Patients In Blastic Phase Research Articles

Allogeneic Stem Cell Transplantation In Philadelphia Negative Myeloproliferative Or Myelodysplastic/Myeloproliferative Neoplasms: A Retrospective Analysis From The Societe Française De Greffe De Moelle Et De Therapie Cellulaire (SFGM-TC)

BackgroundPhiladelphia negative myeloproliferative or myeloproliferative/myelodysplastic neoplasms may evolve towards secondary acute myeloid leukemia (AML). The prognosis of such secondary leukemia is very poor. At present, there are only a few reports assessing the outcome of adult patients with a philadelphia negative myeloproliferative or myeloproliferative/myelodysplastic neoplasm in blast phase (MPN-BP) who received allogeneic stem cell transplantation (allo-SCT). Patients and Methodsin this retrospective study, inclusion criteria were: (i) adult patients with a MPN-BP (ii) who received first allo-SCT (iii) between 2000 and 2010 (iv) irrespective of the stem cell source or conditioning regimen. MPN with <20% blasts in blood/bone marrow and AML secondary to myelodysplastic syndromes were excluded from this analysis. Results60 patients were included. MPN, AML and allo-SCT characteristics are described in table 1. Median age at allo-SCT was 57 (range, 30-68). Patients received allo-SCT in first complete remission (CR1), CR2 or in advanced disease in 22 (37%), 4 (7%) and 34(57%) of cases, respectively. Engraftment was achieved in 55 cases (92%). With a median follow-up of 31 months (range, 25-44), the 3-year overall survival (OS) and Leukemia-Free-Survival (LFS) were respectively 18% and 9%. The 3-year transplant-related mortality (TRM) was 24% whereas relapse incidence was 68%. The 3-year LFS of patients grafted in CR (n=26) was 18% whereas the 3-year LFS of patients allografted in advanced disease (n=34) was only 3% (p=0.008). In the CR group, the 3-year TRM was 24% whereas relapse incidence was 61%. Intermediate or good AML karyotype (3-year LFS of 33% versus 10% for adverse AML karyotype, p=0.03) and the absence of a previous thrombotic event (3-year LFS of 24% versus 0, p=0.02) were associated with an improved LFS in patients allografted in CR.Table 1MPN and AML characteristicsN60Patient genderMale: 46 (77%)MPNMyeloproliferative neoplasms: 43Polycythemia vera: 10Essential Thrombocytemia: 20Primary myelofibrosis: 8Other: 5Myelodysplastic/myeloproliferative neoplasms: 17Chronic myelomonocytic leukemia: 15Other: 2Time from MPN diagnosis to blast phase (months)66 (range, 4-330)Median age at time allo-SCT (years)57 (range, 30-68)AML karyotypeFavorable: 1Normal: 16Other intermediate risk: 9Adverse: 25Failed: 9AML therapy before allo-SCTIntensive chemotherapy: 50Hypomethylating agent: 6Upfront allo-SCT: 7AML status at allo-SCTCR1: 22CR>1: 4advanced: 34Stem cell sourceBone Marrow: 10Peripheral Blood Stem Cell: 44Cord Blood: 6Conditioning regimenMyeloablative: 14Reduced-intensity regimen: 33Sequential regimen: 13 ConclusionThese results suggest that the outcome of patients with a MPN-BP is dismal despite allo-SCT due to a high relapse incidence even in patients transplanted in CR. Outside a clinical trial, allo-SCT should be mainly proposed to patients in CR. New strategies are mandatory to improve the outcome of patients in blast phase. Disclosures:No relevant conflicts of interest to declare.

Treosulfan Based Myeloablative Regimen Provides High Rate Of Allogeneic Engraftment and Low Toxicity In Patients With Advanced Myelofibrosis,

AbstractAbstract 5504 BackgroudAllogeneic transplantation (HSCT) is the only potentially curative therapy for myelofibrosis, even in the era of new drugs that only impact on selected manifestations of disease. The time to evolution of myelofibrosis in advanced phases is variable (months to several years). The choice to proceed to allogeneic transplantation is based on several clinical variables; conditioning regimen and time to transplantation may influence the outcome of HSCT. Here we present our experience in a group of patients with myelofibrosis transplanted in Our Center with a myeloablative regimen based on full dose of treosulfan. MethodsWe retrospectively evaluated 20 patients (15 male) with primary myelofibrosis (14) and post-ET (essential thrombocythemia) myelofibrosis (6) who underwent HSCT at our institute from July 2005 to February 2013. In this cohort we included 4 patients in blast phase, 3 of which received a brief course of chemotherapy prior to transplant; 4 patients who underwent a second allogeneic transplantation for disease relapse (2) or graft failure (1); 1 patient referred at our Institute in graft failure 3 months after first HSCT. Only 1 patient had splenectomy before HSCT. ResultsThe median age at diagnosis was 59 years (range 41-76). JAK2 V617F mutation was positive in 7 and unknown in 3 patients. In post-ET MF patients, the median time to transformation in MF was 134 months (60-144). The median time from diagnosis to transplant was 14 months (4-101 months). The median age at transplant was 62 years. DIPSS score at transplant was low in 1, int-1 in 3, int-2 in 13 and high in 3 patients. We adopted myeloablative regimen based on treosulfan 42 gr/ms and fludarabine 150 mg/ms, plus TBI 4 Gy in 7 patients. GvHD prophylaxis was based on ATG, Rituximab and CSA/MTX (8 pts) or rapamycin (11 pts). The graft was PBSCs (19) and BM (1) from related HLA-identical donor (7 pts), matched unrelated donor (5 pts) and haploidentical donor (8 pts). The incidence of graft failure and poor graft function was 5% and 20% respectively. The median time to neutrophils engraftment was 20 days. The incidence of acute and chronic graft versus host disease was 50% and 40% respectively. Cumulative incidence of TRM (transplant related mortality) was 45 %; day 100 OS (overall survival) was 70% while 2 year OS was 40%. In multivariate analysis there was no statistically significant correlation between individual factors (including WBC, hemoglobin, platelets, ferritin, beta2-microglobulin, IgA, IgG, IgM, LDH, psuedocholinesterase levels, age, Sorror comorbidity score, donor match, bone marrow kariotype) and survival. However, we found that a linear composition of level of peripheral blasts (0%, ≥1%, ≥5%), bone marrow CD34+ cells (<5%, ≥5%, ≥20%), spleen size and number of red blood cells units transfused pre-HSCT is able to predict the outcome (p-value 0.03), even if each factor alone is not strongly correlated with survival. There was no statistical significant correlation between the outcome and DIPSS score, Bacicalupo score and Lille score. ConclusionsA myeloablative regimen based on full dose treosulfan provide a 95% rate of primary allogeneic engraftment and 40% overall survival in myelofibrosis at advanced stage, with low extra-hematological toxicity in frail patients. Allogeneic transplantation after myeloablative low-toxicity regimens may be offered in myelofibrosis in early chronic phase of disease and for younger patients, two conditions usually linked with durable engraftment, low toxicities and low rate of relapse. Disclosures:No relevant conflicts of interest to declare.

