We evaluate outcomes of ponatinib treatment in Argentinean real-world setting. Seventy-two patients were included. Molecular response (MR) < 1% IS%BCR::ABL1 at 12 months was achieved in 51.6% of evaluable patients. Estimated 2-year progression free survival was 84%. Older age, hypercholesterolemia and a SCORErisk > 2% were significantly associated with higher risk of arterial occlusive events. Control of CV risk factors and reducing doses at optimal time-points may help to optimize ponatinib use in daily practice. Background: Ponatinib is a third-generation tyrosine-kinase inhibitor (TKI), indicated in patients with chronic phase (CP), accelerated phase (AP), or blast phase (BP) chronic myeloid leukemia (CML), who are resistant or intolerant to >= 2 prior TKIs, patients for whom subsequent treatment with imatinib is not appropriate, and patients who have a T315I mutation. Patients and Methods: We aimed to evaluate outcomes of ponatinib treatment, including safety, with focus on cardiovascular toxicity, in real-world patients from Argentina. Data from patients with CP CML treated with ponatinib was retrospectively retrieved from 2013 to 2023 in 7 centers. Results: Seventy-two patients were included (median age: 44 years; male: 55.5%; T315I mutation: 32%: median treatment duration: 36 months. At baseline, 57 patients (79%) had a breakpoint cluster region-Abelson (BCR::ABL1) transcript level > 10% on the international reporting scale (BCR::ABL1 IS). A molecular response (MR, BCR::ABL1 (IS) < 1%) was achieved at 12 months in 51.6% of evaluable patients; 57% maintained MR at last follow-up. Overall, 43% and 25% maintained major MR (MMR) or deep MR (DMR) (MR4.0-MR5.0), respectively at last follow-up. Twelve (16.6%) ponatinib-resistant patients were rescued with allogeneic hematopoietic stem cell transplantation. The estimated 2-year progression-free survival (PFS) was 84%. Ponatinib dose was reduced during treatment in 22 patients; nevertheless, MMR was maintained in 50% of these patients. Severe arterial occlusive events (AOE) were reported in 10.9% of patients after a median treatment of 5 months. Conclusion: CV toxicity was consistent with clinical trials and other real-world registries. Older age, hypercholesterolemia and a SCORE risk > 2% were significantly associated with higher risk of AOEs. Controlling CV risk factors and reducing doses at optimal time points may help to optimize ponatinib use in daily practice.

Introduction: Tyrosine Kinase inhibitors (TKIs) treatment in chronic myeloid leukemia (CML) patients have achieved a life expectancy similar to the general population. In clinical practice, TKIs dose reduction (DR) frequently occurs due to numerous adverse events with profound impact on quality of life. However, there is not enough scientific and literary evidence supporting this strategy. We report our real-world experience in Latin America with low dose TKIs and the molecular recurrence-free survival (MRFS) in this population. Material and Methods: Retrospective, multicentric, observational study of a real world cohort of CML chronic phase patients treated with reduced TKI dose between 2000 and 2024. Data was collected from 9 institutions in Latin America. Patients ≥ 18 years who received lower doses of TKI were included, regardless of molecular response (MR) and status at the time of tapering. A DR was defined as Imatinib < 400 mg/day, Dasatinib < 100 mg/day, Nilotinib < 600 mg/day, Bosutinib < 500 mg/day and Ponatinib < 45 mg/day. The causes of DR and subsequent response evolution were analyzed. MRFS was calculated using Kaplan-Meier curves. An event was defined by the loss of stable molecular response or loss of major molecular response (MMR). Results: Sixty-five patients were included, with a median age of 54 years (18-86). Dose reduction TKIs treatment distribution was as follows: Imatinib 11 patients (16.9%) and 54 (83.1%) were under treatment with later lines: Dasatinib 28 (43%); Nilotinib 20 (31%); Ponatinib 5 (7.7%) and Bosutinib 1 (1.5%). The DR was due to toxicity in 51 patients (78.4%): 12 (18.5 %) hematological and 39 (60%) non-hematological: (hepatotoxicity 12.3%, pleural effusion 15.4%, gastrointestinal intolerance 10.8%, skin disorders 4.6%, pulmonary hypertension 4.6%, renal failure 4.6%, myalgia 4.6 %, cardiovascular toxicity 1.5% and pancreatitis 1.5%). Other reasons for DR were persistent deep molecular response or comorbidities (21.5%). TKIs at dose reduction were: Dasatinib 25 mg/50 mg (n:25); Nilotinib 300 mg/450 mg (n:19); Imatinib 200 mg/300 mg (n:11); Ponatinib 15 mg (n:5) and Bosutinib 400 mg (n:1). Sixty three patients (97%) maintained previous MR or achieved MMR after DR, regardless of the cause and previous molecular status. Fifty two patients (81.5%) achieved or maintained MMR at DR with a median duration of 6,7 years (0,3 -13,7). The median follow-up of the entire cohort was 3,23 years ( 0,21-13,7). The MRFS at 5 years was 98,4%. No patient died or progressed to advanced phases. Conclusions: In this study we have observed that DR is effective in maintaining MR and also achieving MMR in a high percentage of patients. The main reason for DR were non-hematological toxicities. Although more evidence is required to incorporate this approach into clinical practice guidelines, our experience might trigger the design of prospective trials to test the use of lower doses of TKI in our region, with possible impact not only on quality of life but also on financial resources in low-income countries.

