Hanson, Curtis A.

Abstract Abstract 460 Background: CYT387 is a potent JAK-1/2 inhibitor that suppresses the in vitro growth of cells harboring JAK2V617F (Leukemia 2009;23:1441) and was effective in a murine model of myeloproliferative neoplasms (MPN) (Blood 2010;115:5232). Aims/Methods: To assess the safety, tolerability, and pharmacokinetic behavior of CYT387 in a Phase I dose-escalation study in patients with high- or intermediate-risk primary myelofibrosis (PMF) and post-PV or post-essential thrombocythemia (ET) myelofibrosis. The secondary objective was evaluation of preliminary efficacy. CYT387 was administered orally once daily in 28-day cycles. Once dose-limiting toxicity (DLT) was identified, a dose-confirmation cohort initiated treatment at the maximum tolerated dose (MTD) or lower. Result: Thirty six subjects (median age 64 years) have been enrolled (targeted accrual 120); 18 each in the dose escalation and dose confirmation phases. Twenty-three subjects had PMF, 8 post-PV MF, and 5 post-ET MF; 81% were JAK2V617F-positive. Median palpable spleen size was 18 cm and 20 subjects (56%) were red cell transfusion-dependent at study entry. Prior treatment included JAK inhibitors (9 and 1 subjects with INCB018424 and TG101348, respectively) and pomalidomide in 9 patients. The median treatment duration to date is 15 weeks (range 4–38). Dose-linear plasma exposures were observed up to 300 mg/day, with mean elimination T1/2 at steady state ranging from 3.9 to 5 hours across doses. Toxicity: All 36 subjects were evaluable for toxicity. At 400 mg/day, 2 of 6 subjects experienced DLT (1 each with asymptomatic grade 3 hyperlipasemia and grade 3 headache that were reversible upon holding drug); consequently, the MTD was declared at 300 mg/day. In the dose-confirmation phase, subjects were started at one of 2 dose levels that were deemed clinically effective: 150 mg/day (n=15) and 300 mg/day (n=3). Thirty-five subjects are currently on active therapy: 100 mg/day (n=2), 150 mg/day (n=20), 300 mg/day (n=10), and 400 mg/day (n=3). CYT387 was well tolerated. No grade 4 non-hematological toxicities were observed. Grade 3 non-hematologic adverse events were infrequent and included increased transaminases (n=2), increased alkaline phosphatase (n=2), headache/head pressure (n=2), increased lipase (n=1), and QTc prolongation (n=1). Thirteen (36%) subjects experienced “first-dose effect” characterized by grade 1 lightheadedness and hypotension; this phenomenon was self-limited and generally resolved within 3–4 hours with rare recurrence. Grade 3/4 thrombocytopenia was seen in 8 (22%) subjects, and treatment-emergent grade 3 anemia was seen in 1 subject only (3%). Treatment-emergent grade 3/4 neutropenia was not observed. Efficacy: Thirty two of 36 subjects who completed at least 1 cycle were eligible for response assessment: Anemia: Twenty two subjects were evaluable for anemia response (baseline Hgb <10 g/dL or red cell transfusion-dependent). Of these, 9 subjects (41%) achieved the threshold of response for “Clinical Improvement (CI)” per the International Working Group for MPN Research and Treatment (IWG-MRT) criteria, including 2 of 4 subjects who were previously treated with INCB018424. An additional 5 subjects experienced a >50% reduction in transfusion requirement, thus increasing the total anemia response rate to 63%. Splenomegaly: Thirty of 32 evaluable subjects had splenomegaly at baseline: median 20 cm; range 10–32 cm. Twenty nine subjects (97%) had some degree of spleen size reduction (median 9 cm; range 2–18 cm): 11 (37%) patients have achieved a minimum 50% decrease in palpable spleen size, thus qualifying them for a CI, including 3 of 8 subjects (38%) who were previously treated with INCB018424. Constitutional symptoms: The proportion of patients with the following symptoms at baseline, are: fatigue (97%), pruritus (22%), night sweats (38%), cough (13%), bone pain (28%), and fever (16%). At last follow up, improvement (complete resolution) in these symptoms was reported by 68% (16%), 86% (57%), 83% (75%), 75% (50%), 78% (44%), and 100% (100%), respectively. Conclusion: CYT387 is first-in-class of the JAK inhibitors with a significant response rate in anemia in myelofibrosis patients. The drug also shows substantial activity in reducing spleen size and controlling constitutional symptoms. CYT387 is well tolerated, and treatment responses have been seen both at (300 mg/day) and below (150 mg/day) the MTD. Disclosures: Pardanani: Cytopia Inc.: Research Funding. Off Label Use: Clinical trial data for CYT387 use in Myelofibrosis. Fida:YM Biosciences Australia: Employment, Equity Ownership. Burns:YM Biosciences Australia: Employment, Equity Ownership. Smith: YM Biosciences Australia: Employment, Equity Ownership.

