Abstract: Several studies have reported that chronic myeloid leukaemia (CML) patients expressing e14a2 BCR::ABL1 have a faster molecular response to therapy compared to patients expressing e13a2. To explore the reason for this difference we undertook a detailed technical comparison of the commonly used Europe Against Cancer (EAC) BCR::ABL1 reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) assay in European Treatment and Outcome Study (EUTOS) reference laboratories ( n  = 10). We found the amplification ratio of the e13a2 amplicon was 38% greater than e14a2 ( p  = 0.015), and the amplification efficiency was 2% greater ( P  = 0.17). This subtle difference led to measurable transcript-type dependent variation in estimates of residual disease which could be corrected by (i) taking the qPCR amplification efficiency into account, (ii) using alternative RT-qPCR approaches or (iii) droplet digital PCR (ddPCR), a technique which is relatively insensitive to differences in amplification kinetics. In CML patients, higher levels of BCR :: ABL1/GUSB were identified at diagnosis for patients expressing e13a2 ( n  = 67) compared to e14a2 ( n  = 78) when analysed by RT-qPCR ( P  = 0.0005) but not ddPCR ( P  = 0.5). These data indicate that widely used RT-qPCR assays result in subtly different estimates of disease depending on BCR::ABL1 transcript type; these differences are small but may need to be considered for optimal patient management.

Abstract: Background The iCMLf CANDID study represents the largest global cohort study to date characterizing COVID-19 in CML. This real world data collection, from 157 institutions in 49 countries, is essential to differentiate impact of patient, disease, and therapy specific factors on risk and outcomes, as the pandemic continues. Objective The primary aim of the CANDID study is to collect and analyze information on COVID-19 cases among CML patients (pts) to define risk factors, clinical evolution and outcome. Patients and methods Since March 2020, the iCMLf has collected data, with contributions from physicians treating CML pts and partner organizations. Country income was determined according to the World Bank Data. COVID-19 severity was classified according to the World Health Organization criteria. Univariate analysis was performed using log-rank test or logistic regression. Multivariate analysis was performed using Cox proportional hazards model or multivariate logistic regression. All the statistical analysis was performed using R statistical software (version 4.0.2). Results By April 2021, 642 cases of COVID-19 were reported from 50 countries. COVID-19 was diagnosed by PCR and/or serology in 601 pts (94%) and clinically suspected in 41 pts (6%). These 642 pts were reported by 186 physicians managing an estimated 37,449 CML pts (approximate incidence 0.7%). Most cases reported were from Europe (52%), followed by Asia (18%) and South America (16%). North America reported 10% of the cases and Africa 2.8%. The median age at the time of COVID-19 diagnosis was 53 years (18-94) and 59% of pts were males. Median time from CML diagnosis to COVID-19 was 8.34 years (range: 0-34). CML treatment at the time of COVID-19 diagnosis: hydroxyurea in 4 pts (6%), 38 (6%) bosutinib, 96 (15%) dasatinib, 275 (43%) imatinib, 92 (14%) nilotinib, 18 (3%) ponatinib, 3 (0.5%) other 4th generation TKIs; one alpha interferon. Ninety-nine (15%) pts were not receiving any treatment: 53 (8%) were in treatment free-remission (TFR) and 46 were without treatment (7%) for other reasons: treatment side effects (7), stem cell transplantation (12), pregnancy (3), lack of efficacy (2), unknown (1) and newly diagnosed CML (21). Significant comorbidities were present in 281 pts (44%), most common were: heart conditions, including hypertension (162), diabetes (76), lung diseases (47) obesity (42) and others (84). COVID-19 was asymptomatic in 53 cases (8%), mild in 363 cases (56%), moderate in 119 cases (18%), severe/critical in 86 cases (13%) and of unknown severity in 21 cases (3%). At the data cut-off, from the 606 pts with known outcome, 48 pts died (8%) and 558 (92%) recovered. Age & gt;75y (Fig 1A, p & lt;0.001), comorbidities (Fig 1B, p=0.039), low income country (Fig 1C, p & lt;0.001), advanced phase CML at time of COVID-19 (Fig 1D, p & lt;0.001) had statistically significant association with overall survival (OS) in CML pts with