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Background: Most patients with myelofibrosis develop ruxolitinib intolerance or disease that is relapsed or refractory, and survival rates after ruxolitinib discontinuation are poor. We aimed to evaluate the safety and efficacy of fedratinib versus best available therapy (BAT) in patients with myelofibrosis previously treated with ruxolitinib., Methods: FREEDOM2 was a multicentre, open-label, randomised, controlled, phase 3 trial in 86 clinics in 16 countries, in which patients aged at least 18 years with intermediate-2 or high-risk myelofibrosis that was relapsed or refractory or intolerant to ruxolitinib with Eastern Cooperative Oncology Group performance status 0-2 were stratified by spleen size by palpation, platelet count, and previous ruxolitinib treatment, and randomly assigned 2:1 by interactive response technology to receive fedratinib 400 mg per day (4 × 100 mg capsules orally once daily, open-label) or BAT. Patients received prophylactic antiemetics and thiamine supplementation, and symptomatic antidiarrhoeals as required. Primary endpoint was proportion of patients reaching spleen volume reduction (SVR) of at least 35% (SVR35) at end of cycle 6 in the intention-to-treat population. This manuscript reports the primary analysis of the trial; follow-up is ongoing. This trial is registered at clinicaltrials.gov, NCT03952039., Findings: Between Sept 9, 2019 and June 24, 2022, of 316 patients screened, 201 were randomly assigned and treated (134 to fedratinib, 67 to BAT [including 52 receiving ruxolitinib]); 46 patients from the BAT group crossed over to fedratinib. Approximately half of enrolled patients were male (fedratinib 75 [56%] of 134; BAT 30 [45%] of 67) and most were White (fedratinib 106 [79%] of 134; BAT 58 [87%] of 67). At data cutoff (Dec 27, 2022), median survival follow-up was 64·5 weeks (IQR 37·9-104·9). SVR35 at end of cycle 6 was seen in 48 (36%) of 134 patients receiving fedratinib versus four (6%) of 67 patients receiving BAT (30% difference; 95% CI 20-39; one-sided p-value <0·0001). During the first six cycles 53 (40%) of 134 patients in the fedratinib group and 8 (12%) of 67 patients in the BAT group had grade 3 or greater treatment-related adverse events, most frequently anaemia (fedratinib 12 [9%] of 134; BAT 6 [9%] of 67) and thrombocytopenia (fedratinib 16 [12%] of 134; BAT 2 [3%] of 67); one patient in the fedratinib group died from acute kidney injury suspected to be related to study drug (no treatment-related deaths in the BAT group). Gastrointestinal adverse events occurred more frequently in the fedratinib group compared with the BAT group, but were mostly grade 1-2 in severity and more frequent in early cycles, and were less frequent than in prior clinical trials. A total of 28 (21%) of 134 patients in the fedratinib group and 3 (4%) of 67 patients in the BAT group had thiamine levels below lower limit of normal per central laboratory assessment, with only one case of low thiamine in the fedratinib arm after the introduction of prophylactic thiamine supplementation., Interpretation: Findings from FREEDOM2 support fedratinib as a second-line Janus kinase inhibitor option to reduce spleen size after ruxolitinib failure or intolerance in patients with myelofibrosis, and shows effective strategies for management of gastrointestinal adverse events and low thiamine concentrations through prophylaxis, monitoring, and treatment., Funding: Bristol Myers Squibb., Competing Interests: Declaration of interests CNH reports research funding from Bristol Myers Squibb, Constellation–Morphosys, and Novartis; consulting fees from Galecto, Geron, and GlaxoSmithKline; honoraria from AbbVie, AOP Health, Bristol Myers Squibb–Celgene, CTI BioPharma, Galacteo, Geron, Gilead, IMAGO, Janssen, Keros, Novartis, Promedior, Roche, Shire, and Sierra; participation on a data safety monitoring board or advisory board with Galacteo and Keros; and leadership at the European Hematology Association. RM reports honoraria from AbbVie, Blueprint, Bristol Myers Squibb, CTI BioPharma, Genentech, Geron, GlaxoSmithKline, Incyte, Morphosys, Novartis, Sierra Oncology, and Telios. MT reports research funding from Bristol Myers Squibb; travel support from Sumitomo; participation on a data safety monitoring board or advisory board with Bristol Myers Squibb, Novartis, and Sumitomo; and leadership in the Society of Hematologic Oncology. HKA-A reports research funding from Bristol Myers Squibb, Incyte, and Novartis; travel support from AbbVie and Bristol Myers Squibb; and participation on a data safety monitoring board or advisory board with AbbVie, AOP Health, Blueprint, Bristol Myers Squibb, Novartis, and SGK. FPas reports research funding from Bristol Myers Squibb–Celgene; consulting fees from AbbVie, AOP Health, Bristol Myers Squibb–Celgene, Kartos, Karyopharma, Kyowa Kirin–MEI, Novartis, Roche, Sierra Oncology, and Sumitomo; and honoraria from AbbVie, AOP Health, Bristol Myers Squibb–Celgene, Novartis, and Roche. FPal reports research funding from Bristol Myers Squibb; honoraria from AbbVie, Amgen, AOP Health, Bristol Myers Squibb, CTI BioPharma, GlaxoSmithKline, Kartos, Novartis, and Telios; travel support from AbbVie and Novartis; and participation on a data safety monitoring board or advisory board with AbbVie, AOP Health, Bristol Myers Squibb, CTI BioPharma, GlaxoSmithKline, and Novartis. GB reports honoraria and participation on a data safety monitoring board or advisory board with Bristol Myers Squibb, Janssen, and Novartis. AMV reports honoraria from AbbVie, Bristol Myers Squibb, Geron, GlaxoSmithKline, Incyte, and Novartis; and participation on a data safety monitoring board or advisory board with Bristol Myers Squibb, Geron, Incyte, and Novartis. CM reports research funding from AbbVie and Bristol Myers Squibb; and honoraria from AbbVie, Bristol Myers Squibb, and Novartis. AI reports honoraria from Bristol Myers Squibb, GlaxoSmithKline, Incyte, Novartis, and Pfizer; and participation on a data safety monitoring board or advisory board with AOP Health, Bristol Myers Squibb, Incyte, Novartis, and Pfizer. PB reports employment and stock or stock options with Bristol Myers Squibb. CH reports employment with Bristol Myers Squibb. SR reports employment and stock or stock options with Bristol Myers Squibb. JW reports employment with Bristol Myers Squibb. J-JK reports consulting fees from AbbVie and GlaxoSmithKline; honoraria from AOP Health and Novartis; and participation on a data safety monitoring board or advisory board with Bristol Myers Squibb and Incyte. BX and IK report no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

The phase 3b FREEDOM trial (ClinicalTrials.gov: NCT03755518) evaluates efficacy/safety of fedratinib in intermediate- or high-risk myelofibrosis patients with platelet count ≥50 × 10 9 /L, previously treated with ruxolitinib. The trial design included protocol specified strategies to mitigate the risk for gastrointestinal (GI) adverse events (AEs), thiamine supplementation, and encephalopathy surveillance. Due to COVID-19, accrual was cut short with 38 patients enrolled. In the efficacy evaluable population ( n  = 35), nine (25.7%; 95% confidence interval 12.5-43.3) patients achieved primary endpoint of ≥35% spleen volume reduction (SVR) at end of cycle (EOC) 6; and 22 (62.9%) patients showed best overall response of ≥35% SVR up to end of treatment. Sixteen (44.4%) patients showed ≥50% reduction in total symptom score at EOC6 ( n  = 36). Compared to previously reported JAKARTA-2 trial, rates of GI AEs were lower, and no patient developed encephalopathy. Overall, FREEDOM study showed clinically relevant spleen and symptom responses with fedratinib, and effective mitigation of GI AEs.

Purpose: Bromodomain and extraterminal (BET) proteins are key epigenetic transcriptional regulators, inhibition of which may suppress oncogene expression. We report results from 2 independent first-in-human phase 1/2 dose-escalation and expansion, safety and tolerability studies of BET inhibitors INCB054329 (study INCB 54329-101; NCT02431260) and INCB057643 (study INCB 57643-101; NCT02711137)., Patients and Methods: Patients (≥18 years) with advanced malignancies, ≥1 prior therapy, and adequate organ functions received oral INCB054329 (monotherapy) or INCB057643 (monotherapy or in combination with standard-of-care) in 21-day cycles (or 28-day cycles depending on standard-of-care combination). Primary endpoints were safety and tolerability., Results: Sixty-nine and 134 patients received INCB054329 and INCB057643, respectively. Study INCB 54329-101 has been completed; INCB 57643-101 is currently active, but not recruiting (no patients were receiving treatment as of January 8, 2019). Terminal elimination half-life was shorter for INCB054329 versus INCB057643 (mean [SD], 2.24 [2.03] vs. 11.1 [8.27] hours). INCB054329 demonstrated higher interpatient variability in oral clearance versus INCB057643 (CV%, 142% vs. 45.5%). Most common (>20%) any-grade treatment-related adverse events were similar for both drugs (INCB054329; INCB057643): nausea (35%; 30%), thrombocytopenia (33%; 32%), fatigue (29%; 30%), decreased appetite (26%; 22%). Two confirmed complete responses and 4 confirmed partial responses with INCB057643 were reported as best responses., Conclusions: INCB057643 exhibited a more favorable PK profile versus INCB054329; exposure-dependent thrombocytopenia was observed with both drugs which limited the target inhibition that could be safely maintained. Further efforts are required to identify patient populations that can benefit most, and an optimal dosing scheme to maximize therapeutic index., (©2019 American Association for Cancer Research.)

