Remission In Chronic Myeloid Leukemia Research Articles

Defining therapy goals for major molecular remission in chronic myeloid leukemia: results of the randomized CML Study IV

Major molecular remission (MMR) is an important therapy goal in chronic myeloid leukemia (CML). So far, MMR is not a failure criterion according to ELN management recommendation leading to uncertainties when to change therapy in CML patients not reaching MMR after 12 months. At monthly landmarks, for different molecular remission status Hazard ratios (HR) were estimated for patients registered to CML study IV who were divided in a learning and a validation sample. The minimum HR for MMR was found at 2.5 years with 0.28 (compared to patients without remission). In the validation sample, a significant advantage for progression-free survival (PFS) for patients in MMR could be detected (p-value 0.007). The optimal time to predict PFS in patients with MMR could be validated in an independent sample at 2.5 years. With our model we provide a suggestion when to define lack of MMR as therapy failure and thus treatment change should be considered. The optimal response time for 1% BCR-ABL at about 12–15 months was confirmed and for deep molecular remission no specific time point was detected. Nevertheless, it was demonstrated that the earlier the MMR is achieved the higher is the chance to attain deep molecular response later.

Imatinib-mesylate enhances the maintenance of chronic myeloid leukemia stem cell potential in the absence of glucose

The introduction of BCR/Abl tyrosine kinase inhibitors (TKI), such as imatinib-mesylate (IM), has revolutioned the treatment of chronic myeloid leukemia (CML). However, although extremely effective in inducing CML remission, IM is unable to eliminate leukemia stem cells (LSC). This is largely due to the suppression of BCR/Abl protein, driven by the reduction of energy supply due to oxygen or glucose shortage, in stem cell niches of bone marrow. Here, we investigated whether, in K562 and KCL22 CML cell cultures, glucose shortage induces refractoriness of stem cell potential to IM. In the absence of glucose, IM, while maintaining its detrimental effect on CML cell bulk, actually enhanced colony formation ability and stem cell potential. This was paralleled by an increased expression of the Nanog and Sox-2 stem cell markers. These evidences stress further the importance of developing strategies alternative to TKI capable to target LSC of CML.

Treatment-free remission in CML: who, how, and why?

Chronic myeloid leukemia (CML) is the best example of successful targeted therapy. Today, the overall survival of patients with CML treated by using tyrosine kinase inhibitors (TKIs) is very close to that of the healthy population. The current question is: how can we further ameliorate the clinical outcome of patients with CML? Clinical trials have shown that some patients with CML in the chronic phase who achieve sustained deep molecular responses on TKI therapy can safely suspend therapy with no evidence of relapse. The long follow-up studies and the number of eligible patients have now validated the concept of treatment-free remission (ie, the ability to maintain a molecular response after stopping therapy). It should be considered as the future criterion to evaluate the success of clinical trials, especially if we want to take into account the quality of life of patients in addition to the economic aspect. Because post-TKI discontinuation follow-ups have been increasing over time with no evidence of relapse in some patients, the next step for the coming decade will be to address the topic of CML cure.

1031P - The EUROSKI biomarker study: Analyzing the mechanisms of treatment-free remission in chronic myeloid leukemia

Background: A substantial proportion of chronic myeloid leukemia (CML) patients in deep molecular response (DMR) reach treatment-free remission (TFR) after tyrosine kinase inhibitors (TKI) cessation. The aim of this study is to identify a gene signature predictive for TFR using whole transcriptome expression analyses. Methods: RNA from peripheral blood (PB) leukocytes of 60 CML patients who stopped TKI therapy within the EUROSKI study and 10 healthy controls were isolated. CML patients were divided into two groups of whom n = 30 patients had ongoing TFR, while 30 patients encountered molecular recurrence. RNA was isolated at the last day of TKI intake. In order to investigate differentially expressed genes, whole transcriptome arrays (Clariom D, Affymetrix) were analyzed. Candidate biomarkers were tested in multivariate analyses and gene set enrichment analyses (GSEA). Results: CML patients in DMR compared to healthy controls showed 16000 differentially expressed genes (p < 0.05). The natural killer cell marker CD69 showed overexpression with highest fold change (> 8-fold) for CML patients versus healthy controls. Significant enrichment of NFκB mediated TNFα and TGFβ pathways (FDR<7%, p < 0.03) were found in CML patients. Comparing the CML TFR versus relapse cohort, we found 2600 differentially expressed genes. Most notably the toll-like receptors TLR1, TLR6 and TLR8 were upregulated in the relapse cohort (p < 0.03). Activated downstream signatures of NOD-like, TLR and TNFα pathways, known for their promotion of a protective CML microenvironment, were significantly enriched (p < 0.03, FDR<2%). In contrast, patients in TFR were characterized by an upregulation of T-cell receptor and granzyme gene family members (p < 0.03). Genes of interest showed distinct cut-offs predictive for TFR over a period of 12 months. Conclusions: CML patients in DMR present a considerable inflammatory gene expression pattern in PB leukocytes in contrast to healthy controls. Alike previous studies, genes involved in immune exhaustion and immune surveillance were differentially expressed between patients with TFR and relapse. The specific inflammatory gene signature of the relapse cohort suggests ‘stemness’ as third mechanism and driver for relapse. Legal entity responsible for the study: University Heidelberg Funding: ELN Foundation Disclosure: R. Sébastien: Novartis research fund. S. Saussele: Advisory board: Novartis, Bristol-Myers Squib, Pfizer and ARIAD Fees: Novartis, Bristol-Myers Squib, Pfizer and ARIAD Research grant: Novartis and Bristol-Myers Squib Travel grant: Novartis and Bristol-Myers Squib. All other authors have declared no conflicts of interest.

