Vannucchi, Alessandro M.

Abstract Abstract 4105 Background: JAK2 mutations are found in approximately 99% of patients with polycythemia vera (PV) and 60% of those with essential thrombocythemia (ET) or primary myelofibrosis (PMF). It is currently assumed that other mutations relevant to JAK signaling contribute to the pathogenesis of JAK2 mutation-negative myeloproliferative neoplasms (MPN). The same might hold true for some cases of “idiopathic erythrocytosis” associated with subnormal serum erythropoietin level (sEpo). LNK is a plasma membrane-bound adaptor protein whose function includes inhibition of wild-type and mutant JAK2 phosphorylation. LNK exon 2 mutations were recently described in two patients with JAK2V617F-negative ET or PMF. Both mutations involved the LNK pleckstrin homology (PH) domain; one was a 5 base-pair deletion and missense mutation leading to a premature stop codon (603_607delGCGCT; 613C>G) and the other a missense mutation (622G>C; glutamic acid to glutamine substitution; E208Q). Objectives: i) To estimate the prevalence of LNK mutations in chronic and blast phase MPN ii) To determine if LNK mutations are mutually exclusive of other MPN-associated mutations iii) To test the hypothesis that LNK mutations might contribute to the pathogenesis of JAK2 mutation-negative PV or otherwise unexplained erythrocytosis Methods: LNK mutation analysis was performed on bone marrow or blood cells using modified primers for amplifying the SH2 and PH domains, using previously published methods (Oh et al. Blood First Edition Paper, prepublished online April 19, 2010; DOI 10.1182/blood-2010-02-270108). Results: LNK mutation studies were performed in 172 patients; paired chronic-blast phase samples were analyzed in 26 cases. Diagnoses in the 172 study patients were as follows: 78 chronic-phase MPN (39 JAK2V617F-positive PV, 25 PMF and 14 ET) enriched for TET2, IDH, JAK2V617F, or MPL mutations, 61 blast-phase MPN (41 blast-phase PMF, 11 blast-phase PV and 9 blast-phase ET), 25 JAK2V617F-negative PV and 8 “unexplained erythrocytosis” associated with subnormal sEpo and negative for Epo receptor (EPOR) mutations. Ten novel heterozygous LNK mutations, all but one affecting exon 2 in the PH domain, were identified: 6 missense mutations involving codons 215, 220, 223, 229 and 234, one nonsense mutation involving codon 208 (622G>T leading to glutamic acid to a stop codon substitution; E208X), one synonymous mutation involving codon 208, and 2 deletion mutations involving exon 2 (685-691_delGGCCCCG) or exon 5 (955_delA). LNK mutations were most frequent in blast-phase MPN, occurring in 6 (9.8%) of the 61 informative patients; chronic-phase sample analysis in 4 of these revealed the same mutation in only one case. Mutant LNK was detected in chronic-phase samples only in 2 additional patients with blast-phase MPN. Among the 8 LNK-mutated blast-phase MPN cases, 7 had blast-phase PMF. The clinical phenotype in the remaining 2 LNK-mutated patients was that of an isolated erythrocytosis without overt features of PV. JAK2V617F was documented in 3 and IDHR140Q in 1 LNK-mutated patients. Conclusions: LNK mutations i) target an exon 2 ‘hot spot' in the PH domain spanning residues E208-D234, ii) might be most prevalent in blast-phase PMF iii) are not mutually exclusive of JAK2 or IDH mutations and iv) might be part of the “missing link” in the pathogenesis of JAK2 mutation-negative “idiopathic” erythrocytosis. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 5060 Background: The Myeloproliferative Neoplasm Symptom Assessment Form (MPN-SAF) is a concise instrument of patient reported outcomes (PRO) designed to assess the unique spectrum of symptoms present in the majority of patients (Mesa et. al. Cancer 2007). We sought to validate the Italian Translation of the MPN-SAF which addresses 19 separate symptoms reported by MPN patients. Methods: Translation: We utilized the standard practice of PRO translation in which 3 independent translations are created by 3 independent translators fluent in both languages. A fourth translator then discussed the translations with the other translators and a consensus translation was obtained. Validation: Patients self completed the MPN-SAF: Italian at the time of a physician office visit and the Italian EORTC-QLQ-C30 (a widely used instrument of PRO for cancer patients) was co-administered for validation purposes. Results: Patients and Symptomatic Burden: 186 patients were prospectively enrolled (ET (N=88; 47%), PV (N=69; 37%) and MF (N=29; 16%)) a median of 6 years (range:0-29) from their diagnosis. Patients were of a median age (62; range 29–91 years) and gender (56% females) typical of the disease. 72% (N=135) had received some form of non-aspirin medical therapy for their disease, and 68% were on therapy at the time of completing the questionnaire. Patients frequently had a history of either thrombotic events (31%) and/or hemorrhagic events (13%). The MPN-SAF measured 19 items in the enrolled patients (data summarized in Table 1). Validation Analysis: EORTC-QLQ-C30: Consistent with our experience with the MPN-SAF:English, Pearson correlations between MPN-SAF:Italian individual symptom scores and the Italian EORTC-QLQ C30 showed excellent correlations with co-validation questions including fatigue, pain, insomnia, (all p<0.001). Excellent correlations were demonstrated between EORTC-QLQ-C30 subscales and corresponding MPN-SAF measurements. Comparison with MPN-SAF:English: Comparison with 102 patients prospectively completing the MPN-SAF: English (ET=20, PV=23, MF=59) in the USA indicated very strong correlations (when controlling for MPN subtype) in the prevalence of all 19 items assessed and only subtle differences in terms of symptomatic severity for fatigue, itching and insomnia. Conclusions: The MPN-SAF:Italian is an easy to administer, clear, 19-item inventory of patient-reported outcomes that is specific to MPNs. Additionally, the instrument is validated by 1) comparison to previously validated Italian instruments and 2) the correlation with the MPN-SAF:English. Utilization of the instrument in Italian MPN clinical trials will allow for useful comparison to patients completing the MPN-SAF in other countries and will serve as a valuable clinical marker of disease symptom severity. Disclosures: Vannucchi: Novartis: Membership on an entity's Board of Directors or advisory committees. Mesa:SBio: Research Funding; Novartis: Research Funding; Celgene: Research Funding; Incyte: Research Funding; Roche: Research Funding; eisai: Research Funding; telik: Research Funding.

