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Background The development of molecularly tailored therapeutic agents such as the BCR/ABL-active tyrosine kinase inhibitors (TKi) resulted in an excellent treatment option for chronic myeloid leukemia (CML) patients. However, following TKi discontinuation, disease relapses in 40–60% of patients, an occurrence very likely due to the persistence of leukemic stem cells that are scarcely sensitive to TKi. Nevertheless, TKi are still the only current treatment option for CML patients. Objective The aim of this study was to compare the effects of TKi belonging to different generations, imatinib and ponatinib (first and third generation, respectively), on progenitor/stem cell expansion potential and markers. Patients and Methods We used stabilized CML cell lines (KCL22, K562 and LAMA-84 cells), taking advantage of the previous demonstration of ours that cell lines contain cell subsets endowed with progenitor/stem cell properties. Primary cells explanted from CML patients were also used. The effects of TKi on the expression of stem cell related genes were compared by quantitative PCR. Flow cytometry was performed to evaluate aldehyde-dehydrogenase (ALDH) activity and the expression of cluster of differentiation (CD) cell surface hematopoietic stem cell markers. Progenitor/stem cell potential was estimated by serial colony formation ability (CFA) assay. Results Ponatinib was more effective than imatinib for the reduction of cells with ALDH activity and progenitor/stem cell potential of CML patient-derived cells and cell lines. Furthermore, ponatinib was more effective than imatinib in reducing the percentage of CD26-expressing cells in primary CML cells, whereas imatinib and ponatinib showed similar efficacy on KCL22 cells. Both drugs strongly upregulated NANOG and SOX2 in CML cell lines, but in KCL22 cells this upregulation was significantly lower with ponatinib than with imatinib, an outcome compatible with a lower level of enrichment of the stem cell compartment upon ponatinib treatment. Conclusion Ponatinib seems to target CML progenitor/stem cells better than imatinib. Electronic supplementary material The online version of this article (10.1007/s11523-020-00741-x) contains supplementary material, which is available to authorized users.

Limited information is available on the impact of the COVID-19 pandemic on the management of chronic myeloid leukaemia (CML). The Campus CML network collected retrospective information on 8665 CML patients followed at 46 centres throughout Italy during the pandemic between February 2020 and January 2021. Within this cohort, we recorded 217 SARS-CoV-2-positive patients (2·5%). Most patients (57%) were diagnosed as having SARS-CoV-2 infection during the second peak of the pandemic (September 2020 to January 2021). The majority (35%) was aged between 50 and 65years with a male prevalence (73%). Fifty-six percent of patients presented concomitant comorbidities. The median time from CML diagnosis to SARS-CoV-2 infection was six years (three months to 18years). Twenty-one patients (9·6%) required hospitalization without the need of respiratory assistance, 18 (8·2%) were hospitalized for respiratory assistance, 8 (3·6%) were admitted to an intensive care unit, while 170 (78%) were only quarantined. Twenty-three percent of patients discontinued tyrosine kinase inhibitor (TKI) therapy during the infection. Twelve patients died due to COVID-19 with a mortality rate of 5·5% in the positive cohort and of 0·13% in the whole cohort. We could also document sequelae caused by the SARS-CoV-2 infection and an impact of the pandemic on the overall management of CML patients.

A limited amount of data has been published in chronic-phase chronic myeloid leukemia (CP-CML) patients aged75 years treated frontline with second-generation tyrosine kinase inhibitors.To address this issue in a clinical 'real-life' setting, we retrospectively analyzed 45 CP-CML patients (pts) followed in 20 Italian Centers and treated frontline with dasatinib (DAS).Median age was 78.4 years (range 75-89.2 years). DAS starting dose was 100 mg QD in 35 pts (77.7%), 80 mg QD in 1 pts (2.2%) and 50 mg QD in 9 pts (20.1%), respectively. The median follow-up was 42.6 months (IQR 20.4 - 63.3).Grade 3 and 4 side effects, both hematological and non-hematological, were detected in 6 (13.3%) and 12 (26.6%) pts, respectively. Pleural effusions of all grades occurred in 13 pts (28.8%) after a median period of DAS exposure of 14.7 months (IQR 3.0 - 33.1). The rates of DAS dose reduction and permanent drug discontinuation were 53.3% and 20.0%, respectively. As the best response, 42/45 patients (93.3%) achieved a complete cytogenetic response (CCyR), 35/45 (77.7%) a major molecular response (MMR) and 24/45 (53.3%) a deep molecular response (both MR 4.0 and MR 4.5). Only 1 patient (2.2%) progressed to the blast phase after 13 months of therapy; 8 deaths were observed (1 CML-related and 7 CML-unrelated). Cumulative event-free survival and overall survival at 36 months were 64.7% (95%, CI 49.4 - 80.0) and 82.3% (95%, CI 70.3-94.3), respectively.These findings, although evaluated in a limited and selected cohort of patients, suggest that DAS might be effective in older patients (aged75 years) affected by CP-CML with acceptable toxicity.

There is paucity of evidence-based data on health-related quality of life (HRQOL) outcomes of chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKIs). We performed a multicenter propensity-matched case-control study to compare HRQOL of newly diagnosed CML patients treated with front-line dasatinib (cases) or imatinib (controls). Patient-reported HRQOL was assessed with the EORTC QLQ-C30 and the EORTC QLQ-CML24 questionnaires. The impact on daily life scale of the EORTC QLQ-CML24 was selected a priori in the protocol as the primary HRQOL scale for the comparative analysis. Overall, 323 CML patients were enrolled of whom 223 in therapy with imatinib and 100 in therapy with dasatinib. Patients treated with dasatinib reported better disease-specific HRQOL outcomes in impact on daily life (Δ = 8.72, 95% confidence interval [CI]: 3.17-14.27, p = 0.002), satisfaction with social life (Δ = 13.45, 95% CI: 5.82-21.08, p = 0.001), and symptom burden (Δ = 7.69, 95% CI: 3.42-11.96, p = 0.001). Analysis by age groups showed that, in patients aged 60 years and over, differences favoring dasatinib were negligible across several cancer generic and disease-specific HRQOL domains. Our findings provide novel comparative HRQOL data that extends knowledge on safety and efficacy of these two TKIs and may help to facilitate first-line treatment decisions.

Background Recent investigations in chronic myeloid leukemia (CML) have focused on the identification and characterization of leukemic stem cells (LSCs). These cells reside within the CD34+ /CD38─ /Lin─ fraction and score positive for CD26 (dipeptidylpeptidase IV) a marker, expressed in both bone marrow (BM) and peripheral blood (PB) samples, that discriminates CML cells from normal hematopoietic stem cells (HSCs) or from LSCs of other myeloid neoplasms. CD26 evaluation could be a useful tool to improve the identification of CML LCSs by using flow-cytometry assay. Methods CD26+ LSCs have been isolated from EDTA PB and BM samples of patients with leucocytosis suspected for CML. Analysis of LSCs CML has been performed by using custom-made lyophilized pre-titrated antibody mixture test and control tube and a CD45+ /CD34+ /CD38- /CD26+ panel as a strict flow cytometric gating strategy. Results The expression of CD26 on CD34+ /CD38- population was detectable in 211/211 PB and 84/84 BM samples of subsequently confirmed BCR-ABL+ CP-CML patients. None of the 32 samples suspicious for CML but scoring negative for circulating CD26+ LSCs were diagnosed as CML after conventional cytogenetic and molecular testing. To validate our results, we checked for PB CD26+ LSCs in patients affected by other hematological disorders and they all scored negative for CD26 expression. Conclusions We propose flow cytometry evaluation of CD26 expression on PB CD34+ /CD38- population as a new rapid, reproducible, and powerful diagnostic tool for the diagnosis of CML. © 2019 The Authors. Cytometry Part B: Clinical Cytometry published by Wiley Periodicals, Inc. on behalf of International Clinical Cytometry Society.

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An observational prospective study was conducted by the CML Italian network to analyze the role of baseline patient characteristics and first line treatments on overall survival and CML-related mortality in 1206 newly diagnosed CML patients, 608 treated with imatinib (IMA) and 598 with 2nd generation tyrosine kinase inhibitors (2GTKI). IMA-treated patients were much older (median age 69 years, IQR 58-77) than the 2GTKI group (52, IQR 41-63) and had more comorbidities. Estimated 4-year overall survival of the entire cohort was 89% (95%CI 85.9-91.4). Overall, 73 patients (6.1%) died: 17 (2.8%) in the 2GTKI vs 56 (9.2%) in the IMA cohort (adjusted HR=0.50; 95% CI=0.26-0.94), but no differences were detected for CML-related mortality (10 (1.7%) vs 11 (1.8%) in the 2GTKIs vs IMA cohort (sHR=1.61; 0.52-4.96). The ELTS score was associated to CML mortality (high risk vs low, HR=9.67; 95%CI 2.94-31.74; p

In chronic-phase chronic myeloid leukemia (CML), tyrosine kinase inhibitors (TKIs) are the standard of care, and treatment-free remission (TFR) following the achievement of a stable deep molecular response (DMR) has become, alongside survival, a primary goal for virtually all patients. The GIMEMA CML working party recently suggested that the possibility of achieving TFR cannot be denied to any patient, and proposed specific treatment policies according to the patient’s age and risk. However, other international recommendations (including 2020 ELN recommendations) are more focused on survival and provide less detailed suggestions on how to choose first and subsequent lines of treatment. Consequently, some grey areas remain. After literature review, a panel of Italian experts discussed the following controversial issues: (1) early prediction of DMR and TFR: female sex, non-high disease risk score, e14a2 transcript and early MR achievement have been associated with stable DMR, but the lack of these criteria is not sufficient to exclude any patient from TFR; (2) criteria for first and subsequent line therapy choice: a number of patient and drug characteristics have been proposed to make a personalized decision; (3) monitoring of residual disease after discontinuation: after the first 6 months, the frequency of molecular tests can be reduced based on MR4.5 persistence and short turnaround time; (4) prognosis of TFR: therapy and DMR duration are important to predict TFR; although immunological control of CML plays a role, no immunological predictive phenotype is currently available. This guidance is intended as a practical tool to support physicians in decision making.

