We sought to understand the genesis of the t(9;22) by characterizing genomic breakpoints in chronic myeloid leukemia (CML) and BCR-ABL-positive acute lymphoblastic leukemia (ALL). BCR-ABL breakpoints were identified in p190 ALL (n ¼ 25), p210 ALL (n ¼ 25) and p210 CML (n ¼ 32); reciprocal breakpoints were identified in 54 cases. No evidence for significant clustering and no association with sequence motifs was found except for a breakpoint deficit in repeat regions within BCR for p210 cases. Comparison of reciprocal breakpoints, however, showed differences in the patterns of deletion/insertions between p190 and p210. To explore the possibility that recombinase-activating gene (RAG) activity might be involved in ALL, we performed extra-chromosomal recombination assays for cases with breakpoints close to potential cryptic recombination signal sequence (cRSS) sites. Of 13 ALL cases tested, 1/10 with p190 and 1/3 with p210 precisely recapitulated the forward BCR-ABL breakpoint and 1/10 with p190 precisely recapitulated the reciprocal breakpoint. In contrast, neither of the p210 CMLs tested showed functional cRSSs. Thus, although the t(9;22) does not arise from aberrant variable (V), joining (J) and diversity (D) (V(D)J) recombination, our data suggest that in a subset of ALL cases RAG might create one of the initiating double-strand breaks.
Introduction. ACE-536, a recombinant fusion protein containing modified activin receptor type IIB and IgG Fc, is being developed for the treatment of anemias due to ineffective erythropoiesis, such as myelodysplastic syndromes (MDS). Patients with MDS often have elevated levels of erythropoietin (EPO) and may be non-responsive or refractory to erythropoiesis-stimulating agents (ESAs). MDS patients have also been shown to have increased serum GDF11 levels (Suragani R et al., Nature Medicine 2014) and increased Smad 2/3 signaling in the bone marrow (Zhou L et al., Blood 2008). ACE-536 binds to ligands in the TGF-ß superfamily, including GDF11, inhibits Smad 2/3 signaling, and promotes late-stage erythroid differentiation via a mechanism distinct from ESAs. RAP-536 (murine version of ACE-536) reduced Smad 2 signaling, increased hemoglobin (Hb) levels and decreased bone marrow erythroid hyperplasia in a mouse model of MDS (Suragani R et al., Nature Medicine 2014). In a healthy volunteer study, ACE-536 was well-tolerated and increased Hb levels (Attie K et al., Am J Hematol 2014). Aims. This is an ongoing, phase 2, multicenter, open-label, dose-finding study to evaluate the effects of ACE-536 on anemia in patients with Low or Int-1 risk MDS who have either high transfusion burden (HTB, defined as ≥4 units RBCs/8 weeks prior to baseline) or low transfusion burden (LTB, defined as <4 units RBCs/8 weeks prior to baseline). Study outcomes include erythroid response (either Hb increase in LTB patients or reduced transfusion burden in HTB patients), safety, tolerability, PK, and PD biomarkers. Methods.Inclusion criteria included Low or Int-1 risk MDS, age ≥ 18 yr, anemia (defined as either being HTB patient or having baseline Hb < 10.0 g/dL in LTB patient), EPO >500 U/L or nonresponsive/refractory to ESAs, no prior azacitidine or decitabine, and no current treatment with ESA, G-CSF, GM-CSF, or lenalidomide. In the dose escalation phase, ACE-536 was administered by subcutaneous (SC) injection once every 3 weeks in 7 sequential cohorts (n=3-6) at dose levels of 0.125, 0.25, 0.5, 0.75, 1.0, 1.33 and 1.75 mg/kg for up to 5 doses with a 3-month follow-up. An expansion cohort (n=30) is planned, and all patients completing this study may enroll in a 12-month extension study. Results. Preliminary data were available for 26 patients (7 LTB/19 HTB) as of 18 Jul 2014. Median age was 71 yr (range: 27-88 yr), 50% were female, 54% had prior EPO therapy and 15% had prior lenalidomide. 