Abdelrahman, Ramy A.

Abstract Background : Momelotinib is a JAK1 and JAK2 inhibitor that is currently being evaluated in phase-3 clinical trials for the treatment of myelofibrosis (MF) (NCT01969838, NCT02101268). In a phase-1/2 clinical trial of patients with MF, the drug was shown to improve anemia, reduce spleen size and alleviate symptoms (Leukemia 2013;27:1322). In the current study, we considered 100 consecutive patients from the Mayo Clinic who received momelotinib therapy, in order to identify molecular and cytogenetic predictors of treatment response and survival from the time of study entry. Methods : The study patients constituted part of a phase-1/2 clinical trial (NCT00935987) using momelotinib in MF. Details of the protocol, including inclusion and exclusion criteria were previously published (Leukemia 2013;27:1322). Response was determined by the 2006 response criteria published by the IWG-MRT. Data analysis and interpretation was carried out independent of any influence from the sponsor. 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. MF type was primary in 64% of the patients and post-polycythemia vera/essential thrombocythemia in 36%. DIPSS-plus risk distribution was 63% high, 36% intermediate-2 and 1% intermediate-1. Red cell transfusion dependency was documented in 49% and palpable spleen size of >5 cm (median 19 cm) in 92%. All patients were annotated for JAK2/CALR/MPL mutations with respective frequencies of 73%, 16% and 7%. Frequencies for other mutations included 42% for ASXL1 (84 evaluable) and 18% for SRSF2(78 evaluable). All patients were evaluable for karyotype, which was unfavorable in 17%. Previous treatment included other JAK inhibitors in 21 patients, thalidomide/lenalidomide/pomalidomide in 31 and hydroxyurea or other cytoreductive agents in 55. Momelotinib was initiated at 100 mg/day in 3 patients, 150 mg/day in 21, 150 mg twice-daily in 20, 200 mg/day in 3, 300 mg/day in 47 and 400 mg/day in 6. The maximum momelotinib dose was 150 mg/day in 6 patients, 150 mg twice-daily in 20, 300 mg/day in 68 and 400 mg/day in 6. Treatment duration was <6 months in 12 patients, 6-12 months in 22, 12-24 months in 19 and >24 months in 47. Genetic correlates of response to momelotinib : Overall response rate was 57% and included no complete remissions (0%), one (1%) partial remission and 57 (57%) clinical improvements (CI). Response rates for spleen/liver and anemia were 43% (91 evaluable) and 44% (68 evaluable), respectively. Transfusion independency was achieved in 25 (51%) of 49 evaluable cases. Spleen/liver response rate was significantly affected by JAK2/CALR/MPL mutational status (34% vs 73% vs 60%, respectively, and 50% in triple-negative; p=0.04), CALR mutated vs unmutated status (73% vs 37%; p=0.009), and unmutated vs mutated ASXL1 (53% vs 29%; p=0.035). Furthermore, all 8 (100%) patients who were CALR+/ASXL1- responded vs 6 (25%) of 24 CALR-/ASXL1+ vs 3 (50%) of 6 CALR+/ASXL1+ vs 16 (43%) of 37 CALR-/ASXL1- patients (p=0.003). Spleen/liver response rates were not affected by SRSF2 mutations (p=0.93) or karyotype (p=0.41). Anemia response rate was not affected by JAK2/CALR/MPL (p=0.81), ASXL1 (p=0.16), SRSF2 (p=0.12) or CALR/ASXL1 (p=0.42) mutational status or karyotype (p=0.65). The number of informative cases for EZH2, IDH, SF3B1 and U2AF1mutations were not adequate enough to warrant similar analysis. Genetic correlates of survival from time of protocol entry : Median follow-up after the institution of protocol drug therapy was 35 months (range 1-49). During this period, 57 (57%) deaths and 12 (12%) leukemic transformations were documented. On multivariable analysis, shortened survival was predicted by the presence of ASXL1 (p=0.01; HR 2.1, 95% CI 1.2-3.8) or SRSF2 (0.01; HR 2.4, 95% CI 1.2-4.8) mutations and the absence of CALR mutations (p=0.03; HR 3.2, 95% CI 1.1-8.9). Karyotype was significant on univariate (p=0.01) but not in multivariable (p=0.6) analysis that included the aforementioned mutations. The prognostic relevance of each specific mutation was DIPSS-plus independent. Conclusions : We demonstrate significant associations between CALR and ASXL1 mutational status and spleen response to momelotinib therapy in MF. We also show that momelotinib therapy did not overcome the inferior survival associated with the presence of ASXL1 or SRSF2 mutations or the absence of CALR mutations. Disclosures No relevant conflicts of interest to declare.

