Resistance to tyrosine kinase inhibitors in patients with chronic myeloid leukemia (CML) and Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph-positive ALL) is frequently caused by mutations in the BCR-ABL kinase domain. Ponatinib (AP24534) is a potent oral tyrosine kinase inhibitor that blocks native and mutated BCR-ABL, including the gatekeeper mutant T315I, which is uniformly resistant to tyrosine kinase inhibitors.
In this phase 1 dose-escalation study, we enrolled 81 patients with resistant hematologic cancers, including 60 with CML and 5 with Ph-positive ALL. Ponatinib was administered once daily at doses ranging from 2 to 60 mg. Median follow-up was 56 weeks (range, 2 to 140).
Dose-limiting toxic effects included elevated lipase or amylase levels and pancreatitis. Common adverse events were rash, myelosuppression, and constitutional symptoms. Among Ph-positive patients, 91% had received two or more approved tyrosine kinase inhibitors, and 51% had received all three approved tyrosine kinase inhibitors. Of 43 patients with chronic-phase CML, 98% had a complete hematologic response, 72% had a major cytogenetic response, and 44% had a major molecular response. Of 12 patients who had chronic-phase CML with the T315I mutation, 100% had a complete hematologic response and 92% had a major cytogenetic response. Of 13 patients with chronic-phase CML without detectable mutations, 100% had a complete hematologic response and 62% had a major cytogenetic response. Responses among patients with chronic-phase CML were durable. Of 22 patients with accelerated-phase or blast-phase CML or Ph-positive ALL, 36% had a major hematologic response and 32% had a major cytogenetic response.
Ponatinib was highly active in heavily pretreated patients with Ph-positive leukemias with resistance to tyrosine kinase inhibitors, including patients with the BCR-ABL T315I mutation, other mutations, or no mutations. (Funded by Ariad Pharmaceuticals and others; ClinicalTrials.gov number, NCT00660920.)
The success of tyrosine kinase inhibitors (TKIs) in treating chronic myeloid leukemia (CML) depends on the requirement for BCR-ABL1 kinase activity in CML progenitors. However, CML quiescent HSCs are TKI resistant and represent a BCR-ABL1 kinase–independent disease reservoir. Here we have shown that persistence of leukemic HSCs in BM requires inhibition of the tumor suppressor protein phosphatase 2A (PP2A) and expression — but not activity — of the BCR-ABL1 oncogene. Examination of HSCs from CML patients and healthy individuals revealed that PP2A activity was suppressed in CML compared with normal HSCs. TKI-resistant CML quiescent HSCs showed increased levels of BCR-ABL1, but very low kinase activity. BCR-ABL1 expression, but not kinase function, was required for recruitment of JAK2, activation of a JAK2/β-catenin survival/self-renewal pathway, and inhibition of PP2A. PP2A-activating drugs (PADs) markedly reduced survival and self-renewal of CML quiescent HSCs, but not normal quiescent HSCs, through BCR-ABL1 kinase–independent and PP2A-mediated inhibition of JAK2 and β-catenin. This led to suppression of human leukemic, but not normal, HSC/progenitor survival in BM xenografts and interference with long-term maintenance of BCR-ABL1–positive HSCs in serial transplantation assays. Targeting the JAK2/PP2A/β-catenin network in quiescent HSCs with PADs (e.g., FTY720) has the potential to treat TKI-refractory CML and relieve lifelong patient dependence on TKIs.
