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Aim. To study the impact of different clinical and biological factors on sustaining molecular remission after discontinuation of tyrosine kinase inhibitors (TKI) therapy in chronic myeloid leukemia (CML) patients with a stable deep molecular response (MR). Materials & Methods. The prospective multi-center trial on molecular remission sustainability after TKIs withdrawal, held from 2015 to 2019, enrolled 98 CML patients. The trial included patients with chronic phase CML treated with TKIs at least during 3 years and having a stable deep MR (< МО4; BCR-ABL < 0.01 %) during at least 2 years. Molecular monitoring was carried out every month during first 6 months after TKIs withdrawal, every 2 months during 0.5-1 year, and every 3 months after 1-year follow-up. In case of the loss of major MR (BCR-ABL > 0.1 %) therapy was reinitiated. Results. Three-year molecular relapse-free survival was 51 % (95% confidence interval 41-61 %) in all patients, 25 % in patients with the failure of prior treatment discontinuation, and 53 % in patients who discontinued TKI therapy for the first time. According to univariate analysis, the following factors proved to be significant: persistance of deep MR, duration of therapy, and depth of MR. It was shown that TKI therapy duration, but not deep MR persistance, has independent prognostic value for the Russian population of CML patients. No significant differences were identified in 3-year molecular relapse-free survival in the groups of patients treated only with imatinib (55 %) compared with patients who received 2nd generation TKI (TKI2) as first-line (70 %; p = 0.26) and second-line (39 %; p = 0.09) therapy. However, duration of therapy in patients treated with TKI2 as first-line therapy was more than twice as short as in patients treated with imatinib as first-line therapy (median 41.5 vs. 96.4 months, respectively; p < 0.0001). Conclusion. Longer therapy duration and MR depth (< M04.5) before TKI withdrawal raise the probability of sustaining off-treatment remission. The study showed that molecular relapse-free survival does not significantly increase with the use of TKI2 as first-line treatment compared to imatinib. Nevertheless, TKI2 as first-line treatment enables to halve the duration of therapy needed to achieve comparable molecular relapse-free survival, as compared with imatinib.

Aim. To analyze adverse cardiovascular events in chronic myeloid leukemia (CML) patients who received various tyrosine kinase inhibitors (TKI). Materials & Methods. The trial included 97 CML patients with nilotinib, dasatinib or imatinib indications. By the time of examination the patients had undergone TKI therapy for 1-138 months. The three of them were sequentially treated with 2 drugs over the monitoring period. All CML patients were aged 22-79 years (median 53.5 years): 55 women were aged 22-71 years (median 53.5 years) and 42 men were aged 24-79 years (median 53 years). Results. The comparative analysis demonstrated significantly higher impact of nilotinib on daily maximum QTc duration compared with other TKIs. The patients who received nilotinib (n = 15) throughout 38 months had QTc of 0.47 s (interquartile range [IQR] 0.46-0.47 s), in imatinib group (n = 17) QTc was 0.43 s (IQR 0.43-0.44 s), and in dasatinib group (n = 4) QTc was 0.43 s (IQR 0.42-0.44 s) (p = 0.0008). Among all patients treated with nilotinib there were 62 % (31/50) with QTc > 0.46 s, in imatinib (6/41) and dasatinib (2/18) groups it was detected in 14.6 % and 11.1 % of patients, respectively (p = 0.0008). Five patients had QTc > 0.48 s, which is the criterion for discontinuation of treatment or dose reduction. In two patients the identified changes of QTc duration required TKI temporary suspension. After nilotinib dose reduction or discontinuation QTc duration normalized in all cases within 2 weeks. Decreased ankle-brachial index (ABI) < 0.9 without pronounced clinical symptoms was identified in two patients who received nilotinib. Afterwards they showed peripheral occlusive disease of lower extremities, and nilotinib treatment was discontinued. In patients treated with other TKIs no occlusive vascular lesions were observed. A case of chronic heart failure with reduced left ventricular ejection fraction developing on nilotinib therapy was revealed and described. Conclusion. Despite high specificity for BCR-ABL tyrosine kinase, new TKIs can, although rarely, induce cardiovascular adverse events. Prior to TKI treatment assignment CML patients should be examined with ECG and EchoCG with systolic function evaluation, and the measurement of pulmonary artery pressure as well as ABI. The examination should be repeated in the end of the 1st year TKI treatment if there is no reason for extra examinations. It is recommended to hold 24-hour ECG monitoring with QTc max measurement prior to nilotinib assignment, then once a year within 2 years of nilotinib treatment, and once in 6 months after 3 years of therapy.

Background. Current clinical guidelines on diagnosis and treatment of chronic myeloid leukemia (CML) define indications for substitution of first-line tyrosine kinase inhibitor (TKI) at therapy failure during different phases of disease progression. Aim. To assess the efficacy of CML treatment with implementing the protocol of timely monitoring and switching to another TKI. Materials & Methods. Patients were included into pilot prospective study РИТМ during 5 years. Data on 100 CML patients were analyzed. Therapy and monitoring were conducted according to the Federal clinical guidelines on CML diagnosis and therapy, 2013. Results. Median follow-up after initiation of treatment was 46 months (range 12-74). Imatinib mesylate was administered as first-line therapy to 91 (91 %) patients, 9 (9 %) patients received 2nd generation TKI (TKI2). Therapy failure was registered in 31 (31 %) patients; 26 (84 %) of them were switched to TKI2. At the time of analysis 95 (95 %) patients were followed-up. Cumulative incidence of CML-associated mortality was 2 %. By the fifth year of follow-up cumulative probability of complete cytogenetic, major and deep molecular responses was 93 %, 88 % and 66 %, respectively. Conclusion. CML treatment according to current guidelines yields the results comparable with those achieved by first-line TKI2 therapy. This approach reduces CML treatment costs and lowers the risk of TKI2-associated adverse events. Due to a high rate of deep molecular response the proportion of CML patients in remission without treatment can be increased in the future.

Compressive Sensing (CS) is a new paradigm of sensing signal. It states that it is possible to recover certain signals from a much fewer number of measurements in comparison with traditional methods. Devices which implement this approach are called analog-to-information converters. This paper considers a brief overview of the CS theory, a non-uniform sampling (NUS) architecture, identify key parameters of this architecture. We conduct a study of the parameters of the NUS architecture, highlight a dependence of some parameters on others and review publications which confirm the results.

