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Abstract Background Fedratinib (SAR302503) is a JAK2-selective inhibitor that has provided clinically meaningful reductions in MF-associated splenomegaly and symptoms in Phase I and II studies (J Clin Oncol 2011;29:789. Haematologica 2013;98:S1113). Here, we present efficacy and safety data from the Phase III JAKARTA study of fedratinib versus placebo in patients with MF (NCT01437787). Methods In this international double-blind, placebo-controlled, 3-arm study, patients aged ≥18 years with IPSS intermediate-2 or high-risk MF, platelet count ≥50 × 109/L, and splenomegaly were randomized (1:1:1) to receive placebo or fedratinib 400 mg or 500 mg, orally, once daily, in consecutive 4-week cycles. Patients who received placebo were eligible to cross-over to fedratinib (randomized 1:1 to 400 mg or 500 mg) following 6 cycles of treatment, or prior to Cycle 6 if the patient had disease progression. The primary endpoint was spleen response rate (RR) (≥35% reduction in spleen volume from baseline measured by MRI or CT at Week 24, and confirmed 4 weeks later). Secondary endpoints included symptom RR (≥50% reduction in total symptom score from baseline at Week 24, measured through a daily electronic eDiary using the modified Myelofibrosis Symptom Assessment Form [Cancer 2011;117:4869. Blood 2011;118:401]), and safety of fedratinib. Results A total of 289 patients were randomized: median age 65 years; 59% male; 63% primary MF; 48% high-risk MF; 67% JAK2V617F positive; 16% platelet count <100 × 109/L; median baseline spleen volume 2568 mL (range 316–8244); median baseline total symptom score 14.7 (0–57). Median (range) exposures for placebo, 400 mg and 500 mg groups were 24 (2–34), 30 (1–55) and 28 (1–60) weeks, respectively. Spleen RRs at Week 24 (placebo 1%; 400 mg 47%; 500 mg 49%), and confirmed at Week 28 (placebo 1%; 400 mg 36%; 500 mg 40%), were significantly (p<0.0001) higher in both fedratinib groups compared with placebo (Table). Nineteen patients had a spleen response at Week 24 not confirmed 4 weeks later (spleen reduction 25–35% [n=10]; image not available/evaluable [n=8]; image taken outside time window [n=1]). Spleen RRs by baseline platelet level are shown in the table. Patients treated with fedratinib had significantly (p<0.0001) greater improvements in MF symptoms compared with placebo (Table). The most common all grade non-hematologic treatment-emergent adverse event (TEAE) was diarrhea (16%, 66% and 56% of patients in the placebo, 400 mg and 500 mg groups, respectively). Grade 3/4 diarrhea was reported in 5% of patients in both the 400 mg and 500 mg dose groups. The most common hematologic TEAE was anemia (any grade 91%, 99% and 98%; Grade 3/4 25%, 43% and 60% in the placebo, 400 mg and 500 mg groups, respectively). Rates of Grade 3/4 thrombocytopenia were 9% (placebo), 17% (400 mg), and 27% (500 mg). Incidences of Grade 3/4 liver function tests (placebo/400 mg/500 mg) were: bilirubin, 2%/2%/1%; ALT, 0%/3%/3%; and AST, 1%/2%/2%. Overall treatment discontinuation rates up to 24 weeks of treatment were 25% (placebo), 22% (400 mg) and 32% (500 mg). Twenty-five patients died during the study (10, 5 and 10 in the placebo, 400 mg and 500 mg groups, respectively); the most common causes of death: disease progression (placebo [n=5]; 400 mg [n=3]; 500 mg [n=4]) and adverse events (placebo [n=4]; 400 mg [n=1]; 500 mg [n=4]). Conclusions In this Phase III, randomized, placebo-controlled, 3-arm study of 289 MF patients, treatment with fedratinib 400 mg or 500 mg once-daily demonstrated clinically meaningful and statistically significant reductions in splenic volume and MF-associated symptom burden versus placebo. Fedratinib had an acceptable safety profile, with the adverse events reported consistent with those observed in previous studies. This study was sponsored by Sanofi. Disclosures: Pardanani: Sanofi, Bristol Myers Squibb, PharmaMar and JW Pharma: Clinical trial support Other. Harrison:Novartis: Research Funding; Novartis, Sanofi, YM Bioscience, Celgene, SBio, Gilead: Honoraria; Novartis, Sanofi, Shire: Speakers Bureau; Novartis, Sanofi, YM Bioscience, SBio, Gilead: Membership on an entity’s Board of Directors or advisory committees. Cortes:Incyte, Sanofi: Consultancy; Incyte, Sanofi: Research Funding. Cervantes:Novartis: Speakers Bureau; Novartis and Sanofi: Membership on an entity’s Board of Directors or advisory committees. Mesa:Incyte, Genentech, Lilly, MS Pharma, Gilead: Research Funding. Jourdan:Sanofi: Honoraria. Vannucchi:Novartis: Membership on an entity’s Board of Directors or advisory committees. Drummond:Sanofi, Novartis, Celgene: Honoraria; TargeGen, Novartis: Speakers Bureau; Sanofi, Novartis, Celgene: Consultancy. Passamonti:Novartis, Celgene, Incyte, Sanofi, Roche: Honoraria. Neumann:Sanofi: Employment. Gao:Sanofi: Employment.