Importance: Myelofibrosis is a hematologic malignancy characterized by splenomegaly and debilitating symptoms. Thrombocytopenia is a poor prognostic feature and limits use of Janus kinase 1 (JAK1)/Janus kinase 2 (JAK2) inhibitor ruxolitinib., Objective: To compare the efficacy and safety of JAK2 inhibitor pacritinib with that of best available therapy (BAT), including ruxolitinib, in patients with myelofibrosis and thrombocytopenia., Design, Setting, and Participants: For this phase 3 randomized international multicenter study-the PERSIST-2 study-of pacritinib vs BAT, 311 patients with myelofibrosis and platelet count 100 × 109/L or less were recruited for analysis. Crossover from BAT was allowed after week 24 or for progression of splenomegaly., Interventions: Patients were randomized 1:1:1 to pacritinib 400 mg once daily, pacritinib 200 mg twice daily, or BAT., Main Outcomes and Measures: Coprimary end points were rates of patients achieving 35% or more spleen volume reduction (SVR) and 50% or more reduction in total symptom score (TSS) at week 24. Efficacy analyses were performed on the intention-to-treat efficacy population, comprising all patients with a randomization date allowing for week 24 data., Results: Overall, 311 patients (mean [SD] age, 63.70 [9.08] years; 171 men [55%] and 140 women [45%]) were included in the study; 149 patients (48%) had prior ruxolitinib. The most common BAT was ruxolitinib (44 patients [45%]); 19 patients (19%) received watchful-waiting only. The intention-to-treat efficacy population included 75 patients randomized to pacritinib once daily; 74, pacritinib twice daily, and 72, BAT. Pacritinib (arms combined) was more effective than BAT for 35% or more SVR (27 patients [18%] vs 2 patients [3%]; P = .001) and had a nonsignificantly greater rate of 50% or more reduction in TSS (37 patients [25%] vs 10 patients [14%]; P = .08). Pacritinib twice daily led to significant improvements in both end points over BAT (≥35% SVR: 16 patients [22%] vs 2 patients [3%]; P = .001; ≥50% reduction in TSS: 24 patients [32%] vs 10 patients [14%]; P = .01). Clinical improvement in hemoglobin and reduction in transfusion burden were greatest with pacritinib twice daily. For pacritinib once daily, pacritinib twice daily, and BAT, the most common (>10%) grade 3 or 4 adverse events were thrombocytopenia (32 patients [31%], 34 patients [32%], 18 patients [18%]), and anemia (28 patients [27%], 23 patients [22%], 14 patients [14%]). In the pacritinib once daily, twice daily, and BAT arms, discontinuation owing to adverse events occurred in 15 patients (14%), 10 patients (9%), and 4 patients (4%)., Conclusions and Relevance: In patients with myelofibrosis and thrombocytopenia, including those with prior anti-JAK therapy, pacritinib twice daily was more effective than BAT, including ruxolitinib, for reducing splenomegaly and symptoms., Trial Registration: clinicaltrials.gov Identifier: NCT02055781.

A total of 1569 patients with chronic myeloid leukemia (CML) referred to our institution within 1 month of diagnosis since 1965 were reviewed: 1148 chronic phase (CP), 175 accelerated phase (AP), and 246 blastic phase (BP). The median survival was 8.9 years in CP, 4.8 years in AP, and 6 months in BP. In CP, the 8-year survival was ≤ 15% before 1983, 42%-65% from 1983-2000, and 87% since 2001. Survival was worse in older patients (P = .004), but this was less significant since 2001 (P = .07). Survival by Sokal risk was significantly different before 2001 (P < .001), but not since 2001 (P = .4). In AP, survival improved over time (P < .001); the 8-year survival in patients treated since 2001 was 75%. Survival by age was not different in years < 2001 (P = .09), but was better since 2001 in patients ≤ 70 years of age (P = .004). In BP, the median survival improved over time (P < .001), although it has been only 7 months since 2001. In summary, survival in CML has significantly improved since 2001, particularly so in CP-AML and AP-CML. Imatinib therapy minimized the impact of known prognostic factors and Sokal risk in CP-CML and accentuated the impact of age in AP- and BP-CML.

Chronic myeloid leukemia (CML) is a myeloproliferative disorder that affects 5000 new patients per year in the United States. Prior to 10 years ago, durable remission was rare and patients often underwent bone marrow transplantation with substantial morbidity and mortality. Fortunately, CML has been the epicenter of exciting advances in cancer therapy with the discovery of the Bcr-Abl gene fusion and the subsequent development of imatinib mesylate, a small molecule tyrosine kinase inhibitor, to target the kinase activity of the bcr-abl protein product. Despite unprecedented durability for complete hematologic, cytogenetic, and molecular responses seen with front-line imatinib therapy, many patients require alternative therapy because of drug intolerance, suboptimal response, primary resistance, secondary resistance, or progression to advanced phase disease. Further, up to 5% of patients present with advanced disease that does not sustain a durable response to tyrosine kinase inhibitors. Thus, up to one third of CML patients require alternate therapy. Chronic myeloid leukemia has become an exemplary model system for understanding molecular targeting and overcoming mechanisms of drug resistance. This review will discuss potential mechanisms of resistance and ongoing research into novel targets and agents for CML resistant to standard of care., (Published by Elsevier Ltd.)

MK-0457 inhibits aurora, BCR-ABL and other kinases and may be clinically active in imatinib resistant leukemia. To define mediators of MK-0457 responsiveness, kinase inhibitory profiles were examined in multiple cell models of imatinib sensitive and resistant disease. Aurora and BCR-ABL kinase inhibition were consistently measured at 20-100 nM and 2-10 microM MK-0457, respectively, but expression of T315I-BCR-ABL and overexpression of Lyn kinase reduced MK-0457 sensitivity. Aurora kinase inhibition was associated with cell cycle restriction and p53 induction and p53-null cells were far less responsive to MK-0457, requiring BCR-ABL inhibitory concentrations for apoptotic activity. In wild-type p53 expressing CML cells MK-0457 sensitivity was modulation by alterations in p53 levels through HDM-2 inhibition and gene silencing. MK-0457 suppressed aurora kinase activity and induced apoptosis in imatinib resistant clinical specimens expressing T315I and other BCR-ABL mutations without effecting BCR-ABL kinase activity. Together, these results suggest that MK-0457 apoptotic activity in CML cells is primarily associated with aurora kinase inhibition but can be altered by multiple molecular changes associated with disease progression or acquisition of imatinib resistance., (2009 Elsevier Inc. All rights reserved.)

Background: Imatinib is a tyrosine kinase inhibitor that is used to treat chronic myelogenous leukemia (CML). BCR-ABL mutations are associated with failure of imatinib treatment in many CML patients. LYN kinase regulates survival and responsiveness of CML cells to inhibition of BCR-ABL kinase, and differences in LYN regulation have been found between imatinib-sensitive and -resistant CML cell lines., Methods: We evaluated cells from 12 imatinib-resistant CML patients with mutation-negative BCR-ABL and from six imatinib-sensitive patients who discontinued therapy because of imatinib intolerance. Phosphorylation of BCR-ABL and LYN was assessed in patient cells and cell lines by immunoblotting with activation state-specific antibodies, co-immunoprecipitation studies, and mass spectroscopy analysis of phosphopeptides. Cell viability, caspase activation, and apoptosis were also measured. Mutations were analyzed by sequencing. The effect of silencing LYN with short interfering RNAs (siRNAs) or reducing activation by treatment with tyrosine kinase inhibitors was evaluated in cell lines and patient cells., Results: Imatinib treatment suppressed LYN phosphorylation in cells from imatinib-sensitive CML patients and imatinib-sensitive cell lines. Imatinib treatment blocked BCR-ABL signaling but did not suppress LYN phosphorylation in cells from imatinib-resistant patients, and persistent activation of LYN kinase was not associated with mutations in LYN kinase or its carboxyl-terminal regulatory domains. Unique LYN phosphorylation sites (tyrosine-193 and tyrosine-459) and associated proteins (c-Cbl and p80) were identified in cells from imatinib-resistant patients. Reducing LYN expression (siRNA) or activation (dasatinib) was associated with loss of cell survival and cytogenetic or complete hematologic responses in imatinib-resistant disease., Conclusions: LYN activation was independent of BCR-ABL in cells from imatinib-resistant patients. Thus, LYN kinase may be involved in imatinib resistance in CML patients with mutation-negative BCR-ABL and its direct inhibition is consistent with clinical responses in these patients.

Lyn kinase functions as a regulator of imatinib sensitivity in chronic myelogenous leukemia (CML) cells through an unknown mechanism. In patients who fail imatinib therapy but have no detectable BCR-ABL kinase mutation, we detected persistently activated Lyn kinase. In imatinib-resistant CML cells and patients, Lyn activation is BCR-ABL independent, it is complexed with the Gab2 and c-Cbl adapter/scaffold proteins, and it mediates persistent Gab2 and BCR-ABL tyrosine phosphorylation in the presence or absence of imatinib. Lyn silencing or inhibition is necessary to suppress Gab2 and BCR-ABL phosphorylation and to recover imatinib activity. Lyn also negatively regulates c-Cbl stability, whereas c-Cbl tyrosine phosphorylation is mediated by BCR-ABL. These results suggest that Lyn exists as a component of the BCR-ABL signaling complex and, in cells with high Lyn expression or activation, BCR-ABL kinase inhibition alone (imatinib) is not sufficient to fully disengage BCR-ABL-mediated signaling and suggests that BCR-ABL and Lyn kinase inhibition are needed to prevent or treat this form of imatinib resistance.