Adverse Prognosis Of Extramedullary Disease In Patients With Chronic Myeloid Leukemia (CML) In The Tyrosine Kinase Inhibitor (TKI) Era: a Cohort Study Of 283 Blastic Phase CML Patients

BackgroundWith the advent of tyrosine kinase inhibitors (TKIs), significant improvement has been made in the survival outcome of chronic myeloid leukemia (CML) patients. However, blastic phase (BP) CML remains a therapeutic challenge. Extramedullary disease (EMD) is a diagnostic criterion for BP, and patients with this presentation represent a unique subgroup of BP CML. The characteristics of EMD in BP CML patients have not been well described, especially in the era of TKIs. MethodsWe have analyzed CML patients with extramedullary BP either at the time of diagnosis or progressing from CP/AP from 2000 to 2011 and treated with different TKIs such as imatinib, nilotinib, dasatinib, bosutinib, and ponatinib at a single institution. All demographic, clinicopathologic variables and medication data including TKIs were collected at the time of the diagnosis of BP. Primary outcomes, overall survival (OS) were defined as time from diagnosis of BP to death. ResultsAmong a total of 284 BP CML patients, median age was 52.6 (range: 15-81) years. Males were 65.0%. 72.2% were in myeloid BP versus 27.7% in lymphoid BP. Median follow up was 1.5 (range: 0.01-12) years. Median time from diagnosis of CML to BP was 2.3 (range: 0.01-28) years. 128 (45%) patients have died. Cytogenetic analysis at diagnosis demonstrated that 34% had only Philadelphia chromosome (Ph) present while 66% had other chromosomal abnormalities besides Ph. Trisomy 8 was the most common additional chromosomal abnormality (18%). 280 (99%) were treated with TKIs. Among them, 176 (623%) were treated with TKI monotherapy, and the rest with a combination of TKI and conventional chemotherapy. Among the patients treated with TKI, 134 (48%) used imatinib; 85 (30%), dasatinib; 48 (17%), nilotinib; 7 (3%), bosutinib; and 6 (2%), ponatinib.EMD was diagnosed in 78 patients (28%) of all BP CML patients. Patients with EMD had a median age of 52.8 (range: 19-80) while BP patients without EMD had a median age of 52.2 (range: 15-81). There were no statistically significant differences in age, gender, ethnicity, or time from diagnosis of CML to BP between EMD and non-EMD patients. Among patients with EMD 76% were myeloid, and 23% lymphoid compared with 70% myeloid and 30% lymphoid in patients without EMD (p=0.3). Patient with EMD had more Ph-only disease compared with patients without EMD (41% vs. 28%, p=0.03). Among 28 patients with deletion 7 chromosomal abnormality, only 1 patient had EMD (EMD vs. non-EMD chi-square p=0.002). There was no association between the presence of EMD and other chromosomal abnormalities such as double Ph, isochromsome 17, trisomy 8, deletion Y and variant Ph. Among patients with EMD, 39 (50%) had EMD in CNS; 22 (28%) in soft tissue, skin, or lymph nodes; 9 (12%) in bones; 8 (10%) in lung or pleura; and 4 (5%) in GI tract and liver.Among patient with BP CML, there were no statistically significant differences between the EMD and non-EMD groups in both complete hematologic response (CHR) rate and complete cytogenetic response (CCyR) rate at 3 months after the initiation of therapy (CHR: EMD 18% vs. non-EMD 22%, p=0.4; CCyR: EMD 8% vs. non-EMD 15%, p=0.1). However, the presence of EMD was associated with worse survival outcome (Hazard Ratio [HR]=1.62, Confidence Interval [CI]= 1.13-2.32, p=0.008). Median overall survival in patients with EMD was 0.8 versus 2.5 years in patients without EMD (log-rank test p=0.008, Figure 1). EMD in CNS was not associated with survival (HR=0.87, CI=0.50-1.51, p=0.6). In multivariate analysis controlling for age, gender, ethnicity, white cell counts, cytogenetics (presence of additional chromosomal abnormality), and pathology (myeloid versus lymphoid), EMD was still linked with adverse survival (adjusted HR=1.53, CI=1.04-2.26, p=0.03). [Display omitted] ConclusionBP CML patients presenting with EMD are likely to have less additional chromosomal abnormality and have inferior overall survival compared with those without EMD. EMD may represent more aggressive pathophysiology in BP CML and may require more intensive treatment. Disclosures:No relevant conflicts of interest to declare.

OP449, a Novel SET Antagonist, Is Cytotoxic To Leukemia Cells and Enhances Efficacy Of Tyrosine Kinase Inhibitors In Drug-Resistant Myeloid Leukemias