Introduction: The introduction of tyrosine kinase inhibitors (TKIs) has revolutionized the treatment of chronic myeloid leukemia (CML), bringing the life expectancy of patients close to that of the general population. However, TKI treatment is associated with adverse events, some of them serious or affecting quality of life. In addition, drug costs have a high economic impact, especially in low-income countries. Treatment-free remission (TFR) is an emerging goal for CML patients and it has been associated with cost savings in different country analyses. Main Objective: Assess the economic impact of TKI discontinuation in patients included in the AST2018 Trial. Secondary objective: Estimate the long-term saving in patients included in the AST2018 Trial, considering Argentinian life expectancy. Methods: AST2018 is a multicentric, prospective trial that recruited aged >18 years CML chronic phase patients, with confirmed typical BCR-ABL1 transcripts b3a2 and/or b2a2, under TKI treatment for at least ≥ 4 years and sustained MR4.0 for ≥ 2 years. Molecular tests were centralized in 2 harmonized laboratories and performed monthly for the first 6 months, every 2 months until the 1st year, and every 3 months until month 24. TKI was restarted at confirmed loss of major molecular response (MMR). The economic impact was evaluated by an Excel-based budget impact model, in order to estimate the costs of the patients in first-line pharmacological treatment for CML. We considered the costs of TKI-treatment, PCRs performing and medical visits as money flow. We calculated the present value of savings, in US dollars, in patients who discontinued treatment during the trial. Results: Between February 2018 and March 2022, we evaluated 50 CML patients in the AST2018 trial, 46 were enrolled from 7 centers in Argentina, and were included in this economic analysis. The median patients’ age was 57.5 years (24-85). TKI treatment before discontinuation was Imatinib 34/46 (74%), Nilotinib 4/46 (9%) and Dasatinib 8/46 (17%). After 24 months since first patient was enrolled, 30/46 (65%) patients continued free from TKI, Imatinib 21/34, Nilotinib 2/4 and Dasatinib 7/8, with a median follow-up of 31.3 months (range 25.9 - 38.1). Treatment was restarted after losing MMR in 16/46 (35%) patients. We considered the costs of TKI treatment, PCR performing and physician visits, and we calculated the estimated cost saving per patient at 24 months on TFR: Imatinib US$ 78,433; Dasatinib US$ 102,817 and Nilotinib US $106,161. For the 30 patients who persisted in TFR for 24 months, total cost saving was US$ 2,579,137. For 17 patients who lost MMR, US$ 335,043 dollars were saved previously to TKI reinitiation. Adding up both amounts, the total economic saving in AST2018 was US$ 2,914,181. We performed an analysis of the potential cost savings of remaining in TFR beyond 24 months and according to life expectancy in Argentina (76 years), median age of patients in this trial and cost per patient/year on TKI treatment, the estimated cost saving per patient was US$ 714,512. Conclusions: This is the first economic analysis of the AST2018 trial on TKI discontinuation in CML patients with sustained deep molecular response in Argentina. Our analysis shows that, in spite of the PCR spending, there is a considerable saving in patients on TFR. A careful approach for patients participating in TFR trials or programs will decrease the risk of relapse and make TFR a reality in our region. Potential advantages of TFR will not only impact in patients’ quality of life but also show considerable reduction in the use of economic resources. In developing countries, where lack of molecular monitoring is still an issue outside academic centers, these savings could be redirected to this unmet need making TFR feasible and a goal for the patient and the healthcare system. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

BackgroundHMGCLL1 is characterized as a lyase activity enzyme located in the extramitochondrial region. Its biological and physiological role is not fully elucidated. Our previous study (Leukemia 2019) demonstrated that: 1) The HMGCLL1 gene variant, ACGTAATG haplotype (A-haplotype) is associated with increased expression of overall levels and isoform 3 (IS3) of the HMGCLL1 gene and predicts a decreased likelihood of deep molecular response after Imatinib (IM) therapy, 2) blockade of HMGCLL1 IS3 results in G0/G1 cell cycle arrest, leading to increased eradication of CML cell lines and CML leukemic stem cells, 3) blockade of HMGCLL1 isoform 3 significantly suppressed CD34+ fractions in CML patients (pts). It was unclear whether a second-generation tyrosine kinase inhibitor (2G-TKI) can reverse the adverse impact of the HMGCLL1 gene variant in CML pts. The present study assessed the prognostic impact of the HMGCLL1 gene variant in CML pts treated with IM or 2G-TKI, and its impact on treatment-free remission (TFR) after TKI discontinuation. Patients and methods Samples from 387 pts were sequenced. Group 1 included 252 pts from 2 centers whose samples were archived retrospectively. These pts were treated with IM (n=190, 75.3%) or second-generation TKIs (n=62) including Dasatinib (n=15, 6.0%), Nilotinib (n=37, 14, 7%), and Bosutinib (n=10; 4.0%). Group 2 included 135 patient samples from 4 countries that attempted to discontinue TKI for TFR. We applied our internal CML-specific smMIP panel with 332 amplicon probes including 8 HMGCLL1 SNPs (rs10948926, rs10948927, rs9370435, rs4546489, rs4275061, rs9475323, rs9475327, rs9296791). Linkage disequilibrium (LD) was assessed using Haploview software (Bioinformatics 2005). For Group 1, treatment outcomes were evaluated concerning major molecular response (MMR), molecular response (MR) with 2 log/deeper (MR2) or 4 log/deeper (MR4), failure-free survival (FFS), progression, and overall survival (OS). Disease characteristics and treatment outcomes were evaluated and compared according to the HMGCLL1 variants using a dominant model. For Group 2, molecular relapse-free survival (RFS) was calculated from the date of TKI discontinuation to the date of confirmed loss of molecular response (either loss of major MMR or two consecutive episodes of MR loss). Kaplan-Meier survival estimate was used to evaluate RFS and Cox's proportional hazard regression model was applied using the dominant model. Results HMGCLL1genotype and haplotype As shown in Fig A, the LD plot showed no recombination among the 8 SNPs, leading to one block for the 8 SNPs to construct a haplotype. Two haplotypes were constructed as CTCAGGCA (C-) or ACGTAATG (A-haplotype) with MAF of 0.674:0.279 in Group 1, and 0.703:0.216 in Group 2, respectively. Summary of outcomes in table 1. Treatment outcomes following TKI therapy according to the HMGCLL1 haplotype Homozygous A-haplotype (A/A) was associated with worse outcomes, showing a lower MR2 (65.9% vs 78.9% at 12 months, p=0.012), lower MMR (64.4% vs 86.8% at 3 years, p=0.00029), lower MR4 (34.7% vs 62.3% at 5 years, p=0.0001; worse FFS (62.8% vs 77.3% at 3 years, p=0.0014), higher risk of progression (16.2% vs 3.4% at 5 years, p=0.000678), and worse OS (56.1% vs 77.7% at 10 years, p=0.0021). The adverse impact of A/A-haplotype was more prominent in the pts treated with Imatinib: A/A-haplotype pts showed a 30-50% lower chance of MR2, MMR, and MR4 achievement, and 2-3 times higher risk of TFR and progression in comparison to those having C-haplotype when treated with Imatinib. However, the use of 2G-TKIs could abrogate the adverse impact of the A/A-haplotype. Impact of HMGCLL1 variant on treatment-free remission following TKI discontinuation While the 12-month RFS rate was 59.9% in overall pts (n=135), an inferior 12-month RFS rate was noted in A/A haplotype (43.8% vs 62.3%) but with borderline significance (p=0.116). Conclusion: The present study demonstrated that the HMGCLL1 gene variant is confirmed as predictive of CML outcomes. Moreover, our result suggests that the adverse impact of the HMGCLL1 genotype can be abrogated by using 2G-TKIs as upfront therapy. We aim to validate this data in a larger cohort of pts treated with 2G-TKI therapy to reach a clearer conclusion on this result. HMGCLL1 genotype information would be helpful to guide CML therapy given that pts with adverse HMGCLL1 genotypes could benefit from 2G-TKI therapy as front-line therapy. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Treatment-free remission (TFR) has been accepted as a practical treatment goal in chronic myeloid leukemia (CML) patients. TFR is defined as successful discontinuation (DISC) of Tyrosine Kinase Inhibitor (TKI) therapy without losing leukemia control. Multiple clinical studies have reproduced a consistent TFR rate of about 50%. No definite biomarker has been identified or validated yet. Adnan et al (BCJ 2022) recently reported that epigenetic modifier gene mutations at initial diagnosis of CML are associated with TFR success after TKI DISC. The issue is the time gap between mutation profiling at initial diagnosis of CML and the clinical event of a TFR attempt, which is about 5-10 years. Mutation profiles in the samples obtained before TKI DISC have never been investigated as a TFR predictive marker. Next-generation sequencing (NGS) has been incorporated into clinical practice. Conventional targeted sequencing techniques have limitations such as the high error rate, its limit of detection is up to 2-5%. Mutation frequency and allele frequency (AF) were assumed to be very low in the patients who achieved deep molecular response. Thus, conventional NGS likely misses mutations with low AF. Single-molecule molecular inversion probe (smMIP) is a bar-coded, error-corrected NGS approach, can overcome the high error rate issue by tracking all sequence reads derived from a single strand. This study aims to detect somatic mutations using a smMIP panel to evaluate if the mutations assessed can be a biomarkers for TFR failure. Patients and Methods We applied our in-house CML-specific smMIP panel with a limit of detection up to 0.2%. The panel encompasses 37 genes with 332 amplicon probes: epigenetic modifiers (n=7), activation signaling (n=12), myeloid transcription factor (TF; n=5), spliceosome (n=3), tumor suppressor (n=3), cohesion (n=4) and miscellaneous (n=3). Our cohort included 135 patients who attempted TKI DISC for TFR from 4 countries: Argentina (n=28, 20.7%), Brazil (n=30, 22.2%), Czechia (n=3, 2.2%), Canada (n=34, 54.8%). Disease characteristics and outcomes were evaluated and compared according to the mutation profiles prior to TKI DISC. Molecular relapse-free survival (RFS) was calculated from the date of TKI DISC to the date of confirmed loss of molecular response. An episode of major molecular response (MMR) loss or two consecutive episodes of molecular response loss of 4 logs or deeper response (MR4) constituted molecular relapse. Kaplan-Meier survival estimate was used to evaluate RFS and Cox's proportional hazard regression model was applied. Results Median age was 55.5 years (25-72), 55% males, and Sokal Score risks rates were as follows: Low 51.8%, intermediate 26.8%, High 8.33%. All patients were in chronic phase at diagnosis. A total of 102 pts (78%) stopped Imatinib, while 24 pts (22%) stopped 2GTKI: Dasatinib (n=17) and Nilotinib (n=7). There was no difference in RFS between IM DISC vs. 2GTKI DISC: the patients who stopped IM showed RFS rate of 64.3% (40.9-80.4%) vs those who stopped 2GTKI showed 58% (48.5-67.7%; p=0.634). A total of 59 mutations were detected in 43 (31.9%) patients. TET2 was the most commonly mutated gene (n=15, 11.1%) followed by ASXL1 (n=10, 7.4%) and, DNMT3A (n=9, 6.7%). According to its biologic pathways of the mutation, mutations were detected in the Epigenetic modifiers (n=33, 56%) most frequently, followed by Cohesin (n=16, 27%), activated signaling (n=7, 12%), tumor suppressor (n=3, 5%) and splicing (n=1, 2%). According to the mutational profile before TKI DISC for the TFR attempt, no difference in RFS was observed according to the biological pathways of mutations or according to the presence of mutation (fig 1). Overall RFS at 1 year was 56% (95% CI [45.1-66.1%]) in patients without any mutations comparing to 67.5% (50.7-79.7%) in patients with mutation(s) (p=0.49; fig 2). The RFS rate at 1 year was 58.9% (48.3-68%) in patients with epigenetic mutations compared to 63.3% (43.6.-78.7%) in those without it (p=0.73). Even after adjustment for MR4 duration, we could not identify any predictive profile of RFS. Conclusion Somatic mutations were not infrequently detected in the patients qualified for TFR attempt using a technique detecting up to 0.2% VAF. Mutations in epigenetic genes were most frequently detected. However, it does not seem to have any predictive power for TFR success. Its biological relevance remains to be further investigated in future research. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Tyrosine kinase inhibitors (TKIs) have dramatically changed the survival of chronic myeloid leukemia (CML) patients, and treatment-free remission (TFR) has recently emerged as a new goal of CML treatment. The aim of this work was to develop recommendations for TKI discontinuation in Latin America (LA), outside of clinical trials. A working group of CML experts from LA discussed 22 questions regarding TFR and reached a consensus for TFR recommendations in the region. TFR is indicated in patients in first chronic phase, with typical BCR-ABL transcripts, under TKI treatment of a minimum of 5 years, in sustained deep molecular response (DMR; molecular response 4.5 [MR4.5]) for 2 years. Sustained DMR must be demonstrated on at least 4 international reporting scale quantitative polymerase chain reaction (PCR) tests, separated by at least 3 months, in the immediate prior 2 years. After second-line therapy, TFR is indicated in previously intolerant, not resistant, patients. Molecular monitoring is recommended monthly for the first 6 months, every 2 to 3 months from months 7 to 12, and every 3 months during the second year, indefinitely. Treatment should be reintroduced if major molecular response is lost. Monitoring of withdrawal syndrome, glucose levels, and lipid profile is recommended after discontinuation. After TKI reintroduction, molecular monitoring is indicated every 2 to 3 months until MR4.0 achievement; later, every 3 to 6 months. For the TFR attempt, having standardized and reliable BCR-ABL PCR tests is mandatory. These recommendations will be useful for safe discontinuation in daily practice and will benefit patients who wish to stop treatment in emergent regions, in particular, with TKI-related chronic adverse events.

Chronic myeloid leukemia (CML) is a myeloid stem cell neoplasm characterized by an expansion of myeloid progenitor cells and the presence of BCR-ABL1 oncoprotein. Since the introduction of specific BCR-ABL1 tyrosine kinase inhibitors (TKI), overall survival has improved significantly. However, under long-term therapy patients may have residual disease that originates from TKI-resistant leukemic stem cells (LSC). In this work, we analyzed the miRNome of LSC-enriched CD34+CD38−CD26+ and normal hematopoietic stem cells (HSC) fractions obtained from the same chronic phase (CP) CML patients, and stem and progenitor cells obtained from healthy donors (HD) by next-generation sequencing. We detected a global decrease of microRNA levels in LSC-enriched CD34+CD38−CD26+ and HSC fractions from CML-CP patients, and decreased levels of microRNAs and snoRNAs from a genomic cluster in chromosome 14, suggesting a mechanism of silencing of multiple non-coding RNAs. Surprisingly, HSC from CML-CP patients, despite the absence of BCR-ABL1 expression, showed an altered miRNome. We confirmed by RT-qPCR that the levels of miR-196a-5p were increased more than nine-fold in CD26+ (BCR-ABL1+) vs. CD26− (BCR-ABL1−) CD34+CD38− fractions from CML-CP patients at diagnosis, and in silico analysis revealed a significant association to lipid metabolism and hematopoiesis functions. In the light of recent descriptions of increased oxidative metabolism in CML LSC-enriched fractions, these results serve as a guide for future functional studies that evaluate the role of microRNAs in this process. Metabolic vulnerabilities in LSCs open the road for new therapeutic strategies. This is the first report of the miRNome of CML-CP CD34+CD38− fractions that distinguishes between CD26+ (BCR-ABL1+) and their CD26− (BCR-ABL1-) counterparts, providing valuable data for future studies.