Abstract Introduction: The utility of patient reported symptoms and serum tryptase levels in distinguishing those with systemic mastocytosis (SM) versus mast cell activation syndrome (MCAS) versus those not meeting formal diagnostic criteria for SM or MCAS has not been systematically examined. Methods: This study was approved by our institutional review board. Patients were referred for suspected SM based on symptoms of mast cell activation, osteopenia, skin rash, etc., or had an established diagnosis of SM. All patients were given a Mastocytosis Symptom Assessment Form (MastSAF) to complete at their initial evaluation. The MastSAF is comprised of 36 symptom questions to be graded on a scale of 0 (absent) to 10 (worst imaginable), and is organized around 9 symptom clusters: gastrointestinal (8 questions), constitutional (3 questions), musculoskeletal (5 questions), cutaneous (4 questions), neuropsychological (6 questions), genitourinary (3 questions), respiratory (4 questions), angioedema (1 question), and cardiovascular (2 questions). All patients underwent bone marrow biopsy and serum tryptase level assessment. SM was diagnosed by 2008 WHO criteria. In the presence of characteristic symptoms, if clonal or abnormal mast cells were not identified, and if serum/urine mast cell mediator levels were increased, then non-SM associated, non-monoclonal MCAS was diagnosed. Results: A total 53 patients were studied. 1) SM: Of 28 patients, 13 had indolent SM (ISM), 9 aggressive SM (ASM) and 6 SM with associated hematological disease (SM-AHD) The median total symptom score was 47 (range 8-159). The median (range) for SM subgroups was: ISM 51 (9-159), ASM 55 (19-157) and SM-AHD 27 (8-131) (p=0.2). The normalized median score for individual symptom categories (total median score/no. of symptoms per category) in order of severity was cutaneous 1.9, gastrointestinal 1.8, constitutional 1.7, neuropsychological 1.3, respiratory 1.3, musculoskeletal 0.9, cardiovascular 0.3, genitourinary 0.3, and angioedema 0. Symptom severity was not significantly different among the 3 SM subgroups, except for constitutional symptoms (median score ASM 9, ISM 4, SM-AHD 2.5, p=0.02). The median (range) tryptase level was 48.4 ng/mL (8.8-282); four patients (14%) had a baseline level <20 ng/mL. The median (range) tryptase level among SM subgroups was: ISM 46.9 (8.8-225), ASM 103 (29.4-282), and SM-AHD 43.5 (28.5-233) (p=0.1). When considering patients with tryptase level ≥50 versus <50 ng/mL, symptom scores were not significantly higher in the former group with the exception of constitutional (p=0.02) and genitourinary symptoms (p=0.04). 2) MCAS: 15 patients The median total symptom score was 127 (range 2-248). The normalized median score for individual symptom categories in order of severity was neuropsychological 4.5, musculoskeletal 4.2, cutaneous 4.0, constitutional 3.3, gastrointestinal 2.1, respiratory and cardiovascular 2.0 each, genitourinary 1.7, and angioedema 1.0. The median (range) serum tryptase level at referral was 12.7 ng/mL (1.7-25.8); five patients (33%) had a baseline level >20 ng/mL. 3) Neither SM/MCAS: 10 patients The median total symptom score was 119 (range 45-177). The normalized median score for individual symptom categories in order of severity was musculoskeletal 4.2, gastrointestinal 3.6, constitutional 3.3, neuropsychological 3.3, cutaneous 3.0, cardiovascular and genitourinary 2.0 each, respiratory 1.3, and angioedema 0. The median (range) serum tryptase level at referral (n=9) was 4.8 ng/mL (2.9-6.6). 4) Comparison: MCAS vs. SM: Symptom scores were significantly higher in MCAS as compared to SM (p<0.05), except for genitourinary and respiratory symptoms, which were not significantly different. ‘Neither SM/MCAS’ vs. SM: Symptom scores (total, gastrointestinal, constitutional, musculoskeletal, cutaneous, and neuropsychological) were significantly higher in the former group (p<0.05). Other symptom scores were not significantly different. Conclusions: The spectrum and severity of patient reported symptoms was broadly similar among WHO subcategories of SM, and serum tryptase level had limited if any correlation with symptom scores. Despite the significantly higher overall symptom burden in MCAS versus SM, tryptase levels in the former group were significantly lower with values >30 ng/mL unusual. Despite overlap, the top ranked symptoms in the 3 groups were different. Disclosures No relevant conflicts of interest to declare.