Abstract Abstract 457 Introduction- The 2008 World Health Organization (WHO) diagnostic criteria for myeloproliferative neoplasms (MPN) underscore the role of bone marrow (BM) morphology in distinguishing essential thrombocythemia (ET) from early, and at times prefibrotic, primary myelofibrosis (PMF) that clinically presents like ET. The value of such a distinction in predicting clinical outcome has been questioned by some investigators. Study Design- Clinician scientists and hematopathologists from seven international centers of excellence for ET convened to design a clinicopathologic database of patients locally diagnosed and treated as ET. Study eligibility criteria included availability of treatment-naïve BM specimens obtained within one year of diagnosis. All bone marrows subsequently underwent a central blinded re-review by the author of the pertinent WHO chapter (JT) who applied strict WHO guidelines to identify cases of early PMF that were spuriously diagnosed as ET. Results- Revision of the BM biopsies according to the WHO morphological criteria confirmed ET in 891 patients (81%). Diagnosis was revised to early, prefibrotic PMF in 180 patients (16%). The remaining 33 (3%) BM specimens were qualitatively inadequate for accurate classification or represented unclassified cases. i) At presentation, early PMF, as opposed to true ET, was characterized by higher leukocyte (p<0.0001) and platelet (p=0.002) counts, lower hemoglobin (p=0.01) and hematocrit (p=0.001) levels, higher serum lactate dehydrogenase level (p<0.0001), higher circulating CD34+ cell count (p=0.03) and higher rate of palpable splenomegaly. JAK2V617F mutational frequency was 60% in each of the two groups. ii) Median follow-up was 6.2 years for ET and 7.0 years for early PMF. During this period, the rates of arterial (1.2-1.4% patients/year) and venous (0.6 patients/year) thrombotic complications were similar in the two groups. However, patients with early PMF, as compared to those with ET, were more likely to develop overt myelofibrosis (1% vs. 0.5% patients/year; RR=2.0, p=0.04) or acute leukemia (0.6% vs. 0.1% patients/year; RR=5.2, p=0.001). Cumulative leukemic transformation rate at 10 and 15 years was 0.7% and 2.1% in true ET versus 5.8% and 11.7% in PMF Similarly, survival was significantly worse in patients with early PMF (mortality rate: 2.7% vs. 1.3% patients/year; RR=2.1, p=0.002).The 10 and 15-years overall survival rates were: 89% and 80% in true ET versus 76% and 59% in PMF. On multivariable analysis, other risk factors for poor survival were age > 60 years (HR=6.3, p<0.0001), a leukocyte count of > 11×109/L (HR=2.13, p<0.0001) and history of thrombosis (HR=3.0, p<0.0001). Conclusions- The current study validates the clinical relevance of strict adherence to WHO criteria in the diagnosis of ET and provides seminal information on the survival and risk of leukemic transformation in strictly WHO-defined ET, which appears to be substantially better than previously assumed. Disclosures: No relevant conflicts of interest to declare.

Abstract Abstract 4095 Background: Symptomatic burden in myeloproliferative neoplasms (MPNs) is present in over 70% of MPN patients (Mesa et. al. Cancer 2007). We sought to validate a broadly applicable instrument (MPN-SAF) to assess symptoms in myelofibrosis (MF), essential thrombocythemia (ET) and polycythemia vera (PV). Methods: Using the previously validated MF-SAF as a base instrument, we added several key additional symptoms previously identified as present in all subtypes of MPNs including headaches, concentration, dizziness, extremity tingling, insomnia, sexual problems and mood changes on a 0 (absent) to 10 (worst-imaginable) scale. Validation: The MPN-SAF was administered jointly with the EORTC-QLQ-C30 as the co-validation instrument using prospective cohorts in the USA, Sweden and Italy. The translated MPN-SAF (Swedish and Italian) was created through a standard approach using teams of 4 translators working in concert. Results: Compiled MPN-SAF: Patient data: 402 MPN-SAF surveys were administered (English (25%), Italian (46%) and Swedish (28%)) in 161 ET patients (40%), 145 PV patients (36%), and 96 MF patients (24%), an average of 7.8 years (range 0 – 43 years) from their MPN diagnosis. Participants were of typical age (64.9, range 26 – 91 years) and gender (53% female) characteristic of disease. Prior hemorrhage (10%) and thrombosis (25%) were frequent. 68% of patients currently received cytoreductive therapy and 84% received cytoreductive therapy in the past. Patients and Symptomatic Burden: 19 items assessed in the MPN-SAF demonstrated consistently that the most common symptoms were fatigue (93%), decreased quality of life (84%), insomnia (65%), sad mood (65%), and sexuality problems (58%). The least common symptoms (<50% prevalence) were fevers (20%), weight loss (35%), abdominal pain (46%), cough (46%), headache (48%), and bone pain (49%). Symptoms were most severe in MF, followed by PV, then ET patients. Although symptoms are present in all 3 MPN subgroups, itching is notably more burdensome in PV patients (65%, median score of 2.8 out of 10). Additionally, abdominal pain, abdominal discomfort, early satiety and inactivity all are most prevalent and severe in MF. Interestingly, night sweats (present in 56%) overall had similar prevalence and severity across all 3 MPNs. The majority found the MPN-SAF easy to understand (98%) and “addressed most of my MPN symptoms” (96%). Comparison to EORTC-QLQ-C30: Strong correlations existed between individual items represented on both the MPN-SAF and