Abstract: Higher doses of cytarabine appear to improve long-term outcome in acute myeloid leukemia (AML), in particular for younger patients. To this end, the optimal dosage of single-agent cytarabine in consolidation therapy remains elusive. Here, we assessed the impact of different dosages of cytarabine consolidation after 7 + 3 induction on outcome in a large real-world data set from the German Study Alliance Leukemia-Acute Myeloid Leukemia (SAL-AML) registry. Methods Patients between 18 and 64 years of age, registered between April 2005 and September 2020, who attained complete remission after intensive induction and received at least one consolidation cycle with intermediate (IDAC) or high-dose cytarabine (HiDAC) were selected. To account for differences in patient and disease characteristics between both groups, the average treatment effect was estimated by propensity score weighting. Results Six-hundred-forty-two patients received HiDAC consolidation with median dosage of 17.6 (IQR (interquartile range), 16.5–18.0) g/m 2 for a median number of 3 cycles (IQR, 2–3), whereas 178 patients received IDAC consolidation with 5.9 (IQR, 5.7–8.6) g/m 2 for a median of 2 cycles (IQR, 1–3). Both groups differed significantly in some important characteristics (age, sex, cytogenetic risk group, ECOG performance status, disease status, HCT-CI, number of induction cycles). After propensity score weighting for differences in patient and disease characteristics, relapse-free survival after 2 years was comparable between HiDAC-treated (55.3%) and IDAC-treated (55.6%) patients (HR = 0.935, p  = 0.69). Moreover, no significant differences in overall survival were observed after 2 years (84.7 vs. 80.6%, HR = 1.101, p  = 0.65). Notably, more patients treated with IDAC received allogeneic hematopoietic cell transplantation in first remission (37.6 vs. 19.8%, p   〈  0.001). Censoring for allogeneic hematopoietic cell transplantation in first remission revealed no significant survival difference with regard to cytarabine dosage. Considering only of European LeukemiaNet (ELN) favorable-risk AML patients, there was no significant difference in outcome. Of note, significantly more patients treated with HiDAC suffered from ≥ 3 CTCAE infectious complications (56.7 [95%-CI 52.8–60.6%] vs. 44.1% [95%-CI 36.6–51.7%] ; p  = 0,004). The rate of other ≥ 3 CTCAE non-hematological toxicities and secondary malignancies was comparable in both treatment groups. Conclusions This retrospective analysis suggests no significant benefit of high-dose cytarabine compared to intermediate dosages in consolidation for AML patients under 65 years of age, independent of ELN risk group. Trial registration NCT03188874.

Abstract: Functional perturbations of the cohesin complex with subsequent changes in chromatin structure and replication are reported in a multitude of cancers including acute myeloid leukemia (AML). Mutations of its STAG2 subunit may predict unfavorable risk as recognized by the 2022 European Leukemia Net recommendations, but the underlying evidence is limited by small sample sizes and conflicting observations regarding clinical outcomes, as well as scarce information on other cohesion complex subunits. We retrospectively analyzed data from a multi-center cohort of 1615 intensively treated AML patients and identified distinct co-mutational patters for mutations of STAG2 , which were associated with normal karyotypes (NK) and concomitant mutations in IDH2 , RUNX1, BCOR, ASXL1 , and SRSF2 . Mutated RAD21 was associated with NK, mutated EZH2, KRAS, CBL , and NPM1 . Patients harboring mutated STAG2 were older and presented with decreased white blood cell, bone marrow and peripheral blood blast counts. Overall, neither mutated STAG2, RAD21, SMC1A nor SMC3 displayed any significant, independent effect on clinical outcomes defined as complete remission, event-free, relapse-free or overall survival. However, we found almost complete mutual exclusivity of genetic alterations of individual cohesin subunits. This mutual exclusivity may be the basis for therapeutic strategies via synthetic lethality in cohesin mutated AML.