Introduction Data on the effectiveness and safety of new vaccines against COVID-19 in patients (pts) with hematological diseases are just beginning to accumulate. We planned to obtain such information for pts with chronic myeloid leukemia (CML) during vaccination. Objective. To evaluate the antibodies formation and adverse events (AEs) after vaccination against COVID-19 in pts with CML Materials and methods. All pts with CML diagnosis who applied to the National Research Center for Hematology (NRCH, Moscow, Russia) for outpatient or remote consultations were suggested to prospectively report the AEs after getting a vaccination against COVID-19 by the most frequently used vector-based vaccine GamCovidVac (Sputnik V). Two vaccine components with the interval of 21 days were given at the vaccination facilities, as prescribed. At least after 3 weeks after the 2 nd injection, pts were advised to perform a blood test for the specific antibodies against spike (S) protein of SARS-CoV-2. A semi-quantitative test detecting the SARS-CoV-2 S1 subunit (RBD) IgG antibodies by enzyme-linked immunoassay (ELISA) kit was used in the clinic. The results were considered positive with the cutoff index >1,1. The use of any other lab tests detecting antibodies to S protein of SARS-CoV-2 was acceptable as well. Results. In total, 66 pts with chronic phase of CML received a vaccination by Sputnik V in the 7 months period (from 18.12.2020 to 20.07.2021). Me age was 54 years (range 29 - 89 years), 34 (52%) were males. Median (Me) CML duration was 8 years (from the moment of diagnostics up to 20 years). Fifty one (77%) pt received TKI therapy and 15 (23%) were off-therapy at the time of vaccination, including 12 (18%) in a treatment-free remission and 3 (4,5%) pts in the process of diagnosis. Deep and major molecular response (MMR) was in 46 (70%) and 7 (11%) pts, respectively. Two (3%) pts had a molecular response MR2, 11 (17%) had no MR2. Eight (12%) pts had a history of COVID-19 manifestation prior to vaccination. Me time for testing for the antibodies was 27 days (range 5-77) after the 2 nd vaccine injection. The tests were done in 44 (67%) of pts and revealed positive by any of the test systems in 42 (95%) pts. ELISA test was used in 30 (45%) pts and was positive in 25 (83%) of 30 pts. Me cutoff index in the positive samples was 7,7 (range 1,1 - 12) and corresponded to the value observed in healthy people after vaccination (medical stuff, data not shown). In all 3 pts with the history COVID 19, the index of positivity was above the Me value (Fig. 1, 2). Other test systems were used in 14 (21%) pts, in all 14 (100%) the antibodies were found. In 3 of 5 patients with the cutoff index A weak reverse correlation of the antibody levels with the time after vaccination was noted ( r = - 0,39, p = 0,033). A very weak reverse correlation with age was observed ( r = - 0,28, p = 0,127) (Fig. 1, 2). No AEs after the vaccination were observed in 25 (38%) pts while 41 (62%) pts reported the AEs and 7 (10%) pts did not report their reactions. The AEs were as follows: local pain/discomfort in the injection site in 19 (29%) pts, weakness and/or drowsiness in 20 (30%), fever and/or chills in 16 (24%), other reactions in 8 (12%) including headache, heartbeat, lower back pain, pain in limbs, activation of herpes infection. Conclusion: The single center study revealed no unusual or unexpected AEs in CML pts after the vaccination against COVID-19 by Sputnik V vaccine. The proportion of CML pts with specific antibodies after was 95% which is close to the published results of the 3rd phase study. No significant correlation was found with age (r = -0,28, p = 0,127), however, the absence or very low antibody levels were detected in individual patients aged about 60-70 years. This data raise a question of a necessity for a non-specific protection (masks, respirators, distance etc) and probably considering additional vaccination in some elderly persons. The duration of a humoral response against COVID-19, protective antibody titer and connection with clinical outcomes in CML pts need further evaluation in parallel with a common population. Figure 1 Figure 1. Disclosures Chelysheva: Pfizer: Speakers Bureau; Pharmstandart: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau; Novartis Pharma: Speakers Bureau. Petrova: Pfizer: Speakers Bureau; Novartis Pharma: Speakers Bureau. Gurianova: Pfizer: Speakers Bureau. Turkina: Pharmstandart: Speakers Bureau; Pfizer: Speakers Bureau; Novartis Pharma: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau.

Introduction Despite the availability of vaccination against COVID 19 for all population categories since January 2021, it is moving slowly in Russia. Patients (pts) with chronic myeloid leukemia (CML) usually lead a normal life with social interactions. In the context of the COVID 19 pandemic, we find it important to identify the factors of adherence to vaccination and clarify the concerns. Objective: To determine the proportion of CML pts willing to consider vaccination against COVID 19, adherence factors and reasons for not vaccinating. Materials and methods. A survey on the attitude to vaccination against COVID 19 was prospectively carried out among all pts with CML consulted at the outpatient department of National Research Center for Hematology (Moscow, Russia) who agreed to participate. The key questions included considerations for and against vaccination, socio-demographic and clinical characteristics, lifestyle, comorbidities and history of COVID 19. Results. Within 4 months (from March 15 to July 19, 2021), 172 CML pts completed the questionnaire. CML chronic phase, advanced phase and blast crisis were in 167 (97%), 4 (2%) and 1(1%) respectively. In total, 141 (82%) pts were on therapy with 1 st, 2 nd and >3 rd therapy line in 77 (55%), 33 (23%) and 31 (22%) pts, respectively. Thirty one (18%) had no therapy: 6 (3.5%) newly diagnozed, 25 (14.5%) in a treatment-free remission. A deep and major molecular response was in 77 (45%) and 30 (17%) pts, respectively. Presence and absence of molecular response MR2 was in 20 (12%) and 45 (26%) pts respectively. The median age of pts was 46 years (range 19-82), 75(44%) were males. Married 108 (63%), 70 (41%) lived with elderly relatives, 35 (20%) with children. A higher education was in 123 (72%) pts, 123 (72%) could not work remotely and 46 (27%) had interactions to people by work. Any comorbidity was in 89 (52%) pts, 42(24%) had >1 concomitant disease, 48 (28%) had cardiovascular diseases, 44 (26%) had an obesity. A history of COVID 19 was in 41 (24%) pts and in the close circle of 74 (43%) pts. Vaccination was supported by 94(55%) pts (with 29 (17%) already vaccinated) and not supported by 76 (44%) pts, 2 (1%) pts did not answer. Among those supporting vaccination vs not supporting there was significantly more males (52% vs 33%, p=0,012), married pts (73% vs 49%, p The two most common reasons to avoid vaccination were the fear of complications in 37(49%) pts and waiting for additional data in 19(25%) (Fig.1). Notably, 7 (9%) pts considered CML as a contraindication to vaccination. Among those supporting vaccination, 55(59%) preferred to choose the GamCovidVac (Sputnik V) vaccine, 20(21%) had no preference (Fig.2). Out of 32 pts who gave the rationale for the Sputnik V choice 19(59%) noted its best availability, study or popularity (Fig.3). Among 23 pts with additional questions 12 (52%) wondered about the possibility of vaccination with CML diagnosis and 6 (26%) asked help with a vaccine choice. Conclusion: Despite access to vaccines against COVID 19 with proven efficacy and safety, almost half of CML pts (44%) do not support vaccination. Socio-demographic factors such as gender, education, marriage status appeared to be significant for this decision. Considering the frequent concerns of the possibility of vaccination with CML diagnosis as well as the fear of complications, hematologists should provide a relevant clarifying information on these issues. Figure 1 Figure 1. Disclosures Chelysheva: Pfizer: Speakers Bureau; Novartis Pharma: Speakers Bureau; Pharmstandart: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau. Petrova: Pfizer: Speakers Bureau; Novartis Pharma: Speakers Bureau. Gurianova: Pfizer: Speakers Bureau. Kokhno: Novartis Pharma: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau. Turkina: Novartis Pharma: Speakers Bureau; Pfizer: Speakers Bureau; Pharmstandart: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau.