the EORTC-QLQC30 including pain, fatigue, appetite and insomnia (all p<0.001). Additionally key symptomatic elements were highly correlated with the EORTC QLQ-C30 functional subscales. Comparison to Physician Perceptions: Comparison of the results of the MPN-SAF to enrolling physicians' blinded opinion of patients symptoms (6 assessed - night sweats, fevers, fatigue, weight loss, bone pain, and pruritus) showed excellent correlation with corresponding patients' responses except bone pain (all p<0.001). Comparison across Countries: When controlling for MPN subtype, responses between the three different countries (and 3 different languages the MPN-SAF was administered) demonstrated great consistency and correlation for all but 1 item, bone pain. Serial MPN-SAF Results: 51 patients in the USA (ET (17.6%), PV (25.5%), and MF (56.9%)), responded to a repeat MPN-SAF survey sent via US mail (50% response rate, mean time between surveys 190±63 days (range 43 – 257)). Pearson correlations indicate that most MPN-SAF items are well correlated (r >0.5, p<.001) upon repeat survey administration. Items characteristic of advanced disease, including weight loss, fever, and cough displayed lower Pearson correlations (r=0.46, -0.08, and 0.38 respectively). Intra-class correlations for test-retest reliability indicated that common features of disease, including mean BFI, inactivity, insomnia, and night sweats, were highly reproducible upon serial survey administration (ICC>0.7, 2, k model used). Conclusion: The MPN-SAF is comprehensive and reliable instrument which is available in multiple languages to evaluate MPN-associated symptoms. The MPN-SAF is recommended as a uniform symptom assessment tool for MPN patients participating in clinical trials globally. Disclosures: Vannucchi: Novartis: Consultancy. Samuelsson:Roche Sweden:. Harrison:Incyte: Honoraria; Novartis: Honoraria. Mesa:SBio: Research Funding; Novartis: Research Funding; Celgene: Research Funding; Incyte: Research Funding; Roche: Research Funding; eisai: Research Funding; telik: Research Funding.

Abstract Background and purpose of the study: Several reports have documented that histone deacetylase inhibitors induce neoplastic cells to undergo growth arrest, differentiation and/or apoptotic cell death. Among these agents, Givinostat inhibits proliferation of cells bearing the JAK2V617F mutation and has shown clinical significant activity with good tolerability in patients with chronic myeloproliferative neoplasms, including polycythemia vera (PV). In two phase II studies [Rambaldi et al. Br J Haematol 2010;150:446, Finazzi et al. Br J Haematol 2013;161:688] the maximum administered dose (150 mg/day) was generally well tolerated. Assuming a linear relationship between dose and efficacy, greater clinical efficacy could be expected with increased doses of Givinostat. Methods: This is a two-part, multicenter, open label, non-randomized, phase Ib/II study to assess the safety and tolerability, maximum tolerated dose (MTD) and preliminary efficacy of Givinostat in patients with JAK2V617F positive PV. Part A (i.e. phase Ib) is the dose escalation portion of the study, while Part B assesses the preliminary clinical efficacy of Givinostat at the MTD defined in Part A. Eligible patients for this study include JAK2V617F positive PV patients, who have active and/or uncontrolled disease, defined as: (i) Hematocrit (HCT) ≥ 45% or HCT <45% normalized by phlebotomy, and (ii) PLT > 400 x109/L, and (iii) WBC > 10 x109/L. Study therapy is administered in 28 day cycles (cycle is defined as 4 weeks of treatment). Disease response has been evaluated according to the clinico-haematological European LeukemiaNet (ELN) criteria [Barosi et al. Blood 2009;113:4829] at Cycles 3 and 6. Disease-related symptoms have been reported directly by the patients who completed the MPN-SAF QoL form. The study lasts up to a maximum of 24 weeks of treatment. However, after completion of the trial, all patients achieving clinical benefit are allowed to continue treatment with Givinostat in a long-term study (ClinicalTrials.gov ID: NCT01761968). In Part A, the Cycle 1 has been used to define the MTD of Givinostat. Only dose limiting toxicities (DLTs) experienced during Cycle 1 were considered for dose escalation decisions. Part B is the cohort expansion part of the study to assess the preliminary clinical efficacy of Givinostat at the MTD in evaluable patients Results: In Part A, 12 patients with active and/or uncontrolled disease, were treated with Givinostat, 6 patients at DL1 (100 mg b.i.d.), 3 patient at DL6 (150 mg/die) and 3 patients at DL0 (50 mg b.i.d.). Only one DLT .(grade 3 dyspepsia) was observed in the 6 patients treated at DL1 during the Cycle 1. Givinostat treatment was generally well tolerated: one patient developed grade 4 and two patients grade 3 thrombocytopenias at DL1 after the Cycle 1. Complete/partial response was observed in 100% of evaluable patients at Cycle 3 (Figure). At that time, an important reduction of WBC and PLT count (about 50% in both cases), an HCT control without phlebotomy, a net decrease of MPN-SAF total score and JAK2V617F allele burden (about 50% and 30%, respectively) have been noted and generally maintained at Cycle 6. One out of 3 (33%) patients with splenomegaly at baseline normalized the spleen at Cycle 6. PK/PD evaluations are currently under analysis. Part B started on December 2015 and is currently recruiting patients. At the time of ASH Meeting, a presentation of the preliminary results of the interim analysis (IA) is planned. The objective of this IA is to