BackgroundThe SET oncoprotein, an inhibitor of the protein phosphatase 2A (PP2A), is overexpressed in leukemia cells, preventing PP2A from performing its regulatory role in deactivating signaling proteins by dephosphorylation. Restoration of PP2A activity in both chronic myeloid leukemia (CML) and acute myeloid leukemia (AML) cells to normal levels through shRNA-mediated knockdown of SET results in reduced leukemogenesis. Given the central role of PP2A and SET in regulating various kinase-dependent and -independent downstream signaling pathways, we evaluated the efficacy of SET antagonism in CML and AML cell lines as well as primary patient cells using OP449, a novel, specific, cell-penetrating SET antagonist. ResultsTreatment of human and murine CML cells with OP449 resulted in dose-dependent increase in PP2A activity and selective inhibition of cell growth (IC50: 0.60 to 1.11 μM), while parental Ba/F3 cells exhibited no measurable cytotoxicity. OP449-mediated decrease in the viability of leukemia cells was significantly rescued by co-treatment with okadaic acid, a PP2A inhibitor, confirming efficacy is mediated through PP2A activation. OP449 was also 3 to 8-fold more potent than FTY720 (a known activator of PP2A) and induced dephosphorylation/degradation of BCR-ABL1, AKT, and STAT5. Importantly, OP449 demonstrated activity against the ABL1 tyrosine kinase inhibitor-resistant BCR-ABL1T315I mutant and the BCR-ABL1E255V/T315I compound mutant (IC50: 1.62 and 1.97 μM, respectively). Consistent with cell line findings, OP449 also inhibited growth of primary cells from CML blastic phase patients harboring either wildtype BCR-ABL1 or BCR-ABL1T315I while normal CD34+ cells exhibited minimal effect. Further, treatment of CML cell lines and primary CD34+ CML cells with OP449 in combination with the ABL1 tyrosine kinase inhibitors showed significantly increased cytotoxicity as compared to each compound alone. For example, treatment of primary CD34+ CML cells with 2.5 μM OP449 or 200 nM nilotinib alone each resulted in a 50% reduction in colony formation, while combination of OP449 and nilotinib at these concentrations reduced colony formation by approximately 87%, suggesting synergistic reduction of clonogenicity (combination index: 0.195). Similar to our findings in CML cells, OP449 increased PP2A activity and suppressed growth in a dose-dependent manner in AML cell lines and primary patient samples harboring various different genetic lesions including FLT3-ITD, CSF1R overexpression, NRASQ61L, and JAK3A572V. Additionally, synergistic inhibition of these cells was observed when OP449 was combined with relevant tyrosine kinase inhibitors and chemotherapy. For example, treatment of MOLM-14 cells (FLT3-ITD) with 2.5 μM OP449 or 1 nM AC220 alone reduced cell viability by 58% and 75%, respectively; combined treatment reduced cell growth 96% (combination index: 0.723). Similarly, treatment of HL-60 cells (NRASQ61L) with 1 μM OP449 or 250 nM cytarabine alone reduced cell viability by 40% and 60%, respectively, whereas combined treatment led to a 94% reduction in viability (combination index: 0.630). Mechanistically, AML patient samples showed significantly increased SET expression compared to normal CD34+ cells, and treatment of AML cells with OP449 reduced phosphorylation of downstream ERK, STAT5, AKT and S6 ribosomal protein signaling. Finally, to evaluate OP449 antitumor efficacy in vivo, we tested OP449 (5 mg/kg intraperitoneally every 3 days) in xenograft mice bearing human HL-60 cell derived tumors. OP449 significantly inhibited tumor growth measured over time and resulted in a >2-fold reduction in tumor burden at the end of the experiment compared to vehicle-treated controls (Day 18: 1.14±0.06 g vs. 0.45±0.08 g, respectively; p<0.001). These results demonstrate the in vivo efficacy of OP449 in a murine leukemia model. ConclusionsSET antagonism is selectively cytotoxic to CML and AML cells harboring various genetic lesions and drug-resistant mutations. Our results demonstrate that combined targeting of SET and tyrosine kinases provides more efficient and selective inhibition of leukemia cell growth for a broad range of oncogenic lesions as compared to normal cells. Taken together, our findings suggest a novel therapeutic paradigm of SET antagonism in combination with tyrosine kinase inhibitors for the treatment of CML and AML patients with drug resistance. Disclosures:Agarwal:Oncotide Pharmaceuticals: Research Funding. Tyner:Incyte Corporation: Research Funding. Vitek:Oncotide Pharmaceuticals: Employment. Christensen:Oncotide Pharmaceuticals: Employment. Druker:Ambit Biosciences: Consultancy, PI or co-investigator on Novartis clinical trials. OHSU and Dr. Druker have a financial interest in MolecularMD. OHSU has licensed technology used in some of these clinical trials to MolecularMD. Potential conflicts of interest are managed by OHSU., PI or co-investigator on Novartis clinical trials. OHSU and Dr. Druker have a financial interest in MolecularMD. OHSU has licensed technology used in some of these clinical trials to MolecularMD. Potential conflicts of interest are managed by OHSU. Other; Bristol-Myers Squibb/Novartis: Currently PI or co-I on Novartis & Bristol-Myers Squibb clinical trials. His institution has contracts with these companies to pay for patient costs, nurse and data manager salaries, and institutional overhead. He does not derive salary, nor does his lab Other; Oncotide Pharmaceuticals: Research Funding, Subaward from NIH STTR, Subaward from NIH STTR Other.

Efficacy Of Different Therapeutic Approaches In Blastic Phase Of Chronic Myeloid Leukemia: Single Centre Experience

Dramatic changes in overall survival of patients (pts) with chronic myeloid leukemia (CML) in chronic phase (CP) have occurred since tyrosine kinase inhibitors (TKIs) were implemented in the treatment strategy. But there are still many issues in therapy of advanced phase disease, especially in blastic phase (BP). Allogeneic stem cell transplantation (alloSCT) is still the only curative option for CML BP, so all efforts should be focused on bringing pts to alloSCT. Thus optimal approach to obtain at least stable hematologic response before alloSCT is needed.Since 2008, 14 pts (4 more pts with isolated extramedullary BP were not included) with CML BP were admitted to our clinic. These were 8 males and 6 females with a median age of 44 years (range; 21-63) at the time of BP. The types of BP were: biphenotypic (n=1), undifferentiated (n=1), myeloid (n=8) and lymphoid (n=4). All pts except 2 (1 with BP and 1 with accelerated phase) were initially diagnosed as CP. Median time from diagnosis to BP was 37 months (range; 0-83). Before BP all pts except 2 were pretreated with imatinib and 6 of them, after failing imatinib, received one or more new TKIs. First line therapy in BP was monotherapy with new TKI (n=5) or chemotherapy (“7+3”, “RACOP”, low doses of Ara-C, “Hyper-CVAD”, “Dexa+VCR”) with or w/o TKI (n=9). Responses are specified in table 1.FLAG regimen was subsequently given to 5 pts as second or more line therapy after failure of previous monoTKI (n=1) or Rx + TKI (n=4). Median time from BP to FLAG was 3,5 months (range; 1,5-21). The best response to FLAG therapy was complete hematologic (n=1), complete cytogenetic with (n=1) or w/o (n=1) major molecular response. There were no responses in 2 cases. All responders maintain their response after median follow up (FU) of 2 months (range; 1,5-5). All patients treated with FLAG are alive (2 after alloSCT, 3 pending alloSCT). Only 1 ptn reached alloSCT w/o any Rx after monoTKI. AlloSCT was successful in 4/5. Median FU time for patients alive after alloSCT is 12 months (range; 3,5-25). For whole group after a median FU of 14 months, 7/14 (50%) pts are alive, including 4 pts after alloSCT. Estimated 3-year overall survival for all pts is 54% (fig. 1). [Display omitted] ConclusionAll CML BP patients treated with TKIs alone lost their response in a short time. Responses were much more durable in pts treated with Rx +/- TKIs. FLAG regimen was effective even in pts with failure to previous Rx+TKIs. The majority of pts after alloSCT are alive. Chemotherapy, including FLAG with concomitant or subsequent TKIs, had advantage over monoTKI both in overall and progression free survival in CML BP. Disclosures:Lomaia:Novartis: Honoraria, Travel grants Other; Bristol-Myers Squibb: Honoraria, Travel grants, Travel grants Other. Zaritskey:University of Heidelberg: Research Funding.

