BCR-ABL Transcript Levels Research Articles

How Best to Express the Results of Serial RQ-PCR Studies to Measure Minimal Residual Disease in Treated Leukaemia Patients?.

The use of real time quantitative PCR (RQ-PCR) is now established for monitoring minimal residual disease (MRD) in patients with leukemia responding well to therapy. The level of the target gene is usually expressed as a percentage ratio normalised to the control gene. Measurement of a control gene is needed to exclude the possibility of false negative values due to sample (RNA) deterioration. The ideal control gene should be expressed in blood and/or bone marrow at intermediate level without significant variation between different patients; its RNA should have stability similar to that of the gene of interest; and it should not have a processed pseudogene. For monitoring the low levels of BCR-ABL transcripts characteristic of Ph-positive CML during treatment, different laboratories have quantified as controls (amongst others) ABL, BCR, G6PD, GAPDH,β-actin and β2-microglobulin. Despite the ABL gene being a component of the BCR-ABL fusion gene, it fulfils the criteria for a good control. Moreover as it is expressed at relatively low levels it is sensitive to sample deterioration. Analysis of 10,021 CML blood samples revealed that ABL transcript numbers were consistent when BCR-ABL transcript numbers were less than 20,000 (median 50,200), but above this level ABL quantification was influenced by BCR-ABL copy number (median 110,500). In MRD studies designed specifically to detect small numbers of residual transcripts, the contribution of amplifying BCR-ABL to the control value is not critical to the assessment of tumour load. A contemporaneous comparison of levels of BCR and ABL transcript levels in 831 blood samples taken from patients with CML at various stages of treatment showed a linear relationship (p=0.0001), but the median BCR expression was 0.7 log greater than the median ABL expression. In practice an assay using ABL as control gene for measuring the log reduction in BCR-ABL transcript levels following effective treatment compared with a BCR-ABL baseline value obtained before treatment yields values approximately equivalent to the log reduction obtained with an assay based on BCR as control gene. Nonetheless the variable expression of the commonly used control genes means that log reduction values may differ between centers. Thus we believe that the best method for reporting MRD values in CML patients undergoing treatment is as a percent ratio compared with previous values, i.e. the serial samples post treatment. Log reductions may be a useful ancillary for use within individual centres.

Understanding and Monitoring Chronic Myeloid Leukemia Blast Crisis: How to Better Manage Patients.

Chronic myeloid leukemia (CML) is triggered primarily by the t(9;22) (q34.13; q11.23) translocation. This reciprocal chromosomal translocation leads to the formation of the BCR-ABL fusion gene. Patients in the chronic phase (CP) experience a good curative effect with tyrosine kinase inhibitors. However, cases are treatment refractory, with a dismal prognosis, when the disease has progressed to the accelerated phase (AP) or blast phase (BP). Until now, few reports have provided a comprehensive description of the mechanisms involved at different molecular levels. Indeed, the underlying pathogenesis of CML evolution comprises genetic aberrations, chromosomal translocations (except for the Philadelphia chromosome), telomere biology, and epigenetic anomalies. Herein, we provide knowledge of the biology responsible for blast transformation of CML at several levels, such as genetics, telomere biology, and epigenetic anomalies. Because of the limited treatment options available and poor outcomes, only the therapeutic response is monitored regularly, which involves BCR-ABL transcript level assessment and immunologic surveillance, with the optimal treatment strategy for patients in CP adapted to evaluate disease recurrence or progression. Overall, selecting optimal treatment endpoints to predict survival and successful TFR improves the quality of life of patients. Thus, identifying risk factors and developing risk-adapted therapeutic options may contribute to a better outcome for advanced-phase patients.

Predictive value of tyrosine phosphatase receptor gamma for the response to treatment tyrosine kinase inhibitors in chronic myeloid leukemia patients

Protein tyrosine phosphatase receptor gamma (PTPRG) is a member of the receptor-like family protein tyrosine phosphatases and acts as a tumor suppressor gene in different neoplasms. Recent studies reported the down-regulation of PTPRG expression levels in Chronic Myeloid Leukemia disease (CML). In addition, the BCR-ABL1 transcript level is currently a key predictive biomarker of CML response to treatment with Tyrosine Kinase Inhibitors (TKIs). The aim of this study was to employ flow cytometry to monitor the changes in the expression level of PTPRG in the white blood cells (WBCs) of CML patients at the time of diagnosis and following treatment with TKIs. WBCs from peripheral blood of 21 CML patients were extracted at diagnosis and during follow up along with seven healthy individuals. The PTPRG expression level was determined at protein and mRNA levels by both flow cytometry with monoclonal antibody (TPγ B9-2) and RT-qPCR, and BCR-ABL1 transcript by RT-qPCR, respectively. PTPRG expression was found to be lower in the neutrophils and monocytes of CML patients at time of diagnosis compared to healthy individuals. Treatment with TKIs nilotinib and Imatinib Mesylate restored the expression of PTPRG in the WBCs of CML patients to levels observed in healthy controls. Moreover, restoration levels were greatest in optimal responders and occurred earlier with nilotinib compared to imatinib. Our results support the measurement of PTPRG expression level in the WBCs of CML patients by flow cytometry as a monitoring tool for the response to treatment with TKIs in CML patients.