Background: Data on the safety and efficacy of copy drugs is usually unavailable. Imatinib mesylate is used to treat chronic myeloid leukemia (CML) patients in Argentina since 2002. During the last decade more than ten different imatinib copies are marketed by the different health-care systems in the country, usually for cost issues. In spite of the undoubted benefit of this tyrosine-kinase inhibitor indication in CML, there is no solid evidence that supports copy drug equivalent outcomes for this patient population. Aim: To compare the clinical presentation, treatment response and outcome of a chronic phase (CP) CML patient cohort treated with branded and copy imatinib in the real-life setting. Methods: Multicentric, retrospective trial based on data obtained from medical charts of adult CP CML patients treated with imatinib in 9 centers in Argentina from 2002 to 2020.We analyzed demographic characteristics and clinical characteristics described for branded and copy imatinib treated cohorts. Frequency of complete cytogenetic response (CCyR) at 12 months, Major molecular response or better(≥MMR) at 12, 18 and 24 months and overall MR4.0, MR4.5 and deep molecular response (MR4.0 +MR4.5 IS) were analyzed. Event was defined as failure, progression or CML related death. Kaplan Meier comparison of event free, progression free and overall survival. Statistics: IBM SPSS version 1. Results: A total of 568 CP CML adult patients (pt) treated with imatinib were included. Mean age at diagnosis: 45.7 years (range 18 - 85). Male 55.6% (316/568). Sokal Score was recorded in 471 pt: 57% (269/471) low, 26% (122/471) intermediate and 17% (80/471) high-risk. Median follow-up 107 months (RIQ: 36-149). Branded imatinib treatment 330 (58%) and imatinib copies 238 (42%). For branded and copy imatinib cohorts mean age 46,1 (18-85) and 45.3(18-80), male 53% (175/330) and 59% (141/238), median follow up 102 (RIQ 101-130) and 61 (RIQ 62-146) respectively. Sokal score low 58% (164/284) and 56% (105/187), intermediate 27% (77/284) and 24% (45/187) and high 15% (43/284) and19% (37/187). Frequency of CCyR at 12 months 71% (67/94) and 69% (41/59), ≥MMR at 12 months 57% (79/138) and 43% (39/89), ≥MMR 18m 66 % (61/92) and 71% (43/60), ≥MMR 24m 65% (96/147) and 79% (58/73). Overall MR4, MR 4.5 and Deep MR with branded imatinib 62.4% (186/298), 42% (118/276) and 63% (189/300), compared to 45(97/214), 24% (50/207) and 46% (99/215) with copies. Difference in evaluation throughout the treatment periods with loss of data did not allow response rate statistical comparison in predetermined timepoints. Kaplan Meier Event free survival median 229 months vs 75 months p 0.001, Progression free survival mean 318 months vs 208 pt 0.034 and Overall Survival mean 275 months vs 206 months for branded and copy imatinib respectively. Discussion: Several case reports have shown poor outcomes in patients treated with imatinib copy drugs, including loss of responses previously attained with branded imatinib. This study reports data from a large cohort of CP CML patients treated in daily practice during a long period of time. Treatment results at determined timepoints is comparable. Although management and treatment decisions were performed in different time periods, results show different outcomes in EFS and PFS between patients treated with branded vs copy imatinib. Overall survival in both cohorts is comparable. As studies assesing the safety and efficacy of the copy drugs compared with branded imatinib will hardly be performed this evidence calls for careful attention and strict follow up measures when managing CML patients with copy imatinib. Figure Disclosures Varela: Novartis: Consultancy, Speakers Bureau. Pavlovsky:Pint Pharma: Speakers Bureau; Pfizer: Speakers Bureau; BMS: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Freitas:Pfizer: Consultancy, Other: Advisory Board. Pavlovsky:Varifarma: Speakers Bureau; Astra Zeneca: 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, Other: travel grants, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Other: Travel grants, Speakers Bureau. Moiraghi:Novartis: Speakers Bureau; BMS: Speakers Bureau.

INTRODUCTION: Long-term survival of patients with chronic myeloid leukemia (CML) has significantly improved since the introduction of BCR-ABL1 tyrosine kinase inhibitors (TKIs). Several considerations about the side effects, risks and cost associated with the lifetime treatment, have led patients and physicians to explore the possibility of TKI discontinuation after achievement of a sustained deep molecular response (DMR), so-called treatment-free remission (TFR). Several clinical trials show that approximately half of patients who achieve a sustained DMR during TKI treatment maintain molecular remission after suspension of TKIs. There is currently no biomarker that reliably predicts TFR in CML, mainly due to different study designs that have generated inconsistent data. Thus, further investigations are needed to identify factors that consistently favor achievement of TFR. With the aim of developing a biomarker for TFR prediction we analyzed the phenotype of Natural Killer (NK) cells and their relation to successful TKI cessation. METHODS: This analysis was conducted as a substudy of the Argentina Stop Trial. Altogether, 50 consecutive chronic phase CML patients who participated in the clinical trial were recruited from 7 Argentinian centers. Peripheral blood samples were collected before stopping TKI treatment, at month 3, 12 and at any time when MR3.0 was lost. Freshly isolated mononuclear cells from 46 patients were immunophenotyped by staining with CD3, CD16, CD25, CD56, CD57, CD158, NKp30, NKp44, NKp46, NKG2A, NKG2C, NKG2D and PD-1 antibodies and NK cells subpopulations were analyzed by flow cytometry (BD FACS Canto™II). Molecular recurrence-free survival was estimated by the Kaplan-Meier method and compared within groups by the log-rank test. The cutoffs of the numerical variables were optimized according to the log-rank test. Quantitative variables were dichotomized according to receiver operating characteristics (ROC) curves in order to describe sensibility and specificity. Multivariate analysis was performed through Cox proportional hazards model. Main results are provided with hazard ratio (HR) at 6 months and 95% confidence intervals (95% CI). RESULTS: At the time of discontinuation the median proportion of NK cells (CD3-CD56+) among lymphocytes was significantly increased in patients compared with controls (15% vs 9%, P = 0.0016). A significant difference between molecular relapsed vs no-relapsed patients was observed when optimal cutoff (0.43) for CD56bright low and high was determined (at 6 months 74% vs 100% respectively, log rank test, p=0.023). At this time of follow up, no significant difference was observed for CD56dim NK cells. Phenotypic markers for adaptive-like NK cells were analyzed, however, no significant differences were observed between the non-relapsing and relapsing groups. Nevertheless, molecular non-relapsing patients had significantly higher frequencies of PD-1+ NK cells as compared with molecular relapsing patients (at 6 months 85% vs 64%, Log Rank test, P=0.009). Based on the ROC and Youden Index analysis, at 6 months the 1.2 cutoff shows an 80% specificity and 50% sensitivity. Moreover, after multivariable Cox proportional analysis, including age, time of treatment, deep