Charles Chuah

Dasatinib versus Imatinib in Newly Diagnosed Chronic-Phase Chronic Myeloid Leukemia

BACKGROUND Treatment with dasatinib, a highly potent BCR-ABL kinase inhibitor, has resulted in high rates of complete cytogenetic response and progression-free survival among patients with chronic myeloid leukemia (CML) in the chronic phase, after failure of imatinib treatment. We assessed the efficacy and safety of dasatinib, as compared with imatinib, for the first-line treatment of chronic-phase CML. METHODS In a multinational study, 519 patients with newly diagnosed chronic-phase CML were randomly assigned to receive dasatinib at a dose of 100 mg once daily (259 patients) or imatinib at a dose of 400 mg once daily (260 patients). The primary end point was complete cytogenetic response by 12 months, confirmed on two consecutive assessments at least 28 days apart. Secondary end points, including major molecular response, were tested at a significance level of 0.0001 to adjust for multiple comparisons. RESULTS After a minimum follow-up of 12 months, the rate of confirmed complete cytogenetic response was higher with dasatinib than with imatinib (77% vs. 66%, P=0.007), as was the rate of complete cytogenetic response observed on at least one assessment (83% vs. 72%, P=0.001). The rate of major molecular response was higher with dasatinib than with imatinib (46% vs. 28%, P<0.0001), and responses were achieved in a shorter time with dasatinib (P<0.0001). Progression to the accelerated or blastic phase of CML occurred in 5 patients who were receiving dasatinib (1.9%) and in 9 patients who were receiving imatinib (3.5%). The safety profiles of the two treatments were similar. CONCLUSIONS Dasatinib, administered once daily, as compared with imatinib, administered once daily, induced significantly higher and faster rates of complete cytogenetic response and major molecular response. Since achieving complete cytogenetic response within 12 months has been associated with better long-term, progression-free survival, dasatinib may improve the long-term outcomes among patients with newly diagnosed chronic-phase CML. (ClinicalTrials.gov number, NCT00481247.)

A Phase 2 Trial of Ponatinib in Philadelphia Chromosome–Positive Leukemias

BACKGROUND Ponatinib is a potent oral tyrosine kinase inhibitor of unmutated and mutated BCR-ABL, including BCR-ABL with the tyrosine kinase inhibitor-refractory threonine-to-isoleucine mutation at position 315 (T315I). We conducted a phase 2 trial of ponatinib in patients with chronic myeloid leukemia (CML) or Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-positive ALL). METHODS We enrolled 449 heavily pretreated patients who had CML or Ph-positive ALL with resistance to or unacceptable side effects from dasatinib or nilotinib or who had the BCR-ABL T315I mutation. Ponatinib was administered at an initial dose of 45 mg once daily. The median follow-up was 15 months. RESULTS Among 267 patients with chronic-phase CML, 56% had a major cytogenetic response (51% of patients with resistance to or unacceptable side effects from dasatinib or nilotinib and 70% of patients with the T315I mutation), 46% had a complete cytogenetic response (40% and 66% in the two subgroups, respectively), and 34% had a major molecular response (27% and 56% in the two subgroups, respectively). Responses were observed regardless of the baseline BCR-ABL kinase domain mutation status and were durable; the estimated rate of a sustained major cytogenetic response of at least 12 months was 91%. No single BCR-ABL mutation conferring resistance to ponatinib was detected. Among 83 patients with accelerated-phase CML, 55% had a major hematologic response and 39% had a major cytogenetic response. Among 62 patients with blast-phase CML, 31% had a major hematologic response and 23% had a major cytogenetic response. Among 32 patients with Ph-positive ALL, 41% had a major hematologic response and 47% had a major cytogenetic response. Common adverse events were thrombocytopenia (in 37% of patients), rash (in 34%), dry skin (in 32%), and abdominal pain (in 22%). Serious arterial thrombotic events were observed in 9% of patients; these events were considered to be treatment-related in 3%. A total of 12% of patients discontinued treatment because of an adverse event. CONCLUSIONS Ponatinib had significant antileukemic activity across categories of disease stage and mutation status. (Funded by Ariad Pharmaceuticals and others; PACE ClinicalTrials.gov number, NCT01207440 .).

