Nilotinib has a relatively favorable safety profile and is active in imatinib-resistant CML. (ClinicalTrials.gov number, NCT00109707 [ClinicalTrials.gov].).

Acquired imatinib resistance in advanced Philadelphia-positive acute lymphoblastic leukemia (Ph ؉ ALL) has been associated with mutations in the kinase domain (KD) of BCR-ABL. We examined the prevalence of KD mutations in newly diagnosed and imatinib-naive Ph ؉ ALL patients and assessed their clinical relevance in the setting of uniform frontline therapy with imatinib in combination with chemotherapy. Patients enrolled in the German Multicenter Study Group for Adult Acute Lymphoblastic Leukemia (GMALL) trial ADE10 for newly diagnosed elderly Ph ؉ ALL were retrospectively examined for the presence of BCR-ABL KD mutations by denaturing highperformance liquid chromatography (D-HPLC), cDNA sequencing, and allelespecific polymerase chain reaction (PCR). A KD mutation was detected in a minor subpopulation of leukemic cells in 40% of newly diagnosed and imatinib-naive patients. At relapse, the dominant cell clone harbored an identical mutation in 90% of cases, the overall prevalence of mutations at relapse was 80%. P-loop mutations predominated and were not associ- IntroductionIncorporation of the ABL kinase inhibitor imatinib into frontline treatment of Philadelphia-positive acute lymphoblastic leukemia (Ph ϩ ALL) has significantly improved the antileukemic efficacy of induction therapy. Several cooperative ALL study groups have demonstrated complete remission rates consistently above 90%, irrespective of whether imatinib is used alone or combined with multiagent chemotherapy. [1][2][3][4][5][6][7][8][9] These results are superior to previously reported complete remission (CR) rates of 65% to 90% in younger patients [10][11][12][13] and 40% to 60% in Ph ϩ ALL patients older than 60 to 65 years of age. [14][15][16][17] Although accumulating evidence suggests that imatinib-containing therapeutic regimens may also improve long-term outcome in these patients, 3,[6][7][8]14 relapse remains a predominant cause of treatment failure. 3,[7][8][9] Numerous point mutations in the kinase domain (KD) of BCR-ABL that impair imatinib binding to varying degrees have been identified as a major mechanism of acquired resistance in patients with chronic myeloid leukemia (CML). [18][19][20][21][22][23][24][25] Data on BCR-ABL mutations in patients with Ph ϩ ALL or lymphoid blast crisis of CML are more limited. Two studies of patients with advanced Ph ϩ lymphoid leukemias identified 5 different KD mutations in 14 of the 17 evaluated patients with acquired resistance to imatinib. 26,27 Preponderance of the E255K/V P-loop mutation, which occurred in 6 of 9 patients (67%) following their treatment with imatinib was suggested by one of these reports 26 but not by the other. 27 However, all point mutations arose at positions within the KD that are known to be important for drug binding and to confer significant resistance to imatinib in vitro. [18][19][20] This demonstrated that different mutations within the BCR-ABL KD can be responsible for refractoriness of Ph ϩ lymphoid leukemias to imatinib, and also suggested that KD mutations may be a f...