Allogeneic hematopoietic cell transplantation (HCT) is curative for selected patients with advanced essential thrombocythemia (ET) or polycythemia vera (PV). From 1990 to 2007, 75 patients with ET (median age 49 years) and 42 patients with PV (median age 53 years) underwent transplantations at the Fred Hutchinson Cancer Research Center (FHCRC; n = 43) or at other Center for International Blood and Marrow Transplant Research (CIBMTR) centers (n = 74). Thirty-eight percent of the patients had splenomegaly and 28% had a prior splenectomy. Most patients (69%for ET and 67%for PV) received a myeloablative (MA) conditioning regimen. Cumulative incidence of neutrophil engraftment at 28 days was 88% for ET patients and 90% for PV patients. Acute graft-versus- host disease (aGVHD) grades II to IV occurred in 57% and 50% of ET and PV patients, respectively. The 1-year treatment-related mortality (TRM) was 27% for ET and 22% for PV. The 5-year cumulative incidence of relapse was 13% for ET and 30% for PV. Five-year survival/progression-free survival (PFS) was 55%/47%and 71%/48% for ET and PV, respectively. Patients without splenomegaly had faster neutrophil and platelet engraftment, but there were no differences in TRM, survival, or PFS. Presence of myelofibrosis (MF) did not affect engraftment or TRM. Over 45% of the patients who undergo transplantations for ET and PV experience long-term PFS.
Transplantation; PV; ET
The authors have recently shown that a majority of patients with myelodysplastic syndrome (MDS) classified by the International Prognostic Scoring System as lower risk die without transformation to acute myelogenous leukemia (AML). The cause of death (COD) of these patients is not well understood. Identifying the COD could help to guide early therapy decisions.
The authors retrospectively analyzed the COD in a cohort of 273 deceased patients with lower-risk MDS according to the International Prognostic Scoring System at presentation to The University of Texas M. D. Anderson Cancer Center from 1980 to 2004. MDS-related death was defined as infection, bleeding, transformation to AML, or disease progression. Remaining CODs were classified as non–MDS-related.
Median age at presentation was 66 years (range, 19-88 years). Overall median survival was 59 weeks (range, 1-831 weeks). All French-American-British leukemia classification subgroups were represented. The percentage of International Prognostic Scoring System low and intermediate-1 groups were 21% and 79%, respectively. The most common cytogenetic abnormality (9%) was del(5q). Patients received supportive care only. The COD was identified as MDS-related in 230 of 273 (84%) patients. The most common disease-related CODs were infection (38%), transformation to AML (15%), and hemorrhage (13%). The most frequent non–disease-related COD was cardiovascular events (19 of 43 patients).
The majority of patients with low- or intermediate-1 risk MDS will die because of causes related to their underlying disease. Although these results need to be validated in different populations, early therapeutic intervention could be considered in the management of these patients to improve survival.
myelodysplastic syndrome; mortality; International Prognostic Scoring System; cause of death
The annual incidence of chronic myeloid leukemia (CML) in the United States is about 4800 cases. With the success of tyrosine kinase inhibitor (TKI) therapy, the all-cause annual mortality rate was reduced to 2%. The prevalence of CML is therefore increasing over time. Estimating the CML prevalence and plateau prevalence is important in the implementation of healthcare strategies and future therapeutic trials.
Estimate the increasing prevalence and plateau prevalence of CML in future years.
The prevalence of CML was estimated based on several parameters: annual mortality rate on TKI therapy compared to age-matched normal population, incidence of CML, anticipated population growth in the United States, aging of the population.
Based on these calculations, the mortality ratio of patients with CML compared to an age-matched normal population is about 1.53. The prevalence of CML is estimated to be about 70,000 in 2010, 112,000 in 2020, 144,000 in 2030, 167,000 in 2040 and 181,000 in 2050 when it reaches a near plateau prevalence.
The prevalence of CML will continue to increase to reach a near plateau prevalence 35 times the annual incidence. These estimates should be considered in healthcare policies and in the design of future studies in CML.
The long-term outcome of patients with chronic phase chronic myeloid leukemia treated with imatinib after failure of interferon alpha therapy has not been detailed.
Patients and Methods
368 patients were analyzed. Univariate and multivariate analyses for survival were conducted using standard statistical methods.