Tyrosine kinase inhibitors (TKIs) have radically changed the outcome of chronic myeloid leukemia (CML) patients in the last 20 years. Moreover, the advent of second generation TKIs, namely nilotinib and dasatinib, have largely increased the number of CML patients achieving deep and sustained molecular responses. However, the possible mechanisms capable of influencing the maintenance of the long-term molecular response are not yet fully known and understood. In this light, polymorphisms in MDR-ABC transporters may influence the efficacy and safety of TKIs. In this study, we examined seven single nucleotide polymorphisms (SNPs) in four ABC transporter genes: ABCC1 rs212090 (5463T>A), ABCC2 rs3740066 (3972C>T), ABCC2 rs4148386 G>A, ABCC2 rs1885301 (1549G>A), ABCG2 rs2231137 (34G>A), ABCG2 rs2231142 G>C, ABCB1 rs1045642 (3435C>T), to determine their effect on the achievement and/or loss of molecular response in 90 CML patients treated with nilotinib. We found that ABCC2 rs3740066 CC and CT as well as the ABCB1 rs1045642 TT genotypes correlated with a higher probability to achieve MR3 in a shorter time (p=0.02, p=0.004, and p=0.01), whereas ABCG2 rs2231137 GG was associated with lower probability of MR3 achievement (p=0.005). Moreover, ABCC2 rs3740066 CC genotype, the ABCB1 rs1045642 CC and TT genotypes were positively correlated with MR4 achievement (p=0.02, p=0.007, and p=0.003). We then generated a predictive model incorporating the information of four genotypes, to evaluate the combined effect of the SNPs. The combination of SNPs present in the model affected the probability and the time to molecular response. This model had a high prognostic significance for both MR3 and MR4 (p=0.005 and p=0.008, respectively). Finally, we found ABCG2 rs2231142 GG genotype to be associated with a decrease risk of MR3 loss. In conclusion, MDR-transporters SNPs may significantly affect the achievement and loss of molecular response in CML patients treated with nilotinib.

To evaluate the role of bosutinib in elderly patients aged >65 years with chronic myeloid leukemia (CML), a real-life cohort of 101 chronic-phase CML patients followed up in 23 Italian centers and treated with bosutinib in second or a subsequent line was retrospectively evaluated. Starting dose of bosutinib was 500 mg/day in 25 patients (24.8%), 400 mg/day in 7 patients (6.9%), 300 mg/day in 33 patients (32.7%), 200 mg/day in 34 patients (33.6%), and 100 mg/day in 2 patients (2.0%). Grade 3/4 hematological toxicity occurred in 7/101 patients (6.9%) and grade 3/4 extra-hematological toxicity in 19/101 patients (18.8%). Permanent bosutinib discontinuation due to toxicity was needed in 12 patients (11.9%). Among the 96 patients evaluable for response, 74 (77.0%) achieved a complete cytogenetic response (CCyR), while 64 of these 74 patients in CCyR (66.6% of all 96 evaluable patients) also achieved a molecular response (MR) (major MR [MR 3.0] in 21 [21.8%], deep MR [MR 4.0/4.5] in 43 [44.8%]). The 3-year event-free survival and overall survival of the whole patients' cohort from bosutinib start were 60.9% (CI 95% 49.3-72.5) and 86.4% (CI 95% 77.2-95.6), respectively. Our real-life data show that bosutinib is effective, with a favorable safety profile, also in elderly patients with important comorbidities and resistance and/or intolerance to previous tyrosine-kinase inhibitor treatments. As a consequence, it could play a significant role in current clinical practice for frail patients.

Recommendations for dyslipidemia management aimed at reducing arterial occlusive events (AOEs) have been recently published. So far, no data have been reported on the management of dyslipidemia in chronic myeloid leukemia (CML) patients treated with nilotinib. We investigated 369 CML adult patients, stratified according to the new Systematic Coronary Risk Evaluation (SCORE) scoring system. Plasma levels of cholesterol, HDL, LDL, and triglycerides were measured prior to the start of nilotinib and after 3, 6, and 12months. The 5-year cumulative incidence of AOEs was 15.9%. Patients with cholesterol levels > 200mg/dL and LDL > 70mg/dL 3months after treatment showed a significantly higher incidence of AOEs (21.9 ± 4.6% vs 6.2 ± 2.5, P= 0.003). Patients belonging to the high and very high SCORE risk group showed a significant increase of AOEs (34.4 ± 6% vs 10 ± 2.1%, P< 0.001). In multivariate analysis, both high cholesterol and LDL levels and a high and very high SCORE risk remained significantly associated with the risk of AOEs (P= 0.008; HR = 3.5; 95% CI = 1.4–8.7 and P < 0.001; HR = 4.4; 95% CI = 2–9.8, respectively). Overall, 78 patients (21.1%) presented dyslipidemia at the time of CML diagnosis and 88 (23.3%) after starting nilotinib, but only 26 of them (29.5%) were treated with statins. Low LDL and cholesterol plasma levels are associated with a significant lower risk of AOEs in CML patients treated with nilotinib in the real life.

Successful discontinuation of tyrosine kinase inhibitors has been achieved in patients with chronic-phase chronic myeloid leukemia (CML). Careful molecular monitoring after discontinuation warrants safe and prompt resumption of therapy. We retrospectively evaluated how molecular monitoring has been conducted in Italy in a cohort of patients who discontinued tyrosine kinase inhibitor (TKI) treatment per clinical practice. The outcome of these patients has recently been reported&mdash, 281 chronic-phase CML patients were included in this subanalysis. Median follow-up since discontinuation was 2 years. Overall, 2203 analyses were performed, 17.9% in the first three months and 38.4% in the first six months. Eighty-six patients lost major molecular response (MMR) in a mean time of 5.7 months&mdash, 65 pts (75.6%) during the first six months. We evaluated the number of patients who would experience a delay in diagnosis of MMR loss if a three-month monitoring schedule was adopted. In the first 6 months, 19 pts (29.2%) would have a one-month delay, 26 (40%) a 2-month delay. Very few patients would experience a delay in the following months. A less intense frequency of monitoring, particularly after the first 6 months off treatment, would not have affected the success of treatment-free remission (TFR) nor put patients at risk of progression.

The treatment of chronic myeloid leukemia (CML) has been radically changed by the approval of tyrosine kinase inhibitors (TKIs), which target BCR-ABL1 kinase activity. CML is now managed as a chronic disease requiring long-term treatment and close molecular monitoring. It has been shown that in a substantial number of patients who have achieved a stable deep molecular response (DMR), TKI treatment can be safely discontinued without loss of response. Therefore, treatment-free remission (TFR), through the achievement of a DMR, is increasingly regarded as a feasible treatment goal in many CML patients. However, only nilotinib has approval in this setting and a number of controversial aspects remain regarding treatment choices and timings, predictive factors, patient communication, and optimal strategies to achieve successful TFR. This narrative review aims to provide a comprehensive overview on how to optimize the path to DMR and TFR in patients with CML, and discusses recent data and future directions.

Hypertension is a commonly reported comorbidity in patients diagnosed with chronic myeloid leukemia (CML), and its management represents a challenge in patients treated with 2nd- or 3rd-generation tyrosine kinase inhibitors (TKIs), considering their additional cardiovascular (CV) toxicity. The renin angiotensin system (RAS) contributes to hypertension genesis and plays an important role in atherosclerosis development, proliferation, and differentiation of myeloid hematopoietic cells. We analyzed a cohort of 192 patients with hypertension at CML diagnosis, who were treated with 2nd- or 3rd-generation TKIs, and evaluated the efficacy of RAS inhibitors (angiotensin-converting enzyme inhibitors (ACEi) and angiotensin-II receptor blockers (ARBs)) in the prevention of arterial occlusive events (AOEs), as compared with other drug classes. The 5-year cumulative incidence of AOEs was 32.7 ± 4.2%. Patients with SCORE ≥ 5% (high-very-high) showed a significantly higher incidence of AOEs (33.7 ± 7.6% vs 13.6 ± 4.8%, p = 0.006). The AOE incidence was significantly lower in patients treated with RAS inhibitors (14.8 ± 4.2% vs 44 ± 1%, p < 0.001, HR = 0.283). The difference in the low and intermediate Sokal risk group was confirmed but not in the high-risk group, where a lower RAS expression has been reported. Our data suggest that RAS inhibitors may represent an optimal treatment in patients with hypertension and CML, treated with 2nd or 3rdG TKIs.

No abstract available.

Not available.

Background Role of erythropoietin (EPO) in the treatment of late anemia in patients with Chronic Myeloid Leukemia (CML) is still undefined. Methods Fifty CML patients treated at 14 institutions with frontline imatinib for at least 12 months and in stable complete cytogenetic response who developed a late chronic anemia treated with EPO were retrospectively evaluated. Results Median time from imatinib start to EPO treatment was 42.2 months [interquartile range (IQR) 20.8-91.9]. Median Hb value at EPO starting time was 9.9 g/dL (IQR 8.9-10.3): Eleven patients (22.0%) were transfusion dependent. Alpha-EPO (40 000 UI weekly) was employed in 37 patients, beta-EPO (30 000 UI weekly) in 9 patients, zeta-EPO (40 000 UI weekly) in 2 patients, and darbepoetin (150 mcg/weekly) in the remaining 2 patients. On the whole, 41 patients (82.0%) achieved an erythroid response, defined as a stable (>3 months) improvement >1.5 g/dL of Hb level, and 9 patients (18.0%) indeed resulted resistant. Among responding patients, 10 relapsed after a median time from EPO start of 20.7 months (IQR 10.8-63.7). No EPO-related toxicity was observed. Conclusions Results of EPO treatment for late chronic anemia during long-lasting imatinib therapy are encouraging, with a high rate of response.

TO THE EDITOR: The Imatinib Suspension and Validation (ISAV) study1 is a multicenter trial of imatinib discontinuation (ID) among patients with chronic myeloid leukemia (CML) in undetectable deep molecular remission (U-DMR). After 12 months of follow-up, 48% of patients relapsed (total n = 107), with the majority of relapses occurring within the first 9 months. An inverse relationship between patient age and risk of relapse was also observed at this timepoint. Here we report the final results of ISAV after a median follow-up of 49 months, as well as the dynamics of leukemic tumor load as determined by digital polymerase chain reaction (dPCR) in nonrelapsed patients. This trial is registered at www.clinicaltrials.gov (NCT01578213). Eligible patients were 18 years and older and had CML, either in chronic or accelerated phase, with U-DMR of at least 18 months’ duration and at least...