Abstract Abstract 3838 Background: SAR302503 (SAR503, formerly TG101348), a potent, oral JAK2-selective inhibitor was studied in a Phase I/II trial for the treatment of patients with high- or intermediate-risk primary, post-polycythemia vera (PV) and post-essential thrombocythemia (ET) myelofibrosis (MF). SAR503 was administered orally once daily in 28-day cycles. Eligibility criteria included platelet count of ≥50 × 109/L. Interim safety and efficacy data from this study up to April 2010 have been previously published (JCO 2011, 29(7):789–796). The aim of this presentation is to report updated safety and efficacy of ongoing patients as well as an analysis of the JAK2V617F allele burden in this cohort. Results: Overall, 59 subjects (median age 64 years) were treated. Forty four patients had PMF, 12 post-PV MF and 3 post-ET MF; 86% were JAK2 V617F-positive. Median palpable spleen size was 18 cm at study enrollment. Twenty eight patients were treated in the dose-escalation cohort (30–800 mg administered as a single daily dose); thirty one patients were treated at the MTD (680 mg) in the dose confirmation cohort. 43/59 patients (73%) completed 6 cycles of treatment and continued treatment on the extension study. Currently, 22 patients (37%) remain on treatment with a median number of 28.5 cycles (24–41 range) and a median of last dose of 440 mg/day. Safety: Treatment-emergent toxicities in cycle 1–6 have been previously reported; toxicities were dose-dependent and generally alleviated with dose-reduction. Five patients discontinued treatment beyond cycle 6 for treatment-related adverse events: thrombocytopenia, depression, mental status changes, creatinine elevation and subdural hematoma. For the subgroup of patients with a baseline platelet count between 50–100 × 109/L (n =13; median 73, range 51–94); the platelet count at defined times points during follow up was: cycle 3; median 50, range 21–138 (p=0.09) and cycle 6; median 47, range 13–85 (p=0.01). Despite 7 of the 13 patients being treated at ≥680 mg/day, only 2 instances of Grade 4 thrombocytopenia were noted in this group Spleen response: As previously reported, spleen responses were seen early, usually within first 3 cycles, with half or more patients in each dose level ≥240 mg/day showing a durable ≥50% decrease in palpable spleen size. Spleen size (mean, median, range, and proportion with ≥50% reduction) at the following time points was: Baseline (n=58; 18.33cm, 18cm, 4–38cm, NA) ; 6 months (n=57; 9.05cm, 9cm, 0–30cm, 54.4%;) 12 months (n=42; 8.55cm, 9cm, 0–28cm, 66.7%) 18 months (n=36; 8.03cm, 8.5cm, 0–33cm, 52.8%); 24 months (n=31; 8.10cm, 8cm, 0–30cm, 54.8%,) 30 months (n=18; 6cm, 7.5cm, 0–16cm, 61.1%,and) 36 months (n=9; 5.89cm, 3cm, 0–16cm, 66.7%). JAK2V617F allele burden: We previously reported a significant decrease in JAK2V617F allele burden at the end of cycles 6 and 12. A durable decrease was also demonstrable after 24 cycles of treatment (n =21; median 9%, range 0–100%) relative to baseline (n =51; median 20%, range 3–100%) (p=0.03). Similarly, for patients with JAK2 V617F allele burden >20% at baseline; there was a significant decrease after cycle 24 (n =12; median 21%, range 6–100%) relative to baseline (n =23; median 60%, range 23–100%) (p=0.03). Conclusions: SAR503 is safe and efficacious treatment with long term effect on spleen size and JAK2V617F allele burden in patients with high- and intermediate-risk myelofibrosis. Additional follow up information will be updated at the time of meeting. Disclosures: Jamieson: Wintherix: Equity Ownership; Pfizer Oncology: Research Funding; Celgene: Research Funding; Novartis: Honoraria. Gao:Sanofi-Aventis: Employment. Zhang:Sanofi-Aventis: Employment. Neumann:Sanofi-Aventis: Employment.