Abstract Background While unfavorable karyotype at referral is associated with significantly inferior overall and leukemia-free survival in myelofibrosis (MF) patients (Blood. 2011 Oct 27;118(17):4595), the incidence of clonal evolution during JAK inhibitor (JAKi) treatment and its clinical significance are not currently known. We conducted a sponsor-independent, single-center retrospective analysis examining the phenotypic correlates and prognostic impact of clonal evolution during JAKi treatment. Methods Clinical, cytogenetic and molecular data were collected on MF patients treated with one or more JAKi on a clinical trial at the Mayo Clinic, Rochester, MN. Baseline data pertained to the onset of treatment with first JAKi. Karyotype risk categories were as previously defined (Blood. 2011 Oct 27;118(17):4595). Serial bone marrow biopsies were obtained at varying frequencies based on individual JAKi protocol requirements. Mutation screening was performed as previously described (Leukemia. 2013 Apr 26. doi: 10.1038/leu.2013.119). Information on survival and leukemic transformation was updated in July 2013. Results A total of 157 MF patients were studied (60% male; median age 65 years, range 34-89 years). The DIPSS-plus distribution was: Low/Int-1 20 (13%), Int-2 66 (42%), and High 71 (45%). The first JAKi was momelotinib (CYT387) in 79 patients (50%), ruxolitinib in 51 (33%) and fedratinib (SAR302503) in 27 (17%). Median follow up from first JAKi treatment was 30 months (range 1-67 months); during this period, 72 deaths (46%) and 14 (9%) leukemic transformations were documented. Eighty nine patients (57%) had a median total 3 (range 2-8) bone marrow biopsies with karyotype analysis during JAKi treatment. Of these, 21 patients (24%) showed clonal evolution (ie, acquisition or loss of one or more chromosome abnormalities when comparing last observed karyotype during JAKi treatment to baseline). Overall, 13 patients (15%) had upstaging of karyotype risk category (eg, normal to unfavorable), 9 (10%) had downstaging (eg, favorable to normal) and 67 (75%) had no change. Acquisition of worse-than-baseline karyotype was significantly higher in DIPSS-plus high-risk patients (26%) versus non-high risk patients (6%) (p=0.03). There was no association between acquisition of a worse karyotype category and baseline karyotype risk category or ASXL1 or SRSF2 mutation status. There was borderline association with RBC transfusion-dependence and constitutional symptoms at baseline (p=0.06). There was no relationship between clonal evolution and achievement of spleen or anemia response during JAKi treatment (p>0.05). The median overall survival of the entire cohort was 41 months. On univariate analysis, overall survival was significantly worse in patients who acquired a worse-than-baseline karyotype risk category during JAKi treatment (n=13, 77% deaths, median survival=31 months) versus those who did not (n=76, 43% deaths, median survival=52 months) (p=0.01) (Figure). On multivariate analysis, the prognostic significance of acquiring a worse karyotype risk category was maintained against all individual DIPSS-plus prognostic variables, including baseline karyotype risk category, except age >65 years. On univariate analysis, leukemia-free survival was significantly worse in patients who acquired a worse-than-baseline karyotype risk category during JAKi treatment (n=13, 31% leukemic transformation, median leukemia-free survival=32 months) versus those who did not (n=76, 8% leukemic transformation, median leukemia-free survival not reached) (p=0.0006) (Figure). On multivariate analysis against known predictors of leukemic risk in PMF patients (ie, baseline unfavorable karyotype, SRSF1 mutated status and platelet count <100 x 109/L), only acquisition of a worse-than-baseline karyotype risk category maintained its prognostic value (HR 5.3, p=0.03) Conclusions This is the first study to examine the incidence of clonal evolution during JAKi treatment in MF patients. Approximately 25% of patients exhibited clonal evolution; acquisition of a worse-than-baseline karyotype risk category had a strong and independent association with inferior leukemia-free survival. A similar association was also observed for inferior overall survival, albeit not independent of older age. In contrast, there was no association with spleen or anemia response during JAKi treatment. Disclosures: Pardanani: Bristol Myers Squibb: Clinical trial support Other; Sanofi: Clinical trial support. Publication support service., Clinical trial support. Publication support service. Other; PharmaMar: Clinical trial support, Clinical trial support Other; JW Pharmaceutical Corp.: Clinical trial support, Clinical trial support Other.

Abstract Background Recent studies have suggested that increased circulating free light chains, inflammatory cytokines, hepcidin, ferritin, and ASXL1 mutated status have independent prognostic value for survival in primary myelofibrosis (PMF). In the current retrospective study, we studied all the aforementioned variables in the context of DIPSS-plus to examine their relative prognostic contributions for overall and leukemia-free survival. Methods The diagnosis of PMF was according to WHO criteria. The study population included all consecutive referrals to the Mayo Clinic, Rochester, MN where complete information on clinical and laboratory parameters and bone marrow karyotype was available. Inclusion to the study required availability of a research blood sample collected at referral. Levels of circulating free light chains (FLC) (J Clin Oncol. 2012 Apr 1;30(10):1087), inflammatory cytokines (J Clin Oncol. 2011 Apr 1;29(10):1356), hepcidin and ferritin (Am J Hematol. 