Allogeneic Stem Cell Transplantation for Chronic Myeloid Leukemia

In recent years new, more potent tyrosine-kinase inhibitors have been introduced to accompany imatinib for the treatment of chronic myeloid leukemia. Most patients in chronic phase obtain an optimal response to these oral agents with minimal toxicity. Allogeneic stem cell transplantation is therefore indicated only in a minority of patients who do not achieve an adequate response to first, second or third generation agents. Patients in accelerated phase have a lower chance of achieving an optimal response on these drugs. For patients in blast phase, transplantation remains the only therapy with curative potential, although now it is increasingly used in combination with tyrosine-kinase inhibitors. In this review we address the role of allogeneic stem cell transplantation in the treatment of this disease and how patients should be transplanted.

Associations Between Baseline Mutation Status and Response to Treatment with Omacetaxine Mepesuccinate in Heavily Pretreated Patients with Chronic Myeloid Leukemia

AbstractAbstract 4433 BackgroundSubcutaneous omacetaxine mepesuccinate (“omacetaxine”) is an investigational, first-in-class cephalotaxine and is a protein synthesis inhibitor that does not depend on direct binding of Bcr-Abl. Omacetaxine reduces levels of multiple oncoproteins, including Bcr-Abl, and induces apoptosis in leukemic stem cells by blocking the initial step of protein translation at the level of the ribosome. Omacetaxine has shown clinical activity and adequate tolerability in two phase 2, open-label, international, multicenter studies in patients with chronic myeloid leukemia (CML). Patients with a history of the T315I mutation who failed prior imatinib were enrolled in the first study (CML202). Patients were enrolled in the second study (CML203) if they had resistance or intolerance to ≥2 tyrosine kinase inhibitors (TKIs). Point mutations occur frequently in CML patients who develop resistance to imatinib. This is a post hoc analysis of responses to omacetaxine in patients with any phase CML by mutational status. MethodsData from patients with CML in chronic phase (CP), accelerated phase (AP), or blast phase (BP) were included from the two phase 2 studies. Omacetaxine 1.25 mg/m2was administered subcutaneously twice daily for 14 consecutive days every 28 days for induction and the same dosage for 7 days every 28 days as maintenance. An exploratory analysis was conducted to elucidate associations between mutation status and complete hematologic response (CHR) or major cytogenetic response (MCyR) following omacetaxine treatment. ResultsAmong CP, AP, and BP patients, grade 3/4 hematologic toxicities were thrombocytopenia (in 89/105, 43/49, and 43/44 patients, respectively), neutropenia (86/106, 35/49, 36/44), leukopenia (76/106, 30/49, 29/44), and anemia (66/107, 39/49, 36/44). Common grade 3/4 nonhematologic adverse events included fatigue (5/108, 5/51, and 2/44 patients, respectively) and pneumonia (3/108, 4/51, and 2/44). Seventy-six deaths occurred during long-term follow-up (33, 24, 19); 8 were treatment-related (5, 2, 1), most commonly due to sepsis (n=3).The pooled baseline mutational analysis included 203 CML patients (108 CP, 51 AP, and 44 BP). Unknown mutations were noted in 24%, 25%, and 32% of CP, AP and BP patients, respectively. Mutations were identified in 52%, 51%, and 52% while no mutation status was recorded for 24%, 25%, and 16% of CP, AP, and BP patients, respectively. T315I was the most frequently identified mutation (Table), occurring in 36%, 24%, and 39% of patients, respectively. Multiple mutations, which include individual mutations listed separately, were detected in 12% CP, 14% AP, and 7% BP patients.Among patients with CP or AP CML, CHR rate was high in the presence of the T315I mutation. MCyR rates for CP patients were similar for patients with or without mutations but appeared to be relatively lower among patients with multiple mutations. Among AP patients, MCyR only occurred in those without mutations. ConclusionsPoint mutations, particularly T315I, were common in this heavily treated population of CML patients although T315I may be overrepresented due to CML202 inclusion criteria. Efficacy of omacetaxine, as measured by rates of CHR and MCyR, appeared to be largely independent of the presence or absence of point mutations. However, interpretation of these results is limited by small sample sizes in many of the groups.Support: Teva Pharmaceutical Industries Ltd.TableResponse Rates by Mutation and CML PhasePoint Mutations, n Responders/n with Mutation (%)CP (n=108)AP (n=51)BP (n=44)CHRMCyRCHRMCyRCHRMCyRNo mutation17/26 (65)5/26 (19)4/13 (31)2/13 (15)0/70/7Unknown status18/26 (69)6/26 (23)4/12 (33)0/122/14 (14)0/14Any mutation44/56 (79)13/56 (23)7/26 (27)0/261/23 (4)0/23T315I32/39 (82)10/39 (26)5/12 (42)0/120/170/17F317I/L3/5 (60)0/50/30/30/20/2G250E1/3 (33)0/32/5 (40)0/50/00/0V299L2/3 (67)1/3 (33)1/2 (50)0/20/00/0F359V/C4/6 (67)3/6 (50)0/00/00/10/1Multiple mutations (including those above)8/13 (62)2/13 (15)2/7 (29)0/70/30/3 Disclosures:Off Label Use: Subcutaneous omacetaxine mepesuccinate (“omacetaxine”) is a protein synthesis inhibitor that does not depend on direct binding of Bcr-Abl. Omacetaxine has shown clinical activity in 2 studies of chronic myeloid leukemia (CML), one in patients with a history of the T315I Bcr-Abl mutation and the other in patients failing at least 2 tyrosine kinase inhibitors. Nicolini:BMS: Research Funding, Speakers Bureau; Ariad: Consultancy, Speakers Bureau; Pfizer: Consultancy; Novartis: Consultancy, Research Funding, Speakers Bureau; Teva: Speakers Bureau. Wetzler:BMS: Research Funding; Teva: Membership on an entity’s Board of Directors or advisory committees. Akard:Celgene: Research Funding, Speakers Bureau; Millenium: Speakers Bureau; Eisai: Speakers Bureau; Pfizer: Research Funding; Merck: Research Funding; Ariad: Research Funding; Teva: Research Funding; Bristol-Myers Squibb: Research Funding, Speakers Bureau; Novartis: Research Funding, Speakers Bureau. Baccarani:Teva: Research Funding. Kantarjian:ChemGenex (Teva): Research Funding. Craig:Teva: Consultancy. Cortes:Chemgenex (Teva): Consultancy, Research Funding; Ariad: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding; BMS: Consultancy, Research Funding; Deciphera: Research Funding.

