Improved tolerability by a modified intermittent treatment schedule of dasatinib for patients with chronic myeloid leukemia resistant or intolerant to imatinib.

Intermittent dosing of dasatinib with a once daily regimen has been shown to reduce side effects while preserving clinical efficacy in early and advanced phase chronic myeloid leukemia (CML). Yet, hematologic toxicity and fluid retention demand a dose modification or treatment discontinuation in selected patients. Patients resistant or intolerant to imatinib were retrospectively evaluated based on the toxicity-guided administration of a dose-reduced dasatinib regimen. Patients were treated with an on/off regimen (3 to 5 days on, 2 to 4 days off) to allow regression of dasatinib-dependent off-target toxicity. Patients were followed up by routine hematologic and cytogenetic assessment and molecular monitoring to safeguard clinical response to the altered drug schedule. Thirty-three CML patients primarily in chronic phase with imatinib intolerance (n = 11) or resistance (n = 22) were investigated. Nonexclusive reasons for dose reduction were hematologic toxicity (17/33, 51%) and pleural effusions (18/33, 55%). On/off treatment with a weekend drug holiday significantly reduced pleural effusions and hematologic toxicity. Eighteen of 31 (58%) patients showed effective disease control despite reduced total weekly dasatinib doses, either demonstrated by achieving an improved response level (12/31) or keeping the response level achieved by conventional continuous dosing (6/31). Of note, 10/12 patients with subsequently improved response have been treated for a minimum of 6 months with continuous dosing dasatinib regimens without having achieved the response level achieved after allowing drug holiday. Weekend treatment interruption of dasatinib allows continuation of dasatinib treatment for patients suffering from side effects. These data mandate prospective investigation of alternative intermittent targeting regimens.

Impact of additional cytogenetic aberrations at diagnosis on prognosis of CML: long-term observation of 1151 patients from the randomized CML Study IV.

The prognostic relevance of additional cytogenetic findings at diagnosis of chronic myeloid leukemia (CML) is unclear. The impact of additional cytogenetic findings at diagnosis on time to complete cytogenetic (CCR) and major molecular remission (MMR) and progression-free (PFS) and overall survival (OS) was analyzed using data from 1151 Philadelphia chromosome-positive (Ph(+)) CML patients randomized to the German CML Study IV. At diagnosis, 1003 of 1151 patients (87%) had standard t(9;22)(q34;q11) only, 69 patients (6.0%) had variant t(v;22), and 79 (6.9%) additional cytogenetic aberrations (ACAs). Of these, 38 patients (3.3%) lacked the Y chromosome (-Y) and 41 patients (3.6%) had ACAs except -Y; 16 of these (1.4%) were major route (second Philadelphia [Ph] chromosome, trisomy 8, isochromosome 17q, or trisomy 19) and 25 minor route (all other) ACAs. After a median observation time of 5.3 years for patients with t(9;22), t(v;22), -Y, minor- and major-route ACAs, the 5-year PFS was 90%, 81%, 88%, 96%, and 50%, and the 5-year OS was 92%, 87%, 91%, 96%, and 53%, respectively. In patients with major-route ACAs, the times to CCR and MMR were longer and PFS and OS were shorter (P < .001) than in patients with standard t(9;22). We conclude that major-route ACAs at diagnosis are associated with a negative impact on survival and signify progression to the accelerated phase and blast crisis.

Tolerability-adapted imatinib 800 mg/d versus 400 mg/d versus 400 mg/d plus interferon-α in newly diagnosed chronic myeloid leukemia.