Assessment of individual molecular response in chronic myeloid leukemia patients with atypical BCR-ABL1 fusion transcripts: recommendations by the EUTOS cooperative network

PurposeApproximately 1–2% of chronic myeloid leukemia (CML) patients harbor atypical BCR-ABL1 transcripts that cannot be monitored by real-time quantitative PCR (RT-qPCR) using standard methodologies. Within the European Treatment and Outcome Study (EUTOS) for CML we established and validated robust RT-qPCR methods for these patients.MethodsBCR-ABL1 transcripts were amplified and sequenced to characterize the underlying fusion. Residual disease monitoring was carried out by RT-qPCR with specific primers and probes using serial dilutions of appropriate BCR-ABL1 and GUSB plasmid DNA calibrators. Results were expressed as log reduction of the BCR-ABL1/GUSB ratio relative to the patient-specific baseline value and evaluated as an individual molecular response (IMR).ResultsIn total, 330 blood samples (2–34 per patient, median 8) from 33 CML patients (19 male, median age 62 years) were analyzed. Patients expressed seven different atypical BCR-ABL1 transcripts (e1a2, n = 6; e6a2, n = 1; e8a2, n = 2; e13a3, n = 4; e14a3, n = 6; e13a3/e14a3, n = 2; e19a2, n = 12). Most patients (61%) responded well to TKI therapy and achieved an IMR of at least one log reduction 3 months after diagnosis. Four patients relapsed with a significant increase of BCR-ABL1/GUSB ratios.ConclusionsCharacterization of atypical BCR-ABL1 transcripts is essential for adequate patient monitoring and to avoid false-negative results. The results cannot be expressed on the International Scale (IS) and thus the common molecular milestones and guidelines for treatment are difficult to apply. We, therefore, suggest reporting IMR levels in these cases as a time-dependent log reduction of BCR-ABL1 transcript levels compared to baseline prior to therapy.

The influence of peripheral blood sample storage and delivery on the quantitative detection result of BCR-ABL (P210) transcript levels

目的探索慢性髓性白血病（CML）患者外周血样本的存储和运输对实时定量PCR（RQ-PCR）检测BCR-ABL（P210）转录本水平的影响。方法采集84例CML患者外周血样本，根据储存时间（0、6、12、24、48和72 h）、温度［室温（18～24 °C）和低温（2～8 °C）］以及振荡条件（振荡时长3、6和12 h）设置不同分组，RQ-PCR法检测不同条件下外周血样本BCR-ABL（P210）转录本水平。本研究将BCR-ABL拷贝数、ABL拷贝数和BCR-ABL（P210）转录本水平等原始数据进行对数转化（log10N）。结果①琼脂糖凝胶电泳结果显示：室温条件下，储存48、72 h的样本RNA出现显著降解；②储存温度方面，总体样本中，室温储存48、72 h的样本BCR-ABL拷贝数检测水平显著低于低温储存的样本（P<0.05）；然而BCR-ABL（P210）转录本水平在低温储存与室温储存条件下检测结果差异无统计学意义（P>0.05）；③储存时间方面，与基线的3.35±1.60相比，总体样本的BCR-ABL拷贝数检测结果仅在室温储存储存下48 h（2.93±1.59）和72 h（2.79±1.42）显著下降（P<0.05）；与基线的5.47±0.35相比，总体样本中ABL拷贝数检测结果在48 h（低温5.29±0.30，室温5.06±0.38）和72 h（低温5.11±0.54，室温4.64±0.79）均显著下降（P<0.05）。但是，与基线的−0.56±1.51相比，无论低温或室温条件下，不同储存时间（6、12、24、48和72 h）的样本BCR-ABL（P210）转录本水平检测结果无显著改变（P>0.05）；④振荡方面，与基线的−0.60±1.37相比，振荡3、6、12 h的样本BCR-ABL（P210）转录本水平检测结果无显著改变（P>0.05）。结论样本储存时间、储存温度及运输振荡因素可以影响BCR-ABL、ABL拷贝数的检测结果，但对BCR-ABL（P210）转录本水平定量检测结果无显著影响。

Real-World Effectiveness of First-Line (1L) Dasatinib Versus 1L Imatinib in Newly Diagnosed Patients with Chronic Phase Chronic Myeloid Leukemia (CP-CML)

