Abstract: Introduction. Blast phase (BP) is the terminal and most incurable phase of myelofibrosis (MF) and occurs in a not negligible fraction of patients (pts). In the pre-ruxolitinib (RUX) era, peripheral blasts, thrombocytopenia, unfavorable cytogenetics, and high risk category were identified as predictors of BP. RUX is the standard of care for symptomatic MF; however, information on clinical/laboratory correlates of BP in RUX-treated pts is not available. Aims. The primary objective of the study is to assess real-world data on incidence, risk factors and outcome of BP in RUX-treated MF pts. Methods. A multicentre observational retrospective study on RUX-treated MF pts was conducted in 20 European Hematology Centers. Data were extracted from an electronic database that included consecutive pts treated with RUX from June 2011. Data cut-off was June 2019. Risk category was assessed at RUX start according to the Dynamic International Prognostic Score System (DIPSS) or the Myelofibrosis Secondary to PV and ET Collaboration Prognostic Model (MYSEC-PM) in pts with post-Polycythemia Vera (PV)/post-Essential Thrombocythemia (ET) MF (secondary MF, SMF). A time-to-event (BP) analysis was conducted with Fine & Gray model with death/time of stem cell transplant as competing risks. Variables tested for association with BP were: age≥65yr, sex, transfusion-dependency, PLT 〈 150x109/l, peripheral blasts ≥3%, marrow fibrosis grade, CALR-unmutated genotype, unfavorable karyotype, spleen length (≥10 cm), total symptoms score (≥20), previous hydroxyurea (HU), alkylating agents, and interferon (IFN) use, time from MF diagnosis to RUX start, and PV/ET duration. Cumulative Incidence Function among risk categories for DIPSS and MYSEC-PM was calculated applying the Gray's model. Results . Overall, 589 MF pts were included and observed for 1833 pt-yrs from RUX start (median, 35.4 mos). Diagnosis was PMF in 304 pts (51.6%), PPV-MF in 164 pts (27.8%) or PET-MF in 121 (20.6%); 58.4% males. Molecular status was: JAK2V617F (82.5%), CALR (11.3%) and MPLW515K/L (1.1%); 5.1% were triple negatives. Overall, 368 (62.5%) pts received ≥1 cytoreductive therapy before RUX, specifically: HU, n. 357; alkylating agents, n. 47; anagrelide, n. 33; and IFN, n. 29. Median time from MF diagnosis to RUX start was 1.3 yrs. DIPSS for the whole cohort was: INT-1 (52.9%), INT-2 (40.1%), and HIGH (7%). DIPSS distribution in PMF pts was: INT-1 (47.8%), INT-2 (45.7%), and HIGH (6.5%), while SMF pts were categorized at LOW (11.1%), INT-1 (43.1%), INT-2 (31.2%) and HIGH (14.6%) risk according to the MYSEC-PM. Overall, 65 (11%) developed BP. In 61 pts, BP caused RUX withdrawal after a median time of 1.2 yrs (0.7-6.2); in 4 pts BP occurred after RUX stop (median time: 2.4 yrs). BP incidence rate was 3.6 x100 pt-yrs and was comparable in PMF and SMF (p=0.1). In univariate analysis, the probability of BP evolution for the PMF cohort was significantly reduced by previous IFN use (p=0.001). In SMF, predictors for BP in univariate analysis were PLT 〈 150 x109/l (p=0.001), blasts ≥3% (p=0.002), grade 3 marrow fibrosis (p=0.03) and PV/ET duration ≥ 10 yrs (p=0.02); previous IFN significantly reduced the risk of BP (p=0.02). In multivariable analysis, PLT 〈 150 x109/l (HR 2.4, 95% CI 1.1-5.4, p=0.03), blasts ≥3% (HR 3.3, 95% CI 1.4-7.5, p=0.004) and previous IFN (HR 0.1, 95% CI 0.02-0.8, p=0.04) remained significant. High DIPSS risk significantly predicted BP in PMF (p=0.04, HR [95% CI]: 2.6 [1.1-6.5] ) but not in SMF (p=0.40). In this latter cohort, only the MYSEC-PM was associated with BP (p=0.02, HR 1.7 [95% CI]: [1.1-2.8] ) (Fig.1). Estimated HRs, in reference to the lower score category, were: 1.10 for INT-1, 1.82 for INT-2, and 4.04 for HIGH risk. HR for HIGH risk, comparing to all lower risk groups, was 3.53 (95% CI: 1.53-8.11). Overall, 54 (81.8%) BP pts died and median survival was 2.8 mos. Survival after BP was not influenced by type of MF, previous response to RUX, and type of salvage treatment. Conclusions. Thrombocytopenia and peripheral blasts at RUX start identified pts at higher risk of BP in SMF, while previous IFN use was associated with reduced BP