Abstract Abstract 4122 Background: We have previously identified sole +9, 13q- or 20q- as “favorable” and sole +8 or complex karyotype as “unfavorable” cytogenetic abnormalities in primary myelofibrosis (PMF) (Blood 2010; 115: 496). The purpose of the current study, which includes more than twice the number of patients included in previous studies, was to identify additional prognostically-relevant cytogenetic abnormalities in PMF and refine cytogenetic risk categorization for overall and leukemia-free survival. Methods: Clinical and laboratory data were collected from consecutive patients with PMF seen at our institution and in whom cytogenetic information at or within 1 year of diagnosis was available. Diagnosis of PMF and acute myeloid leukemia were according to the World Health organization (WHO) criteria. Results: A total of 433 patients with PMF were included in the current study. Median age at diagnosis was 65 years. IPSS risk distributions were low in 12% of patients, intermediate-1 in 25%, intermediate-2 in 24% and high in 39%. JAK2V617F mutational frequency was 60%. Cytogenetic findings were normal in 275 (64%) patients. Among the 158 (36%) patients with abnormal karyotype, 109 (69% of abnormal cases) represented sole abnormalities, 23 (15%) two abnormalities and 26 (17%) three or more (i.e. complex) abnormalities. In an effort to identify cytogenetic categories of similar prognosis, each one of 12 operational cytogenetic categories was separately compared with both normal and complex karyotype. Accordingly, we were able to devise a two-tired cytogenetic risk stratification with highly significant differences in overall and leukemia-free survival (Figures 1 and 2): unfavorable (complex karyotype or sole or two abnormalities that include +8, -7/7q-, i(17q), inv(3), -5/5q-, 12p- or 11q23 rearrangement) and favorable (all other cytogenetic findings including normal karyotype). Median survivals of patients with favorable and unfavorable karyotype were 5.2 and 2.0 years, respectively (p<0.0001). The corresponding 5-year survival rates were 51% and 8% (HR 3.1, 95% CI 2.2–4.3; p<0.0001). Multivariable analysis confirmed the IPSS-independent prognostic value of cytogenetic risk categorization (p<0.0001; HR 2.1, 95% CI 1.5–3.1) and also identified thrombocytopenia (platelet count < 100 × 109/L) as another independent predictor of inferior survival (p<0.0001; HR 1.9; 95% CI 1.4–2.6). A similar multivariable analysis showed that cytogenetic risk profile (p=0.001; HR 4.1, 95% CI 1.7–9.6) and platelet count (p=0.04; HR 2.3, 95% CI 1.0–5.0), but not IPSS (p=0.27), predicted leukemia-free survival; the 5-year leukemic transformation rates for unfavorable and favorable karyotype were 46% and 7%, respectively (HR 5.5, 95% CI 2.5–12.0; p<0.0001). These results, in terms of both overall and leukemia-free survival analysis, did not change when patients receiving allo-SCT were censored at the time of their transplant. Among patients with favorable karyotype; the incidences of leukopenia and thrombocytopenia were highest in patients with sole 20q- (41% and 38%, respectively) and lowest in those with sole 13q- (0% and 0%, respectively). Conclusions: The current study provides the rationale and necessary details for incorporating cytogenetic findings and platelet count in future prognostic models for PMF. The study also revealed a highly significant association between sole 20q- and both leukopenia and thrombocytopenia, which suggests a 20q- haploinsufficient gene effect. Disclosures: No relevant conflicts of interest to declare.

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 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.

