Citations

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 459 Background: A Phase I study of TG101348, a potent, oral JAK2-selective inhibitor in patients with high- or intermediate-risk primary, post-polycythemia vera (PV) and post-essential thrombocythemia (ET) myelofibrosis (MF) recently completed enrollment. Data from the dose escalation cohort (n=28; 30–800 mg administered as a single daily dose) showed dose-linear plasma exposure, with mean elimination T1/2 at steady state ranging from 16 to 34 hours. The dose-limiting toxicity was reversible asymptomatic grade 3 or 4 amylasemia/lipasemia; the maximum tolerated dose was 680 mg. We now present updated results from an extension study in which subjects continued treatment beyond six 28-day cycles. Result: In the entire study, 59 subjects (median age 64 years) were treated. Forty four patients had PMF, 12 post-PV MF, and 3 post-ET MF; 86% were JAK2V617F-positive. Median palpable spleen size was 18 cm and 21 (36%) patients were transfusion-dependent at study enrollment. Forty three (73%) subjects continued treatment on the extension study; the median (range) cumulative exposure to TG101348 was 380 days (170-767); the number of cycles of treatment completed ranged from 7–29, and the proportion of subjects who completed 12, 18, and 24 cycles of treatment was 72%, 28%, and 14%, respectively. The median (range) treatment dose at data cutoff was 440 mg/day (120 to 680 mg/day; n = 35). Toxicity: TG101348 was well tolerated. Non-hematologic, at least possibly related adverse events included nausea (69%; Grade 3=3%), diarrhea (64%; Grade 3=10%), and vomiting (58%; Grade 3=3%), that were dose-dependent; the symptoms were self-limited or controlled with symptomatic treatment and/or dose reduction. Also observed were asymptomatic increases in serum lipase (27%), AST/ALT (27%/25%), creatinine (24%), and alkaline phosphatase (17%). Grade 3/4 hematological adverse events possibly related to TG101348 included treatment-emergent anemia (35% of patients who were not transfusion dependent at baseline), thrombocytopenia (24%), and neutropenia (10%). Spleen: During cycles 1–6, 42% of patients achieved Clinical Improvement (CI) per the International Working Group for Myeloproliferative Neoplasms Research and Treatment (IWG-MRT) criteria for spleen response. The CI rate for the 43 subjects who continued treatment beyond 6 cycles was 65%, and the median time (range) to CI was 140 days (77-802). After 12 cycles, 36 (95%) of the 38 evaluable patients had some degree of spleen size reduction; 32 (85%), 26 (68%), and 10 (26%) of subjects had a minimum 25%, 50%, and 100% decrease in palpable splenomegaly. JAK2V617F allele burden: Of the 48 JAK2V617F mutation-positive subjects, 23 (48%) had a baseline mutant allele burden of >20%. Of these, 20 subjects with a baseline median allele burden (range) of 62% (23% to 100%) completed at least 6 cycles of treatment. Sixteen subjects (80%) exhibited a median 62% (range 6% to 96%) decrease in JAK2V617F burden, including 9 (45%) with a ≥50% decrease; 4 subjects (20%) had increases (range 18% to 58%). Eighteen subjects (78%) completed 12 cycles of treatment; 13 (72%) had a median 50% decrease (range 29% to 82%), including 7 (39%) subjects with a ≥50% decrease; 5 subjects (28%) had no change or increases (range 0% to 22%) in JAK2V617F. Constitutional symptoms: For patients with data at baseline and cycle 6, early satiety, fatigue, night sweats, cough, and pruritus were reported by 56%, 47%, 24%, 22%, and 19% of subjects, respectively. Improvement (complete resolution) rates observed at cycle 6 were: 75% (40%), 65% (29%), 89% (89%), 88% (75%), and 100% (57%) for the aforementioned symptoms, respectively. Leukocytosis/Thrombocytosis: Leukocytosis was present at baseline in 33 subjects; following 6 and 12 cycles of therapy, 57% (n=28) and 56% (n=25) achieved normal WBC counts. Thrombocytosis was noted at baseline for 10 (17%) subjects; following 6 and 12 cycles of therapy, 90% (n=10) and 88% (n=8) achieved normal platelet counts. Conclusion: The current study provides proof-of-concept that selective JAK2 inhibition has anti-myeloproliferative/anti-clonal activity in myelofibrosis. The majority of subjects treated with TG101348 for more than 6 cycles experienced a rapid, significant, and durable decrease in splenomegaly, normalization of leukocyte/platelet counts, and improvement of disease-related symptoms, all within the context significantly decreased JAK2V617F burden. Disclosures: Off Label Use: There is no FDA approved drug for Myelofibrosis.All the drugs discussed will be off-label. Stone:Novartis: Consultancy. Silverman:TargeGen: Consultancy. Shorr:TargeGen: Employment, Equity Ownership.

