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Anti-CD38 monoclonal antibodies have consistently shown increased efficacy when added to standard of care for patients with multiple myeloma. We aimed to assess the efficacy of isatuximab in addition to lenalidomide, bortezomib, and dexamethasone in patients with newly diagnosed transplantation-eligible multiple myeloma.This open-label, multicentre, randomised, active-controlled, phase 3 trial was done at 67 academic and oncology practice centres in Germany. This study is ongoing and divided into two parts; herein, we report results from part 1. Eligible patients were aged 18-70 years; had a confirmed diagnosis of untreated multiple myeloma requiring systemic treatment and a WHO performance status of 0-2; and were eligible for induction therapy, high-dose melphalan and autologous haematopoietic stem-cell transplantation, and maintenance treatment. Patients were randomly assigned (1:1) to receive three 42-day cycles of induction therapy either with isatuximab plus lenalidomide, bortezomib, and dexamethasone (isatuximab group) or lenalidomide, bortezomib, and dexamethasone alone (control group) using a web-based system and permuted blocks. Patients in both groups received lenalidomide (25 mg orally on days 1-14 and 22-35), bortezomib (1·3 mg/mBetween Oct 23, 2018, and Sep 22, 2020, 660 patients were included in the ITT analysis (331 in the isatuximab group and 329 in the control group). 654 (99%) patients were White, two were African, one was Arabic, and three were Asian. 250 (38%) were women and 410 (62%) were men. The median age was 59 years (IQR 54-64). MRD negativity after induction therapy was reached in 166 (50%) patients in the isatuximab group versus 117 (36%) in the control group (OR 1·82 [95% CI 1·33-2·48]; p=0·00017). Median follow-up time from start to end of induction therapy was 125 days (IQR 125-131) versus 125 days (125-132). At least one grade 3 or 4 adverse event occurred in 208 (63%) of 330 patients versus 199 (61%) of 328 patients. Neutropenia of grade 3 or 4 occurred in 77 (23%) versus 23 (7%) patients and infections of grade 3 or 4 occurred in 40 (12%) versus 32 (10%) patients. Among 12 deaths during induction therapy, one death due to septic shock in the isatuximab group and four deaths (one cardiac decompensation, one hepatic and renal failure, one cardiac arrest, and one drug-induced enteritis) in the control group were considered treatment-related.Addition of isatuximab to lenalidomide, bortezomib, and dexamethasone for induction therapy improved rates of MRD negativity with no new safety signals in patients with newly diagnosed transplantation-eligible multiple myeloma.Sanofi and Bristol Myers Squibb (Celgene).

Supplementary Figure S2. Phosphorylation levels of JAK1 and JAK3 were not affected by ruxolitinib.

Supplementary Table 2 from DNA Methylation of Tumor Suppressor Genes in Clinical Remission Predicts the Relapse Risk in Acute Myeloid Leukemia

Supplementary Table 1 from DNA Methylation of Tumor Suppressor Genes in Clinical Remission Predicts the Relapse Risk in Acute Myeloid Leukemia

Supplementary Figure Legend

Epigenetic changes play an important role in leukemia pathogenesis. DNA methylation is among the most common alterations in leukemia. The potential role of DNA methylation as a biomarker in leukemia is unknown. In addition, the lack of molecular markers precludes minimal residual disease (MRD) estimation for most patients with hematologic malignancies. We analyzed the potential of aberrant DNA promoter methylation as a biomarker for MRD in acute leukemias. Quantitative real-time PCR methods with bisulfite-modified DNA were established to quantify MRD based on estrogen receptor α (ERα) and/or p15INK4B methylation. Methylation analyses were done in >370 DNA specimens from 180 acute leukemia patients and controls. Methylation of ERα and/or p15INK4B occurred frequently and specifically in acute leukemia but not in healthy controls or in nonmalignant hematologic diseases. Aberrant DNA methylation was detectable in >20% of leukemia patients during clinical remission. In pediatric acute lymphoblastic leukemia, methylation levels during clinical remission correlated closely with T-cell receptor/immunoglobulin MRD levels (r = +0.7, P < 0.01) and were associated with subsequent relapse. In acute myelogenous leukemia patients in clinical remission, increased methylation levels were associated with a high relapse risk and significantly reduced relapse-free survival (P = 0.003). Many patients with acute leukemia in clinical remission harbor increased levels of aberrant DNA methylation. Analysis of methylation MRD might be used as a novel biomarker for leukemia patients' relapse risk. [Cancer Res 2007;67(3):1370–7]