molecular response time, Sokal risk, NK cells and PD-1+ NK cells, the last subpopulation was identified as an independent prognostic factor for molecular-relapse-free survival (Hazard ratio = 3.63; 95% CI 1.3 - 10.1; P=0.014). CONCLUSIONS: The clinical impact of NK cells in patients who have discontinued TKIs is controversial. The effects of TKIs against immune cells, including NK cell subsets, could depend on the type of TKIs; this aspect is particularly relevant in Argentinian treated patients real world, since many different copies of TKIs are routinely used in the clinical setting. Our study is the first, to our knowledge, to report a significant increase in PD-1 expression in NK cells at TKI cessation in patients who do not relapse. Accordingly to recent reports, PD-1 expression is more abundant on NK cells with an activated and more responsive phenotype and does not mark NK cells with an exhausted phenotype. To fully understand how PD-1 on NK cells modulates immune responses we are planning to carry out functional studies. In the future, we are also planning a comprehensive study of immune suppressors, including regulatory T cells and myeloid-derived suppressor cells. Disclosures Moiraghi: Novartis: Speakers Bureau; BMS: Speakers Bureau. Varela:Novartis: Consultancy, Speakers Bureau. Pavlovsky:Varifarma: Speakers Bureau; Astra Zeneca: 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, Other: Travel grants, Speakers Bureau; Janssen: Membership on an entity's Board of Directors or advisory committees, Other: travel grants, Speakers Bureau. Pavlovsky:Pint Pharma: Speakers Bureau; Pfizer: Speakers Bureau; BMS: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Introduction: Treatment-free remission (TFR) is an emerging treatment goal for chronic myeloid leukemia (CML) patients in deep molecular response (DMR). Current evidence shows that 40%-60% of patients relapse while in TFR; and nearly all regain response once tyrosine kinase inhibitors (TKIs) treatment are reinitiated. However a robust predictor of prolonged TFR has not been reported yet. Considering real-life setting, 2 key factors may affect TFR outcome if not properly done: Access to serial molecular monitoring at optimal timepoints and quality laboratory terms as accuracy, sensitivity and rapid results. This motivated the creation of the AST study in our region to guarantee adequate molecular monitoring for TFR in Argentina and characterize new prognostic biomarkers helpful to identify more accurately patients who will be able to sustain TFR. We aimed to assess the proportion of patients with sustained major molecular response (MMR) after TKIs discontinuation and define precise conditions for stopping treatment. Methods: This prospective, multicentre Argentina Stop Trial (AST) trial is recruiting chronic phase CML patients under TKI treatment for at least ≥ 4 years, in DMR (≥MR4.0) sustained for ≥ 2 years in standardized laboratory, confirmed typical BCR-ABL1 transcripts b3a2 and/or b2a2 and aged > 18 years. Molecular tests are centralized in 2 harmonized laboratories and performed monthly for the first 6 months, every 2 months until the first year, and every 3 months during the second year. If patients lost MMR, TKI was restarted immediately. Molecular relapse Free Survival was estimated by Kaplan-Meier method. Difference between survival variables was evaluated through log-rank test. Multivariate analysis was performed through Cox proportional hazards model. The cutoffs of the numerical variables were considered according to the log-rank test. Results: Between February 2019 and July 2020, we evaluated 50 CML patients of whom 46 were enrolled from 7 centers in Argentina and 4 were screening failures. Recruitment was interrupted due to COVID-19 pandemic. Patient median age was 57.5 years (range 24-85). Before discontinuation, TKI treatment was as follows: Imatinib 37/46 (80%), Nilotinib 5/46 (11%) and Dasatinib 4/46 (9%), 2G-TKI as 1st line, 11% of the patients received non-branded treatment. Sokal risk score showed to be low in 22 patients (48%), intermediate in 14 (30%) and high in 10 (22%). Median follow-up was 10 months (range 4-17) and the estimated molecular relapse-free survival was 80.2% (95%CI 69-93) at 6 months Fig 1. Longer DMR durations before discontinuation were associated with increased probability of maintaining response at 6 and 12 months: 83.2% for patients who had >54 months in DMR vs 70% with <54 months and 72% vs 23.3% respectively (p=0.0453) Fig 2. Cox multivariate analysis was performed including different variables as age at diagnosis, time in DMR, time in TKI previous to discontinuation and Sokal risk. The only significant variable associated to improved prognosis was time in DMR (HR 2.8 95%CI 1.002-8.07 p=0.0495). Our cohort had a long time on TKI treatment previous to discontinuation, median 10.5 years (4.16-17.5) probably considering it a favorable factor for the high TFR rates described at 6 months. Among the 46 patients included, 15 (33%) lost MMR, all restarted treatment with the same TKI used before discontinuation, 12/15 (80%) regained MMR with a median time of 3 months (range1-8) and 9/15(60%) obtained MR 4.0 with a median time of 3 months (range1-5). Conclusion: This is the first multicenter study of TKI discontinuation in CML patients in Argentina showing that TKI can be safely discontinued in those who achieve and maintain a DMR before discontinuation. We observed high rates of molecular relapse free survival, although longer follow-up is needed. We must continue with this approach for patients participating in TFR trials or TFR programs in order to decrease the risk of relapse and make this goal a fact in our region. This discontinuation study will allow in a near future significant saving of economic resources and might improve patients quality of life specially in those who are currently experiencing treatment adverse events. Disclosures Pavlovsky: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Speakers Bureau; Pfizer: Speakers Bureau; Pint Pharma: Speakers Bureau. Varela:Novartis: Consultancy, Speakers Bureau. Pavlovsky:Janssen: Membership on an entity's Board of Directors or advisory committees, Other: travel grants, Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees, Other: Travel grants, Speakers Bureau; Astra Zeneca: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Varifarma: Speakers Bureau. Moiraghi:BMS: Speakers Bureau; Novartis: Speakers Bureau.