COVID-19. OS was 71% in low or lower middle income countries, 93% in upper middle and 95% in high-income countries (Fig 1C, p & lt;0.001). The mortality rate for pts with cardiovascular disease; heart failure, coronary artery disease, cardiomyopathies, hypertension, stroke or cerebrovascular disease (12%), and chronic lung disease (13%) were higher than those pts with other comorbidities (6%), or without comorbidities (4%; p=0.003; Fig 1E). By multivariate analysis, all these risk factors remained significantly associated with OS. For pts who were hospitalized with severe disease, age & gt;75y (p=0.037), comorbidities (p=0.001), male gender (p=0.01), CML status (AP/BC vs CP in MMR; p=0.049), CML treatment (pre-TKI vs TFR; p=0.02) and length of time with CML (p & lt;0.05) were significant risk factors for mortality. By multivariate analysis, all the risk factors except age remained significant. The risk factors for mortality for pts with moderate, severe, or critical disease were age & gt;75y (p=0.003) and low and lower middle income countries (p & lt;0.001), both confirmed by multivariate analysis. Conclusions We confirmed a higher mortality for CML pts with COVID-19 in older pts ( & gt;75y), pts with cardiovascular or pulmonary comorbidities and from low and low-middle income countries, the latter probably related to limitations in supportive care. Additionally, more deaths occurred in pts in advanced phases and in pts not in MMR. Acknowledgment The iCMLf CANDID Study would not have been possible without the 186 physicians who contributed case reports. Figure 1 Figure 1. Disclosures Pagnano: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Astellas: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Pintpharma: Other: Lecture; EMS: Other: Lecture; Jansenn: Other: Lecture. Mauro: Sun Pharma / SPARC: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Pfizer: Consultancy; Takeda: Consultancy; Novartis: Consultancy, Research Funding. Cortes: Takeda: Consultancy, Research Funding; Bio-Path Holdings, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Research Funding; Bristol Myers Squibb, Daiichi Sankyo, Jazz Pharmaceuticals, Astellas, Novartis, Pfizer, Takeda, BioPath Holdings, Incyte: Consultancy, Research Funding; Sun Pharma: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Evans: Pfizer: Research Funding. Milojkovic: Pfizer: Honoraria, Speakers Bureau; Bristol-Myers Squibb: Honoraria, Speakers Bureau; Novartis: Honoraria, Speakers Bureau; Incyte: Honoraria, Speakers Bureau. Moiraghi: Novartis, Pfizer, Takeda: Speakers Bureau. Nicolini: Incyte Biosciences: Honoraria, Other: travel, accommodations, expenses, Research Funding, Speakers Bureau; BMS: Honoraria; Kartos Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Sun Pharma Ltd.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel, accommodations, expenses, Research Funding. Rea: Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees. Hughes: Novartis: Honoraria, Research Funding; BMS: Research Funding; Takeda: Honoraria.

Abstract: Introduction: The in-study and out-study sections of the European Treatment and Outcome Study (EUTOS) registry comprise data on imatinib-treated adult patients with chronic myeloid leukemia (CML) who were prospectively enrolled in clinical studies or registries between 2002 and 2006. All patients diagnosed with chronic-phase Philadelphia chromosome-positive CML were eligible for analysis. The new EUTOS long-term survival (ELTS) score was developed in 2,205 in-study patients (Blood 2014; 124(21):153). Its purpose is the discrimination of three risk groups with clinically significantly different probabilities of dying from CML. The score was validated in 1,120 out-study patients. Aims: Up to now, many investigators still apply the Sokal score for the prognostic discrimination of CML-patients treated with tyrosine kinase inhibitors (TKIs). The Sokal score allocated more than 20% of chronic-phase patients to the high-risk group while it was 12% with the new ELTS score. Long-term outcome with tyrosine kinase inhibitors (TKIs) suggests that the allocation of more than 20% chronic-phase CML patients into a high-risk group is too pessimistic. The focus of this analysis was the comparison of risk group allocations and prognosis between the two scores. Methods: Survival time was calculated from the date of start of treatment to death or to the latest