A common BIM deletion polymorphism mediates intrinsic resistance and inferior responses to tyrosine kinase inhibitors in cancer

Tyrosine kinase inhibitors (TKIs) elicit high response rates among individuals with kinase-driven malignancies, including chronic myeloid leukemia (CML) and epidermal growth factor receptor–mutated non–small-cell lung cancer (EGFR NSCLC). However, the extent and duration of these responses are heterogeneous, suggesting the existence of genetic modifiers affecting an individuals response to TKIs. Using paired-end DNA sequencing, we discovered a common intronic deletion polymorphism in the gene encoding BCL2-like 11 (BIM). BIM is a pro-apoptotic member of the B-cell CLL/lymphoma 2 (BCL2) family of proteins, and its upregulation is required for TKIs to induce apoptosis in kinase-driven cancers. The polymorphism switched BIM splicing from exon 4 to exon 3, which resulted in expression of BIM isoforms lacking the pro-apoptotic BCL2-homology domain 3 (BH3). The polymorphism was sufficient to confer intrinsic TKI resistance in CML and EGFR NSCLC cell lines, but this resistance could be overcome with BH3-mimetic drugs. Notably, individuals with CML and EGFR NSCLC harboring the polymorphism experienced significantly inferior responses to TKIs than did individuals without the polymorphism (P = 0.02 for CML and P = 0.027 for EGFR NSCLC). Our results offer an explanation for the heterogeneity of TKI responses across individuals and suggest the possibility of personalizing therapy with BH3 mimetics to overcome BIM-polymorphism–associated TKI resistance.

Early response with dasatinib or imatinib in chronic myeloid leukemia: 3-year follow-up from a randomized phase 3 trial (DASISION)

This analysis explores the impact of early cytogenetic and molecular responses on the outcomes of patients with chronic myeloid leukemia in chronic phase (CML-CP) in the phase 3 DASatinib versus Imatinib Study In treatment-Naive CML patients trial with a minimum follow-up of 3 years. Patients with newly diagnosed CML-CP were randomized to receive 100 mg dasatinib (n = 259) or 400 mg imatinib (n = 260) once daily. The retrospective landmark analysis included patients evaluable at the relevant time point (3, 6, or 12 months). Median time to complete cytogenetic response was 3 vs 6 months with dasatinib vs imatinib. At 3 and 6 months, the proportion of patients with BCR-ABL transcript levels ≤10% was higher in the dasatinib arm. Deeper responses at 3, 6, and 12 months were observed in a higher proportion of patients on dasatinib therapy and were associated with better 3-year progression-free survival and overall survival in both arms. First-line dasatinib resulted in faster and deeper responses compared with imatinib. The achievement of an early molecular response was predictive of improved progression-free survival and overall survival, supporting new milestones for optimal response in patients with early CML-CP treated with tyrosine kinase inhibitors. This study was registered at www.clinicaltrials.gov as NCT00481247.

Regulation of myeloid leukaemia by the cell-fate determinant Musashi

Chronic myelogenous leukaemia (CML) can progress from a slow growing chronic phase to an aggressive blast crisis phase, but the molecular basis of this transition remains poorly understood. Here we have used mouse models of CML to show that disease progression is regulated by the Musashi–Numb signalling axis. Specifically, we find that the chronic phase is marked by high levels of Numb expression whereas the blast crisis phase has low levels of Numb expression, and that ectopic expression of Numb promotes differentiation and impairs advanced-phase disease in vivo. As a possible explanation for the decreased levels of Numb in the blast crisis phase, we show that NUP98–HOXA9, an oncogene associated with blast crisis CML, can trigger expression of the RNA-binding protein Musashi2 (Msi2), which in turn represses Numb. Notably, loss of Msi2 restores Numb expression and significantly impairs the development and propagation of blast crisis CML in vitro and in vivo. Finally we show that Msi2 expression is not only highly upregulated during human CML progression but is also an early indicator of poorer prognosis. These data show that the Musashi–Numb pathway can control the differentiation of CML cells, and raise the possibility that targeting this pathway may provide a new strategy for the therapy of aggressive leukaemias.

Final 5-year study results of DASISION: The dasatinib versus imatinib study in treatment-Naïve chronic myeloid leukemia patients trial

PURPOSE We report the 5-year analysis from the phase III Dasatinib Versus Imatinib Study in Treatment-Naïve Chronic Myeloid Leukemia Patients (DASISION) trial, evaluating long-term efficacy and safety outcomes of patients with chronic myeloid leukemia (CML) in chronic phase (CP) treated with dasatinib or imatinib. PATIENTS AND METHODS Patients with newly diagnosed CML-CP were randomly assigned to receive dasatinib 100 mg once daily (n = 259) or imatinib 400 mg once daily (n = 260). RESULTS At the time of study closure, 61% and 63% of dasatinib- and imatinib-treated patients remained on initial therapy, respectively. Cumulative rates of major molecular response and molecular responses with a 4.0- or 4.5-log reduction in BCR-ABL1 transcripts from baseline by 5 years remained statistically significantly higher for dasatinib compared with imatinib. Rates for progression-free and overall survival at 5 years remained high and similar across treatment arms. In patients who achieved BCR-ABL1 ≤ 10% at 3 months (dasatinib, 84%; imatinib, 64%), improvements in progression-free and overall survival and lower rates of transformation to accelerated/blast phase were reported compared with patients with BCR-ABL1 greater than 10% at 3 months. Transformation to accelerated/blast phase occurred in 5% and 7% of patients in the dasatinib and imatinib arms, respectively. Fifteen dasatinib-treated and 19 imatinib-treated patients had BCR-ABL1 mutations identified at discontinuation. There were no new or unexpected adverse events identified in either treatment arm, and pleural effusion was the only drug-related, nonhematologic adverse event reported more frequently with dasatinib (28% v 0.8% with imatinib). First occurrences of pleural effusion were reported with dasatinib, with the highest incidence in year 1. Arterial ischemic events were uncommon in both treatment arms. CONCLUSION These final results from the DASISION trial continue to support dasatinib 100 mg once daily as a safe and effective first-line therapy for the long-term treatment of CML-CP.