Introduction: The safety and efficacy of 1L dasatinib and 1L imatinib was established in the pivotal DASISION and IRIS trials; however, limited real-world evidence exists for the comparative effectiveness of these agents among US patients with CP-CML treated in routine clinical practice. As such, real-world data are needed to assess the outcomes of imatinib- and dasatinib-treated patients in a pragmatic setting. Additionally, recent data suggest that second generation tyrosine kinase inhibitors (TKIs), including dasatinib, may be beneficial in certain CP-CML populations, which may be underrepresented in clinical trials (e.g., high risk, elderly, or high body mass index [BMI]). This study examined the real-world clinical response rates and time to response associated with 1L dasatinib or 1L imatinib among patients with CP-CML, as well as in subgroups defined by Sokal risk, age, and BMI. Methods: A retrospective, observational, US multi-site cohort study was conducted among adults with newly diagnosed Philadelphia chromosome-positive CP-CML treated with 1L dasatinib or 1L imatinib between January 2014 and September 2018. Patients had at least 1 year of follow-up after 1L initiation and did not have another malignancy or treatment as part of any clinical trial for CML. Oncologists collected data from eligible patient charts, including patient characteristics, treatment details, response to dasatinib or imatinib, and survival. Response was classified as major molecular response (MMR) and deep molecular response (DMR: 4.5-log reduction in BCR-ABL1 transcript levels) by physician report. Patient characteristics and outcomes were summarized using descriptive statistics for dasatinib and imatinib; results were reported in aggregate and stratified by Sokal risk (low and intermediate/high), age (&amp;lt; 65 and ≥ 65 years old), and BMI (low/normal [&amp;lt; 25 kg/m2] and high [≥ 25 kg/m2]). Comparisons were made by chi-square or Fisher's exact test for categorical variables, t-test or Wilcoxon test for continuous variables, log-rank test for overall survival (OS), and Cox proportional hazard models using Fine and Gray's method to account for competing risks in estimating differences in time to response across groups. Results: Among the patients treated with 1L dasatinib (n = 309) and 1L imatinib (n = 304), median follow-up time was 27.4 and 28.9 months, respectively. Most patients initiated dasatinib at 100 mg (82%) or imatinib at 400 mg (95%). Dose reductions were more common among dasatinib patients vs imatinib (15% vs 7%, P &amp;lt; 0.01), though fewer dasatinib-treated patients discontinued for any reason (15% vs 28%, P &amp;lt; 0.01). Higher rates of MMR were seen in dasatinib vs imatinib patients (79% vs 65%, P &amp;lt; 0.01) and median time to MMR was shorter with dasatinib vs imatinib (11.9 vs 14.7 months, P &amp;lt; 0.01). Similarly, higher rates of DMR were seen among dasatinib vs imatinib patients (44% vs 25%, P &amp;lt; 0.01) along with a shorter median time to DMR with dasatinib vs imatinib (30.3 vs 66.1 months, P &amp;lt; 0.01). Among patients with intermediate/high Sokal risk, as well as those &amp;lt; 65 years old, rates of MMR and DMR were higher and achieved earlier with dasatinib vs imatinib (all P &amp;lt; 0.01) (Table). Low-risk patients treated with dasatinib had higher rates of DMR vs imatinib (60% vs 32%, P = 0.01). Among patients ≥ 65 years old, rates of MMR and DMR were numerically higher with dasatinib vs imatinib, though differences were not significant at α = 0.05. Across both BMI strata, rates of MMR and DMR were higher with 1L dasatinib vs 1L imatinib (all P &amp;lt; 0.05). In the overall population, dasatinib patients had superior OS compared to those treated with imatinib (98% vs 89%, P &amp;lt; 0.01). Conclusions: In real-world clinical practice, a greater proportion of patients with CP-CML treated with 1L dasatinib achieved MMR and DMR and also achieved these responses earlier vs 1L imatinib. These clinically meaningful improvements were also observed across patient subgroups stratified by Sokal risk, age, and BMI. These findings from real-world US data were consistent with DASISION, demonstrating that dasatinib yields better outcomes among patients with CP-CML, with the novel findings of improved OS and improved outcomes in certain subgroups, including a higher rate of DMR among low-risk patients. Disclosures Klink: Cardinal Health: Current Employment, Current equity holder in publicly-traded company. Keating:Bristol Myers Squibb: Current Employment. Brokars:Bristol Myers Squibb: Current Employment. Kee:Bristol Myers Squibb: Current Employment. Copher:Bristol Myers Squibb: Current Employment. Stwalley:Bristol Myers Squibb: Current Employment, Current equity holder in publicly-traded company. Feinberg:Cardinal Health: Current Employment. Jabbour:Takeda: Other: Advisory role, Research Funding; AbbVie: Other: Advisory role, Research Funding; Genentech: Other: Advisory role, Research Funding; Amgen: Other: Advisory role, Research Funding; Pfizer: Other: Advisory role, Research Funding; Adaptive Biotechnologies: Other: Advisory role, Research Funding; BMS: Other: Advisory role, Research Funding.