evolution in both PMF and SMF, suggesting a possible disease-modifying action of this agent. Also, this analysis supports the ability of MYSEC-PM in predicting BP in pts with SMF. Despite RUX use, outcome after BP remained dismal, confirming the need for newer treatment strategies. Disclosures Palandri: Novartis: Consultancy, Honoraria. Breccia:Incyte: Honoraria; Celgene: Honoraria; Novartis: Honoraria; Pfizer: Honoraria; BMS: Honoraria. Tiribelli:Incyte: Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees. Benevolo:Novartis Pharmaceuticals: Consultancy. Bonifacio:Novartis: Honoraria; Amgen: Honoraria; Pfizer: Honoraria; Incyte: Honoraria; BMS: Honoraria. Iurlo:Pfizer: Honoraria; BMS: Honoraria; Incyte: Honoraria; Novartis: Honoraria. Elli:Novartis: Membership on an entity's Board of Directors or advisory committees. Abruzzese:BMS: Consultancy; Incyte: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Sgherza:Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Incyte: Honoraria. Cavazzini:Pfize: Honoraria; Incyte: Honoraria; Novartis: Honoraria. Crugnola:Novartis: Honoraria; Incyte: Honoraria. Isidori:Janssen: Honoraria; Novartis: Honoraria; Gilead: Honoraria. Heidel:Novartis: Consultancy, Research Funding; Celgene: Consultancy; CTI: Consultancy. Latagliata:Janssen: Honoraria; Novartis: Honoraria; Pfizer: Honoraria; Celgene: Honoraria. Trawinska:Novartis: Consultancy, Honoraria. Krampera:Janssen: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees. Cuneo:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Honoraria, Speakers Bureau; Abbvie: Honoraria, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Cavo:takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; AbbVie: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations, Speakers Bureau; janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel accommodations, Speakers Bureau; bms: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; novartis: Honoraria. Palumbo:Novartis: Honoraria; Janssen: Honoraria; Celgene: Honoraria; Amgen: Honoraria; Hospira: Honoraria; Teva: Honoraria.

Abstract: Introduction . The 2016 WHO criteria identified early primary myelofibrosis (early-PMF) as an individual entity with different clinical/laboratory presentations and a significantly better outcome compared to overt PMF. No information is available on the therapeutic effects of ruxolitinib (RUX) in the context of each disease separately. Aims . To report the differences between early and overt PMF patients (pts) treated with RUX in terms of baseline clinical/laboratory characteristics, response to treatment and toxicity. Methods . A clinical database was created in 23 European Hematology Centers including retrospective data of 537 MF pts treated with RUX from Jan 2011 to July 2018. Spleen and symptoms response (SR & SyR) to RUX were evaluated according to the 2013 IWG-MRT criteria. Hematologic toxicity and infections were graded according to the WHO scale. Overall survival (OS) and progression-free survival (PFS) were estimated from diagnosis using the Cox proportional hazards regression model, with adjustment for the dynamic international prognostic score system (DIPSS) and left-truncation. Results . A total of 199 pts had a diagnosis of early (n. 59, 29.7%) or overt (n. 140, 70.3%) PMF confirmed by bone marrow biopsy at RUX start and were included in this analysis. At RUX start, median age was 68.4 yrs (26.5-88.9) and 66.3% of pts had a spleen palpable at ≥10 cm below the left costal margin (LCM) (median spleen length: 12 cm). Median hemoglobin value and total symptoms score (TSS) were 10.5 g/dL and 20 (0-80), respectively. DIPSS distribution was: intermediate-1 (50.5%), intermediate-2 (42.1%), high (7.4%). Molecular status was: JAK2V617F 72.3%, CALR 13.7%, MPLW515K/L 3.1%, triple-negative 5%. Median time from diagnosis to RUX start was 22.4 mos (0.1-394). Compared to overt PMF pts, pts with early PMF started RUX with higher hemoglobin levels (median, 11.6 vs 10.4 g/dl, p=0.01) and lower circulating blast counts (p 〈 0.001), and were more frequently at intermediate-1 DIPSS risk (69.6% vs 42.5%, p 〈 0.001). RUX starting and 12-weeks titrated doses were