Treatment-free remission in chronic myeloid leukemia: floating between expectation and evidence.

Treatment-free remission in chronic myeloid leukemia: floating between expectation and evidence

Enhanced Natural Killer and Cytotoxic T Lymphocyte Responses, with Decreased Monocytic Myeloid Derived Suppressor Cells May Promote Treatment Free Remission in Chronic Myeloid Leukaemia Patients Following Tyrosine Kinase Inhibitor Cessation

Introduction:An attempt at tyrosine kinase inhibitor (TKI) withdrawal in deep molecular remission leads either to treatment free remission (TFR) or early molecular relapse (MolR) in chronic myeloid leukaemia (CML) patients. We hypothesise that immune responses promote sustained TFR and immunological markers may predict response following TFR attempt.Methodology: We studied 54 CML patients (from ALLG trials CML 8, median follow-up 66 mo, and CML 10, median follow-up 24 mo) at baseline on TKI (minimum 24 mo MR4.5) and 3 mo and 6 mo following TKI discontinuation. MolR was defined as any single sample on follow-up with BCR-ABL1 >0.1% or two consecutive BCR-ABL1 positive samples at any value. Effector immune responses of CD56dim natural killer (NK) cells and NK cell receptor repertoire were characterised by flow cytometry and cytotoxic T lymphocyte (CTL) responses to leukaemia-associated-antigens (LAAs) WT1, BMI-1, PR3 and PRAME by interferon-gamma ELISPOT. Immune suppressor regulatory T cells (Treg; CD4+CD25brightCD127-FoxP3+), Granulocytic and Monocytic Myeloid-Derived Suppressor Cells (MDSCs; HLA-DR-Lin-CD11b+CD33+CD66b+CD15+ and HLA-DR-Lin-CD11b+CD33+CD66b-CD14+, respectively), Programmed cell death-1 (PD-1) expression on T cells, NK cells, B cells and Monocytes, and major B cell subsets were characterized by flow cytometry.Results: TFR patients displayed increased CD3-CD56dimCD16bright cytolytic NK cells as a proportion of total lymphocytes at baseline (n=23, 27.1% ± 2.9) vs MolR (n=23, 19.1% ± 2.0, p=0.02). TFR patients displayed a more mature CD56dim CD57+ NK cell phenotype at baseline (74.5% ± 2.2 of total NK cells) vs MolR (66.3% ± 2.7, p=0.04). Extensive characterisation of NK cell receptor repertoire revealed NKG2D activating receptor expression was increased in TFR patients (baseline= 56.8% ± 3.8, 3 mo= 61.4% ± 5.0, 6 mo= 49.9% ± 5.8) vs MolR (baseline= 44.2% ± 3.7, 3 mo= 42.2% ± 5.5, 6 mo= 22.0% ± 8.3, all p=0.02). KIR2DL2/DL3/DS2-positive NK cells were increased in MolR patients at 3 and 6 mo vs TFR. (MolR; 3 mo= 44.8% ± 4.6, 6 mo= 48.8% ± 4.9. TFR; 3 mo= 31.5% ± 4.0 p=0.05, 6 mo= 31.1% ± 2.1, p=0.001).No significant differences were observed in CD56brightCD16-/dim immunoregulatory NK cells, C-type lectin receptor expression (CD94/NKG2A/NKG2C, CD161, CD69), Natural cytotoxicity receptors (NKp30, NKp44, NKp46), CD62L (on T cells and NK cells) and KIR2DL5 expression. No difference in NK Cell-mediated K562 degranulation as a surrogate marker of NK cell function was observed between TFR and MolR patients.Functional CTL immune responses were observed in TFR and MolR patients. BMI-1 CTL responses were increased at baseline in TFR (23%) vs MolR (9%). PR3 CTL responses were not detected in TFR at baseline, 3 mo or 6 mo (0%) vs MolR (baseline= 18%, 3 mo= 50%, 6 mo= 50%). No difference was observed in WT1 or PRAME CTLs.Quantification of immune suppressor cell types revealed decreased Monocytic MDSCs in TFR patients at baseline (10.0% ± 2.3) vs MolR (17.7% ± 3.1, p=0.02). There was no difference in granulocytic MDSCs or Treg between TFR and MolR. No difference in PD-1 expression was observed on NK cells, T cells, B cells and Monocytes. Extensive characterisation of B cell subsets revealed no difference in TFR vs MolR (Table 1).Conclusion: In keeping with STIM and EURO-SKI trials, a threshold level of particular NK cell subsets may be important in maintaining TFR. We found additionally that enhanced NK and CTL effector responses and decreased inhibitory NK KIR2DL2/DL3/DS2 expression, in combination with reduced monocytic MDSC may promote sustained TFR. Methods to enhance nett immune effector responses, such as mature CD56dimCD57+ NK cells and BMI-1 CTL responses or targeting inhibitory KIR may increase TFR success rates. [Display omitted] DisclosuresWhite:Ariad: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Ross:Novartis Pharmaceuticals: Honoraria, Research Funding; BMS: Honoraria. Hughes:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Honoraria. Yong:Celgene: Research Funding; BMS: Honoraria, Research Funding; Novartis: Honoraria, Research Funding.