Korrektur zu 10.1038/s41375-020-0826-9

Standard first-line therapy of chronic myeloid leukemia is treatment with imatinib. In the randomized German Chronic Myeloid Leukemia-Study IV, more potent BCR-ABL inhibition with 800 mg ('high-dose') imatinib accelerated achievement of a deep molecular remission. However, whether and when a de-escalation of the dose intensity under high-dose imatinib can be safely performed without increasing the risk of losing deep molecular response is unknown. To gain insights into this clinically relevant question, we analyzed the outcome of imatinib dose reductions from 800 mg to 400 mg daily in the Chronic Myeloid Leukemia-Study IV. Of the 422 patients that were randomized to the 800 mg arm, 68 reduced imatinib to 400 mg after they had achieved at least a stable major molecular response. Of these 68 patients, 61 (90%) maintained major molecular remission on imatinib at 400 mg. Five of the seven patients who lost major molecular remission on the imatinib standard dose regained major molecular remission while still on 400 mg imatinib. Only two of 68 patients had to switch to more potent kinase inhibition to regain major molecular remission. Importantly, the lengths of the intervals between imatinib high-dose treatment before and after achieving major molecular remission were associated with the probabilities of maintaining major molecular remission with the standard dose of imatinib. Taken together, the data support the view that a deep molecular remission achieved with high-dose imatinib can be safely maintained with standard dose in most patients. Study protocol registered at clinicaltrials.gov 00055874.

Leukemia : normal and malignant hemopoiesis 30(6), 1255-1262 (2016). doi:10.1038/leu.2016.20, Published by Nature Publ. Group, Basingstoke

Ruxolitinib is a small-molecule inhibitor of the JAK kinases, which has been approved for the treatment of myelofibrosis, a rare myeloproliferative neoplasm (MPN), but clinical trials are also being conducted in inflammatory-driven solid tumors. Increased infection rates have been reported in ruxolitinib-treated patients, and natural killer (NK) cells are immune effector cells known to eliminate both virus-infected and malignant cells. On this basis, we sought to compare the effects of JAK inhibition on human NK cells in a cohort of 28 MPN patients with or without ruxolitinib treatment and 24 healthy individuals. NK cell analyses included cell frequency, receptor expression, proliferation, immune synapse formation, and cytokine signaling. We found a reduction in NK cell numbers in ruxolitinib-treated patients that was linked to the appearance of clinically relevant infections. This reduction was likely due to impaired maturation of NK cells, as reflected by an increased ratio in immature to mature NK cells. Notably, the endogenous functional defect of NK cells in MPN was further aggravated by ruxolitinib treatment. In vitro data paralleled these in vivo results, showing a reduction in cytokine-induced NK cell activation. Further, reduced killing activity was associated with an impaired capacity to form lytic synapses with NK target cells. Taken together, our findings offer compelling evidence that ruxolitinib impairs NK cell function in MPN patients, offering an explanation for increased infection rates and possible long-term side effects associated with ruxolitinib treatment. Cancer Res; 75(11); 2187–99. ©2015 AACR.