2013 Apr;88(4):312) were determined as previously described. Disease-relevant mutations (ASXL1, SRSF2, EZH2, IDH-1/2, SF3B1, JAK2V617F and MPLW515) were identified as previously described (Leukemia. 2013 Apr 26. doi: 10.1038/leu.2013.119). Results A total of 224 PMF patients were studied (66% male; median age 63 years, range 18-83 years). The DIPSS-plus distribution was: Low 23 (10%), Int-1 26 (12%), Int-2 98 (44%), and High 77 (34%). Clinical characteristics were: unfavorable karyotype 13%, hemoglobin <10 g/dL 58%, leukocyte count >25 x 109/L 13%, platelet count <100 x 109/L 20%, peripheral blasts ≥1% 62%, red blood cell transfusion-dependent 38%, and constitutional symptoms 36%. Mutation frequencies were: JAK2V617F 61% (n=220), MPLW515 6% (n=204), ASXL1 34% (n=154), SRSF2 16% (n=189), IDH-1/2 3% (n=209), EZH2 1.5% (n=134), SF3B1 5% (n=91) and SETBP1 4% (n=114). Distribution of circulating biomarkers was: FLC >receiver operating characteristic (ROC) cutoff of 3.78 mg/dL 37% (n=222), interleukin (IL)-2R and/or IL-8 >3 standard deviations above normal mean (SD) 75% (n=197), ferritin ≥1000 mcg/L 18% (n=146), ferritin ≥500 30% (n=146), and hepcidin >3SD 72% (n=203). Median follow up from the time of referral was 45 months (range 1-317 months); during this period, 139 deaths (62%) and 27 (12%) leukemic transformations have been documented. The median overall survival of the entire cohort was 61 months. The following variables had DIPSS-plus independent predictive value for inferior survival: ferritin ≥1000 mcg/L (HR 1.9), ASXL1 mutated status (HR 1.7) and FLC >ROC cutoff (HR 2.0) and IL-2R and/or IL-8 >3SD (HR 1.6) (all p<0.05). When the aforementioned variables were added to the multivariate model (sequentially or altogether), only serum ferritin >1000 mcg/L retained its significance for overall survival independent of DIPSS-plus (HR 2.1; p=0.03). The predictive significance for increased ferritin level was maintained in RBC transfusion-dependent (ferritin ≥1000 mcg/L; n=26/54; median survival 21 versus 59 months; p=0.03) and -independent (ferritin >500 mcg/L; n=5/92; median survival 20 versus 80 months; p=0.0002) patients. Multivariable analysis identified the following predictors for inferior leukemia-free survival: SRSF2 mutated status (HR 4.8), unfavorable karyotype (HR 4.0), and circulating blasts ≥1% (HR 3.0) (p<0.05). Conclusions When considering composite risk-assessment in PMF where input variables were disease-relevant mutations and circulating biomarkers in addition to traditional clinical parameters, only increased serum ferritin levels at time-of-referral retained adverse predictive value for overall survival independent of DIPSS-plus. The prognostic value of serum ferritin was independent of anemia and RBC transfusion need. It appears to more fully capture the severity of the underlying erythropoietic defect in PMF by also likely reflecting (as an acute-phase reactant) the marrow-suppressive effect of disease-related inflammation. The shortened survival in patients with increased ferritin levels was unrelated to iron overload since none of the deaths, where information was available, were caused by cardiac siderosis. Serum ferritin levels were not associated with leukemic transformation risk. In the latter analysis, only SRSF2 mutations, unfavorable karyotype and presence of circulating blasts were independently associated with inferior leukemia-free survival. Disclosures: No relevant conflicts of interest to declare.

Abstract Background: KIT D816V is considered the driver mutation in systemic mastocytosis (SM) however this mutation alone does not explain the diverse clinical manifestations of SM. While mutations in other myeloid-relevant genes have been reported in SM, their pattern(s) of co-segregation and prognostic value, independent of age and SM subtype, have not been fully defined in a mature dataset. Objectives: In this pilot study of advanced SM patients, we sequenced a panel of myeloid-relevant genes for known pathogenic mutations, to ascertain: (i) the frequency of individual mutations; (ii) the pattern(s) of mutation co-segregation; and (iii) the prognostic value of mutations, both individually and in combination, on overall- (OS) and leukemia-free survival (LFS). Methods: The current study was approved by the Mayo Clinic institutional review board. SM was classified as per World Health Organization criteria. DNA was isolated from archived bone marrow (BM) cell pellets. Next-generation deep sequencing by HiSeq SBS chemistry (Illumina) was performed to investigate the coding regions of 22 genes: KIT, JAK2, CALR, SRSF2, U2AF1, SF3B1, ASXL1, TET2, EZH2, SETBP1, DNMT3A, IDH-1/2, SUZ12, CBL, NRAS, FLT3, PTPN11, RUNX1, CEBPA, TP53 and NPM1. Results: We studied 19 patients with advanced SM; 6 had aggressive SM (ASM) and 13 had SM with an associated hematological disease (SM-AHD). Of the latter, 5 patients (38%) had myeloproliferative neoplasm-unclassified (MPN-u), 3 (23%) chronic myelomonocytic leukemia (CMML), 2 (15%) acute myeloid leukemia (AML), and 1 (8%) each polycythemia vera, myelodysplastic syndrome, and multiple myeloma. The median follow up from diagnosis was 20 months (range 2 to 84). Over this period, 5 patients (26%) developed leukemic transformation and 12 patients (63%) have died. KIT D816V was identified in 9 (47%) patients; 9 of 10 patients who tested negative by deep sequencing were screened by allele-specific PCR (sensitivity ~0.01%), with 8 additional patients testing positive. Thus, overall KIT D816V frequency was 89%. Fourteen (74%) patients harbored at least one additional non-KIT mutation; of these 7 patients had one additional mutation (ASXL1/TET2/SF3B1 = 2 each and JAK2 =1), 3 patients each had two and three additional mutations, and 1 patient had 4 additional mutations. The most frequently mutated genes (other than KIT) were ASXL1/TET2 (5 patients each, 