Optimal Interval for Detection of Molecular Relapse after Stop of Tyrosine Kinase Inhibitor (TKI) in Philadelphia Chromosome Positive Acute Lymphoblastic Leukemia (Ph+ALL) Caliculated By Kinetics of BCR-ABL Transcripts

Background In Ph+ALL patients, prophylactic/maintenance administrations of TKI are used after the protocol treatment. Unlike Chronic myelogenous leukemia (CML), after TKI stopped, there is no consensus about how often to monitor to detect molecular relapse. In the current study, from clinical data of 31 patients we tried to determine the optimal frequency of MRD monitor for better prognosis using a mathematical model. Methods Doubling time (DT) and Growth rate (GR) were retrospectively calculated by the increase of BCR-ABL from 99 kinetic data from 31 patients with Ph+ALL at molecular relapse. Measurement of amount BCR-ABL was performed by RQ-PCR. Mimicking CML, we defined BCR-ABL/ABL ratio of 0.1% as "MR3 (Major molecular response)" and undetectable levels of BCR-ABL transcript as "MR5 (Complete molecular response)". In order to investigate the relationship between tumor burden (BCR/ABL) at the time of MRD detection and prognosis, it was divided into 3 groups, BCR/ABL&amp;lt;0.1% (MR3), 0.1%&amp;lt;BCR/ABL&amp;lt;1% (MR2) and BCR/ABL&amp;gt;1% (MR1). This study was approved by the institutional review committee. Results The doubling time was 1.3 days (GR 0.7%/day) to 95.4 days (70.8%/day) with a median of 12.3 days (5.8%). The rate of increase was compared by three groups of tumor burden. The DT among patients in MR1 was shorter than those in MR3 and MR2 (7.7 days vs 15.2 days in median, t-test p&amp;lt;0.01). There were no differences of DT in sex, age, treatments and BCR/ABL mutation. Most patient had multiple kinetic data and the smallest amount of BCR/ABL was used in each patient. Among 8 patients who showed MR3 (MR3pt) and 11 who showed MR2 (MR2pt), 14 are alive at this analysis, while among 10 patients who showed MR1 (MR1pt), only 1 patient is alive.(Log-rank test, p&amp;lt;0.1) (Figure) Median survival time is 882 days, 330 days and 16 days in MR3pt, Mr2pt and MR1pt, respectively. All patients died of progression of the disease. Finding molecular relapse before MR2 may related to better results. Optimal interval of MRD detection We set several hypotheses to determine the optimal frequency to detect early recurrence of leukemia. We estimated that patients with MR2 and MR5 have 1010 and 107 Ph+ cells in body, respectively. We defined "MR2" and "MR5" as "optimal intervention threshold" and "detection threshold". From our clinical data, we tentatively determined that doubling time of leukemia growth is distributed between 1 day (GR 100%/day) and 100days (0.7%). Also, we assumed that single cell has a relapse potency and the GR is constant during observation in each patient. The number of Ph+ cells in a MR5 patient who would potentially relapse might be distributed between 1 cell and 1 x 107 (MR5). "Success" was defined as if molecular relapse is detected between M5 and MR2 and "Failure" was defined as if detected more than MR2. According to the daily clinical practice, the optimal examination interval is tentatively every 7 days, every 14 days, every 28 days, every 56 days, every 84 days, every 6 months, and every year. First, in order to calculate the growth rate that would be successful at 7-day intervals, the rate of 168%/day for 1 cell to increase 107 (MR5) in 7 days was calculated. This rate is faster than the maximum rate of 100%/day in this study, so an interval of 7 days is good for the initial period. Similarly, at 14-day intervals, 68%/day is calculated, and in this case, it requires 32 days to increase 107 (MR5) from 1 cell. As a result, after 32.7 days, 14-day intervals are acceptable. Similarly, the calculated results for 28 days, 56 days, 84 days, 6 months, and 1 year are shown in the Table. MRD can be found before M3 (success) with 28-day intervals after 65 days, 56-day intervals after 131 days, 84-day intervals after 196 days, 6-month intervals after 419 days and 1-year intervals after 852 days. Conclusion Taken together, soon after stop of TKI, more frequent monitoring of MRD than in "treatment free remission" in CML is needed. The interval can be prolonged with the passage of time. In several patients, hematopoietic stem cell transplantation (HSCT) was possible due to early intervention by changing TKI and chemotherapy. After HSCT, TKI combined with rapid reduction of immune-suppressants and donor lymphocyte infusion successfully related with long term survival. (data will be shown in ASH) Thus, the tight monitoring according to the mathematical model is important. The current strategy may be applied to other leukemia in which MRD monitoring by PCR is established. Disclosures Miyamura: Bristol-Myers Squibb Co., Ltd.:Honoraria;Celgene Co., Ltd.:Honoraria;Daiichi-Sankyo Co., Ltd.:Honoraria;Otsuka Co., Ltd.:Honoraria;Pfizer Co., Ltd.:Honoraria;Novartis Co., Ltd.:Honoraria.Goto:Takeda Pharmaceutical Co., Ltd:Honoraria;Novartis Pharma Co., Ltd.:Honoraria.Morishita:Bristol-Myers Squibb Co., Ltd.:Honoraria.Ozawa:Novartis Co., Ltd.:Honoraria.