Background: The problem of resistance and intolerance to 2nd generation tyrosine kinase inhibitors (2G TKIs) in patients (pts) with chronic myeloid leukemia (CML) currently remains relevant. Ponatinib has demonstrated a high effectiveness and may be an option in CML pts with resistance or intolerance to available TKIs but the high incidence of vascular adverse events (AEs) limits its broad use. A STAMP (Specifically Targeting the ABL Myristoyl Pocket) inhibitor asciminib has demonstrated a superiority over bosutinib in CML pts previously treated with 2 or more TKIs (Phase III Study). Asciminib is available in Russia under the Managed Access Program (MAP) approved by Novartis. Aim: to present the first results of the use of asciminib in clinical practice under the MAP program in Russia. Methods: In total 46 CML pts from 3 Russian clinics were enrolled into the MAP program and received asciminib from September 2019 to June 2021 (1 pt started asciminib in a cinical trial and was transferred to MAP later). We analyzed therapy results of 32 pts who received asciminib for at least 3 months. Patient recruitment, dosing regimen, response monitoring, and toxicity control were performed according to the MAP treatment plan. Complete cytogenetic response (CCyR), major molecular response (MMR) and deep molecular response (MR4) rates were assessed by cumulative incident function (CIF). Differences between the subgroups were considered significant with p value ≤ 0.05 by the Gray's test. Results: Baseline characteristics: male: 41%; Меdian (Me) age 54 years (range 26-81); Me duration of CML before asciminib was 8 years (range 2-24); 23 pts were in chronic phase (CP) CML, 7 and 2 pts had a history of accelerated phase (AP) and blast crisis (BC), respectively, but were in a second CP at baseline. Nineteen (59%) pts had BCR-ABL mutations, 10 pts (31%) had BCR-ABLt315i clones, 7 (22%) pts had at least two mutations. Eight (25%) pts had additional chromosomal abnormalities (ACAs). Twenty one (66%) pts received ≥4 TKIs, 14 (44%) pts had a history of ponatinib treatment. Me duration of asciminib treatment at the time of analysis was 7 months (range 4-24), 4 (12.5%) pts discontinued asciminib due to lack of efficacy; all pts were alive. The initial asciminib dose was 40 BID in 22 (69%) pts and 200 mg BID in 10 (31%) pts. CCyR, MMR and MR4 at the time of analysis was achieved in 32% (8/25), 34% (10/29) and 17% (5/30) pts, respectively (considering pts without this kind of response at baseline). The 6 month CIF of CCyR, MMR and MR4 was 27%, 24% and 19%, respectively. Univariate analysis was performed in 29 pts without MMR at baseline evaluating the following factors of 6 month MMR achievement: initial dose of asciminib, CML phase, presence of BCR-ABL mutations and ACAs, best molecular response on previous TKIs, molecular response at the time of asciminib starting, history of ponatinib treatment, number of TKIs and duration of TKI therapy before asciminib. The duration and number of TKIs, the history of advanced phases, BCR-ABL kinase domain mutations and ACAs did not significantly effect on MMR rate (tab.1). BCR-ABL Fourteen (44%) of 32 pts had AEs of any grade and 7 (22%) had AEs of grade 3-4 (hematological AEs -6 (19%), non-hematological AE- 1 (3%)) (tab.2). Conclusion: Asciminib has shown promising efficacy and a good toxicity profile in a cohort of highly pre-treated CML pts and should be considered as a therapeutic option for CML pts resistant or intolerant to other TKIs. Figure 1 Figure 1. Disclosures Turkina: Bristol Myers Squibb: Speakers Bureau; Pfizer: Speakers Bureau; Pharmstandart: Speakers Bureau; Novartis Pharma: Speakers Bureau. Lomaia: Novartis: Honoraria; Pfizer: Honoraria; BMS: Honoraria; Pharmstandard: Honoraria. Petrova: Pfizer: Speakers Bureau; Novartis Pharma: Speakers Bureau. Chelysheva: Novartis Pharma: Speakers Bureau; Pharmstandart: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau; Pfizer: Speakers Bureau. Gurianova: Pfizer: Speakers Bureau.

Background: Not everyone with CML responds optimally to TKI-therapy, especially those with BCR::ABL1T315I. PF-114 is a 4 th-generation oral tyrosine kinase-inhibitor (TKI) active against wild-type and mutated BCR::ABL1 isoforms including BCR::ABL1T315I. We present final results of a phase-1 study (NCT02885766). Methods: 3+3 dose-escalation study to determine maximum tolerated dose (MTD) and dose-limiting toxicity (DLT). Secondary objectives included safety and efficacy based on haematological, cytogenetic and molecular response criteria. Adverse events (AEs) were graded using NCI-CTCAE v4.03. Results: 51 subjects (5 with accelerated phase CML, 46 - with chronic CML), 23 males, were studied. Daily doses were 50-600 mg/d given once daily continuously. Median age was 50 y (range, 29-82 y). Median CML duration pre-study was 10 y (range, 0.3-23 y). 16 subjects had BCR::ABL1T315I. 25 subjects received ≥ 3 prior TKIs. Median follow-up was ≥ 31 mo and median exposure, 6 mo (range, 0.4-52). Therapy was ongoing in 7 subjects at study termination. Others discontinued because of progression (n = 20), AEs (n = 2), consent withdrawal (n = 5), entry into another study (n = 3) or other reasons (n = 14). The MTD was 600 mg with the grade-3 psoriasis-like skin AE as the DLT. There were no vascular occlusive events or deviations of ankle-brachial index. Complete haematologic response (CHR) was achieved in 14 of 30 subjects, major cytogenetic response (MCyR) in 15 of 44 subjects, complete cytogenetic response (CCyR) in 11 of 50 subjects and major molecular response (MMR) in 8 of 51 subjects. Median duration of CHR was 12 mo and has not been reached for MCyR, CCyR and MMR. The best safety/efficacy dose was 300 mg/d with 6 of 9 subjects achieving a MCyR, 5, a CCyR and 4, MMR. 5 of 16 subjects with BCR::ABL1T315I responded, including 4 achieving a MCyR, 2, a CCyR and 1, a MMR. 2 of 6 subjects failing ponatinib achieved a CHR. Conclusion: PF-114 was safe and effective in subjects failing ≥ 2 TKIs and those with BCR::ABL1T315I including those failing ponatinib. The PF-114 dose for further study is 300 mg/d. Disclosures Turkina: Bristol Myers Squibb: Speakers Bureau; Pfizer: Speakers Bureau; Pharmstandart: Speakers Bureau; Novartis Pharma: Speakers Bureau. Vinogradova: Bristol Myers Squibb: Speakers Bureau; Novartis Pharma: Speakers Bureau; Pfizer: Speakers Bureau; Pharmstandart: Speakers Bureau. Lomaia: Novartis: Honoraria; Pfizer: Honoraria; BMS: Honoraria; Pharmstandard: Honoraria. Chelysheva: Pfizer: Speakers Bureau; Novartis Pharma: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau; Pharmstandart: Speakers Bureau. Petrova: Pfizer: Speakers Bureau; Novartis Pharma: Speakers Bureau. Cortes: Bio-Path Holdings, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sun Pharma: Consultancy, Research Funding; Takeda: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Bristol Myers Squibb, Daiichi Sankyo, Jazz Pharmaceuticals, Astellas, Novartis, Pfizer, Takeda, BioPath Holdings, Incyte: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Baccarani: Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Ottmann: Fusion: Honoraria; Incyte: Honoraria, Research Funding; Amgen: Honoraria, Research Funding; Celgene/BMS: Honoraria, Research Funding; Novartis: Honoraria. Mikhailov: Fusion Pharma: Current Employment. Novikov: Fusion Pharma: Current Employment. Shulgina: Fusion Pharma: Current Employment. Chilov: Fusion Pharma: Current Employment.