comparable in the two groups. At 3 and 6 months, 43.1% and 48.9% of early-PMF pts achieved a SR, compared to 27.9% and 31.3% of overt-MF pts (p=0.04 and p=0.04, respectively). The rate of SyR was also higher in early-PMF pts at 3 months (82.5% vs 68.8%, p=0.05) and at 6 months (90.0 vs 73.7, p=0.02). In the first 12 months from RUX start, anemia/thrombocytopenia of all grades occurred in 75.6%/43.1% and 86.3%/60.0% of early and overt PMF pts, respectively (p=0.11 and p=0.03). At 3 months, anemia was more frequent in overt PMF pts (94.7% vs 80.0%, p=0.01), with 32.6% of pts having a grade 3-4 anemia compared to 17.8% in early PMF (p=0.02). The incidence of thrombocytopenia was also higher in overt PMF at 3 (51.5% vs 36.2%, p=0.05) and 6 (52.9% vs 35.8%, p=0.04) months, with only 2.2% and 2.5% of pts having a grade 3-4 thrombocytopenia, respectively. Seventy-five pts had at least one grade ≥2 infectious episode during RUX therapy. Considering death as competing risk, the cumulative risk of infections grade ≥2 was comparable in the two cohorts (p=0.4). Overall, 108 pts discontinued RUX (52.5% and 55.0% of early and overt PMF pts, p=0.7). Evolution into acute leukemia (AL) occurred in 21 pts. After a median follow-up of 23 months, 69 pts died (19 early), specifically because of progression of myelofibrosis (38%), AL (16.9%), infections (11.3%), hemorrhage/thrombosis (12.6%), second neoplasias (8.5%) or transplant-associated toxicity (2.8%), other causes (9.9%). OS (p=0.88) and PFS (p=0.86) were comparable in early and overt PMF pts. Conclusions . This study indicates for the first time that early PMF represents a category of pts that is projected to have better responses and lower toxicities from RUX treatmemt. In the setting of RUX therapy, a WHO-defined diagnosis may contribute to better identify pts who may deserve a strict monitoring during treatment. Disclosures Palandri: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Palumbo:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees. Abruzzese:BMS: Consultancy; Pfizer: Consultancy; Novartis: Consultancy; Ariad: Consultancy. Foà:INCYTE: Other: ADVISORY BOARD; GILEAD: Speakers Bureau; JANSSEN: Other: ADVISORY BOARD, Speakers Bureau; ROCHE: Other: ADVISORY BOARD, Speakers Bureau; CELTRION: Other: ADVISORY BOARD; ABBVIE: Other: ADVISORY BOARD, Speakers Bureau; AMGEN: Other: ADVISORY BOARD; NOVARTIS: Speakers Bureau; CELGENE: Other: ADVISORY BOARD, Speakers Bureau. Vitolo:Takeda: Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Speakers Bureau; Sandoz: Speakers Bureau. Aversa:Basilea: Honoraria, Membership on an entity's Board of Directors or advisory committees; Astellas: Honoraria; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees. Cuneo:Roche: Other: advisory board, Speakers Bureau; Abbvie: Other: advisory board, Speakers Bureau; Gilead: Other: advisory board, Speakers Bureau; janssen: Other: advisory board, Speakers Bureau. Di Raimondo:Celgene: Honoraria; Takeda: Honoraria, Research Funding. Cavo:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Breccia:Incyte: Honoraria; Pfizer: Honoraria; Novartis: Honoraria; BMS: Honoraria.

Abstract: The development of different generations of BCR-ABL1 tyrosine kinase inhibitors (TKIs) has led to the high overall survival of chronic myeloid leukemia (CML) patients. However, there are CML patients who show resistance to TKI therapy and are prone to progress to more advanced phases of the disease. So, implementing an alternative approach for targeting TKIs insensitive cells would be of the essence. Dihydroorotate dehydrogenase (DHODH) is an enzyme in the de novo pyrimidine biosynthesis pathway that is located in the inner membrane of mitochondria. Here, we found that CML cells are vulnerable to DHODH inhibition mediated by Meds433, a new and potent DHODH inhibitor recently developed by our group. Meds433 significantly activates the apoptotic pathway and leads to the reduction of amino acids and induction of huge metabolic stress in CML CD34+ cells. Altogether, our study shows that DHODH inhibition is a promising approach for targeting CML stem/progenitor cells and may help more patients discontinue the therapy.