Retro-Prospective Observational Study on the Risk of Progression in Chronic Phase-Chronic Myeloid Leukemia (CML) Patients Eligible for Tyrosine Kinase Inhibitor Discontinuation (TFR-PRO)

Retro-Prospective Observational Study on the Risk of Progression in Chronic Phase-Chronic Myeloid Leukemia (CML) Patients Eligible for Tyrosine Kinase Inhibitor Discontinuation (TFR-PRO)

BCR-ABL1 Transcript Doubling Time after Imatinib Discontinuation for Treatment-Free Remission in Chronic Myeloid Leukemia in Chronic Phase: Predictor for Treatment-Free Remission Failure

BCR-ABL1 Transcript Doubling Time after Imatinib Discontinuation for Treatment-Free Remission in Chronic Myeloid Leukemia in Chronic Phase: Predictor for Treatment-Free Remission Failure

Dasatinib treatment long-term results among imatinib-resistant/intolerant patients with chronic phase chronic myeloid leukemia are favorable in daily clinical practice

To evaluate long-term real-life results of dasatinib therapy among chronic phase chronic myeloid leukemia patients resistant or intolerant to imatinib, we retrospectively analyzed data of 118 patients treated in centers participating in the database INFINITY. With median follow-up of 37 months, estimated 5-year cumulative incidences of complete cytogenetic and major molecular responses were 78% and 68%, respectively. The estimated 5-year probability of overall survival (OS) and event-free survival (EFS) were 86% and 83%, respectively. Both OS and EFS were significantly improved among patients with BCR-ABL1 transcript level ≤10% at 3 months. Dasatinib toxicity was tolerable however persistent in almost half our patients, even after years of therapy. Pleural effusion occurred in 29% of patients and was responsible for 30% of dasatinib discontinuations. Our results confirmed very good efficacy and acceptable toxicity of dasatinib in second line setting and support the evidence and importance of high-quality real-life CML patient management.

Efficacy and safety profile of generic imatinib in patients with newly diagnosed chronic myeloid leukemia-chronic phase: sharing experience of a hemato-oncology center from eastern India.

In India, CML is the commonest adult leukemia. Imatinib is the gold standard for frontline treatment of newly diagnosed CML-CP patients. The present study was conducted to assess the efficacy and safety of generic imatinib in newly diagnosed CML-CP patients. In this prospective study, 76 newly diagnosed CML-CP patients received generic imatinib. They were monitored as per the ELN2013 recommendation. Karyotyping and BCR-ABL transcript level were done at specified time points. Adverse effects, if any, were documented as per the NCI-CTCAE criteria v4.03. Statistical analysis was done using standard methods. A total of 76 patients included in the study; median age was 36years. The most common (71%) presenting symptom was fatigue; splenomegaly was found in all patients. CHR was achieved in 97% cases. At 3months, 64.5% patients achieved ERM. At 6months, CCyR and MCyR had seen in 65% and 68% cases, respectively. MMR achieved at 12months in 44% cases. Most common hematological and non-hematological toxicity were anemia and skin changes seen in 89.5% and 71% cases, respectively. With generic imatinib therapy, the results of treatment outcome and safety profile were comparable with original imatinib. The added advantage was gross reduction in cost of therapy meeting unmet needs in CML patients in countries with resource constraints.

Treatment Outcomes in Chronic Myeloid Leukemia: Does One Size Fit All?