Introduction Tyrosine kinase inhibitors (TKIs) have dramatically changed the outcome of chronic phase chronic myeloid leukemia patients (CP-CML),improving the long-term outcome; indeed, life expectancy is now very close to that of age matched individuals in the general population. Imatinib (IMA) the first generation TKI, increased the overall survival(OS)by more than 80%. Second-generation TKIs, (2gen TKIs) used in first line dasatinib and nilotinib, induced faster molecular responses, rapidly reducing the disease burden, but did not change the OS of CP-CML newly diagnosed patients. Most of the available data reported were extrapolated from sponsored clinical trials. The aim of this analysis is to detail and analyze the prognostic features influencing the OS in a large Italian CML cohort of patients prospectively enrolled in the GIMEMA CML Italian study. Methods Relevant clinical, demographic, biological and treatment-related information were web-based collected during a multicenter,observational Italian study that enrolled consecutive patients in each disease phase, at 68 Italian hematologic centers belonging to the GIMEMA network from January 2013 to June 2020. We analyzed prognostic factors influencing the OS by Kaplan Meier method and Cox multivariable models. Results A cohort of 1206 patients was prospectively analyzed, 608 of them received frontline IMA and 598 2genTKIs. Median age in the IMA cohort was 69 years (range 58-77) vs 52 years in the 2genTKIs cohort (range 41-63). The male/female ratio was 1.7 in the IMA group and 1.35 in the 2genTKIs cohort. Ninety-eight percent of patients were in CP. Results of molecular analysis of the BCR-ABL transcript at baseline showed: b2a2 in 33.1 % of patients and b3a2 in 59.9%, while an atypical transcript was found in 7%. The cytogenetic analysis at baseline showed major and minor additional aberrations in 5.7% and 1.6% of patients respectively. In the IMA cohort,according to the Sokal score, 27.7%, 57.3% and 15% of patients were stratified as low, intermediate and high risk, whereas according to the ELTS score 51.3%, 35.5% and 13.3%, of patients were classified as low, intermediate and high risk. In the 2genTKIs cohort, according to the Sokal score, 44.8%, 34.5% and 20.8%, were low, intermediate and high risk, respectively, whereas according to the ELTS score, 66.9%, 22% and 11% were assigned to the respective risk groups.The Charlson comorbidity index in the IMA cohort was 2-3 and 4-5 in 74% and 26% of patients respectively; in the 2genTKIs cohort the score was 2-3 in 89% and 4-5 only in 10% of patients. Overall, median follow-up of the whole population was 24.7 months (range 13.3-39.3).Seventy-three patients (6.1%) in the overall population died, the majority of them in the IMA cohort: 56 patients (9.2%), at median age of 80.5 years,11/608 (1.8%) due to CML-related causes. Conversely,in the 2genTKIs cohort only 17 patients (2.8%) died, at a median age of 62 years, 10/598 (1.7%) for CML-related causes. Estimated 60-months OS of the overall population was 86.4% (95% CI 81.3-90.2): 75.8% (95% CI 64.5-84) in the IMA cohort and 93.8% (95% CI 87.5-97) in the 2genTKIs group (p Conclusions In this first analysis of our study different clinical behaviors were observed among Italian hematologists, who prevalently prescribed IMA to older patients,with more comorbidities, as compared to 2genTKIs.These differences explain a better OS for patients treated with 2genTKIs vs IMA, however, the risk of death for CML related causes is quite similar between the two groups, all the differences being attributable to other causes of death.Prognostic baseline features associated to an increased OS confirmed that, in addition to age, the ELTS score and the comorbidities are the main clinical factors that independently influence the long-term OS Disclosures Pregno: Incyte-Italy,: Membership on an entity's Board of Directors or advisory committees, Other: conference reports; Novartis-Italy: Membership on an entity's Board of Directors or advisory committees, Other: conference reports; Pfizer-Italy: Membership on an entity's Board of Directors or advisory committees, Other: conference reports. Breccia:Bristol-Myers Squibb/Celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Abbvie: Consultancy. Castagnetti:Novartis: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Galimberti:Novartis: Speakers Bureau; Incyte: Honoraria. Bocchia:CELGENE: Honoraria; Incyte: Honoraria. Abruzzese:Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bms: Honoraria; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees. Levato:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees; Gilead: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Rosti:Pfizer: Research Funding, Speakers Bureau; Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau; Incyte: Speakers Bureau. Di Raimondo:GILEAD, Incyte: Research Funding; Amgen, Takeda, Novartis: Honoraria; Celgene: Consultancy, Honoraria; Janssen: Consultancy, Honoraria; Amgen: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; GSK: Consultancy, Honoraria. Pane:Janssen: Other: Travel Expenses; Bristol Myers Squibb: 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, Speakers Bureau; Novartis pharma SAS: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Jazz Pharmaceuticals: Consultancy, Other: travel expenses, Speakers Bureau; Daiichi Sankyo: Consultancy, Other: Travel Expenses; Amgen: Consultancy, Other: Travel Expenses, Speakers Bureau; AbbVie: Consultancy, Other: Travel Expenses, Speakers Bureau. Foà:Incyte: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Saglio:Bristol-Myers Squibb: Research Funding; Pfizer: Research Funding; Incyte: Research Funding; Roche: Research Funding; Novartis: Research Funding; Ariad: Research Funding.

Summary Tyrosine kinase inhibitors (TKi) are effective against chronic myeloid leukemia (CML), but their inefficacy on leukemia stem cells (LSCs) may lead to relapse. To identify new druggable targets alternative to BCR/ABL, we investigated the role of the MEK5/ERK5 pathway in LSC maintenance in low oxygen, a feature of bone marrow stem cell niches. We found that MEK5/ERK5 pathway inhibition reduced the growth of CML patient-derived cells and cell lines in vitro and the number of leukemic cells in vivo. Treatment in vitro of primary CML cells with MEK5/ERK5 inhibitors, but not TKi, strikingly reduced culture repopulation ability (CRA), serial colony formation ability, long-term culture-initiating cells (LTC-ICs), and CD26-expressing cells. Importantly, MEK5/ERK5 inhibition was effective on CML cells regardless of the presence or absence of imatinib, and did not reduce CRA or LTC-ICs of normal CD34+ cells. Thus, targeting MEK/ERK5 may represent an innovative therapeutic approach to suppress CML progenitor/stem cells., Graphical Abstract, Highlights • ERK5 is constitutively active in chronic myeloid leukemia (CML) cells • ERK5 pathway inhibition reduces the growth of CML cells in vitro and in vivo • ERK5 pathway inhibition strikingly reduces CML progenitor/stem cell maintenance • The combination of ERK5i with imatinib reduces the expression of stem cell proteins, Tyrosine kinase inhibitors targeting BCR/ABL are very effective against chronic myeloid leukemia (CML) cells but not leukemia stem cells (LSCs). Dello Sbarba, Rovida, and colleagues discovered that targeting the extracellular signal-regulated kinase 5 pathway in CML cell lines and primary cells results in the suppression of LSC as well as, especially in combination with tyrosine kinase inhibitors, the overall cell population.

Myelodysplastic Syndromes (MDS) are clonal neoplasms where stem/progenitor cells endowed with self-renewal and capable of perpetuating the disease have been demonstrated. It is known that oxygen tension plays a key role in driving normal hematopoiesis and that hematopoietic stem cells are maintained in hypoxic areas of the bone marrow (BM). Hypoxia could also regulate leukemic/dysplastic hematopoiesis. We evaluated the stem cell potential of MDS cells derived from the BM of 39 MDS patients and selected under severe hypoxia. MDS cells rescued from hypoxia-incubated cultures were subjected to stem and progenitor cell assays in vitro, as well as to hematopoietic reconstitution assay in NOD-SCID mice. Incubation in severe hypoxia of cells explanted from MDS patients selected a cell subset endowed with stem cell potential, as determined in vitro. This occurred only from the BM of patients classified as IPSS low/INT-1 risk. Transplantation into NOD-SCID mice confirmed using an in vivo model that severe hypoxia selects a cell subset endowed with stem cell potential from bone marrow mononuclear cells (BMMC). derived from patients belonging to the IPSS low/int-1 risk group. Data here reported show that cells endowed with stem cell potential and capable of adapting to hypoxia and escaping hypoxia-induced apoptosis exist within MDS cell populations.