Imatinib mesylate, a targeted inhibitor of BCR-ABL tyrosine kinase, is the standard of care for chronic myeloid leukemia (CML). A phase 2 trial of imatinib in late chronic-phase (CP) CML after interferon-alpha (IFNalpha) failure enrolled 532 patients, 454 with a confirmed diagnosis of CP CML. Median time from diagnosis was 34 months; median duration of imatinib treatment was 65 months. Cumulative best rates of major cytogenetic response (MCyR) and complete cytogenetic response (CCyR) were 67% and 57%, respectively. At the 5-year landmark, 184 (41%) of the 454 patients are in CCyR. At more than 6 years, 199 (44%) of the 454 patients remain on imatinib. Most responses occurred within 12 months of starting imatinib; however, some patients achieved initial MCyR and CCyR more than 5 years after imatinib initiation. Estimated rates of freedom from progression to accelerated phase (AP) and blastic phase (BP) and overall survival at 6 years were 61% and 76%, respectively. Both freedom from progression to AP/BP and overall survival (OS) were associated with cytogenetic response level at 12 months. No increase in rates of serious adverse events was observed with continuous use of imatinib for up to 6.5 years, compared with earlier time points. Imatinib continues to be an effective and safe therapy for patients with CP CML after failure of IFN.

Imatinib was the first treatment for chronic myeloid leukemia (CML) that specifically targeted the causative BCR-ABL oncoprotein, and represented a major therapeutic advance in this disease; however, some patients develop resistance or intolerance. Resistance can be classified as BCR-ABL-dependent (e.g., mutation in the BCR-ABL gene) or BCR-ABL-independent (alternative pathways of disease progression, e.g., SRC-family tyrosine kinases). The investigation of therapeutic options post-imatinib failure resulted in the development and regulatory approval of dasatinib, a BCR-ABL and SRC-family kinase inhibitor. Dasatinib is active across all phases of CML and Philadelphia chromosome-positive acute lymphoblastic leukemia, and demonstrates activity in almost all imatinib-resistant mutations. Other therapeutic options are also under investigation, with nilotinib being the most clinically advanced. Nilotinib is an analog of imatinib with similar multiple kinase targets, but without inhibition of SRC, and reduced in vitro activity against BCR-ABL P-loop mutations compared with dasatinib. Similar to dasatinib, nilotinib has no activity against T315I mutations. The availability of dasatinib and development of other tyrosine kinase inhibitors provide positive prospects for patients with imatinib-resistant or -intolerant CML. Here, we discuss several of these new strategies for treating patients after imatinib failure.

Treatment options are limited for patients with imatinib-resistant or -intolerant accelerated phase chronic myeloid leukemia (CML-AP). Dasatinib is a novel, potent, oral, multitargeted kinase inhibitor of BCR-ABL and SRC-family kinases that showed marked efficacy in a phase 1 trial of patients with imatinib-resistant CML. Results are presented for 107 patients with CML-AP with imatinib-resistance or -intolerance from a phase 2, open-label study further evaluating dasatinib efficacy and safety. At 8 months' minimum follow-up, 81%, 64%, and 39% of patients achieved overall, major (MaHR), and complete hematologic responses, respectively, whereas 33% and 24% attained major and complete cytogenetic remission. Of 69 patients who achieved MaHR, 7 progressed. Seventy-six percent of patients are estimated to be alive and progression-free at 10 months. Response rates for the 60% of patients with baseline BCR-ABL mutations did not differ from the total population. Dasatinib was well tolerated: most nonhematologic adverse events (AEs) were mild to moderate; no imatinib-intolerant patients discontinued dasatinib because of AEs. Although common (76% of patients with severe neutropenia), cytopenias were manageable through dose modification. In summary, dasatinib induced significant hematologic and cytogenetic responses in patients with imatinib resistance or intolerance, was well tolerated, and may represent a potent new therapeutic option for CML-AP. Further follow-up is warranted. This trial was registered at www.clinicaltrials.gov as #CA180005.

Background: The prognosis of patients with chronic myelogenous leukemia (CML) after failure of imatinib mesylate therapy is not well documented., Methods: The outcome of 420 patients with CML post-imatinib failure (resistance-recurrence in 374; toxicities in 46) were reviewed in relation to survival, overall, and by different therapies., Results: The estimated 3-year survival rates were 72% in 88 patients who progressed in chronic phase, 30% in 130 patients who progressed in accelerated phase, 7% in 156 patients who progressed in blastic phase, and 75% in 37 patients in chronic phase with imatinib intolerance. Survival in chronic phase was better when subsequent therapy was nilotinib or dasatinib vs allogeneic stem cell transplant vs others (estimated 2-year survival rates 100% vs 72% vs 67%; P = .01), but not in accelerated-blastic phase., Conclusions: Prognosis post-imatinib failure in chronic phase is reasonable; it is poor if the CML phase post-imatinib failure is accelerated or blastic.

Developing strategies to counteract imatinib resistance constitutes a challenge in chronic myelogenous leukemia (CML). Therapy with the tyrosine kinase inhibitors nilotinib (AMN107) and dasatinib (BMS-354825) has produced high rates of hematologic and cytogenetic response. Src kinase activation has been linked to Bcr-Abl-mediated leukemogenesis and CML progression. In addition to binding Abl kinase with less stringent conformational requirements than imatinib, dasatinib is a potent Src kinase inhibitor. In the current study, we report on 23 patients with CML (19 of them in accelerated or blastic phases) treated with dasatinib after treatment failure with both imatinib and nilotinib. More than half (13; 57%) of 23 patients responded to dasatinib: 10 (43%) had a complete hematologic response (CHR), including 7 (30%) who had a cytogenetic response (2 complete, 4 partial, and 1 minor). These results suggest that dasatinib may be active in some patients after failure with both imatinib and nilotinib.

Chronic myeloid leukemia (CML) was the first human malignant disease to be linked to a single, acquired genetic abnormality. Identification of the BCR-ABL kinase fusion protein and its central role in the pathogenesis of CML provided new opportunities to develop rational molecular targeted therapies. This review provides an update on the underlying pathophysiologies of disease progression and imatinib mesylate resistance, leading to the development of new targeted tyrosine kinase inhibitors for managing CML. Imatinib, a selective inhibitor of BCR-ABL, represents a major success in the era of target-directed cancer chemotherapy. However, patients with advanced CML have been less sensitive to therapy and responses have been short. In addition, treatment resistance is an emerging problem at all disease stages. Insight into factors involved in imatinib resistance and disease progression has highlighted a role for such BCR-ABL-dependent factors as amplification and overexpression of the BCR-ABL gene and the emergence of mutant isoforms of BCR-ABL. However, BCR-ABL-independent factors, including leukemogenic pathways involving kinases other than BCR-ABL, also play a part. In light of the limitations of imatinib against these factors, newer tyrosine kinase inhibitors, including dasatinib (a multitargeted kinase inhibitor of BCR-ABL and Src family kinases) and nilotinib (AMN107, a selective BCR-ABL inhibitor), may provide promising treatment options for patients with CML.

A survival benefit for imatinib mesylate versus interferon-alpha therapy could not be demonstrated in the randomized study in newly diagnosed Philadelphia chromosome (Ph)-positive chronic-phase chronic myelogenous leukemia (CML) due to the high rate of crossover (90%) from interferon-alpha to imatinib mesylate within a year of study entry. We compared survival in 279 patients with newly diagnosed CML treated with imatinib mesylate at our institution (2000-2004) to 650 patients treated with interferon-alpha (1982-1997). The complete cytogenetic response rates were 87% with imatinib mesylate and 28% with interferon-alpha (P < .001). The estimated 3-year survival rates were 96% with imatinib mesylate and 81% with interferon-alpha (P < .01). Survival rates with imatinib mesylate were significantly better than with interferon-alpha within each of the CML prognostic risks groups. By multivariate analysis, imatinib mesylate therapy was identified as an independent favorable prognostic factor, after accounting for the impact of pretreatment factors (hazard ratio, 0.44; P < .01). By landmark analysis at 12 months, survival within each cytogenetic response category was similar with imatinib mesylate or interferon-alpha, suggesting that the survival benefit of imatinib mesylate (versus interferon-alpha in newly diagnosed CML) is through improving cytogenetic response.

Imatinib mesylate suppresses phosphorylation of its kinase target, Bcr-Abl. We hypothesized that loss of p210Bcr-Abl (the kinase target) may lead to imatinib mesylate resistance. We studied K562 cells [chronic myelogenous leukemia (CML) blast crisis line] and MO7E/MBA-1 cells (with MBA-1 cells representing MO7E cells stably transfected with BCR-ABL). Imatinib mesylate resistance developed when p210Bcr-Abl expression was abolished. Furthermore, K562 cells were significantly more growth suppressed after imatinib mesylate exposure than after downregulation of Bcr-Abl expression. Signaling pathways which were functional in the absence of Bcr-Abl expression (NF-kappaB and mitogen-activated protein kinase activation or the growth factor pathway) were disrupted when p210Bcr-Abl was present but dephosphorylated, suggesting that an intact, but enzymatically inactive Bcr-Abl, may interfere with critical growth/signaling pathways. Downregulation of p210Bcr-Abl may be a mechanism by which imatinib mesylate resistance emerges. Samples from three of 15 patients with imatinib mesylate-resistant CML blast crisis had undetectable levels of p210Bcr-Abl. We conclude that retention of a dephosphorylated p210Bcr-Abl has a biologic impact distinct from that of downregulation/loss of p210Bcr-Abl and, in a subset of patients, loss of the target of the kinase inhibitor may lead to imatinib mesylate resistance.