Two-Year Consolidation By Nilotinib Is Associated with Successful Treatment Free Remission in Chronic Myeloid Leukemia with MR4.5: Subgroup Analysis from STAT2 Trial in Japan

▪Background Nilotinib (NIL) is a second-generation tyrosine kinase inhibitor (TKI) that exhibits significant efficacy as first- or second-line treatment in patients with chronic myeloid leukemia (CML). Superior rates of deeper molecular responses (DMR) were achieved with NIL vs. imatinib (IM) in patients newly diagnosed with CML in chronic phase (CML-CP) in the ENESTnd trial. In addition, the ENESTcmr study demonstrated that switching to NIL after a minimum of 2 years on IM led to increased rates of DMR vs. remaining on IM. Switching to NIL treatment for 2 years safely led to MR4,5 (BCR-ABLIS…0.0032%) in 47.5% of patients with major molecular response (MMR) on long-term IM therapy in our STAT1 trial. Recently, treatment free remission (TFR) was proposed as one of the goals in CML treatment. Indeed, prospective trials suggest that IM therapy may be safely and successfully discontinued in 40% of CML patients with MR4.5. STAT2 is the first study to evaluate the efficacy of two-year consolidation by NIL for successful TFR in patients with CML-CP who had achieved MR4.5. Before enrolling in STAT2, some patients were treated by not only IM but also NIL because of MMR but no MR4.5 after IM therapy, and some patients changed over from STAT1 to STAT2. Here, we present the results of the subgroup analysis from STAT2 based on the prior treatments at the time of entry into the study.Methods In the STAT2 trial, patients who achieved MR4.5 on IM front line therapy (subgroup 1; SG1) or NIL second line therapy after IM therapy (subgroup 2; SG2) were eligible and NIL was given twice daily at the dose of 600 mg/day for 2 years in consolidation phase. The primary endpoint of STAT2 was the proportion of patients with successful TFR, defined as no confirmed loss of MR4.5 (2 consecutive IS RQ-PCR tests), within the first 12 months of TFR phase. Thirty-five institutions in STAT study group participated. The study was conducted in accordance with the principles of the Declaration of Helsinki. Informed consent was signed by all patients according to institutional guidelines. The study was approved by all institutional review boards and registered with UMIN-CTR (000005904).Results Between July 2011 and December 2012, 96 patients were enrolled in STAT2. Among 96 patients, 50 patients were treated by IM first line only as prior therapy (SG1). On the other hand, 40 patients were treated by IM first line and NIL second line including 21 patients who changed over from STAT1 to STAT2 because they achieved MR4.5 (SG2). Six patients were excluded in this analysis because second generation TKIs were taken as a first line therapy. Among patients treated by NIL for 2 years in this study, 40/50 (80%; 95% CI, 68.4%-88.7%) in SG1 and 33/40 (82.5%; 95% CI, 69.6%-91.5%) in SG2 entered the TFR phase, respectively. The median age was 54.5 years in SG1 and 56.0 years in SG2. The ratio of men to women was 26:14 in SG1 and 18:15 in SG2. The total duration of TKI treatment was 110 months for the SG1 with a median of 86 months of IM, and 24 months of NIL, and 93 months in SG2 with a median of 62 months of IM, and 31 months of NIL, respectively. All patients achieved MR4.5 at the time of entry into the study and the median time to MR4.5 was 47 months in SG1 and 60 months in SG2.The proportion of patients who maintained TFR at 12 months after stopping NIL was similar across the 2 subgroups: 25/40 (62.5%; 95% CI, 48.3%-77.3%) in SG1, and 23/33 (69.7%; 95% CI, 54.0%-82.5%) in SG2. The Kaplan-Meier (KM) analysis of TFR survival showed that in the 2 subgroups, the majority of events occurred within the first 6 months after stopping NIL (Figure 1). There were no significant differences between these 2 subgroups.Conclusion After two-year consolidation by NIL of CML-CP patients who achieved MR4.5, the TFR rate was 67.9% (90%CI: 58.2% to 76.6%) at 12 months in the STAT2 trial. In the present analysis looking at the prior TKI exposure, the TFR rate was similar in patients treated with IM first line only or who switched from IM to NIL before entering the study, despite the fact that the treatment duration of switched patients was slightly shorter. These findings suggest that two-year consolidation by NIL is associated with successful TFR in CML with MR4.5 that was achieved with IM alone or after switching to NIL. [Display omitted] DisclosuresTakahashi:PFIZER: Honoraria, Research Funding; BMS: Honoraria; NOVARTIS PHARMA: Honoraria, Research Funding. Nakaseko:BMS: Honoraria, Research Funding; PFIZER: Honoraria, Research Funding; NOVARTIS: Honoraria. Nishiwaki:Novartis PHARMA: Research Funding.

Deep molecular responses for treatment-free remission in chronic myeloid leukemia.