Epigenetic changes play an important role in leukemia pathogenesis. DNA methylation is among the most common alterations in leukemia. The potential role of DNA methylation as a biomarker in leukemia is unknown. In addition, the lack of molecular markers precludes minimal residual disease (MRD) estimation for most patients with hematologic malignancies. We analyzed the potential of aberrant DNA promoter methylation as a biomarker for MRD in acute leukemias. Quantitative real-time PCR methods with bisulfite-modified DNA were established to quantify MRD based on estrogen receptor α (ERα) and/or p15INK4B methylation. Methylation analyses were done in >370 DNA specimens from 180 acute leukemia patients and controls. Methylation of ERα and/or p15INK4B occurred frequently and specifically in acute leukemia but not in healthy controls or in nonmalignant hematologic diseases. Aberrant DNA methylation was detectable in >20% of leukemia patients during clinical remission. In pediatric acute lymphoblastic leukemia, methylation levels during clinical remission correlated closely with T-cell receptor/immunoglobulin MRD levels (r = +0.7, P < 0.01) and were associated with subsequent relapse. In acute myelogenous leukemia patients in clinical remission, increased methylation levels were associated with a high relapse risk and significantly reduced relapse-free survival (P = 0.003). Many patients with acute leukemia in clinical remission harbor increased levels of aberrant DNA methylation. Analysis of methylation MRD might be used as a novel biomarker for leukemia patients' relapse risk. [Cancer Res 2007;67(3):1370–7]

Internal tandem duplications (ITDs) of the juxtamembrane region of the FLT3 tyrosine kinase receptor are the most frequent genetic alterations in acute myeloid leukemia (AML). The presence of this mutation has been recognized as an independent poor prognostic factor. In this study, we compared the FLT3 mutational status between diagnosis and subsequent relapses in 31 patients with AML. At diagnosis, seven patients were identified to contain FLT3-ITD mutations and one patient to harbor the D835 mutation. Five patients remained FLT3-ITD positive throughout the disease course (+/+). Three patients lost the FLT3 gene mutation at first (one FLT3-ITD, one D835 mutation), or second relapse (one FLT3-ITD) (+/-). One additional patient lost a small FLT3-ITD positive clone at relapse and at the same time gained an apparently unrelated FLT3-ITD positive clone. One patient without FLT3 mutation at diagnosis relapsed with an FLT3-ITD mutation (-/+). A shorter median duration of first remission (6 months versus 11.5 months) and a higher relapse rate after salvage therapy (e.g. allogeneic peripheral blood stem cell transplantation) resulted in a lower leukemia-free survival in the FLT3 mutated group (11% versus 31%). The loss of a clone with a mutation in the FLT3 gene at relapse did not improve the prognosis.

Nongestational choriocarcinomas are rare tumors. In the gastrointestinal tract, they are characterized by a biphasic tumor growth with separated areas of adenocarcinomatous and choriocarcinomatous differentiation. We here report a case of a combined adenocarcinoma-choriocarcinoma of the rectum. The tumor showed an aggressive clinical behavior with metastasis to the liver and lungs. A transient partial remission was achieved after 4 cycles of cisplatinum, etoposide, and ifosfamide chemotherapy, with normalization of serum beta-human chorionic gonadotropin levels. At this time, viable residual choriocarcinoma cells were found in surgically resected lung metastasis. The patient succumbed 8 months after initial diagnosis to a rapid abdominal relapse. We used comparative genomic hybridization (CGH) and fluorescence in situ hybridization to elucidate the genetic relationship of adenocarcinoma and choriocarcinoma in this neoplasm. We found genetic changes characteristic for colorectal adenocarcinomas, a loss of chromosomal regions 8p21-pter as well as 18q21-pter, and a gain of 5p and 20q, in both tumor parts. This provides evidence for the common origin of both components. A differential pattern of additional genetic changes suggests a clonal evolution from a common ancestor cell. In contrast to findings from a comparative study on a choriocarcinoma of the renal pelvis, we did not find an amplification of the germ cell cancer-associated chromosomal region 12p11.2-p12.1 in the areas of choriocarcinoma but found instead a loss of Xp11.3-pter. To our knowledge, this is the first report of a CGH comparison of the adenocarcinomatous and choriocarcinomatous tumor parts in a nongestational choriocarcinoma of the gastrointestinal tract.

Transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha) is mutated in 6-10% of patients with acute myeloid leukaemia (AML). Recently, we reported the emergence of an N-terminal C/EBPalpha mutation after chemotherapy in a patient with secondary AML. The clone carrying the mutation became the dominant clone at relapse. This observation prompted us to compare the C/EBPalpha mutational status of 26 de novo non-core binding factor AML patients at diagnosis and at relapse after induction and consolidation chemotherapy. Four mutations in the C/EBPalpha gene were identified in two out of 26 patients. In both these cases, a biallelic mutation was present at diagnosis and at relapse: an amino-terminal frameshift mutation and a mutation of the fork/leucine finger 1 region. In patient 1, the amino-terminal frameshift mutation was duplicated and found on both alleles at relapse. In patient 2, the amino-terminal frameshift mutation and a mutation in the fork region were found either alone or combined on the same allele, suggesting a subclone formation. None of the patients without a C/EBPalpha mutation at diagnosis showed a mutation at relapse. This is the first report of an evolution of the C/EBPalpha gene between diagnosis and relapse in AML.

Background Chronic myeloid leukemia (CML)-study IV was designed to explore whether treatment with imatinib (IM) at 400mg/day (n=400) could be optimized by doubling the dose (n=420), adding IFN (n=430) or cytarabine (n=158) or using IM after IFN-failure (n=128). Methods From July 2002 to March 2012, 1551 newly diagnosed patients in chronic phase were randomized into a 5-arm study. The study was powered to detect a survival difference of 5% at 5 years. The impact of patients' and disease factors on survival was prospectively analyzed. At the time of evaluation, at least 62% of patients still received imatinib, 26.2% were switched to 2nd generation tyrosine kinase inhibitors. Results After a median observation time of 9.5 years, 10-year overall survival was 82%, 10-year progression-free survival 80% and 10-year relative survival 92%. In spite of a faster response with IM800mg, the survival difference between IM400mg and IM800mg was only 3% at 5 years. In a multivariate analysis, the influence on survival of risk-group, major-route chromosomal aberrations, comorbidities, smoking and treatment center (academic vs. other) was significant in contrast to any form of initial treatment optimization. Patients that reached the response milestones 3, 6 and 12 months, had a significant survival advantage of about 6% after 10 years regardless of therapy. The progression probability to blast crisis was 5.8%. Blast crisis was proceeded by high-risk additional chromosomal aberrations. Conclusions For responders, monotherapy with IM400mg provides a close to normal life expectancy independent of the time to response. Survival is more determined by patients' and disease factors than by initial treatment selection. Although improvements are also needed for refractory disease and blast crisis, more life-time can currently be gained by carefully addressing non-CML determinants of survival. Disclosures Hehlmann: Novartis: Research Funding; BMS: Consultancy. Saussele: Pfizer: Honoraria; Incyte: Honoraria; Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding. Pfirrmann: BMS: Honoraria; Novartis: Honoraria. Krause: Novartis: Honoraria. Baerlocher: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria. Bruemmendorf: Novartis: Research Funding. Müller: Novartis: Honoraria, Research Funding; BMS: Honoraria, Research Funding; Ariad: Honoraria, Research Funding; Pfizer: Honoraria, Research Funding. Jeromin: MLL Munich Leukemia Laboratory: Employment. Hänel: Roche: Honoraria; Novartis: Honoraria. Burchert: BMS: Honoraria. Waller: Mylan: Consultancy, Honoraria. Mayer: Eisai: Research Funding; Novartis: Research Funding. Link: Novartis: Honoraria. Scheid: Novartis: Honoraria. Schafhausen: Novartis: Honoraria; BMS: Honoraria; Pfizer: Honoraria; Ariad: Honoraria. Hochhaus: Incyte: Research Funding; MSD: Research Funding; Pfizer: Research Funding; Novartis: Research Funding; BMS: Research Funding; ARIAD: Research Funding.