26%), CBL (4 patients, 21%), SETBP1/SF3B1/DNMT3A (2 patients each, 11%) and JAK2/CALR/FLT3/IDH-1/RUNX1/TP53 (1 patient each, 5%). There was no overlap between patients harboring TET2 and ASXL1 mutations however 2 and 1 CBL-mutated patients concurrently harbored TET2 and ASXL1 mutations, respectively. SETBP1 and SF3B1 but not DNMT3A mutations occurred independently of TET2 and ASXL1 mutations. The distribution of mutations was similar between ASM and SM-AHD subgroups. When considered individually, the following non-KIT mutated genes (present in at least 2 patients) were associated with significantly inferior OS: ASXL1, CBL and SETBP1 (p<0.05). When the 3 mutated genes were considered together, only ASXL1 and CBL maintained their significance, independent of age and SM subtype, for inferior OS (Hazard ratio (95% confidence interval)=34.8 (3.1-393.9) and 59.7 (4.1-861.5), respectively). Patients harboring ASXL1 and/or CBL mutations (n=8, 8 deaths, median OS=11 months) had a significantly worse OS as compared to those without either mutation (n=11, 4 deaths, median OS=84 months) (p=0.0002) (Fig 1). When considering the number of non-KIT mutations (zero, one, two, three and four mutations in 5, 7, 3, 3 and 1 patients, respectively), the group with ≥3 mutations (n=4, 4 deaths, median OS=7 months) had a significantly inferior OS as compared to those with <3 mutations (n=15, 8 deaths, median OS=48 months) (p=0.01) (Fig 2). Presence of mutations was not correlated with LFS in this analysis. Conclusions: In this cohort of advanced SM patients, non-KIT mutations were frequent (prevalence 74%). TET2, ASXL1, SETBP1 and SF3B1, but not CBL or DNMT3A, mutations were mutually exclusive. Presence of ASXL1 and CBL mutations was associated with significantly inferior OS (HR=35 and 60, respectively), independent of known prognostic factors. An increasing number of non-KIT mutations (≥3, HR=5.9) was also associated with a significantly worse survival outcome. Sequencing results from a larger cohort will be presented at the meeting. Figure 1. Figure 1. Figure 2. Figure 2. Disclosures Pardanani: Stemline: 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.

Abstract Background: CD123 is the α-subunit of the high-affinity receptor for interleukin-3; its expression in normal bone marrow (BM) is highly restricted, however CD123 is highly expressed in certain hematolymphoid malignancies. In a pilot study of 11 systemic mastocytosis (SM) patients (Lasho et al., Leukemia, 2015), we made the following novel observations (i) CD123 was aberrantly expressed on neoplastic mast cells (MC); and (ii) there was focal proliferation of plasmacytoid dendritic cells (PDC) around MC aggregates, suggesting a tumor promoting role for PDC. Objectives: To study MC CD123 expression by IHC in a larger cohort of SM patients to ascertain: (i) whether there is a significant difference in CD123 expression between SM subtypes; (ii) whether focal PDC proliferation around MC aggregates is correlated with CD123 expression; and (iii) whether CD123 expression has prognostic value for overall survival (OS). Methods: The current study was approved by the Mayo Clinic institutional review board. SM was classified as per standard criteria. Archived BM slides were stained for tryptase and CD123 as previously described (Lasho et al., Leukemia, 2015). Slides were reviewed independently by 2 hematopathologists who were blinded with regards to SM subgroups and scored on the following pre-defined parameters: (i) CD123 expression yes/no; (ii) CD123 expression strong/weak; (iii) focal PDC proliferation yes/no; and (iv) BM MC%. Results: We studied 58 SM patients and 3 controls. Of the former, 23 had indolent SM (ISM), 10 aggressive SM (ASM), 23 SM with associated hematological disease (SM-AHD), and 2 had mast cell leukemia (MCL). Of the SM-AHD patients, 10 (43%) had CMML, 5 (22%) myeloproliferative neoplasm-unclassified (MPN-u), 3 (13%) PV, 2 (9%) acute myeloid leukemia, and 1 each had lymphoma, myeloma and myelodysplastic syndrome. The median follow up from diagnosis was 32 months (range 0.1 to 162). Over this period, 3 patients (5%) had leukemic transformation and 30 patients (52%) died. Concordance rates between hematopathologists for CD123 positive/negative, CD123 strong/weak, focal PDC proliferation yes/no and MC% were 97%, 94%, 98% and 100%, respectively. MC CD123 expression was absent in control cases but demonstrable in 37 (64%) SM patients; expression rates were 100%, 61%, 57%, and 0% in ASM, ISM, SM-AHD and MCL, respectively (p=0.02). Similar to MCL, both cases with SM-AML showed absent MC CD123 expression. Strong MC CD123 expression (comparable to background interstitial PDC) was observed in 23 patients (62%), including 85% with SM-AHD, 60% with ASM, and 43% with ISM (p=0.08). Focal PDC proliferation around MC aggregates, regardless of CD123 expression status, was noted in 44 patients (76%), including 90% with ASM, 87% with ISM, 65% with SM-AHD and 0% with MCL (p=0.02). Focal PDC proliferation was significantly higher in CD123-positive versus -negative patients (87% versus 50%, p=0.005). OS was predicted by SM subtype; the median OS for ISM, ASM, SM-AHD and MCL patients was not reached, 30 months, 25 months and 3 months, respectively (p=0.005). CD123 expression status did not have prognostic value for OS overall, however, in SM-AHD patients, CD123 expression was associated with significantly inferior survival (p=0.04), independent of the associated disease (ie, CMML vs AML vs MPN vs other). Survival outcome of SM-CMML patients expressing MC CD123 (n=3, median OS=11 months) was significantly inferior as compared to patients who did not (n=7, median OS=44 months), independent of age and absolute monocyte count (p=0.01). CD123 staining intensity had borderline significance for