Chronic myeloid leukemia (CML) is a myeloid stem cell neoplasm characterized by an expansion of myeloid progenitor cells and the presence of BCR-ABL1 oncoprotein. Since the introduction of specific BCR-ABL1 tyrosine kinase inhibitors (TKI), overall survival has improved significantly. However, under long-term therapy patients may have residual disease that originates from TKI-resistant leukemic stem cells (LSC). In this work, we analyzed the miRNome of CML LSC, normal hematopoietic stem cells (HSC) obtained from the same CML patients, and stem and progenitor cells obtained from healthy donors (HD) by next-generation sequencing. We detected a global decrease of microRNA levels in LSC and HSC from CML patients, and decreased levels of microRNAs and snoRNAs from a genomic cluster in chromosome 14, suggesting a mechanism of silencing of multiple non-coding RNAs. Surprisingly, HSC from CML patients, despite the absence of BCR-ABL1 expression, showed an altered miRNome. In silico analysis revealed an association between validated microRNAs and multiple metabolic pathways, suggesting that these molecules may be mediators of the previously reported dysregulation of LSC metabolism. This is the first report of the LSC miRNome that distinguishes between BCR-ABL1 + LSC and their BCR-ABL1 - counterparts, providing valuable data for future studies. * aUPD : acquired uniparental disomy BFU-E : burst-forming unit-erythroid BM : bone marrow CFU-GEMM : colony-forming unit-granulocyte erythroid macrophage megakaryocyte CFU-GM : colony-forming unit-granulocyte macrophage CML : chronic myeloid leukemia FACS : fluorescent-activated cell sorting GO : Gene Ontology HD : healthy donor HSC : hematopoietic stem cells KEGG : Kyoto Encyclopedia of Genes and Genomes LSC : leukemic stem cells LT-HSC : (murine) long-term repopulating hematopoietic stem cell NGS : next-generation sequencing PB : peripheral blood MNC : mononuclear cells Ph : Philadelphia chromosome Pre-L-NSC : pre-leukemic neoplastic stem cells qPCR : quantitative PCR RT : reverse transcription snoRNAs : small nucleolar RNAs snRNAs : small nuclear RNAs TKI : tyrosine kinase inhibitors tRNAs : transfer RNAs

Introduction: Up to 20% of patients (pts) with essential thrombocythemia (ET) and up to 10-15% of pts with polycythemia vera (PV) are diagnosed before the age of 40 years and the percentage is even lower in pts with primary myelofibrosis (PMF). Pregnancy (Pcy) in MPN is associated with an increased incidence of thrombotic and bleeding events and obstetric complications with live birth rates of 50% to 70%. There are no evidence-based guidelines for the management of these pts and most of the data come from case series of few pts. There are no validated variables that can predict outcomes in pregnant women with MPN. Objetives: Primary: To learn the incidence of thromboembolic, hemorrhagic and OC in pregnant women with MPN in Argentina. Secondary: To evaluate parameters such as mutational status, platelet count, history of complications in previous Pcy, use of aspirin (ASA), low molecular weight heparin (LMWH) or interferon (IFN) and their relationship with obstetric outcomes. Materials and methods: Retrospective evaluation of medical records of pts with diagnosis of MPN and Pcy. Quantitative variables were expressed as median and interquartile range (IQR) and qualitative variables as total number and percentage (%). Fisher's exact test was used to analyze variables and their association with events and Wilcoxon test for platelet counts. Results: A total of 30 Pcy in 23 women with a diagnosis of MPN were recorded, 20 Pcy in pts with ET, 4 Pcy in pts with PV and 6 MF pregnancies. Pcy was planned in 56.6% of cases. There were OC in 15/19 previous Pcy. The median age was 32.9 years (IC25-75% 30-36 years). Mutational status was assessed in 22 pts: 9/22 JAK2 +, 7/22 CALR +, 1/22 triple-negative, 1/22 JAK2-CALR- and MPL not performed, 6/22 JAK2- CALR and MPL without data. The overall number of live births and first trimester spontaneous abortions (SA) were 26(86%) and 4(13.3%) respectively, without cases of second (2T) and third trimester (3T) fetal loss or stillbirths. There was a case of neonatal death in a patient with MF. We detected 13 obstetric events (ET: 9/20, PV: 2/4, and MF 2/6): 4 SA, 5 cases of fetal growth retardation, 1 partial placental abruption and 3 placental hematomas. There was no significant association between JAK2 mutational state, history of complications in previous Pcy, platelet count, use of ASA, LMWH or IFN and obstetric outcomes. Two of the pts who had SA presented smoking as a cardiovascular risk factor. There was heterogeneity among hematologist regarding therapeutic management: ASA was indicated in 24 Pcy and LMWH in prophylactic doses during Pcy in 15. In 21/25 cases LMWH was indicated as postpartum prophylaxis, only in 3/21 it was extended for 6 weeks(wks). Before Pcy 17 cases received cytoreductive treatment: 2 with HU and 1 with anagrelide that were discontinued at the time Pcy was confirmed, 5 with peg IFN, and 9 conventional IFN. During Pcy 8 continued with cytoreductive treatment (6/9 conventional IFN, 2/9, pegIFN, including 1 patient previously receiving HU) and 5 initiated IFN (1/5 conventional, 4/5 pegIFN). Platelet counts in pts who did not require cytoreduction dropped from 600 x 109/L (290-1596 x 109/L) at the beginning of Pcy to 470 (240-1548) x 109/L, p=0.0068, and 423 (240-843) x 109/L, p=0.0005, in the 2T and 3T, respectively, with non-significant increase after delivery to 494 x 109/L (122-1600 x 109/L). No cases of maternal thrombosis and 2 episodes of major postpartum bleeding who required surgical intervention one of them with hysterectomy were found.The median time of delivery was at 38 wks of gestation (IC25-75% 36.5-38.5). Vaginal delivery was performed in 6 Pcy, caesarean section (CS) was required due to emergency in 2, because of lack of fetal progression in 2, and 16 were scheduled CS. The median birth weight was 2900g (IC25-75% 2500-3300g). No congenital malformations in live births were detected. Conclusions: Pcy is a rare but high-risk event in MPN pts with 11/30 OC in this cohort. The live birth rate was high compared to the literature. The risk of MC was low, without thrombotic complications and 2/30 episodes of major postpartum bleeding. There was no correlation between mutational status, platelet count or treatments received and obstetric outcomes. There was a significant reduction in the number of platelets in pts with thrombocytosis without requiring cytoreduction. The high percentage of pts who finished their pregnancy with scheduled CS is highlighted. Disclosures No relevant conflicts of interest to declare.

Ph negative myeloproliferative neoplasms (NMP), polycythemia vera (PV), essential thrombocythemia(ET) and primary myelofibrosis (MF), are clonal hematopoietic disorders characterized in their chronicphase by an overproduction of differentiated hematopoietic cells. Hydroxyurea (HU) is an antineoplasticagent belonging to the family of antimetabolites. (According to ELN guidelines, it is recommended as first-line cytoreductive therapy). It is the cytoreductive agent recommended in the first line by the European Leukemia Net (ELN). The aim of this work was to describe the criteria for the initiation of cytoreductive treatment, vascular complications and response rates, intolerance, resistance and progression to myelofibrosis or AML in a population of patients with NMP treated with hydroxyurea in Argentina. 419 patients referred by 63 members of the SAH, belonging to 37 institutions, diagnosed between 1986 and 2017 were included, of which 417 were available for analysis. We observed that the main reason for starting treatment was age (51%), followed by the presence of vascular risk factors (26.6%), thrombocytosis (24.7%) with an average platelet count 1.052 x 109/L (DS 360.32) and previous thrombosis (16.8%). Complete hematological responses lasting at least three months were obtained in PV and TE (61 and 66%). The presence of arterial and venous thrombosis had a similar frequency (14%). The use of HU significantly reduced the risk of thrombosis in the higher risk group. The clinical course and complications of the patients studied with PV JAK2 and positive JAK2 TE were similar and adverse events due to the use of HU were mild but frequent (32.6%).