Abstract Abstract 3949 Acute kidney injury (AKI) is a common but serious sequela of multiple myeloma. Recently, the International Myeloma Working Group (IMWG) introduced a new renal response criteria with complete (CRenal), partial (PRenal) and minimal (MRenal) responses. This study compares the IMWG criteria with other models to determine their correlation with overall survival (OS). Patients with multiple myeloma and AKI were identified from centers around the world. OS was calculated from the day of AKI. Renal function was assessed by estimated glomerular filtration rate (eGFR) via MDRD method. Hematologic response was the best achieved as assessed by International Uniform Response Criteria for Multiple Myeloma. Only patients with peak serum creatinine (Scr) ≥ 2.0 mg/dl were included. Separate analyses were performed on the newly diagnosed (ND) versus previously treated (PT) patients. A total of 158 patients were collected from centers in United States, United Kingdom, France and Austria. Fourteen patients were excluded for having peak Scr < 2.0 mg/dl and one for repeated episodes of AKI. Median age of the 143 patients was 64 (34 – 87) years, 58.7% were male and 115 were newly diagnosed. Median Scr was 5.1 (2.0 to 18.6) mg/dl and median eGFR was 10.6 (2.8 – 36.5) ml/min/1.72 m2. Dialysis was required in 49.3%, and 72.9% were dialysis independent at the end of the study. By IMWG criteria, median OS ranged between 6.0 months (m) in PT patients with no renal response (NRenal) to 23.7m in patients with CRenal, p = 0.34 (Table 1). In ND patients, OS was 31.4m in NRenal vs 73.8m in CRenal (p = 0.08). However, OS was similar between PRenal and CRenal, p = 0.70 (Figure 1). If only patients with a hematologic PR or better were analyzed, the OS range was 6.0m in NRenal to 23.7m in CRenal in PT patients (p = 0.85) and 36.6m in NRenal to 73.8m in CRenal in ND patients, p = 0.73.Table 1.Previously TreatedNMedian SurvivalNMedian Survival (>PR) CRenal323.7 m323.7 m PRenal413.1 m312.8 m MRenal512.0 m119.2 m NRenal166.0 m56.0 m p-value0.340.85Newly Diagnosed CRenal2273.8 m2273.8 m PRenal27Not Reached23Not Reached MRenal2265.6 m1965.6 m NRenal4331.4 m2136.6 m p-value0.080.73Figure 1.Overall survival (OS) of 115 patients evaluated by the IMWG renal response criteria. OS was not significantly different by Log-Rank test between patients with CRenal and NRenal, p = 0.08.Figure 1. Overall survival (OS) of 115 patients evaluated by the IMWG renal response criteria. OS was not significantly different by Log-Rank test between patients with CRenal and NRenal, p = 0.08. The best model tested was one that defined renal response (RR) as regaining or maintaining dialysis independence and no response (NR) as dialysis dependence. RR was associated with a superior survival for both PT patients (13.5 m vs 6.0m (NR), p = 0.03) and ND patients (73.8m vs 20.1m (NR), p < 0.001). RR increased with the depth of hematologic response, p = 0.04. RR occurred in 75% of the PT patients with hematologic PR or better and 66.7% in those with less than PR, p = 0.64. In ND patients, RR occurred in 85.7% of those with PR or better and 54.6% of those with PR or less, p = 0.003. This may explain the differences in OS when hematologic response was considered. In PT patients with hematologic PR or better, renal response did not improve OS (21m vs 6m, p = 0.28) but it remained beneficial in the ND patients (73.8m vs 35.1m, p = 0.04, Figure 2). Renal response was not significantly associated with OS for any patient with hematologic response that was VGPR or better. In a multivariate analysis, RR (p = 0.001), ND (p <0.001) and PR or better hematologic response (p = 0.046) were associated with OS.Figure 2.In a separate model, 83 newly diagnosed patients with hematologic response of PR or better were evaluated. Patients who were dialysis independent achieved a renal response (RR) and those who remained on dialysis had no response (NR). Patients with RR had a superior overall survival than patients with NR. Renal response was independent of a hematologic response of PR or better.Figure 2. In a separate model, 83 newly diagnosed patients with hematologic response of PR or better were evaluated. Patients who were dialysis independent achieved a renal response (RR) and those who remained on dialysis had no response (NR). Patients with RR had a superior overall survival than patients with NR. Renal response was independent of a hematologic response of PR or better. The results of our study suggest renal response is important to OS but the depth of response was not as important. Renal response was most important when the hematologic response was less than a VGPR. This supports renal response as part of the overall response assessment in multiple myeloma patients. Based on our results, reducing the number of response categories and simplifying the current consensus criteria seems justified. Median survival of the 143 patients evaluated by the IMWG renal response criteria. Overall survival was calculated by Kaplan Meier method. Differences in survival were evaluated by Log-Rank test. Disclosures: Ludwig: Mundipharma, Janssen-Cilag: Research Funding, Speakers Bureau. Hutchison:The Binding Site: Honoraria.