Abstract Background : In essential thrombocythemia (ET) , ̴ 85% of patients harbor one of three "driver" mutations, with mutational frequencies of approximately 58%, 23% and 4%, for JAK2, CALR and MPL, respectively; ̴ 15% are wild type for all three mutations and are operationally referred to as "triple negative" (Blood. 2014;124:2507). In one of the original descriptions on CALR mutations, CALR -mutated patients with ET, compared to their JAK2-mutated counterparts, were reported to have better survival (NEJM. 2013;369:2379). However, this observation was not supported by subsequent studies while other reports suggested differential prognostic effect from distinct CALR variants in myelofibrosis (Blood. 2014;124:2465). In this study, we sought to clarify the impact of all three mutations, and CALR variants, on overall (OS), myelofibrosis-free (MFS) and leukemia-free (LFS) survival. Methods: Patientswere selected from our institutional database of myeloproliferative neoplasms, based on availability of mutational status inforomation. ET diagnosis was according to WHO criteria (Blood. 2009;114:937). 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 diagnosis to date of death or last contact. MFS and LFS calculations considered fibrotic or leukemic transformation events as uncensored variables, respectively. Cox proportional hazard regression model was used for multivariable analysis. Results : A total of 502 patients (median age 59 year; 61% females) met study eligibility criteria. Median levels of hemoglobin, platelet count and leukocyte counts were 13.7 g/dL, 893 x 10 (9)/L and 8.8 x 10(9)/L, respectively. All patients were annotated for JAK2/CALR/MPL mutations as well as CALR variants; 324 harbored JAK2, 111 CALR and 13 MPL mutations; 54 patients were triple-negative. The 111 CALR-mutated patients included type 1 (n=55), type 2 (n=41) or other (n=15) CALR variants. At a median follow-up time of 9.9 years, 172 (34.3%) deaths, 42 (8.4%) fibrotic progressions, 15 (3%) blast transformations and 12 (2.4%) polycythemic conversions were documented. In univariate analysis, survival data appeared significantly better in "triple negative" patients (median not reached) and inferior in MPL-mutated cases (median 8.5 years) whereas median survival times were similar for JAK2 (18.5 years) and CALR (22.1 years) mutated cases (Figure 1; p=0.0006). However, the difference in survival was no longer apparent (p=0.60) during multivariable analysis that included age and sex, which are known to differentially cluster with specific driver mutations; in the current study, median age/sex distributions for "triple-negative", CALR, JAK2 and MPL mutated cases were 44 years/72% females, 48 years/46% females, 60 years/65% females, 70 years/46% females, respectively (p=<0.0001/0.0007). Of note, both age and sex were independently predictive of shortened survival. OS data remained unchanged when CALR-mutated patients were further stratified into type 1 vs type 2 vs other CALR variants, with similar survival data between the three CALR mutation groups (p=0.98). In univariate analysis, MPL-mutated patients were significantly more prone to fibrotic progression (Figure 2; p=0.0083). The prognostic relevance of MPL mutations to MFS remained significant when age and sex were included in multivariable analysis (p=0.008). In the current cohort, univariate analysis identified lower hemoglobin and lower platelet count as the only other risk factors for fibrotic progression. Multivariable analysis confirmed the independent prognostic relevance of MPL mutations (p=0.003), lower hemoglobin level (p=0.0009) and lower platelet count (p=0.0094) for MFS. There was no significant difference in LFS among the four driver mutational categories (p=0.9): 9 events in JAK2, 6 in CALR, none in triple negative and none in MPL mutated cases. Among the 6 leukemic transformations in CALR-mutated cases, three were type 1, two type 2, and one other CALR variants. Conclusions : Age- and sex-adjusted survival is similar among ET patients with JAK2 vs CALR vs MPL vs "triple-negative" mutational status. Survival is also similar between patients with distinct CALR variants. MPL -mutated patients with ET might be at a higher risk of fibrotic progression. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Pardanani: Stemline: Research Funding.