Health Related Quality of Life of Bosutinib in Imatinib-Resistant or Imatinib-Intolerant Patients with Advanced Chronic Myeloid Leukemia

Abstract 4448 Purpose:Bosutinib is a dual Src/Abl tyrosine kinase inhibitor (TKI), which has demonstrated efficacy in a phase I/II study of patients with Advanced Phase Chronic Myeloid Leukemia (CML). The objective was to evaluate the effect of bosutinib on health -related quality of life (HRQoL) in patients with advanced CML after failure with imatinib. Methods:Patient reported HRQoL was an exploratory objective in the clinical trial and measured using the 44-item Functional Assessment of Cancer Therapy-Leukemia (FACT-Leu). The FACT-Leu is a modular approach to assess patient HRQoL using a core set of general cancer questions as well as a cancer site specific leukemia subscale with 5 domains: Social Well-being (SWB), Emotional Well-being (EWB), Physical Well-being (PWB), Functional Well-being (FWB) and Leukemia Subscale (LeuS); and 3 summary scales: FACT-General, FACT Trial Outcome Index (TOI) and FACT-Leu Total. The item responses for each scale are summed to provide scores; higher scores indicate better HRQoL. The FACT-Leu was completed at weeks 4, 8, 12 and every 12 weeks thereafter, as well as treatment completion. Within cohort comparisons were assessed using paired t-tests. Results:Of the 164 patients with advanced leukemia included in the trial, 76 had accelerated phase (AP) CML and 64 blast phase (BP) CML. At 24 weeks, AP patients reported statistically significant improvements in PWB (p=0.02), EWB (p<0.001), LeuS (p<0.001), FACT-G (p<0.001), FACT-Leu (p<0.001) and FACT-TOI (p<0.001) with the PWB, FACT-G, LeuS, TOI and FACT-Leu exceeding minimally important differences (MID) at 24 weeks. Blast phase patients reported significant improvements in PWB (p=0.02), EWB (p=0.02), FWB (p=0.04), LeuS (p=0.01), FACT-G (p<0.001), FACT-Leu (p<0.001) and FACT-TOI (p=0.01) at 24-weeks with all scales exceeding MID except the SWB. At 48-weeks the AP patients continued to have statistically significant improvements in PWB (p=0.05), EWB (p=0.02), and FACT-G (p=0.03) and PWB, FACT-G, TOI and FACT-Leu exceeded the MID at 48 weeks. There were no statistically significant deteriorations in HRQoL through week 48 (Figure 1) Conclusions:These data suggest that CML patients treated with bosutinib demonstrate improved HRQoL. Confirmation in a controlled study is needed. [Display omitted] Disclosures:Whiteley:Pfizer Inc: Employment, Equity Ownership. Reisman:Pfizer Inc: Employment, Equity Ownership. Kelly:Pfizer Inc: Employment, Equity Ownership. Cortes:Novartis, Bristol Myers Squibb, Pfizer, Ariad, Chemgenex: Consultancy, Research Funding. Cella:Pfizer Inc: Honoraria, Research Funding.

“Stem cell transplantation: its importance today”

Allogeneic stem cell transplantation (SCT) had traditionally been the first-line therapy of chronic myeloid leukaemia (CML), but the introduction of tyrosine kinase inhibitors (TKI) has caused a major change to the treatment algorithm. The majority of patients in chronic phase obtain an excellent response to these oral agents with minimal toxicity. SCT is therefore used only in a minority of patients who do not achieve adequate response to first-, second- or even third-generation agents. Patients in accelerated phase are less likely to achieve an optimal response and for patients in blast phase, SCT continues to be the only therapy with curative potential although it is now increasingly used in combination with TKI. This review discusses the place of SCT in the current therapy of CML.

Prognostic factors for outcomes in allogeneic transplantation for CML in the imatinib era: a CIBMTR analysis

Allogeneic hematopoietic stem cell transplantation (HSCT) is curative treatment, albeit in a minority of patients with accelerated (AP) or blast phase (BP) chronic myeloid leukemia (CML). Imatinib (IM) has transient but significant activity in advanced phases of CML, which may permit early allografting for responding patients. To identify prognostic factors in allograft recipients previously treated with IM, we analyzed 449 allogeneic HSCT performed between 1999–2004 in advanced phase CML using data reported to the Center for International Blood and Marrow Transplant Research. CML patients in second chronic phase (CP2, n=184), AP (n=185), and BP (n=80) received HLA-identical sibling (27%), related (3%), or matched or mismatched unrelated donor (70%), peripheral blood (47%) or bone marrow (53%) HSCT after myeloablative (78%) or non-myeloablative (22%) conditioning. 52% in CP2, 49% in AP, and 46% in BP received IM pre-HSCT. Disease-free survival was 35–40% for CP2, 26–27% for AP and 8–11% for BP. Cumulative incidence of acute and chronic GVHD and TRM were not affected by stages of CML or pre-HSCT IM exposure. Multivariate analyses showed that conventional prognostic indicators remain the strongest determinants of transplant outcomes. In conclusion, there are no new prognostic indicators of outcomes of allogeneic HSCT for advanced phase CML in the IM era.

Increased expression of protease-activated receptor 1 (PAR-1) in human leukemias

Protease-activated receptor 1 (PAR-1) is a G-protein-coupled receptor that is overexpressed in solid tumors, being associated with several pro-tumoral responses including primary growth, invasion, metastasis and angiogenesis. Expression of PAR-1 in human leukemic cell lines is reported but the status of its expression in human leukemic patients is currently unknown. In this study we evaluated the expression pattern of PAR-1 in patients with the four main types of leukemia – chronic lymphocytic leukemia subtype B (B-CLL), acute lymphoblastic leukemia subtype B (B-ALL), acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). Flow cytometry analyses show that lymphocytes from B-CLL patients express this receptor at similar levels to healthy individuals. On the other hand, it was observed a significant increase in PAR-1 expression in B-ALL lymphocytes as compared to B-CLL and healthy donors. Flow cytometric and real-time PCR demonstrated a significant increase in PAR-1 expression in granulocytes from CML patients in blast phase (CML-BP) but not in chronic phase (CML-CP) as compared to healthy donors. Finally, a significant increase in PAR-1 expression has been also observed in blasts from AML (subtypes M4 and M5) patients, as compared to monocytes or granulocytes from healthy donors. We conclude that PAR-1 might play an important biological role in aggressive leukemias and might offer additional strategies for the development of new therapies.