Overall, 247 patients (67%) achieved complete cytogenetic response (CCyR). Of 327 patients studied, 207(63%) achieved major molecular response (MMR), and 99 (30%) had undetectable BCR-ABL levels at some time on therapy. The estimated 10-year survival rate was 68%, progression-free survival rate 67%, and event-free survival rate 51%. By multivariate analysis, age ≥ 60 years, hemoglobin < 10g/dl, marrow basophils ≥ 5%, any peripheral blasts, and clonal evolution were independent adverse factors for survival. The estimated 7-year survival by the presence of none (n=154), 1-2 (n=190), or ≥ 3 factors (n=24) were 93%, 70%, and 25% respectively (p <0.01). Achievement of MMR, CCyR, or partial cytogenetic response at 12 months were associated with significantly better 10-year survival rate by landmark analysis (10-year survival 80-90%) vs. achieving minor cytogenetic response or complete hematologic response (10-year survival 55-65%) vs. other response (10-year survival 10%). Using landmark analysis to include imatinib response at 12 months, achievement of major cytogenetic response or better (hazard ratio 0.12; p< 0.001) and complete hematologic response or minor cytogenetic response (hazard ratio 0.36; p=0.003) were significant favorable prognostic factors.
The estimated 10-year survival rate of 68% in patients with chronic myeloid leukemia receiving imatinib after interferon failure has improved.
Cardiac dysfunction, particularly QT interval prolongation, has been observed with tyrosine kinase inhibitors approved to treat chronic myeloid leukemia. This study examines the effects of ponatinib on cardiac repolarization in patients with refractory hematological malignancies enrolled in a phase 1 trial.
Electrocardiograms (ECGs) were collected at 3 dose levels (30, 45, and 60 mg) at 6 time points. Electrocardiographic parameters, including QTc interval, were measured, and 11 morphological analyses were conducted. Central tendency analyses of ECG parameters were performed using time-point and time-averaged approaches. All patients with at least 2 baseline ECGs and 1 on-treatment ECG were included in the analyses. Patients with paired ECGs and plasma samples were included in the pharmacokinetic/pharmacodynamic analysis to examine the relationship between ponatinib plasma concentration and change from baseline in QT intervals.
Thirty-nine patients at the 30-, 45-, and 60-mg dose levels were included in the central tendency and morphological analyses. There was no significant effect on cardiac repolarization, as evidenced by non-clinically significant mean QTcF changes from baseline of −10.9, −3.6, and −5.0 ms for the 30-, 45-, and 60-mg dose levels, respectively. The morphological analysis revealed 2 patients with atrial fibrillation and 2 with T wave inversion. Seventy-five patients were included in the pharmacokinetic/pharmacodynamic analysis across all dose levels. The slope of the relationship for QTcF versus plasma ponatinib concentration was not positive (−0.0171), indicating no exposure–effect relationship.
Ponatinib is associated with a low risk of QTc prolongation in patients with refractory hematological malignancies.
Ponatinib; BCR-ABL; Chronic myeloid leukemia; Philadelphia chromosome; Drug safety; Electrocardiography
Since its approval in 2001 for frontline management of chronic myelogenous leukemia (CML), imatinib has proven to be very effective in achieving high remission rates and improving prognosis. However, up to 33% of patients will not achieve optimal response. This has led researchers to develop new second- and third-generation tyrosine kinase inhibitors. In this article, we review the mechanisms of resistance, recommendations for monitoring, assessment of milestones, and management options for patients with CML who are resistant to imatinib therapy. We further explain the potential pitfalls that can lead to unnecessary discontinuation, the prognosis of patients whose condition fails to respond to treatment, and the upcoming therapies.
CML; imatinib resistance; treatment; tyrosine kinase inhibitor
The epidemiology of candidemia varies depending on the geographic region. Little is known about the epidemiology of candidemia in Latin America.
We conducted a 24-month laboratory-based survey of candidemia in 20 centers of seven Latin American countries. Incidence rates were calculated and the epidemiology of candidemia was characterized.
Among 672 episodes of candidemia, 297 (44.2%) occurred in children (23.7% younger than 1 year), 36.2% in adults between 19 and 60 years old and 19.6% in elderly patients. The overall incidence was 1.18 cases per 1,000 admissions, and varied across countries, with the highest incidence in Colombia and the lowest in Chile. Candida albicans (37.6%), C. parapsilosis (26.5%) and C. tropicalis (17.6%) were the leading agents, with great variability in species distribution in the different countries. Most isolates were highly susceptible to fluconazole, voriconazole, amphotericin B and anidulafungin. Fluconazole was the most frequent agent used as primary treatment (65.8%), and the overall 30-day survival was 59.3%.