69% were WHO subtype RCMD, and the remaining patients were del(5q), RARS, or RAEB-1. Mean (SD) baseline Hgb for the LTB patients (n=7) was 9.1 (0.4) g/dL. Mean (SD) units RBC transfused in the 8 weeks prior to treatment was 0.9 (1.1) units for the LTB patients and 6.3 (2.4) units for the HTB patients. Two of the 7 LTB patients had an increase in mean Hb ≥1.5 g/dL over 8 weeks compared to baseline. Mean maximum Hb increase in the LTB patients was 0.8, 1.0, 2.2, and 2.7 g/dL in the 0.125 (n=1), 0.25 (n=1), 0.75 (n=3), and 1.75 (n=2) mg/kg dose groups, respectively. Six of the 7 LTB patients achieved RBC transfusion independence (RBC-TI) for ≥8 weeks during the study. Six of the 19 HTB patients had a ≥4 unit or ≥50% reduction in RBC units transfused over an 8-week interval during the treatment period compared to the 8 weeks prior to treatment; five of these 6 patients achieved RBC-TI ≥ 8 weeks during the study (range 71-152 days). Increases in neutrophil count following study drug administration were observed in some patients. ACE-536 was generally well tolerated. No related serious adverse events have been reported to date. The most frequent adverse events regardless of causality were: diarrhea (n=4, grade 1/2), bone pain, fatigue, muscle spasms, myalgia, and nasopharyngitis (n=3 each, grade 1/2). Conclusions. Based on preliminary data in Low or Int-1 MDS patients, ACE-536 administered SC every 3 weeks for up to 5 doses increased Hb levels or decreased transfusion requirement, with a favorable safety profile. These data strongly support further evaluation of longer-term treatment with ACE-536 in patients with MDS. Disclosures Platzbecker: Celgene: Honoraria, Research Funding. Germing:Celgene: Honoraria, Research Funding. Goetze:Celgene Corp: Honoraria; Novartis Pharma: Honoraria. Radsak:Celgene: Research Funding. Hankin:Acceleron Pharma: Employment, Equity Ownership. Wilson:Acceleron Pharma: Employment, Equity Ownership. Sherman:Acceleron Pharma: Employment, Equity Ownership. Attie:Acceleron Pharma: Employment, Equity Ownership.
7040 Background: Nilotinib is a highly selective Bcr-Abl tyrosine kinase inhibitor that is 30-fold more potent than imatinib. In a phase I trial, nilotinib demonstrated efficacy and favorable tolerability in these pts. These results expand upon the phase I experience Methods: This phase II open-label study was designed to evaluate the safety and efficacy of nilotinib in adult imatinib-resistant or - intolerant BC pts or pts with relapsed/refractory Ph+ALL. Primary endpoint was investigator assessment of best hematologic response for BC and complete response for Ph+ALL pts. Nilotinib was started at 400mg BID with escalation to 600mg BID if no adequate response. Results: Safety and efficacy data are reported for 120 BC (27 lymphoid, 87 myeloid, 6 unknown) and 41 Ph+ALL pts (37 active disease, 4 residual disease, 38 relapsed, 3 refractory). 60% of pts had >35% Ph+ metaphases for BC and 31% for Ph+ALL. Median ages was 54 yrs for BC and 46 yrs for Ph+ALL pts. Chromosomal abnormalities other than Ph+ were noted in 64 (53%) BC and 12 (29%) Ph+ALL pts. Extramedullary involvement was present in 44 (37%) BC and 3 (7%) Ph+ALL pts. Treatment is ongoing for 21 (18%) BC and 4 (10%) Ph+ALL pts. Majority of discontinuations were due to disease progression [61 (51%) in BC; 26 (63%) in Ph+ALL). Median treatment duration was 53 (1–441) and 72 (3–363) days for BC and Ph+ALL, respectively. Median dose intensity was 800mg/day for both pt groups. CHR was reported in 25 (21%) pts, marrow responses in 7 (6%) pts, and return to chronic phase in 10 (8%) pts. Complete response was reported in 10 (24%) Ph+ALL; of which, 1 patient had minimal residual disease. The most common Grade 3/4 AEs were thrombocytopenia (41%), neutropenia (28%), pneumonia (11%), and anemia (27%) in BC and thrombocytopenia (24%) in Ph+ALL pts. During study period death occurred in 9 (8%) BC and 3 (7%) Ph+ALL pts. No Ph+ALL pt developed CNS disease while on therapy. Conclusions: Nilotinib has significant clinical activity and is well tolerated in imatinib-resistant or -intolerant BC and relapsed/refractory Ph+ALL pts. Nilotinib represents an important new treatment option for these pts in which there remains a high unmet medical need. No significant financial relationships to disclose.