follow-up date. Survival was censored at the time of allogeneic stem cell transplantation in first chronic phase. Cumulative incidence probabilities (CIPs) of dying of CML were compared with the Gray test and overall survival probabilities with the log-rank test. As "death due to CML", only death after confirmed disease progression was regarded. Progression was defined in accordance with the recommendations of the ELN (Baccarani et al, Blood 2013). Level of significance was 0.05. Results: Both registries combined, the 3,325 patients had a median observation time of 6.1 years. Six-year overall survival probability was 91% (95% confidence interval (CI): 89-92%). Death was due to CML in 142 of 309 deceased patients (46%).The 6-year CIP of dying of CML was 4% (CI: 4-5%). From low to high risk groups, the Sokal score resulted in 6-year CIPs of 3% (n=1358 (41%), CI: 2-4%), 4% (n=1209 (36%), CI: 3-5%), and 8% (n=758 (23%), CI: 6-11%) and the ELTS score in 6-year CIPs of 2% (n=2030 (61%), CI: 2-3%), 6% (n=898 (27%), CI: 4-7%), and 13% (n=397 (12%), CI: 10-17%). Of the 758 patients allocated to high risk by the Sokal score, the ELTS score classified 165 (22%) as low risk and 265 (35%) as intermediate risk. Compared to the 328 high-risk patients (43%) according to both scores (6-year CIP of dying: 13%, CI: 9-17%), the CIPs of dying were significantly lower for the 165 low-risk patients (p=0.0062, 6-year CIP: 5%, CI: 2-9%) and for the 265 intermediate-risk patients (p=0.0050, 6-year CIP: 5%, CI: 3-9%). These 430 Sokal high but ELTS non-high-risk patients (6-year OS: 89%. CI: 86-92%) showed significantly higher OS probabilities than the 328 Sokal and ELTS high-risk patients (p=0.030, 6-year OS: 81%. CI: 76-85%). Of the 2030 patients identified as low risk by the ELTS score, the Sokal score allocated 603 (30%) to the intermediate- and 165 (8%) to the high-risk group. Without significant CIP differences to the latter group, at 6 years, the CIP of dying was 2% (CI: 1-3%) in the 1262 low-risk and also 2% in the 603 intermediate-risk patients (CI: 1-3%). The OS probabilities of the 768 non-low-risk patients according to the Sokal score (6-year OS: 93%. CI: 91-95%) were not significantly different from the 1262 classified as low-risk by both scores (6-year OS: 95%. CI: 93-96%). Conclusions: To be able to perform comparisons between the various prognostic groups suggested by the Sokal and the EUTOS survival score with a reasonable power, data of in- and out-study samples were combined. The Sokal score allocated an absolute difference of 12% (n=430) more patients to the high-risk groups than the EUTOS survival score. As these patients had significantly and clinically relevantly lower CIPs and higher OS probabilities, the allocation of the Sokal score was not appropriate. Contrarily, the long-term outcome of 768 patients assessed as low-risk by the ELTS and non-low-risk by the Sokal score was not different from the outcome of 1262 assesses as low-risk patients by both scores. For prognosis of long-term survival outcome, the use of the EUTOS survival score is recommended. Disclosures Pfirrmann: BMS: Consultancy, Honoraria; Novartis Pharma: Consultancy, Honoraria. Hasford:Novartis: Research Funding. Saussele:Novartis Pharma: Honoraria, Other: Travel grant, Research Funding; BMS: Honoraria, Other: Travel grant, Research Funding; ARIAD: Honoraria; Pfizer: Honoraria, Other: Travel grant. Turkina:Bristol Myers Squibb: Consultancy; Pfizer: Consultancy; Novartis Pharma: Consultancy. Prejzner:Novartis Pharma: Honoraria; BMS: Honoraria. Steegmann:Novartis Pharma: Consultancy, Honoraria, Research Funding; Bristol Myers Squibb: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria, Research Funding. Simonsson:Novartis Pharma: Research Funding. Zaritskey:University of Heidelberg: Research Funding; Novartis: Consultancy. Zackova:Novartis Pharma: Consultancy; Bristol Myers Squibb: Consultancy. Janssen:Novartis: Research Funding; Pfizer: Consultancy; Bristol Myers Squibb: Consultancy; ARIAD: Consultancy. Cervantes:Novartis: Consultancy, Speakers Bureau; Sanofi-Aventis: Consultancy; CTI-Baxter: Consultancy, Speakers Bureau. Hehlmann:Novartis Pharma: Research Funding; BMS: Consultancy. Baccarani:Novartis: Consultancy, Honoraria, Speakers Bureau; BMS: Consultancy, Honoraria, Speakers Bureau; Pfizer: Consultancy, Honoraria, Speakers Bureau; Ariad: Consultancy, Speakers Bureau.