With the success of tyrosine kinase inhibitors (TKIs) in achieving next-to-normal overall survival in chronic myeloid leukemia (CML), treatment-free remission (TFR) has become a significant goal in the management of this disease. Discontinuation of therapy is attractive to both patients and physicians because maintaining a stable BCR-ABL transcript level without therapy would imply true operational CML cure. With TFR, patients are not exposed to unknown long-term adverse effects of TKIs and common adverse effects that may affect quality of life. Several factors need to be considered before attempting TFR, because this goal is not appropriate for a significant proportion of patients with CML. Patient-related factors, CML response to therapy and its duration, monitoring capacity, patient preferences and compliance with monitoring, and economic factors influence the decision to attempt to discontinue TKIs. Unfortunately, only 50% of patients are appropriate candidates for discontinuation of treatment. Of those, another 50% maintain stable disease while off TKIs. This means that merely 25% of patients achieve TFR. Further optimization and research are required to be able to extend this treatment goal to a larger population of patients. Although TFR is attractive and desirable, this goal is not a one-size-fits-all approach, and we should continue to focus on patients with CML having a normal OS with the best quality of life possible.

Frequency of coexistence and kinetics of the BCR-ABL1 transcript level and allele burden of JAK2V617F and CALR Type 1, 2 gene mutations in patients with chronic myeloid leukemia

Introduction. The pathogenesis of myeloproliferative neoplasms is associated with the chimeric gene BCR-ABL1 or with one of the driver mutations in the genes JAK2, MPL and CALR (Calreticulin). However, the classifi cation of the World Health Organization lists no myeloid neoplasms with more than one driver genetic abnormality. Aim. To search for mutations in the genes JAK2, MPL and CALR in patients with BCR-ABL1-positive chronic myeloid leukemia (CML), as well as to evaluate the kinetics of the discovered mutations during tyrosine kinase inhibitor (TKI) therapy. Materials and methods. mRNA and DNA samples isolated from blood and bone marrow cells of 567 CML patients, who underwent periodic monitoring of the BCR-ABL1 transcript level over the 2012–2019 period were included in the study The BCR-ABL1 transcript level was determined using a highly sensitive quantitative real-time polymerase chain reaction. The mutations JAK2V617F and MPLW515L/K were detected using real-time quantitative allele-specifi c polymerase chain reaction. Mutations in the CALR gene were investigated using fragment analysis followed by Sanger sequencing. Results. The combination of the BCR-ABL1, JAK2 and CALR gene mutations among CML patients receiving TKIs was 1.23 % (7/567). Out of these, the combination of BCR-ABL1 with JAK2V617F and the combination of BCR-ABL1 with CALR gene mutations were detected in 0.88 % (5/567) and 0.35 % (2/567) of cases, respectively. During TKI therapy, in 5 out of 7 patients, the level of BCR-ABL1 reached major molecular response (MR). In 4 of these patients, the therapy was discontinued. These patients are currently in molecular remission. In the remaining 2 patients, major MR was not achieved, despite the use of second-generation TKI preparations. Conclusions. The combination of the BCR-ABL1 chimeric gene with gene mutations Jak2 or CALR was a rare event and amounted to 0.88 and 0.35 % of cases, respectively. The combination of BCR-ABL1 with Jak2V617F and CALR mutations does not always impede the achievement of major MR.

Why is it critical to achieve a deep molecular response in chronic myeloid leukemia?

The primary goal of tyrosine kinase inhibitor (TKI) therapy for patients with chronic myeloid leukemia is survival, which is achieved by the vast majority of patients. The initial response to therapy provides a sensitive measure of future clinical outcome. Measurement of BCR-ABL1 transcript levels using real-time quantitative polymerase chain reaction standardized to the international reporting scale is now the principal recommended monitoring strategy. The method is used to assess early milestone responses and provides a guide for therapeutic intervention. When patients successfully traverse the critical first 12 months of TKI therapy, most will head towards another milestone response, deep molecular response (DMR, BCR-ABL1 ≤0.01%). DMR is essential for patients aiming to achieve treatment-free remission and a prerequisite for a trial of TKI discontinuation. The success of discontinuation trials has led to new treatment strategies in order for more patients to reach this milestone response. DMR has been incorporated into endpoints of clinical trials and is considered by some expert groups as the optimal treatment response. But is DMR a stable response and does it provide the ultimate protection against TKI resistance and death? Do we need to increase the sensitivity of detection of BCR-ABL1 to better identify the patients who would likely remain in treatment-free remission after TKI discontinuation? Is it necessary to switch current TKI therapy to a more potent inhibitor if the goal is to achieve DMR? These are issues that I will explore in this review.