evaluate the response rate of the first 12 treated and evaluable patients. Conclusions: Taking into account the continuous schedule of the drug as prescribed in this current study, the daily dosage of 200 mg has been identified as the MTD of Givinostat in PV patients. Givinostat treatment is generally well tolerated and shows preliminary clinical efficacy in PV patients with an active/uncontrolled disease. Response rate of patients in Part A C3D28 = Cycle 3 Day 28, or three months of treatment. C6D28 = Cycle 6 Day 28, or six months of treatment. Two patients dropped-out the study Part A, due to Informed Consent Form withdrawal, while 1 patient left the study for AE (i.e. grade 3 dyspepsia, DLT). At C3D28, 1 Complete Response (CR) and 8 Partial Response (PR) have been observed. At C6D28, 1 Complete Response (CR), 7 Partial Response (PR) and 1 No Response (NR) have been observed Figure Figure. Disclosures McMullin: Novartis: Honoraria, Speakers Bureau. Vannucchi:Novartis: Honoraria, Speakers Bureau. Mesa:Ariad: Consultancy; CTI: Research Funding; Galena: Consultancy; Celgene: Research Funding; Promedior: Research Funding; Novartis: Consultancy; Incyte Corporation: Research Funding; Gilead: Research Funding. Tibes:Italfarmaco S.p.A.: Consultancy, Honoraria. Bettica:Italfarmaco S.p.A.: Employment. DI Tollo:Italfarmaco S.p.A.: Employment.

Abstract Background : In primary myelofibrosis (PMF), ̴ 88% of patients harbor JAK2, CALR or MPL, with respective mutational frequencies of approximately 60%, 22% and 6%; ̴ 12% are wild type for all three driver mutations and are labelled as being "triple negative" (Blood. 2014;124:2507). It is now well-established that CALR-mutated patients with PMF display significantly better survival, compared to all the other mutational categories; in addition, preliminary data have suggested inferior survival for "triple-negative" cases (Leukemia. 2014;28:1472; Blood. 2014;124:1062) and the possibility that the favorable impact of CALR mutations might be restricted to CALR type 1 or type 1-like variants (Blood. 2014;124:2465). In the current study, we sought to clarify the prognostic impact of driver mutations, and CALR variants, on overall (OS) and leukemia-free (LFS) survival, in a two-center study involving 1118 patients. Methods: A total of 1118 patients with PMF from the Mayo Clinic (n =722) and University of Florence, Italy (n =396) were included in the current study. Study patients were selected based on availability of mutation information. PMF diagnosis was according to World Health Organization criteria (Blood. 2009;114:937). Previously published methods were used for CALR, JAK2 and MPL mutation analyses and determination of CALR variants (Blood. 2014;124:2465). Kaplan-Meier survival analysis was considered from the date of first referral for the Mayo cohort and date of diagnosis for the Florence cohort. Leukemic transformation events replaced death as the uncensored variable during LFS analysis and Cox proportional hazard regression model was used for multivariable analysis. Results : Analysis was first conducted on the Mayo cohort of 722 patients (median age 64 years; 64% males). DIPSS-plus risk distributions were 14% low, 17% intermediate-1, 37% intermediate-2 and 33% high. All patients were annotated for JAK2/CALR/MPL mutations as well as CALR variants; 477 harbored JAK2, 139 CALR and 41 MPL mutations; 65 patients were triple-negative. The 139 CALR -mutated patients included type 1/type 1-like (n =115) and type 2/type 2-like (n =24). At a median follow-up time of 3.1 years, 439 (61%) deaths and 63 (8.7%) blast transformations were documented. In univariate analysis, survival in patients with CALR type 1/type 1-like mutations was significantly longer than every other mutational category: HR (95% CI) were for triple-negative 2.7 (1.8-4.0), JAK2 2.7 (2.0-3.7), CALR type 2/type 2-like 2.3 (1.3-4.2) and MPL 1.9 (1.1-3.1) (Figure 1); these differences were sustained during multivariable analysis that included ASXL1 mutations (n =480) and DIPSS-plus, and were also apparent in the Florence cohort of 396 cases that included 251 JAK2, 53 CALR type 1/type 1-like, 21 CALR type 2/type 2-like, 50 triple-negative and 21 MPL mutated cases (Figure 2). There was no difference in survival among the Mayo cohort across mutational categories not including CALR type 1/type 1-like variants (p=0.33). Because specific driver mutations in PMF differentially cluster with age and sex, multivariable analysis including these two parameters was also performed and confirmed the significant survival advantage of CALR type 1/type 1-like over triple-negative, JAK2 and CALR type 2/type 2-like mutated cases. Based on the above information, we divided driver mutational categories into "type 1/type 1-like" (median survival 10.3 years) and "all other mutational categories" (median survival 3.9 years; p<0.01). The difference in survival between these two groups remained significant (HR 2.1, 95% CI 1.5-2.9) during multivariable analysis that included both DIPSS-plus (P<0.01) and ASXL1 mutation (HR 1.8, 95% CI 1.4-2.2). LFS was similar between these two groups (p=0.4) but it was inferior in triple-negative cases compared to CALR type 1/type 1-like variants (HR 2.8, 95% CI 1.3-6.2), MPL (HR 4.6; 95% CI 1.04-20.4) and JAK2 (HR 2.5, 95% CI 1.3-4.8) but not CALR type 2/type 2-like variants (p=0.56). There was no difference in LFS among mutational categories not including triple-negative cases (p=0.33). Conclusions : In PMF, driver mutations might be classified into two prognostically distinct categories: "favorable" (type 1/type 