To assess the results of following up patients with chronic myeloid leukemia (CML) and a deep molecular response (MR) without tyrosine kinase inhibitor (TKI) therapy.The reasons for TKI discontinuation in 70 patients with CML and a deep MR of more than 1 year's duration were adverse events, pregnancy, and patients' decision. Information was collected retrospectively and prospectively in 2008-2016.The median follow-up after TKI therapy discontinuation was 23 months (2 to 100 months). At 6, 12 and 24 months after TKI therapy discontinuation, the cumulative incidence of major MR (MMR) loss was 28, 41 and 48%, respectively; the survival rates without TKI therapy were 69, 50, and 39%, respectively. MMR loss was noted in 28 (88%) patients at 12 months; it was not seen without TKI therapy at 2-year follow-up. Deaths due to CML progression were absent. The Sokal risk group was a reliable factor influencing MMR loss (p ≤ 0.05). The cumulative recovery rate for deep MR after resumption of TKI use was 73 and 100% at 12 and 24 months, respectively, with a median follow-up of 24 months (1 to 116 months). Deep MR recovered at a later time when the therapy was resumed more than 30 days after MMR loss.Safe follow-up is possible in about 50% of the patients with CML and stable deep MRs without TKI therapy. The introduction of this approach into clinical practice requires regular molecular genetic monitoring and organizational activities. Biological factors in maintaining remission after TKI discontinuation need to be separately studied.Цель исследования. Оценка результатов наблюдения больных хроническим миелолейкозом (ХМЛ) с глубоким молекулярным ответом (МО) без терапии ингибиторами тирозинкиназ (ИТК). Материалы и методы. Причинами отмены ИТК у 70 больных ХМЛ с длительностью глубокого МО более 1 года служили нежелательные явления, беременность, собственное решение больных. Сбор информации осуществлялся ретроспективно и проспективно в 2008-2016 гг. Результаты. Медиана времени наблюдения после отмены терапии ИТК составила 23 мес (от 2 до 100 мес). Кумулятивная частота потери большого молекулярного ответа (БМО) после прекращения терапии ИТК через 6, 12 и 24 мес составила 28, 41 и 48% соответственно, выживаемость без терапии ИТК - 69, 50 и 39% соответственно. У 28 (88%) пациентов потеря БМО отмечена в течение 12 мес; после 2 лет наблюдения без терапии ИТК потери БМО не отмечалось. Летальные исходы от прогрессии ХМЛ отсутствовали. Группа риска по Sokal являлась достоверным фактором, влияющим на потерю БМО (p≤0,05). Кумулятивная частота восстановления глубокого МО после возобновления приема ИТК составляла 73 и 100% через 12 и 24 мес соответственно при медиане наблюдения 24 мес (от 1 до 116 мес). Восстановление глубокого МО наблюдалось позднее при возобновлении терапии более, чем через 30 дней после потери БМО. Заключение. Примерно у 50% больных ХМЛ со стабильным глубоким МО возможно безопасное наблюдение без терапии ИТК. Для внедрения этого подхода в клиническую практику необходимы обеспечение регулярного молекулярно-генетического контроля и организационные меры. Биологические факторы сохранения ремиссии после отмены ИТК нуждаются в отдельном изучении.

Background The criteria of molecular relapse in different treatment-free remission (TFR) trials in patients (pts) with chronic myeloid leukemia (CML) varied. In the early trials molecular relapse was defined as loss of deep molecular response (DMR) including MR4 loss. In recent ELN guideline (Hochhaus et al, 2020) major molecular response (MMR) loss was a criterion of molecular relapse. We consider it reasonable to evaluate the role of MR4 loss in connection with MMR loss and time of treatment-free observation and to describe the pattern of minimal residual disease (MRD) in this context. Aim To evaluate the role of MR4 loss on further MMR loss in CML pts during early and late period after TKI cessation and to describe the pattern of MRD during TFR. Patients and methods In total 98 CML pts with chronic phase who had received therapy by any TKI ≥3 years (yrs) with sustained DMR (at least MR4 or BCR-ABL ≤0.01% by international scale (IS)) during ≥2 yrs) were enrolled into the prospective TFR study RU-SKI. The BCR-ABL level (IS) was evaluated by RQ-PCR monthly during the first 6 months (mo) after TKI cessation, every 2 mo from 6 to 12 mo and every 3 mo thereafter. MR4 loss was considered if BCR-ABL was >0,01% and 0,1%). Molecular relapse free survival (MRFS) was evaluated by Kaplan-Meier method, log-rank test was used for comparison. Results Меdian (Me) time after TKI discontinuation was 40 mo (range 28-57). MMR loss and MR4 loss was observed in 48(49%) and 38(39%) pts respectively. In 42(87%) pts MMR loss was observed within first 6 mo after treatment cessation. MRFS at 36 mo was 51% (95% CI 41 - 61%). No MMR loss occurred in 10(26%) pts with MR4 loss while 28(74%) pts with MR4 loss subsequently lost MMR. The MRFS after the first documented MR4 loss was 29% (95% CI 15 - 44%) and 24% (95% CI 10,5 - 38%) at 12 and 24 mo respectively. MRFS at 24 mo was significantly higher in pts with late MR4 loss (>3 mo) than in pts with early MR4 loss ( The pattern of MRD in 50 pts who continued a treatment-free observation after TKI cessation was represented by 3 main variants: 1) stable undetected MRD in 17(34%) pts; 2) transient short-term or long-term fluctuations without MR4 loss in 23(46%) pts; 3) fluctuations with transient MR4 loss but without MMR loss in 10(20%) pts (figure 2). Interestingly, 8 of 10 pts with MR4 fluctuations subsequently achieved MRD-negative status. Conclusion We confirmed that MR4 loss after TKI cessation in most cases (74%) preceded the molecular relapse which was considered as MMR loss. However, the MRFS was significantly higher in pts with late MR4 loss than in those with early MR4 loss during the first 3 mo of TKI cessation and comparable with MRFS in the whole pts cohort. We found that only 34% pts who maintained a molecular remission had stable undetected MRD while 66% of pts had fluctuations of MRD during TFR. About a quarter of pts (26%) with MR4 loss could remain in TFR and achieve the MRD-negative status. We support the importance of regular MRD monitoring both in early and late terms during TFR observation to benefit for the safety of the pts. Disclosures Chelysheva: Novartis: Other: performed lectures; Fusion Pharma: Consultancy. Shukhov:Novartis: Consultancy, Other: performed lectures; Pfizer: Consultancy, Other: performed lectures. Ionova:BMS: Other: principal investigator of the observational studies sponsored by BMS; Takeda: Other: principal investigator of the observational studies sponsored by Takeda. Turkina:Pfizer: Honoraria; Novartis Pharma: Honoraria; BMS: Honoraria.