CML-143: BCR-ABL1 Translocation Combined with JAK2V617F or CALRtype-1,2 Mutations in Russian CML Patients Undergoing TKI Therapy: Transcript Level and Mutation Allele Burden

Background Frequency of BCR-ABL1 translocation and JAK2V617F or CALRtype-1,2 mutation co-occurrence in chronic myeloid leukemia (CML) patients varies in different populations. According to Soderquist et al., it amounts to 0.4% of cases in USA; Martin-Cabrera et al. – 0.2% in Germany; Lewandowski et al. – 0.7% in Poland. Combination of BCR-ABL1 translocation with CALRtype-1,2 mutations in CML patients during tyrosine kinase inhibitor (TKI) therapy has not been reported yet. Prognostic value of the BCR-ABL1 transcript level kinetics and of JAK2V617F or CALRtype-1,2 mutations allele burden (AB) in Russian CML patients undergoing TKI therapy has not been assessed so far. Aims To evaluate frequency of coexistence and kinetics of the BCR-ABL1 transcript level and AB of JAK2V617Fand CALRtype-1,2 mutations in CML patients undergoing TKI therapy. Materials and Methods mRNA and DNA samples isolated from blood and bone marrow cells of 683 CML patients, who underwent periodic monitoring of the BCR-ABL1 transcript level over the 2012–2020 period were included in the study. The BCR-ABL1 transcript level and AB of JAK2V617F mutation were determined using a highly sensitive (Log-5) quantitative real-time polymerase chain reaction. CALRtype-1,2 mutations were investigated using fragment analysis followed by Sanger sequencing. Results The combination of the BCR-ABL1, JAK2V617F, and CALRtype-1,2 mutations among CML patients receiving TKIs occurred in 8 of 683 cases (1.17%). Out of these, the combination of BCR-ABL1 with JAK2V617F, and the combination of BCR-ABL1 with CALRtype-1,2 mutations were detected in 0.88% (6/683) and 0.29% (2/683) of cases, respectively. During TKI therapy, in 6 out of 8 cases, the level of BCR-ABL1 reached major molecular response (MR). In 4 of these cases, the therapy was discontinued. These patients are currently in molecular remission. In the remaining 2 patients, major MR was not achieved, despite the use of second generation TKIs. Conclusions The combination of the BCR-ABL1 translocation with JAK2V617F or CALRtype-1,2 mutations is a rare event in our cohort of patients and occurred in 0.88 and 0.29% of cases, respectively. The combination of the BCR-ABL1, JAK2V617F, and CALRtype-1,2 mutations may not interfere with the achievement of major MR under TKI treatment.

Abstract 4682: Influence of PI3K/AKT pathway on imatinib mesylate treatment outcome in chronic myeloid leukemia patients

Abstract Chronic myeloid leukemia (CML) is a common myeloproliferative disorder characterized by cytogenetic abnormality [t(9;22)(q34;q11)] that generates BCR-ABL oncogene with aberrant tyrosine kinase activity, the driver event in CML origin. Tyrosine kinase inhibitors (TKIs) are remarkably effective; yet, treatment failure is common in some cases due to the accumulation of mutations in BCR-ABL itself and other genes causing drug resistance/relapse, which indicates that BCR-ABL inhibition alone may not be sufficient to combat CML. The PI3K/Akt/mTOR signaling pathway downstream of BCR-ABL has been proven to be an important survival mechanism in leukemias. In vitro studies demonstrated that targeting this pathway could be a viable strategy, but needs further validation in CML patients. In this study, we examined the critical PI3K/AKT/mTOR pathway genes (PIK3CA, PTEN, AKT1, SHIP1, mTOR, and FOXO3A) in CML patients (n=51) using qPCR method at diagnosis and after treatment, and analyzed with respect to BCR-ABL status, and JAK2, STAT5, and STAT3 levels. Interestingly, significant upregulation of AKT1 (p=0.012) and PIK3CA (p=0.026) and downregulation of PTEN (P=0.06) and SHIP1 (p=0.039) was observed in samples at diagnosis compared to their post imatinib treated. Remarkably, these elevated AKT1 and PI3KCA transcript levels were significantly associated with increased BCR-ABL and JAK2 transcript levels, but not STAT3 and STAT5 suggesting PI3K pathway as a prominent target in CML. However, with respect to the clinical phase and imatinib response, none of the genes showed significant differences except for PTEN, which was significantly downregulated in advanced phase (p&amp;lt;0.042) and in cases with poor imatinib response. Overall, these results indicate a critical role for PI3K pathway in CML and its maintenance. Citation Format: Swathi Banapuram, Manjula Gorre, Raghunadha Rao Digumarti, Vishnupriya Satti, Komaraiah Palle, Sandhya Annamaneni. Influence of PI3K/AKT pathway on imatinib mesylate treatment outcome in chronic myeloid leukemia patients [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4682.