Background: Tyrosine kinase inhibitors (TKI) may offer a normal life expectancy to Chronic Myeloid Leukemia (CML) patients. However, during treatment with nilotinib, a higher than expected incidence of arterial occlusive events (AOEs) was observed. We retrospectively showed an "inflammatory status" during nilotinib treatment that may explain this increased incidence of AOEs. Here, we report results of a prospective multicenter (KIARO) study including 186 CML patients (89 imatinib, 59 nilotinib, 38 dasatinib) in which pro/anti-inflammatory cytokines were measured at diagnosis and during treatment, with the aim to investigate potential changes in each patient's inflammatory status possibly favoring AOEs. Aims: The aims of this study are: 1) to analyze prospectively inflammation status during TKI treatment; 2) to record AOEs; 3) to calculate the SCORE and evaluate its predictive role for AOEs; 4) to analyze possible associations of AOEs with altered inflammation status. Methods: Inflammatory status was evaluated by measuring IL6, IL10, TNFα, oxLDL and hs-CRP plasma levels at diagnosis and during treatment (+1, +3, +6, +12 months); additionally, clinical and biochemical pro-atherothrombotic profiles and the 10-year SCORE chart were also evaluated. Results: 186 newly-diagnosed CML patients starting either imatinib, nilotinib or dasatinib treatment, entered this study. Regarding the inflammation status, we observed that TNFα and IL6 levels were high at diagnosis and decreased during the first 12 months of treatment regardless the type of TKI; instead, IL10 levels were comparable among the 3 TKI cohorts at baseline, but showed a remarkably different evolution during treatment. In fact, IL10 levels were significantly higher after 6 and 12 months of imatinib (p=0.012 and p=0.009, respectively) and dasatinib (p=0.032 and p=0.014, respectively) compared to nilotinib. Consequently, TNFα/IL10 ratio was significantly higher in nilotinib cohort at 6 and 12 months respect to imatinib (p=0.044 at 6 months and p=0.041 at 12 months) and dasatinib (p=0.040 at 6 months and p=0.044 at 12 months). As well, IL6/IL10 ratio was significantly higher in nilotinib cohort compared to imatinib and dasatinib both at 6 (p=0.042 and p=0.049, respectively) and 12 months (p=0.040 and p=0.041, respectively) (Figure 1). OxLDL levels were similar in the 3 groups for the first 6 months. At 12 months we detected a significant increase of oxLDL levels in the nilotinib cohort (p=0.041), respect to imatinib and dasatinib. We did not find significant differences in hs-CRP levels across the 3 TKIs, although a trend for higher levels was observed in nilotinib cohort. Overall, these results suggest a TKI-driven pro-inflammatory status in nilotinib treated patients. After a median follow-up of 23.3 months of TKI treatment, 10 patients (5.4%) suffered an AOE, specifically: 6 ACS, 2 PAOD, 1 TIA and 1 stroke. 5 events (50%) occurred in patients treated with nilotinib, either in first line (4 patients) or in third line (1 patient, after failure following brief treatment with imatinib and dasatinib). In this subgroup of 10 patients experiencing an AOE, we observed a trend of increased IL6 and TNFα median values both at diagnosis and at each time point, compared with the remaining no-AOE patients. IL10 and oxLDL had similar median concentrations in both AOE and no-AOE cohorts, except for oxLDL at 12 months which resulted higher in patients who experienced AOEs. Moreover, regarding AOEs, nilotinib treatment showed a 3.1 times increased risk compared to other TKIs (HR 3.1, 95% CI 2.6-4.4 p< 0.001), whereas 10-year SCORE was not predictive in the whole cohort (HR 0.6, 95% CI 0.33-0.94 p= 0.094) or in any subgroup (imatinib HR 0.8, 95% CI 0.49-1.03 p= 0.067; nilotinib HR 0.4, 95% CI 0.29-0.76 p= 0.112, dasatinib HR 0.6, 95% CI 0.37-0.92 p= 0.082). Conclusions: Our results showed a pro-inflammatory/oxidative milieu increasing along treatment with nilotinib compared with imatinib or dasatinib, as demonstrated by higher IL6/IL10 and TNFα/IL10 ratios, higher levels of oxLDL and a trend for higher hs-CRP only in nilotinib cohort. However, due to the low number of observed events, a formal statistical analysis for any association between AOEs and pro/anti-inflammatory cytokines levels was not possible. Therefore, a longer follow-up is needed to further confirm the active role of nilotinib in AOEs pathogenesis. Figure 1 Figure 1. Disclosures Abruzzese: Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria. Galimberti: Incyte: Speakers Bureau; AbbVie, Janssen: Honoraria, Other: Travel grants. Stagno: Pfizer: Consultancy, Honoraria, Other: Support for attending meetings and/or travel; InCyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria, Other: Support for attending meetings and/or travel, Research Funding.

Background We already showed that in CML pts peripheral blood CD34+/CD38-/CD26+ cell population represent a "CML specific" leukemia stem cell (LSC) circulating compartment. Indeed, we demonstrated that CD26+LSCs are measurable by flow-cytometry in 100% of CML pts at diagnosis the latter representing an alternative and rapid diagnostic tool. In addition, in a cross-sectional study we were able to spot peripheral blood CD26+LSCs also in about 65% of CML during TKI treatment regardless of type and length of TKI treatment and degree of molecular response. However, no prospective data are available regarding the behavior of PB CD26+LSCs in terms of rate and timing of reduction during TKI therapy and the correlation, if any, with the attainment of response according to ELN guidelines. Interestingly, even CML patients in stable TFR may harbor circulating CD26+LSCs thus suggesting a probable active role of the immune system in the control of residual disease. One hypothesis could reside in the presence or absence on the LSCs of molecules (such as PD-L1) able to hamper an anti-leukemic T cell response. From Jan 2018 we conducted a prospective multicenter Italian study including CML pts at diagnosis treated and managed by each of 15 participating center according to ELN guidelines. We here present the first interim analysis after a median time of treatment of 12 mos. Aims The main goals of this study were to prospectively monitoring PB CD26+LScs in CML pts during TKI treatment and to correlate the behavior of LSCs with molecular response. In a proportion of pts PD-L1 expression on CD26+ LSCs at diagnosis was also evaluated. Methods At diagnosis and during TKI treatment, pts have been centrally evaluated in Siena lab for flow-cytometry PB CD26+ LSCs (+3, +6, +12, +18, +24 mos) and PD-L1 expression (at diagnosis). At each time point molecular BCR-ABL/ABLIS ratio was monitored locally in each center. Results 176 consecutive CML pts (IMA 92; NILO 61; DASA 23) were enrolled in the study so far (table 1). PB CD26+LSCs were measured at time 0 (baseline) in all 176 CML pts and in 165/176 (94%), 142/176 (81%) and 112/176 (71%) at +3, +6, +12 mos of TKI treatment, respectively. Median CD26+LSCs absolute number/µL at baseline was 6.96/µL (range 0.0126-64429), at +3 mos 0.0137/µL (range 0-6,49), at +6 mos 0.0056/µL (range 0-1.188), and at +12 mos 0.0112/µL (range 0-0.1824). No significant correlation between number of CD26+LSC, degree of response and BCR-ABL copies was found (Table 2). Interestingly, median CD26+LSCs at diagnosis was found significantly higher in NILO and DASA treated pts (12, 48/µL and 17,48/µL, respectively) than in IMA pts (4,58/µL). So far, 20/176 (11.4%) pts switched to different TKIs, due to failure/suboptimal response: of note, median CD26+ LSCs of this cohort at diagnosis was the highest (23.12/µL). Starting from Jun 2019, 44/176 (25%) CML pts have been evaluated also for PD-L1 expression at diagnosis: of these, 23/44 (52%) resulted PD-L1 positive and 21/44 (48%) resulted negative with a median of CD26+LSCs of 15.39/µL (range 1.28-635.5) and 4.45/µL (range 0.234-113.9), respectively. Conclusions After a sensible drop observed at 3 mos of any TKI treatment, CD26+LSCs are fluctuating and measurable at low level in most of pts (> 65%) even at 18 and 24 mos. We confirmed no correlation between the absolute number of persisting CD26+LSCs and BCR-ABL copies. However, pts with failure or suboptimal response showed the highest level of CD26+ at diagnosis. CD26+LSCs were found PD-L1+ in about half of 44 pts tested. At diagnosis higher CD26+LSCs number, PD-L1 positivity or both may correlate with a lower probability to achieve an optimal response; interim data of this first report will be presented; enrolment and follow up are ongoing. Disclosures Bocchia: Incyte: Honoraria; CELGENE: Honoraria. Abruzzese:Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bms: Honoraria. Galimberti:Novartis: Speakers Bureau; Incyte: Honoraria. Pregno:Incyte-Italy,: Membership on an entity's Board of Directors or advisory committees, Other: conference reports; Novartis-Italy: Membership on an entity's Board of Directors or advisory committees, Other: conference reports; Pfizer-Italy: Membership on an entity's Board of Directors or advisory committees, Other: conference reports. Crugnola:BMS: Honoraria; Janssen: Honoraria; Celgene: Honoraria; Novartis: Honoraria. Liberati:MORPHOSYS: Honoraria, Research Funding; ONCONOVA: Honoraria, Research Funding; INCYTE: Honoraria; VERASTEM: Honoraria, Research Funding; ROCHE: Honoraria, Research Funding; PFIZER: Honoraria, Research Funding; ONCOPEPTIDES AB: Honoraria, Research Funding; TAKEDA: Honoraria, Research Funding; FIBROGEN: Honoraria; BIOPHARMA: Honoraria; ARCHIGEN: Honoraria; BEIGENE: Honoraria; BMS: Honoraria; AMGEN: Honoraria; CELGENE: Honoraria; JANSSEN: Honoraria; ABBVIE: Honoraria, Research Funding; NOVARTIS: Honoraria, Research Funding; KARYOPHARM: Honoraria, Research Funding.