Abstract Abstract 1570 B-cell non-Hodgkin lymphoma encompasses a heterogeneous group of B-lymphocyte-derived malignancies that are characterized by chromosomal translocations involving the immunoglobulin (IG) gene loci and specific histological subtypes of disease are associated with a different spectrum of IG translocations. Marginal zone derived B cell lymphomas encompass three distinct entities: extranodal marginal zone B lymphoma (MZL) of mucosa associated lymphoid tissue (MALT), nodal MZL (NMZL), and splenic MZL (SMZL). MALT lymphoma is genetically unique and four mutually exclusive chromosomal translocations have been identified in this disease thus far. However, the known translocations are only present in a subset of cases suggesting that additional uncharacterized translocations or other genetic events may exist that contribute to disease development. In previous studies we characterized the novel t(X;14)(p11.4;q32) translocation in a patient with MALT lymphoma and found that GPR34, an orphan G-protein coupled receptor (GPCR), was highly expressed due to its juxtaposition to the IGHSA2 switch region. We then measured GPR34 mRNA expression in tissue biopsies from a panel of MALT, NMZL, SMZL, lymphoplasmacytic (LPL), diffuse large B cell (DLBCL), follicular (FL), and mantle cell (MCL) lymphomas. Expression of GPR34 was detected in all tissues examined, but was significantly increased in MALT (37 fold), LPL (23 fold), NMZL (18 fold), and SMZL (21 fold) compared to normal CD19+ B cells. GPR34 mRNA expression was also analyzed by gene expression profiling (GEP) of a panel of lymphomas or control lymphoid tissue and we confirmed elevated expression of GPR34 in the t(X;14) case and detected elevated GPR34 mRNA expression in MALT, LPL, NMZL, SMZL, and ABC DLBCL. When we grouped specimens by high and low expression of GPR34, a clear molecular subtype of SMZL could be identified and suggests that GPR34 high expressing tumors have a unique GEP. To confirm the qPCR and GEP analysis of GPR34 expression, we analyzed surface expression of GPR34 by flow cytometry of normal and malignant tissues and found that expression of GPR34 was detected on all MALT and SMZL B cells with an average DMFI of 2.08 (DMFI range 1.26–3.18, n=12) and on the JeKo-1 lymphoma B cell line (DMFI= 4.75). Analysis of CD19+ cells from normal controls (n=3) revealed a low level of GPR34 on (average DMFI =1.12). Little is known about the function of GPR34 and to further characterize the impact of GPR34 overexpression on cell signaling, OCI-LY19 lymphoma B cells and HeLa cells were transduced with GPR34 or a vector control. To determine if MAPK activity, a pathway regulated by GPCRs, was upregulated, the phosphorylation status of ERK1/2 in GPR34 or control cells was analyzed and we found that ERK1/2 was constitutively phosphorylated at significantly higher levels in GRP34 expressing cells. To further explore which signaling pathways were affected by GPR34 overexpression, GPR34 or vector control cells were transfected with an AP-1, CRE, NF-kB, E2F, SRE, NFAT, or ISRE- luciferase reporter plasmid and GPR34 expressing cells had significantly increased luciferase activity driven by AP-1 (5.35-fold), CRE (4.7-fold), NF-kB (2.6-fold), and E2F (2.1) when compared to vector control cells. To determine the biologic impact of GRP34 overexpression, the proliferation rates of vector control and GPR34 cells were compared and we found that proliferation of GPR34 WT cells was significantly higher than that seen in the control. We next tested the effect of the MEK inhibitor on proliferation and saw a dose dependent decrease in proliferation of GPR34 expressing cells. We then tested the ability of GPR34 cells to generate colony formation in a soft-agar colony formation assay. After 3 weeks of culture, the GPR34 cells had formed significantly more colonies than the vector control suggesting that overexpression of GPR34 can result in increased anchorage-independent cell growth. Taken together, our results identify a novel translocation in MALT lymphoma, emphasize a novel role for GPR34 in regulation of gene expression and tumor cell growth, and suggest that MEK inhibitors may be useful in a subset of translocation–harboring or GRP34 high-expressing tumors. Disclosures: No relevant conflicts of interest to declare.

Abstract The deficiency in the conversion of prothrombin to thrombin which develops after administration of dicumarol appears to be due largely to decreased cothromboplastin activity. Both the development of this deficiency and the recovery from it tend to precede the accompanying changes in prothrombin itself, as measured by the two-stage method. In terms of deviation from normal, the deficiency in conversion often exceeds in magnitude the deficiency of prothrombin itself.