PURPOSE: Treatment of chronic-phase (CP) chronic myeloid leukemia (CML) with imatinib 400 mg/d can be unsatisfactory. Optimization of treatment is warranted. PATIENTS AND METHODS: In all, 1,014 newly diagnosed CP-CML patients were randomly assigned to imatinib 800 mg/d (n = 338), imatinib 400 mg/d (n = 325), or imatinib 400 mg/d plus interferon alfa (IFN-α; n = 351). Dose adaptation to avoid higher-grade toxicity was recommended. First primary end point was major molecular remission (MMR) at 12 months. RESULTS: A higher rate of MMR at 12 months occurred with tolerability-adapted imatinib 800 mg/d than with imatinib 400 mg/d (59% [95% CI, 53% to 65%] v 44% [95% CI, 37% to 50%]; P < .001) or imatinib 400 mg/d plus IFN-α (59% v 46% [95% CI, 40% to 52%]; P = .002). Median dose in the 800-mg/d arm was 628 mg/d with a maximum dose of 737 mg/d during months 4 to 6 and a maintenance dose of 600 mg/d. All three treatment approaches were well tolerated with similar grade 3 and 4 adverse events. Independent of treatment approach, MMR at 12 months showed better progression-free survival (99% v 94%; P = .0023) and overall survival (99% v 93%; P = .0011) at 3 years when compared with > 1% on the international scale or no MMR but showed no difference in 0.1% to < 1% on the international scale, which closely correlates with complete cytogenetic remission. CONCLUSION: Treatment of early-phase CML with imatinib can be optimized. Early high-dose therapy followed by rapid adaptation to good tolerability increases the rate of MMR at 12 months. Achievement of MMR by month 12 is directly associated with improved survival.

Dynamics of mutant BCR-ABL-positive clones after cessation of tyrosine kinase inhibitor therapy.

BACKGROUND: Point mutations of the BCR-ABL tyrosine kinase domain are considered the predominant cause of imatinib resistance in chronic myeloid leukemia. The expansion of mutant BCR-ABL-positive clones under selective pressure of tyrosine kinase inhibition is referred to as clonal selection; there are few data on the reversibility of this phenomenon. DESIGN AND METHODS: The changes of expression of mutant BCR-ABL-positive alleles after cessation of tyrosine kinase inhibitor treatment were examined in 19 patients with chronic myeloid leukemia harboring different mutations in a longitudinal follow-up. The proportion of mutant alleles was quantified by amplification of rearranged ABL sequences followed by mutation-specific restriction digestion, electrophoresis and densitometry. The size of mutant clones was established as a measure of the absolute amount of mutant cells considering the proportion of mutant BCR-ABL transcripts and the total level of BCR-ABL obtained by quantitative reverse transcriptase polymerase chain reaction. RESULTS: The median proportion of mutant transcripts was 97% before and 8% after cessation of tyrosine kinase inhibitor treatment indicating a relative decline of 88% within a median of 6 months. The relative decrease in the size of the mutant clones was 86%. Repeated selection and deselection of the mutant clone after resumption and second cessation of tyrosine kinase inhibitor treatment was observed in individual patients. CONCLUSIONS: Deselection of mutant BCR-ABL-positive clones after cessation of tyrosine kinase inhibitor treatment might be a common, rapid and reproducible phenomenon, although some patients harboring the T315I mutation showed no deselection. Cessation of tyrosine kinase inhibitor treatment may lead to the regression of T315I mutant clones to a level under the limit of detection, offering the therapeutic option of resumed tyrosine kinase inhibitor treatment under close surveillance of the mutation status.

Current treatment concepts of CML.

The elucidation of the triggering molecular mechanism of chronic myeloid leukemia gave rise to the development of imatinib, a tyrosine kinase inhibitor and a prototype of target-oriented drugs. Imatinib led to impressing response and survival rates and now represents the standard therapy of CML. However, a significant proportion of patients do not tolerate or fail to respond to imatinib treatment. Alternative therapies can be offered to those patients. The particular challenge of CML patient management is to recognize an impending imatinib failure by adequate surveillance and to know about therapeutic options to prevent progression of the disease to accelerated phase or blast crisis since these are more difficult to control. Targeted therapy with second-generation tyrosine kinase inhibitors should be used in synopsis with mutational analysis and the patients' history. In this review we present current knowledge of diagnosis, monitoring and therapy strategies of patients with CML.

Detection of centrosome aberrations in disease-unrelated cells from patients with tumor treated with tyrosine kinase inhibitors.