Background. The Philadelphia (Ph) chromosome (chr.) is the hallmark of chronic myeloid leukemia (CML) and typically results from the reciprocal translocation t(9;22)(q34;11.2). Complex variant translocations (CVT) involving one or more additional chr. are identified in less than 5% of newly diagnosed CML. There are conflicting reports about the prognostic impact of CVT in the achievement of optimal response to tyrosine kinase inhibitor (TKI), and very few studies addressed the role of frontline treatment with imatinib or second generation (2G)-TKI in patients with CVT. Aims. To assess the response to imatinib or 2G-TKI in a large cohort of newly diagnosed CML with CVT, and to explore the impact of the different chr. translocations on outcome. Methods. This observational retrospective study was conducted in 19 hematologic centers in the framework of Campus CML, a network of Italian physicians involved in the management of CML patients. All newly diagnosed CML from 2000 to 2019 were evaluated and patients with CVT were selected for the present analysis. Karyotypes were defined according to the 2016 International System for Human Cytogenetic Nomenclature. Responses to frontline treatment were retrospectively categorized according to the 2013 ELN recommendations, as they include cytogenetic milestones. Deep molecular response (DMR, i.e. MR4or better) was defined as BCR-ABLIS ratio ≤0.01% or undetectable disease with ≥10,000 ABL copies. Patients with DMR lasting ≥2 years and at least a Q-PCR test every 6 months were defined as stable DMR responders. Failure-free survival (FFS) was calculated from the start of frontline TKI treatment to progression to advanced phase, death, or switch to other treatments for resistance. For FFS calculation, patients were censored at TKI stop for treatment-free remission (TFR) or in case of switch for intolerance only. Differences between subgroups according to the partner chr. were presented for descriptive purposes. Results. CVT were identified in 109 (3.2%) patients from a whole population of 3,361 subjects with newly diagnosed CML. Ninety-five out of 109 patients (87%) exhibited three-way translocations, with chr. 1, 4, 6, 10, 11, 12, 14, 15 and 17 representing the most common additional partners (figure). Four- and five-way translocations were identified in 13 and 1 patients, respectively. Additional chr. abnormalities (ACA) in the Ph+ cells were observed in 15/109 (13.8%) patients and were more common in older individuals (p=0.018). Overall, median age at diagnosis was 50.6 years (range 20-90). Risk distribution according to the ELTS score was 54%, 28% and 8% for L, I and H risk, respectively (10% missing). Cytogenetic result was available before the choice of frontline treatment in 45% of cases and represented a decisive factor in 28% of them (i.e. clinicians selected a 2G-TKI or high-dose imatinib, according to the available options). Frontline TKI treatment was imatinib in 80 cases (73%) and 2G-TKI (nilotinib n=22, dasatinib n=6, bosutinib n=1) in the remaining cases. The frequency of optimal response at 3, 6 and 12 months was 48%, 45% and 53%, respectively, for imatinib-treated patients, and 76%, 83% and 76%, respectively, for the 2G-TKI cohort (p The subtype of CVT had an impact on response and long-term outcome. Patients with CVT involving chr. 1, 4, 6, 11 or 12 had a higher frequency of MMR at 12 months than patients with CVT involving chr. 10, 14, 15 or 17 (75.8% vs 30.4%, respectively, p=0.001), higher frequency of stable DMR (48.7% vs 22.2%, respectively; p=0.04) and tended to have better median FFS (p=0.07), regardless of the type of frontline TKI and of the ELTS score. Conclusions. Due to its retrospective nature, this study does not allow to define which is the optimal therapy for CML harboring CVT at diagnosis. However, our data reinforce the usefulness of bone marrow karyotyping in CML. The observed differences between partner chr. may also depend on the breaking points, which are variable. Further dissection of CVT will help to identify which are associated to a poor response to TKIs. Figure Disclosures D'Adda: Incyte: Other: Advisory board; Novartis: Other: Advisory board; Pfizer: Other: Advisory board. Galimberti:Novartis: Speakers Bureau; Incyte: Honoraria. Crugnola:Celgene: Honoraria; Janssen: Honoraria; BMS: Honoraria; Novartis: Honoraria. Bocchia:Incyte: Honoraria; CELGENE: 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. Breccia:Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Abbvie: Consultancy; Bristol-Myers Squibb/Celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Saglio:Novartis: Research Funding; Ariad: Research Funding; Pfizer: Research Funding; Bristol-Myers Squibb: Research Funding; Incyte: Research Funding; Roche: Research Funding.

Introduction. New guidelines for the management of dyslipidemia and lipid modification in order to reduce the risk of cardiovascular (CV) events have been recently published by the European Society of Cardiology (ESC) and the European Atherosclerosis Society (EAS). New recommendations regarding the target value of plasma lipids in very high and high CV risk patients have been provided, in addition to an estimate of the CV risk with a new Systematic Coronary Risk Evaluation (SCORE) chart. Few data have been reported on the management of dyslipidemia in chronic myeloid leukemia (CML) patients treated with nilotinib, and the association with arterial occlusive events (AOEs). We therefore analyzed a large real-life cohort of Italian patients with CML treated with nilotinib outside of clinical trials and evaluated the association between AOEs and plasma lipoproteins levels; moreover, we estimated the prognostic value of the new SCORE chart to predict AOEs. The secondary endpoint was to report the management of dyslipidemia in the clinical practice. Methods. We identified 233 adult patients with CML who were treated in 20 Italian centers with nilotinib. All patients were stratified into low to moderate (SCORE ≤ 5%) or high to very high (SCORE risk >5%) CV risk, according to the new version of the SCORE 2019. We recorded concentration levels of cholesterol, high-density lipoproteins (HDL), low-density lipoproteins (LDL) and triglycerides at diagnosis of CML, before starting ponatinib and therefore after 3, 6 and 12 months of treatment. All AOEs (cerebrovascular, peripheral vascular and CV events excluding hypertension) were considered. Results. The median age was 50 years (range 20-88) and the Sokal score was intermediate-high in 45.5% of patients. The median follow-up was 5 years (range 3.4-10.5). Nilotinib was administered as first line of therapy in (72%) of cases or second or subsequent lines of treatment for inefficacy (20.9%) or intolerance (7.1%). At baseline, nilotinib was administered at the following doses: 800 mg/day in 9.3% of patients, 600 mg/day in 87% of patients, 400 mg/day in 3.1% of patients and 300mg in 0.6% of patients, respectively. The median time of drug exposure was 60 months (range 2-155). The 48-month cumulative incidence rate of AOEs was 14.1±2.7%. Patients with cholesterol plasma levels > 200 mg/dL and LDL >70 mg/dL at baseline and 3 months after starting nilotinib, showed a significantly higher incidence of AOEs (24.5±7.3% vs 11±2.7%, P=0.02 and 22.3±4.9% vs 5.9±2.6, P=0.003, respectively) Figure 1. Patients with triglycerides levels > 200 mg/dL 3 months after starting nilotinib, showed a significantly higher incidence of AOEs (56±20.5% vs 13.3±2.7%, P=0.011) Patients belonging to the high and very high SCORE risk group showed a significant increase of AOEs (32.8.1±9% vs. 9±1%±2.6%, p=0.001). In multivariate analysis, statistical significance of cholesterol plasma levels > 200 mg/dL and LDL >70 mg/dL after 3 months and high-very-high SCORE was maintained (P=0.018, HR=3.4, 95% CI=1.2-9.4 and P=0.004, HR=3.5, 95% CI=1.5-8.2, respectively). Overall, 46 patients (20.5%) presented dyslipidemia at CML diagnosis and 65 (29%) at the start of treatment with nilotinib. Despite dyslipidemia, only 6 patients were taking statins during the treatment with nilotinib and only 5 started it after 3 months of nilotinib: 3 patients were treated with rosuvastatin and 2 with pravastatin. Conclusions. Our findings suggest that a proper control of dyslipidemia, keeping cholesterol and triglycerides plasma levels ≤ 200 mg/dL and LDL ≤70 mg/dL is associated with reduced risk of AOEs in CML patients treated with nilotinib. An under estimation of the clinical importance of elevated plasma lipids as a risk factor for AOEs events represents a possible issue in the real-life. Figure 1 Disclosures Abruzzese: Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bms: Honoraria; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees. Galimberti:Incyte: Honoraria; Novartis: Speakers Bureau. Castagnetti:Novartis: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Bristol Myers Squibb: Consultancy, Honoraria. Pregno:Incyte-Italy,: Membership on an entity's Board of Directors or advisory committees, Other: conference reports; Novartis-Italy: Membership on an entity's Board of Directors or advisory committees, Other: conference reports; Pfizer-Italy: Membership on an entity's Board of Directors or advisory committees, Other: conference reports. Bocchia:CELGENE: Honoraria; Incyte: Honoraria. Gugliotta:Novartis: Honoraria; Incyte: Honoraria; Pfizer: Honoraria. Foà:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees.

INTRODUCTION: Frontline therapy with second generation (2G) tyrosine-kinase inhibitors (TKIs) in chronic phase (CP) chronic myeloid leukemia (CML) patients demonstrated higher efficacy as compared to imatinib, with less patients experiencing treatment failure and progression to advanced disease. However, limited information are currently available on the management and outcome of those CML pts not achieving an optimal response to first-line treatment with a 2G-TKI. AIM: To describe the clinical outcome of CP CML patients without an optimal response to a frontline 2G-TKI that switched to alternative TKIs. METHODS: We performed a retrospective analysis in 22 Centers cooperating within the Italian CML Campus Project. Main inclusion criteria were: 1) diagnosis of CP-CML after 2010; 2) first-line treatment with a 2G-TKI; 3) switch to second-line treatment in case of non-optimal response (either following ELN recommendations or as for clinical practice); 4) CML in CP at the time of switching to second-line treatment. The main exclusion criteria were a switch to second-line treatment for intolerance or for low adherence to therapy. RESULTS: The main findings of this analysis are summarized in the table. Seventy-one pts meeting the inclusion/exclusion criteria were identified; the median age of pts at CML diagnosis was 46 (21-80) years. Sokal risk score was low, intermediate, and high in 24 (34%), 30 (42%), and 17 (24%) pts, respectively. First-line treatment was performed with nilotinib in 47 (66%) pts and dasatinib in 24 (34%) pts. According to the ELN 2020 recommendations, 51 (72%) pts fulfilled the criteria for "failure" and 20 (28%) pts those for "warning". BCR-ABL mutations were identified in 12 of 65 (18%) evaluable pts (T315I in 1 pt). Additional chromosomal abnormalities in Ph+ cells were identified in 6 of 54 (11%) evaluable pts. Second-line treatment was started after a median time of 16 (4-72) months, with ponatinib (40 pts, 56%), dasatinib (21 pts, 30%), nilotinib (7 pts, 10%), or bosutinib (3 pts, 4%). Median follow-up from start of second-line treatment was 25 (2-90) months. Best response to second-line treatment was MR2 in 18 (25%) pts and MR3 in 37 (51%) pts. Nineteen (27%) pts (13 for resistance and 6 for intolerance) switched to third-line treatment (ponatinib, 11 pts; nilotinib, 3 pts; dasatinib, 4 pts; imatinib, 1 pt), after a median time of 8 (1-72) months. Mutations were identified in 2 of 17 evaluable pts, and both patients harbored a T315I mutation. MR3 was reached by 9 (47%) of these pts. Lastly, 7 (10%) pts switched (6 for resistance and 1 for intolerance) to fourth-line treatment (asciminib, 4pts; dasatinib, 2 pts, nilotinib, 1 pt). Overall, 44 (62%) patients reached with sequential TKI treatments a MR3 (31/51 pts among "failures"; 13/20 among "warnings"). Allogeneic stem-cell transplantation (SCT) was performed in 7 (9.5%) pts (6 among "failures"), after a median time of 20 (15-60) months from CML diagnosis. Progression to advanced phase occurred in 2 (3%) pts; both pts previously met the ELN2020 "failure" criteria. Estimated 4-y PFS was 92.5%. Death occurred in 3 (4%) pts (1 after progression to blast phase, 2 for cardiovascular adverse events). Estimated 4-y OS was 93.7% CONCLUSION Our findings show that CP-CML patients not achieving an optimal response to frontline 2G-TKI therapy, despite a complex management, still have a favorable prognosis and survival due to the availability of both multiple TKI options and SCT. Figure Disclosures Gugliotta: Novartis: Honoraria; Incyte: Honoraria; Pfizer: Honoraria. Galimberti:Novartis: Speakers Bureau; Incyte: Honoraria. Abruzzese:Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Bms: Honoraria; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees. Bocchia:CELGENE: Honoraria; Incyte: Honoraria. Castagnetti:Bristol Myers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Incyte: Consultancy, Honoraria. Di Raimondo:Amgen, Takeda, Novartis: Honoraria; Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria; GILEAD, Incyte: Research Funding; GSK: Consultancy, Honoraria; Takeda: Consultancy, Honoraria; Amgen: Consultancy, Honoraria. Cavo:Jannsen, BMS, Celgene, Sanofi, GlaxoSmithKline, Takeda, Amgen, Oncopeptides, AbbVie, Karyopharm, Adaptive: Consultancy, Honoraria. Rosti:Bristol-Myers Squibb: Speakers Bureau; Incyte: Speakers Bureau; Novartis: Speakers Bureau; Pfizer: Research Funding, Speakers Bureau. Foà:Abbvie: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Roche: Membership on an entity's Board of Directors or advisory committees; Novartis: Speakers Bureau; Incyte: Speakers Bureau. Saglio:Pfizer: Research Funding; Ariad: Research Funding; Roche: Research Funding; Incyte: Research Funding; Bristol-Myers Squibb: Research Funding; Novartis: Research Funding. Breccia:Abbvie: Consultancy; Pfizer: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Bristol-Myers Squibb/Celgene: Consultancy, Honoraria; Novartis: Consultancy, Honoraria.