Abstract Background Myelofibrosis (MF) is a clonal myeloproliferative neoplasm (MPN) associated with a high degree of symptomatology, progressive cytopenias and potential to transform into acute myelogenous leukemia (AML). Thrombocytopenia amongst MF patients is a proven negative prognostic indicator and predictor of transformation to AML. Ruxolitinib is an effective JAK inhibitor for MF symptoms and splenomegaly, but is not indicated in patients with severe thrombocytopenia. Phase III trials of pacritinib have shown alleviation of the MF symptom burden amongst patients with thrombocytopenia (ASCO 2015 Mesa et. al.). In this study, we assessed the symptom burden of MF patients with significant thrombocytopenia who were naïve to pacritinib. Methods Data was assessed from a prospectively collected international database of MF patients in which demographics, disease features, and MF symptoms utilizing the myeloproliferative neoplasm symptom assessment form (MPN-SAF; Scherber et al, 2011). The MPN-SAF includes the patient's perceptions of common MPN-related symptoms and overall quality of life (QOL) on a 0 (absent) to 10 (worst imaginable) scale. Total symptom score (TSS) was computed based on symptom items using the published scoring algorithm on a 0 (all reported symptoms absent) to 100 (all reported symptoms worst imaginable) scale. MF risk scores were calculated using the DIPSS criteria (Gangat, 2011). Thrombocytopenia was defined as a platelet count <100 x 10(9)/L, anemia was defined as hemoglobin<10 g/dL and leukopenia was defined as a white blood cell count <4.0 x 10(9)/L. Associations between the MPN-SAF individual symptoms were investigated using Pearson correlations. Results Demographic and Disease Features: A total of 418 patients with (n=89) and without (n=329) thrombocytopenia completed the MPN-SAF. Patients with thrombocytopenia were slightly younger (57.4 vs. 61.0, p=0.01) with longer disease durations (11.9 years vs. 8.8 years, p=0.0489) and had a higher prevalence of primary myelofibrosis (PMF; 82% vs. 66%, p=0.01). The presence of thrombocytopenia was associated with other laboratory abnormalities including anemia (60.7% vs. 25.3%, p<0.001) and leukopenia (34.8% vs. 52.3%, p<0.001), along with the need for red blood cell transfusions (34.8% vs. 14.6%, p<0.001). Patient cohorts did not differ by gender, DIPSS risk score, history of prior thrombosis or hemorrhage. In comparing patients with severe thrombocytopenia (<50 x 10(9)/L, n=43) to those with moderate thrombocytopenia (51-100 x 10(9)/L, n=46), severe thrombocytopenia patients were more likely to have anemia (74.4% vs. 47.8%, p=0.01) and require red blood cell transfusions (51.2% vs. 19.6%, p=0.002). Symptoms Scores for individual MPN-SAF items were assessed for each subgroup. Patients with thrombocytopenia had markedly higher total symptom scores than patients without thrombocytopenia (32.8 vs. 24.1, p<0.001). Individual scores were also higher for most items (fatigue, early satiety, inactivity, dizziness, sad mood, sexuality, cough, night sweats, itching, fever, weight loss, overall QOL)[Figure 1]. No significant differences in MPN SAF TSS or individual symptom scores were observed in comparing severe vs. moderate thrombocytopenia patients. Discussion MF patients with thrombocytopenia have distinctive clinical characteristics and face a significantly more severe symptom burden. Importantly, despite thrombocytopenia being a recognized risk factor for disease advancement, no correlations are noted between patient symptomatology and risk category. In addition, patients with severe thrombocytopenia do not differ symptomatically from patients with moderate thrombocytopenia despite having more severe anemia, leukopenia and transfusion requirements. This implies that the degree of symptomatology expressed by thrombocytopenic MF patients occurs independent from the exact platelet value. Conclusion The results of this study suggest that patients with thrombocytopenia will benefit from aggressive symptomatic control, potentially from targeted agents. Figure 1. MF Symptoms in Patients With and Without Thrombocytopenia Figure 1. MF Symptoms in Patients With and Without Thrombocytopenia Disclosures Kiladjian: Novartis: Consultancy; Novartis: Other: Travel grant; Research Funding paid to institution (Hôpital Saint-Louis et Université Paris Diderot); Incyte Corporation: Consultancy. Zweegman:Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding. Harrison:Shire: Speakers Bureau; CTI Biopharma: Consultancy, Honoraria, Speakers Bureau; Sanofi: Honoraria, Speakers Bureau; Gilead: Honoraria; Novartis: Honoraria, Research Funding, Speakers Bureau. Cervantes:Novartis: Consultancy, Speakers Bureau; Sanofi-Aventis: Consultancy; CTI-Baxter: Consultancy, Speakers Bureau. Barbui:Novartis: Speakers Bureau. Etienne:ARIAD: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Other: Congress Travel/Accomodations, Research Funding, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau. Roy:BMS: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Vannucchi:Shire: Speakers Bureau; Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees. Mesa:Novartis. Research- incyte, Gilead, cti, Genentech, promedior, NS Pharma: Consultancy.