Human C/EBPepsilon is a recently cloned member of the C/EBP family of transcriptional factors. Previous studies demonstrated that the expression of this gene is tightly regulated in a tissue-specific manner; it is expressed almost exclusively in myeloid cells. To understand the mechanism by which the expression of C/EBPepsilon gene is controlled, we cloned a large genomic region surrounding the C/EBPepsilon gene and performed a DNase I hypersensitivity analysis of this locus. These sites probably represent areas of binding of proteins modulating gene transcription. Hypersensitive (HS) regions in 30 kb of DNA surrounding the C/EBPepsilon gene were examined in C/EBPepsilon high-expressing (NB4, HL-60), low-expressing (Jurkat), very-low-expressing (KG-1), and non-expressing (K562) hematopoietic cells as well as in non-hematopoietic-non-expressing cells (MCF-7, DU 145, PC-3). Three HS sites were detected near the first exon of C/EBPepsilon gene. They were found only in hematopoietic cells and were especially prominent in C/EBPepsilon expressing cells, suggesting that these sites play an important role in transcribing the gene. These hypersensitive bands did not change when the cells were cultured with retinoids. Gel-shift assays using 200 bp of nucleotide sequences that encompassed the hypersensitive sites and nuclear extracts from NB4 and Jurkat cells (C/EBPepsilon expressing) as well as K562 and MCF-7 cells (non-expressing) showed different retarded bands on gel electrophoresis. A fourth HS site, located about 11 kb upstream of exon 1, was found only in cells highly expressing C/EBPepsilon. Two sites, one about 4.5 kb upstream of exon 1 and another about 8.5 kb downstream of exon 2, were positive only in non-expressing cell lines, suggesting that repressors may bind in these areas. Taken together, we have found six specific DNase I hypersensitive sites in the region of C/EBPepsilon that may be involved in regulating transcription of this gene.

Platelet production is primarily regulated by the thrombopoietic cytokine thrombopoietin (TPO). In most cases thrombopoietin serum levels are determined by the rate of c-mpl receptor-mediated degradation after TPO uptake into platelets and megakaryocytes. The contribution of increased TPO protein synthesis by a translational mechanism was recently appreciated as the cause for hereditary thrombocythemia and will have to be elucidated in other conditions of thrombocytosis in association with increased TPO levels.

Cyclin A1 differs from other cyclins in its highly restricted expression pattern. Besides its expression during spermatogenesis, cyclin A1 is also expressed in hematopoietic progenitor cells and in acute myeloid leukemia. We investigated mechanisms that might contribute to cyclin A1 expression in hematopoietic cells. Comparison of cyclin A1 and cyclin A promoter activity in adherent and myeloid leukemia cell lines showed that the cyclin A1 promoter is preferentially active in myeloid cell lines. This preferential activity was present in a small, 335-bp cyclin A1 promoter fragment that contained several potential c-myb binding sites. Coexpression of a c-myb expression vector with the cyclin A1 promoter constructs significantly increased the reporter activity in adherent CV-1 as well as in myeloid U937 cells. Gel-shift assays demonstrated that c-myb could bind to the cyclin A1 promoter at a binding site located near the transcription start site. Site-directed mutagenesis of this site decreased promoter transactivation by 50% in both KCL22 cells that express high levels of c-myb and in CV-1 cells that were transfected with c-myb. In addition, transfection of primary human embryonic fibroblasts with a c-myb expression vector led to induction of the endogenous cyclin A1 gene. Taken together, c-myb can directly transactivate the promoter of cyclin A1, and c-myb might be involved in the high-level expression of cyclin A1 observed in acute myeloid leukemia. These findings suggest that c-myb induces hematopoiesis-specific mechanisms of cell cycle regulation.