Several clinical trials have demonstrated that some patients with chronic myeloid leukemia in chronic phase (CML‐CP) who achieve sustained deep molecular responses on tyrosine kinase inhibitor (TKI) therapy can safely suspend therapy and attempt treatment‐free remission (TFR). Many TFR studies to date have enrolled imatinib‐treated patients; however, the feasibility of TFR following nilotinib or dasatinib has also been demonstrated. In this review, we discuss available data from TFR trials and what these data reveal about the molecular biology of TFR. With an increasing number of ongoing TFR clinical trials, TFR may become an achievable goal for patients with CML‐CP.

The concept of treatment-free remission in chronic myeloid leukemia.

The advent of tyrosine kinase inhibitors (TKI) into the management of patients with chronic myeloid leukemia (CML) has profoundly improved prognosis. Survival of responders is approaching that of the general population but lifelong treatment is still recommended. In several trials, TKI treatment has been stopped successfully in approximately half of the patients with deep molecular response. This has prompted the development of a new concept in the evaluation of CML patients known as ‘treatment-free remission'. The future in CML treatment will be to define criteria for the safe and most promising discontinuation of TKI on one hand, and, on the other, to increase the number of patients available for such an attempt. Until safe criteria have been defined, discontinuation of therapy is still experimental and should be restricted to clinical trials or registries. This review will provide an overview of current knowledge as well as an outlook on future challenges.

Killer immunoglobulin-like receptors can predict TKI treatment-free remission in chronic myeloid leukemia patients

Several factors are predictive of treatment-free remission (TFR) in chronic myeloid leukemia (CML), but few data exist on the role of natural killer (NK) cells and their killer-cell immunoglobulin-like receptors (KIRs). KIR and human leukocyte antigen (HLA) genotypes were investigated in 36 CML patients who discontinued tyrosine kinase inhibitor (TKI) treatment after achieving deep molecular response (MR(4.5)). Cumulative TFR was significantly higher in patients homozygous for KIR A haplotype (85.7% vs. 45.5%; p = 0.029). Younger age, Bx haplotype, and the combination KIR3DS1/KIR3DL1 present/HLA-Bw4 present were significantly associated with relapse. KIR genotypes could prove useful in identifying patients that are likely to maintain MR(4.5) after discontinuing TKI treatment.

Defining Therapy Goals for Major Molecular Remission in Chronic Myeloid Leukemia: Results of the Randomized CML-Study IV

Background: In the current ELN recommendations (Baccarani et al., Blood 2013) the optimal time point to achieve major molecular remission (MMR) is defined at 12 months after diagnosis of CML. MMR is not a failure criterion at any time point leading to uncertainties when to change therapy in CML patients not reaching MMR after 12 months. Aims: We sought to evaluate a failure time point for MMR using data of the CML-Study IV, a randomized five-arm trial designed to optimize imatinib therapy alone or in combination. In addition the optimal time-point to achieve a MMR should be evaluated. Methods: Patients with valid molecular analysis on MR4 level were divided randomly into a learning (LS) and a validation sample (VS). For the LS, MR2 (defined as BCR-ABL Results: 1551 patients were randomized from 2002 to 2012, 1358 had a valid molecular analysis on the MR4 level. 114 patients in the imatinib after IFN arm and 16 patients with missing EUTOS score were excluded. Of the 1228 evaluable patients two thirds were randomly allocated to the LS (n=818) and one third to the VS (n=410). Percentage of patients of the LS in MR2, MMR and MR4 or deeper at one year was 28%, 29% and 14%, and at 5 years 5%, 21% and 71%, respectively. Monthly time points in between were also calculated. 44 patients of the LS reached MMR on second generation tyrosine kinase inhibitors.. The minimum of the cubic function of the HRs was found for MMR at 2.34 years with a HR of 0.25 (compared to patients without any remission) and 0.75 compared to those in MR2. For MR4 or deeper no exact time point could be calculated (see Fig. 1), although it was shown that the risk of progression was slightly lower for MR4 than for MMR. Since the time interval for molecular evaluation in the study is 3 months, the validation was done with 2.25 instead of 2.34 years. 364 of the 410 of the VS were still at risk at this time point and evaluable. A significant PFS advantage for patients in MMR could be demonstrated (p=0.018). At 8 years, the probability of PFS for patients in MMR was 90.8% (confidence interval 87.0-93.7%) vs. 80.5% (confidence interval 70.2-88.6%) for patients not in MMR (see Fig 2). For the optimal MMR analysis no singular time point could be calculated as the earlier a MMR was reached the higher was the chance to achieve a MR4. Conclusions: In this model, an optimal time point to predict PFS in patients with MMR was defined at 2.25 years after diagnosis and could be validated as significant. Nevertheless, patients being in MMR had a lower risk of progression than patients not being in MMR on any other time point as well. With this model we can give hints when to define MMR as failure and a change in therapy should be considered. Despite this we should keep in mind that the earlier MMR was achieved the higher was the chance to achieve deep molecular response later during therapy. Disclosures Saussele:Novartis: Honoraria, Research Funding, Travel Other; Bristol-Myers Squibb: Honoraria, Research Funding, Travel, Travel Other; Pfizer: Honoraria, Travel, Travel Other. Hehlmann:Bristol-Myers Squibb: Research Funding; Novartis: Research Funding. Schnittger:MLL Munich Leukemia Laboratory: Equity Ownership. Hanfstein:Novartis: Research Funding; Bristol-Myers Squibb: Honoraria. Neubauer:MedUpdate: Honoraria, Speakers Bureau. Kneba:Novartis: Consultancy, Equity Ownership, Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding. Pfirrmann:Novartis: Consultancy; Bristol-Myers Squibb: Honoraria. Hochhaus:Novartis: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Consultancy, Honoraria; ARIAD: Honoraria, Research Funding; Pfizer: Consultancy, Research Funding. Muller:Novartis: Honoraria, Research Funding; Bristol Myers Squibb: Honoraria, Research Funding; ARIAD: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding.