OS in the overall cohort (p=0.08). When restricted to non-indolent SM cases, strong CD123 expression was associated with significantly worse overall survival (15 versus 88 months, p=0.04). Conclusions: In this cohort, aberrant MC CD123 expression was observed in the majority of SM patients with highest prevalence in ASM patients and uniformly absent expression in leukemic phase SM (MCL or SM-AML). Focal PDC proliferation around MC aggregates was significantly higher in CD123-positive cases, indicating a potential functional interaction. CD123 expression identified SM-AHD patients with inferior OS, especially those with SM-CMML. Strong CD123 staining intensity may be associated with inferior OS in non-indolent SM patients. CD123 expression on MC and PDC constitutes a novel therapeutic target in non-leukemic SM. Disclosures Pardanani: Stemline: Research Funding. Brooks:Stemline Therapeutics, Inc.: Employment, Equity Ownership, Patents & Royalties.

Abstract Background The impact of JAK inhibitor (JAKi) therapy on the natural history of myelofibrosis remains unclear. While a Phase 3 study showed that overall survival of ruxolitinib-treated intermediate-2 or high-risk myelofibrosis patients was superior as compared to placebo-treated patients, it remains unclear whether such an advantage would persist in patients receiving standard therapy, and whether this result is generalizable to other JAK inhibitors. We conducted a sponsor-independent, single-center retrospective analysis of overall and leukemia-free survival after long-term follow up in patients receiving JAKi treatment with comparison to two control populations: (i) a contemporaneously diagnosed (2005 onwards) primary myelofibrosis (PMF) patient cohort receiving standard therapy (JAKi and pomalidomide naïve); and (ii) a pomalidomide treated patient cohort (JAKi-naïve). Methods Baseline clinical, cytogenetic and molecular data were collected at the onset of study treatment with the first JAKi or pomalidomide, or at the time of first referral for patients receiving standard therapy. Information regarding bone marrow karyotype and DIPSS-plus risk status was available for all patients. Information on survival and leukemic transformation was updated in July 2013. Results The 3 patient groups were: (i) JAKi-treated: n=157, median age 65 years, range 34-89. DIPSS-plus risk: Low/Int-1 20 (13%), Int-2 66 (42%), and High 71 (45%). Median follow up from first JAKi treatment was 30 months (range 1-67 months); during this period, 72 deaths (46%) and 14 (9%) leukemic transformations were documented. The first JAKi was ruxolitinib in 51 patients (33%), momelotinib (CYT387) in 79 (50%), and fedratinib (SAR302503) in 27 (17%). The proportion of patient deaths and leukemic transformation (median follow up, range) per specific JAKi was: ruxolitinib 57% and 12% (40 months, 2-67), momelotinib 43% and 9% (29 months, 1-42), and fedratinib 33% and 4% (21 months, 2-53), respectively. (ii) Control#1 (Pomalidomide-treated): n=69, median age 67 years, range 36-87. DIPSS-plus risk: Low/Int-1 0 (0%), Int-2 28 (41%), and High 41 (59%). Median follow up was 25 months (range 2-70 months); during this period, 47 deaths (68%) and 7 (10%) leukemic transformations were documented. (iii) Control# 2 (Standard therapy): n=319, median age 66 years, range 22-90. DIPSS-plus risk: Low/Int-1 98 (31%), Int-2 122 (38%), and High 99 (31%). Median follow up from time of referral was 18 months (range 1-92 months); during this period, 101 deaths (32%) and 18 (6%) leukemic transformations were documented. For patients with Int-2 or high-risk disease (n=221), 92 deaths (42%) and 13 (6%) leukemic transformations were recorded (median follow up 16 months, range 1-92). The survival analysis focused on DIPSS-plus Int-2 and high-risk patients for all groups, reflecting the population predominantly selected for treatment on JAKi clinical trials. There was no significant difference in the median overall survival of myelofibrosis patients treated with JAKi (39 months) versus standard therapy (35 months) versus pomalidomide (26 months) (p=0.12) (Figure). The 5-year survival rates were 31%, 33% and 26%, respectively. Similarly, the median overall survival of patients treated with ruxolitinib (35 months), momelotinib (37 months) or fedratinib (42 months) was not significantly different (p=0.4). Baseline DIPSS-plus status (ie, Int-2 vs. high-risk) effectively stratified JAKi treated patients in terms of overall survival (median survival 31 vs. 60 months; p=0.0002). There was no significant difference in leukemia-free survival when comparing JAKi-treated patients versus standard therapy verus pomalidomide-treated patients (p=0.6) (Figure). The estimated 5-year risk of leukemic transformation was 17%, 12% and 13%, respectively. Conclusions With long-term follow up, myelofibrosis patients receiving JAKi therapy exhibited similar overall and leukemia-free survival as compared to two control populations (DIPSS-plus matched standard therapy and pomalidomide-treated patients). Baseline DIPSS-plus status was a powerful predictor of overall survival in JAKi treated patients. While underscoring the limitation of a non-head-to-head retrospective comparison, there was no significant difference in overall or leukemia-free survival when comparing individual JAKi drugs. Disclosures: Pardanani: Bristol Myers Squibb: Clinical trial support Other; Sanofi: Clinical trial support, Publication support services, Clinical trial support, Publication support services Other; PharmaMar: Clinical trial support, Clinical trial support Other; JW Pharmaceutical Corp.: Clinical trial support, Clinical trial support Other. Off Label Use: Use of Ruxolitinib, Momelotinib, Fedratinib and Pomalidomide for treatment of Myelofibrosis in Clinical Trial setting.