Abstract: Introduction . Ruxolitinib (RUX) is the only targeted therapy available for the treatment of myelofibrosis (MF)-related splenomegaly and symptoms. Significant clinical responses may be achieved in around 50% of patients (pts). However, half of responding pts lose the response over time. Aims . To report the outcome of a large cohort of MF pts after RUX failure, in terms of disease status, treatment strategies and survival. Methods . A clinical database was created in 23 European Hematology Centers including retrospective data of 537 MF pts treated with RUX from Jan 2011 to July 2018. Updated information at the date of July 15th 2018 was available in 442 pts who were included in the present analysis. Spleen and symptoms response (SR & SyR) to RUX were evaluated according to the 2013 IWG-MRT criteria. RUX-related toxicity and infections were graded according to the WHO scale. Overall (OS) was estimated from the date of RUX discontinuation to the date of death or last contact, using the Kaplan-Meyer method (log-rank test). Results . After a median follow-up of 30.5 months (1.7-84.3), 214 out of 442 evaluable (48.4%) pts had discontinued RUX. 43 (20.1%) died while on therapy because of: MF progression (34.9%), infections (25.6%), heart disease (16.3%), second neoplasia (7%), hemorrhages (7%), other (9.2%). The median follow-up after RUX discontinuation for the remaining 171 pts was 11.3 months (0.5-66.7). Causes of RUX discontinuation were: drug-related toxicity (28.6%), loss/lack of response (23.4%), MF progression (12.3%), acute leukemia (AL) (13.4%), allogeneic stem cell transplantation (ASCT) (11.1%), second solid neoplasia (4.1%), other unrelated causes (i.e. pts decision; 7.1%). After stopping RUX, 68 pts received 1 line of therapy, 21 received 2 lines and 9 received 〉 2 treatments; 73 pts did not receive any therapy. Treatments received after RUX discontinuation, alone or in combination, included hydroxyurea (HU) (n. 61, 62.2%), ASCT (n. 20, 20.4%), second-generation JAK2 inhibitors (momelotinib/fedratinib/pacritinib) (n. 11, 11.2%), splenectomy (n. 7, 7.1%), azacytidine/decitabine (n. 5, 5.1%), chemotherapy (n. 4, 4.1%), investigational agents (imetelstat/PRM151: n. 4), danazole (n. 4), erythropoietin-stimulating agents (ESA) (n. 4). A total of 95 pts (55.6%) died after RUX discontinuation, because of: MF progression (30.5%), AL (25.4%), infections (14.7%), second neoplasia (9.5%), hemorrhages (4.2%), heart disease (4.2%), ASCT (4.2%), thrombosis (2.1%), other (5.2). Median survival time from RUX stop of the 171 evaluable pts was 22.6 mos (95% CI, 13.2-30.7). Among baseline features, survival after discontinuation was significantly influenced by the dynamic international prognostic score (DIPSS) category (p 〈 0.001), transfusion dependency (p 〈 0.001) and driver mutation status (with triple-negative pts having the worst survival compared to JAK2V617F and CALR-mutated pts, p=0.01). During therapy, 45 out of 153 (29.4%) and 123 out of 161 (76.4%) evaluable pts achieved a SR and a SyR at any time. Survival was not affected by the previous response to RUX at any time-point. Conversely, survival significantly differed according to the reason for stopping RUX, with pts discontinuing because of AL evolution/second solid neoplasia having the worst outcome (Figure 1a, p 〈 0.001). In pts who discontinued RUX in chronic phase, the use of second generation TKIs and other investigational agents tended to prolong survival compared to the administration of conventional medical treatments (i.e. HU, danazole, ESA) (Figure 1b, p=0.07) Discussion . After RUX failure, very limited therapeutic options are available and the prognosis of MF pts is dismal, particularly for those pts starting RUX with advanced stage disease (i.e. high DIPSS category and transfusion dependency). Also, disease evolution into AL and occurrence of a second solid neoplasia significantly reduced life expectancy. In chronic phase pts, survival probability may be improved by the use of medical therapies that are still in the experimental phase. Novel investigational agents are needed. Disclosures Palandri: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Abruzzese:BMS: Consultancy; Ariad: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Vitolo:Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Gilead: Speakers Bureau; Takeda: Speakers Bureau; Sandoz: Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Aversa:Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Basilea: Honoraria, Membership on an entity's Board of Directors or advisory committees; Merck: Honoraria; Astellas: Honoraria; Gilead: Honoraria, Membership on an entity's Board of Directors or advisory committees. Cuneo:Gilead: Other: advisory board, Speakers Bureau; Roche: Other: advisory board, Speakers Bureau; Abbvie: Other: advisory board, Speakers Bureau; janssen: Other: advisory board, Speakers Bureau. Foà:ROCHE: Other: ADVISORY BOARD, Speakers Bureau; AMGEN: Other: ADVISORY BOARD; JANSSEN: Other: ADVISORY BOARD, Speakers Bureau; GILEAD: Speakers Bureau; NOVARTIS: Speakers Bureau; CELTRION: Other: ADVISORY BOARD; ABBVIE: Other: ADVISORY BOARD, Speakers Bureau; INCYTE: Other: ADVISORY BOARD; CELGENE: Other: ADVISORY BOARD, Speakers Bureau. Di Raimondo:Celgene: Honoraria; Takeda: Honoraria, Research Funding. Cavo:Janssen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; GlaxoSmithKline: Honoraria, Membership on an entity's Board of Directors or advisory committees; AbbVie: Honoraria, Membership on an entity's Board of Directors or advisory committees; Adaptive Biotechnologies: Honoraria, Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees. Breccia:Pfizer: Honoraria; Incyte: Honoraria; BMS: Honoraria; Novartis: Honoraria. Palumbo:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees.

Abstract: To evaluate the prognosis of patients with Essential Thrombocythemia (ET) in the first decade of the century we assessed retrospectively the thrombosis free survival (TFS) and the overall survival (OS) of the patients diagnosed from 01/01/2000 to 31/12/2009 and collected in the database of our group. The diagnosis of ET was performed with PVSG, WHO 2001 or WHO 2008 criteria, according to the period of the first observation. The whole population of 757 patients was then divided in two groups: the first (group I) with the diagnosis performed between 01/01/2000 to 31/12/2005 (334 patients) with a median follow-up of 111,9 months, the second (group II) diagnosed between 01/01/2006 to 31/12/2009 (385 patients) with a median follow-up of 58,2 months. The main clinical features of the two groups of patients are reported in the Table 1. No difference was observed between the two groups as to age, gender, platelet and WBC count, Hb level, Cardio-Vascular Risk Factors (CVRF), spleen enlargement and occurrence of previous thrombotic events. The frequency of the JAK-2 V617F mutation resulted significantly different (49.1% vs 68.4%) but in the group I the search of the mutation was never performed at the diagnosis. The TFS and OS were calculated from the date of diagnosis to the date of any appropriate event or to the date of last follow-up with Kaplan-Meier product limit method; the comparison of proportions and median values was computed with the Chi-squared and the Mann-Withney tests, as indicated. No significant difference emerged neither for TFS (p= 0,09, HR 1,42, 95% C.I. 0.89-2.30) nor for OS (p= 0,15, HR 1,34, 95% C.I. 0,87-2,06). We also considered the type of treatment used in the two groups to assess the potential link between the therapy and TFS or OS. No difference emerged between the two groups as to anti-aggregating treatment (mainly ASA), equally utilized in both groups [287/369, 77,8%, and 330/383, 78,3%, respectively (p = 0,95)]. As for the cyto-reductive therapy, Hydroxyurea was used in 74.8% vs 67.9% (p= 0.60) and alkylating agents in 1.9% vs 2.1% (p= 0.85), whereas Anagrelide was used in 10,6% vs 3,9% (p= 0,001) and Interferon in 9,5% vs 5,2% (p= 0,037), respectively. This more frequent use of Anagrelide and Interferon in the first group (2000-2005) did not modify TFS and OS of the patients. In conclusion, no improvement was observed in the prognosis of ET patients in the recent years: thus, new efforts to identify patients at risk and the introduction of new drugs as JAK-2 inhibitors are warranted to improve the prognosis of these patients. Table Table. Disclosures Breccia: Bristol Myers Squibb: Honoraria; Pfizer: Honoraria; Novartis: Consultancy, Honoraria; Celgene: Honoraria; Ariad: Honoraria. Cimino:Celgene: Honoraria; Bristol-Mayer: Honoraria. Lo Coco:Pfizer: Consultancy; Baxalta: Consultancy; Novartis: Consultancy; Lundbeck: Honoraria, Speakers Bureau; Teva: Consultancy, Honoraria, Speakers Bureau. Latagliata:Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria; Janssen: Consultancy, Honoraria; Shire: Honoraria.