Advances in Immunotherapy of Chronic Myeloid Leukemia CML

Tyrosine kinase inhibitors induce sustained disease remissions in chronic myeloid leukemia by exploiting the addiction of this type of leukemia to the activity of the fusion oncogene BCR-ABL. However, these agents fail to eradicate CML stem cells which are ultimately responsible for disease relapses upon treatment discontinuation. Evidence that the immune system can effectively reject CML stem cells potentially leading to patient cure is provided by the experience with patients receiving allogeneic bone marrow transplantations. Compelling evidence indicates that more modern, antigen-specific immunotherapeutic approaches are also feasible and hold strong potential to be clinically effective. Amongst these, particularly promising is the use of autologous dendritic cells pulsed with antigens or direct application of in vitro transcribed RNA encoding for leukemia-associated antigens, since this approach allows to circumvent HLA-restriction of the leukemia-associated T cell epitopes that have been eventually identified. Combining these strategies with monoclonal antibodies, such as anti-CTLA-4 or anti-PD-1, may help to obtain even stronger immune responses and better clinical results. This narrative review addresses this topic by focusing in particular on the cell-based immunotherapeutic strategies for CML and on the issue of the leukemia-associated antigens to be selected for targeting.

Jak2V617F myeloproliferative neoplasm stem cells and interferon-alpha

The myeloproliferative neoplasms (MPNs) are clonal disorders of hematopoiesis that arise as a result of aberrant activation of tyrosine kinases and result in the proliferation and accumulation of mature myeloid cells in the blood, bone marrow and spleen. The prototypical MPN, chronic myeloid leukemia (CML) is caused by constitutive activation of ABL kinase occurring as a result of the BCR-ABL fusion. Importantly, targeted therapy to inhibit ABL kinase signaling, using imatinib, induces durable clinical responses in the majority of CML patients. The molecular pathogenesis of the BCR-ABL negative MPNs, polycythemia vera (too many red cells), essential thrombocythemia (too many platelets) and myelofibrosis, was elucidated in 2005 with the discovery of JAK2V617F, an activating mutation in the non-receptor tyrosine kinase, JAK2 [1]. The JAK2V617F mutation is present in more than 95% patients with polycythemia vera, and approximately 50% patients with essential thrombocythemia and myelofibrosis. In advanced disease, MPN may transform to acute leukaemia and this is associated with a dismal prognosis. In MPN, JAK2V617F is found in long-term hematopoietic stem cells (LT-HSCs), a population of rare quiescent cells present in the bone marrow and capable of long-term self-renewal. These somatically mutated LT-HSCs, referred to as MPN-propagating cells or MPN stem cells, maintain the MPN throughout the life of the patient and can serially transplant disease in animal models of Jak2V617F-mediated MPN [2, 3]. To definitively cure MPN will require complete eradication of the MPN disease-maintaining stem cell population. In contrast to the efficacy of imatinib in achieving molecular remissions in CML, JAK2 kinase inhibitors have shown only modest benefit in the treatment of myelofibrosis, namely in reducing splenomegaly and improving constitutional symptoms. Furthermore, the lack of an effect of the JAK2 inhibitors on reducing JAK2V617F allele burden in myelofibrosis patients [4] and the demonstration that MPN-propagating cells are insensitive to JAK2 kinase inhibition in vivo [2] suggests that MPN stem cells do not require JAK2 signaling for survival and that JAK2 inhibitor monotherapy will not cure MPN patients. The clinical efficacy of long-acting pegylated IFNα in MPN has renewed interest in understanding the mechanism of action of IFNα treatment in JAK2V617F-mediated MPN. Prolonged IFNα treatment results in normalization of blood counts in most patients with polycythemia vera, reduces JAK2V617F allele burden and in 15-40% of patients, the JAK2V617F mutant clone is rendered undetectable to sensitive molecular assays[5, 6]. These clinical results suggest that IFNα eradicates JAK2V617F-mutant LT-HSC, however the mechanism by which molecular remissions are achieved in MPN patients in response to treatment with IFNα have not been well defined. Figure 1 MPN stem cells are responsible for disease initiation and propagation in vivo To determine the efficacy of IFNα therapy on Jak2V617F-positive MPN stem cells in vivo, we used a murine model of Jak2V617F-mediated MPN [7]. We found that prolonged treatment of Jak2V617F mice with IFNα reversed the myeloproliferation phenotype (normalizing hemoglobin and white cell count and reducing extramedullary hematopoiesis). Importantly, we observed selective depletion of Jak2V617F over WT LT-HSC and this correlated with an inability of IFNα treated mice to propagate MPN into transplanted recipients. IFNα can directly activate the cell cycle in quiescent wild-type (WT) LT-HSCs and induce HSC proliferation in vivo [8]. We found that IFNα treatment induced enhanced cell-cycle activation of Jak2V617F-mutant LT-HSCs, as compared to WT LT-HSCs, explaining this preferential depletion over time. Using Ifnar1 knock-out mice (lacking the type 1 interferon receptor), we showed that the effects of IFNα on cell cycle are specifically mediated through type 1 interferon signaling and are intrinsic to Jak2V617F-mutant LT-HSCs. Using gene expression analysis we found an enrichment of cell cycle genes in Jak2V617F-mutant LT-HSC, both at baseline and after IFNα treatment, providing a potential explanation for their preferential sensitivity to IFNα treatment. This work suggests that IFNα achieves molecular remissions in JAK2V617F-positive MPN patients through the activation and consequent depletion of quiescent MPN disease-propagating cells. What are the clinical implications of this work? Firstly, these data support the rational design of clinical trials to test combinatorial therapeutic approaches using IFNα (to target quiescent MPN-stem cells) together with JAK2 kinase inhibitors or cytotoxic chemotherapy (to target actively cycling progenitor populations). Plausibly, the depletion of MPN stem cells in polycythemia vera could alter the natural history of the disease, through eliminating the malignant clone and thus preventing fibrotic and/or leukemic transformation, both devastating complications of MPN. Currently, IFNα is far from an ideal drug, and few patients are able to tolerate prolonged treatment due to its side effects. We have identified a number of novel targets that are differentially regulated in Jak2V617F and WT LT-HSCs following IFNα treatment. In ongoing studies, we are working to validate these targets with the goal of developing more specific, less toxic IFNα derivatives capable of selectively eliminating MPN stem cells, while sparing normal LT-HSCs and other organ systems.