Background: The BCR-ABL tyrosine kinase inhibitor imatinib is effective in Philadelphia chromosome-positive (Ph-positive) leukemias, but relapse occurs, mainly as a result of the outgrowth of leukemic subclones with imatinib-resistant BCR-ABL mutations. We evaluated dasatinib, a BCR-ABL inhibitor that targets most imatinib-resistant BCR-ABL mutations, in patients with chronic myelogenous leukemia (CML) or Ph-positive acute lymphoblastic leukemia (ALL)., Methods: Patients with various phases of CML or with Ph-positive ALL who could not tolerate or were resistant to imatinib were enrolled in a phase 1 dose-escalation study. Dasatinib (15 to 240 mg per day) was administered orally in four-week treatment cycles, once or twice daily., Results: A complete hematologic response was achieved in 37 of 40 patients with chronic-phase CML, and major hematologic responses were seen in 31 of 44 patients with accelerated-phase CML, CML with blast crisis, or Ph-positive ALL. In these two phases, the rates of major cytogenetic response were 45 percent and 25 percent, respectively. Responses were maintained in 95 percent of patients with chronic-phase disease and in 82 percent of patients with accelerated-phase disease, with a median follow-up more than 12 months and 5 months, respectively. Nearly all patients with lymphoid blast crisis and Ph-positive ALL had a relapse within six months. Responses occurred among all BCR-ABL genotypes, with the exception of the T315I mutation, which confers resistance to both dasatinib and imatinib in vitro. Myelosuppression was common but not dose-limiting., Conclusions: Dasatinib induces hematologic and cytogenetic responses in patients with CML or Ph-positive ALL who cannot tolerate or are resistant to imatinib. (ClinicalTrials.gov number, NCT00064233 [ClinicalTrials.gov].)., (Copyright 2006 Massachusetts Medical Society.)

Background: Several staging classification systems, all of which were designed in the preimatinib era, are used for chronic myeloid leukemia (CML). The World Health Organization (WHO) recently proposed a new classification system that has not been validated clinically. The authors investigated the significance of the WHO classification system and compared it with the classification systems used to date in imatinib trials ("standard definition") to determine its impact in establishing the outcome of patients after therapy with imatinib., Methods: In total, 809 patients who received imatinib for CML were classified into chronic phase (CP), accelerated phase (AP), and blast phase (BP) based on standard definitions and then were reclassified according to the new WHO classification system. Their outcomes with imatinib therapy were compared, and the value of individual components of these classification systems was determined., Results: With the WHO classification, 78 patients (10%) were reclassified: 45 patients (6%) were reclassified from CP to AP, 14 patients (2%) were reclassified from AP to CP, and 19 patients (2%) were reclassified from AP to BP. The rates of complete cytogenetic response for patients in CP, AP, and BP according to the standard definition were 72%, 45%, and 8%, respectively. After these patients were reclassified according to WHO criteria, the response rates were 77% (P = 0.07), 39% (P = 0.28), and 11% (P = 0.61), respectively. The 3-year survival rates were 91%, 65%, and 10%, respectively, according to the standard classification and 95% (P = 0.05), 63% (P = 0.76), and 16% (P = 0.18), respectively, according to the WHO classification. Patients who had a blast percentage of 20-29%, which is considered CML-BP according to the WHO classification, had a significantly better response rate (21% vs. 8%; P = 0.11) and 3-year survival rate (42% vs. 10%; P = 0.0001) compared with patients who had blasts > or = 30%., Conclusions: Different classification systems had an impact on the outcome of patients, and some prognostic features had different prognostic implications in the imatinib era. The authors believe that a new, uniform staging system for CML is warranted, and they propose such a system., ((c) 2006 American Cancer Society.)

The BCR/ABL kinase has been targeted for the treatment of chronic myelogenous leukemia (CML) by imatinib mesylate. While imatinib has been extremely effective for chronic phase CML, blast crisis CML and Ph+ acute lymphoblastic leukemia (ALL) are often resistant. In particular, mutation of the T315 residue in the bcr/abl activation loop renders cells highly resistant to imatinib and to second-generation kinase inhibitors such as BMS-354825 or AMN107. Adaphostin is a tyrphostin that was originally intended to inhibit the BCR/ABL kinase by competing with its peptide substrates. Recent findings have in addition implicated reactive oxygen species (ROS) in the cytotoxic mechanism of adaphostin. In view of this unique mode of action, we examined the effects of adaphostin on numerous imatinib-resistant leukemia models, including imatinib-resistant CML and Ph+ ALL cell lines, cells harboring point mutations in BCR/ABL, and specimens from imatinib-resistant CML patients, using assays for intracellular ROS, apoptosis, and clonogenicity. Every model of imatinib resistance examined remained fully sensitive to adaphostin-induced cell death. Collectively, these data suggest that ROS generation by adaphostin overcomes even the most potent imatinib resistance in CML and Ph+ ALL.

Purpose: Imatinib has potential teratogenicity in animals, but the effect of exposure to imatinib during conception and pregnancy in humans is not known., Patients and Methods: The records of all patients with chronic myeloid leukemia (CML) treated with imatinib were reviewed. We report the experience on 19 pregnancies involving 18 patients (10 females and eight males) who conceived while receiving imatinib for the treatment of CML., Results: All female patients discontinued therapy immediately on recognition of pregnancy. Three pregnancies (involving two female patients and one male patient) ended in spontaneous abortion, and one patient had an elective abortion. All other pregnancies were uneventful. Two of the 16 babies had minor abnormalities at or shortly after birth (hypospadias in one baby and rotation of small intestine in one baby) that were surgically repaired. All babies have continued normal growth and development. Among female patients who interrupted therapy, five of nine in complete hematologic remission (CHR) at the time of treatment interruption eventually lost CHR, and six experienced an increase in Philadelphia chromosome-positive metaphases. At a median of 18 months after resuming therapy with imatinib, eight patients had a cytogenetic response (complete in three patients)., Conclusion: Although there is no evidence that a brief exposure to imatinib during conception and pregnancy adversely affects the developing fetus, most patients lose their response after treatment interruption. Patients receiving imatinib should be advised to practice adequate contraception.

Purpose: Epithelial tumors, including non-small cell lung cancer (NSCLC) and head and neck squamous cell carcinoma (HNSCC), present clinical challenges. One potential target for systemic therapy is Src family nonreceptor tyrosine kinases, which are overexpressed in these tumors and induce pleiotropic effects, including increased proliferation, enhanced survival, stimulation of angiogenesis, and changes in motility. Dasatinib (BMS-354825), an ATP-competitive, small molecule tyrosine kinase inhibitor, suppresses the activity of these kinases at subnanomolar concentrations. Therefore, we tested the antitumor effects of this inhibitor in vitro to determine whether in vivo analyses were warranted., Experimental Design: The antitumor effects of dasatinib on HNSCC and NSCLC cells were evaluated using assays to measure cell cycle progression, apoptosis, migration, and invasion. Western blotting was used to monitor its effects on cell signaling., Results: Dasatinib inhibited migration and invasion in all cell lines and induced cell cycle arrest (blocking the G1-S transition) and apoptosis in some lines. The effects on migration and invasion correlated with the inhibition of Src and downstream mediators of adhesion [e.g., focal adhesion kinase (FAK), p130, and paxillin], and the cell cycle effects and apoptosis correlated with the induction of p27 and the dephosphorylation of Rb. Dasatinib also induced morphologic changes that were consistent with an upstream role for Src in regulating focal adhesion complexes., Conclusions: This study showed that Src inhibition in HNSCC and NSCLC has antitumor effects in vitro. This suggests that dasatinib would have therapeutic activity against these tumors. Clinical studies in these tumor types are warranted.

Background: Myelofibrosis is associated historically with a poor prognosis in patients with chronic myelogenous leukemia (CML). Its significance in the recent era of effective therapy with imatinib mesylate is unknown., Methods: The current study evaluated the significance of the degree of pretreatment myelofibrosis on response and survival with imatinib therapy in patients with newly diagnosed CML. The study group comprised 198 patients with newly diagnosed Philadelphia chromosome-positive, chronic-phase CML treated with imatinib mesylate therapy. They were analyzed for the prognostic significance of bone marrow reticulin fibrosis., Results: Severe reticulin (Grade 3-4) fibrosis was observed in 75 patients (38%): Grade 3 in 46 (23%) patients and Grade 4 in 29 (15%) patients. There was a trend towards a lower incidence of a complete cytogenetic response in patients with Grade 4 reticulin fibrosis (76% vs. 89%; P = 0.07), and a significantly worse survival (estimated 3-year survival rate of 87% vs. 97%; P = 0.04)., Conclusions: Although the prognostic significance of severe reticulin fibrosis in patients with newly diagnosed CML receiving imatinib therapy was better, 15% of patients with Grade 4 reticulin fibrosis still had a worse outcome.