Abstract: Tandem-duplication mutations of the UBTF gene ( UBTF -TDs) coding for the upstream binding transcription factor have recently been described in pediatric patients with acute myeloid leukemia (AML) and were found to be associated with particular genetics (trisomy 8 (+8), FLT3 -internal tandem duplications ( FLT3 -ITD), WT1 -mutations) and inferior outcome. Due to limited knowledge on UBTF- TDs in adult AML, we screened 4247 newly diagnosed adult AML and higher-risk myelodysplastic syndrome (MDS) patients using high-resolution fragment analysis. UBTF -TDs were overall rare ( n  = 52/4247; 1.2%), but significantly enriched in younger patients (median age 41 years) and associated with MDS-related morphology as well as significantly lower hemoglobin and platelet levels. Patients with UBTF -TDs had significantly higher rates of +8 (34% vs. 9%), WT1 (52% vs. 7%) and FLT3 -ITD (50% vs. 20.8%) co-mutations, whereas UBTF -TDs were mutually exclusive with several class-defining lesions such as mutant NPM1 , in-frame CEBPA bZIP mutations as well as t(8;21). Based on the high-variant allele frequency found and the fact that all relapsed patients analyzed ( n  = 5) retained the UBTF -TD mutation, UBTF -TDs represent early clonal events and are stable over the disease course. In univariate analysis, UBTF -TDs did not represent a significant factor for overall or relapse-free survival in the entire cohort. However, in patients under 50 years of age, who represent the majority of UBTF -mutant patients, UBTF -TDs were an independent prognostic factor for inferior event-free (EFS), relapse-free (RFS) and overall survival (OS), which was confirmed by multivariable analyses including established risk factors such as age and ELN2022 genetic risk groups (EFS [HR: 2.20; 95% CI 1.52–3.17, p   〈  0.001], RFS [HR: 1.59; 95% CI 1.02–2.46, p  = 0.039] and OS [HR: 1.64; 95% CI 1.08–2.49, p  = 0.020]). In summary, UBTF -TDs appear to represent a novel class-defining lesion not only in pediatric AML but also younger adults and are associated with myelodysplasia and inferior outcome in these patients.

Abstract: Background In newly diagnosed acute myeloid leukemia (AML), the general recommendation is to start treatment immediately after the diagnosis has been made. This paradigm is based both on the observation that untreated acute leukemia has a poor prognosis and on retrospective analyses demonstrating a shorter survival in younger AML patients (pts) in whom treatment was delayed by more than 5 days (Sekeres et al., 2009). A more recent single-center analysis came to a different conclusion, showing no prognostic effect for the time from diagnosis to treatment (TDT; Bertoli et al., 2013). We explored the relationship between TDT and prognosis on a large set of real-world data from the AML registry of the Study Alliance Leukemia (SAL) and compared it to the published cohorts. Methods The SAL runs a transregional AML registry in 46 treatment centers across Germany (NCT03188874). All registered patients with an intensive induction treatment, a minimum follow-up time of 12 months and no acute promyelocytic leukemia were selected (n=2,200). Treatment start was defined by the first day of cytarabine, whereas single agent hydroxyurea (HU) was labeled as pretreatment. We analyzed the influence of TDT on complete remission (CR), early death (ED) and overall survival (OS) in univariable analyses for each day of treatment delay, in groups of 0-5, 6-10, 11-15 and & gt;15 days of TDT, and by using the restricted cubic spline (RCS) method for data modelling. In order to adjust for the influence of established prognostic variables on the outcomes, we used multivariable regression models and propensity score weighting. The influence of HU pretreatment on outcomes was investigated by introducing an interaction term between TDT and the presence of HU pretreatment. Results The median age was 59 years (y) (IQR 50-68), the proportion of pts with favorable, intermediate and adverse genetic risk according to ELN was 27%, 53%, and 20%; & gt;95% of pts received induction treatment