1-like) and "unfavorable" (all other mutational categories). In addition, triple-negative cases might be at a higher risk of leukemic transformation. Disclosures Pardanani: Stemline: Research Funding. Vannucchi: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; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Abstract Introduction: Myelofibrosis (MF) is a life-threatening hematologic malignancy characterized by splenomegaly and debilitating symptoms including fatigue, abdominal pain, night sweats, bone pain, pruritus, and unintentional weight loss. The myeloproliferative neoplasm symptom assessment form (MPN-SAF) is a PRO tool designed to measure MF-related symptom burden and was developed and validated at Mayo Clinic. It was modified (MPN-SAF total symptom score [TSS] and TSS 2.0) for use in the PERSIST-1 and PERSIST-2 phase 3 trials. For PERSIST-1, when examining the 6 common symptoms in both TSS versions (tiredness, night sweats, early satiety, itchiness, bone pain, and abdominal pain), pacritinib-treated patients (pts) had significant improvements in TSS overall and in individual symptoms vs BAT; Pt Global Impression of Change (PGIC) was also significantly improved for pts receiving pacritinib. Improvements in EORTC-QLQ-C30 scales were noted in the pacritinib arm (Mesa, EHA 2015). The proportion of pts achieving spleen volume reduction (SVR) ≥35% at Week 24 was significantly greater with pacritinib vs BAT (ITT: 19.1% vs 4.7%, p=0.0003; evaluable at baseline and Week 24: 25.0% vs 5.9%; p=0.0001). This analysis examines relationships between TSS improvement and changes in splenomegaly and HRQoL outcomes. Methods: Pts who received no prior JAK inhibitor therapy were randomized 2:1 to oral pacritinib 400 mg once daily or BAT. Pts were stratified by DIPSS risk (Int-1/Int-2 vs High) and platelet count (<50,000/μL vs 50,000/μL to <100,000/μL vs ≥100,000/μL). Pts must have had a baseline total TSS ≥13 using MPN-SAF TSS 2.0. Each symptom is rated on a scale from 0 (absent) to 10 (worst imaginable) using MPN-SAF TSS and TSS 2.0. Results for the 6 symptoms common to both TSS versions are reported. Additional PROs used for assessment of HRQoL included EORTC QLQ-C30 and EQ-5D-5L. In multivariate logistic regressions, odds of TSS reduction ≥50% at Week 24 were modeled as a function of Week 24 SVR ≥35%, spleen length reduction (SLR) ≥ 50%, PGIC, improvement in each EORTC scale, and improvement in EQ-5D-5L Overall Health State (OHS) and in each dimension individually while adjusting for treatment (pacritinib vs BAT). Correlations were examined in all pts and by baseline platelet counts (<50,000/μL, <100,000/μL, and ≥100,000/μL). Results: A total of 327 pts were enrolled (PAC: 220, BAT: 107). 62% of pts had primary MF, 32% had baseline platelets <100,000/μL, and 16% had baseline platelets <50,000/μL. TSS reduction ≥50% was found to be associated with SVR ≥35% and improvement in splenomegaly (SLR ≥50%). In the total pt population, there was a significant association between TSS reduction and SVR (odds ratio [OR]=2.60, p=0.016). In all pts, there was a significant association between TSS reduction and improvements in OHS as measured by EQ-5D-5L (OR=2.30, p=0.013). TSS reductions were also marginally associated with improvements in the QLQ-C30 Global Health Scale (GHS)/QoL Scale (OR=1.92, p=0.050) and, though not statistically significant, there was a trend of improvement in perceived overall health as measured by PGIC (OR=2.16, p=0.118). TSS reductions were further examined in pts grouped by baseline platelet count. Improvement in EQ-5D-5L OHS was marginally associated with TSS reductions in pts with platelets <50,000/μL (OR=6.03, p=0.057). For pts with platelets <100,000/μL, reductions in TSS were significantly associated with reductions in splenomegaly (SLR ≥50%; OR=9.53, p=0.004), and improvements in the QLQ-C30 GHS/QoL domain (OR=4.03, p=0.022) as well as the EQ-5D-5L OHS (OR=5.49, p=0.008). A significant association between TSS reductions and SVR ≥35% was observed in pts with platelets ≥100,000/μL (OR=3.99, p=0.005). In all pts, improvements in Fatigue as measured by QLQ-C30 were significantly associated with TSS reductions (OR=2.20, p=0.019) as well as in pts with baseline platelets <50,000/μL (OR=17.88, p=0.008) and <100,000/μL (OR=10.18, p<0.001). Conclusions: In the total pt population, TSS reduction was associated with improvements in spleen response and perceived overall health. This trend was also observed in pts with low baseline platelet counts. Additionally, TSS reduction was significantly associated with improvements in fatigue, a major contributor to poor HRQoL in pts with MF. This reinforces the clinical relevance of measuring TSS using a validated instrument as an endpoint in MF trials. Disclosures Mesa: NS Pharma: Research Funding; Pfizer: Research Funding; Gilead: Research Funding; Incyte Corporation: Research Funding; CTI Biopharma: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; Genentech: Research Funding; Promedior: Research Funding. Off Label Use: This abstract discusses off-label use of pacritinib. Harrison:Shire: Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau; Gilead: Honoraria; CTI Biopharma: Consultancy, Honoraria, Speakers Bureau; Sanofi: Honoraria, Speakers Bureau. Cervantes:Novartis: Consultancy, Speakers Bureau; Sanofi-Aventis: Consultancy; CTI-Baxter: Consultancy, Speakers Bureau. Dean:CTI Biopharma: Employment, Equity Ownership. Wang:CTI Biopharma: Employment, Equity Ownership. Yang:Baxalta: Employment, Other: Stock. 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.