Controversy exists as to whether Kaposi's sarcoma–associated herpesvirus (KSHV) is more widespread than originally reported. Recently, Monini et al reported that KSHV is ubiquitous in urogenital and prostate tissues and sperm of healthy Italian adults using nested polymerase chain reaction (PCR). We have examined for the presence of KSHV in 10 normal prostates from Italian men and 10 from men from the United States, as well as 32 prostatic, 30 vulvar, 24 ovarian, 20 cervical, and 30 testicular cancer specimens from patients from the United States. None of the patients had a history of human immunodeficiency virus infection. The samples were tested by nested PCR. The sensitivity of this assay was determined by a dilution study performed by diluting KSHV DNA from the KS-1 cells (a primary effusion lymphoma cell line which is estimated to have 16 copies of KSHV per cell) in DNA from a K562 myeloid cell line. The nested PCR that we used can detect 2.4 copies of KSHV sequences on a background of K562 DNA. All the samples were negative for KSHV sequences. Therefore, we cannot confirm the finding that KSHV sequences are ubiquitous in urogenital and prostate tissues. Furthermore, because our samples were from both the United States and Italy, the discrepancy between results is unlikely to be explained by either ethnic or environmental factors. False-positive results easily occur using nested primer PCR because of contamination. Our data argue that KSHV is not widely disseminated in urogenital tissues from nonimmunosuppressed individuals.

Acute myeloid leukemia (AML) is a heterogenous disease according to morphology, immunophenotype, and genetics. The retained capacity of differentiation is the basis for the phenotypic classification of the bulk population of leukemic blasts and the identification of distinct subpopulations. Within the hierarchy of hematopoietic development and differentiation it is still unknown at which stage the malignant transformation occurs. It was our aim to analyze the potential involvement of cells with the immunophenotype of pluripotent stem cells in the leukemic process by the use of cytogenetic and cell sorting techniques. Cytogenetic analyses of bone marrow aspirates were performed in 13 patients with AML (11 de novo and 2 secondary) and showed karyotype abnormalities in 10 cases [2q+, +4, 6p, t(6:9), 7, +8 in 1 patient each and inv(16) in 4 patients each]. Aliquots of the samples were fractionated by fluorescence-activated cell sorting of CD34+ cells. Two subpopulations, CD34+/CD38-(early hematopoietic stem cells) and CD34+/CD38+ (more mature progenitor cells), were screened for karyotype aberations as a marker for leukemic cells. Clonal abnormalities and evaluable metaphases were found in 8 highly purified CD34+/CD38-populations and in 9 of the CD34+/CD38-specimens, respectively. In the majority of cases (CD34+/CD38-, 6 of 8 informative samples; CD34+/CD38+, 5 of 9 informative samples), the highly purified CD34+ specimens also contained cytogenetically normal cells. Secondary, progression-associated chromosomal changes (+8, 12) were identified in the CD34+/CD38-cells of 2 patients. We conclude that clonal karyotypic abnormalities are frequently found in the stem cell-like (CD34+/CD38-) and more mature (CD34+/CD38+) populations of patients with AML, irrespective of the phenotype of the bulk population of leukemic blasts and of the primary or secondary character of the leukemia. Our data suggest that, in AML, malignant transformation as well as disease progression may occur at the level of CD34+/CD38-cells with multilineage potential.

An inherent defect of erythroid differentiation at the colony-forming unit blast (CFU-blast) compartment and (or) an impaired response of early erythroid progenitors (BFU-E) to growth stimulation are both considered to contribute to anemia in myelodysplastic syndromes (MDS). With the intention of improving survival and growth of early erythroid progenitors we investigated the effect of stem-cell factor (SCF) and interleukin-3 (IL-3) alone and in combination with erythropoietin, on the in vitro erythropoiesis of 13 patients with MDS and of three normal controls. SCF and IL-3 alone did not promote erythroid colony growth in MDS, while 3 cases responded to erythropoietin alone. In each of these, BFU-E colony growth could be increased by SCF, which was also found in all normal bone marrows. Altogether 6 cases showed a significant enhancement of BFU-E colony numbers by the combination of SCF and erythropoietin as compared to erythropoietin alone (P = 0.036). Out of the 6 responding cases, 5 belonged to the FAB-classified subgroups refractory anemia (RA) and refractory anemia with ringed sideroblasts (RA/RS) (5/5), while 1 patient was classified as having refractory anemia with excess of blasts (RAEB) (1/4). No patient with refractory anemia with excess of blasts in transformation (RAEB-T) (0/4) responded. In spite of these positive effects, the absolute number of BFU-E colonies remained reduced in all MDS cases when compared to normal controls. IL-3 proved ineffective in increasing the response to erythropoietin in MDS although it increased erythropoietin-induced BFU-E formation in normal controls significantly. We conclude that the striking synergistic effect of SCF and erythropoietin on erythroid colony formation seen with normal bone marrow is conserved in most cases with RA and RA/RS. In RAEB and RAEB-T the intrinsic defect of the erythroid differentiation pathway cannot be overcome by SCF.