Abstract Background: Over the last decade there have been three FDA-approved agents available for the treatment of myelodysplastic syndromes (MDS); azacitidine was approved in 2004 for all subtypes of MDS; lenalidomide in 2005 for MDS with del(5q); and decitabine in 2006 for intermediate/high risk MDS. However the ability of these drugs to improve survival outside of clinical trials remains controversial (Neukirchen J, Leuk Res 2015, Bernal T, Leukemia 2015). Objectives : i) Evaluate trends in overall survival (OS) and leukemic transformation (LT) rate amongst primary MDS patients (pts) by year of diagnosis and, ii) Evaluate trends in OS by treatment received. Methods : The Mayo Clinic database was used to identify pts with primary MDS in whom bone marrow histologic and cytogenetic information was obtained at the time of diagnosis. WHO criteria were used for MDS diagnosis and LT. A comparative analysis was performed based on year of diagnosis commensurate with the approval of the aforementioned drugs (Group 1- diagnosis prior to the year 2000, Group 2- year 2001-2004, Group 3- year 2005-2009, and Group 4- year 2010-2014). Results : i) Patient characteristics: A total of 1000 pts met the above-stipulated criteria. 85% of pts were above 60 years of age (median 72 years) with 69% being males. The distribution of pts by year of diagnosis was as follows: Group 1 (n=281)(28%), Group 2 (n=250)(25%), Group 3 (n=264)(26%), and Group 4 (n=205 (21%). Median follow-up of our cohort was 27 months (range; 0-300 months) during which time 808 (81%) deaths and 129 (13%) LT were documented. ii) Comparison of patient characteristics by year of diagnosis: Pts in group 1 and 2 compared with groups 3 and 4 were more likely to present with anemia defined as hemoglobin < 10 g/dl (61%/59% vs 50%/55%)(P =.04). In addition, groups 1 and 2 displayed a higher incidence of RA (5%/4% vs 1% each), and RARS (17%/16% vs 9%/8%), compared to groups 3 and 4 that had a higher incidence of RCMD (37%/44% vs 17%/28%) (P <.001). The IPSS-R risk distribution was not significantly different; 17% very low, 36% low, 21% intermediate, 15% high and 11% very high risk with median survivals of 72, 43, 24, 18 and 7 months, respectively (P <.001). As expected, a higher proportion of pts in groups 3 and 4 (41% and 57% respectively) received "disease-modifying" therapy including allogeneic transplant and hypomethylating agents as opposed to only 6% and 22% in groups 1 and 2 respectively (P <.001). iii) Trends in OS and LT rate by year of diagnosis: The median OS of the entire cohort was 30 months, with median OS and LT rates being similar amongst groups 1 through 4 at 31 vs 33 vs 30 vs 27 months (P =.79) (Figure) and 10% vs 16% vs 12% vs 15% (P =.25), respectively. iv) Trends in OS by treatment received: In univariate analysis survival was significantly better in pts who underwent allogeneic transplant (n=65) with median survival of 55 months vs 26 months for non-transplant pts (P<. 001); and among non-transplant lenalidomide-treated pts (n=44) with median survival of 54 months vs 26 months for the remainder of pts (P =.02). However, these results lost significance on multivariable analysis with the addition of age as a co-variate for transplant pts (P =.28), and IPSS-R as a co-variate for lenalidomide treated pts (P =.10). Excluding transplant pts, pts that received hypomethylating agents (n=158) had similar survival to pts not treated with hypomethylating agents (27 vs 29 months; P =.19, age-adjusted P =.11). In addition, the 54 pts who received other chemotherapeutic agents had similar survival to pts not treated with these agents (33 vs 26 months; P =.57, age-adjusted P =.80). Supportive care alone was utilized in 702 pts that had comparable survival to the 298 pts that received "disease-modifying" therapy (27 months vs 34 months; P =.05, age-adjusted P =.11). Conclusions : In this single center analysis of 1000 pts with primary MDS, stratified by year of diagnosis, the poor outcome of these pts has not improved over the last two decades, in spite of the significantly higher utilization of "disease-modifying" therapy, including hypomethylating agents since 2005. The lack of improvement in survival with hypomethylating therapy is consistent with recently published results from the Spanish MDS registry (Bernal T, Leukemia 2015). However, our retrospective study is not designed to detect marginal survival benefit, which has thus far been reported in only one clinical trial. Figure 1. Figure 1. Disclosures Al-Kali: Novartis: Research Funding. Pardanani:Stemline: Research Funding.

Abstract Background : Hydroxyurea has been the mainstay of cytoreductive therapy in essential thrombocythemia (ET) for over four decades. In 1988, anagrelide was first reported as an effective drug in ET (Silverstein et al. NEJM 1988;318:1292) and hundreds of patients were enrolled in clinical trials, which subsequently led to FDA approval in 1997. As a result, an increasing number of patients with ET were being treated with anagrelide until a subsequent controlled study suggested an inferior treatment outcome with anagrelide compared to hydroxyurea (Harrison et al. NEJM 2005;353:33). In the current study, we examined the impact of the corresponding practice changes on overall, myelofibrosis-free and leukemia-free survival, by comparing patients with ET diagnosed before 1988, between 1988 and 1997, and between 1998 and 2005 Methods: More than 45,000 patient charts with "thrombocytosis" were reviewed to identify those