Abstract Background JAK inhibitors (JAKi) currently represent a frontline treatment modality in patients with symptomatic intermediate- or high-risk myelofibrosis (MF). While the efficacy of JAKi in decreasing spleen size and improving disease-related symptoms is well documented, the effect of this drug class on overall survival and risk of leukemic transformation in MF patients is less well understood, primarily due to short follow up in individual patient cohorts. Furthermore, there is scant information on baseline predictors of overall and leukemia-free survival, and also spleen and/or anemia responses, at the onset of JAKi therapy. We conducted a sponsor-independent single-center retrospective review of patients treated with JAKi with long follow up to address the aforementioned issues. Here, we report our findings regarding baseline predictors of clinical outcome and treatment response in MF patients treated with JAKi. Methods Clinical, cytogenetic and molecular data were retrospectively collected on patients treated with one or more JAKi on a clinical trial at the Mayo Clinic, Rochester, MN. Baseline clinical data pertained to the onset of treatment with the first JAKi. Karyotype information was available for all patients. Screening for JAK2V617F, MPLW515, ASXL1, and SRSF2 mutations was performed as previously described (Leukemia. 2013 Apr 26. doi: 10.1038/leu.2013.119). Spleen size was measured by palpation by clinical investigators. Anemia and spleen responses were adjudicated as per IWG criteria (Tefferi, Blood, 2006). Information on survival and leukemic transformation was updated in July 2013. Results A total of 157 MF patients were studied (60% male; median age 65 years, range 34-89 years). Ninety seven patients (62%) had primary MF, 42 (27%) post-polycythemia vera MF, and 18 (11%) post-essential thrombocythemia MF. The DIPSS-plus distribution was: Low/Int-1 20 (13%), Int-2 66 (42%), and High 71 (45%). Other characteristics were: JAK2V617F positive 78%, unfavorable karyotype 17%, hemoglobin <10 g/dL 58%, leukocyte count >25 x 109/L 31%, platelet count <100 x 109/L 15%, peripheral blasts ≥1% 69%, red blood cell transfusion-dependent 37%, and constitutional symptoms 56%. Forty one patients (38%) were ASXL1 mutated (n=108) and 20 (18%) SRSF2 mutated (n=110). One hundred and thirty nine patients (89%) were evaluable for spleen response (median spleen size by palpation 19 cm, range 6-32 cm) and 91 (58%) for anemia response by IWG criteria. The first JAKi was momelotinib (CYT387) in 79 patients (50%), ruxolitinib in 51 (33%) and fedratinib (SAR302503) in 27 (17%). Median follow up from first JAKi treatment was 30 months (range 1-67 months); during this period, 72 deaths (46%) and 14 (9%) leukemic transformations have been documented. The median overall survival of the entire cohort was 41 months. Multivariable analysis identified the following DIPSS-plus independent predictors for survival: palpable spleen size >20 cm (HR 2.5), ASXL1 mutated status (HR 3.1) and SRSF2 mutated status (HR 3.8) (all p<0.01) (Figure). In contrast, there was no difference in survival with regards to the first JAKi used for MF treatment (p=0.3). Multivariable analysis identified the following predictors for leukemia-free survival: SRSF2 mutated (HR 9.7), unfavorable karyotype (HR 8.7), and palpable spleen size >20 cm (HR 9.1) (all p<0.01). Predictors of spleen response included baseline spleen size (≤20 cm 56%, >20 cm 34%; p=0.01), with borderline significance for ASXL1 mutation status (unmutated 51%, mutated 31%; p=0.06). Predictors of anemia response included RBC transfusion status at baseline (transfusion dependent 38%, transfusion independent 12%; p<0.01) and JAK2V617F status (unmutated 46%, mutated 22%; p=0.02). Conclusions Larger baseline spleen size and ASXL1 and SRSF2 mutated status predicted for inferior overall survival, independent of DIPSS-plus, at the onset of first JAKi treatment in MF patients. Similarly, multivariable analysis identified larger baseline spleen size and presence of unfavorable karyotype and SRSF2 mutations as being predictive for inferior leukemia-free survival. Spleen response rates were significantly superior in patients with smaller baseline spleen size and possibly ASXL1 unmutated status. Anemia response rates were significantly higher in patients who were transfusion-dependent at baseline and had JAK2V617F unmutated status. Disclosures: Pardanani: Bristol Myers Squibb: Clinical trial support Other; Sanofi: Clinical trial support, Publication support services, Clinical trial support, Publication support services Other; PharmaMar: Clinical trial support, Clinical trial support Other; JW Pharmaceutical Corp.: Clinical trial support, Clinical trial support Other. Off Label Use: Use of Ruxolitinib, Momelotinib, Fedratinib and Pomalidomide for treatment of Myelofibrosis in Clinical Trial setting.