Abstract: Abstract 2797 Background: Nilotinib is a second-generation tyrosine kinase inhibitor that demonstrated higher and faster responses and lower progression rates compared to imatinib in ECP CML patients. Early cytogenetic and molecular responses have been associated with a better outcome in patients treated with imatinib, dasatinib, or nilotinib frontline. In particular, BCR-ABL transcript level 〈 10% at 3 months has been associated with: increased 2-year cumulative incidence of complete cytogenetic response (CCyR), major molecular response (MMR), and MR4.5 ( 〉 4.5 log reduction in BCR-ABL transcript level) with dasatinib (Marin D et al, Blood 2012); increased CCyR rate by 1 year, MMR rate by 2 years, and better progression-free survival (PFS) at 2 years, with dasatinib (DASISION; Hochhaus A et al, ASH 2011, abs. 2767); increased MMR rate by 1 year, and better PFS and overall survival (OS), with nilotinib (ENESTnd; Hochhaus A et al, EHA 2012, abs. 584). Here we report a landmark analyses based on BCR-ABL transcript level and cytogenetic response at 3 months to evaluate their impact on subsequent response and outcome in an independent cohort of patients treated with nilotinib-based regimens in Italy (CML Italian Registry of Nilotinib). Methods: The CML Italian Registry of Nilotinib includes 215 patients, enrolled in 2 multicenter phase II studies conducted by the GIMEMA CML WP (ClinicalTrials.gov. NCT00481052 and NCT00769327) or treated at the Dpt. of Hematology and Oncology, Bologna University Hospital, with nilotinib 300 mg BID or 400 mg BID as initial treatment. The median age was 53 years (range 18–86). The median follow-up was 29 months (range: 18–47 months). At 3 months 196/215 (91%) and 189/215 (88%) patients were evaluable for the molecular and cytogenetic response, respectively. BCR-ABL transcript levels were: 21% in 88%; 〉 1% to 2 10% in 11%; 〉 10% in 1%; given the very low proportion of patients with a BCR-ABL 〉 10% (n. 2), to the purpose of these analyses, patients have been divided into 2 groups, with a transcript level 21% (n. 173, 88%), or 〉 1% (n. 23, 12%). Cytogenetic response was: CCyR 84%; partial cytogenetic response (PCyR) 9%; less than PCyR 7%. We analyzed the rate of MMR at 1 year, and the failure-free survival (FFS, according to ELN 2009 definitions), PFS (transformation to accelerated or blastic phase), and OS (any death included) according to the BCR-ABL transcript levels and to the cytogenetic response at 3 months. Results: Of the 2 patients with a BCR-ABL transcript level 〉 10% at 3 months, 1 progressed to blastic phase at 1 year, while the other one obtained a CCyR at 6 months and a MMR at 24 months. Patients with BCR-ABL 2 1% at 3 months had a higher rate of MMR at 12 months with respect to those with a transcript level 〉 1% (79% vs. 35%, p 〈 0.001) (Table 1). A lower transcript level (BCR-ABL 2 1%) at 3 months correlated with a better FFS and PFS and a similar OS at 3 years. Patients with a MCgR and CCyR at 3 months had higher rates of MMR at 12 months (77% and 79%, respectively) vs. patients with less than a MCyR or less than a CCyR (46% and 57%, respectively) (p=0.02 and 0.019, respectively). Patients in MCgR at 3 months had a better FFS and PFS, but similar OS with respect to patients not in MCgR. Conclusion: In our national experience, where 42 centers are represented with at least 1 patient, a very small proportion of patients treated frontline with nilotinib failed to achieve a reduction to 〈 10% level of BCR-ABL transcript (2/196 or 1%) if compared to other reports: in the frame of the ENESTnd trial, 24/258 or 9% (Hochhaus et al, EHA 2012, abs. 584). The cut-off of 1% of BCR-ABL at 3 months in our experience is a reliable surrogate marker of response at 1 year (MMR) and outcome (PFS and FFS), along with the level of cytogenetic response achieved. These patients with 〉 1% of BCR-ABL at 3 months are characterized by a higher propensity to fail the treatment and to progress. Consequently, they