2 Resistance to targeted therapy: mechanisms and therapeutic implications

Ponatinib is a third generation tyrosine kinase inhibitor (TKI) active against wild type and mutant bcr/abl tyrosine kinase (including T315I). Ponatinib is approved for the treatment of adult patients with T315I mutation detected in CML (all phases) and in Ph+ ALL, for CML patients who are resistant to dasatinib or nilotinib and patients with Ph+ ALL who are intolerant or resistant to dasatinib and for whom subsequent imatinib treatment is not an optimal therapy. In phase II registration study (PACE), 267 patients with CML in chronic phase (CP), 83 in accelerated (AC) and 94 patients in blastic phase (BP) of CML or Ph+ALL were enrolled. T315I mutation was detected in 64, 18 and 46 patients, respectively. Two or more or three or more TKIs were used before ponatinib in 93% and 58% of patients, respectively for median period of 16.7 months. Major cytogenetic response (MCyR) by 12 months was achieved in 59% of CP CML patients (median follow-up 36 months), and major hematological response (MaHR) by 6 months in 55% of AC CML patients, and in 34% of BP CML and Ph+ALL patients (median follow-up 15.16 and 6 months, respectively). Efficacy of ponatinib as a first-line treatment for CP CML patients was shown in phase II and III trials. Serious adverse reactions have been reported with ponatinib, including vascular occlusion, heart failure and hepatotoxicity. Ponatinib is a valuable treatment option for patients with CML and Ph+ALL resistant or intolerant to previous therapy with TKIs and those with T315I mutation.

Inhibition of IGF‐IR tyrosine kinase induces apoptosis and cell cycle arrest in imatinib‐resistant chronic myeloid leukaemia cells

Although signalling through the type I insulin-like growth factor receptor (IGF-IR) maintains the survival of haematopoietic cells, a specific role of IGF-IR in haematological neoplasms remains largely unknown. Chronic myeloid leukaemia (CML) is the most common subtype of chronic myeloproliferative diseases. Typically, CML evolves as a chronic phase (CP) disease that progresses into accelerated (AP) and blast phase (BP) stages. In this study, we show that IGF-IR is universally expressed in four CML cell lines. IGF-IR was expressed in only 30% and 25% of CP and AP patients, respectively, but its frequency of expression increased to 73% of BP patients. Increased expression levels of IGF-IR with CML progression was supported by quantitative real-time PCR that demonstrated significantly higher levels of IGF-IR mRNA in BP patients. Inhibition of IGF-IR decreased the viability and proliferation of CML cell lines and abrogated their growth in soft agar. Importantly, inhibition of IGF-IR decreased the viability of cells resistant to imatinib mesylate including BaF3 cells transfected with p210 BCR-ABL mutants, CML cell lines and primary neoplastic cells from patients. The negative effects of inhibition of IGF-IR were attributable to apoptosis and cell cycle arrest due to alterations of downstream target proteins. Our findings suggest that IGF-IR could represent a potential molecular target particularly for advanced stage or imatinib-resistant cases.

The Oncogenic Role of Tumor Suppressor Protein p27 in Ph+ Chronic Myeloid Leukemia.

Abstract 3276Poster Board III-1 Background:Several studies have indicated that BCR-ABL causes cell cycle defects by interfering with the cell cycle regulatory functions of p27, a Cyclin dependent kinase (Cdk) inhibitor and tumor suppressor. Studies in BCR-ABL positive cell lines have shown that BCR-ABL promotes proteasomal degradation of p27 in a pathway that involves the SCFSKP2 ubiquitin ligase, while cytoplasmic mislocalization has been described in primary CML cells. It has been suggested that the principal effect of this cytoplasmic mislocalization is to remove p27 from the nucleus, thereby relieving Cdks from p27 inhibition. However, recent studies have shown that a p27 mutant (p27CK-), that cannot bind to Cdks or Cyclins, actively contributes to oncogenesis. This raises the question as to whether cytoplasmic mislocalization of p27 in CML cells may in fact promote leukemogenesis rather than merely compromise Cdk inhibition. We therefore hypothesized that the net contribution of p27 in CML is to promote leukemogenesis due to the oncogenic activity of cytoplasmic p27. Experimental approach and results:We determined p27 localization in BCR-ABL positive cell lines and CD34+ progenitor cells from newly diagnosed chronic phase CML patients (N=7) and from CML patients in blast crisis (N=2) by immunoblotting of nuclear and cytoplasmic cellular fractions. We found that p27 is predominantly cytoplasmic in most CML cell lines and in CD34+ cells from 8/9 (89%) patient samples, including patients in blastic phase. Cytoplasmic localization of p27 in CD34+ cells from CML patients was also confirmed by immunofluorescence analysis. Further, we observed that inhibition of BCR-ABL kinase by imatinib, an Abl kinase inhibitor increased nuclear p27 in all cell lines tested and in 4/9 patient samples (3/7 chronic phase and 1/2 blastic phase samples). However, we did not observe a substantial change in the cytoplasmic p27 levels. Similar results were obtained in Ba/F3 and 32D murine hematopoietic cell lines expressing BCR-ABL when compared with the respective parental cells. Further, SKP2 was up-regulated in CD34+ cell from CML patients as compared to the normal patients consistent withSKP2 mediated down-regulation of nuclear p27. These data suggest that nuclear but not cytoplasmic p27 levels are predominantly regulated by BCR-ABL kinase activity. To test whether p27 is crucial for BCR-ABL-driven leukemia, we compared leukemogenesis between recipients of BCR-ABL transduced p27+/+ and p27-/- bone marrow. Mice transplanted with BCR-ABL infected p27-/- marrow had significantly longer median survival (70 days, range 48-150 days) compared to recipients of p27+/+ marrow (37 days, range 14-56 days) (p=0.0123). To exclude that this difference was related to the differences in homing and engraftment capabilities of p27+/+ and p27-/- bone marrow cells, we compared short term homing and long term engraftment of p27+/+ and p27-/- bone marrow cells transplanted into wild-type recipients and found no differences. These data suggest that the net contribution of p27 to BCR-ABL-mediated leukemogenesis is positive. Further, to investigate the contribution of nuclear p27 to leukemogenesis, we utilized marrow from p27S10A mice in the murine CML model. In p27S10A mice, p27 is nuclear to to abrogation of the phosphorylation site implicated in nuclear export. We injected BCR-ABL transduced bone marrow cells of p27S10A and p27+/+ mice into wild-type recipients and compared the disease progression. We observed that mice transplanted with BCR-ABL infected p27S10A marrow had significantly longer median survival (28 days, range 23-79 days) compared to the recipients of p27+/+ marrow (23 days, range 21-38 days) (p=0.0139). This data is consistent with nuclear tumor suppressor function of p27. Combined with the data above, this suggests that cytoplasmic p27 promotes BCR-ABL mediated leukemogenesis. Conclusions:Our data suggest that though nuclear p27 functions as a tumor suppressor, the net contribution of p27 in CML might be oncogenic due to an oncogenic role of the increased cytoplasmic p27. Restoring nuclear p27 or reducing cytoplasmic p27 may be therapeutically useful in malignancies with low nuclear and high cytoplasmic p27 expression. Disclosures:Druker:OHSU patent #843 - Mutate ABL Kinase Domains: Patents & Royalties; MolecularMD: Equity Ownership; Roche: Consultancy; Cylene Pharmaceuticals: Consultancy; Calistoga Pharmaceuticals: Consultancy; Avalon Pharmaceuticals: Consultancy; Ambit Biosciences: Consultancy; Millipore via Dana-Farber Cancer Institute: Patents & Royalties; Novartis, ARIAD, Bristol-Myers Squibb: Research Funding. Deininger:Genzyme: Research Funding; BMS: Consultancy; Novartis: Consultancy, Honoraria; Ariad : Research Funding.