This first large epidemiologic study of candidemia in Latin America showed a high incidence of candidemia, high percentage of children, typical species distribution, with C. albicans, C. parapsilosis and C. tropicalis accounting for the majority of episodes, and low resistance rates.
Despite being highly effective for newly diagnosed chronic myeloid leukemia (CML), imatinib not only is inactive against quiescent CML stem cells, but also has limited activity against blast crisis (BC) CML. The relative activity of Bcr-Abl and the expression levels of antiapoptotic proteins in proliferating and quiescent CD34+ BC CML progenitor cells and the effects of targeting antiapoptotic proteins in these cells are unknown. Here we report higher levels of p-CrkL in quiescent than in proliferating CD34+ progenitor cells and comparable expression levels of Bcl-2, Bcl-xL, Mcl-1, and XIAP in the two populations in BC CML. Inhibition of Bcl-2/Bcl-xL by ABT-737 in cells from patients with tyrosine kinase inhibitor (TKI)-resistant BC CML promoted apoptosis in quiescent CD34+ progenitor cells with an efficacy similar to that in proliferating cells. Combination of ABT-737 with imatinib (which decreases Mcl-1 levels) or triptolide (which decreases Mcl-1 and XIAP) synergistically induced death of both proliferating and quiescent CD34+ progenitor cells obtained from TKI-resistant BC CML patients. These results suggest that antiapoptotic proteins are critical targets in BC CML and that activation of apoptosis signaling can eliminate both proliferating and quiescent CD34+ progenitor cells in BC CML, independent of response to TKIs.
apoptosis; Bcl-2/Bcl-xL; Mcl-1; XIAP; quiescent; CML; progenitors
Background: Previous studies have suggested that NPM1 mutations may be a marker for response to all-trans retinoic acid (ATRA) given as an adjunct to intensive chemotherapy in older patients with acute myeloid leukemia (AML).
Patients and Methods: We examined the impact of the addition of ATRA among patients with diploid cytogenetics treated on a randomized phase II study of fludarabine + cytarabine + idarubicine ± G-CSF ± ATRA with available data on their NPM1 mutation status. Between September 1995 and November 1997, 215 patients were enrolled in the study. Among them, 70 patients had diploid cytogenetic and are the subjects of this analysis.
Results: The median age of the 70 patients was 66 years (range 23–87). Twenty (29%) of patients had NPM1 mutations. Among them 7 (35%) did and 13 (65%) did not receive ATRA in combination with chemotherapy. Complete remission (CR) was achieved in 71% of patients treated with ATRA as compared to 69% without ATRA (P = 0.62). With median follow-up of 12.5 years, the overall survival (OS), event-free survival (EFS), and relapse-free survival (RFS) were similar among patients who received ATRA compared to no ATRA regardless of NPM1 mutation status.
Conclusion: The addition of ATRA to intensive chemotherapy did not affect the overall outcome of patients with AML regardless of NPM1 mutation status.
NPM1; ATRA; AML; elderly; chemotherapy
Outcome in acute myeloid leukemia (AML) worsens with age, at least in part because of higher treatment-related mortality (TRM) in older patients. Eligibility for intensive AML treatment protocols is therefore typically based on age as the implied principal predictor of TRM, although other health- and disease-related factors modulate this age effect.
Patients and Methods
We empirically defined TRM using estimated weekly hazard rates in 3,365 adults of all ages administered intensive chemotherapy for newly diagnosed AML. We used the area under the receiver operator characteristic curve (AUC) to quantify the relative effects of age and other covariates on TRM in a subset of 2,238 patients. In this approach, an AUC of 1.0 denotes perfect prediction, whereas an AUC of 0.5 is analogous to a coin flip.