179 Background: Myeloproliferative neoplasms (MPNs), such as essential thrombocythemia (ET), are driven by neoplastic progenitor cells. The JAK2 V617F mutation can be detected in approximately 50% of patients (pts) with ET, and the JAK2 V617F allele burden can be used to measure the treatment-induced molecular response (MR) over time. Telomerase is upregulated in neoplastic progenitor cells and sustains indefinite replication. Imetelstat is a first in class, potent, specific inhibitor of telomerase which selectively distributes to bone marrow and inhibits thrombopoiesis. In vitro studies demonstrate that imetelstat selectively inhibits spontaneous megakaryocytic colony-forming unit (CFU-Meg) growth from the blood of pts with ET but not from healthy individuals. Phase I studies have demonstrated that imetelstat inhibits telomerase activity in pts at doses of 7.5 mg/kg and above. Therefore, unlike conventional cytoreductive therapy and JAK2 kinase inhibitors, imetelstat may be uniquely able to selectively inhibit proliferation of neoplastic clonogenic cells in pts with ET and modify the biology and progression of the disease. Methods: A phase II study enrolled pts with ET who had failed or were intolerant to at least one prior therapy, or who refused standard therapy. Pts were treated with imetelstat 7.5 mg/kg or 9.4 mg/kg IV weekly. After attainment of best platelet response in the induction phase, maintenance dosing with imetelstat was commenced with dosing based upon platelet count. Primary endpoint was best overall hematologic response (HR) with complete response (CR) defined as platelet count <400 × 103/μl maintained for at least 4 consecutive weeks in the absence of new thromboembolic events. A key secondary endpoint was rate of MR in patients with JAK2 V617F molecular mutations. JAK2 V617F allele burden was measured by allele-specific quantitative real-time PCR with a limit of detection of 0.1%. CFU-Meg growth pre- and post-treatment and tolerability were also assessed. Results: As of July 9, 2012, 13 pts were treated. Median age was 60 yrs (range 21–83) with a median of 2 prior treatments (range 1–3). Median years since initial diagnosis were 5.8 (range 0.3 to 24.9) and initial platelet count was 809 × 103/μl (range 601 to 1359 × 103/μl). Best overall HR was 100%, with 11 of 13 pts achieving a confirmed CR after a median of 6.1 weeks (range 5.1 to 14.1 wks). Twelve of 13 pts remain on maintenance therapy (median time on study 26.1 weeks) and despite transient elevations of platelets above best response, pts continue to be responsive to imetelstat. Four pts have reached 1 year of therapy and continue to be treated with ongoing HR. Dosing frequency on maintenance therapy was generally reduced with time. A substantial decrease in JAK2 V617F allele burden was demonstrated in all 5 JAK2 V617F-positive pts (mean allele burden reduction of 82%; range of 59–94%, see table below). Four pts who were eligible for MR assessment by LeukemiaNetcriteria (initial JAKV617F allele burden >10%) reached molecular partial responses (PR): one pt after 12 weeks, which has been maintained through 1 year, and 3 other pts at 24, 36 and 48 weeks of therapy. One additional pt with JAK2 V617F levels of 4.8% prior to therapy has also had a 75% reduction after 12 weeks of treatment. A reduction in the spontaneous growth of CFU-Meg was also observed in the 2 pts tested, with 93% and 96% reduction from baseline, respectively. Long-term administration of imetelstat was generally well tolerated. Common adverse