Abstract Background: SL-401 is a novel targeted therapy directed to the interleukin-3 receptor (CD123), a target overexpressed by many hematologic malignancies. SL-401 is currently being advanced through clinical trials in patients with a variety of CD123+ malignancies including blastic plasmacytoid dendritic cell neoplasm (BPDCN), acute myeloid leukemia (AML) in remission with high relapse risk, and multiple myeloma. CD123 has been shown to be expressed on myeloproliferative neoplasm (MPN) cells as well as microenvironmental immune cells, namely plasmacytoid dendritic cells (pDCs), in the bone marrows of some patients with MPN including chronic myelomonocytic leukemia (CMML). Microenvironmental pDCs have been implicated in promoting plasma cell disorders and preliminary data suggest that pDCs could play a related role in some myeloid neoplasms. Accordingly, a therapy directed at both CD123-expressing myeloid cells and neighboring CD123-expressing pDCs could provide therapeutic benefit. SL-401 is being evaluated in patients with advanced, high-risk MPN, including systemic mastocytosis (SM), myelofibrosis (MF), primary eosinophilic disorders (PED), and CMML. Preliminary results are reported here. Methods & Results: This multicenter, single-arm Phase 2 trial of patients with advanced, high risk MPN includes a lead-in (stage 1) and expansion (stage 2). In stage 1, patients receive SL-401 as a daily IV infusion at 7, 9, 12 ug/kg/day, or higher for days 1-3 of a 21-28 day cycle in a 3x3 design. In stage 2, patients receive SL-401 at the dose determined in stage 1. Study objectives include characterization of the safety profile, including determination of the maximum tolerated or tested dose, and detection of preliminary efficacy signals including evaluation of tumor response and progression free survival by standard criteria. As of 7/20/16, 6 patients with MPN (MF, n=3; CMML-2, n=2; CMML-1, n=1) received SL-401 (7 ug/kg, n=3; 9 ug/kg, n=3). The median age was 66 years (range: 42-81 years). Patients treated at all doses received 1+ to 2+ cycles (ongoing) of SL-401. The most common treatment-related adverse events (AEs) were thrombocytopenia (2/6; 33%) and fatigue (2/6; 33%); the most common ≥ Grade 3 treatment-related AEs were thrombocytopenia (2/6; 33%) and anemia (1/6; 17%); there has been no DLT. Efficacy assessments are ongoing. Patients are currently enrolling in the 12 ug/kg/day cohort. Conclusions: Initial dosing of SL-401 appears to be well-tolerated in patients with MPN and CMML, with no unexpected AEs observed. Given CD123 expression on myeloid neoplastic cells as well as microenvironmental immune cells (namely, pDCs), SL-401 may offer a novel, targeted therapeutic approach in patients with high-risk MPN and CMML of unmet medical need. Enrollment continues in stage 1 of this ongoing Phase 2 trial and updated safety and efficacy data will be presented. Clinical trial information: NCT02268253. Disclosures Gupta: Novartis: Consultancy, Honoraria, Research Funding; Incyte Corporation: Consultancy, Research Funding. Carraway:Incyte: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Baxalta: Speakers Bureau; Celgene: Research Funding, Speakers Bureau; Amgen: Membership on an entity's Board of Directors or advisory committees. Schiller:Incyte Corporation: Research Funding. Talpaz:Incyte Corporation: Other: Travel expense reimbursement, Research Funding; Ariad: Other: Expense reimbursement, travel accomodation expenses, Research Funding; Novartis: Research Funding; Pfizer: Consultancy, Other: travel accomodation expenses, Research Funding. McCloskey:Novartis: Speakers Bureau; Incyte: Consultancy; Ariad: Consultancy, Speakers Bureau; Amgen: Speakers Bureau. Lee:Alexion Pharmaceuticals: Consultancy; Amgen: Consultancy; Baxalta: Consultancy; Boehringer Ingelheim: Consultancy; Pfizer Inc: Consultancy. Yacoub:Alexion: Honoraria; Seattle Genetics: Consultancy, Honoraria, Speakers Bureau; Incyte: Consultancy, Honoraria, Speakers Bureau. Ali:Incyte Corporation: Research Funding. Chen:Stemline Therapeutics, Inc.: Employment, Equity Ownership. Shemesh:Stemline Therapeutics: Employment, Equity Ownership. Brooks:Stemline Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties.