Abstract Background: The Philadelphia chromosome negative myeloproliferative neoplasms (MPNs), including essential thrombocythemia (ET), polycythemia vera (PV) and myelofibrosis (MF) all have a time dependent risk of progression to either an advanced myelofibrotic state (post ET/PV MF) and/or to acute myeloid leukemia. The impact of disease duration upon the MPN symptom burden is not well understood, nor are the precise mechanisms of disease progression. We sought to better understand the impact of disease duration on MPN symptom burden. Methods: Symptom burden data was collected utilizing the Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF) amongst MPN patients, collected at the time of an office visit in an international cohort of MPN patients as previously described (Scherber et. al.). Symptom burden assessment was a previously validated 27-item symptom burden questionnaire scored on a 0-10 scale (0= as good as it can be, 10 = as bad as it could be). The patient or provider was asked to report the time since MPN diagnosis. MPN duration was determined to be early if the diagnosis was established between 0 to 5 years ago, intermediate if the diagnosis was established between 6 to 10 years ago, and late if the diagnosis was established 11 years ago or more. Anemia was defined as a red blood cell count less than 10 g/dL, leukopenia was defined as a white blood cell count was below 4 x 109, and thrombocytopenia if the platelet count was below 150 x109. Statistical significance was calculated using ANOVA f-test and chi squared. Results: Patient demographics and disease burden: A total of 1443 patients responded to the survey, including 592 (41%) ET, 549 (38%) PV, and 302 (21%) MF patients, including 181 (60%) primary MF, 67 (22%) post-ET MF, and 54 (18%) post-PV MF. Among MF patients, mean duration of MPN diagnosis was 9 years, and mean duration MF diagnosis was 4.7 years. Among respondents, 757 fit criteria for early disease duration, 353 fit criteria for intermediate disease duration, and 333 fit criteria for late disease duration. Respondent mean age was 62 years and approximately half of respondents were female (55%). Patients with longer diagnosis duration tended to be older (p=0.009) and were most likely to have anemia (0.02), leukopenia (p=0.01), or thrombocytopenia (p=0.03). These individuals were also most likely to have a history of hemorrhage (p=0.007) or require red blood cell transfusions (p<0.001). Combined cohort symptom burden: On average among the combined cohort of ET, PV and MF patients, symptoms tended to worsen with time with this effect being significant for symptom items of fatigue (BFI, p<0.04), concentration (p=0.007), insomnia (p=0.02), sexual difficulties (p=0.002), cough (p=0.03), night sweats (p=0.002), and pruritus (p=0.02). Symptoms of early satiety (p=0.004), concentration difficulties (p=0.01), insomnia (p=0.03), sexual difficulties (p=0.02), cough (p=0.01), and night sweats (p=<0.001) had significantly higher prevalence in those with longer disease duration. Similarly, the total calculated MPN-10 score (p=0.008) and quality of life assessment (0.03) demonstrated worsened outcomes with time (Table 1). No significant differences in symptoms for the combined cohort were observed among individuals diagnosed 0 to 1 years ago compared to those with a diagnosis established between 2 and 5 years ago. Symptom burden in MPN subtypes. When evaluating specific MPN types, patients with essential thrombocythemia experienced significantly greater sexual difficulties over time (p=0.03). The severity (p=0.01) and incidence (p=0.03) of pruritus and incidence of night sweats (p<0.001) were significantly increased over time for individuals with PV. For those with MF, the severity (p= 0.01) and incidence (p=0.009) of cough also significantly increased with longer diagnosis duration. Discussion Overall, significant worsening in symptom burden can be recognized over time for individuals diagnosed with MPNs. Diagnosis may not necessarily correlate with disease duration as the timing of diagnosis may be delayed from onset of disease. Given the intent of this abstract to evaluate changes with disease duration, we did not investigate correlations between symptom burden and cytopenias. We do know that risk factors for survival in the MPNs include older age and thrombosis, however, disease duration should be investigated as an alternative marker of burden in future survival studies. Disclosures Harrison: CTI Biopharma: Consultancy, Honoraria, Speakers Bureau; Shire: Speakers Bureau; Gilead: Honoraria; Novartis: Honoraria, Research Funding, Speakers Bureau; Sanofi: Honoraria, Speakers Bureau. Kiladjian:Incyte Corporation: Consultancy; Novartis: Other: Travel grant; Research Funding paid to institution (Hôpital Saint-Louis et Université Paris Diderot); Novartis: Consultancy. Zweegman:Celgene: Research Funding; Janssen: Research Funding; Takeda: Research Funding. Barbui:Novartis: Speakers Bureau. Etienne:Novartis: Consultancy, Honoraria, Other: Congress Travel/Accomodations, Research Funding, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; ARIAD: Consultancy, Honoraria, Speakers Bureau. te Boekhorst:CTI Biopharma: Consultancy; Novartis: Consultancy. Vannucchi:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Other: Research Funding paid to institution (University of Florence), Research Funding; Shire: Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees. Mesa:Novartis. Research- incyte, Gilead, cti, Genentech, promedior, NS Pharma: Consultancy.