We aimed to characterize withdrawal syndrome (WS) and evaluate factors associated with its development in the prospective clinical study RU-SKI in patients with chronic myeloid leukemia with deep molecular response who discontinued tyrosine kinase inhibitor (TKI) therapy. In total, 98 adult patients with chronic myeloid leukemia chronic phase, TKI therapy ≥ 3 years, and deep molecular response (BCR-ABL ≤ 0.01%) ≥ 2 years were enrolled and observed without treatment. WS was defined as newly observed or worsening musculoskeletal pain after TKI cessation. WS symptoms were found in 41 (42%) of 98 patients with a median time of observation of 25 months (range, 12-42 months). WS grades 1 to 2 and grade 3 were observed in 39 (95%) and in 2 (5%) patients, respectively. The median duration of WS was 5 months (range, 1-25 months). WS was resolved in 37 (90%) patients. Anti-inflammatory therapy was used in 21 (51%) patients. Older age (P = .039) and longer TKI therapy (P = .001) were associated with WS. The 2-month landmark analysis found no association of WS development and the rate of molecular relapses. In total, 42% of the patients experienced WS after TKI therapy discontinuation in the RU-SKI study. Physicians should be warned about the possibility of WS development, and patients of older age and with longer TKI treatment need special attention.

We analyzed changes in multipotent mesenchymal stromal cells of patients with chronic myeloid leukemia before discontinuation of tyrosine kinase inhibitors. Withdrawal syndrome was significantly more common in patients who have been taking tyrosine kinase inhibitors for a longer time and in patients of older age and with lower body weight. In patients with withdrawal syndrome, the total production of mesenchymal stromal cells and expression of FGFR2 and MMP2 genes were significantly lower; loss of deep molecular response was also less frequent in this group of patients. At the same time, the expression of genes important for the maintenance of stem cells (SOX9, PDGFRa, and LIF) was significantly lower in the mesenchymal stromal cells of patients with withdrawal syndrome and loss of deep molecular response. We observed a clear-cut relationship between the development of withdrawal syndrome and the loss of deep molecular response. The decrease in the expression of FGFR2 and MMP2 genes in the mesenchymal stromal cells of patients with chronic myeloid leukemia before discontinuation of treatment can be a predictor of withdrawal syndrome, while simultaneous decrease in the expression of SOX9, PDGFRa, and LIF in these cells attests to undesirability of therapy discontinuation at the moment.

Aim To define the prognostic factors for molecular relapse-free survival (MRFS) after TKI discontinuation in the Russian CML population. Methods The base for the analysis was the Russian multicenter prospective study RU-SKI on the discontinuation of TKI in patients (pts) with CML and deep molecular response (DMR). Ninety-eight CML pts with chronic-phase, TKI therapy for at least three years and a stable DMR (BCR-ABL Results Three-year MRFS rate was 51%. Baseline pts characteristics: male - 50%; median (Me) age at TKI cessation 46 years (range, 22 to 80); Me duration of TKI therapy 8.3 years (range, 3 to 16.2); Me duration of DMR 3.2 years (range, 2 to 10.7). Therapy before treatment cessation: imatinib in 67 (68.4%) pts, second-generation (2G) TKI in 31 (31.6%) pts. Me follow-up time after TKI cessation was 40 mo (range, 28 to 57). Probability of MRFS (1st stop) was 53% after 36 mo of follow-up. Length of DMR, duration of therapy and depth of molecular response were found to be significant factors with p ≤ 0.05. We have found that the duration of TKI therapy, and not the duration of DMR, has an independent prognostic value for the Russian CML population due to the lack of molecular monitoring data at early stages of the disease. No difference in 36 months MRFS was observed in 1st-line imatinib (55%) compared with 1st-line 2G TKI (70%; p=0.26) and 2nd-line 2G TKI (39%; p=0,09) groups. However, significantly shorter treatment duration was observed in pts treated with 1st-line 2G TKI (Me=41.5 mo) vs imatinib (Me=96.4 mo), p Conclusion Longer treatment duration and depth of DMR before cancellation at least MR 4.5 are associated with durable TFR. Our study showed that the MRFS rate is not significantly improved with the use of 1st-line 2G TKI in comparison with 1st-line imatinib.