Abstract Background The median survival (OS) of patients with primary myelofibrosis (PMF; 6.5y) is significantly shortened compared to reference population (Cervantes et al, JCO 2012; 30:2981). OS is predicted by the four risk categories of IPSS, Dynamic-IPSS and DIPSS-plus score, nevertheless pts heterogeneity persists within these categories, necessitating improved risk stratification. We recently reported that pts harboring mutations in any one of the prognostically relevant ASXL1, EZH2, IDH1/2 and SRSF2 genes constitute a IPSS-and DIPPS-plus independent Molecular High Risk category (MHR+) characterized by significant reduction of OS and leukemia free survival (LFS) (Vannucchi et al, Leukemia 2013). The aim of this work was to analyze the impact of the number of prognostically relevant mutated genes on OS and LFS in PMF. Patients and methods Two independent cohorts are included, a “test cohort” from Europe, analyzed at diagnosis, and a “validation cohort” from Mayo Clinic, analyzed at any time after diagnosis. Mutation analysis was performed in DNA from whole blood or granulocytes using RTQ-PCR, HRM and direct sequencing; all mutations were confirmed at least twice. The prognostic value of the molecular variables with regard to OS and LFS was analyzed by Cox regression. Test cohort It included 490 pts (median age 61y; males = 301) risk stratified by IPSS into high (n=74, 15%), intermediate-2 (n=93, 19% ), intermediate-1 (n=147, 30%) and low (n=176, 36%). The median follow-up was 3.63y (95% CI, 0.06-28.33); 161 pts died (33.0%), of whom 76 (15.6%) had progressed to acute leukemia after a median of 3.4y (0.04-28.3) from diagnosis. One hundred forty-six pts (29.8%) presented at least one of the four aforementioned mutated genes and were classified as MHR+. The OS of MHR+ pts was significantly reduced compared to patients with no mutations (n=344): 80.7 vs 148.9 mo (HR 2.2, CI95% 1.6-3.03). One hundred twelve (22.8%) pts had 1 mutation and 34 (6.9%) had 2 or more mutations. In univariate analysis presence of 2 or more mutated genes was significantly more detrimental for OS (29.5mo; HR 4.12, IC95% 2.6-6.4) than having 1 mutated gene (84.2mo; HR 1.8, IC95% 1.2-2.5) compared with having no mutations (148.9mo). Multivariate analysis results adjusted for IPSS indicated that having two or more mutations was an independent prognostic factor for OS (HR 2.9, 95% CI 1.8-4.5). Notably, the prognostic relevance of harboring two or more mutations involved both lower (low and intermediate-1; HR 1.87, 95% CI 1.3-2.6) and higher (intermediate-2 and high; HR 1.6, 95% CI 1.2-2.1) categories of IPSS. Also LFS resulted significantly shorter (129mo; HR 3.1, 95%CI 1.9-4.8) in MHR+ pts compared with pts with no adverse mutations (323mo). Having 2 or more mutations correlated with greater reduction of LFS (79.6mo; HR 7.02, CI95% 3.9-12.6) than having one mutation only (133.9mo; HR 2.2, IC95% 1.3-3.7) as compared with no mutations (323.2mo). Multivariate analysis showed that IPSS high risk category (HR 4.5; 95% CI 2.3-8.8) and two or more mutated genes (HR 5.3; 95% CI 2.9-9.8) predicted independently for a significant reduction in LFS. The negative impact on LFS of having 2 or more mutated genes compared to one or no mutations was maintained in the lower (HR 6.4, 95% CI 2.6-15.2) and higher (HR 5.5, 95% CI 2.3-12.8) risk categories. Validation cohort Validation cohort included 262 patients (median age 64 years; males = 167) risk stratified by DIPSS-plus into high (n=89, 34%), intermediate-2 (n=92, 35%), intermediate-1 (n=46, 18%) and low (n=34, 13%). One hundred forty-six pts (56%) displayed none of the four aforementioned mutations, 93 (36%) harbored one mutation whereas 23 (9%) harbored two or more mutations. In univariate analysis, having two or more mutations (HR 3.7; 95% CI 2.2-6.1) was significantly more detrimental for OS than having no mutations, which is more favorable than having one mutation (HR 1.9; 95% CI 1.4-2.7). When adjusted for DIPSS-plus, the presence of two or more mutations retained its significance (HR 2.1; 95% CI 1.3-3.6) and outperformed ASXL1 mutation alone in its prognostic relevance Conclusions Overall, these results show that the number of prognostically relevant mutated genes correlate with OS and LFS in pts with PMF, suggesting that screening for these mutations might help to improve risk stratification. Disclosures: No relevant conflicts of interest to declare.