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 Background : Anemia is one of the most prominent symptoms in primary myelofibrosis (PMF) and is often associated with inferior quality of life and survival. Current drugs, including JAK inhibitors, are suboptimal in the treatment of PMF-associated anemia and better information on its pathogenesis is critical for the development of more effective drugs. In the current study of JAK2/CALR/MPL annotated patients with PMF, we examined its correlation with both "driver" and "non-driver mutations", as well as cytogenetic abnormalities, in order to gain better insight into its pathogenesis. Methods: Study patients were selected based on availability of "driver" 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). Considering their relatively high mutational frequency in PMF, subsets of patients were also screened for ASXL1, spliceosome component (SF3B1, U2AF1, SRSF2, ZRSR2) and TET2 mutations. Cytogenetic analysis and reporting was done according to the International System for Human Cytogenetic Nomenclature. Statistical analyses considered clinical and laboratory parameters obtained at time of first referral at the Mayo Clinic. Results : Analysis was conducted on 722 patients (median age 64 years; 64% males). DIPSS-plus risk distribution was 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). Non-driver mutations screened included ASXL1 (n =480; mutated 38%), SRSF2 (n =474; mutated 14%), U2AF1 (n =457; mutated 16%), SF3B1 (n =328; mutated 8%), ZRSR2 (n =180; mutated 11%) and TET2 (n =180; mutated 18%). Karyotype was normal in 60%, favorable in 28% and unfavorable in 12%. Anemia was defined as being absent (normal sex-adjusted hemoglobin level; n =110; 15%), mild (hemoglobin level of ≥10 g/dL but below sex-adjusted normal value; n =263; 36%), moderate (hemoglobin level below 10 g/dL but not transfusion-dependent; n =108; 15%) and severe (transfusion-dependent anemia; n =241; 33%). Presence of at least mild anemia was associated with abnormal karyotype (p=0.006) with no difference between favorable and unfavorable abnormalities, U2AF1 (p=0.002), TET2 (p=0.02) and ASXL1 (p=0.04) mutations; other significant associations included male sex and older age. Presence of moderate to severe anemia was associated with U2AF1 (p<0.0001), SRSF2 (p=0.007) and driver mutations other than CALR type 1/type 1-like (p<0.0001). Presence of severe anemia was associated with U2AF1 (p<0.0001), SRSF2 (p=0.003) and non-CALR driver mutations (17% incidence in both types of CALR variants vs 51% in triple negative, 35% JAK2, 39% MPL mutated cases; p<0.0001). An association with older age but not gender was also noted for both moderate to severe and severe anemia (p<0.0001). During multivariable analysis, independent associations with moderate to severe anemia were confirmed for U2AF1 (p<0.0001), SRSF2 (p=0.007) and age (p=0.0001), but not driver mutation profile (p=0.30). A similar analysis for severe anemia also identified U2AF1, SRSF2 and age as being significantly relevant. Conclusions : The current study identifies older age and the spliceosomal mutations U2AF1 and SRSF2 as having strong and independent association with moderate to severe anemia in PMF. Targeting the spliceosome machinery or its mutant components offers a potential approach in the treatment of PMF-associated anemia. Disclosures Pardanani: Stemline: Research Funding.