with standard 7+3. HU pretreatment was administered in 4% of pts. The median TDT was 3 days (IQR 2-6). Descriptive statistics after grouping of pts showed the highest median age and the lowest proportion of NPM1 mutated and favorable risk in the TDT group 11-15. Of all pts, 79% achieved a CR/CRi; unadjusted CR rates for the patient groups with TDT of 0-5, 6-10, 11-15 and & gt;15 days were 80%, 77%, 74% and 76%, respectively (p=0.317). In multivariable analysis accounting for the influence of ELN risk, age, WBC, LDH, de novo versus secondary AML and ECOG, the OR for each additional day of TDT was 0.99 (95%-CI, 0.97-1.00; p=0.124). Four percent of pts died within the first 30 days from treatment start. The respective rates in the four TDT categories were 4.0%, 3.8%, 5.1% and 4.1% (p=0.960). In multivariable analysis, the OR for TDT was 1.01 (95%-CI, 0.98-1.05; p=0.549). After a median follow-up of 40 months, the 2-y OS of all pts was 51%. The unadjusted 2-y OS rates stratified by TDT of 0-5, 6-10, 11-15, & gt;15 days were 52, 49, 46, and 51% (see Table 1 and Figure 1). The hazard ratio (HR) for each day of treatment delay was 1.00 (95%-CI; 0.99-1.01; p=0.317). In multivariable Cox regression analysis, the HR for TDT as continuous variable was 1.00 (95%-CI, 0.99-1.01; p=0.689). When OS was analyzed separately stratified for age ≤60 and & gt;60 ys and for high versus lower initial WBC defined by a threshold of 50 x 109/L, no significant differences between TDT groups were observed. Multivariable models using TDT as a grouped variable or with RCS did not provide evidence for a significant influence of TDT on outcomes. Propensity score matching of pts in the four TDT groups did not reveal an influence on outcomes. The use of HU was not associated with CR, ED nor OS. Conclusion Our study on 2,200 newly diagnosed registry pts receiving consistent intensive induction with standard-dose cytarabine plus daunorubicin (7+3) suggests that TDT is not related to response or survival, neither in younger nor in older pts. Despite multivariable analyses, a bias towards longer TDT intervals in pts judged to be clinically stable by the treating physician cannot be excluded entirely. As treatment stratification in intensive first-line treatment of AML evolves, the TDT data suggests that it may be a safe and reasonable approach to wait for genetic and other laboratory test results in order to assign clinically stable pts to the best available treatment option before the start of intensive treatment. Disclosures Krämer: Daiichi-Sankyo: Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; BMS: Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Hänel:Roche: Honoraria; Amgen: Honoraria; Celgene: Other: advisory board; Novartis: Honoraria; Takeda: Other: advisory board. Jost:Daiichi: Honoraria; Sanofi: Honoraria; Gilead: Other: travel grants; Jazz Pharmaceuticals: Honoraria. Brümmendorf:Merck: Consultancy; Janssen: Consultancy; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; University Hospital of the RWTH Aachen: Employment; Ariad: Consultancy. Krause:Siemens: Research Funding; Takeda: Honoraria; MSD: Honoraria; Gilead: Other: travel; Celgene Corporation: Other: Travel. Scholl:Novartis: Other: Project funding; Pfizer: Other: Advisory boards; Gilead: Other: Project funding; Daiichi Sankyo: Other: Advisory boards; AbbVie: Other: Advisory boards. Hochhaus:Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; Incyte: Research Funding; MSD: Research Funding. Kiani:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Middeke:Sanofi: Research Funding, Speakers Bureau; Roche: Speakers Bureau; AbbVie: Consultancy, Speakers Bureau; Gilead: Consultancy; Janssen: Consultancy, Speakers Bureau; MSD: Consultancy. Thiede:AgenDix GmbH: Employment, Equity Ownership; Novartis: Research Funding, Speakers Bureau; Bayer: Research Funding; Daiichi-Sankyo: Speakers Bureau. Stoelzel:JAZZ Pharmaceuticals: Consultancy; Neovii: Other: Travel funding; Shire: Consultancy, Other: Travel funding. Platzbecker:Celgene: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Research Funding.