Abstract Background In the recent International Prognostic Score for Thrombosis in essential thrombocythemia (IPSET-thrombosis), age and history of thrombosis were confirmed as independent risk factors for future thrombosis and the study also identified independent prothrombotic role for cardiovascular (CV) risk factors and JAK2 V617F mutation (Barbui et al. Blood 2012). Methods In the current study, we re-analyzed the original IPSET-thrombosis data in 1019 patients with WHO-defined ET in whom JAK2 mutational status was available, in order to quantify the individual contributions of JAK2 mutations and CV risk factors in conventionally-assigned low and high risk ET, as well as in age- versus thrombosis-defined high risk status. Results After a median follow-up of 6.8 and 5.0 years in conventionally-assigned low- and high-risk patients, respectively, the overall annual rate of total thrombosis (108 events) in conventionally-assigned low- and high-risk patients was 1.11%-pt/y (CI 0.81-1.52) and 2.46%-pt/y (CI 1.94-3.11) respectively (p=0.001), and the difference was mainly due to a higher frequency of arterial thrombosis in high-risk patients (p<0.001).The influence of JAK2 mutational status and CV-risk factors on the rate of thrombosis in conventionally assigned low- and high-risk groups is presented in the table. Table 1. Additional risk factors N (%) Event Rate % pts/yr (95% CI) P-value P-value P-value trend Low risk 506 (50) 39 1.11 (0.81-1.52) None 200 (40) 7 0.44 (0.21-0.92) ref Cardiovascular risk factor 36 (7) 3 1.05 (0.34-3.25) 0.220 0.227 JAK2V617F 213 (43) 21 1.59 (1.04-2.44) 0.001 0.217 Both 52 (10) 8 2.57 (1.29-5.15) <0.001 ref <0.001 High risk 513 (50) 69 2.46 (1.94-3.11) None 111 (22) 10 1.44 (0.78-2.68) ref Cardiovascular risk factor 44 (9) 4 1.64 (0.62-4.37) 0.909 0.067 JAK2V617F 222 (43) 30 2.36 (1.65-3.38) 0.168 0.082 Both 136 (27) 25 4.17 (2.82-6.17) 0.011 ref 0.005 The number of major arterial and venous thrombosis was reported as rates per 100 patient-years and the difference among groups was assessed by Mantel Cox log-rank test i) Conventionally-assigned low-risk group. Amongst 506 patients, 200 (40%) displayed neither JAK2 mutation nor CV risk factors and their annual rate of thrombosis was 0.44%, as opposed to 1.05% in the presence of CV risk factors (P=NS), 1.59% in the presence of JAK2 mutation (p=0.001) and 2.57% in the presence of both CV risk factors and JAK2 mutation (P<0.001). There was no significant difference when low-risk patients with both JAK2 mutation and CV risk factors were compared with either those with CV risk factors only (p=0.227) or those with JAK2 mutation only (p=0.217). ii) Conventionally assigned high-risk group: The absence or presence of one or both of the aforementioned additional risk factors for thrombosis were documented in 111 (22%), 44 (9%), 222 (43%) and 136 (27%) patients, respectively, with corresponding annual rates of thrombosis at 1.44%, 1.64%, 2.36% and 4.17% (Table). High-risk patients with both risk factors had a significantly higher risk of thrombosis compared to their counterparts with the absence of JAK2 mutations and CV risk factors (p=0.011). Additional analysis revealed limited enhancement of thrombosis risk by either JAK2 mutations or CV risk factors or both in patients whose high-risk status was defined by the presence of thrombosis history, regardless of age (P=NS). In contrast, the presence of JAK2 mutations, with or without CV risk factors, might have affected thrombosis risk in patients where high-risk status was defined by age alone (p=0.05). Conclusions The current study suggests the possibility of considering four risk categories in ET: "very low risk" group (age ≤60 years and without thrombosis history, JAK2 mutations or CV risk factors); "low risk" (age ≤60 years and without thrombosis history but with JAK2 mutations or CV risk factors); "intermediate risk" (age>60 years but without thrombosis history or JAK2 mutations); and "high risk" (thrombosis history at any age or JAK2 -mutated patients who are older than 60 years of age). Treatment recommendations for each one of the above-mentioned new risk categories should be examined in the context of prospective controlled studies. Disclosures Barbui: Novartis: Speakers Bureau. Vannucchi:Novartis Pharmaceuticals Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Shire: Speakers Bureau; Baxalta: Membership on an entity's Board of Directors or advisory committees. Buxhofer-Ausch:AOP Orphan: Research Funding. De Stefano:Novartis: Research Funding, Speakers Bureau; Janssen Cilag: Research Funding; Shire: Speakers Bureau; GlaxoSmithKline: Speakers Bureau; Bruno Farmaceutici: Research Funding; Roche: Research Funding; Amgen: Speakers Bureau; Celgene: Speakers Bureau. Gisslinger:Janssen Cilag: Honoraria, Speakers Bureau; AOP ORPHAN: Consultancy, Honoraria, Research Funding, Speakers Bureau; Geron: Consultancy; Sanofi Aventis: Consultancy; Celgene: Consultancy, Honoraria, Research Funding, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau.