BACKGROUND RESPONSE is an ongoing, multicenter, open-label, phase 3 trial comparing the efficacy and safety of rux with BAT in patients (pts) with PV who are resistant to or intolerant of hydroxyurea (HU). Primary analysis and 80-week (wk) follow-up results from RESPONSE have been published previously. The 80-wk follow-up data confirmed that the probability of maintaining primary and hematocrit (Hct) responses with rux treatment was 92% and 89%, respectively, and hence, rux could be an effective long-term therapy option for hydroxyurea (HU)-resistant/intolerant (R/I) pts with PV. Here, we report the long-term efficacy and safety updates of rux treatment in RESPONSE trial after a follow-up of 208 wks (after last pt first treatment visit). METHODS This was a preplanned follow-up when all pts completed the wk 208 visit or discontinued. Pts who were R/I of HU per modified ELN criteria, were aged ≥ 18 years (y), with splenomegaly, and phlebotomy (PBT) requirement to control Hct were eligible. Pts were randomized 1:1 to receive open-label rux 10 mg bid or BAT (selected based on investigator's choice). Pts randomized to BAT could crossover (CO) to rux after wk 32. The primary response was a composite endpoint of achieving both Hct control without PBT (defined as no PBT eligibility between wks 8 to 32 with no more than 1 PBT eligibility from randomization to wk 8) through wk 32 and a ≥ 35% of reduction in spleen volume (SVR) by imaging at wk 32. Durability of the primary response, overall clinicohematologic response (CLHM; Hct control without PBT, platelet count ≤ 400 × 109/L, a WBC count ≤ 10 × 109/L, SVR ≥ 35% by imaging) as well as the long-term safety were updated at wk 208 . RESULTS Overall, 222 pts were randomized (rux, 110; BAT, 112) and BL characteristics were overall similar between arms, though more pts randomized to rux had prior history of nonmelanoma skin cancer (NMSC) or pre-cancerous skin conditions (10.9 vs 6.3%) and longer prior exposure to HU (162.9 vs 145.6 wks) compared to BAT arm. At the wk 208 analysis, 41 pts (37%) originally randomized to rux arm were still receiving therapy (median exposure, 225 wks) vs no pts on BAT (median exposure, 34 wks). Among the pts in rux arm, 29% completed the treatment as per protocol. Of 98 pts who crossed over to rux after wk 32, 38% remained on rux (median exposure, 189 wks) and 31% completed treatment. Other main reasons for the study drug discontinuations (rux + CO pts) were disease progression (11% + 8%), pt decision (6% + 6%), and adverse events (AE, 14% + 14%). At the time of analysis in rux arm, 6 of 25 primary responders and 21 of 70 pt who achieved overall CLHM have progressed. Median duration of primary and CLHM responses has not been reached (Figure 1). The KM estimate at 208 wks of duration of primary and CLHM responses for rux arm are 0.73 (95% CI: 0.49, 0.87) and 0.67 (95% CI: 0.54, 0.77), respectively. The KM estimates for overall survival at 5 y were 90.6% (95% CI: 80.1, 95.7) in the rux arm and 87.7% (95% CI: 74.8, 94.3) in the BAT arm. Since wk 80 in rux arm, there were 2 new on-treatment deaths (adenocarcinoma gastric [n = 1, investigator-suspected event to be related to study drug] and neoplasm malignant [n = 1, investigator assessed it not related to study drug]). In the CO population, there were 4 pts who died and had fatal AEs leading to 4 on-treatment deaths (not related to rux). The most frequent AEs (> 20%) in the rux arm (wk 208 vs wk 80) were anemia (35% vs 27%), pruritus (27% vs 20%), diarrhea (26% vs 20%), headache (23% vs 22%), arthralgia (22% vs 13%), weight increased (21% vs 16%), and muscle spasms (20% vs 16%). The most frequent AE (> 20%) in CO pts (wk 208 vs wk 80) was anemia (29.6% vs 22.4%). In the rux arm and CO pts, incidence of thromboembolic events (wk 208 vs wk 80) was 4.5% vs 6% and 9.2% vs 6.1%. The exposure-adjusted rate of overall malignancies in rux was 6.8 (wk 208) vs 6.1 (wk 80) per 100 pt-ys and 4.5 per 100 pt-ys in CO pts (wk 208).The exposure-adjusted rate of NMSC in rux was 5.1 (wk 208) vs 4.4 (wk 80) per 100 pt-ys. In the CO pts, exposure-adjusted rate of NMSC was 2.6 (wk 208) vs 2.0 (wk 80) per 100 pt-ys. At wk 208, the rates of transformation to MF and AML in rux arm were 2.2 and 0.2 per 100 pt-yrs, respectively, and 1.9 and 0.3 in CO pts. CONCLUSION At wk 208 analysis of data from RESPONSE study, the overall safety profile remained consistent with the 80-wk data, and the response was durable. In both the rux arm and CO population, around 30% of pts completed the study treatment and 37% of pts were still receiving the treatment. Download : Download high-res image (82KB) Download : Download full-size image Disclosures Kiladjian: Celgene: Membership on an entity's Board of Directors or advisory committees; AOP Orphan: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding. Verstovsek: Roche: Research Funding; Roche: Research Funding; Blueprint Medicines Corp: Research Funding; Genentech: Research Funding; Seattle Genetics: Research Funding; Astrazeneca: Research Funding; Blueprint Medicines Corp: Research Funding; Gilead: Research Funding; Astrazeneca: Research Funding; Lilly Oncology: Research Funding; Seattle Genetics: Research Funding; Promedior: Research Funding; Incyte: Research Funding; CTI BioPharma Corp: Research Funding; CTI BioPharma Corp: Research Funding; Promedior: Research Funding; Celgene: Research Funding; Incyte: Research Funding; Celgene: Research Funding; Pfizer: Research Funding; Pfizer: Research Funding; Bristol Myers Squibb: Research Funding; Galena BioPharma: Research Funding; Genentech: Research Funding; Galena BioPharma: Research Funding; Lilly Oncology: Research Funding; NS Pharma: Research Funding; Bristol Myers Squibb: Research Funding; NS Pharma: Research Funding; Gilead: Research Funding. Griesshammer: Baxalta: Consultancy, Honoraria, Speakers Bureau; Sanofi: Honoraria, Speakers Bureau; Gilead: Consultancy, Honoraria, Speakers Bureau; AOP Orphan: Consultancy, Honoraria, Speakers Bureau; Shire: Consultancy, Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau. Masszi: BMS: Consultancy; Janssen-Cilag: Consultancy; Novartis: Consultancy; Pfizer: Consultancy; Takeda: Consultancy; AbbVie: Consultancy. Durrant: Novartis: Honoraria, Speakers Bureau. Passamonti: Novartis Pharmaceuticals Corporation: Consultancy, Honoraria, Speakers Bureau. Harrison: Gilead: Consultancy, Speakers Bureau; Shire: Speakers Bureau; Celgene: Consultancy; Novartis: Honoraria, Research Funding, Speakers Bureau; CTI: Speakers Bureau. Pane: Novartis: Honoraria, Speakers Bureau. Kirito: Novartis Pharma KK: Honoraria. Besses: Novartis: Honoraria, Research Funding; Shire: Honoraria. Hino: Novartis: Research Funding. Varela: Novartis: Honoraria, Speakers Bureau. Miller: Novartis: Honoraria, Speakers Bureau; Gilead: Honoraria, Research Funding; Incyte: Consultancy, Honoraria, Research Funding, Speakers Bureau. Mesa: CTI BioPharma Corp.: Research Funding; Gilead Sciences, Inc.: Research Funding; Incyte Corporation: Research Funding; Ariad: Consultancy; Promedico: Research Funding; Celgene Corporation: Research Funding; Galena Biopharma, Inc.: Consultancy; Novartis Pharmaceuticals Corporation: Consultancy. Dong: Novartis: Employment. Francillard: Novartis: Employment. Laughlin: Novartis: Employment. Vannucchi: Novartis: Honoraria, Speakers Bureau; Shire: Speakers Bureau.

Introduction: Early reduction of BCR-ABL transcript level has been associated with improved outcomes in CML treatment. Inability to achieve early molecular response(MR) at 3 months (M3>10%) is considered a predictor factor for unfavourable outcome. However, the kinetics of BCR-ABL transcript level reduction measured at early time points have shown to be an independent predictor of response.The aim of this analysis was to determine whether the "M3-M6" status is critical to categorize CML patients (pts) focusing in high-risk group.