who met either PVSG (older patient cohort) or WHO criteria for diagnosis of ET. Survival was calculated from time of initial diagnosis to the time of last follow-up or death. For leukemia- or fibrosis-free survival, the time of the transformation events was considered as the uncensored variable. Conventional statistics was utilized for all analyses. Patients were divided into three groups commensurate with changes in treatment practices, corresponding to the aforementioned publications; Group 1 patients were diagnosed prior to 1988 (n =222), Group 2 1988 to 1997 (n =253), and Group 3 1998 to 2005 (n =264). Results : A total of 739 patients met the above-stipulated criteria (median age 57 years; 65% females). At a median follow-up of 12.2 years (range: 0.01-43.6 years), 368 (50%) deaths, 48 (6.5%) fibrotic transformations and 23 (3%) leukemic transformations were documented. Median overall survival (OS) was 18.6 years. On multivariable analysis, older age (P <0.001), increased leukocyte count (P <0.001), thrombosis history (P =0.04), and male sex (P<0.0001) were identified as predictors of inferior OS. Myelofibrosis-free survival (MFS) was predicted by platelet count <100 x 10(9)/L and lower hemoglobin level (multivariate P values 0.03 and <0.001, respectively). Leukemia-free survival (LFS) was predicted by increased leukocyte count, on multivariable analysis (P =0.002). Comparison of presenting features and outcome by period of diagnosis: Significant differences, in presenting features, between groups 1, 2, and 3 included age (median 55, 56, and 59 years, respectively; P =0.003), female preponderance (68, 69, and 58%, respectively; P =0.02), platelet count (1080, 995, and 890 x 10(9)/L, respectively; P <0.001), and leukocyte count (10, 9.6, and 8.4 x 10(9)/L, respectively; P <0.001). Median survival was 20.7 years, 19 years and 14.3 years, in groups 1, 2 and 3, respectively (P =0.02) (Figure 1). However, the difference in survival was no longer apparent during multivariable analysis that included age as a covariate (P=0.88). In univariate analysis, MFS was significantly shorter in group 3 patients (P=0.02; Figure 2); borderline significance was retained during multivariable analysis (p=0.13). LFS was similar among the three groups (P = 0.27). Conclusions : The results from the current retrospective study suggest increased rate of progression to myelofibrosis in ET patients diagnosed in the anagrelide era, an observation that is consistent with the results from a previous controlled study (Harrison et al. NEJM 2005;353:33). Regardless, survival in ET in the last four decades remains unchanged. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Pardanani: Stemline: Research Funding.

Abstract INTRODUCTION. Although uncommon, involvement of the central nervous system (CNS) is the most common extramedullary manifestation of Chronic Lymphocytic Leukemia (CLL). Nonetheless, a broad array of conditions can lead to neurologic symptoms in CLL patients and distinguishing between clinically significant CLL involvement of the CNS and other etiologies can be challenging. The actual prevalence of CNS involvement by CLL is unknown, the only available data being case reports and small case series. METHODS. Between 01/1995 and 11/2014, 186 of the 4317 (4%) patients with CLL followed at our center underwent an MRI of the CNS (e.g. brain, spine) and/or a lumbar puncture (LP) with cerebral spinal fluid (CSF) analysis to evaluate neurologic symptoms. As the mere presence of CLL cells in the CSF is not diagnostic of clinically significant CNS disease, a final diagnosis of clinically significant CNS involvement by CLL was established by the collaborative review of the pathologist, neurologist and treating hematologist based on comprehensive work-up and multi-disciplinary evaluation. RESULTS. After evaluation, the etiology of neurologic symptoms was clinically significant involvement of the CNS by CLL in 19 (10%) patients, CNS Richter Syndrome (RS) in 15 (8%), infection in 42 (23%), autoimmune conditions in 31 (17%), other cancer in 9 (5%), and another etiology in 70 (37%). The sensitivity of LP to detect clinically significant CNS involvement by CLL was 89%, however its specificity was only 42% where CLL cells were also frequently observed in the CSF in concomitance with inflammatory processes, such as infections and autoimmune disease. Factors associated with clinically significant CNS involvement by CLL/RS were mutated IGHV (p=0.04), low CSF glucose (p=0.02), elevated CSF total nucleated cells (TNC)(p=0.004), lymphocytes (p=0.02) and CLL cells, both as absolute count (p=0.05) and percentage of TNC (p=0.02). Median OS among patients with clinically significant CNS involvement by CLL or RS were 21 and 11 months, respectively. Median OS for patients with neurological symptoms secondary to infection was 6 months, to autoimmune process was 63 months, to other cancers was 19 months, and to other non-CLL related etiologies was 37 months. CONCLUSIONS. Clinically significant CNS involvement by CLL and RS are rare conditions. Neurologic symptoms in patients with CLL are attributable to non-CLL-related etiologies in the majority of cases, even when CLL B-cells are present in the CSF. Analysis of the CSF has high sensitivity but limited specificity to distinguish clinically significant CNS involvement by CLL from other etiologies. Comprehensive evaluation is required before attributing neurologic symptoms to CLL. Disclosures No relevant conflicts of interest to declare.