Regardless of age, risk of death declined once 4 weeks had elapsed from treatment start, suggesting that patients who die during this time comprise a qualitatively distinct group. Performance status (PS) and age were the most important individual predictors of TRM (AUCs of 0.75 and 0.65, respectively). However, multicomponent models were significantly more accurate in predicting TRM (AUC of 0.83) than PS or age alone. Elimination of age from such multicomponent models only minimally affected their predictive accuracy (AUC of 0.82).
These data suggest that age is primarily a surrogate for other covariates, which themselves add significantly to predictive accuracy, thus challenging the wisdom of using age as primary or sole basis for assignment of intensive, curative intent treatment in AML.
The response definitions proposed by the European LeukemiaNet (ELN) are defined on the basis of imatinib front-line therapy. It is unknown whether these definitions apply to patients treated with second-generation tyrosine kinase inhibitors (TKIs).
Patients and Methods
One hundred sixty-seven patients with newly diagnosed chronic myelogenous leukemia (CML) in chronic phase were treated with second-generation TKIs in phase II trials (nilotinib, 81; dasatinib, 86). Median follow-up was 33 months. Event-free survival (EFS) was measured from the start of treatment to the date of loss of complete hematologic response, loss of complete or major cytogenetic response, discontinuation of therapy for toxicity or lack of efficacy, progression to accelerated or blastic phases, or death at any time.
Overall, 155 patients (93%) achieved complete cytogenetic response (CCyR), including 146 (87%) with major molecular response (MMR; complete in 46 patients [28%]). According to the ELN definitions, the rates of suboptimal response were 0%, 2%, 1%, and 12% at 3, 6, 12, and 18 months of therapy, respectively. There was no difference in EFS and CCyR duration between patients who achieved CCyR with and without MMR across all the landmark times of 3, 6, 12, and 18 months.
The use of second-generation TKIs as initial therapy in CML induces high rates of CCyR at early time points. The ELN definitions of response proposed for imatinib therapy are not applicable in this setting. We propose that achievement of CCyR and partial cytogenetic response at 3 months should be considered optimal and suboptimal responses, respectively. The achievement of MMR offered no advantage over CCyR in defining long-term outcome in patients with newly diagnosed CML treated with second-generation TKIs.
Chronic myeloid leukemia (CML) is a clonal stem cell malignancy whose pathogenesis is driven by constitutive activation of the breakpoint cluster region–v-abl Abelson murine leukemia viral oncogene homolog 1 (BCR-ABL1) kinase. Although BCR-ABL1 activation is present in all patients with CML, patients can present in 3 different phases characterized by an increasingly worse prognosis and diminished responsiveness to tyrosine kinase inhibitors: chronic phase, accelerated phase, or blastic phase. The biologic basis for progression from chronic phase to blastic phase and for regulating the homeostasis of tyrosine kinase inhibitor-resistant CML stem cells is not entirely understood.
To shed some light into these aspects of CML biology, the authors used reverse phase protein arrays probed with 112 individual monoclonal antibodies to compare protein expression patterns in 40 samples of leukemia-enriched fractions from patients with CML (25 in chronic phase, 5 in accelerated phase, and 10 in phase).
An analysis of variance (significance cutoff, P < .01) unveiled a set of proteins that were overexpressed in blastic phase, including heat-shock protein 90 (hsp90); retinoblastoma (Rb); apoptosis-inducing factor (AIF); serine/threonine-protein phosphatase 2A (PP2A); B-cell leukemia 2 (Bcl-2); X-linked inhibitor of apoptosis protein (Xiap); human homolog of Drosophila Mad (mothers against decapenta-plegic) and related Caenorhabditis elegans gene Sma, family member 1 (Smad1); single-stranded DNA binding protein 2 alpha (SSBP2α); poly(adenosine diphosphate-ribose) polymerase (PARP); GRB2-associated binding protein 2 (Gab2); and tripartite motif containing 24 (Trim24). It is noteworthy that several of these proteins also were overexpressed in the CD34-positive compartment, which putatively contains the CML stem cell population.