Abstract Background The 2016 revised World Health Organization (WHO) classification system distinguishes prefibrotic (pre-PMF) from overtly fibrotic (overt PMF) primary myelofibrosis, based on the respective absence or presence of grade ≥2 bone marrow (BM) reticulin fibrosis (Blood. 2016;127:2391). The main objective of the current study was to determine the prognostic relevance of this distinction and compare clinical and genetic features between the two entities. Methods Study patients fulfilled the 2016 WHO criteria for the diagnosis of pre-PMF or overt PMF (Blood. 2016;127:2391). The degree of BM reticulin fibrosis was based on "real life" BM reports from Mayo Clinic hematopathologists and often in accordance with the European consensus scoring system (Haematologica 2005;90:1128). Targeted next generation sequencing was used to screen for prognostically-relevant mutations (Blood 2015 126:354). Statistical analyses considered clinical and laboratory parameters obtained at time of BM examination that was graded for reticulin fibrosis. Results Patient characteristics: Analysis was conducted on 467 patients (median age 64 years; 62% males), including 63 with pre-PMF and 404 with overt PMF. 302 (65%) patients harbored JAK2 mutations, 90 (19%) CALR, 24 (5%) MPL and 51 (11%) were "triple-negative"; among the 90 CALR-mutated cases, 74 (82%) were classified as "type 1/type 1-like". Dynamic international prognostic scoring system (DIPSS)-plus risk distribution (JCO 2011;29:392) was 30% high, 38% intermediate-2, 16% intermediate-1 and 15% low; 29% displayed red cell transfusion-dependency, 29% constitutional symptoms, 70% palpable splenomegaly and 37% abnormal karyotype, including 13% with unfavorable karyotype. 308 patients were screened for ASXL1 mutations with 39% mutated, 305 for SRSF2 mutations with 16% mutated, 291 for U2AF1 with 18% mutated, 264 for SF3B1 with 6% mutated, 240 for EZH2 with 5% mutated and 118 for IDH1/2 with 7% mutated. BM reticulin fibrosis was reported as grade '0' in 5 (1%) patients, grade '1' in 58 (12%), grade '2' in 169 (36%) and grade '3' in 235 (50%). After a median follow up of 3 years, 273 (59%) deaths and 42 (9%) leukemic transformations were documented. Clinical, cytogenetic and molecular comparisons between pre-PMF vs overt PMF: Significant differences included higher hemoglobin level (p<0.0001), higher platelet count (p<0.0001), higher incidence of thrombocytosis (p<0.0001), lower circulating blast percentage (p=0.0002), lower incidence of constitutional symptoms (p=0.003), lower incidence of palpable splenomegaly and lower DIPSS-plus risk distribution (p=0.0004), in pre-PMF, compared to overt PMF. There were significantly more triple-negative patients with pre-PMF (22% vs 9% for overt PMF; p=0.02) but otherwise no significant difference in the distribution of ASXL1, SRSF2, U2AF1, SF3B1, EZH2 or IDH1/2 mutations or incidence of unfavorable karyotype. Survival analysis: In univariate analysis, all 8 variables included in DIPSS-plus were significantly associated with shortened survival (p<0.001 in all instances). Significant risk factors in univariate analysis also included overt PMF vs pre-PMF (p=0.002; HR 2.0, 95% CI 1.3-3.1), absence of CALR type 1/type 1-like (p<0.0001) and presence of ASXL1 (p<0.0001) or SRSF2 (p<0.0001) mutations. The significant difference in survival between pre-PMF and overt PMF was independent of DIPSS-plus (p=0.03), driver mutational status (p=0.001), ASXL1 (p=0.008) and SRSF2 (p=0.02) mutations; no significant difference in leukemia-free survival was noted (p=0.25). The survival difference between pre-PMF and overt PMF was most evident in high/intermediate-2 DIPSS-plus risk groups (Figure). Of note, we found no difference in survival when patients with grade '0' were compared to those with grade '1' reticulin fibrosis (p=0.96) and when those with grade '2' were compared with grade '3' (p=0.08). Conclusion The current study demonstrates the risk-adjusted prognostic relevance of the WHO distinction between pre-PMF and overt PMF. The two clinic-pathologic entities were otherwise similar in their spectrum of prognostically-relevant mutations or cytogenetic abnormalities, although pre-PMF clustered with thrombocythemic and triple-negative phenotype and overt PMF with adverse clinical features. Figure Figure. Disclosures No relevant conflicts of interest to declare.