deserve a close monitoring and, for those not achieving the expected cytogenetic and molecular responses later on (at 6–12 months), an optimization of the dose of nilotinib or a treatment modification is advised. Acknowledgments: European LeukemiaNet, University of Bologna, BolognAIL, COFIN. Disclosures: Gugliotta: Novartis: Consultancy, Honoraria; Bristol-Myers-Squibb: Consultancy, Honoraria. Castagnetti:Novartis: Consultancy, Honoraria; Bristol-Myers-Squibb: Consultancy, Honoraria. Breccia:Bristol Myers Squibb: Consultancy; Novartis: Consultancy. Abruzzese:Bristol Myers-Squibb and Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Soverini:Novartis: Consultancy; Bristol-Myers Squibb: Consultancy; ARIAD: Consultancy. Saglio:Novartis: Consultancy, Speakers Bureau; BMS: Consultancy, Speakers Bureau; Pfizer: Consultancy. Martinelli:Novartis: Consultancy, Honoraria, Speakers Bureau; Bristol-Myers-Squibb: Consultancy, Honoraria, Speakers Bureau. Baccarani:ARIAD, Novartis, Bristol Myers-Squibb, and Pfizer: Consultancy, Honoraria, Speakers Bureau. Rosti:Novartis Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Speakers Bureau; Pfizer: Speakers Bureau.

Abstract: Background: MPNs including Polycythemia Vera (PV), Essential Thrombocythemia (ET) and Primary Myelofibrosis (PMF), are clonal hematopoietic diseases in which the discovery of molecular driver mutations (JAK2, CALR, MPL) has deeply modified diagnostic approach in recent years. To date available data on epidemiology of MPNs and perspective analysis are rare. Our aim is to study the incidence of MPN Ph negative in a specific region of Italy named Latium and its variability across five years. Moreover we prospectively report the general features of our population. Method: We present here the prospective epidemiologic analysis of 1116 adult patients affected by MPNs (PV=289, ET=550, PMF=209) diagnosed according to 2008 WHO criteria, from January 2011 to December 2015 in 15 hematological Centers (5 academic and 10 community-based Hospitals) in Latium. A total of 289 PV, 550 ET and 209PMF were identified. The overall incidence rate of 289PV was 1.0/105 in 2011 and 2012, 1.1/105 in 2013, 0.9/105 in 2014 and 2015. The overall incidence rate of 550ET was 2.0/105 in 2011, 2.4/105 in 2012, 2.2/105 in 2013, 1.8/105 in 2014 and 1,2/105 in 2015 and the overall incidence rate of 209PMF was 0.7/105 in 2011 and 2012, 1.0/105 in 2013, 0.7/105 in 2014 and 0.5/105 in 2015. We have observed also 63 cases of MPNu (36M/32F) and the incidence rate was 0.3/105 in 2011 and 2012, 0.14/105 in 2013, 0.24/105 in 2014 and 0.22/105 in 2015. Baseline features of PV, ET and PMF patients are summarized in table 1. We have also analyzed the presence of comorbidities including obesity, arhythmia and neoplasia observed at the diagnosis in 1.6, 6.2 and 4% of all population, respectively; thirty-five percent of 1116 pts presented other comorbidities such as diabetes, inflammatory bowel disease, renal and liver failure. As thrombotic risk factors we considered diabetes, dislipidemia, smoke, essential hypertension and thrombophilia observed in 11,8, 16,2, 13,2, 51,7 and 3% of total pts, respectively. Conclusions: We confirm in our prospective observational protocol the overall incidence of MPN Ph negative, previously reported in the literature and the major incidence of male gender in PV and PMF, female in of ET. The annual incidence from 2011-2015 in Latium is remained substantially the same during the observation period. The decreasing trend observed in 2015 is probably due to the different update of some Centers that was done in October 2015 not including patients diagnosed in the last two months. Disclosures Latagliata: Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria; Janssen: Consultancy, Honoraria; Shire: Honoraria. Breccia:Pfizer: Honoraria; Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Celgene: Honoraria; Ariad: Honoraria. Cimino:Celgene: Honoraria; Bristol-Mayer: Honoraria.