Targeting primitive chronic myeloid leukemia cells by effective inhibition of a new AHI-1-BCR-ABL-JAK2 complex.

BackgroundImatinib mesylate (IM) induces clinical remission of chronic myeloid leukemia (CML). The Abelson helper integration site 1 (AHI-1) oncoprotein interacts with BCR-ABL and Janus kinase 2 (JAK2) to mediate IM response of primitive CML cells, but the effect of the interaction complex on the response to ABL and JAK2 inhibitors is unknown.MethodsThe AHI-1–BCR-ABL–JAK2 interaction complex was analyzed by mutational analysis and coimmunoprecipitation. Roles of the complex in regulation of response or resistance to ABL and JAK2 inhibitors were investigated in BCR-ABL + cells and primary CML stem/progenitor cells and in immunodeficient NSG mice. All statistical tests were two-sided.ResultsThe WD40-repeat domain of AHI-1 interacts with BCR-ABL, whereas the N-terminal region interacts with JAK2; loss of these interactions statistically significantly increased the IM sensitivity of CML cells. Disrupting this complex with a combination of IM and an orally bioavailable selective JAK2 inhibitor (TG101209 [TG]) statistically significantly induced death of AHI-1–overexpressing and IM-resistant cells in vitro and enhanced survival of leukemic mice, compared with single agents (combination vs TG alone: 63 vs 53 days, ratio = 0.84, 95% confidence interval [CI] = 0.6 to 1.1, P = .004; vs IM: 57 days, ratio = 0.9, 95% CI = 0.61 to 1.2, P = .003). Combination treatment also statistically significantly enhanced apoptosis of CD34+ leukemic stem/progenitor cells and eliminated their long-term leukemia-initiating activity in NSG mice. Importantly, this approach was effective against treatment-naive CML stem cells from patients who subsequently proved to be resistant to IM therapy.ConclusionsSimultaneously targeting BCR-ABL and JAK2 activities in CML stem/progenitor cells may improve outcomes in patients destined to develop IM resistance.

Sequential Treatment After Allogeneic Stem Cell Transplantation for Chronic Myelogenous Leukemia.