Therapeutic Challenges in Chronic Myeloid Leukemia: A Case-Based Discussion

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by a reciprocal translocation between the long arms of chromosomes 9 and 22 that results in expression of the oncoprotein BCR-ABL1. An optimal response to tyrosine kinase inhibitors (TKIs) requires a BCR-ABL transcript level ≤ 10% at 3 months, ≤ 1% at 6 months, ≤ 0.1% at 1 year, and ≤ 0.01% onwards. Complex scenarios like P190 BCR-ABL CML, unusual BCR-ABL transcripts, primary refractory CML, and detection of TKI-resistance mutations during treatment frequently pose a therapeutic challenge. In this article we present some of these clinical scenarios using a case-based approach. J Med Cases. 2020;11(7):215-220 doi: https://doi.org/10.14740/jmc3510

A novel HDAC inhibitor chidamide combined with imatinib synergistically targets tyrosine kinase inhibitor resistant chronic myeloid leukemia cells

Chidamide is a novel selective histone deacetylase inhibitor (HDACi) with promising activity in hematological malignancies, but its role in chronic myeloid leukemia (CML) was marginally addressed. In this study, we firstly demonstrated that chidamide alone inhibited CML cells proliferation, induced apoptosis and cell cycle arrest. Further, chidamide combined with imatinib (IM) induced synergistic lethality in CML cell line KBM5, as well as IM-resistant CML cells KBM5T315I, associated with a marked reduction of Bcr-Abl kinase activity and acetyl-histone H3 expression. The combination treatment markedly inhibited constitutive activity of β-catenin signaling in IM-resistant cells and abolished the protective effects of mesenchymal stromal cells (MSCs) to CML cells. In addition, the co-treatment significantly reduced Bcr-Abl and β-catenin transcript levels and induced apoptosis of primary CD34+ stem/progenitor cells derived from blast crisis (BC)-CML patients, but exhibited minimal toxicity to normal CD34+ progenitors. Collectively, our data show that combination of chidamide and imatinib synergistically targets tyrosine kinase inhibitor (TKI) -resistant BC-CML cells via inhibition of Bcr-Abl and β-catenin signaling, suggesting that this combination has the potential for treating TKI-resistant CML and improving clinical outcomes of BC-CML patients.

BCR-ABL1 and beyond

Chronic myeloid leukaemia (CML) is characterised by the BCR-ABL1 fusion, which causes activated and abnormal cell signalling. If untreated, CML progresses to a rapidly fatal acute leukaemia at a median of 3 years. BCR-ABL1 can be superbly targeted by tyrosine kinase inhibitor drugs and most patients now have a life expectancy approaching that of the general population. However, about 20% of patients fail therapy and require a rapid change of treatment to avoid the risk of disease progression and death. Molecular monitoring of BCR-ABL1 transcript levels using quantitative PCR is now the recommended monitoring strategy and can detect treatment failure and emerging drug resistance. Acquired resistance is most frequently associated with mutations in the BCR-ABL1 kinase domain that interfere with drug binding. These are detected in ∼50% of resistant patients, but the other resistance mechanisms are not well understood. Data is emerging from next-generation sequencing studies that somatic variants in cancer-related genes occur at a high frequency at drug resistance. Furthermore, these mutations have also been detected in some patients at diagnosis and are associated with a poor outcome. Next-generation sequencing may provide important prognostic information for CML patients at diagnosis and resistance and identify targets for therapy.

BCR-ABL1 transcript decline ratio combined BCR-ABL1IS as a precise predictor for imatinib response and outcome in the patients with chronic myeloid leukemia.

Purpose: The early BCR-ABL1 reduction had the prognostic impact of the chronic-phase chronic myeloid leukemia (CML-CP) patients. This study was to find a more precise early prognosis index at 3 months in the patients with newly diagnosed CML-CP, especially for the patients with BCR-ABL1IS >10%.Methods: We retrospectively analyzed the data of 79 newly diagnosed CML-CP patients from October 2013 to April 2017. All patients took imatinib regularly and continuously and monitored BCR-ABL1 transcript level at baseline and 3, 6, 9, 12, 18 months after starting imatinib treatment.Results: Among the 44(55.7%) patients with BCR/ABL1IS ≤10% at 3 months after imatinib treatment, 12(27.3%) cases did not achieve major molecular response (MMR) at 12 months, and 7(14.9%) patients with the halving time BCR-ABL1 transcript ≤40 days failed to achieve MMR at 12 months. However, approximately twenty-six percent of the patients with BCR-ABL1IS >10% still obtained MMR. Moreover, the patients with BCR-ABL1IS ≤10% and halving time ≤40 days had a significantly better MMR than that of the patients with the BCR-ABL1IS ≤10% and halving time >40 days (88.6% versus 11.1%, P <0.001). However, the patients with the BCR-ABL1IS >10% and halving time >40 days rarely achieved MMR at 12 months.Conclusion: These data indicated that the halving time of BCR-ABL1 transcript was also an important prognostic factor as that of the BCR-ABL1IS. Combined observations of these two prognosis indexes are more accurate predictor for the long-term molecular response, especially for the CML-CP patients with BCR-ABL1IS >10%, and which is helpful for TKI switching as early as possible to improve patients' survival and reduce drug costs.