BACKGROUNDElderly patients with Philadelphia chromosome‐positive acute lymphoblastic leukemia (Ph+ALL) have a poor prognosis, with a low complete remission (CR) rate, high induction mortality, and short remission duration. Imatinib (IM) has a favorable toxicity profile but limited antileukemic activity in advanced Ph+ALL. Imatinib in combination with intensive chemotherapy has yielded promising results as front‐line therapy, but its value as monotherapy in newly diagnosed Ph+ALL is not known.METHODSPatients with de novo Ph+ALL were randomly assigned to induction therapy with either imatinib (IndIM) or multiagent, age‐adapted chemotherapy (Indchemo). Imatinib was subsequently coadministered with consolidation chemotherapy.RESULTSIn all, 55 patients (median age, 68 years) were enrolled. The overall CR rate was 96.3% in patients randomly assigned to IndIM and 50% in patients allocated to Indchemo (P = .0001). Nine patients (34.6%) were refractory and 2 patients died during Indchemo; none failed imatinib induction. Severe adverse events were significantly more frequent during Indchemo (90% vs 39%; P = .005). The estimated overall survival (OS) of all patients was 42% ± 8% at 24 months, with no significant difference between the 2 cohorts. Median disease‐free survival was significantly longer in the 43% of patients (21 of 49 evaluable) in whom BCR‐ABL transcripts became undetectable (18.3 months vs 7.2 months; P = .002).CONCLUSIONSIn elderly patients with de novo Ph+ALL, imatinib induction results in a significantly higher CR rate and lower toxicity than induction chemotherapy. With subsequent combined imatinib and chemotherapy consolidation, this initial benefit does not translate into improved survival compared with chemotherapy induction. Cancer 2007. © 2007 American Cancer Society.

We investigated the role of copy number alterations to refine risk stratification in adult Philadelphia chromosome positive (Ph) acute lymphoblastic leukemia (ALL) treated with tyrosine kinase inhibitors (TKIs) and allogeneic stem cell transplantation (aSCT). Ninety-seven Ph ALL patients (median age 41 years; range 18-64 years) within the prospective multicenter German Multicenter ALL Study Group studies 06/99 (n = 8) and 07/2003 (n = 89) were analyzed. All patients received TKI and aSCT in first complete remission (CR1). Copy number analysis was performed with single nucleotide polymorphism arrays and validated by multiplex ligation-dependent probe amplification. The frequencies of recurrently deleted genes were: IKZF1, 76%; CDKN2A/2B, 45%; PAX5, 43%; BTG1, 18%; EBF1, 13%; ETV6, 5%; RB, 14%. In univariate analyses, the presence of CDKN2A/2B deletions had a negative impact on all endpoints: overall survival ( = .023), disease-free survival ( = .012), and remission duration ( = .036). The negative predictive value of CDKN2A/2B deletions was retained in multivariable analysis along with other factors such as timing of TKI therapy, intensity of conditioning, achieving remission after induction phase 1 and BTG1 deletions. We therefore conclude that acquired genomic CDKN2A/2B deletions identify a subgroup of Ph ALL patients, who have an inferior prognosis despite aSCT in CR1. Their poor outcome was attributable primarily to a high relapse rate after aSCT.

Imatinib is highly effective in newly diagnosed, but not in relapsed, Philadelphia chromosome positive acute lymphoblastic leukemia (Ph þ ALL). BCR-ABL tyrosine kinase domain (TKD) mutations are associated with acquired imatinib resistance, but their role in primary resistance is uncertain. Using highly sensitive ligation-PCR and denaturing high-performance liquid chromatography (DHPLC), we identified baseline TKD mutations in 21% and 42% of imatinib-naïve patients with newly diagnosed (n ¼ 26) or recurrent (n ¼ 65) Ph þ ALL, respectively (P ¼ ns). Within 4 weeks of starting the imatinib treatment, absolute levels of mutant bcr-abl transcripts increased significantly in patients with advanced, but not with de novo, Ph þ ALL. The net expansion of pre-existing mutant clones during imatinib treatment resulted in the rapid appearance of initially undetectable TKD mutations, which after 4 weeks were detectable in 70% of patients with advanced disease. There was a high degree of concordance between the type of mutations detected at relapse and during initial imatinib treatment. The profoundly different outgrowth dynamics of leukemic clones with bcr-abl mutations in imatinib-treated patients who differ in their disease history, provides clinical --translational evidence for a contributory role of non-mutational resistance mechanisms, possibly induced by prior chemotherapy. Moreover, the prevalence of pre-existing, clinically relevant TKD may have been underestimated in tyrosine kinase inhibitor-naïve patients with Ph þ ALL.