Abstract: Introduction: Polycythemia vera (PV) is a myeloproliferative neoplasm (MPN) characterized by expansion of the granulocytic, erythrocytic, and megakaryocytic lineages in the bone marrow and peripheral blood, and in most cases, by the presence of a JAK2 mutation. Survival of patients with PV is decreased compared with age-matched controls, and this is mainly due to thromboembolic complications followed by progression to post-PV myelofibrosis and acute leukemia. While no curative treatment exists, cytoreductive treatment with hydroxyurea (HU) or ropeginterferon is approved in EU for first-line therapy, and ruxolitinib (RUX) is approved in EU and US for second-line therapy in patients with HU intolerance or resistance. The current futility analysis assesses the efficacy of ruxolitinib in newly-diagnosed PV treated within the Ruxo-BEAT trial. Methods: This clinical trial entitled "Ruxolitinib versus Best Available Therapy in patients with high-risk Polycythemia Vera or high-risk Essential Thrombocythemia" (Ruxo-BEAT; NCT02577926) is a multicenter, open-label, two-arm phase-IIb trial with a target population of 380 pts with PV and ET. Patients in first-line PV and in first and later lines ET are randomized in a 1:1 manner to receive either RUX or best available therapy (BAT). Crossover from BAT to RUX is possible in eligible patients after 6 months. Patients with PV in the RUX arm receive a starting dose of 10 mg bid and may increase their dose up to 20 mg bid. Primary endpoint is the rate of complete clinicohematologic response rate (CHR) at month 6 as defined by Barosi et al Blood 2009. Secondary endpoints include differences in the absence of phlebotomies, spleen size, patient-reported outcomes, and survival. This is a pre-specified futility analysis of RUX in the PV arm, after 50 PV patients had been enrolled. Of the 50 patients, 28 patients with newly-diagnosed PV were randomized into the RUX arm and were analyzed (a maximum of 6 weeks of HU, anagrelide, or interferon therapy was allowed). The PV arm would have to be closed if no favorable trend were observed for RUX for any of the following variables: (1) improvement (decrease) in the hematocrit level during 6 months of treatment, (2) improvement (decrease) of the JAK2V617F allele burden during 6 months of treatment, or (3) improvement of one of the following three symptom variables assessed by physician´s judgement or via MPN Symptom Assessment Form (MPN-SAF) during 6 months of treatment: pruritus, night sweats, or bone pain. Differences between screening (Hct) or baseline (all other variables) and end of month 6 (all variables) were calculated using Fisher´s exact test (for physician-assessed pruritus and night sweats) or the Wilcoxon matched-pairs signed rank test (all other variables). Results: 28 patients received RUX for at least 6 months. After 6 months, the mean hematocrit level decreased from 45.9+/-5.6% to 41.0+/-5.0% (mean+/-SD) (p=0.0003). The number of phlebotomies calculated per year decreased from 4.2+/-3.9% to 0.96+/-2.1 (p=0.0009). Mean JAK2V617F allele burden decreased from 50.2+/28.4% to 44.0+/-28.5% (p=0.0039). The percentage of patients, as assessed by the physician, with pruritus or night sweats decreased from 41% to 26% (trending with p=0.13), and from 30% to 11% (p=0.02), respectively. The points reported by patients themselves on the MPN-SAF survey for pruritus decreased from 2.7+/-3.0 to 1.3+/-1.5 (p=0.0095) and there was a strong trend for reduction of night sweat points (from 3.1+/-3.6 to 1.6+/-2.4; p=0.0579), while the points for bone pain remained unaltered (2.0+/-2.8 to 1.4+/-2.2; p=0.215). Conclusion: Treatment with ruxolitinib in first line PV is efficient regarding the above-mentioned endpoints. Recruitment of our trial will be ongoing. In order not to weaken the study´s statistical power, comparison of both arms was not performed. Disclosures Koschmieder: Ariad: Consultancy, Honoraria, 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, Research Funding; Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bristol Myers-Squibb: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Incyte: 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; Shire: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis Foundation: Research Funding; CTI: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; AOP Pharma: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Isfort:Mundipharma: Other: Travel reimbursement; Amgen: Other: Travel reimbursement; Hexal: Other: Travel reimbursement; BMS: Honoraria; Ariad: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria, Other: Travel reimbursement; Novartis: Consultancy, Honoraria, Other: Travel reimbursement; Roche: Other: Travel reimbursement; Alexion: Other: Travel reimbursement. Schafhausen:Novartis: Consultancy, Honoraria; Incyte: Consultancy, Equity Ownership, Honoraria. Griesshammer:Novartis: Consultancy, Honoraria, Speakers Bureau. Platzbecker:Abbvie: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Novartis: Consultancy, Honoraria, Research Funding. Döhner:CTI Biopharma: Consultancy, Honoraria; Daiichi: Honoraria; Jazz: Honoraria; Novartis: Honoraria; Celgene: Honoraria; Janssen: Honoraria. Jost:Abbvie: Consultancy, Patents & Royalties: Royalty payments for the drug compound ABT-199, Research Funding; Bohringer: Consultancy, Research Funding; BMS: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; Celgene: Other: Travel Support; Novartis: Research Funding. von Bubnoff:Novartis: Research Funding. Stegelmann:Novartis: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Crysandt:Amgem: Other: travel grant; celgene: Other: travel grant; Pfizer: Other: travel grant; Gilead: Other: travel grant; Incyte: Membership on an entity's Board of Directors or advisory committees. Gezer:AMGEM: Membership on an entity's Board of Directors or advisory committees. Brümmendorf:Merck: Consultancy; Pfizer: Consultancy, Research Funding; University Hospital of the RWTH Aachen: Employment; Janssen: Consultancy; Ariad: Consultancy; Novartis: Consultancy, Research Funding. OffLabel Disclosure: Ruxolitinib as first-line treatment in newly-diagnosed PV

Abstract: Introduction: Ph-negative myeloproliferative neoplasms (MPN) represent a heterogeneous group of hematological malignancies which differ in various aspects such as clinical manifestation, underlying genetic aberrations, cytomorphological features and life expectancy. However, across all subtypes, patients (pts) with MPN often suffer from severe symptoms, resulting in an impairment of the quality of life (QoL). Methods: The German Study Group for MPN (GSG-MPN) Bioregistry is a non-interventional prospective study including pts of at least 18 years with diagnosis of Ph-negative MPN according to WHO criteria (2008) having provided written informed consent. The Bioregistry study also includes assessment of QoL at baseline and on an annual basis, with all pts completing the standardized MPN-SAF-TSS questionnaire (German version) and an additional item indicating pts' subjective overall QoL on an 11-point Likert scale. Total scores range from 0 to 90 and were calculated if at least 6 items were answered (Emanuel RM et al., J Clin Oncol. 2012; 30 (33): 4098-103.)). Clinical variables, as documented in the registry, included comorbidities, reported symptoms as assessed by the physician, bleeding, and thromboembolic events (TEE). For statistical analysis, standard descriptive methods, Spearman correlation coefficient, Wilcoxon test/Kruskal-Wallis test for significance testing, and Kendall´s tau-b statistics were used. Results: 1,403 pts who had completed at least six items of the QoL assessment at baseline were included in this analysis. Median age at diagnosis was 58 years (interquartile range [IQR] 22), 98% were Caucasian, 50% were female. 494 pts were diagnosed with essential thrombocythemia (ET, 35%), 444 pts with polycythemia vera (PV, 32%), 302 pts with primary myelofibrosis (PMF, 22%), 83 pts with MPN-unclassifiable (MPNu, 6%), 43 pts with post-ET-myelofibrosis (pET-MF, 3%) and 37 pts with post-PV-myelofibrosis (pPV-MF, 3%). The most common complaint reported via the MPN-SAF-TSS was fatigue, occurring in more than 80% of the pts in all entities except MPNu (77%). More than 50 % of pts in each entity reported to suffer from early satiety, night sweats, concentration problems, or overall impairment of QoL. Table 1 summarizes all 9 symptoms and overall QoL from the questionnaire categorized by entity. Interestingly, the pts suffering from PET-MF reported the highest symptom burden, while PPV-MF pts showed the lowest overall symptom burden (median total QoL score of 23 vs. 16; p=0.01). The strongest correlations among the different symptoms were seen for fatigue and overall QoL (Spearman´s rho 0.57, p 〈 