Chronic myeloid leukemia (CML) with P190BCR-ABL: analysis of characteristics, outcomes, and prognostic significance

AbstractThe most common BCR-ABL transcripts in chronic myeloid leukemia (CML) are e13a2(b2a2) and e14a2(b3a2). Other transcripts such as e1a2 are rare and their outcome with tyrosine kinase inhibitors (TKI) therapy is undefined. We analyzed 1292 CML patients and identified 14 with only e1a2 transcripts, 9 in chronic phase (CP), 1 in accelerated phase (AP), and 4 in blast phase (BP). Of the CP, 4 achieved complete hematologic response (CHR); 2, complete cytogenetic response (CCyR); 2, partial cytogenetic response (PCyR), and 1 did not respond to imatinib. Five patients progressed to myeloid BP (3), lymphoid BP (1), or AP (1). The AP patient received various TKIs sequentially and achieved only CHR. BP patients received hyper-CVAD (hyperfractionated cyclophosphamide, vincristine, adriamycin, dexamethasone) plus imatinib/dasatinib or idarubicin plus cytarabine (Ara-C); 2 did not respond, 1 had CCyR, and 1 short-lasting complete molecular response (CMR). Overall, cytogenetic responses lasted 3 to 18 months; only 2 achieved major molecular response (MMR) on TKI. P190BCR-ABL CML is rare and is associated with an inferior outcome to therapy with TKI. These patients need to be identified as high-risk patients.

Chronic myeloid leukemia (CML) with e1a2 BCR-ABL fusion transcript type: Analysis of characteristics, outcomes, and prognostic significance

7030 Background: The most common BCR-ABL fusion transcripts in CML are e13a2 (b2a2) and e14a2 (b3a2). Rarely, other transcripts like e1a2 are seen. Currently, there is no published series of data on efficacy of imatinib or other tyrosine kinase inhibitors (TKIs) in CML with e1a2. Methods: We analyzed records of 1,292 CML patients treated with TKI at our institution between January 2000 and November 2008. Results: 14 CML patients with e1a2 transcripts were identified, 9 in chronic phase (CP), 1 in accelerated phase (AP), and 4 in blast phase (BP). Median age at diagnosis was 60 (range 28–86) years, median follow-up 39.5 (range 2–109) months. Of the 9 in CP, 3 received interferon and then imatinib after interferon failure, 6 received TKI as first-line therapy (5 imatinib, 1 nilotinib): 5 achieved CHR only, 1 CCyR, 1 MCyR, 1 PCyR, and 1 did not respond to imatinib. 5 patients (2 post-interferon failure - 1 in CHR, 1 in PCyR; 3 frontline imatinib - 1 in CHR, 1 in CCyR, 1 non-responder) progressed to advanced phases (3 myeloid BP, 1 lymphoid BP, 1 AP) at a median 48 (range 4–92) months after CML diagnosis; with only 1 alive and in CMR after allogeneic SCT. AP patient received various TKIs sequentially and achieved only CHR with disappearance of clonal evolution. BP patients received Hyper-CVAD+imatinib/dasatinib or idarubicin+Ara-C; 2 did not respond, 1 had CCyR lasting 12 months with Hyper-CVAD+Imatinib and 1 had CMR after allogeneic SCT lasting 2 months. In all 14 patients, cytogenetic responses lasted 1–9 months before being lost and none (except 2) achieved MMR or CMR on imatinib or other TKI therapy. Six patients (5 CP, 1 AP) were alive at a median 39 (range 2–85) months after initial diagnosis: 4 with CHR (2 on imatinib, 1 nilotinib, 1 bosutinib), 1 with MCyR on imatinib, and 1 with CMR after allogeneic SCT. Conclusions: CML with e1a2 BCR-ABL fusion transcripts is rare and is associated with an inferior outcome to therapy with TKI, with responses being usually short-lived. These patients need to be identified as high-risk patients and monitored closely for efficacy during therapy with TKI. No significant financial relationships to disclose.

Characterisation of extramedullary relapse in patients with chronic myeloid leukemia in advanced disease after allogeneic stem cell transplantation

Recently, higher extramedullary relapse rates following allogeneic stem cell transplantation (SCT) in myeloid malignancies were reported e.g. because of selection of poor-risk patients. We analysed five consecutive patients with post-transplant extramedullary relapse of chronic myeloid leukemia (CML) out of a total of 24 patients (21%) undergoing allo-SCT. All five patients with extramedullary relapse had clonal evolution and a history of blast phase (BP). In particular, 56% of the patients in BP had extramedullary relapse with no extramedullary relapse in patients with chronic/accelerated phase. Most frequent manifestation sites were the skeletal system, the muscles/subcutaneous tissue and the central nervous system. In one case chloroma was mimicking myositis of the lower limbs. Combined approaches were performed including irradiation (n = 4), chemotherapy (n = 2), IM (n = 2), dasatinib (n = 4), nilotinib (n = 1), a novel aurora-kinase-inhibitor (n = 1), donor lymphocytes (n = 2) or a second allo-SCT (n = 2). Transient response was achieved in one case, stable partial remissions in two cases, whereas two cases were refractory. Research should focus on prospective studies aiming to improve treatment of extramedullary relapse in stem cell recipients with CML with a special focus on the role of second generation tyrosine kinase inhibitors.

Safety and Efficacy of Subcutaneous (SC) Omacetaxine Mepesuccinate in Imatinib(IM)-Resistant Chronic Myeloid Leukemia (CML) Patients (pts) with the T315I Mutation – Results of An Ongoing Multicenter Phase II Study.