Abstract Background : Momelotinib (a JAK1 and JAK2 inhibitor) induces both anemia and spleen response in patients with myelofibrosis (MF) (Leukemia 2013;27:1322). The favorable effect on anemia was a distinguishing feature for momelotinib, compared to other JAK inhibitors, but the drug was also associated with treatment-emergent peripheral neuropathy (TE-PN). We examined the natural history and risk factors of momelotinib-associated peripheral neuropathy. Methods : The study patients constitute part of a larger phase-1/2 clinical trial (CCL09101; NCT00935987) using momelotinib for the treatment MF. Toxicity grading was according to the Common Terminology Criteria for Adverse Events (CTCAE) v.4.03. Momelotinib capsules (as opposed to the newer tablet formulation used in the currently ongoing phase-3 study) were used in the current study, which represents a sponsor-independent analysis. 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. DIPSS-plus (JCO. 2011;29:392) risk distribution was 63% high, 36% intermediate-2 and 1% intermediate-1. 75% of the patients harbored JAK2V617F and 50% abnormal karyotype. Previous treatment included other JAK inhibitors in 21 patients, thalidomide/lenalidomide/pomalidomide in 31 and hydroxyurea or other cytoreductive agents in 55. History of diabetes was documented in 7% of the patients at baseline and 14 (14%) of the patients had symptoms of PN before starting treatment with momelotinib, all of which were grade-1. Momelotinib was initiated at 100 mg/day in 3 patients, 150 mg/day in 21, 150 mg twice-daily in 20, 200 mg/day in 3, 300 mg/day in 47 and 400 mg/day in 6. The maximum momelotinib dose was 150 mg/day in 6 patients, 150 mg twice-daily in 20, 300 mg/day in 68 and 400 mg/day in 6. Treatment duration was <6 months in 12 patients, 6-12 months in 22, 12-24 months in 19 and >24 months in 47. Median follow-up after the institution of protocol drug therapy was 35 months (range 1-49). During this period, TE-PN was documented in 44 (44%) patients; of these, 42 were in patients without baseline neuropathy. TE-PN involved the feet only in 28 patients, hands only in one patient and both feet and hands in 15 patients. Median (range) for the time of onset of TE-PN was 32 weeks (1-132) and duration of TE-PN 11 months (0-40). All 42 newly-emergent PN were grade-1 sensory while the two patients with grade-1 baseline PN progressed to grade-2. Formal neurological evaluation, which was performed in 9 patients, mostly showed length-dependent sensory-motor large and small fiber neuropathy with axonal features. TE-PN resulted in drug discontinuation in 7 patients and reduction in drug dose in 28 patients. Improvement after drug dose reduction was documented in only one patient and in none of those with drug discontinuation. Progression to grade-2 PN was documented in 3 patients. TE- PN was significantly associated with clinical improvement (CI) with 54% incidence in responders vs 30% in non-responders (p=0.02); however, longer treatment duration was also associated with higher prevalence of TE-PN (p=0.03). In univariate analysis, patients with TE-PN lived longer than those without TE-PN (p=0.048); however, significance was lost during multivariable analysis that included either achievement of CI or treatment duration. Neither the initial (p=0.53) nor maximum (p=0.37) momelotinib dose was correlated with TE-PN, which was also not influenced by JAK2V617F (p>0.99), karyotype (p=0.26), history of diabetes (p=0.39) or previous treatment with JAK inhibitor therapy (p=0.7), thalidomide (p=0.24), lenalidomide (p=0.59), pomalidomide (p=0.63) or hydroxyurea (p=0.56). There were no correlations between TE-PN and age (p=0.37), sex (p=0.37), type of MF (p=0.98), DIPSS-plus score (p=0.07), baseline transfusion dependency (p=0.15), constitutional symptoms (p=0.83) or spleen size (p=0.53). TE-PN did not correlate with hematologic (p=0.14) or extramedullary toxicity other than PN (p=0.41) or lipase/amylase abnormalities (p=0.35). Conclusions : Momelotinib-associated neuropathy in MF might not be reversible in the majority of cases but also does not appear to be progressive. We were not able to identify risk factors for TE-PN, other than duration of treatment, which also explains its apparent association with response/survival. We are currently looking into possible correlations with serum thiamine levels. Disclosures No relevant conflicts of interest to declare.