Background The data on quality of life (QoL) in chronic myeloid leukemia (CML) patients (pts) with deep molecular response (DMR) in the treatment-free remission (TFR) studies are limited. The influence of comorbidities on QoL in CML pts before and after tyrosine kinase inhibitors (TKIs) discontinuation has not been studied. Aim We aimed to study the impact of comorbidities on QoL in CML pts before and after the stop therapy by TKIs. Patients and methods The chronic phase (CP) CML pts who had received therapy by any TKI ≥3 years (yrs) with sustained DMR (BCR-ABL ≤0.01% IS) during ≥2 yrs were enrolled into the prospective TFR study RU-SKI. A regular qPCR with BCR-ABL IS evaluation was performed after TKI cessation. TKI were resumed in pts with major molecular response loss (MMR loss, BCR-ABL>0,1%). The QoL was evaluated by RAND SF-36 questionnaire at baseline before TKI stop and at 1, 3, 6, 12 mo during TFR. Eight functional scales were assessed: physical functioning, role limitations physical, bodily pain, general health perceptions, energy/vitality, social functioning, role limitations emotional, mental health. The Integral QoL Index (IQoLI) was calculated based on the scales. Mann-Whitney test, paired Wilcoxon test χ2 were used for the statistical analysis. Molecular relapse free survival (MRFS) was evaluated by Kaplan-Meier method, log-rank test was used for comparison. Results The analysis was performed in the group of 97 CML pts. Median (Me) age was 47±14.5 (yrs), 48.5% were males. The TKI before treatment cessation were as follows: imatinib and second-generation (2G) TKIs in 67 (70%) and 30 (30%) pts accordingly; 9 (30%) pts received 2G TKIs in 1st line and 21 (70%) pts in 2nd line. Me time of observation was 25 mo (range 12-42). Comorbidities were present in 81 pts (82%) at baseline. The most frequent comorbidities were cardiovascular (38.4%), gastroenterological (29.3%) and musculoskeletal disorders (27.3%). First we compared baseline QoL in 2 pts groups: group 1 - pts with acute comorbidity status at baseline (n=42), group 2 - pts with stable comorbidity status (n=29) and with no comorbidity (n=16). QoL in group 1 was significantly worse by all functional scales, except mental health (p Then we evaluated QoL at 3 mo after TKI stop in 72 available pts, as acute status comorbidity remained in 30 pts. The majority of pts exhibited QoL improvement or stabilization by all SF-36 scales. The most pronounced positive changes were observed by SF-36 scales in pts with acute comorbidity status (group 1).The proportion of pts with QoL improvement at 3 mo after TKI stop was higher in group 1 as compared to group 2 by physical functioning (57% vs 29%), role physical functioning (30% vs 5%) and social functioning (40% vs 24%), p MRFS at 24 mo was 62% (CI 46-77%) and 45% (CI 32-58%) in groups 1 and 2 respectively, with no significant differences between the groups (p=0.107). Conclusion CML pts with DMR and acute comorbidity status had a worse QoL before TKI therapy cessation compared to pts without comorbidity or with comorbidity in remission. The majority of pts exhibited QoL improvement or stabilization in early terms after TKI stop. Pts with acute comorbidity status had more pronounced positive QoL changes after treatment cessation than other pts. Possible explanation is that TKI therapy could increase the clinical symptoms manifestation by overlapping with the treatment toxicity effects. The molecular relapse rate was similar in pts with and without acute comorbidity status. Thus, comorbidity is not a factor which may have negative impact on the outcomes of stop TKI therapy in CML pts. Disclosures Ionova: Takeda, BMS: Other: Principal Investigator of IISR, Research Funding. Chelysheva:Novartis: Consultancy, Honoraria; Fusion Pharma: Consultancy. Shukhov:Novartis: Consultancy; Pfizer: Consultancy. Turkina:Novartis: Consultancy, Speakers Bureau; Pfizer: Consultancy; Bristol Myers Squibb: Consultancy; fusion pharma: Consultancy; Novartis: Consultancy, Speakers Bureau.

Background: PF-114 is a 4th-generation oral tyrosine kinase-inhibitor (TKI) active against wild-type and mutated BCR-ABL1 isoforms including BCR-ABL1T315I. We present data from a phase-1 study in patients with chronic or accelerated phase chronic myeloid leukaemia (CML) failing ≥2 TKIs or with BCR-ABL1T315I (NCT02885766) with ≥6 months therapy. Methods: 3+3 dose-escalation study to determine maximum tolerated dose (MTD) and dose-limiting toxicity (DLT). Secondary objectives included safety and efficacy based on haematological, cytogenetic, and molecular criteria. Adverse events (AEs) were graded using NCI-CTCAE v4.03. Results: 51 patients were enrolled. Daily doses were 50 mg (n=3), 100 mg (n=3), 200 mg (n=9), 300 mg (n=11), 400 mg (n=12), 500 mg (n=3), 600 mg (n=6), 750 mg (n=4) given continuously. Median age was 50 years (range, 29-82 years). Median CML duration pre-study was 10 years (range, 0.3-23 years). All patients had baseline ECOG performance scores 0-1. Twelve patients had BCR-ABL1T315I. Patients were heavily pre-treated: 25 received ≥3 prior TKIs; 5 patients with BCR-ABL1T315I received 1 prior TKI. Interim analysis was conducted at follow-up of ≥6 months (cut-off date January 16th 2019). Therapy was ongoing in 17 patients at doses 200 mg (n=4), 300 mg (n=9), 400 mg (n=3) and 600 mg (n=1) with median duration of exposure of 7,4 (range, 4,6-26), 9,2 (range, 7,4-26), 9,2 (range, 8,3-9,2) and 9,2 months. Other patients discontinued because of progression (n=18), adverse events (n=6), consent withdrawal (n=4), participation in another study (n=3) or other reasons (n=3). The MTD was 600 mg with the grade-3 psoriasis-like skin lesions the DLT, which occurred during the first 28 days of treatment. Reversible grade-3 skin toxicity occurred in 11 patients at doses ≥400 mg. There were no other drug-related non-hematologic grade-3 toxicities except 1 grade-3 toxic hepatitis at 400 mg and there were no detectable effects on ankle-brachial index or vascular occlusive events. The best safety/efficacy dose was 300 mg/d with 6 of 11 patients achieving a major cytogenetic response (MCyR) and 4 of them - a major molecular response (MMR). Higher doses were less effective probably because of toxicity-related therapy interruptions and discontinuations. Five of 12 patients with BCR-ABL1T315I responded, 3 of which achieved a complete hematologic response and 4 achieved MCyR. Conclusion: PF-114 was safe and effective in patients with CML failing ≥2 TKIs or with BCR-ABL1T315I. The most effective dose was 300 mg/d. Five of 12 patients with BCR-ABL1T315I responded. A pivotal study is beginning. Disclosures Turkina: Novartis: Consultancy, Speakers Bureau; Pfizer: Consultancy; Bristol Myers Squibb: Consultancy; fusion pharma: Consultancy; Novartis: Consultancy, Speakers Bureau. Vinogradova:Novartis: Consultancy; Fusion Pharma: Consultancy. Lomaia:Novartis: Other: Travel Grant;Lecture fee; Pfizer: Other: Travel Grant. Shukhov:Pfizer: Consultancy; Novartis: Consultancy. Chelysheva:Novartis: Consultancy, Honoraria; Fusion Pharma: Consultancy. Shikhbabaeva:Novartis: Consultancy; Fusion Pharma: Consultancy. Shuvaev:Fusion Pharma: Consultancy; Novartis: Consultancy; Pfize: Honoraria; BMS: Consultancy. Cortes:Pfizer: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Research Funding; Novartis: Consultancy, Honoraria, Research Funding; Daiichi Sankyo: Consultancy, Honoraria, Research Funding; Biopath Holdings: Consultancy, Honoraria; Immunogen: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Research Funding; Astellas Pharma: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Research Funding; BiolineRx: Consultancy; Sun Pharma: Research Funding; Merus: Consultancy, Honoraria, Research Funding; Forma Therapeutics: Consultancy, Honoraria, Research Funding. Baccarani:Novartis: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Takeda: Consultancy. Ottmann:Roche: Honoraria; Pfizer: Honoraria; Fusion Pharma: Honoraria; Takeda: Honoraria; Novartis: Honoraria; Celgene: Honoraria, Research Funding; Incyte: Honoraria, Research Funding; Amgen: Honoraria, Research Funding. Mikhailov:Fusion Pharma: Employment. Novikov:Fusion Pharma: Employment. Shulgina:Fusion Pharma: Employment. Chilov:Fusion Pharma: Consultancy.