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 Introduction Polycythemia vera (PV) and Essential thrombocytosis (ET) progress to myelofibrosis (MF). Extramedullary hematopoeisis (EMH) is common in patients with primary or secondary MF, and can occur in the lungs. Pulmonary EMH can cause recurrent pleural effusions, pulmonary hypertension, and right heart failure with symptoms of dyspnea, cough, and fatigue. Low dose single fraction whole lung irradiation (WLI) has been utilized at our institution, and our preliminary report of 4 patients noted symptomatic improvement with no reported acute side effects. Here we report on a larger cohort of 57 patients as well as long term outcomes for 20 of those patients, including the original 4 patients. Methods We performed a retrospective review of 57 patients with myelofibrosis and pulmonary EMH who received single fraction WLI to a dose of 100 cGy at the Mayo Clinic from March 2001 to March 2014. Data related to the following parameters was collected: initial diagnosis, age at initial diagnosis, date of progression to myelofibrosis, initial treatment prior to radiation therapy, whole body bone marrow scan findings if available, and response to WLI. Overall survival was measured using the Kaplan Meier method. Chi-square analysis was used to evaluate predictors of response to WLI. Results The median age at first WLI was 67 years (45-84 years), and 33 patients (58%) were male. Twenty-two patients (39%) had a diagnosis of primary MF, 27 patients (47%) had PV or ET, and 8 patients (14%) had another cause of secondary MF. At the time of WLI, 27 patients (47%) were on supplemental oxygen, and 3 patients (5%) were in the intensive care unit. Hydroxyurea (n=14, 25%), JAK2 inhibitors (n=9, 16%), Anagrelide (n=3, 5%), and Thalidomide and Prednisone (n=3, 5 %) were the most frequent treatments prior to WLI. EMH was confirmed on bone scan in 38 patients (67%). In the remaining 19 patients, a diagnosis of EMH was made based on clinical impression. This included symptoms of dyspnea, cough, and fatigue, echocardiographic findings of pulmonary hypertension, and in some patients recurrent pleural effusions (n=13), positive lymph node biopsy (n=2), or thoracentesis (n=1). Twenty-eight (49%) patients had other active cardiac or pulmonary conditions that likely contributed to their clinical symptoms. These patients were receiving concurrent treatment for their other conditions. In some patients there were multiple coexisting conditions. Clinical improvement occurred in 30 patients (53%). The median time from WLI to symptomatic improvement was 10 days (1-174 days). Twenty-four patients (42%) did not have clinical improvement. Nine patients (16%) had stable symptoms, 15 patients (26%) had progressive symptoms, and 3 patients (5%) had insufficient follow up. In the group of patients with concurrent active cardiac or pulmonary conditions, 15 patients (54%) had clinical improvement following WLI. In the 29 patients who had solitary EMH, 15 (52%) patients had clinical improvement. There was no difference in response rates related to oxygen use at the time of WLI. Six patients (11%) received WLI on multiple occasions. There was no difference in the percentage of patients with positive bone marrow scans (67%) in the 2 groups. The median overall survival was 259 days for all patients. Patients who improved after WLI had a median survival of 325.5 days compared to 122.5 days for patients who did not improve. No new hematologic abnormalities temporally related to WLI were reported. Long term follow up beyond 1 year was available for 20 patients (35%). No patients developed pneumonitis or pulmonary fibrosis that was considered related to WLI. One patient received a diagnosis of an upper esophageal squamous cell carcinoma 6 years after WLI and allogeneic stem cell transplant. Conclusion Our prior study showed WLI is safe and effective in a small number of patients with isolated pulmonary EMH from MF. The current study confirms the long term safety of this approach. Our results suggest WLI may contribute to symptomatic improvement in 1/2 of patients, even in the common clinical situation of multiple coexisting cardiac and pulmonary conditions. Repeat WLI is also well tolerated and can result in symptomatic improvement. We did not find any factors that predicted response to WLI. WLI should be considered in patients who have clinically proven pulmonary EMH and associated symptoms, even in the presence of other conditions, and can be repeated safely. 