Context SETD2 is a tumor suppressor encoding a histone methyltransferase that trimethylates histone H3 at lysine 36 (H3K36Me3) and is involved in various cellular processes, including transcriptional regulation and repair of DNA damage. SETD2 loss of function due to mutations or deletions has been observed in some solid tumors and acute leukemias. Objective We aimed to investigate the frequency and underlying mechanisms of SETD2 loss of function in advanced phase of Chronic Myeloid Leukemia (CML). Patients A large cohort of 90 CML patients with advanced phase CML was screened for SETD2 and H3K36Me3 status. Results Reduced or null SETD2 and H3K36Me3 were detected by western blotting in 88% of advanced-phase CML patients, as compared to a pool of healthy donors and to CP patients at diagnosis. No genetic abnormalities or transcript downregulation were observed and enhanced SETD2 proteasome-mediated degradation was rather found to occur. After proteasome inhibition, accumulation of hyper-ubiquitinated SETD2 bound to MDM2 was observed. Both MDM2 pharmacological inhibition by SP-141 and siRNA-mediated silencing suggested that MDM2 is implicated in SETD2 loss. Aurora Kinase A, that is overexpressed in CML, was also found to co-immunoprecipitate with SETD2. Both pharmacological inhibition and knock-down of Aurora A rescued SETD2 and H3K36Me3. SETD2/H3K36Me3 loss was found to impair the proficiency of homologous recombination (HR) repair as demonstrated by comparison of phosphorylated histone 2A.X and Rad51 foci in steady-state conditions and after sub-lethal DNA damage by UV exposure in SETD2-deficient CML cells as well as in SETD2-proficient CML cells subjected to SETD2 silencing. Reduction of clonogenic growth after treatment with proteasome, MDM2, and Aurora kinase A inhibitors at nanomolar or subnanomolar concentrations was observed both in cell lines and in primary cells from SETD2-deficient advanced-phase CML patients. Conclusions In advanced-phase CML, phosphorylation by Aurora kinase A and hyper-ubiquitination by MDM2 are responsible for SETD2 non-genomic loss of function. Loss of SETD2/H3K36Me3 was associated with increased DNA damage and impaired HR repair. Restoring physiological H3K36Me3 levels should further be explored as a therapeutic strategy to help improve the outcome of this critical subset of patients.

Background Limited information is available regarding the rate of long-term cardiovascular (CV) mortality in chronic myeloid leukaemia (CML) patients treated with second- and third-generation tyrosine kinase inhibitors (2ndG/3rdG TKIs) in the real-life practice. Methods We identified 656 consecutive CML patients treated with nilotinib, dasatinib, bosutinib and ponatinib. Results The 15-year CV-mortality free survival was 93 ± 2.8%. Age ≥65 years (p = 0.005) and a positive history of CV disease (p = 0.04) were significantly associated with a lower CV-mortality free survival. CV disease accounted for 16.5% and 5% of potential years of life lost (PYLL) in male and female patients, respectively. The standard mortality ratio (SMR) following ischemic heart disease (IHD) was 3.9 in males and 3.8 in female patients, meaning an excess of IHD deaths observed, in comparison with the population of control. Conclusion. Prevention strategies based on CV risk factors, in particular in those patients with a previous history of CV disease, should be considered.

Background Risk of death is particularly high in patients with a previous history of arterial occlusive events (AOEs) and the probability for a recurrent event is around 20%. Little is known about recurrent AOE and the role of secondary prevention in patients with Chronic Myeloid Leukemia (CML) with previous AOE, treated with second- and third-generation tyrosine kinase inhibitors (2ndG/3rdG TKIs), nilotinib, dasatinib, bosutinib and ponatinib. Methods We identified a real-life cohort of 57 consecutive adult CML patients treated with 2ndG/3rdG TKI. All patients had a previous history of AOE. Ongoing use of secondary prevention of AOE (including antiplatelet agents, anticoagulant therapy, and statins) before starting a 2ndG/3rdG TKI was recorded, as well as CV risk factors. Results The 60-month cumulative incidence rate of recurrent AOEs was 47.8 ± 10.9%. Despite a history of AOE, 10 patients (16%) were not receiving secondary preventative measures. Patients treated with nilotinib and ponatinib showed a higher incidence of recurrent AOEs (76.7 ± 14.3% and 64 ± 20.1%, respectively) than those treated with dasatinib and bosutinib (44 ± 24.2% and 30.5 ± 15.5%, respectively) (p = 0.01). Only treatment with a 2ndG/3rdG TKI given as second or subsequent line therapy showed a significant association with an increased incidence of recurrent AOE (p = 0.039). Overall, 17 recurrent AOEs were observed; 3 CV-related deaths were reported. Conclusion CML patients with a previous history of AOE treated with 2ndG/3rdG TKI represent a particular patient population with a higher probability of experiencing a recurrent AOE; individualized treatment is needed to optimize secondary prevention.

Very elderly (> 75years) chronic myeloid leukaemia (CML) patients at diagnosis are sometimes treated with different doses of imatinib (IM) based on concomitant diseases and physicians’ judgement. However, data on long-term follow-up of these patients are still lacking. To investigate treatment response and outcome, we retrospectively revised an Italian database of 263 very elderly CML patients receiving IM from the time of diagnosis. Median age at diagnosis was 78.5years and 56% of patients had 2 or 3 comorbidities. A complete haematological and cytogenetic response were achieved in 244 (92.8%) and 184 (69.9%) patients, respectively. In 148 cases (56.2%), a major molecular response was observed, which was deep in 63 cases (24%). A blastic phase occurred in 11 patients (4.2%). After a median follow-up of 45.0months, 93 patients have died (9 from disease progression) and 104 (39.5%) are still in treatment with IM. Incidence of grades 3–4 haematological and non-haematological toxicity was similar to those reported in younger patients. Five-year event-free survival was 54.5% and 45.2% in patients ≤80years and > 80years, respectively (p = 0.098). Five years OS was 75.7% and 61.6% in patients ≤80years and > 80years, respectively (p = 0.003). These findings show that IM plays an important role in frontline treatment of very elderly CML patients without increased toxicity and any effort to treat these patients with standard doses should be made in order to achieve responses as in younger subjects.

BCR-ABL1 kinase domain (KD) mutation status is considered to be an important element of clinical decision algorithms for chronic myeloid leukemia (CML) patients who do not achieve an optimal response to tyrosine kinase inhibitors (TKIs). Conventional Sanger sequencing is the method currently recommended to test BCR-ABL1 KD mutations. However, Sanger sequencing has limited sensitivity and cannot always discriminate between polyclonal and compound mutations. The use of next-generation sequencing (NGS) is increasingly widespread in diagnostic laboratories and represents an attractive alternative. Currently available data on the clinical impact of NGS-based mutational testing in CML patients do not allow recommendations with a high grade of evidence to be prepared. This article reports the results of a group discussion among an ad hoc expert panel with the objective of producing recommendations on the appropriateness of clinical decisions about the indication for NGS, the performance characteristics of NGS platforms, and the therapeutic changes that could be applied based on the use of NGS in CML. Overall, these recommendations might be employed to inform clinicians about the practical use of NGS in CML.

Several papers authored by international experts have proposed recommendations on the management of BCR-ABL1+ chronic myeloid leukemia (CML). Following these recommendations, survival of CML patients has become very close to normal. The next, ambitious, step is to bring as many patients as possible into a condition of treatment-free remission (TFR). The Gruppo Italiano Malattie EMatologiche dell’Adulto (GIMEMA; Italian Group for Hematologic Diseases of the Adult) CML Working Party (WP) has developed a project aimed at selecting the treatment policies that may increase the probability of TFR, taking into account 4 variables: the need for TFR, the tyrosine kinase inhibitors (TKIs), the characteristics of leukemia, and the patient. A Delphi-like method was used to reach a consensus among the representatives of 50 centers of the CML WP. A consensus was reached on the assessment of disease risk (EUTOS Long Term Survival [ELTS] score), on the definition of the most appropriate age boundaries for the choice of first-line treatment, on the choice of the TKI for first-line treatment, and on the definition of the responses that do not require a change of the TKI (BCR-ABL1 ≤10% at 3 months, ≤1% at 6 months, ≤0.1% at 12 months, ≤0.01% at 24 months), and of the responses that require a change of the TKI, when the goal is TFR (BCR-ABL1 >10% at 3 and 6 months, >1% at 12 months, and >0.1% at 24 months). These suggestions may help optimize the treatment strategy for TFR.