Epidemiologic study on survival of chronic myeloid leukemia and Ph+ acute lymphoblastic leukemia patients with BCR-ABL T315I mutation

The BCR-ABL T315I mutation represents a major mechanism of resistance to tyrosine kinase inhibitors (TKIs). The objectives of this retrospective observational study were to estimate overall and progression-free survival for chronic myeloid leukemia in chronic-phase (CP), accelerated-phase (AP), or blastic-phase (BP) and Philadelphia chromosome-positive (Ph)(+) acute lymphoblastic leukemia (ALL) patients with T315I mutation. Medical records of 222 patients from 9 countries were reviewed; data were analyzed using log-rank tests and Cox proportional hazard models. Median age at T315I mutation detection was 54 years; 57% cases were men. Median time between TKI treatment initiation and T315I mutation detection was 29.2, 15.4, 5.8, and 9.1 months, respectively, for CP, AP, BP, and Ph(+) ALL patients. After T315I mutation detection, second-generation TKIs were used in 56% of cases, hydroxyurea in 39%, imatinib in 35%, cytarabine in 26%, MK-0457 in 11%, stem cell transplantation in 17%, and interferon-alpha in 6% of cases. Median overall survival from T315I mutation detection was 22.4, 28.4, 4.0, and 4.9 months, and median progression-free survival was 11.5, 22.2, 1.8, and 2.5 months, respectively, for CP, AP, BP, and Ph(+) ALL patients. These results confirm that survival of patients harboring a T315I mutation is dependent on disease phase at the time of mutation detection.

Chronic myeloid leukemia in Asia

Chronic myeloid leukemia (CML) in Asia has an incidence rather lower than in Western countries yet tends to afflict a younger population. As in the West, imatinib mesylate (IM, Glivec) has supplanted busulphan, hydroxyurea and interferon-α as first-line treatment. Its use has resulted in a dramatic decline in the number of hematopoietic stem cell transplantations (HSCT) performed. Although it is expensive, IM induces a complete cytogenetic response in 60–90% of newly diagnosed patients, and up to 10% for those in blastic phase. The standard dose of 400 mg is well tolerated by most patients, although adverse events have been observed, including drug-induced cytopenia. Through the Glivec International Patient Assistance Program, the majority of CML patients has access to IM and can expect prolonged survival, even in the absence of HSCT. However, just as in Western countries, resistance to imatinib has emerged in Asian countries. They will require the novel tyrosine kinase inhibitors (dasatinib, nilotinib) becoming available through either clinical trials or market approval. This review examines the available data on CML in China, Hong Kong, India, the Philippines, Singapore, South Korea, Taiwan and Thailand.

Targeting of the MNK–eIF4E axis in blast crisis chronic myeloid leukemia inhibits leukemia stem cell function

Significance Cancer stem cells (CSCs) frequently acquire the ability to self-renew and persist in their hosts by coopting normal stem cell programs. Blast crisis (BC) chronic myeloid leukemia is a prototypic example, as the acquired activation of β-catenin signaling that enables BC CSC function is also important in normal hematopoietic stem cell maintenance. In identifying eIF4E phosphorylation by the MNK kinases as a necessary step in β-catenin activation in BC CSCs, but not normal hematopoietic stem cells, we define a therapeutic target in BC. Our studies suggest that clinical trials with MNK kinase inhibitors are warranted in BC chronic myeloid leukemia. Chronic myeloid leukemia responds well to therapy targeting the oncogenic fusion protein BCR-ABL1 in chronic phase, but is resistant to treatment after it progresses to blast crisis (BC). BC is characterized by elevated β-catenin signaling in granulocyte macrophage progenitors (GMPs), which enables this population to function as leukemia stem cells (LSCs) and act as a reservoir for resistance. Because normal hematopoietic stem cells (HSCs) and LSCs depend on β-catenin signaling for self-renewal, strategies to specifically target BC will require identification of drugable factors capable of distinguishing between self-renewal in BC LSCs and normal HSCs. Here, we show that the MAP kinase interacting serine/threonine kinase (MNK)-eukaryotic translation initiation factor 4E (eIF4E) axis is overexpressed in BC GMPs but not normal HSCs, and that MNK kinase-dependent eIF4E phosphorylation at serine 209 activates β-catenin signaling in BC GMPs. Mechanistically, eIF4E overexpression and phosphorylation leads to increased β-catenin protein synthesis, whereas MNK-dependent eIF4E phosphorylation is required for nuclear translocation and activation of β-catenin. Accordingly, we found that a panel of small molecule MNK kinase inhibitors prevented eIF4E phosphorylation, β-catenin activation, and BC LSC function in vitro and in vivo. Our findings identify the MNK–eIF4E axis as a specific and critical regulator of BC self-renewal, and suggest that pharmacologic inhibition of the MNK kinases may be therapeutically useful in BC chronic myeloid leukemia.