Background It is reasonable to incorporate quality of life (QoL) assessment into the comprehensive evaluation of treatment outcomes in chronic myeloid leukemia (CML) patients (pts) with deep molecular response (DMR) who enter the treatment-free remission (TFR) phase and stop therapy by tyrosine kinase inhibitors (TKIs). QoL assessment was included into the design of Russian prospective multicenter trial RU-SKI along with the clinical outcomes evaluation. Aim To study QoL in chronic phase (CP) CML pts with DMR before stopping TKI treatment and during TFR observation. Materials and methods The study has been conducted within the clinical approbation supported by the Ministry of Health of RF. The CML CP pts with therapy by any TKI ≥ 3 years (yrs) and stable DMR (BCR-ABL ≤0.01% IS) during ≥2 yrs were enrolled. Pts who met these criteria and had previous resistance to any TKI were also eligible. TKIs were resumed in case of major molecular response loss (MMR, BCR-ABL>0,1%). The QoL questionnaires RAND SF-36 and EORTC QLQ C30 were filled out by the pts before stopping TKI treatment and at 1, 3, 6 and 12 months (mo) after treatment discontinuation. The comparison group consisted of healthy persons matched by age and gender to CML CP pts (n=97). The Mann-Whitney test, paired Wilcoxon test and Generalized Estimation Equations (GEE) with adjustment to age, gender, the risk group according to Sokal score and duration of TKI treatment were used for the statistical analysis. Results QoL assessment was performed in all 99 CML CP pts who were enrolled into the trial during a period from Aug 2015 till Dec 2017. The TKIs before treatment cessation were as follows: imatinib and second-generation (2G) TKIs were used in 69(70%) and 30(30%) pts accordingly. 2G TKIs were used in 9(30%) and in 21(70%) pts as 1st and 2nd line accordingly. Mean age was 47±14.5 yrs, 48.5% were males, 12.1% had high Sokal risk score. The physical functioning of CML pts before stopping TKI treatment compared to the healthy controls was significantly worse (p0.05). Conclusion The QoL in CML CP pts with DMR on TKI treatment is slightly worse and physical functioning is significantly lower as compared to healthy controls. The positive changes of the role functioning along with TKI treatment-related symptoms decrease were revealed in pts who maintained stable MMR during 12 mo of TFR. No changes in QoL and no new symptoms were found in pts who reinitiated treatment before and after TKIs interruption. The results of QoL assessment may contribute to optimization of the treatment strategies of CML patients with DMR. Disclosures Chelysheva: Fusion Pharma: Other: provided consultations ; Bristol Myers Squibb: Other: provided consultations and performed lectures; Novartis: Other: provided consultations and performed lectures. Shukhov:Bristol Myers Squibb: Other: provided consultations and performed lectures ; Novartis: Other: provided consultations and performed lectures . Turkina:Novartis: Other: provided consultations; Bristol Myers Squibb: Other: provided consultations; Phizer: Other: provided consultations; Fusion Pharma: Other: provided consultations. Ionova:Takeda: Research Funding; BMS: Research Funding.

Background: PF-114 mesylate is a 4th-generation oral tyrosine kinase-inhibitor (TKI) active against wild-type and mutated BCRABL1 isoforms including those with a BCRABL1T315I. We present data from a phase-1 study in subjects with chronic or accelerated phase chronic myeloid leukaemia (CML) failing ≥2 TKIs or who have BCRABL1T315I (NCT02885766). Methods: 3+3 dose-escalation design to determine maximum tolerated dose (MTD) followed by expanded cohorts for doses ≤MTD. The primary objective was to determine the MTD and identify dose-limiting toxicities (DLTs) during cycle 1 (28 days). Secondary objectives included safety and anti-CML activity based on hematological, cytogenetic, and molecular criteria. Adverse events (AEs) were assessed and graded using NCI-CTCAE v4.03. Results: 51 subjects were enrolled as of June 26, 2018. Daily doses were 50 mg (n=3), 100 mg (n=3), 200 mg (n=9), 300 mg (n=11), 400 mg (n=12), 500 mg (n=3), 600 mg (n=6), 750 mg (n=4) given on a continuous QD schedule. Median age was 50 years (range, 29-82 years). Median interval from diagnosis to study-entry was 10 years (range, 0-23 years). Subjects had baseline ECOG performance scores Conclusion: MTD of PF-114 is 600 mg with skin toxicity as the DLT. The best safety/efficacy ratio was seen at doses of 200 and 300 mg which are being studied in expanded cohorts and soon in a phase-2 study. Disclosures Turkina: Novartis: Other: provided consultations; Bristol Myers Squibb: Other: provided consultations; Phizer: Other: provided consultations; Fusion Pharma: Other: provided consultations. Shukhov:Novartis: Other: provided consultations and performed lectures ; Bristol Myers Squibb: Other: provided consultations and performed lectures . Chelysheva:Bristol Myers Squibb: Other: provided consultations and performed lectures; Fusion Pharma: Other: provided consultations ; Novartis: Other: provided consultations and performed lectures. Cortes:Daiichi Sankyo: Consultancy, Research Funding; Astellas Pharma: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Arog: Research Funding. Ottmann:Novartis: Consultancy; Pfizer: Consultancy; Takeda: Consultancy; Amgen: Consultancy; Celgene: Consultancy, Research Funding; Incyte: Consultancy, Research Funding; Fusion Pharma: Consultancy, Research Funding. Mikhailov:Fusion Pharma: Employment. Novikov:Fusion Pharma: Employment. Shulgina:Fusion Pharma: Employment. Chilov:Fusion Pharma: Employment.