BCR-ABL transcript levels (IS%BCR-ABL) in CML patients (pts) allow to define molecular response (MR) to TKIs. MR at 3 months (M3>10%) is the strongest predictor of bad outcome and a point of divergence for changing therapy. Emerging biomarkers are being proposed in order to optimize prognosis in addition to initial MR and other clinical markers. The rate of BCR-ABL decline measured as halving time (HT) for transcript level reduction (RT0.5) at month 3 in 1GTKI (imatinib) treated pts, and the fractional clearance as a relative BCR-ABL ratio (RR3) during the first 3 months in 2GTKI (dasatinib) treated pts were recently proposed as predictive markers of outcome. Optimal responses (OR) were defined upon %ISBCR-ABL values at 3, 6 and 12 months: M3 ≤10%, M6 ≤1% y M12 ≤0,1%. Early time point prognostication could allow better outcome predictions and rapid therapeutic interventions. Aim: to determine whether the rate of BCR-ABL decline as HT and the BCR-ABL transcripts reduction as relative ratio at M3 from baseline, have predictive value in CML pts treated with 2GTKIs. Method: BCR-ABL transcript level was measured by Q-PCR according international recommendations and results were reported as BCR-ABL/ABL on the international scale (IS BCR-ABL %). Molecular monitoring was performed prior treatment (M0) and at months 3 (M3), 6 (M6), 12 (M12) and every 6 months thereafter. RT0.5 from baseline to M3 was calculated as the time to halve by considering an exponential model of reduction during the period. The median RT0.5 and quartiles, were calculated to define rapid declines as those HT in the lowest quartile. RR3 was determined as a relative ratio of transcript clearance at M3 from baseline. The median RR3and quartiles, were considered to define high BCR-ABL clearance as those in the highest quartile. Fisher statistical test was used to determine whether the proportions of good responses were statistically different depending on the decline rate. Results: A total of 77 CML pts were included, first line treatment: Dasatinib (D) 28%, Nilotinib (N) 32% and Imatinib (I) 40%. Sokal risk score was available in 70% pts: low (L) 67%, intermediate (In) 22% and high (H) 11%. Molecular assessment: prior therapy M0 (90%), M3 (60%), M6 (79%), M12 (78%) and M0+M3+M12(39%). Deep responses (MR4.0) were considered as IS%BCR-ABL 0,1% and without MR4.0. All of these pts showed RT0.5 >13d and RR3 Conclusions: Faster BCR-ABL decline and high clearance were related to OR and MR4.0 achievement in 2GTKIs patients. No direct relation between Sokal Index and M12≤ 0,1% was observed. Patients with RT0.5 ≤13d showed higher frequencies of good responses. Statistical differences were not found probably due to low sample numbers. Our data suggests that RT0.5 in 2GTKIs (N+D) patients could have a similar predictive value as reported by Branford in 2014, even though it is known that BCR-ABL measurements tend to be less satisfactory when control gene is ABL, owing to possible non-linear ratios. Whilst there were no statistical correlations probably due to the low sample number, pts with OR but no MR4.0 had low reduction rate RR3 99% could provide a stronger predictive value for milestone optimal responses achievement in high risk pts. It will be necessary to extend this study including a higher number of patients treated with 2G TKIs. Disclosures Varela:Bristol Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau. Moiraghi:Novartis: Speakers Bureau; Bristol Myers Squibb: Speakers Bureau. Pavlovsky:Novartis: Honoraria, Speakers Bureau; Janssen: Honoraria, Speakers Bureau. Pavlovsky:Bristol Myers Squibb: Honoraria, Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau.

INTRODUCTION: Ponatinib is a potent TKI indicated in T315I mutated CML and not mutated CML resistant to other drugs. Deep responses were reported in PACE trial in patients who had failed all other TKIs in chronic and advanced phase CML with acceptable toxicity profile. Ponatinib use is authorized in United States and Europe but compassionate use allows access in Argentina with no previous reports of local results.

Abstract Introduction MF is a myeloproliferative neoplasm characterized by bone marrow fibrosis, splenomegaly, cytopenias and constitutional symptoms. Since the identification of JAK2V617F mutation and development of anti JAK molecules, the course of the disease has changed. Ruxolitinib is a JAK1 and JAK2 inhibitor recently approved for patients (pts) with primary and secondary MF. In Argentina, pts could access the ruxolitinib through CUP. Analysis of this multicenter protocol provides a preliminary data set, follow up and efficacy results. Objectives To assess the efficacy (reduction in spleen size/improvement in constitutional symptoms) and toxicity. To investigate risk groups modifications during follow-up. Methods In Argentina, 36 pts with myelofibrosis, including primary MF (PMF) and post polycythemia vera (PPV) received ruxolitinib through CUP regardless of JAK2 mutational status. Study period: September 2011 to June 2013. The participating physicians provided information of the disease characteristics by completing a data form. Splenomegaly was evaluated by physical exam, and constitutional symptoms were categorized as present or absent. Retrospective analysis was performed based on data at baseline (n 36), after 3 months (n 30), 6 months (n 24) and 12 months (n 14). Results Median follow-up is 10 months (1-20). The median age is 65 years (30-79), 64% were men and 36% women. There were 72% positive for the JAK2 V617F mutation, 69% had PMF and 31% Post-PV. At admission 89% of pts had received ≥1 lines of therapy for MF prior to ruxolitinib: hydroxyurea 77%, thalidomide 26%, erythropoietin 23%, others: corticosteroids, interferon, anagrelide, danazol, busulfan, splenic radiation, cytarabine, and 6-mercaptopurine. The distribution of risk category according to DIPSS was: 61% high, 19% Intermediate 2, 17% Intermediate 1, and 3% low. Median value for spleen size was 15 cm (4-33) below the costal margin. Constitutional symptoms were present in 71% of the patients and 33% were transfusion dependent. ECOG (Eastern Cooperative Oncology Group) was zero 28%, one 44%, two 22%, three 3%, and four 3%. The median hemoglobin, leucocytes and platelets was 10 g/dl (4.8-15.2); 13, 4 x 109/L (3.6-64) and 217 x 109/L (75-850), respectively. Peripheral blood blasts ≥ 1% in 44% of pts. Ruxolitinib therapy was initiated at 40 mg/d in 16 pts (50%), 30 mg/day in 9 pts (28%), and at a lower dose in the minority of pts. The median value for spleen size at 3, 6 and 12 months was 10, 8 and 6.5 cm, representing decrease of 20%, 41% and 42% from baseline, respectively (fig 1.). In 13 of 29 pts (45%) spleen size decreased ≥ 50% in 3 months. Constitutional symptoms not present at 3, 6 and 12 months in 79%, 100% and 87% of pts, respectively. Improvement in ECOG class was noted in 73%, 69 % and 73% at the above mentioned time points, respectively. Persistence of transfusion dependence at 3, 6 and 12 months was seen in 33, 24 and 27% of the patients. Hemoglobin median levels during treatment (g/dL): at baseline 10.1, at 3 months 8.5, at 6 months 9.7, and at 12 months 9.5. During follow-up, 27% pts shifted to a lower risk group, 2 pts (7%) to a higher group due to worsening anemia, and 67% did not change its category. Hematologic adverse events (AE) were anemia and thrombocytopenia in 8 pts (Grade 1 and Grade 3 according to CTCAE v4.0), 31% of pts required dose adjustment. There were no suspensions of medication because of cytopenia. Others AE > 10% were: headache, musculoskeletal pain, and diarrhea ( Conclusion Ruxolitinib is an effective therapy that reduced spleen size and improved constitutional symptoms with an acceptable toxicity profile in this group of pts. During follow up at 12 months, a quarter of pts shifted to a lower risk group. Our data is consistent with previous reports Disclosures: Barreyro: GSK: Employment. Enrico:Bristol Myers Squibb: Speakers Bureau; Pfizer: Membership on an entity’s Board of Directors or advisory committees; Novartis: Membership on an entity’s Board of Directors or advisory committees. Lanari Zubiaur:Novartis: Membership on an entity’s Board of Directors or advisory committees. Pavlovsky:Novartis: Consultancy. Sackmann:Novartis: Membership on an entity’s Board of Directors or advisory committees. Bengió:Novartis: Member advisory Board Myelofibrosis Other.