Ponatinib versus imatinib for newly diagnosed chronic myeloid leukaemia: an international, randomised, open-label, phase 3 trial

BACKGROUND Ponatinib has shown potent activity against chronic myeloid leukaemia that is resistant to available treatment, although it is associated with arterial occlusion. We investigated whether this activity and safety profile would result in superior outcomes compared with imatinib in previously untreated patients with chronic myeloid leukaemia. METHODS The Evaluation of Ponatinib versus Imatinib in Chronic Myeloid Leukemia (EPIC) study was a randomised, open-label, phase 3 trial designed to assess the efficacy and safety of ponatinib, compared with imatinib, in newly diagnosed patients with chronic-phase chronic myeloid leukaemia. Patients from 106 centres in 21 countries were randomly assigned (1:1, with stratification by Sokal score at diagnosis) using an interactive voice and web response system to receive oral ponatinib (45 mg) or imatinib (400 mg) once daily until progression, unacceptable toxicity, or other criteria for withdrawal were met. Eligible patients were at least 18 years of age, within 6 months of diagnosis, and Philadelphia chromosome-positive by cytogenetic assessment, with Eastern Cooperative Oncology Group performance status of 0-2, and had not previously been treated with tyrosine kinase inhibitors. The primary endpoint was major molecular response at 12 months. Patients who remained on study and had molecular assessments at specified timepoints were studied at those timepoints. Safety analyses included all treated patients, as per study protocol. This trial is registered with ClinicalTrials.gov, number NCT01650805. FINDINGS Between Aug 14, 2012, and Oct 9, 2013, 307 patients were randomly assigned to receive ponatinib (n=155) or imatinib (n=152). The trial was terminated early, on Oct 17, 2013, following concerns about vascular adverse events observed in patients given ponatinib in other trials. Trial termination limited assessment of the primary endpoint of major molecular response at 12 months, as only 13 patients in the imatinib group and ten patients in the ponatinib group could be assessed at this timepoint; the proportion of patients achieving a major molecular response at 12 months did not differ significantly between the two groups (eight [80%] of ten patients given ponatinib and five [38%] of 13 patients given imatinib; p=0·074). 11 (7%) of 154 patients given ponatinib and three (2%) of 152 patients given imatinib had arterial occlusive events (p=0·052); arterial occlusive events were designated serious in ten (6%) of 154 patients given ponatinib and in one (1%) of 152 patients given imatinib (p=0·010). The data monitoring committee criterion for risk assessment (significant difference in serious grade 3 or 4 ischaemic events between groups) was not met (five [3%] of 154 vs one [1%] of 152; p=0·21). Grade 3 or 4 adverse events observed in more than 5% of patients in the ponatinib group were increased lipase (22 [14%] of 154 vs three [2%] of 152 with imatinib), thrombocytopenia (19 [12%] of 154 vs ten [7%] of 152 with imatinib), rash (ten [6%] of 154 vs two [1%] of 152 with imatinib). In the imatinib group, grade 3 or 4 adverse events observed in more than 5% of patients were neutropenia (12 [8%] of 152 vs five [3%] of 154 with ponatinib) and thrombocytopenia (ten [7%] of 152 vs 19 [12%] of 154 with ponatinib). Serious adverse events that occurred in three or more patients given ponatinib were pancreatitis (n=5), atrial fibrillation (n=3), and thrombocytopenia (n=3). No serious adverse event occurred in three or more patients given imatinib. INTERPRETATION The efficacy of ponatinib treatment of newly diagnosed chronic-phase chronic myeloid leukaemia compared with imatinib could not be assessed due to trial termination, but preliminary data suggest there might be benefit, although with more arterial occlusive events than with imatinib at the doses studied. Because the EPIC trial was terminated early, efficacy of ponatinib in this setting remains to be established. FUNDING ARIAD Pharmaceuticals.