One hundred and ten patients with Philadelphia chromosome (Ph)-positive chronic phase chronic myelogenous leukemia (CML) post-interferon-a failure treated with imatinib mesylate therapy were analyzed for the prognostic significance of marrow reticulin stain-measured fibrosis. The median time from diagnosis was 31 months. Severe reticulin (grade 3 - 4) fibrosis was observed in 67 patients (61%). Patients with severe marrow fibrosis had similar complete cytogenetic response rates with imatinib (67 vs. 58%; P = 0.45) compared with those with mild?-?moderate fibrosis. The estimated 4 year survival rates (80 vs. 88%; P = 0.27) and failure-free survival rates (69 vs. 77%; P = 0.34) were also not different. We conclude that the previously established poor prognostic significance of marrow fibrosis in CML is less relevant with imatinib therapy.

Purpose: To determine the activity of decitabine, a DNA methylation inhibitor, in imatinib-refractory or intolerant chronic myelogenous leukemia., Materials and Methods: Thirty-five patients were enrolled in this phase II study (12 in chronic phase, 17 in accelerated phase, and six in blastic phase). Decitabine was administered at 15 mg/m2 intravenously over 1 hour daily, 5 days a week for 2 weeks. DNA methylation was measured using a LINE1 bisulfite/pyrosequencing assay., Results: Complete hematologic responses were seen in 12 patients (34%) and partial hematologic responses in seven patients (20%), for an overall hematologic response rate of 54% (83% in chronic phase, 41% in accelerated phase, and 34% in blastic phase). Major cytogenetic responses were observed in six patients (17%), and minor cytogenetic responses were seen in 10 patients (29%) for an overall cytogenetic response rate of 46%. Median response duration was 3.5 months (range, 2 to 13+ months). Myelosuppression was the major adverse effect, with neutropenic fever in 28 (23%) of 124 courses of therapy. LINE1 methylation decreased from 71.3% +/- 1.4% (mean +/- standard error of the mean) to 60.7% +/- 1.4% after 1 week, 50.9% +/- 2.4% after 2 weeks, and returned to 66.5% +/- 2.7% at recovery of counts (median, 46 days). LINE1 methylation at the end of week 1 did not correlate with subsequent responses. However, at day 12, the absolute decrease in methylation was 14.5% +/- 3.0% versus 26.8% +/- 2.7% in responders versus nonresponders (P = .007)., Conclusion: Decitabine induces hypomethylation and has clinical activity in imatinib refractory chronic myelogenous leukemia. We hypothesize that the inverse correlation between hypomethylation 2 weeks after therapy and response is due to a cell death mechanism of response, whereby resistant cells can withstand more hypomethylation.

Background: The effect of imatinib mesylate on survival in the accelerated phase of chronic myelogenous leukemia (CML) is unknown. The objectives of this study were to update the long-term experience with imatinib in patients who had accelerated-phase CML and to compare outcomes with historic experience., Methods: The outcomes of 176 patients who received treatment with imatinib were reviewed and compared with the outcomes of 213 historic control patients with accelerated-phase CML who received treatment with interferon-alpha or with other modalities., Results: With imatinib, the complete hematologic response rate was 82% versus a rate < or = 50% for others, and the complete cytogenetic response rate was 43% versus rates of 0-6% for others. The estimated 4-year survival rates were 53% with imatinib, 42% with interferon-alpha, and 0-21% for others. A multivariate analysis of the total population of 389 patients indicated that imatinib therapy (vs. other therapies) was an independent, favorable prognostic factor for survival (P < 0.0001; hazard rate, 0.62). A subset analysis that included only patients who were treated with imatinib and interferon-alpha (276 patients) also identified imatinib as an independent favorable prognostic factor (P < 0.0001; hazard rate, 0.65). The 3-month cytogenetic response to imatinib was associated with significantly different survival outcomes (P < 0.0001). A multivariate analysis that included pretreatment characteristics and 3-month cytogenetic response among 150 patients who received imatinib and were alive at 3 months identified only 2 adverse independent prognostic factors: lack of a cytogenetic response at 3 months (P < 0.001) and anemia (hemoglobin < 10 g/dL; P = 0.003). Patients who had neither factor (41%) had an estimated 4-year survival rate of 88%; in the other patients, the 4-year survival rate was < or = 60%. This may have implications in relation to subsequent therapy, because, according to the outcomes of patients who underwent allogeneic transplantation in accelerated phase at the authors' institution and from literature reports, the estimates of 5-year survival were 25-30%., Conclusions: The current results suggest that imatinib improved survival compared with other therapies in patients with accelerated-phase CML.

Purpose: To determine the clinical significance of molecular response and relapse among patients with chronic myelogenous leukemia (CML) treated with imatinib., Experimental Design: We analyzed the results of quantitative PCR in 280 patients with CML in chronic phase who achieved complete cytogenetic remission with imatinib (117 after IFN-alpha failure and 163 previously untreated). Median follow-up was 31 months (range, 3-52 months)., Results: Median BCR-ABL/ABL ratio before the start of therapy was 39.44 (range, 0.252-170.53). A major molecular response (BCR-ABL/ABL ratio <0.05%) was achieved in 174 (62%), and transcripts became undetectable (complete molecular response) in 95 (34%). By multivariate analysis, only treatment with high-dose imatinib (P = 0.02) was associated with achievement of a major molecular response. Nine of 166 (5%) patients who achieved a major molecular response lost their cytogenetic remission, compared with 25 of 68 (37%) among those who did not achieve this response (P < 0.0001). Patients achieving a major molecular response 12 months after the start of therapy had significantly better complete cytogenetic remission duration than others. A >1-log reduction in transcript levels after 3 months of therapy predicted for an improved probability of achieving a major molecular response at 24 months. Increasing levels of BCR-ABL transcripts predicted for a loss of cytogenetic remission only among patients who did not achieve a major molecular response., Conclusions: Achieving a major molecular response, particularly within the first year of therapy, is predictive of a durable cytogenetic remission and may be the future goal of therapy in CML.

Deletions of derivative chromosome 9 [der(9)] can be identified by fluorescence in situ hybridization (FISH) in 10% to 15% of patients with chronic myeloid leukemia (CML). Patients with der(9) deletions have been reported to have an adverse outcome when treated with chemotherapy, interferon, and possibly imatinib mesylate. We investigated the frequency and prognostic significance of der(9) deletions among 352 patients with CML treated with imatinib mesylate at our institution, in whom a deletion status of der(9) was determined. Thirty-three patients (9%; 95% CI 0.07, 0.13) (30 in chronic phase, 3 in accelerated phase) had der(9) deletions. The rates of major (82% vs 79%, P = 0.82) and complete cytogenetic response (76% vs 66%, P = .33) with imatinib mesylate therapy were similar in patients with and without der(9) deletions, respectively. After a median follow-up of 28 months, there was no difference in overall survival (P = .30) or response duration (P = .49) in patients with and without deletions. In a multivariate analysis, der(9) deletions had no significant impact on response, survival, or response duration. We conclude that treatment with imatinib mesylate overcomes the adverse prognostic significance of der(9) deletions in patients with CML.

We reviewed 261 patients with chronicphase chronic myelogenous leukemia (CML) after interferon-alpha (IFN-alpha) failure treated with imatinib mesylate 400 mg daily. With a median follow-up time of 45 months, the major cytogenetic response rate was 73% and the complete cytogenetic response rate 63%. The estimated 4-year survival rate was 86%. Multivariate analysis for survival identified hematologic resistance to IFN-alpha (P =.01), splenomegaly (P =.03), and lack of any cytogenetic response after 3 months of therapy (P =.01) to have independent poor prognostic significance. Patients could be divided into good (no adverse factors), intermediate (1 adverse factor), and poor-risk groups (2 or 3 adverse factors; 12% of patients) with estimated 4-year survival rates of 96%, 86%, and 49%, respectively (P <.00001). The 4-year cumulative major molecular response (quantitative reverse transcriptase-polymerase chain reaction [Q-PCR] = BCR-ABL/ABL less than 0.05%) rate was 43% and complete molecular response rate (BCR-ABL undetectable) 26%. Compared with a historical group of 251 similar patients treated with nonimatinib therapies, imatinib mesylate was associated with a better 4-year survival rate (86% versus 43%; P <.0001); the survival advantage was confirmed by multivariate analysis (hazard ratio, 0.19; P <.0001).

Background: Reticulin-stained bone marrow fibrosis is associated with a poor prognosis in patients with chronic myelogenous leukemia (CML). Resolution of fibrosis with therapy may improve patient outcome., Methods: The effect of imatinib therapy on bone marrow fibrosis was evaluated in 40 patients with chronic-phase CML who were treated after interferon-alpha failure., Results: Thirty-one patients (78%) had severe (Grade 3 or 4) reticulin fibrosis prior to therapy. After imatinib therapy was administered for 3 to > 24 months, fibrosis was reduced by at least 2 grades in 19 of the 31 patients (61%) and by at least 1 grade in 34 patients (85%). There was no correlation noted between reduction of fibrosis and cytogenetic response. However, a reduction in fibrosis was found to correlate with a reduction in bone marrow megakaryocytosis (P = 0.002)., Conclusions: Treatment with imatinib mesylate appears to reduce CML-associated bone marrow fibrosis in most patients who are treated during the chronic phase of disease. This effect may be independent of the degree of suppression of Philadelphia chromosome-positive cells, and may improve prognosis in patients with CML., (Copyright 2004 American Cancer Society.)