OBJECTIVES: Tyrosine kinase inhibitors (TKIs) target various pathways associated with proliferation of aberrant clones in malignant diseases. Despite good response and acceptable tolerability, little is known concerning long-term toxicity. Furthermore, the influence of these inhibitors on disease-unrelated cells is not investigated yet. METHODS: Centrosome aberrations are hallmarks of various cancers. We sought to evaluate the effect of TKIs on centrosomes of disease-unrelated cells. We examined cells of the oral mucosa (OM) and fibroblasts of patients with chronic myeloid leukemia (CML) treated with dasatinib and bosutinib. Results were compared with data from patients with CML treated with imatinib or nilotinib and with data from patients suffering from renal and hepatocellular carcinomas (RCC/HCC) treated with sorafenib or sunitinib. Cells of healthy donors served as controls. RESULTS: OM cells (n = 12) and fibroblasts (n = 7) of patients with CML treated with dasatinib and OM cells of three patients with CML treated with bosutinib showed centrosomal alterations (mean, 14%) compared with 16 (10 OM and 6 fibroblasts) controls (mean, 3%). OM cells of five patients with CML and one patient with systemic mastocytosis treated with imatinib or nilotinib and of eight patients with RCC or HCC treated with sorafenib or sunitinib showed centrosome defects in a mean of 15%. CONCLUSIONS: Our data have shown that TKI treatment of tumor patients may influence centrosomes in disease-unrelated cells or tissues. This may be important with regard to various observed side effects.

Allogeneic hematopoietic stem cell transplantation (allo SCT) for chronic myeloid leukemia in the imatinib era: evaluation of its impact within a subgroup of the randomized German CML Study IV.

The role of allogeneic stem cell transplantation in chronic myeloid leukemia is being reevaluated. Whereas drug treatment has been shown to be superior in first-line treatment, data on allogeneic hematopoietic stem cell transplantation (allo SCT) as second-line therapy after imatinib failure are scarce. Using an interim safety analysis of the randomized German CML Study IV designed to optimize imatinib therapy by combination, dose escalation, and transplantation, we here report on 84 patients who underwent consecutive transplantation according to predefined criteria (low European Group for Blood and Marrow Transplantation [EBMT] score, imatinib failure, and advanced disease). Three-year survival after transplantation of 56 patients in chronic phase was 91% (median follow-up: 30 months). Transplantation-related mortality was 8%. In a matched pair comparison of patients who received a transplant and those who did not, survival was not different. Three-year survival after transplantation of 28 patients in advanced phase was 59%. Eighty-eight percent of patients who received a transplant achieved complete molecular remissions. We conclude that allo SCT could become the preferred second-line option after imatinib failure for suitable patients with a donor. The study is registered at the National Institutes of Health, http://clinicaltrials.gov: NCT00055874.

ABL single nucleotide polymorphisms may masquerade as BCR-ABL mutations associated with resistance to tyrosine kinase inhibitors in patients with chronic myeloid leukemia.

The BCR-ABL K247R change is based on a rare single nucleotide polymorphism occurring likewise in healthy controls and non-hematologic cell types. Despite its juxtaposition to the P-loop, functional analysis showed no alteration compared to non-mutated BCR-ABL. We sought to investigate if other changes in the BCR-ABL kinase domain should be considered as single nucleotide polymorphisms rather than acquired mutations. A total of 911 chronic myeloid leukemia patients after failure or suboptimal response to imatinib were screened for BCR-ABL kinase domain mutations. Single nucleotide polymorphism analysis was based on the search for nucleotide changes in corresponding normal, non-translocated ABL alleles by ABL allele-specific PCR following mutation analysis. In addition to the K247R polymorphism we uncovered five new single nucleotide polymorphisms within the BCR-ABL kinase domain; two of them led to amino acid changes. Single nucleotide polymorphisms could theoretically contribute to primary but not to secondary resistance to tyrosine kinase inhibitors and must therefore be distinguished from acquired mutations. Novel point mutations should be confirmed by analyzing the normal ABL alleles to exclude polymorphisms.