AbstractAbstract 3129 BackgroundTyrosine kinase inhibitors (TKI) have revolutionized treatment of chronic myeloid leukemia (CML), nonetheless as seen in follow-up of the IRIS study, almost 30% of patients discontinued imatinib due to inadequate response or intolerance. Allogeneic stem cell transplant (ASCT) remains the only effective treatment to produce durable complete remissions in CML; curative effect is largely derived from immune graft-versus-leukemia (GVL) effect mediated by alloreactive donor T cells reacting against residual host malignant cells. We evaluated sequential therapy after a nonmyeloablative preparative regimen, designed to reduce risks of toxicity, graft-versus-host disease (GVHD) and treatment related mortality. Patients with residual CML 3 months post ASCT received imatinib and those without a complete molecular remission after an additional 3 months received donor lymphocyte infusions (DLI).Patients and Methods Objective:To increase frequency of achievement of complete molecular response (CMolR) following reduced intensity ASCT. Eligibility:CML in chronic phase (CP) with failure to respond/intolerance to one or more TKIs. Patients received a reduced intensity preparative regimen involving fludarabine 40 mg/m2 × 4 days, busulfan 130 mg/m2 × 2 days, and antithymocyte globulin (Thymoglobulin) 2.5 mg/kg daily × 3 days followed by ASCT from an HLA identical or one antigen mismatched related or unrelated donor. GVHD prophylaxis was tacrolimus and methotrexate (5 mg/m2 on SCT days 1, 3, 6 and 11). Patients who had engraftment but residual disease by quantitative PCR for bcr-abl rearrangement at 3 months post ASCT received imatinib treatment with dose titrated to hematologic toxicity. Those with residual disease 6 months post ASCT and no active GVHD received DLI. Patients were treated between 4/2003 - 6/2008; median follow up was 74 months (4–99). Outcome of interest was progression free survival (PFS) and overall survival (OS), estimated using Kaplan-Meier estimate, and survival comparisons between groups was by log rank test. ResultsPatient characteristics summarized in Table 1; response analysis in Table 2. 41 patients were entered on study, all were previously treated with a TKI; at time of ASCT, 10 were in first chronic phase (CP1), 8 had isolated clonal evolution (CE) and 23 had a history of advanced CML (>CP1, or accelerated phase). One patient died within 100 days post HSCT and 3 had graft failure; one required a second transplant; 2 had autologous recovery with CMolR and are both alive. At 3 months, all patients in CP1 or with CE (18/44%) obtained complete cytogenetic response (CCgR); 15(36%) of 23 advanced patients achieved CCgR. CMolR was attained by 8 patients, 4 in CP1. No one with minimal residual disease achieved a CMolR without intervention. 22 patients received treatment with TKIs post ASCT; and of those 9 later received DLI. CMolR was achieved in 12 of 22 patients who had molecular progression post ASCT. 26 patients are alive at last follow up and 15 deaths were due to, relapsed leukemia (9), GVHD (3), and infection (3), respectively. ConclusionIn conclusion, sequential therapy including reduced intensity HSCT, post transplant treatment with TKI, and donor lymphocyte infusion was associated with a low rate of treatment related mortality. This approach is capable of prolonged cytogenetic and molecular complete remissions and survival. Disease status at time of transplant was the most important prognostic factor. This is an effective option for patients in chronic phase who have failed to respond optimally to TKI based treatment.Table 1- Patient CharacteristicsN (%)N (%)Age at TP, med (range)42 (14–69)Median f/up in alive, mo74 (4–99)Age ≥50 yr10 (76)% OS60% (42–74)≤5031 (24)% PFS56% (38–70)Donor TypeMRD21/51%Disease statusMUD19/46%CP110/24%Ag MM rel1/2%CP214/34%TKI prior to transplantN (%)≥CP35/12%Imatinib33/80%AP13/7%Dasatinib6/15%AP21/2%Nilotinib1/2%CE8/20%Bafetinib1/2%Table 2- Responses After Sequential Therapy Protocoln= 41Response to prep regimen at 3 moMolecular CR to imatinib (n=22)Molecular CR to DLI (n=9)Alive/CCgR/CMolRRelapse/DeadCP1 n=10CCgR = 10 (100%)1 of 41 of 210/10/50/0CMolR = 4 (40%)CP2/CE/AP1 n=25CCgR = 21 (84%)4 of 175 of 717/16/118/10CMolR= 3 (12%)AP2/≥CP3 n=6CCgR = 2 (33%)1 of 1none1/1/15/5CMolR = 1 (17%)Disease statusOSpPFSpN=15 diedN=17CP11000.0200.01CP2/AP1/CE25912≥CP3/AP2655 [Display omitted] Disclosures:No relevant conflicts of interest to declare.

Label‐free MSE proteomic analysis of chronic myeloid leukemia bone marrow plasma: disclosing new insights from therapy resistance

Chronic myeloid leukemia (CML) is a pluripotent hematopoietic disorder that is currently considered incurable. The tyrosine kinase product of the Philadelphia chromosome, P210 BCR-ABL, provided a pathogenetic explanation for the initiation of the CML chronic phase and is the molecular therapeutic target for the disease. Imatinib mesylate, an orally available BCR-ABL kinase inhibitor, can induce haematologic and cytogenetic remission of CML. However, imatinib resistance occurs frequently, resulting in relapse. New treatment strategies are focusing on resistant CML stem cells and the bone marrow stroma. The identification of novel pathways and mechanisms in the bone marrow microenvironment could significantly contribute to the development of such strategies. In this work, we used a high-resolution label-free MS(E) proteomic approach to identify differential protein expression in the CML bone marrow plasma of responsive and resistant patients. Oxidative lipid metabolism and regulation of the switch from canonical to noncanonical WNT signaling may contribute to CML resistance in the bone marrow compartment.

Molecular and structural characterization of the SH3 domain of AHI‐1 in regulation of cellular resistance of BCR‐ABL+ chronic myeloid leukemia cells to tyrosine kinase inhibitors

ABL tyrosine kinase inhibitor (TKI) therapy induces clinical remission in chronic myeloid leukemia (CML) patients but early relapses and later emergence of TKI-resistant disease remain problematic. We recently demonstrated that the AHI-1 oncogene physically interacts with BCR-ABL and JAK2 and mediates cellular resistance to TKI in CML stem/progenitor cells. We now show that deletion of the SH3 domain of AHI-1 significantly enhances apoptotic response of BCR-ABL(+) cells to TKIs compared to cells expressing full-length AHI-1. We have also discovered a novel interaction between AHI-1 and Dynamin-2, a GTPase, through the AHI-1 SH3 domain. The crystal structure of the AHI-1 SH3 domain at 1.53-Å resolution reveals that it adopts canonical SH3 folding, with the exception of an unusual C-terminal α helix. PD1R peptide, known to interact with the PI3K SH3 domain, was used to model the binding pattern between the AHI-1 SH3 domain and its ligands. These studies showed that an "Arg-Arg-Trp" stack may form within the binding interface, providing a potential target site for designing specific drugs. The crystal structure of the AHI-1 SH3 domain thus provides a valuable tool for identification of key interaction sites in regulation of drug resistance and for the development of small molecule inhibitors for CML.