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: In a previously published phase-1/2 study, momelotinib (a JAK 1/2 inhibitor) induced 53% anemia, 39% spleen and >50% constitutional symptoms response rates in patients with myelofibrosis (MF) (Pardanani A, et al. Leukemia. 2013;27:1322). The particular study included 100 patients from the Mayo Clinic who experienced 43% spleen and 44% anemia response rates (Pardanani et al. Leukemia. 2015;29:741); CALR and ASXL1 mutations independently predicted spleen but not anemia response. In the current study, we examined the impact of momelotinib therapy on DIPSS-plus- and molecular risk-adjusted survival. Methods: The current study represents sponsor-independent analysis of long-term survival among 100 consecutive Mayo Clinic patients who received momelotinib therapy as part of a larger (n =166) phase-1/2 study (NCT00935987). Safety and efficacy data from NCT00935987, as well as protocol design and drug dosing and schedule, have already been formally reported and not reiterated here (Pardanani A, et al. Leukemia. 2013;27:1322; Pardanani A, et al. Leukemia. 2015;29:741; Abdelrahman RA, et al. BJH. 2015;169:77). All statistical analyses considered clinical and laboratory parameters obtained at the time of entry to study. Survival analysis was considered from the date of study entry to date of death or last contact. Cox proportional hazard regression model was used for multivariable analysis of survival. Samples from time of study entry were used for mutation screening. Driver mutations were classified into two prognostically-relevant groups: CALR type 1/type 1-like (favorable) vs all others including CALR type 2/type 2-like, JAK2, MPL and triple-negative (unfavorable). Results: 100 patients with MF (median age 66 years; 58% males) were treated at the Mayo Clinic between 11/20/09 and 11/10/10; 64 patients had primary MF, 22 post-polycythemia vera MF and 14 post-essential thrombocythemia MF. Baseline data: DIPSS-plus risk distribution was 63% high, 36% intermediate-2 and 1% intermediate-1 (JCO 2011;29:392); for the purposes of the current analysis, the single patient with intermediate-1 risk disease was included in the intermediate-2 category. 54 (54%) patients displayed abnormal karyotype. 73 (73%) patients harbored JAK2, 16 (16%) CALR, 7 MPL and 4 "triple-negative". Among the 16 CALR -mutated cases, 13 were classified as "type 1/type 1-like". 94 patients were screened for ASXL1 mutations; 41 (44%) were mutated. Follow-up data was updated in July 2015, providing a minimum follow-up of over 4.5 years since the last patient registration on the protocol. At a median follow-up of 3.2 years, 67 (67%) deaths and 13 (13%) leukemic transformations were documented. Median survival from the time of study entry was 3.2 years and was affected by driver mutation prognostic groups (median survival "not reached" for "favorable" vs 3 years for "unfavorable"; p=0.01), ASXL1 mutational status (median survival 3.9 years in unmutated vs 2.5 years in mutated; p=0.02) and DIPSS-plus risk stratification (median survival 2.6 years in high-risk vs 4 years in intermediate-2 risk; p=0.07). In order to assess the impact of momelotinib on long-term outcome, we compared survival of the study cohort (n =100) with that of 442 consecutive Mayo Clinic patients with high or intermediate-2 risk primary MF (median age 67 years; 66% males). There was no significant difference between this control group of PMF patients versus the momelotinib patient cohort in distribution of age (p=0.56), sex (p=0.12), JAK2/CALR/MPL mutational status (p=0.41) or ASXL1 mutational status (p=0.9); however, the momelotinib cohort had a higher fraction of patients with DIPSS-plus high-risk disease (63% vs 47%; p=0.004). Overall survival was similar between the momelotinib cohort and the control group of PMF patients who were not treated with momelotinib (Figure 1; p=0.99); the difference in survival remained not significant during multivariable analysis that included risk stratification by DIPSS-plus (p=0.32), "favorable" vs "unfavorable" driver mutational status (p=0.78) or ASXL1 mutational status (Figure 2; p=0.61). Conclusions: In the current long-term study, we could not demonstrate a survival impact from momelotinib therapy in myelofibrosis. Although adjusted for clinical and molecular risk status, our study is retrospective and cannot be relied upon to discount marginal survival effect. Disclosures Al-Kali: Novartis: Research Funding. Pardanani:Stemline: Research Funding.