Purpose of the study. A comparative evaluation of the effectiveness of different therapeutic strategies in patients with polycythemia vera (PV) and essential thrombocythemia (ET). Materials and methods. Patients with PV or ET, diagnosed according to the criteria WHO 2016 were included in the study. The primary endpoint - 6 months of therapy (clinical-hematological and molecular responses). The secondary endpoint - 12 months of therapy (clinico-hematologic, molecular, histological responses). Sixty three patients were included in the analysis: the first group consisted of 33 patients who received the therapy with ce-pegiterferone alpha-2b (ce-pegalpha-INF-α-2b), 10 of them received previous treatment; the second group - 23 patients btained hydroxycarbamide; the third group - 7 patients were treated with recombinant interferon alpha therapy (rINFα). In comparison groups, differences in age were revealed: patients receiving hydroxycarbamide therapy were older. Phlebotomy occurred in 36% of patients in the first group, 9% in the second group, and 14% in the third group. Results. By the 6th month of therapy, 43% of the patients receiving the ce-pegalpha-INF-α-2b had complete clinical-hematologic response, 36% had partial clinical-hematologic remission and stabilization of the disease was established in 21% cases. No disease progression occured. By the 12th month of therapy, statistically significant differences in terms of efficacy between the different therapeutic groups (p = 0.2462, Fisher's exact test). In all three groups, the allelic load of JAK2V617F decreased: from 50 to 19%, from 22.3 to 15.8%, from 50 to 7.19%, respectively. The lower the allele load positively correlated with better response to therapy, which was observed in all analyzed groups. Hematologic adverse events (AEs) were more frequently observed in patients receiving ce-pegalpha-INF-α-2b therapy. Local reactions developed on 3-7 days of therapy as a hyperemic macula at the injection site. Both these reactions and hair loss did not influence on patient’s condition. In the second group (patients with hydroxycarbamide therapy) there were changes in the skin and mucous membranes: dry skin, stomatitis, and in older patients new keratomas appeared. The flu-like syndrome was the most common adverse event associated with the therapy of ce-pegalpha-INF-α-2b, which fully relived during the first month of therapy. There was only one case with the flu-like syndrome we observed at the 11th month of therapy. As a rule, the biochemical blood test changes did not influence on patient’s condition, were mostly associated with dietary violations, had a tendency to self-resolution and did not require medical interventions. Serious AEs were reported in one case - pulmonary embolism in a patient treated with rINFα. The reasons for the therapy discontinue in group 1: toxic hepatitis, intolerance, by the request of the patient, inadequate efficacy of therapy; in group 2: skin toxicity, in group 3: thromboses. The conclusion. Treatment of ce-pegalpha-INF-α-2b in patients with PV and ET is highly effective - the most patients pbtained clinical and hematological responses. There were no statistically significant differences in these parameters in comparison with hydroxycarbamide and rINFα. The use of the ce-pegalpha-INF-α-2b had an acceptable safety profile. The estimated therapeutic dose should be calculated according to body weight. To reduce the frequency of hematologic AE, titration of the drug dose is required.

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Background. Wt1 expression is thoroughly studied in acute myeloblastic leukemia and widely used for disease response monitoring.Its role in MPN is less known. Aim. The aim of the study was to reveal the incidence of elevated Wt1 expression in PMF and secondary MF, as well as to find out clinical significance during ruxolitinib therapy. Patients and methods. 38 pts were included ( Primary Mf-31, post PV- and post ET Mf- 8, males - 12, females- 26). Wt1 expression in peripheral blood was studied by qPCR at diagnosis and during ruxolitinib treatment using Quiagen kit. Dynamics of Wt1 expression was studied in 20 pts treated by ruxolininib. Spleen size was measured in cm below costal margin. Results. Wt1 increased expression was found in 35/38 pts. Correlation of Wt1 expression and DIPSS was not found. The relation between blast cell and Wt1 expression was studied by dividing pts in 3 subgroups according to the number of blast cells in peripheral blood- 0, 1-2, >2. Wt1 expression was lowest in the 1st group, and the highest in the 3rd group((p<.05). Ruxolitinib treatment resulted in the decrease of spleen size and parallel decrease of Wt1 level( p<.05 -Fig1).Pts with transformation to acute leukemia(5) had higher level of Wt1 than before transformation. Conclusion. Wt1 expression is elevated in the majority of pts with PMF as well as in secondary MF. Correlation was found with blast level and spleen size. Wt1 could be used for monitoring efficacy of ruxolitinib therapy Disclosures Konopleva: Reata Pharmaceuticals: Equity Ownership; Abbvie: Consultancy, Research Funding; Genentech: Consultancy, Research Funding; Stemline: Consultancy, Research Funding; Eli Lilly: Research Funding; Cellectis: Research Funding; Calithera: Research Funding.

Aim. To assess the efficacy of targeted therapy with ruxolitinib in patients with myelofibrosis in real clinical practice in Russia. To determine the prognostic value of spleen reduction in the early stages of ruxolitinib treatment and its effect on overall survival. Materials & Methods. The present retrospective study was based on the data of 10 centers of Russia. It included 56 myelofibrosis (primary or post-polycythemic and post-throm-bocythemic) patients who received ruxolitinib. The median age of patients was 56 years (range 26-76 years). Most of them (59 %) were considered intermediate-1 risk according Results. By the start of data collection most of patients (79 %) had been treated with ruxolitinib. In no case therapy was withdrawn for the reason of drug toxicity. On ruxolitinib constitutional symptoms were reversed in 70 %, 87 %, and 98 % of patients by months 1, 3 and 6, respectively. In 36 % and 46 % of patients by months 3 and 6, respectively, > 50 % decrease in spleen size was observed. Overall, in 31 % and 27 % of cases the size of the spleen decreased by less than 25 % by months 3 and 6, respectively. The factors affecting the changes in spleen size have not been identified. The probability of overall survival by years 2 and 5 of follow-up was 97 % and almost 70 %, respectively. This parameter was significantly affected by the extent of spleen size reduction by month 3 of follow-up as well as by its initial size. Conclusion. Ruxolitinib shows high efficacy for both decrease of general myelofibrosis symptoms and reduction in spleen size. The extent of spleen reduction is an important prognostic factor. It seems, that in patients with insufficient spleen reduction an increase in drug dose is advisable. If it is not possible, alternative methods of treatment should be sought.

CA 6.0 was used for data analysis. The results were presented as median with 95% confidence interval (CI). Mann-Whitney and Spearman rank tests were applied, the differences considered statistically significant with p < 0.05( * ). Results: 23 (63.9%) PMF patients in the study were JAK2V617F-positive, 8 (22.2%) had mutation in CALR gene. JAK2V617F allele burden data was available in 13 PMF patients with median 8.1% (95%CI 3.4-43.8%). The results of hemostatic parameters in PMF patients and controls are shown in Table 1.