Telomere loss in Philadelphia-negative hematopoiesis after successful treatment of chronic myeloid leukemia: Evidence for premature aging of the myeloid compartment

Telomere shortening, a well-known marker of aging and cellular stress, occurs under several conditions in the hematopoietic compartment, including aplastic anemia and following iatrogenic noxae. We decided to verify whether pathological telomere erosion also arises in restored Philadelphia-negative (Ph-negative) hematopoiesis following successful treatment of chronic myeloid leukemia (CML). Eighty-one CML patients in complete cytogenetic remission were compared to 76 age-matched healthy subjects. Myeloid cells of CML patients had shorter telomeres than controls (6521bp vs 7233bp, p<0.001). This difference was specific for the myeloid compartment, since it was not observed in lymphoid cells (6774bp vs 6909bp, p=0.620). Acquired Ph-negative cytogenetic abnormalities (p=0.010), lack of complete molecular remission (p=0.016) and age (p=0.013) were independent predictors of telomere shortening. Telomere dynamics were assessed over a median follow-up period of 22 months. We documented accelerated non-physiological ongoing telomere shortening in 17/59 CML patients (28%). Patients experiencing grade 2–4 hematological toxicity, during CML remission possessed significantly shorter telomeres compared to those lacking toxicity (p=0.005 for any toxicity, p=0.007 for anemia). CML patients suffer from significant and often ongoing telomere stress resulting in premature and selective aging of the myeloid compartment which might have long-term consequences on function and integrity of Ph-negative hematopoiesis.

P-0226 Colorectal Cancer as a Second Malignancy in Patients with Chronic Myeloid Leukemia – Incidence and Treatment Tactics

ABSTRACT Introduction Occurrence of second neoplasia in patients with chronic myeloid leukemia (CML) is a rare event - especially colorectal cancer (CRC). There are difficulties in choosing treatment strategy of two concurrent diseases, in particular, continuation of therapy for maintenance of cytogenetic or molecular remission of CML and radical treatment for CRC. The purposes of the work are: to assess frequency of CRC in patients with CML, registered in industrial region of Ukraine with population of 5.2 million inhabitants within the period of 2002 - 2011, as well as to assess connection between CRC frequency and previous treatment (chemotherapy / interferon / imatinib mesylate) and to evaluate retrospectively treatment tactics for patients with early CRC, locally advanced and metastatic CRC. Methods The analysis of 10-year period data provided by regional branches of the National Cancer Registry of Ukraine on number of patients registered with diagnosis of CML, as well as data on registration of colorectal cancer cases within this patients` group have been performed. The treatment tactics and status of CML patients at time of detection of colorectal cancer (complete remission, progression to accelerated phase or blast crisis), as well as time interval from the date of registration of CML to time of CRC detection have been evaluated. Results According to data of regional branch of the National Cancer Registry of Ukraine there were 4 cases of CRC out of 443 CML patients (0.9%) within the period of 2002 - 2011. Median observation of patients with the CML before detection of CRC was 24.5 months. Three patients with CML (75%) were in phase of cytogenetic or molecular remission at the moment of detection of CRC. Only one CML patient received imatinib mesylate as a first line therapy with cytogenetic and large molecular remission duration of 31 months. Sigmoid colon cancer (low-differentiated adenocarcinoma) was diagnosed in the TNM stage pT4pN1M0G3. Radical resection of the sigmoid colon was performed with subsequent adjuvant chemotherapy. At that, imatinib mesylate therapy (400 mg daily) was not interrupted. No significant side effects were observed. Conclusion Occurrence of second malignancy of CRC in CML patients corresponds to CRC frequency of Ukrainian population of appropriate age. Continuation with imatinib mesylate therapy may take place subject to relevant indications for chemotherapy of CRC. The toxicity of this combination therapy is acceptable.

Durable complete molecular remission of chronic myeloid leukemia following dasatinib cessation, despite adverse disease features

Patients with chronic myeloid leukemia, treated with imatinib, who have a durable complete molecular response, might remain in complete molecular response after stopping treatment. Previous reports of patients stopping treatment in complete molecular response have included only patients with a good response to imatinib. We describe 3 patients with stable complete molecular response on dasatinib treatment following imatinib failure. Two of the 3 patients remain in complete molecular response more than 12 months after stopping dasatinib. In these 2 patients we used highly sensitive patient-specific BCR-ABL1 DNA PCR to show that the leukemic clone remains detectable, as we have previously shown in imatinib-treated patients. Dasatinib-associated immunological phenomena, such as the emergence of clonal T-cell populations, were observed both in one patient who relapsed and in one patient in remission. Our results suggest that the characteristics of complete molecular response on dasatinib treatment may be similar to that achieved with imatinib, at least in patients with adverse disease features.