Abstract: Abstract 1239 Background. Imatinib (IM), a selective BCR-ABL tyrosine kinase inhibitor (TKI), is a treatment of choice for newly diagnosed chronic myeloid leukemia (CML) patients (pts) in chronic phase (CP) as it was shown in the IRIS trial. The treatment strategy and response evaluation is based on NCCN or ELN guidelines. Only limited “real life” data of IM impact on pts outcome as well as ELN (European LeukemiaNet) recommendations applicability in daily practice has been published. In the Czech as well as in the Slovak Republic (15 million inhabitants), the treatment of CML patients is centralized in overall 13 centers, capable carrying on both the treatment and laboratory monitoring. There are two CML prospective projects CAMELIA and INFINITY focused on CML pts analysis. Aims. To analyze the treatment response and long-term outcome in consecutive, unselected patients with CP-CML treated with IM and to evaluate the prognostic role of ELN 2006 and 2009 response evaluation. To analyze molecular response in more detail. Methods. Altogether 458 consecutively included patients in INFINITY (152 pts) and CAMELIA projects (306 pts) were assessed. For the treatment response evaluation the ELN 2006 and ELN 2009 definitions were used. We assessed rates and the cumulative incidences of complete hematologic responses (CHR), complete cytogenetic responses (CCyR), major (MMoR) and complete molecular responses (CMoR). Overall survival (OS) was defined as the time from the start of IM to death from any cause, overall survival CML-related death (OSCML), transformation-free survival (TFS) as survival without evidence of AP or BP or death from any cause, progression-free survival (PFS) as survival without evidence of AP or BP, loss of CHR, MCyR, increasing white blood cell count or death fron any cause while on IM treatment and event-free survival (EFS) –events defined as a progression (the same as in PFS, as described above), loss of CCyR, failure to achieve CHR at 6 months, MCyR at 12 months and CCyR at 18 months, or intolerance of IM as the cause its discontinution. The patient survival according to MMoR achievement and the cumulative incidence of MMoR according to different BCR-ABL ratio within the first 3 months of IM therapy was analysed. Kaplan-Meier cumulative incidence methods and log rank test were used for survival statistic analysis. Results. A total of 458 patients (median age 52 year;17-81) treated with IM between 2003–2009 were analysed.The median follow-up was 33.1 months (1.4-82.1). At 2 and 4 years the cumulative incidence of CHR was 90.9% and 94.7%, CCyR 64.9% and 76%, MMR 52.4% and 68.1% and CMR 24.5% and 43%, respectively. In 4 years estimated OS was 91.1%, OSCML 96.6%, TFS 93.9%, PFS 83.2% and EFS 66%. According to ELN 2006 criteria the optimal response (OR) by 6 months (defined as PCyR) and by 12 months (defined as CCyR) resp. had significant impact on PFS (p=0.04 and p 〈 0.001 resp.). The optimal reponse by 3 months (defined as CHR) had significant impact on TFS (p 〈 0.001). According to actualized criteria in ELN 2009, the new definition of optimal response in the 3rd month - at least minor cytogenetic response (mCyR), did not show any prognostic impact on PFS. The achievement of MMoR was correlated with the significant improvement in PFS in the 3rd month (p=0.039) as well as in the 12th month (p 〈 0.049). There was significant improvement in EFS for patients in MMoR in all timepoints (p 〈 0.003, 〈 0.001, 〈 0.001, 〈 0.005). The BCR-ABL ratio lower than 1% within the first 3 months was associated with MMoR achievement in higher number of patients in comparison to patients with higher BCR-ABL levels (p 〈 0.001) Conclusion. The excellent and long-lasting efficacy of imatinib in the treatment of CP-CML in non-selected group of patients treated in the defined region was confirmed. Our results are comparable to those achieved in IRIS trial. Response criteria and their predictive role defined by ELN 2006 and 2009 seems to be helpful at some time points, but the ELN 2009 modification does not seem to represent significant improvement compared to ELN 2006. On the other hand based on the present analysis the earlier incorporation of molecular response into the evaluation scheme may be beneficial. Supported by: CELL-The Czech Leukemia Study Group for Life, Project INFINITY; Project CAMELIA. Disclosures: Faber: BMS, Novartis: Consultancy, Honoraria.