Imatinib mesylate, an inhibitor of the Bcr-Abl tyrosine kinase, has modest activity in refractory/relapsed Philadelphia chromosome (Ph)-positive acute lymphocytic leukemia (ALL). Use of concurrent chemotherapy and imatinib mesylate in newly diagnosed Ph-positive ALL was explored. There were 20 patients who received hyper-CVAD (cyclophosphamide, vincristine, Adriamycin, and dexamethasone) and imatinib mesylate followed by imatinib mesylate-based consolidation/maintenance therapy. Of these patients, 11 had de novo disease, 4 were primary failures after induction (without imatinib mesylate), and 5 were in complete remission (CR) after induction (without imatinib mesylate). All 15 patients treated for active disease achieved CR. Within a median of 3.5 months in first CR, 10 patients underwent allogeneic stem cell transplantation (SCT). One patient relapsed after matched related SCT. The other 9 patients remained alive in CR with median follow-up of 12 months after SCT (range, 1+ to 17+ months). Among 10 patients ineligible for (no donor or older age) or refusing allogeneic SCT, 1 patient relapsed after one year. There were 5 patients who remained alive in continuous CR for a median of 20 months (range, 4+ to 24+ months), with 2 older patients dying in CR at 15 and 16 months of comorbid conditions. Molecular CRs were achieved in both groups (SCT or no SCT). Outcome with hyper-CVAD and imatinib mesylate appears better than with prior regimens; continued accrual and longer follow-up of the current cohort is needed.

Background: Imatinib mesylate administration has become standard treatment for patients with chronic myelogenous leukemia (CML). Although the safety profile of imatinib is favorable, Grade > or = 3 neutropenia (according to the National Cancer Institute Common Toxicity Criteria) occurs in 35-45% of patients with CML in chronic phase who receive standard-dose imatinib. Myelosuppression results in treatment interruptions, which may compromise responses to imatinib. The authors investigated the ability of granulocyte-colony-stimulating factor (filgrastim) to reverse imatinib-associated neutropenia, thereby allowing for more continuous imatinib administration., Methods: Thirteen patients with chronic-phase CML and Grade > or = 3, imatinib-induced neutropenia were treated with filgrastim. Treatment with filgrastim was initiated after a median of 22 months from the start of imatinib. Eleven patients received filgrastim 5 microg/kg 1-3 times weekly, and 2 patients received filgrastim 5 microg/kg daily; doses were titrated to maintain an absolute neutrophil count (ANC) > or = 10(9)/L., Results: Seven of 11 patients (64%) who began treatment with an ANC < 1.5 x 10(9)/L had responses (i.e., their ANC improved to > or = 2 x 10(9)/L within 21 days); the other 4 patients experienced slower recovery but were able to continue receiving imatinib uninterrupted. Before filgrastim administration was initiated, patients did not receive imatinib (due to neutropenia-related treatment interruptions) for an average of 21% of the total time since the start of imatinib. This figure decreased to 6% after the start of filgrastim treatment (P = 0.0008). Before filgrastim treatment was initiated, only one patient had achieved a major (partial) cytogenetic response. After the start of filgrastim treatment, five patients had major cytogenetic responses (including two complete responses)., Conclusions: The authors concluded that filgrastim may overcome imatinib-associated neutropenia and allow improved delivery of imatinib. Some patients may experience improvements in their responses to therapy as a result., (Copyright 2004 American Cancer Society.)

Background: Myelosuppression occurs in up to 50% of patients with chronic myeloid leukemia (CML) who are treated with imatinib and > or = Grade 3 myelosuppression is reported in approximately 10% of patients., Methods: The authors investigated the prognostic significance of anemia occurring during therapy with imatinib in patients with CML in chronic phase., Results: Of 338 patients treated with imatinib (150 patients after interferon failure and 188 patients with newly diagnosed CML), 230 (68%) developed anemia. In a multivariate analysis, factors associated with an increased probability of developing anemia were a starting hemoglobin level < 12 g/dL, age > or = 60 years, female gender, higher imatinib dose, and intermediate or high Sokal risk group. Of these 230 patients, 102 patients received treatment with 40,000 U of recombinant human erythropoietin administered subcutaneously once weekly. An increase in the hemoglobin level of > or = 2 g/dL was achieved in 69 patients (68%) and 22 patients (22%) had an increase of 1-1.9 g/dL. Patients who developed anemia had a trend toward a lower probability of complete cytogenetic remission compared with patients without anemia (68% vs. 77%; P = 0.14), as well as a trend for inferior survival. Patients with anemia and other manifestations of myelosuppression were found to have a significantly worse outcome than those with isolated anemia., Conclusions: The authors concluded that erythropoietin is safe and effective in patients in chronic-phase CML who develop anemia with imatinib therapy., (Copyright 2004 American Cancer Society.)

Imatinib mesylate (STI571) is effective in chronic phase chronic myelogenous leukemia (CML). However, most patients treated with 400 mg imatinib daily have variable levels of residual molecular disease. We treated 114 patients with newly diagnosed chronic phase CML with 400 mg imatinib twice daily. Overall, 109 patients (96%) had a major cytogenetic response (Philadelphia chromosome [Ph] < 35%), and 103 (90%) had a complete response (Ph 0%). With a median follow-up of 15 months, no patient has progressed to accelerated or blastic phase. The estimated 2-year survival rate was 94%. By quantitative polymerase chain reaction (QPCR) studies, 71 (63%) of 112 patients showed BCR-ABL/ABL percentage ratios decrease to less than 0.05%, and 31 (28%) to undetectable levels. Compared with standard-dose imatinib, high-dose imatinib was associated with significantly better complete cytogenetic response (P =.0005), major molecular response (QPRC < 0.05%; P =.00001), and complete molecular response (undetectable BCR-ABL; P =.001). High-dose imatinib was well tolerated but resulted in more frequent myelosuppression; 82% of patients continue to receive 600 mg or more of imatinib daily. In conclusion, high-dose imatinib induced higher rates of complete cytogenetic response and of molecular response in patients with newly diagnosed chronic phase CML.

Five to 10 per cent of patients with Philadelphia chromosome (Ph)-positive chronic myelogenous leukaemia (CML) have variant translocations involving chromosomes other than 9 and 22. We investigated the characteristics and outcome of patients with variant translocations treated with imatinib. Among 721 patients, 44 (6%) had variant translocations, involving one (n = 39) or two (n = 4) additional chromosomes. Nineteen patients (44%) were in chronic (12 previously untreated), 24 (55%) in accelerated and one (2%) in blastic phase. A major cytogenetic response was achieved in 14 (74%) patients treated in chronic phase and in 14 (58%) treated in accelerated phase. Six of 13 (46%) evaluable patients had deletion of derivative chromosome 9, and there was a trend for a lower response rate in these patients. We compared the 43 patients in chronic or accelerated phase to 678 patients with classic Ph treated with imatinib. The only significant difference in clinical characteristics was a higher frequency of accelerated phase among those with variant translocations (56%) compared with those with classic translocations (38%). No differences in outcome were evident. In a multivariate analysis, variant Ph translocations had no impact in response rate, overall survival or duration of response. We conclude that patients with variant Ph translocations have a similar prognosis to those with classic Ph translocations when treated with imatinib.

Purpose: To evaluate the basic pharmacokinetic (PK) characteristics of imatinib mesylate and assess the relationship between the PK and pharmacodynamic (PD) properties of the drug., Patients and Methods: The PK and PD properties of imatinib were investigated during a phase I trial that included 64 adult patients with Philadelphia chromosome-positive leukemias. Patients received imatinib orally once or twice daily. PK parameters of imatinib, derived from the plasma concentration-time curves, were determined. PD response, defined as the WBC after 1 month of treatment with imatinib, was used to develop an efficacy model. A maximum inhibition-effect model was used to describe the relationship between reduction in WBC and drug exposure parameters., Results: Imatinib exposure was dose proportional after oral administration for the dose range of 25 to 1,000 mg. There was a 1.5- to three-fold drug accumulation after repeated once-daily dosing. Mean plasma trough concentration was 0.57 microg/mL (approximately 1 micromol/L) 24 hours after administration of 350 mg of imatinib at steady-state, which exceeds the 50% inhibitory concentration required to inhibit proliferation of Bcr-Abl-positive leukemic cells. Analysis of PK/PD relationships indicates that the initial hematologic response depends on the administered dose for patients with chronic myeloid leukemia., Conclusion: Drug exposure (area under the concentration-time curve) is dose proportional for the dose range of 25 to 1,000 mg, and there is a 1.5- to three-fold drug accumulation at steady-state after once-daily dosing. Analysis of the relationship between PD (WBC reduction) and PK parameters at steady-state indicates that a dose of 400 mg or greater is required for maximal PD effect.

Imatinib mesylate (IM) binds to the BCR-ABL protein, inhibiting its kinase activity and effectively controlling diseases driven by this kinase. IM resistance has been associated with kinase mutations or increased BCR-ABL expression. However, disease progression may be mediated by other mechanisms that render tumor cells independent of BCR-ABL. To demonstrate this potential, IM-resistant cells were found in chronic myelogenous leukemia patients with continuous BCR-ABL gene expression but undetectable BCR-ABL protein expression. These cells were unresponsive to IM and acquired BCR-ABL-independent signaling characteristics. IM resistance in some patients may be mediated through loss of kinase target dependence.