Abstract Introduction: There are few effective treatment options available for patients (pts) with myelofibrosis (MF). Pts with thrombocytopenia, a risk factor for shorter overall survival, have poorer prognosis (Gangat, J Clin Oncol 2010). Pacritinib is a kinase inhibitor with specificity for JAK2, FLT3, IRAK1, and CFSR1 and has demonstrated minimal myelosuppression in clinical trials (Hart, Leukemia 2011; Komrokji, Blood 2015; Mesa, ASCO 2015). In the phase III open-label PERSIST-1 trial, a significantly greater proportion of pts treated with pacritinib achieved spleen volume reductions (SVR) ≥35% vs BAT (ITT: 19.1% vs 4.7%, p=0.0003; pts evaluable at baseline and Week 24: 25.0% vs 5.9%, p=0.0001; Mesa, ASCO 2015). This analysis examines pt responses across subgroups. Methods: Pts naive to treatment with JAK inhibitors were randomized 2:1 to receive oral pacritinib 400 mg once daily or BAT. Stratification factors included DIPSS risk status and baseline platelet count. Pts were eligible who had DIPSS Intermediate (Int)-1, Int-2, or High risk disease; absolute neutrophil count >500/µL; palpable splenomegaly ≥5 cm; and baseline Total Symptom Score (TSS) ≥13 using the Modified MPN Symptom Assessment Form Total Symptom Score (MPN-SAF TSS and TSS 2.0). There was no restriction on baseline platelets or hemoglobin (Hgb) levels. The primary endpoint was the proportion of pts achieving SVR ≥35% at Week 24 by centrally-reviewed MRI or CT and the secondary endpoint was the proportion of pts achieving ≥50% reduction in TSS from baseline at Week 24 using 6 symptoms from the MPN-SAF TSS. Pt responses were analyzed by baseline risk factors for MF including platelet counts (<50,000/µL vs ≥ 50,000/µL and <100,000/µL vs ≥100,000/µL), sex, age (≥65 y vs <65 y), JAK2V617F mutation status (positive vs negative), baseline MF diagnosis (primary MF [PMF] vs secondary MF), reticulin and collagen fibrosis staging (> 1 vs ≤1), TSS (≥20 vs <20), white blood cell count (>25×109/L vs ≤25×109/L), peripheral blasts (≥5% vs <5%), Hgb (<10 g/dL vs ≥10 g/dL), transfusion dependency by Gale criteria (Y vs N), time from diagnosis (<12 mos vs ≥12 mos), ECOG PS (2-3 vs 0-1), and bone pain (>3 vs ≤3). In multivariate logistic regressions, the odds of SVR ≥35% and TSS reduction ≥50% at Week 24 were modeled as a function of prognostic factors for MF and adjusted for treatment (pacritinib vs BAT). Results for the 6 symptoms common to both TSS versions are reported. Results: 327 pts were enrolled and randomized (pacritinib: 220, BAT: 107). Overall, 62% of pts had PMF; 32% had baseline platelets <100,000/µL and 16% had <50,000/µL; 75% were positive for JAK2V617F. After a median follow-up of 8.4 months, treatment with pacritinib resulted in consistent rates of SVR across subgroups (Figure 1). When comparing vs BAT, the greatest differences in SVR ≥35% rates between treatment arms were observed in pts with baseline platelets <50,000/μL (+22.9% vs BAT), JAK2V617F-negative pts (+23.0% vs BAT) and those aged <65 y (+21.2% vs BAT). Improvements in TSS (TSS and TSS 2.0 reduction ≥50%) were also consistent for pts receiving pacritinib (Figure 2). By multivariate analysis, SVR ≥35% was significantly correlated only with ECOG PS ≥2 (odds ratio [OR]=2.97, p=0.030) and TSS reduction ≥50% was significantly correlated only with bone pain >3 (OR=0.35, p=0.004). Conclusions: Treatment with pacritinib resulted in consistent rates of SVR ≥35% and TSS reduction ≥50% irrespective of baseline characteristics. Comparisons vs BAT were favorable for all patient subpopulations examined for both endpoints. These results support the use of pacritinib across all intermediate- or high risk MF pt subgroups analyzed. Figure 1. Proportion of Patients Receiving PAC who Achieved ≥35% SVR from baseline to Week 24 (95% CI) Figure 1. Proportion of Patients Receiving PAC who Achieved ≥35% SVR from baseline to Week 24 (95% CI) Figure 2. Proportion of Patients Receiving PAC who Achieved ≥50% TSS reduction (6 common symptoms in MPN-SAF TSS and MPN-SAF TSS 2.0) from baseline to Week 24 (95% CI) Figure 2. Proportion of Patients Receiving PAC who Achieved ≥50% TSS reduction (6 common symptoms in MPN-SAF TSS and MPN-SAF TSS 2.0) from baseline to Week 24 (95% CI) Disclosures 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. Off Label Use: This abstract discusses off-label use of pacritinib. Mesa:Gilead: Research Funding; NS Pharma: Research Funding; Incyte Corporation: Research Funding; Genentech: Research Funding; Novartis Pharmaceuticals Corporation: Consultancy; Promedior: Research Funding; Pfizer: Research Funding; CTI Biopharma: Research Funding. Cervantes:Novartis: Consultancy, Speakers Bureau; Sanofi-Aventis: Consultancy; CTI-Baxter: Consultancy, Speakers Bureau. Prasad:BIOGEN IDEC: Consultancy, Membership on an entity's Board of Directors or advisory committees; BMS: Speakers Bureau. Elinder:Celgene: Consultancy. Recher:Sunesis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Research Funding; Chugai: Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. te Boekhorst:CTI Biopharma: Consultancy; Novartis: Consultancy. Somervaille:Novartis Pharmaceuticals Corporation: Consultancy, Membership on an entity's Board of Directors or advisory committees. Dean:CTI Biopharma: Employment, Equity Ownership. Harrison:Shire: Speakers Bureau; Gilead: Honoraria; CTI Biopharma: Consultancy, Honoraria, Speakers Bureau; Sanofi: Honoraria, Speakers Bureau; Novartis: Honoraria, Research Funding, Speakers Bureau.