Abstract: Background: Recently we have published results of pilot study on CML patients demonstrating fast development of hyperinsulinaemia, peripheral insulin resistance, hypoadiponectinaemia and hypercholesterolemia during nilotinib therapy. Aims: To analyze results from follow up multicenter study “ENIGMA 2” with the aim to confirm or to exclude results from the pilot study, as well as to analyze whether these abnormalities are detected in control groups of patients treated with other TKIs - imatinib and dasatinib. Methods: Patients received intensive laboratory workup before the start of TKI and after 3 month of therapy. This included fasting insulin, glucose, adiponectin and lipid serum concentration, HbA1c and oral glucose tolerance test. Patients with TKI treatment interruption for 〉 2 weeks and/or dose reduction for 〉 25% were excluded. Results: Between 2/2011-6/2014 in 5 centers 37 CML patients initiated therapy with nilotinib, 18 with imatinib and 8 with dasatinib. After 3 months patients treated with nilotinib developed significant hypersinulinaemia and hyperglycaemia as result of fast development of peripheral insulin resistance. This was proved by significant increase in HOMA-2 index during 3 months of nilotinib therapy (mean – 1.4 vs. 1.8; p = 0.0023). Moreover, we have proved significant decrease of adiponectin (major insulin sensitizer) concentration as well as significant increase in total and LDL cholesterol concentration after 3 month of nilotinib treatment. Details are presented in Table. Contrary – none of these abnormalities were detected in the control group of patients treated with imatinib and dasatinib, including any change in insulin resistance measured by HOMA-2 index (means – 0.9 vs. 1.3; p = 0.1046 and 1.1 vs. 1.1; p = 0.9255). Moreover, administration of imatinib (and probably also dasatinib, however only limited data are available at this moment) leads to increase of adiponectin concentration, which serves as major insulin sensitizer in peripheral tissues. Conclusions: Our study proved fast development of peripheral insulin resistance already during the first 3 months of nilotinib therapy as underlying cause of glucose and secondary also lipid metabolism impairment during this treatment. Moreover, this was not proved for patients treated with imatinib and dasatinb and significant increase in adiponectin concentration during imatinib (and probably dasatinib) therapy could at least partly explain observed amelioration of diabetes 2 during its administration described in some studies Supported by the CELL – the Czech Leukemia Study Group – for life Table. NILOTINIB THERAPY (n=37) Start Month 3 p mean (range) mean (range) Fasting glucose [mmol/l] 5.3 (4.5-6.7) 5.7 (4.6-8.2) 〈 0.0001 Fasting insulin [mU/l] 11.2 (2.4-28.3) 14,1 (2.5-32.7) 0.0037 Fasting C-peptide [pmol/ml] 0.73 (0.53-1.78) 0.76 (0.76-3.31) 0.4953 Fasting HbA1c [mmol/mol] 38.9 (24.0-55.0) 38.2 (25.0-57.0) 0.3900 Fasting adiponectin [mg/l] 16.6 (2.1-45.1) 8.6 (2.6-22.4) 0.0019* Total cholesterol [mmol/l] 4.8 (2.5-6.7) 5.9 (4.4-7.9) 〈 0.0001 LDL cholesterol [mmol/l] 2.8 (1.1-4.9) 3.6 (2.1-5.7) 〈 0.0001 IMATINIB THERAPY (n=18) Start Month 3 p mean (range) mean (range) Fasting glucose [mmol/l] 5.5 (4.4-7.7) 5.6 (4.2-6.4) 0.7567 Fasting insulin [mU/l] 6.7 (2.0-19.0) 9.8 (2.0-37.80) 0.1369 Fasting C-peptide [pmol/ml] 0.77 (0.25-1.55) 0.72 (0.27-1.78) 0.4569 Fasting HbA1c [mmol/mol] 44.8 (33.0-59.0) 41.1 (30.0-55.0) 0.005 Fasting adiponectin [mg/l] 10.8 (2.1-25.7) 26.1 (6.0-45.2) 〈 0.0001** Total cholesterol [mmol/l] 5.1 (3.3-7.1) 4,7 (2.6-7.1) 0.1123 LDL cholesterol [mmol/l] 3.1 (1.7-4.7) 2.7 (1.2-4.7) 0.064 DASATINIB THERAPY (n=8) Start Month 3 p mean (range) mean (range) Fasting glucose [mmol/l] 5.8 (4.6-6.8) 5.3 (3.3-6.7) 0.1764 Fasting insulin [mU/l] 8.1 (2.5-19.3) 8.4 (2.6-17.9) 0.8815 Fasting C-peptide [pmol/ml] 0.63 (0.16-1.11) 0.60 (0.24-1.03) 0.8223 Fasting HbA1c [mmol/mol] 38.8 (31.0-51.0) 37.8 (30.0-56.0) 0.684 Fasting adiponectin [mg/l] 17.3 (9.2-26.7) 12.9 (5.5-21.4) 0.0106*** Total cholesterol [mmol/l] 4.0 (3.0-5.0) 4.5 (3.6-5.8) 0.0831 LDL cholesterol [mmol/l] 2.2 (1.6-3.0) 2.5 (1.9-3.3) 0.1140 *number of paired measurements = 24 **number of paired measurements = 12 ***number of paired measurements = 3 Disclosures Zdenek: Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Klamova:Novartis and Bristol Myers-Squibb: Consultancy, Honoraria. Mayer:Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.