Purpose: The purpose of this research was to compare the survival of patients with Philadelphia chromosome (Ph) -positive chronic myelogenous leukemia (CML) post-IFN-alpha failure treated with imatinib to historical experiences with standards of care or other therapies., Experimental Design: The outcome of 261 patients with Ph-positive chronic phase CML post-IFN failure treated with imatinib was compared with 204 historical control patients treated for a similar disease status with existing therapies. A subset of 147 patients in late chronic phase CML and 100% Ph-positive status treated with imatinib was compared with 95 patients in a similar disease status treated with IFN. Multivariate analyses were conducted to assess the independent prognostic effect of therapy (imatinib versus other) on survival., Results: In the first analysis involving 261 patients on imatinib plus 204 historical patients, the complete cytogenetic response rates were 62% and 19%, respectively (P < 0.001). A multivariate analysis identified pretreatment peripheral blasts and thrombocytosis to be independent poor prognostic factors for survival. Imatinib therapy (versus others) was a significant independent favorable prognostic factor for survival (hazard ratio, 0.17; P < 0.0001). In the second analysis involving the subset of 147 patients receiving imatinib plus 95 historical patients treated with IFN regimens, the complete cytogenetic response rates were 41% and 7%, respectively (P < 0.001). A multivariate analysis selected pretreatment anemia and peripheral blasts to be significant independent poor prognostic factors for survival. Imatinib therapy (versus IFN) was an independent favorable prognostic factor for survival (hazard ratio, 0.20; P < 0.0001). Three-month and 6-month landmark analyses showed that patients in all cytogenetic response categories (major, minor, and none) after imatinib therapy had survival outcomes better than the historical control population. Within each cytogenetic response category, survival was also better with imatinib than with other therapies., Conclusions: This analysis provides evidence for a survival advantage with imatinib versus other therapies in chronic-phase CML post-IFN failure, and for a survival advantage with imatinib versus IFN in late chronic-phase CML.

Background: Imatinib mesylate induces high rates of hematologic and cytogenetic response in patients with chronic myelogenous leukemia (CML). During therapy with imatinib, up to 45% of patients with CML reportedly experience myelosuppression > or = Grade 3, requiring interruption of therapy and/or dose reductions. The significance of myelosuppression for response to imatinib is unknown., Methods: The authors analyzed 143 patients with late chronic-phase CML who were treated with imatinib after failing interferon. Univariate and multivariate analyses were performed to determine patient characteristics that were correlated with myelosuppression response and the association between myelosuppression and cytogenetic response., Results: Neutropenia > or = Grade 3 (according to National Cancer Institute Common Toxicity Criteria) occurred in 64 patients (45%), and thrombocytopenia > or = Grade 3 occurred in 31 patients (22%). Any myelosuppression > or = Grade 3 was associated with a lower rate of major (P = 0.04) or complete (P = 0.01) cytogenetic responses. This was more pronounced with myelosuppression that lasted > 2 weeks. The major cytogenetic response rate was 58% with Grade > or = 3 myelosuppression compared with a rate of 75% without Grade > or =3 myelosuppression (P = 0.03); the complete cytogenetic response rates were 36% and 63%, respectively (P = 0.001). In a multivariate analysis, pretreatment platelet count, imatinib dose reductions, and duration of myelosuppression were associated significantly with response., Conclusions: Myelosuppression is an independent adverse factor for achieving cytogenetic response with imatinib in patients with CML. Intervention with hematopoietic growth factors in patients with CML who are treated with imatinib should be investigated., (Copyright 2003 American Cancer Society.)

Background: The International Randomized study of Interferon-alpha plus cytarabine (IFN-alpha plus ara-C) versus STI571 (imatinib mesylate) [IRIS trial] in patients with newly diagnosed Philadelphia chromosome (Ph)-positive, chronic-phase chronic myelogenous leukemia (CML) has not shown (to date) a survival advantage for imatinib. This was most likely because approximately 90% of patients receiving IFN-alpha plus ara-C changed to imatinib therapy after a median of 8 months into therapy., Methods: The authors analyzed the results with imatinib therapy in patients with newly diagnosed Ph-positive CML in chronic phase and compared their outcome with patients who received IFN-alpha regimens. A total of 187 patients with Ph-positive CML in early chronic phase treated with imatinib were compared with a historic group of 650 similar patients treated with IFN-alpha regimens from 1982 until 1997., Results: Patients who received imatinib were significantly older and had significantly more bone marrow basophilia and less leukocytosis. The complete cytogenetic response (Ph 0%) rates were better with imatinib (81% vs. 32%; P < 0.001), as were the survival rates (30-month estimated survival rates 98% vs. 88%; P = 0.01). A multivariate analysis of the total study group of 837 patients identified imatinib therapy to be a significant independent favorable prognostic factor for survival (P = 0.01)., Conclusions: The current study is the first to indicate the survival advantage of imatinib compared with IFN-alpha, the previous standard of care, in patients with early chronic-phase CML., (Copyright 2003 American Cancer Society.)

Background: Imatinib mesylate is a tyrosine kinase inhibitor that targets the BCR-ABL protein in CML, c-kit (KIT) and platelet-derived growth factor receptors. In clinical trials with imatinib mesylate, common side effects of nausea, emesis, diarrhea, periorbital edema, fluid retention, and myelosuppression have been documented., Methods: In this case series, the authors describe unique clinical findings of skin hypopigmentation in six patients with CML who were treated with imatinib mesylate., Results: Most patients developed onset of skin hypopigmentation within the first month of treatment and all of the patients experienced additional drug toxicity. Despite patient susceptibility to toxicity, the presence of hypopigmentation did not appear to predict leukemic cell response or clinical outcome. All six patients established a hematologic response but only two patients had a complete cytogenetic response. Imatinib mesylate induced hypopigmentation also appeared to be reversible and potentially dose related., Conclusion: Skin hypopigmentation is a benign side effect from imatinib mesylate treatment that appears to be reversible upon discontinuation or dose reduction. Several lines of evidence have previously reported that KIT and its ligand stem cell factor (SCF) have a regulatory role in melanocyte development and survival, suggesting a rational mechanism of action for imatinib mesylate in the pathogenesis of hypopigmentation. The signal transduction mechanism currently is believed to involve SCF ligand binding of KIT and downstream activation of MAP kinase (Erk-2). Microphthalmia (Mi), a basic helix-loop-helix leucine zipper (bHLHZip) transcription factor, is phosphorylated by MAP kinase at a serine residue (S73). Once phosphorylated, Mi transactivates the tyrosine pigmentation gene promoter and affects pigment production., (Copyright 2003 American Cancer Society.)

A phase II study of troxacitabine, a non-natural dioxolane nucleoside L-enantiomer, was conducted in patients with chronic myelogenous leukemia in blastic phase (CML-BP). Patients were untreated for BP, or treated with imatinib mesylate (IM) as sole prior therapy for BP. Troxacitabine was given as an intravenous infusion over 30 min daily for 5 days at a dose of 8.0 mg/m(2) per day. Thirty-one patients, 29 (93%) of whom had failed prior IM therapy, received 51 courses of therapy. Grade 3 or 4 toxicities included stomatitis (4%), hand-foot syndrome (18%), and skin rash (12%). Four patients (13%) responded. Troxacitabine-based combinations merit study in IM-resistant CML.

Background: Anecdotal cases of chromosomal abnormalities in Philadelphia chromosome (Ph)-negative metaphases have been reported in patients with chronic myelogenous leukemia (CML) in the chronic phase during treatment with interferon and, more recently, with imatinib. This phenomenon is different from true clonal evolution in that the additional cytogenetic abnormality occurs in Ph-negative cells., Methods: The authors analyzed their experience with 342 patients with CML in chronic phase treated with imatinib to investigate the frequency and significance of this event., Results: After a median follow-up of 30 months (range, 16-35 months), 21 patients (6%; 95% confidence interval, 0.04, 0.09) developed 25 chromosomal abnormalities in Ph-negative cells. Thirteen (54%) of these abnormalities were seen in 2 or more metaphases. The median time from the start of treatment with imatinib to the appearance of the abnormalities was 6 months (range, 3-22 months). The most common cytogenetic abnormality detected was trisomy 8 (33%). Twenty of 21 patients (95%) achieved a major (Ph < 35%) cytogenetic response (complete cytogenetic response in 13-62%). After a median follow-up of 22 months (range, 4-33 months), all 21 patients were alive, 20 of them in chronic phase and in complete hematologic response. None of the patients showed features of myelodysplasia., Conclusions: Cytogenetic abnormalities occur in Ph-negative cells in a fraction of patients with CML in chronic phase treated with imatinib. With a short follow-up, no clear clinical consequences can be identified., (Copyright 2003 American Cancer Society.)