0.001) as well as concentration problems and overall QoL (Spearman´s rho 0.33, p 〈 0.001). Furthermore, the impact of variables such as age, comorbidities and TEE on QoL was assessed. Abdominal discomfort increased with age (rho = -0.14, p 〈 0.001). A history of TEE before baseline assessment correlated significantly with fatigue scores (Spearman rho= 0.07, p 〈 0.01) and with concentration problems (rho=0.07, p 〈 0.01). With an increasing number of TEE, scores for both of these items worsened over time (p 〈 0.01, respectively). Moreover, MPN-total score (MPN-TSS) was higher in pts with more comorbidities (Median: 18 (IQR:23), and 25 (27) for pts with 〈 3 versus ≥3 comorbidities, respectively, p= 0.017). Next, we compared data on 5 of the pts symptoms (reported in the questionnaire) to their assessment by the treating physician (only 5 items were available both in the questionnaire and in our registry database) in order to understand whether the "physician´s opinion" is congruent with the patient´s reported outcome in the questionnaire. While there were clear associations between the two data sources, there were also significant discrepancies, e.g., the physician did not indicate fatigue in about 20% of pts with self-assessed fatigue score of 〉 =6 points. The most concordant symptom was night sweats (further details in table 2). Conclusions: Most MPN pts suffer from a significant symptom burden which impairs their QoL. TEE influence fatigue and concentration problems. The perception of symptoms (particularly with respect to fatigue) differs between pts and treating physician which suggests that questionnaires should be used on a routine basis in order to faithfully reflect patient´s degree of suffering from MPN and/or treatment. Disclosures Isfort: Amgen: Other: i.e. travel support; Mundipharma: Other: i.e. travel support; Roche: Other: i.e. travel support; Incyte/Ariad: Consultancy; Pfizer: Consultancy, Honoraria, Other: i.e. travel support; BMS: Honoraria; Novartis: Consultancy, Honoraria, Other: i.e. travel support; Alexion: Other: i.e. travel support; Hexal: Other: i.e. travel support. Stegelmann:Novartis: Consultancy, Honoraria. Al-Ali:Gilead: Consultancy, Research Funding; Otsuka: Consultancy, Honoraria; Alexion: Honoraria; Novartis: Consultancy, Honoraria, Other: Travel support, Research Funding; Celgene: Honoraria, Other: Travel support, Research Funding. Goethert:BMS: Consultancy, Honoraria, Other: i.e. travel support; Incyte: Consultancy, Honoraria, Other: i.e. travel support; Pfizer: Consultancy, Honoraria; Novartis: Honoraria; Proteros Biostructures: Honoraria; AOP Orphan: Other: i.e. travel support. Haenel:Novartis: Honoraria; Takeda: Honoraria; Roche: Honoraria; Amgen: Honoraria. Platzbecker:Celgene: Research Funding. Griesshammer:Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Brümmendorf:Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Janssen: Consultancy; Merck: Consultancy; Takeda: Consultancy.

Abstract: Patients (pts) with polycythemia vera (PV) suffer from pruritus, night sweats, and other symptoms, as well as from thromboembolic complications and progression to post-PV myelofibrosis. Ruxolitinib (RUX) is approved for second-line therapy in high-risk PV pts with hydroxyurea intolerance or resistance. The RuxoBEAT trial (NCT02577926, registered on October 1, 2015, at clinicaltrials.gov) is a multicenter, open-label, two-arm phase-IIb trial with a target population of 380 pts with PV or ET, randomized to receive RUX or best available therapy. This pre-specified futility analysis assesses the early clinical benefit and tolerability of RUX in previously untreated PV pts (6-week cytoreduction was allowed). Twenty-eight patients were randomly assigned to receive RUX. Compared to baseline, after 6 months of treatment, there was a significant reduction of median hematocrit (46 to 41%), the median number of phlebotomies per year (4.0 to 0), and median patient-reported pruritus scores (2 to 1), and a trend for reduced night sweat scores (1.5 to 0). JAK2V617F allele burden, as part of the scientific research program, also significantly decreased. One hundred nine adverse events (AEs) occurred in 24/28 patients (all grade 1 to 3), and no pt permanently discontinued treatment because of AEs. Thus, treatment with ruxolitinib in untreated PV pts is feasible, well-tolerated, and efficient regarding the above-mentioned endpoints.