Background: Omacetaxine (homoharringtonine, HHT) shows clinical activity against Ph+ CML, with a mechanism of action independent of tyrosine kinase inhibition. Currently available tyrosine kinase inhibitors (TKIs) have not demonstrated activity in CML pts harboring the T315I BCR-ABL mutation.Study Goals: To evaluate the safety and efficacy of omacetaxine in pts with IM-resistant T315I+ Ph+ CML.Methods: Eligible pts include adult CML with confirmed T315I BCR-ABL mutation following imatinib failure after informed consent. Presence of T315I mutation is confirmed at one of 2 central reference labs. Induction schedule consists of 1.25 mg/m2 omacetaxine SC twice daily for 14 days every 28 days until complete hematologic response (CHR) or hematologic improvement (HI). Maintenance schedule may start after at least one induction cycle and after initial hematologic response. Maintenance treatment consists of 1.25 mg/m2 OMA SC twice daily for 7 days every 28 days, for up to 24 months.Study Results: To date, 50 pts have been enrolled, all having failed prior imatinib therapy, and 82% having failed 2 or more prior TKIs. Enrollment includes 26 pts in chronic phase (CP), 13 in accelerated phase (AP) and 11 in myeloid blast phase (BP). Median age: 58 yrs (19–84), 70% male. Mean baseline WBC values (/μl) were 11.51 (range 1.9–23.76) in CP, 18.88 (range 3.6– 78.2) in AP and 16.58 (range 2.4–51.5) in BP patients. Median disease duration is 58 months (range 5–285).Efficacy: Data are available for 30 pts: 15 CP, 10 AP and 6 BP pts. In CP pts, CHR has been achieved in 80% (12/15) with a median duration of response of 8 months (range 2.7 to 13.5+). Of these 12 pts achieving CHR, 11 pts continue on study with the remaining patient achieving complete cytogenetic response (CCyR) and being removed from treatment to receive allograft transplantation. The median time to hematologic response was 1.2 months (range 0.6 to 2.5). Overall cytogenetic response in CP pts is 20% (3/15) with 13% (2/15) achieving CCyR and 1 pt achieving a minimal cytogenetic reponse. Median duration of cytogenetic response is 9.1 months (range 7.1 to 9.2+) with one pt continuing in CCyR and the second patient receiving allograft as described above. In AP pts, overall hematologic response is 60% (6/10) with 5 of these patients remaining active in treatment. Two pts have achieved CHR, 3 returned to chronic phase and 1 showed HI. Median duration of response was 2.2 months (range 1 to 4.4+). Overall cytogenetic response rate in AP patients is 21% (3/14), with 2 pts achieving major cytogenetic response and 1 pt achieving minimal response. In BP patients, overall hematologic response rate is 33% (2/6) with 1 pt achieving CHR and 1 HI. Duration of response was 3.7 and 3.9 months respectively. The T315I mutated clone has been decreased below the limit of detection in 60% of evaluable patients.Safety: Data are available for 32 pts enrolled in all disease phases. The primary toxicity being myelosuppression which is reversible and managed by adjusting the number of dosing days received per cycle. Incidence of treatment emergent grade 3/4 events includes: thrombocytopenia 44%, neutropenia 34%, anemia 28%, febrile neutropenia 16%, and pancytopenia 9.4%. Injection site reactions have been mild with no grade 3–4 events reported. Four pts have died (3 BP, 1 AP) during the study period, all due to disease progression.Conclusions: Omacetaxine therapy in T315I mutated BCRABL+ IM-resistant CML is well tolerated and is producing durable CHRs and cytogenetic responses in these patients.

Successful Use of National Cancer Registry Data to Monitor the Effective Use of Imatinib for Treating Chronic Myeloid Leukaemia

Imatinib is a tyrosine kinase inhibitor, which selectively antagonises the BCR-ABL molecular pathway which causes chronic myeloid leukaemia (CML). Imatinib was first approved by the Scottish Medicines Consortium (SMC) in January 2002 with the recommendation that its use be audited. The cost of the drug has major financial implications for health resources. All imatinib usage since its first prescription in Scotland in September 2000 to July 2003 was audited through pharmacy records and through the Scotland Leukaemia Registry (SLR), an existing national registry of patients with CML. One hundred and four patients in Chronic Phase (CP), 36 in Accelerated Phase (AP) and five in Blast Phase (BP) received imatinib. The median duration of therapy was not reached for CFP 17 months for AFP and two months for BP patients. Major (complete) cytogenetic response rates were 74% (63%) and 38% (24%) respectively for CP and APR Overall survival for all CP patients from the start of imatinib therapy was 94% at one year, 91% at two years and 83% at three years. An audit of the effectiveness of the SLR as an auditing agency, showed complete registration in 95% of cases. We believe such data collection should be an important ongoing resource for assessing outcomes in a rare form of leukaemia but one which already has major implications for health economics and will continue to do so given the future development of dual tyrosine kinase inhibitors for imatinib resistant cases.

Upregulation of CXCR4 Is Essential for the Migration and Survival of Quiescent CML Progenitor Cells in the Bone Marrow Microenvironment after Imatinib Treatment.

Chronic myeloid leukemia (CML) is driven by constitutively activated Bcr-Abl tyrosine kinase, which causes the defective adhesion of CML cells to bone marrow (BM) stroma. The overexpression of p210Bcr-Abl was reported to down-regulate CXCR4 expression, resulting in cell migration defects in CML. We proposed that the tyrosine kinase inhibitors imatinib or INNO-406 may restore CXCR4 expression and cause the migration of CML cells to BM microenvironment niches which results in acquisition of stroma-mediated chemoresistance of CML progenitor cells. In KBM5 and K562 cells, imatinib or INNO-406 increased CXCR4 expression and migration. Imatinib induced a G0/1 cell cycle block in CML cells, which was further enhanced in a bone marrow-derived stromal cell (MSC) co-culture system. Quiescent KBM5 cells migrating to stromal cells were resistant to Imatinib-induced cell death. These anti-apoptotic effects were abrogated by inhibition of CXCR4 (AMD3465) or Integrin-linked kinase (QLT0267). BM CD34+ cells from newly diagnosed (n=15) or blast crisis CML patients (n=5) expressed markedly lower CXCR4 levels compared with normal CD34+ BM progenitor cells (n=12) (p<0.05), and was associated with deficient migration of CD34+ CML cells. A longitudinal analysis of peripheral blood samples from CML patients in blast crisis treated with imatinib (n=5) revealed induction of CXCR4 in peripheral blood CD34+ progenitor cells within the first few days after initiation of treatment, which coincided with decreased WBC and absolute blast counts. After prolonged (3–10 day) exposure to imatinib, however, CXCR4 levels of CD34+ PB CML cells decreased, frequently below the starting levels. CXCR4 immunostaining on blasts/immature cells in BM biopsy sections from patients demonstrated that 5 of 7 patient samples were CXCR4-negative prior to imatinib therapy; 4 of these 5 became CXCR4 positive after imatinib treatment. While patients in blast-phase had short-lived hematologic responses to imatinib, Ph+ clone remained predominant in the bone marrow, and all patients ultimately relapsed with recurrence of blasts in the BM. Altogether, these findings suggest that the up-regulation of CXCR4 by imatinib promotes migration of CML cells to BM stroma, causing G0/1 cell-cycle arrest and enhancing the survival of quiescent CML progenitor cells within bone marrow microenvironment. This provides the rationale for interfering with the protective effects of BM stroma cells by inhibiting CXCR4 and/or integrin signaling, which could be of benefit in eradicating residual quiescent CML cells.