The results from this study indicated that reverse phase protein array analysis can unveil differentially expressed proteins in advanced phase CML that can be exploited therapeutically with targeted approaches.
chronic myeloid leukemia; protein expression; reverse phase protein array; signature; blastic phase; chronic phase; proteomics
The clinical outcome for patients with chronic myeloid leukemia (CML) has changed dramatically in the past 15 years. This has been due to the development of tyrosine kinase inhibitors (TKI), compounds which inhibit the activity of the oncogenic BCR-ABL1 protein. Imatinib was the first TKI developed for CML, and it led to high rates of complete cytogenetic responses and improved survival for patients with this disease. However, about 35% of patients in chronic phase treated with imatinib will develop resistance or intolerance to this drug. The recognition of the problem of imatinib failure led to the design of 2nd-generation TKI (dasatinib, nilotinib and bosutinib). These drugs are highly active in the scenario of imatinib resistance or intolerance. More recently, both nilotinib and dasatinib were approved for frontline use in patients with chronic phase CML. Ponatinib represents the last generation of TKI, and this drug has been developed with the aim of targeting a specific BCR-ABL1 mutation (T315I) which arises in the setting of prolonged TKI therapy and leads to resistance to all commercially available TKI. Parallel to the development of specific drugs for treating CML, major advances were made in the field of disease monitoring and standardization of response criteria. In this review we summarize how therapy with TKI for CML has evolved over the last decade.
Chronic Myelogenous Leukemia; BCR-ABL1; Tyrosine Kinase Inhibitors; Imatinib; Dasatinib; Nilotinib; Bosutinib; Ponatinib
Complete cytogenetic response (CCyR) is the gold standard for response to therapy for patients with chronic myeloid leukemia (CML) because it is associated with a survival benefit. However, patients who have failed initial therapy with a tyrosine kinase inhibitor (TKI) frequently achieve only partial or minor cytogenetic responses. The clinical benefit of such responses is unclear.
Patients and Methods
We analyzed the records of all 165 consecutive patients treated in clinical trials with TKI as second line therapy or beyond after failure to prior imatinib therapy.
A CCyR was achieved with second-line TKI therapy or beyond in 52% of patients, while 7% achieved a partial cytogenetic response (PCyR), 14% a minor cytogenetic response (mCyR), 14% complete hematologic response (CHR) only, and 17% no response. The 3-year survival probability was 98% for those with CCyR, compared to 83% with PCyR, 83% for mCyR, 76% for CHR and 71% for no response. Survival free from transformation rates at 3 years were 93%, 73%, 84%, 88%, and 0%, respectively.
CCyR is associated with the greatest survival benefit among patients treated with 2nd line therapy or beyond and remains the optimal cytogenetic goal of therapy. However, patients with partial and minor cytogenetic response derive a benefit compared to patients who have no response. This benefit should be recognized and evaluated against any alternative option available to a given patient before a change in therapy is recommended.
Although signaling through the type I insulin-like growth factor receptor (IGF-IR) maintains the survival of hematopoietic cells, a specific role of IGF-IR in hematological neoplasms remains largely unknown. Chronic myeloid leukemia (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 4 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.
IGF-IR; chronic myeloid leukemia; BCR-ABL; picropodophyllin; imatinib mesylate
Treatment of CML with the tyrosine kinase inhibitor (TKI) imatinib mesylate results in the emergence of point mutations within the kinase domain (KD) of the BCR-ABL1 fusion transcript. The introduction of next-generation TKIs that can overcome the effects of some BCR-ABL1 KD mutations requires quantitative mutation profiling methods to assess responses. We report the design and validation of such quantitative assays, using pyrosequencing and mutation-specific RT-PCR techniques, to allow sequential monitoring and illustrate their use in tracking specific KD mutations (e.g. G250E, T315I, and M351T) following changes in therapy. Pyrosequencing and mutation-specific RT-PCR allows sequential monitoring of specific mutations and identification of rapid clonal shifts in response to kinase inhibitor therapy in CML. Rapid reselection of TKI-resistant clones occurs following therapy switch in CML.