Arterial occlusive events (AOEs) represent emerging complications in chronic myeloid leukemia (CML) patients treated with ponatinib. We identified 85 consecutive CML adult patients who were treated with ponatinib in 17 Italian centers. Patients were stratified according to the Systematic Coronary Risk Evaluation (SCORE) assessment, based on sex, age, smoking habits, systolic blood pressure, and total cholesterol levels. The 60-month cumulative incidence rate of AOEs excluding hypertension was 25.7%. Hypertension was reported in 14.1% of patients. The median time of exposure to ponatinib was 28months (range, 3-69months). Patients with a high to very high SCORE risk showed a significantly higher incidence rate of AOEs (74.3% vs 15.2%, P&nbsp

It is judged safe to discontinue treatment with tyrosine kinase inhibitors (TKI) for chronic myeloid leukemia (CML) in experimental trials on treatment-free remission (TFR). We collected a total of 293 Italian patients with chronic phase CML who discontinued TKI in deep molecular response. Seventy-two percent of patients were on treatment with imatinib, and 28% with second generation TKI at the time of discontinuation. Median duration of treatment with the last TKI was 77 months [Interquartile Range (IQR) 54;111], median duration of deep molecular response was 46 months (IQR 31;74). Duration of treatment with TKI and duration of deep molecular response were shorter with second generation TKI than with imatinib (P

Background: Since its introduction ponatinib has proved great efficacy among patients (pts) with chronic myeloid leukemia (CML), representing in some settings like the T315I mutation the only therapeutical choice due to its unique conformation. Its use both in the cohort of heavily pretreated CML and frontline has led to promising results in terms of overall survival (OS) and progression free survival (PFS), as demonstrated in the PACE study (Cortes JE, Blood 2018) and in the single center experience of the MD Anderson (Jain P, Lancet Haematol 2015). The cardiovascular toxicity associated with treatment has been addressed both in protocols and real-life experiences: it is clear that the benefits of ponatinib in terms of molecular response have to be balanced with the possibility of adverse events such as arterial and venous thromboembolism, dyslipidemia and hypertension which have to be managed and, whenever possible, prevented (Dorer JD, Leuk Res 2016; Caocci G, Int J Cardiol 2019). Before the final registration of the drug by AIFA, ponatinib has been available in Italy since October 2011 to March 2015 in compassionate regimen: the results collected here represent a real-life experience on ponatinib use in a cohort of Italian patients mostly heavily pre-treated. Methods: Italian chronic-phase (CP) CML pts treated with ponatinib in compassionate regimen since October 2011 were collected in the GIMEMA retrospective multicenter protocol CML1214 (clinicaltrials.gov NCT02448095). Primary objective of the study was the assessment of the tolerability and safety profile; secondary objectives were the assessment of the OS, PFS, best response, mutational status, rate of dose reductions. Data were collected following the rules of retrospective studies in Italy and all patients signed an informed consent. Results: 34 pts with CP-CML were enrolled. Accelerated phase or blastic phase were considered as exclusion criteria. There were 17 males and 17 females, with a median age of 62 (25-84) years at ponatinib initiation. Sokal score was high in 7 (23.33%), intermediate in 17 (56.67%), low in 6 (20%) and unknown in 4 pts. Regarding previous TKIs, 22 (64.7%) pts had three previous lines of therapy, 10 (29.41%) two lines, 2 (5.8%) only one TKI before ponatinib. Two patients experienced a previous stem cell transplant (SCT) and other 10 (29.4%) harbored a T315I mutation before ponatinib initiation. At baseline none of the 34 patients were in major molecular remission (MMR). The median follow-up on ponatinib was 46.6 months (range 15.2-74.5). Cumulative incidence of MMR was 14.7% at three months, 20.6% at six months, 29.4% at nine months, and 55.5% at 36 months. Rate of OS at 36 months was 80% (Figure 1); the presence of T315I did not affect survival. At last follow-up 17 pts were still on treatment with ponatinib; eight pts died, 3 after SCT, 1 for cardiovascular toxicity, 3 for disease progression; one for unknown reason. The treatment-related vascular adverse events (AEs) represented 20.6% of total AEs reported: 6 of them were cardiovascular, 2 cerebrovascular, 2 peripheral, 3 new-onset hypertension, 2 cardiac failures. Non cardiovascular AEs were mostly due to hematological intolerance, with 43 events of neutropenia/thrombocytopenia out of 73 total collateral effects, followed by 9 reported skin problems (which varied from simple rash or desquamation to one episode of ichthyosis). Conclusions: After a median follow up of 46.6 months, ponatinib provided substantial benefits in a cohort of pts in a timeframe where, after failing 2nd generation TKIs, no other chances were available except transplantation, and T315I positive patients were practically orphan of treatment before ponatinib. Aside from the large prospective PACE trial, results from GIMEMA CML1214 pair with other real-life experiences like the French PEARL (Heiblig M, Exp Hematol 2018) or the Spanish GELMC (Garcia-Gutierrez V, EHA 2016) reports, thus confirming the manageability and the effectiveness of this therapy in challenging clinical situations. Disclosures Fava: Incyte: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Novartis: Honoraria. Pregno:Incyte: Consultancy, Honoraria; Bristol Myers Squibb: Honoraria; Pfizer: Honoraria; Novartis: Honoraria. Abruzzese:BMS: Consultancy; Incyte: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Gambacorti-Passerini:Pfizer: Honoraria, Research Funding; Bristol-Meyers Squibb: Consultancy. Elena:Pfizer: Consultancy; Novartis: Consultancy. Iurlo:Pfizer: Other: Speaker Honoraria; Novartis: Other: Speaker Honoraria; Incyte: Other: Speaker Honoraria. Saglio:Celgene: Consultancy; Jansen: Consultancy; Pfizer: Consultancy; Incyte: Consultancy; BMS: Consultancy; Novartis: Consultancy; Ariad: Consultancy.

The introduction of second-generation tyrosine-kinase inhibitors (TKIs) has generated a lively debate on the choice of first-line TKI in chronic phase, chronic myeloid leukemia (CML). Despite the TKIs have different efficacy and toxicity profiles, the planned use of two TKIs has never been investigated. We report on a phase 2 study that was designed to evaluate efficacy and safety of a treatment alternating nilotinib and imatinib, in newly diagnosed BCR-ABL1 positive, chronic phase, CML patients. One hundred twenty-three patients were enrolled. Median age was 56 years. The probabilities of achieving a complete cytogenetic response, a major molecular response, and a deep molecular response (MR 4.0) by 2 years were 93%, 87%, and 61%, respectively. The 5-year overall survival and progression-free survival were 89%. Response rates and survival are in the range of those reported with nilotinib alone. Moreover, we observed a relatively low rate of cardiovascular adverse events (5%). These data show that the different efficacy and toxicity profiles of TKIs could be favorably exploited by alternating their use. Am. J. Hematol. 91:617-622, 2016. © 2016 Wiley Periodicals, Inc.

Scarce information is available on the use of ponatinib as second-line treatment in chronic phase chronic myeloid leukemia (CP-CML) patients resistant and/or intolerant to prior tyrosine kinase inhibitor (TKI) therapy. We collected data from 29 CML patients, with a median age of 54 years (range 32–72). Eleven patients had received dasatinib, 15 patients received nilotinib, and 3 patients received imatinib as first-line treatment. Forty-five percent of patients started ponatinib for secondary resistance, 38% for primary resistance, 7% for severe intolerance associated to a molecular warning, 7% due to the presence of a T315I mutation, and 3% for severe intolerance. Ponatinib was started at a dose of 45 mg in 60% of patients, 30 mg in 38%, and 15 mg in 2% of patients. Overall, at a median follow-up of 12 months, 85% of treated patients improved the level of response as compared to baseline, with 10 patients achieving a deep molecular response (MR4-4.5). No thrombotic events were recorded. The dose was reduced during treatment in 2 patients due to intolerance and in 8 patients in order to reduce the cardiovascular risk. Ponatinib seems a valid second-line treatment option for chronic phase CML, in particular for patients who failed a front-line second-generation TKI due to BCR-ABL-independent mechanisms of resistance.

In spite of the proven efficacy of the tyrosine kinase inhibitor (TKI), imatinib, in chronic myeloid leukemia (CML), many patients develop intolerance and discontinue therapy in the long-term. Second-generation TKIs (dasatinib, nilotinib, bosutinib) and the third-generation TKI, ponatinib, have added opportunities but also complexity in the settings of CML treatment.Different definitions of intolerance have been used through several clinical trials, making the published data non homogenous. In most cases, only the severity of acute adverse events (AEs), graded by conventional scales such as Common Terminology Criteria for Adverse Events, was reported. Limited attention to long-term events or more in general, to the impact of AEs on patient quality of life (QoL), remains a problem. Ponatinib is active against all BCR-ABL1 mutants, including T315I, and is widely used to treat patients who developed resistance to other TKIs in any CML phase; however, only limited data is available on the possible role of ponatinib for intolerant patients.We review the different definitions of intolerance used in sponsored trials and in clinical practice, and we discuss how such definitions impact on the management of AEs. We summarize how to evaluate QoL during treatment with TKIs and how to include ponatinib among possible option for intolerant patients.

Hepatic Veno-occlusive disease (VOD) is a potentially severe complication of hematopoietic stem cell transplantation (HSCT). Here we report two patients receiving an allogeneic HSCT who developed late onset VOD with atypical clinical features. The two patients presented with only few risk factors, namely, advanced acute leukemia, a myeloablative busulphan-containing regimen and received grafts from an unrelated donor. The first patient did not experience painful hepatomegaly and weight gain and both patients showed only a mild elevation in total serum bilirubin level. Most importantly, the two patients developed clinical signs beyond day 21 post-HSCT. Hepatic transjugular biopsy confirmed the diagnosis of VOD. Intravenous defibrotide was promptly started leading to a marked clinical improvement. Based on our experience, liver biopsy may represent a useful diagnostic tool when the clinical features of VOD are ambiguous. Early therapeutic intervention with defibrotide represents a crucial issue for the successful outcome of patients with VOD.