events reported on therapy were mild to moderate gastrointestinal toxicities, reductions in neutrophil counts, and fatigue. Conclusions: Imetelstat rapidly induces and maintains hematologic responses in pts with ET who have failed or are intolerant to conventional therapies. Importantly, substantial MR is observed in all JAK2 V617F-positive pts and inhibition of the neoplastic clonogenic growth ex-vivo is demonstrated. The reduction in JAK2 V617F allele burden and cytokine-independent growth of CFU-Meg suggests that imetelstat has a relatively selective inhibitory effect on the growth of the neoplastic clone(s) which drive ET and has the potential to modify the underlying biology of MPNs. Additional data will be presented from this ongoing study. Disclosures: Baerlocher: Geron Corporation: Research Funding. Oppliger Leibundgut:Geron Corporation: Research Funding. Ayran:Geron Corporation: Employment. Blaney:Geron Corporation: Employment. Burington:Geron Corporation: Employment. Morfeld:Geron Corporation: Employment. Odenike:Sanofi Aventis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees. Reddy:Geron Corporation: Employment. Roeth:Geron Corporation: Research Funding. Stuart:OncoMed Pharmaceuticals: Consultancy; Geron Corporation: Consultancy, Employment.
6528 Background: Dasatinib (D) (BMS-354825) is a multi-targeted kinase inhibitor of BCR-ABL and SRC. Preliminary data from a phase I study suggest high efficacy of D in IM pretreated pts. Methods: START L is an open label phase II study of D in IM-R or IM-I pts with LB-CML and Ph+ALL conducted at 42 centers worldwide. D was given orally, 70 mg twice a day (bid), with escalation to 100 mg bid for poor response or reductions to 50 mg and 40 mg bid for toxicity. Pts had weekly blood counts and monthly bone marrow exams, including cytogenetics. The primary endpoint was confirmed (sustained for at least 4 weeks) major hematologic response (MaHR) rates. Results: From January to June 2005, 101 pts were accrued. Data are available on the first 78 treated pts (42 LB-CML, 36 Ph+ALL). Of the 42 LB-CML pts, 37 were IM-R, 52% were male with median (med) age of 47 years. Prior therapy included IM >600 mg/day in 52% and stem-cell transplant (SCT) in 33% of pts. Med baseline platelet (plt) count was 32.5/nl, med BM blasts were 82%, Bcr-Abl mutations were seen in 48%, and extramedullary disease (EMD) was seen in 29% of pts. The D dose was reduced in 14%, temporarily interrupted in 33%, and escalated in 26% of pts. At 6-months, the MaHR rate was 31% including 26% complete hematologic response (CHR), the MCyR rate was 50%, and 17% of pts remained on study. Of the 36 Ph+ALL pts, 34 were IM-R, 64% were male with med age 46 years. Prior therapy included IM> 600 mg/day in 47% and SCT in 42% of pts. Baseline plt count was 53.5/nl, med BM blasts were 69%, Bcr-Abl mutations were seen in 47% and EMD was seen in 31% of pts. The D dose was reduced in 28%, temporarily interrupted in 39%, and escalated in 47% of the pts. At 6-months, the MaHR rate was 42% including 31% CHR, the MCyR rate was 58%, and 33% pts remained on study. Among all 78 pts, grade 3–4 thrombocytopenia and neutropenia was seen in 82% and 76% of pts, respectively. The most frequent D-related non-hematologic toxicities were diarrhea (30%), nausea (23%), fatigue (19%), rash (17%) and pleural effusion (13%). Conclusions: D is active in IM pretreated LB-CML and Ph+ALL pts. Data on all 101 pts will be presented at the meeting. [Table: see text]
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