Abstract Introduction The Classic Myeloproliferative Neoplasms (MPNs), characterised by an over production of one or more cells of the myeloid lineage, are classified into polycythaemia vera (PV), essential thrombocythaemia (ET) and primary myelofibrosis (PMF). Despite the identification of numerous genetic mutations, a paucity of information relating to medical and lifestyle factors contributing to the aetiology of these diseases remains. Methods The MOSAICC Study was an exploratory case-control study of MPNs. MPN patients were recruited between two sites, Belfast and Southampton, in preparation for a planned UK-wide investigation. Population controls (identified by General Practitioners) and non-blood relative/friend controls were also recruited. Participants completed a telephone-based questionnaire seeking information on a range of medical, environmental, lifestyle and occupational risk factors. Risk factors were assessed using unconditional logistic regression with adjustment for potential confounders. Results Risk factors identified included smoking [≥25 pack years vs. never: odds ratio (OR) 3.14, 95% confidence interval (CI) 1.26-7.87], increasing childhood household density [>2 vs <1 Child(ren)/room: OR 3.29, 95% CI 1.31-8.30], history of heart disease (OR 3.31, 95% CI 1.23-8.87), CT scans (≥3 vs. none: OR 4.92, 95% CI 1.55-15.67), having an implant (OR 10.77, 95% CI 1.01-3.10), and pig ownership (OR 5.92, 95% CI 1.17-29.92). Alcohol was associated with a reduced risk of MPNs (OR 0.49, 95% CI 0.28-0.88) as was home working on car exhausts (OR 0.33, 95% CI 0.12-0.88), painting at home (OR 0.49, 95% CI 0.28-0.86) and short haul air travel (p for trend 0.012). Participants working in occupations with high exposure to environmental tobacco smoke had an excess risk of MPN (OR 2.45, 95% CI 1.12-5.37). Work-based radiation and solvent exposure also appeared to increase risk of MPNs (p<0.05). Conclusions This exploratory study has confirmed a reported association between cigarette smoking and MPNs. It has identified some potential novel risk factors including work-based radiation and solvent exposure. The findings of this study need to be replicated in a larger, adequately powered, study in order to identify important risk factors for the classic MPNs. Conflict of Interest The authors declare no conflict of interest. Acknowledgments: The MOSAICC Study team acknowledges the support of the National Institute for Health Research, through the Northern Ireland Cancer Research Network (NICRN) and for Southampton the Central South Coast Cancer Network (CSCCN). The team thank those who have participated in the MOSAICC study and the personnel who assisted in the recruitment of patients. Disclosures Mesa: CTI Biopharma: Research Funding; Promedior: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; Incyte Corporation: Research Funding; Pfizer: Research Funding; NS Pharma: Research Funding; Genentech: Research Funding; Gilead: Research Funding.

Abstract Abstract 2688 Members of the signal transducers and activators of transcription (STAT) family of proteins function as secondary messengers mediating cellular responses to various cytokines. Aberrant activation of STAT5 protein has been implicated in the pathogenesis of hematologic malignancies due to the ability of these transcription factors to regulate genes involved in cellular proliferation and survival. The two highly homologous transcription factors collectively known as STAT5, namely STAT5A and STAT5B, display both redundant and distinct physiologic functions in non-malignant B cells. Yet, despite evidence suggesting independent functions for STAT5A and STAT5B in the pathophysiology of solid tumors, the precise roles of these isoforms in hematologic malignancies such as Waldenstrom's macroglobulinemia (WM) are not known. Initial immunohistochemical staining of WM bone marrow biopsies (n=6) revealed higher levels of STAT5 phosphorylation compared to bone marrows from normal controls (n=6). Additionally, phosphorylated STAT5 was highly expressed in CD19/CD138+ sorted cells obtained from the bone marrow of patients with WM (average ΔMFI compared to isotype control, 4.64 +/− 1.7, n=6) as determined by FACS analysis. Furthermore, western blotting demonstrated baseline STAT5 phosphorylation in both WM and IgM-secreting cell lines (MWCL-1 and BCWM-1, respectfully). The expression of other phosphorylated STAT proteins (1, 3, 4, and 6) was not detected. To better understand the overall role of STAT5 biologically in WM, MWCL-1 and BCWM.1 cells were treated with a specific inhibitor of STAT5, N′-((4-Oxo-4H-chromen-3-yl)methylene) nicotinohydrazide. Following 72 hours in culture, this inhibitor significantly decreased IgM secretion at lower doses when compared to controls (10 μM, MWCL-1: 9413 +/− 511 ng/mL vs. 6166 +/− 160 ng/mL, p<0.001; BCWM.1: 13,380 +/− 393 ng/mL +/− 10970 +/− 240 ng/mL, p<0.001) and nearly abolished IgM secretion at higher doses. Significant effects on proliferation and viability were also observed, but only at higher concentrations of drug where the specificity toward STAT5 may have diminished. To characterize the roles of the individual STAT5 isoforms in WM, we have developed doxycycline-inducible STAT5A-shRNA and STAT5B-shRNA and used these to create stable knockdowns in the MWCL-1 cell line. Addition of doxycycline to these cell lines for 72h nearly abolishes STAT5A or STAT5B protein expression, respectively, without affecting expression of the other isoform, while no change in STAT5 expression is detected in cells transduced with the empty vector (EV) control. The functional effects of isoform-specific STAT5 inhibition on WM tumor biology were assessed through proliferation assays and ELISA to determine the utility of therapeutically targeting a single STAT5 isoform. No difference in proliferation was observed in the STAT5A- or STAT5B-shRNA cells following 72h induction with doxycycline as compared to the EV control cells. However, specific knockdown of STAT5A following doxycycline induction significantly decreased IgM secretion as compared to the EV control (EV, 91.8 +/− 10.2% of baseline secretion, STAT5A, 66.7 +/− 15.1% of baseline, p<0.05), whereas IgM secretion was decreased by knockdown of STAT5B but not significantly. Similarly, IL-6 secretion was only diminished in cells lacking STAT5A as compared to EV cells (EV, 94 +/− 14.16% of baseline secretion; STAT5A, 64% +/− 7.6% of baseline, p<0.001). Overall these initial data indicate a role for isoform-specific STAT5 activation in the maintenance of WM tumors, and future studies will further our understanding of the specific roles of STAT5A and STAT5B in WM tumors. Disclosures: Ansell: Seattle Genetics, Inc.: Research Funding.