Background: Ponatinib is effective as salvage treatment for chronic phase (CP) Ph+ chronic myeloid leukemia (CML) patients resistant or intolerant to prior TKIs. Based on the concern for an unfavourable cardiovascular toxicity profile, a dose reduction to 15 mg daily is currently recommended in CP patients after the achievement of treatment milestones. As more flexible approaches with TKIs dosage are increasingly adopted in clinical practice, identifying specific profiles of patients eligible for different treatment strategies, in order to improve the benefit/risk ratio, would be of particular interest. Aims: To update previous observations in an extended cohort of CML patients, resistant or intolerant to prior TKIs, describing the efficacy and toxicity of two different ponatinib schedules (de-escalated vs 15 mg starting dose). Secondly, to investigate whether specific subsets of CML patients were managed more successfully with one strategy. Methods: A retrospective analysis of CML-CP patients treated with ponatinib 15 mg, as starting or de-escalated dose has been performed. No pre-specified criteria to switch to ponatinib, to reduce or to start therapy with a lower dose were indicated. Cytogenetic and molecular responses were evaluated according to the ELN2013 recommendations. Toxicities under ponatinib treatment leading to transient or definitive discontinuation were recorded. Results: 68 patients were included in this analysis. Median age at ponatinib start was 57 years (range: 28-87). The median time from CML diagnosis to ponatinib treatment was 4.6 years (range: 0.4-19). Most patients (70.6%) were treated with imatinib as frontline treatment. 30/68 patients (44%) received ponatinib as 4th or subsequent line of therapy. ABL1 mutations were detected in 18 (26.5%) patients (being 44% of them positive for the T315I mutation). 50/68 (73.5%) of cases had less than MR2 at the time of ponatinib initiation, with one third exhibiting primary refractoriness to all prior treatments. Resistance to prior TKIs was the reason for switch in 85% of patients treated with higher doses of ponatinib, while 13/26 patients starting with 15 mg were purely intolerant or intolerant and resistant (p= 0.001). No other significant differences between the two groups were identified. MR2, MR3 and MR4/MR4.5 rates were 78.6%, 59.6% and 28.6% in 42 patients treated with the "de-escalated" approach, respectively. First step of dose reduction was decided after a median time of 3.1 months, with a subsequent decrease to 15 mg after a median of 10 months. Dose modifications were guided mostly by adverse events (73%) and, less frequently, to prevent toxicity and/or following response attainment (27%). Median duration of treatment was 27 months (range: 2-81), with 5/42 patients discontinuing ponatinib (1 cerebrovascular accident, 2 severe hematologic toxicities, two cases of resistance/progression). 4 deaths were registered, three after blast crisis and one for a fatal cardiovascular event. 26 patients started ponatinib 15 mg daily, with a median duration of treatment was 15 months (range: 2-58). MR2 was obtained in 77%, MR3 in 69.3% and MR4 in 46.2% of cases, respectively. MR3 or deeper responses were maintained in 80% of patients; 7/26 lost their best acquired response, with subsequent dose escalation to higher than 15 mg in 5/26 patients. Treatment discontinuation was necessary in 3 cases (1 coronary vasospasm-induced acute coronary syndrome, 2 muscle skeletal pain). Of note, patients with ABL mutations gained benefit only from the "de-escalated" approach, with response improvements in 10/14 of cases vs 0/4 in the "low dose" group. Similarly, a higher rate of at least a MR2 was obtained in primary refractory patients treated ab initio with higher doses of ponatinib (57.1 % vs 14.3 %). However, focusing only on pure intolerant patients, 15 mg starting dose was very effective, with all patients achieving at least a MR3 or deeper response. Summary/Conclusion: With the limits of the retrospective nature and small sample size, these data suggest that different dose strategies could be applied to specific subsets of CP-CML patients. While mutations or refractoriness to previous treatments should address towards a "debulking approach" with 45 or 30 mg ponatinib dose, intolerant or "low level resistance" cases could benefit from lower starting dose. Further investigation in larger prospective trials is warranted. Disclosures Castagnetti: Incyte: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Bristol Meyers Squibb: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Gugliotta:Bristol-Myers Squibb: Honoraria; Incyte: Honoraria; Novartis: Honoraria; Pfizer: Honoraria. Abruzzese:Ariad: Consultancy; BMS: Consultancy; Novartis: Consultancy; Pfizer: Consultancy. Breccia:Pfizer: Honoraria; BMS: Honoraria; Novartis: Honoraria; Incyte: Honoraria. Levato:Novartis: Other: Advisory board. Pane:AMGEN: Speakers Bureau; BMS: Speakers Bureau; Novartis: Research Funding, Speakers Bureau.

Introduction: Bosutinib is a Src/Abl tyrosine kinase inhibitor (TKI) currently licensed for patients with Ph+ chronic-phase (CP), accelerated-phase (AP), or blast-phase (BP) Chronic Myeloid Leukemia after failure or intolerance to at least 2 other TKIs. It can also be prescribed, in accordance with label if, after failure of the first TKI therapy, another option does not seem feasible. Previous studies demonstrated a potent activity of second-line bosutinib across a spectrum of BCR-ABL1 mutations and a distinct toxicity profile compared to other TKIs. Aim: We retrospectively assessed the efficacy and safety of real life Bosutinib administration in 85 patients resistant/refractory or intolerant to other TKIs, referred to 22 Italian Hematological Institutions. The main features at Bosutinib start are reported in the Table. Results: At Bosutinib start, all patients were in CP. 60 patients (71%) were resistant/refractory, 25 (29%) were intolerant to previous TKIs. BCR-ABL1 kinase mutations were reported in 5/35 evaluable patients (14%); no T315I was reported. The number of previous TKIs was less than 3 in 24/85 patients (28%) and 3 or more in 61 (72%). Comorbidities were present in 63 patients (74%), the most common being arterial hypertension (40), diabetes (14), cardiac disease (10) and chronic obstructive pulmonary disease (6). The most frequent concomitant medications were: antihypertensive in 55% patients, antiplatelets in 26%, antidiabetic in 19%. The initial dose was 100 mg in 4/85 patients (5%), 200 mg in 24 (28%), 300 mg in 18 (22%), 400 in 8 (9%); 31 patients (36%) started at the full standard dose of 500 mg. Major Molecular Response (MMR)/Deep Molecular Response (DMR) were achieved by 37/80 (46%) evaluable patients; 43/80 patients (54%) never reached a MMR/DMR at any time. Best responses in these cases were: Complete Hematologic Response (CHR) in 4 patients (9%), Partial Cytogenetic Response (PCyR) in 6 (14%), Complete Cytogenetic Response (CCyR) in 10 (23%). Dose reductions were necessary in 4 patients (5%) due to adverse events (2 cases of diarrhea, 1 transaminase elevation, 1 skin rash). After a median follow-up of 26 months (range 3-49), 75/85 patients (88%) are alive and 54/75 patients (72%) are still in treatment. Discontinuations were due to: intolerance in 8/75 patients (11%), loss of response in 3/75 (4%), resistance to therapy in 10/75 (13%). Hematological toxicity was observed in 14 patients (16%), any grade, and grade 3-4 in 3 (3%). Extra-hematological toxicity was reported in 41/85 patients (48%), any grade, and grade 3-4 in 14 patients (16%). Causes of death were: acute myocardial infarction (3), cardiac failure (2), acute respiratory distress (2), allogeneic transplant complications (1), cerebral hemorrhage (2). Conclusions: In our "real life experience" with Bosutinib, we confirm a stable long-term efficacy in heavily pre-treated, mainly elderly patients with intolerance/resistance to other TKIs, who show an initial response to treatment, as reported in clinical trials. Patients show a fast response to the drug (mainly at three months). Hematological and extrahematological toxicities are manageable. Disclosures Breccia: BMS: Honoraria; Incyte: Honoraria; Pfizer: Honoraria; Novartis: Honoraria. Abruzzese:Novartis: Consultancy; Ariad: Consultancy; BMS: Consultancy; Pfizer: Consultancy. Castagnetti:Bristol Meyers Squibb: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria; Incyte: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Bonifacio:Novartis: Research Funding; Amgen: Consultancy; Pfizer: Consultancy; Incyte: Consultancy; Bristol Myers Squibb: Consultancy.

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Chronic myeloid leukemia (CML) patients in sustained “deep molecular response” may stop TKI treatment without disease recurrence; however, half of them lose molecular response shortly after TKI withdrawing. Well-defined eligibility criteria to predict a safe discontinuation up-front are still missing. Relapse is probably due to residual quiescent TKI-resistant leukemic stem cells (LSCs) supposedly transcriptionally low/silent and not easily detectable by BCR-ABL1 qRT-PCR. Bone marrow Ph+ CML CD34+/CD38− LSCs were found to specifically co-express CD26 (dipeptidylpeptidase-IV). We explored feasibility of detecting and quantifying CD26+ LSCs by flow cytometry in peripheral blood (PB). Over 400 CML patients (at diagnosis and during/after therapy) entered this cross-sectional study in which CD26 expression was evaluated by a standardized multiparametric flow cytometry analysis on PB CD45+/CD34+/CD38− stem cell population. All 120 CP-CML patients at diagnosis showed measurable PB CD26+ LSCs (median 19.20/μL, range 0.27–698.6). PB CD26+ LSCs were also detectable in 169/236 (71.6%) CP-CML patients in first-line TKI treatment (median 0.014 cells/μL; range 0.0012–0.66) and in 74/112 (66%), additional patients studied on treatment-free remission (TFR) (median 0.015/μL; range 0.006–0.76). Notably, no correlation between BCR-ABL/ABLIS ratio and number of residual LSCs was found both in patients on or off TKIs. This is the first evidence that “circulating” CML LSCs persist in the majority of CML patients in molecular response while on TKI treatment and even after TKI discontinuation. Prospective studies evaluating the dynamics of PB CD26+ LSCs during TKI treatment and the role of a “stem cell response” threshold to achieve and maintain TFR are ongoing.