Cells are regulated by networks of controllers having many targets, and targets affected by many controllers, in a “many-to-many” control structure. Here we study several of these bipartite (two-layer) networks. We analyze both naturally occurring biological networks (composed of transcription factors controlling genes, microRNAs controlling mRNA transcripts, and protein kinases controlling protein substrates) and a drug-target network composed of kinase inhibitors and of their kinase targets. Certain statistical properties of these biological bipartite structures seem universal across systems and species, suggesting the existence of common control strategies in biology. The number of controllers is ∼8% of targets and the density of links is 2.5%±1.2%. Links per node are predominantly exponentially distributed. We explain the conservation of the mean number of incoming links per target using a mathematical model of control networks, which also indicates that the “many-to-many” structure of biological control has properties of efficient robustness. The drug-target network has many statistical properties similar to the biological networks and we show that drug-target networks with biomimetic features can be obtained. These findings suggest a completely new approach to pharmacological control of biological systems. Molecular tools, such as kinase inhibitors, are now available to test if therapeutic combinations may benefit from being designed with biomimetic properties, such as “many-to-many” targeting, very wide coverage of the target set, and redundancy of incoming links per target.
CML is a clonal multistep myeloproliferative disease originating from and ultimately sustained by a rare population of BCR-ABL+ cells with multilineage stem cell properties. Imatinib, the most successful of molecular targeted therapies, has revolutionized treatment of patients with CML. Despite this achievement, CML is often not curable, largely due to the innate insensitivity of CML stem cells, particularly when in a quiescent state. This failure of not only imatinib but also the second-generation tyrosine kinase inhibitors frequently leads to relapse upon drug discontinuation. Thus, any curative therapy must eliminate CML stem cells. A comprehensive understanding of the biological properties of CML stem cells and an elucidation of the molecular mechanisms and signaling pathways enabling these CML stem cells to self-renew, combined with insight into the regulation of apoptosis signaling and the mechanisms governing the interaction of CML stem cells with their bone marrow microenvironment, will facilitate the development of therapies for targeting these cells. In this seminar, we will discuss the biological properties of CML stem cells and potential strategies to eliminate them.
The adverse prognosis of CD20 expression in adults with de novo precursor B-lineage acute lymphoblastic leukemia (ALL) prompted incorporation of monoclonal antibody therapy with rituximab into the intensive chemotherapy regimen hyper-CVAD (fractionated cyclophosphamide, vincristine, doxorubicin, dexamethasone). Other modifications (irrespective of CD20 expression) included early anthracycline intensification, alterations in number of risk-adapted intrathecal chemotherapy treatments for CNS prophylaxis, additional early and late intensifications, and extension of maintenance phase chemotherapy by 6 months.
Patients and Methods
Two hundred eighty-two adolescents and adults with de novo Philadelphia chromosome (Ph)–negative precursor B-lineage ALL were treated with standard or modified hyper-CVAD regimens. The latter incorporated standard-dose rituximab if CD20 expression ≥ 20%.
The complete remission (CR) rate was 95% with 3-year rates of CR duration (CRD) and survival (OS) of 60% and 50%, respectively. In the younger (age < 60 years) CD20-positive subset, rates of CRD and OS were superior with the modified hyper-CVAD and rituximab regimens compared with standard hyper-CVAD (70% v 38%; P < .001% and 75% v 47%, P = .003). In contrast, rates of CRD and OS for CD20-negative counterparts treated with modified versus standard hyper-CVAD regimens were similar (72% v 68%, P = not significant [NS] and 64% v 65%, P = NS, respectively). Older patients with CD20-positive ALL did not benefit from rituximab-based chemoimmunotherapy (rates of CRD 45% v 50%, P = NS and OS 28% v 32%, P = NS, respectively), related in part to deaths in CR.
The incorporation of rituximab into the hyper-CVAD regimen appears to improve outcome for younger patients with CD20-positive Ph-negative precursor B-lineage ALL.
