ALBERT

Description: 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

Description: 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.

Description: 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.