Background: The effect on prognosis of adding imatinib mesylate to the treatment of patients with Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML) has not been explored fully. The objective of the current study was to evaluate the benefit of adding imatinib to the treatment sequence of patients with early chronic phase Ph-positive CML who received interferon alpha (IFN)-based regimens as frontline therapy., Methods: A total of 201 patients with early chronic phase Ph-positive CML who were treated on our 3 recent frontline IFN-based programs and were impacted early by the availability of sequential therapy with imatinib were analyzed. Their outcome was compared with that of a historical control group of 293 patients treated from 1982 until 1990 who were treated with IFN programs for early chronic phase CML and who did not have the opportunity of early access to imatinib (because it was not available during that period). Multivariate analysis was used to evaluate the independent effect of imatinib therapy on survival., Results: Of 201 patients who were treated, 159 patients (79%) had their regimen changed sequentially to imatinib after a median duration of 14 months of IFN therapy. Of 139 patients who continued evaluation at our institution, 101 patients (73%; 64% of the total group) achieved a complete cytogenetic response, and 20 of 80 patients analyzed (25%; 10% of the total group) had no disease according to molecular studies (quantitative polymerase chain reaction studies). The estimated 5-year survival rate for the total study group of 201 patients was 86%. Survival of this group was significantly superior to the historic control group of IFN-treated patients who did not have the benefit of imatinib (P = 0.03). The trend also was observed within defined CML risk groups. Imatinib therapy was confirmed as an independent, significant, favorable prognostic factor for survival by multivariate analysis, after accounting for the independent prognostic effect of pretreatment prognostic factors (P = 0.005)., Conclusions: The current analysis is the first to indicate the independent, favorable effect of imatinib on the survival of patients with Ph-positive CML., (Copyright 2003 American Cancer Society.DOI 10.1002/cncr.11665)

Background: Older age is a consistent poor prognostic factor in patients with Philadelphia chromosome (Ph)-positive chronic myelogenous leukemia (CML). Whether this is related to an intrinsic worse disease biology or to inadequate drug delivery or excessive treatment-associated toxicity is unknown. The availability of imatinib mesylate, a selective, Bcr-Abl-targeted therapy that is administered orally with minimal side effects, may clarify whether older age would remain an adverse factor (thus, implying a different age-related CML biology)., Methods: Seven hundred forty-seven patients in different phases of Ph-positive CML who were treated with imatinib from 1999 until the time of last follow-up were evaluated. Among them, 187 patients had newly diagnosed, early chronic phase CML; 351 patients had chronic phase CML after interferon alpha (IFN) failure; 133 patients had accelerated phase CML; and 76 patients had blastic phase CML. The imatinib daily dose varied from 400 mg to 800 mg orally, according to the protocol design. Patients were categorized into a group of older patients (age 60 years or older) or younger patients (age younger than 60 years). Their characteristics, responses to therapy, and survival were compared by univariate and multivariate analyses., Results: One hundred eighty-seven patients had newly diagnosed CML, and 49 patients (26%) were in the older age group. Older patients had similar cytogenetic response rates and survival compared with younger patients. Among 351 patients with late chronic phase CML after IFN failure, 120 patients (34%) were in the older age group. Although the older patients had a lower incidence of achievement of complete cytogenetic response (Ph, 0%) by univariate analysis (56% vs. 44%; P = 0.05), age was not found to be an independent poor prognostic factor in the multivariate analysis. Similarly, older age was not an adverse poor prognostic factor for survival. Forty-two of 133 patients (32%) with accelerated phase CML were older. The incidence of any cytogenetic response was lower in older patients (53% vs. 33%; P = 0.04), but age was not significant in the multivariate analysis. Older patients also had a trend toward worse survival (P = 0.09) that was not significant in the multivariate analysis. Twenty-eight of 76 patients (37%) evaluated in blastic phase were older. Older age was not a significant prognostic factor either for achieving response or for survival., Conclusions: With imatinib therapy, older age appears to have lost much of its prognostic relevance. This suggests that the previous poor prognosis observed with older age was related to treatment-associated factors (e.g., toxicity with allogeneic transplantation or with IFN therapy) rather than to an intrinsic, different disease biology of CML in older patients., (Copyright 2003 American Cancer Society.DOI 10.1002/cncr.11629)

Imatinib at 400 mg daily is effective in chronic-phase chronic myeloid leukemia (CML) after interferon failure, although only a few patients achieve a molecular remission. We investigated whether higher doses of imatinib may be more effective. Thirty-six patients with chronic-phase CML after failure on interferon-alpha were treated with 400 mg imatinib twice daily. Median time from diagnosis was 25 months (range, 10-135 months); 4 patients (11%) had clonal evolution. All 11 patients with active disease achieved complete hematologic response. Excluding patients with fewer than 35% Ph-positive metaphases before the start of therapy, 19 (90%) of 21 evaluable patients achieved a major cytogenetic response. Of 27 evaluable patients, 24 (89%) achieved a complete cytogenetic response. Quantitative polymerase chain reaction was performed in bone marrow every 3 months. Of 32 evaluable patients, 18 (56%) showed BCR-ABL/ABL percentage ratios lower than 0.045%, including 13 (41%) with undetectable levels. With a median follow-up of 15 months, all patients were alive in chronic phase. Toxicities were similar to those reported with standard dose; 71% of patients continue to receive 600 mg or more of imatinib daily. In conclusion, high-dose imatinib induces complete cytogenetic responses in most patients with chronic-phase CML after interferon failure. This is accompanied by a high rate of molecular remission.

Background: Imatinib mesylate is a selective tyrosine kinase inhibitor of c-abl, bcr/abl, c-kit, and platelet-derived growth factor-receptor (PDGF-R). c-kit is expressed in most patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) and PDGF has been implicated in the pathogenesis of myeloproliferative disorders (MPD)., Methods: The authors investigated the efficacy of imatinib in patients with these disorders. Forty-eight patients with AML (n = 10), MDS (n = 8), myelofibrosis (n = 18), atypical chronic myeloid leukemia (CML; n = 7), chronic myelomonocytic leukemia (CMML; n = 3), or polycythemia vera (n = 2) were treated with imatinib 400 mg daily., Results: None of the patients with AML or MDS responded. Among patients with myelofibrosis, 10 of 14 patients with splenomegaly (71%) had a 30% or greater reduction in spleen size, 1 patient had trilineage hematologic improvement, 2 had erythroid hematologic improvement, and 1 had improvement in platelet count. One patient with atypical CML had erythroid hematologic improvement. Both patients with polycythemia vera needed fewer phlebotomies (from 2-3 per year to none during the 8 months of therapy and from 3-6 per year to 1 during 9 months of therapy). None of the three patients with CMML responded. Treatment was well tolerated. The side effects were similar to those observed in patients with CML., Conclusions: Within these small subgroups of disease types, single-agent imatinib did not achieve a significant clinical response among patients with AML, MDS, atypical CML, or CMML without PDGF-R fusion genes. Preliminary data on polycythemia vera are promising and deserve further investigation. Responses among myelofibrosis patients were minor. Therefore, a combination treatment regimen including imatinib may be more effective., (Copyright 2003 American Cancer Society.)

The Philadelphia chromosome translocation (t(9;22)) results in the molecular juxtaposition of two genes, BCR and ABL, to form an aberrant BCR-ABL gene on chromosome 22. BCR-ABL is critical to the pathogenesis of chronic myelogenous leukemia and a subset of acute leukemias. The chimeric Bcr-Abl protein has constitutively elevated tyrosine phosphokinase activity. This abnormal enzymatic activation is critical to the oncogenic potential of Bcr-Abl. Initially, protein kinases were thought to be poor therapeutic targets because of their ubiquitous nature and crucial role in many normal physiologic processes. However, the advent of imatinib mesylate (Gleevec, Novartis Pharmaceuticals, Basel, Switzerland), formerly known as STI571 and CGP57148B, demonstrated that designer kinase inhibitors could be specific. This agent has shown striking activity in chronic myelogenous leukemia. It also inhibits phosphorylation of Kit (stem-cell factor receptor) and platelet-derived growth factor receptor. In addition, it has shown similar impressive responses, with little host toxicity, in gastrointestinal stromal tumors, which harbor activating Kit mutations, and in tumors with activated platelet-derived growth factor receptor. The studies of imatinib mesylate provide proof-of-principle for using aberrant kinases as a therapeutic target and are a model for the promise of molecular therapeutics. This paper reviews the current knowledge on the function of Bcr-Abl and its normal counterparts (Bcr and Abl), as well as the impact of this knowledge on the development of a remarkably successful targeted therapy approach.

Cytogenetic clonal evolution (CE) is a known poor prognostic factor in Philadelphia chromosome-positive chronic myelogenous leukemia (Ph-positive CML). However, its prognostic relevance in the era of imatinib therapy is unknown. We investigated the independent prognostic relevance of CE in 498 patients with Ph-positive CML treated with imatinib for chronic or accelerated phases. One hundred twenty-one patients had CE alone (n = 70) or with other accelerated phase criteria (n = 51). Patients were compared in 4 categories: chronic phase (n = 295), CE only (n = 70), accelerated phase without CE (n = 82), and accelerated phase with CE (n = 51). Statistical methods used established methodologies for univariate and multivariate analyses. In chronic and accelerated phases of CML, CE was not associated with significant differences in major or complete cytogenetic response rates, but it was an independent poor prognostic factor for survival by multivariate analyses in both chronic (P =.005) and accelerated phase (P =.03). Multivariate analyses conducted at the 3-month landmark (including the 3-month cytogenetic response) identified the lack of cytogenetic response at 3 months to be a stronger independent poor prognostic factor for survival than CE for both chronic (major cytogenetic response versus other) and accelerated phase (any cytogenetic response versus other). We conclude that cytogenetic CE is not an important factor for achieving major or complete cytogenetic response with imatinib mesylate therapy, but it is an independent poor prognostic factor for survival in both chronic and accelerated phases of CML. The 3-month cytogenetic response to imatinib mesylate refined the prognostic relevance of such studies in patients on imatinib mesylate therapy.