The epigenetic impact of DNA methylation in chronic myelogenous leukemia (CML) is not completely understood. To elucidate its role we analyzed 120 patients with CML for methylation of promoter-associated CpG islands of 10 genes. Five genes were identified by DNA methylation screening in the K562 cell line and 3 genes in patients with myeloproliferative neoplasms. The CDKN2B gene was selected for its frequent methylation in myeloid malignancies and ABL1 as the target of BCR-ABL translocation. Thirty patients were imatinib-naïve (mostly treated by interferon-alpha before the imatinib era), 30 were imatinib-responsive, 50 were imatinib-resistant, and 10 were imatinib-intolerant. We quantified DNA methylation by bisulfite pyrosequencing. The average number of methylated genes was 4.5 per patient in the chronic phase, increasing significantly to 6.2 in the accelerated and 6.4 in the blastic phase. Higher numbers of methylated genes were also observed in patients resistant or intolerant to imatinib. These patients also showed almost exclusive methylation of a putative transporter OSCP1. Abnormal methylation of a Src suppressor gene PDLIM4 was associated with shortened survival independently of CML stage and imatinib responsiveness. We conclude that aberrant DNA methylation is associated with CML progression and that DNA methylation could be a marker associated with imatinib resistance. Finally, DNA methylation of PDLIM4 may help identify a subset of CML patients that would benefit from treatment with Src/Abl inhibitors.
Nilotinib is a highly selective Bcr-Abl inhibitor approved for imatinib-resistant chronic myeloid leukemia (CML). Nilotinib and dasatinib, a multi-targeted kinase inhibitor also approved for second line therapy in CML, have different patterns of kinase selectivity, pharmacokinetics, and cell uptake and efflux properties, and thus patients may respond to one following failure of the other. An international Phase II study of nilotinib was conducted in CML patients [39 chronic phase (CP), 21 accelerated phase (AP)] after failure of both imatinib and dasatinib. Median times from diagnosis of CP or AP to nilotinib therapy were 89 and 83 months, respectively. Complete hematologic response and major cytogenetic response (MCyR) rates in CP were 79% and 43% respectively. Of 17 evaluable patients with CML-AP, 5 (29%) had a confirmed hematologic response and 2 (12%) a MCyR. The median time to progression has not yet been reached in CP patients. At 18 months 59% of patients are progression-free. Median overall survival for both populations has not been reached and the estimated 18 month survival rate in CML-CP was 86% and 80% at 12 months for CML-AP. Nilotinib is effective therapy in CML-CP and -AP following failure of both imatinib and dasatinib therapy.
Imatinib; dasatinib; nilotinib; resistance; abl inhibitors
To determine the efficacy and toxicity of the combination of sorafenib, cytarabine, and idarubicin in patients with acute myeloid leukemia (AML) younger than age 65 years.
Patients and Methods
In the phase I part of the study, 10 patients with relapsed AML were treated with escalating doses of sorafenib with chemotherapy to establish the feasibility of the combination. We then treated 51 patients (median age, 53 years; range, 18 to 65 years) who had previously untreated AML with cytarabine at 1.5 g/m2 by continuous intravenous (IV) infusion daily for 4 days (3 days if > 60 years of age), idarubicin at 12 mg/m2 IV daily for 3 days, and sorafenib at 400 mg orally twice daily for 7 days.
Overall, 38 (75%) patients have achieved a complete remission (CR), including 14 (93%) of 15 patients with mutated FMS-like tyrosine kinase-3 (FLT3; the 15th patient had complete remission with incomplete platelet recovery [CRp]) and 24 (66%) of 36 patients with FLT3 wild-type (WT) disease (three additional FLT3-WT patients had CRp). FLT3-mutated patients were more likely to achieve a CR than FLT3-WT patients (P = .033). With a median follow-up of 54 weeks (range, 8 to 87 weeks), the probability of survival at 1 year is 74%. Among the FLT3-mutated patients, 10 have relapsed and five remain in CR with a median follow-up of 62 weeks (range, 10 to 76 weeks). Plasma inhibitory assay demonstrated an on-target effect on FLT3 kinase activity.
Sorafenib can be safely combined with chemotherapy, produces a high CR rate in FLT3-mutated patients, and inhibits FLT3 signaling.