Abstract Abstract 2699 Myeloid differentiation factor 88 (MYD88) is an adaptor protein that plays a key role in mediating innate immune response. Upon activation of toll-like (TLRs) or IL-1b receptors, MYD88 activates a signaling cascade that culminates in activation of NF-kB and expression of proinflammatory genes. Activating mutations in MYD88 have been reported in non-Hodgkin's lymphoma (NHL) tumors, including diffuse large B cell and marginal zones lymphoma. The most common MYD88 mutation described thus far is a single base pair mismatch resulting in an amino acid switch from lysine to proline at position 265 (MYD88L265P). MYD88L265P functions as a constitutively active MYD88 protein resulting in dysregulated NF-kB and STAT3 signaling. This mutation has recently been reported to be present in lymphomoplasmacytic lymphoma/Waldenstrom macroglobulinemia (LPL/WM) at a high frequency, ∼ 90% (Xu et al, ASH, #261, 2011). The discovery of MYD88L265P in a high percentage of LPL/WM tumors, and other subtypes of NHL, provides the basis for the identification and targeting of MYD88 dependent pathways. Additionally, the ability of this mutation to drive NF-kB-mediated cytokine expression combined with our finding that LPL/WM patients have elevated serum cytokines suggests that the MYD88 mutation may play a significant role in LPL/WM pathogenesis. We first wanted to confirm the incidence of the MYD88L265P mutation in LPL/WM and other subtypes of indolent lymphoma. Using Sanger sequencing we found that 57% (n=58) of LPL, 4% of MALT (n=23), 5% of nodal marginal zone (n=34), and 6% of splenic marginal zone (n=34) lymphomas harbor the MYD88L265P mutation, with all but 1 case being heterozygous. When we specifically looked at the LPL cases with WM, we found that 70% of WM tumors have the MYD88L265P mutation. In a validation cohort of WM (n=41), we found a similar mutation rate of 68%. Additionally, the WM cell line MWCL1 and the IgM secreting cell line BCWM.1 also harbor the MYD88L265P mutation. The prevalence of the MYD88L265P mutation in NHL, specifically WM and LPL, suggests that it may be a novel driver of lymphoma pathogenesis and a potential therapeutic target. However, it is not yet clear if this mutation correlates with activation of signaling pathways, or cell growth and survival in LPL/WM. To address these questions we first explored the possibility that the MYD88 signaling pathway is constitutively active in cells that express MYD88L265P. Upon activation of TLRs or IL-1b receptors, MYD88 forms a homodiamer and recruits IRAK1/4 and TRAF6 into a complex resulting in association and phosphorylation of TAK1 followed by activation of NF-kB. Using three cell lines that express MYD88L265P (BCWM, MWCL1, and OCI-Ly3), we looked for complex formation of MYD88, IRAK1/4, TRAF6, and TAK1. Immunoprecipitation of either endogenous IRAK1 or TAK1 revealed constitutive association with both TRAF6 and MYD88. We also detected phosphorylation of TAK1, and taken together, these data suggest that the MYD88 pathway is activated in cells that harbor the MYD88L265P mutation. We next wanted to confirm the significance of the MYD88 pathway on lymphoma cell growth. Using our cell lines we tested the effect of IRAK1/4, TAK1, and NF-kB inhibitors on cell proliferation. All MYD88L265P expressing cell lines were sensitive to the TAK1 and NF-kB inhibitors in a dose dependent manner (0–10 uM), however, we only saw inhibition of cell proliferation with the IRAK1/4 inhibitor at the highest dose (10 uM) in the BCWM cell line. These data suggest that cell proliferation is dependent on the MYD88 signaling pathway, with some variation being detected between cell line models and inhibitors. Because the MYD88 pathway has also been shown to drive cytokine secretion we next tested the impact of the IRAK1/4, TAK1, and NF-kB inhibitors on expression of IL-10. Using drug doses that were shown to inhibit cell proliferation, but not impact survival, we found that all three inhibitors reduced the level of IL-10 secreted by each of cell lines. In summary, our data confirm the high incidence on the MYD88L265P mutation in LPL/WM, we find that the MYD88 signaling pathway is constitutively activated in cells the harbor the mutation, and we show that cell proliferation and cytokine secretion are dependent on MYD88 signaling targets. These studies highlight the biologic significance of the MYD88L265P mutation in LPL/WM and suggest that the MYD88 signaling pathway may be a novel therapeutic target. Disclosures: No relevant conflicts of interest to declare.