Background: A large number of tyrosine kinase inhibitors (TKI) discontinuation studies has shown that about 50% of chronic myeloid leukemia (CML) patients (pts) after TKI cessation lose a major molecular response (MMR) and should return to therapy. Despite the fact that, after TKI resumption, almost all patients re-achieve deep molecular remission, facilitating a more accurate selection process for therapy cessation remains topical. Aim: Develop a prognostic model for the better selection of CML patients for TKI discontinuation. Methods: The base for the training set was the Russian multicenter prospective study RU-SKI on the discontinuation of TKI in pts with CML and deep molecular response (DMR). Ninety-eight CML pts with chronic phase (CP), TKI therapy for at least three years and a stable DMR (BCR-ABL0.1%). We used the Kaplan-Meier method for calculating the probability of TFR. Univariate analyses were performed using the log-rank test to identify prognostic factors for TFR. Variables found to be significant at the p Results: Baseline characteristics of the training set (n=91): male: 48%; median (Mе) age at TKI cessation 46 years (range 22 to 80); Me duration of TKI therapy 8.3 years (range three to 16.2); Me duration of DMR 3.2 years (range two to 10.7). Therapy before treatment cessation: imatinib in 63 (69%) pts, second-generation (2G) TKI in 28 (31%) pts. Me follow-up time after TKI cessation was 14 mo (range three to 36). Probability of TFR was 55% after 12 mo of follow-up. We analyzed the following factors: age, gender, history of previous resistance to imatinib, type and line of TKI, duration of therapy, length of DMR, depth of molecular response before cancellation, Sokal risk group. Age, Sokal risk group, duration of therapy and depth of molecular response were found to be independently significant factors and included in the survival prognostic model (Table 1). 73% (n=66) of pts scored 5.5 points or less and were assigned to the low risk group. The probability of TFR was 64% and 33% for the low risk and high risk groups, respectively (p=0.001) (Figure 1). Baseline characteristics of validation set (n=48): male: 36%; Ме age at TKI cessation 46 years (range 22 to 76); Me duration of TKI therapy six years (range 3.5 to 13.2); Me duration of DMR 2.8 years (range two to 10). Therapy before treatment stopped: imatinib in 31 (65%) pts, 2G TKI in 17 (35%) pts. Me follow-up time after TKI cessation was 36 mo (range six to 116). Probability of TFR was 47% after 30 mo of follow-up. In the validation set, 77% (n=37) of pts were assigned to the low risk group. The probability of TFR was 56% and 18% for the low risk and high risk groups, respectively (p=0.007) (Figure 2). Conclusion: RU-SKI prognostic model is effective in prediction of successful TFR and can be used for better selection of CML pts for TKI discontinuation. Disclosures Shukhov: Novartis: Other: provided consultations and performed lectures ; Bristol Myers Squibb: Other: provided consultations and performed lectures . Chelysheva:Novartis: Other: provided consultations and performed lectures; Fusion Pharma: Other: provided consultations ; Bristol Myers Squibb: Other: provided consultations and performed lectures. Turkina:Novartis: Other: provided consultations; Bristol Myers Squibb: Other: provided consultations; Phizer: Other: provided consultations; Fusion Pharma: Other: provided consultations.

Background: PF-114 mesylate is a novel third generation oral tyrosine kinase inhibitor (TKI) that blocks native and mutated Bcr-Abl isoforms, including the gatekeeper mutant T315I, which is uniformly resistant to all approved first- and second generation TKIs. At the present time extensive pre-clinical studies of PF-114, including mechanism of action, kinase profiling, in vitro and in vivo efficacy, safety pharmacology, ADME, and toxicology studies in mice, rats and dogs have been completed and supported initiation of phase I clinical trial of PF-114 mesylate in patients with chronic or accelerated phase Ph+ CML who are resistant to at least one of the second generation TKIs or intolerant to previous treatment with TKIs or who have T315I mutation in the BCR-ABL gene (NCT02885766). Methods: The trial represents a classical 3+3 design of dose escalation till the maximum tolerated dose (MTD) followed by the expanded cohorts planned for dose(s) below the MTD. The total expected enrollment is 44 patients. Escalating doses of single-agent PF-114 mesylate were administered orally on a continuous once daily (QD) dosing schedule. Treatment continued until disease progression, unacceptable toxicity, consent withdrawal, or death. The primary objective was to study the dose-limiting toxicities (DLTs) occurring in cycle 1 of treatment and determine the MTD. Secondary objectives included safety, anti-CML activity (based on hematologic, cytogenetic, and molecular assessments), pharmacodynamic and pharmacogenetic properties. Adverse events (AEs) were assessed and graded according to NCI-CTCAE v4.03. Results: At data cutoff, 4-dose cohorts - 50 mg, 100 mg, 200 mg and 400 mg have completed cycle 1 and 500 mg cohort has started cycle 1 of treatment. Overall 18 patients (8 males) had been treated at the following QD doses: 50 mg (n = 1), 200 mg (n = 5), 400 mg (n = 11), 500 mg (n = 1), and the MTD has not yet been reached. A total of 7 patients with T315I mutation were included into the trial thus far. Median age was 50.5 years (range, 32-66 years). Median time from diagnostics to treatment was 11.5 years (range, 16-1 years) All patients had baseline Eastern Cooperative Oncology Group performance status 0-1. Patients were heavily pretreated; 9 (50%) had received ≥ 3 prior TKIs, 6 (33%) had received 2 prior TKIs and 3 (17%) patients with T315I had received 1 prior TKI. In 11 patients, treatment is ongoing at doses 200-500 mg QD, with median duration of exposure of 8 months (range, 2-12 months), and 7 patients discontinued (disease progression [n = 5], AEs [n = 2]). Preliminary data suggest PF-114 pharmacokinetics is dose-proportional. At the end of cycle 1 of study therapy, no drug-related adverse events greater than grade 1 in severity were observed in patients treated at the 50 mg, 100 mg and 200 mg dose levels. At the dose of 400 mg QD, a single DLT case of grade 3 erythematous rash was observed. Most common grade 2/3 AEs on 400 mg QD were dermatologic toxicity (4/11), neutropenia (1/11). No deterioration of the ankle-brachial index (ABI), which is being prospectively measured, or vascular occlusive events were observed so far. The patient with recurrent pleural effusions on previous treatment with dasatinib did not reveal effusions after 11 cycle of therapy; the patient with ischemic stroke on previous treatment with nilotinib did not reveal cardio-vascular events after 9 cycles. To date, no SAEs have been reported. Overall, during the period of 3 cycles, major cytogenetic response (CyR) have been obtained in 4 of 11 patients who completed 3 cycles (2 cases of complete CyR in and 2 cases of partial CyR). Of those patients who revealed cytogenetic response two patients have T315I mutation. Pharmacodynamic and pharmacogenetic assessments are underway. Conclusion: PF-114 mesylate exhibits antitumor activity in a heavily pretreated subgroup of patients with resistant forms of CML including cases with T315I mutation. The evaluation of the safety profile continues. The dose escalation stage of the current phase 1 study continues, while the including of patients into the expanded cohorts with doses below the MTD has already started. Disclosures Chelysheva: Fusion Pharma LLC: Consultancy. Nemchenko: Fusion Pharma LLC: Consultancy. Zaritskey: Janssen: Consultancy; Novartis: Consultancy, Speakers Bureau. Shuvaev: Fusion Pharma LLC: Consultancy. Novikov: Fusion Pharma LLC: Employment. Shulgina: Fusion Pharma LLC: Employment. Chilov: Fusion Pharma LLC: Employment, Patents & Royalties.