felt to be most helpful in diagnosis (rarely 11%; sometimes 49%; often 30%; always 9%), risk stratification (sometimes 31%; often 51%; always 15%), and prognosis (sometimes 31%; often 51%; always 14%); its role was more limited in response assessment (never 12%; rarely 25%; sometimes 44%; often 14%) and to predict responses to HMAs (never 5%; rarely 28%; sometimes 52%, often 14%) (Fig. 3). Various types of evidence were used to stratify MDS risk and prognosis: genetic mutations were used by nearly everyone (95%); 70% relied on morphologic findings, while gene expression/transcriptome profiling was used by 40%. Eighty-four percent of responders reported relying on conventional prognostic models like IPSS-R to identify high-risk patients for whom they would consider intensive treatment options. For this purpose, 62% would also rely on mutation profiling, and 32% would also consider higher frequency of gene mutations. While mutations in the p53 pathway were felt to be helpful in terms of risk stratification and treatment decisions by 70% of responders, 43%, 39%, 31%, 26% 23%, 20%, and 3% considered mutations in spliceosome, DNA methylation, transcription factors, histone modification, signaling, RAS pathway, and cohesin genes, respectively, to be useful as well. Approximately 31% of responders were not certain as to which mutations would affect risk stratification and management choices and said they needed to review literature. The respondents also cited multiple limitations to wider clinical use of MDS gene mutation profiling (Fig. 4). Conclusions. Our survey demonstrates widespread use of gene mutation profiling in the management of patients with MDS, but also reveals substantial variability in beliefs, practices, testing logistics, and interpretation of molecular profiling. Our findings emphasize the need for high-quality data to develop consensus evidence-based guidelines for gene profiling of MDS patients. Disclosures Sekeres: Opsona: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Opsona: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Bejar:AbbVie/Genentech: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; Foundation Medicine: Consultancy; Astex/Otsuka: Consultancy, Honoraria; Modus Outcomes: Consultancy; Takeda: Research Funding; Genoptix: Consultancy. Gore:Celgene: Consultancy, Research Funding. Zeidan:Ariad: Consultancy, Speakers Bureau; Gilead: Consultancy; Incyte: Employment; Celgene: Consultancy; Abbvie: Consultancy; Agios: Consultancy; Novartis: Consultancy; Pfizer: Consultancy.

Abstract Background: The prognostic significance of lymphocyte counts and immune status has been carefully examined in lymphoid malignancies, but the importance of the lymphocyte count in chronic myeloid neoplasms is less clear. In a recent analysis of MDS cases associated with deletion of chromosome 5q (Holtan SG et al AmJHem 2008 Epub 12Jun), we observed that an ALC >1.2 × 109 cells/L at diagnosis is independently associated with improved survival. The prognostic value of ALC in MDS not associated with del(5q) is unknown. Methods: We reviewed the medical records of patients without del(5q) diagnosed with MDS at our institution over a 10-year period and gathered data on complete blood counts and leukocyte differentials, bone marrow findings, and clinical course. Inclusion criteria included diagnosis within 6 months prior to initial consultation at our institution and <20% marrow blasts. Patients were classified according to the International Prognostic Scoring System (IPSS) and the WHO-classification based Prognostic Scoring System (WPSS). Results: The median age of the 503 included patients (360 M, 143 F) was 69 years (range 20–91). Median follow-up was 14 months, and 65% of patients were known to have died with an overall median survival of 36 months. Cytogenetic results as classified by the IPSS were favorable in 326 (65%) patients, intermediate in 112 (22%), and poor in 65 (13%). Both IPSS and WPSS accurately stratified patients, but the WPSS was better at identifying the lowest and highest risk patients. Survival by IPSS risk group was as follows: low-risk disease (n=95, median survival 41.8 months), intermediate-1 (n=285, 23.6 months), 106 with intermediate-2 (n=106, 14.1 months), and high-risk (n=17, 8.05 months). WPSS risk groups included very low risk (n=87; median survival 71.9 months), low risk (n=149, 28.8 months), intermediate risk (n=85, 19.3 months), high risk (n=143, 14.4 months), and very high risk (n=39, 8.8 months). In univariate analysis, factors associated with poorer survival included advanced age (p = 0.0012), higher-risk WHO subtype (p<0.0001), increased marrow blast percentage (p<0.0001), poor-risk karyotype (p<0.0001), higher IPSS score or WPSS score (p<0.0001), lower hemoglobin (p<0.0001), lower MCV (p=0.03), lower ALC (p=0.001), and lower platelets (p=0.001). Factors not associated with survival included sex and ANC. In a multivariate model including only baseline CBC parameters, hemoglobin >10 g/dL (p < 0.001), MCV >96 fl (p = 0.0493), ALC >1.2 × 109/L (p = 0.0449), and platelet count >100 × 109/L (p = 0.0046) were associated with improved survival. A high baseline ALC also maintained independent prognostic significance in a multivariate model against the IPSS (RR 0.746, 95% CI: 0.598, 0.933, p = 0.0099), and the raw WPSS score (RR 0.791, 95% CI 0.633, 0.987, p=0.037) but not the WPSS group (p=0.0794). There was no significant difference in the distribution of IPSS scores between the ALC >1.2 × 109 cells/L and the ALC ≤ 1.2 × 109 cells/L groups, although there were significantly more WPSS high risk patients in the low baseline ALC group (p = 0.0163). The creation of an ALC-modified IPSS score by adding 0.5 point for an ALC ≤ 1.2 × 109 cells/L resulted in a significant increase in median overall survival of the low risk group (41.8 months versus 66.1 months, p < 0.001, Figure 1). Conclusion: ALC is a novel and easily obtained prognostic marker in MDS that provides information complementary to existing prognostic scoring systems. Figure 1. Kaplan-Meier curves based upon IPSS (a) and the ALC-modified IPSS (b), where 0.5 point was added for an ALC ≤ 1.2 × 109 cells/L. Figure 1. Kaplan-Meier curves based upon IPSS (a) and the ALC-modified IPSS (b), where 0.5 point was added for an ALC ≤ 1.2 × 109 cells/L.