Immunosuppression has recently been proposed for low-risk myelodysplastic syndromes (MDS) to reverse bone marrow failure by inhibiting intramedullary secretion of proapoptotic cytokines. We treated 35 MDS patients (24 refractory anaemia (RA), 10 RA with excess blasts and one chronic myelomonocytic leukaemia) with either horse antithymocyte globulin 15 mg/kg/day or rabbit antithymocyte globulin 3.75 mg/kg/day, each for 5 days. Median age was 63 years (range: 41-75). After 1 to 34+ months of follow-up (mean: 15+), four patients experienced complete haematological responses (CR), six good responses (GR) and two minor responses. All CRs and GRs occurred in patients with RA, in whom both horse and rabbit ATG yielded five responses out of 12 (42%). Time to response varied between 1 and 10 (mean: 3) months. The median duration of response was 9+ (1-17+) months; five patients are in continuing response. In all, 23 patients suffered side effectsdegrees II WHO (the degree of toxicity encountered according to the internationally accepted WHO toxicity grading); one patient died 2 weeks after rabbit ATG from rhinocerebral mucormycosis. Parameters that correlated with response were duration of disease and RA subgroup. In our experience, immune-modulating therapy with either horse or rabbit ATG is feasible in patients with RA and short duration of disease.

Transcription factor CCAAT/enhancer binding protein alpha (C/EBPalpha) is mutated in 6-10% of patients with acute myeloid leukaemia (AML). Recently, we reported the emergence of an N-terminal C/EBPalpha mutation after chemotherapy in a patient with secondary AML. The clone carrying the mutation became the dominant clone at relapse. This observation prompted us to compare the C/EBPalpha mutational status of 26 de novo non-core binding factor AML patients at diagnosis and at relapse after induction and consolidation chemotherapy. Four mutations in the C/EBPalpha gene were identified in two out of 26 patients. In both these cases, a biallelic mutation was present at diagnosis and at relapse: an amino-terminal frameshift mutation and a mutation of the fork/leucine finger 1 region. In patient 1, the amino-terminal frameshift mutation was duplicated and found on both alleles at relapse. In patient 2, the amino-terminal frameshift mutation and a mutation in the fork region were found either alone or combined on the same allele, suggesting a subclone formation. None of the patients without a C/EBPalpha mutation at diagnosis showed a mutation at relapse. This is the first report of an evolution of the C/EBPalpha gene between diagnosis and relapse in AML.

Introduction: Ruxolitinib (INCB018424) is the first JAK inhibitor approved for treatment of myelofibrosis (MF). Ruxolitinib-induced reduction of splenomegaly and symptoms control is linked to a substantial suppression of MF-associated circulating pro-inflammatory and pro-angiogenic cytokines. However, an increased rate of infections in ruxolitinib-exposed patients with MF was recently described. Natural killer (NK) cells are innate immune effector cells eliminating malignant or virus-infected cells. Thus, the aim of this project was to define in more detail the impact of JAK inhibition on NK cell biology both in vitro and in vivo. Methods: 28 patients with myeloproliferative neoplasms (MPN) with or without ruxolitinib therapy and 12 healthy donors were analyzed for NK cell frequency, NK receptor expression and function. Phenotypic and functional NK cell markers (e.g. CD11b, CD27, KIR, NKG2A, NKG2D, NKp46, CD16, granzyme B, and perforin) were analyzed by FACS. NK cell function was evaluated by classical killing assays upon stimulation with MHC class I-deficient target cells K562. Finally, a set of additional in vitro experiments (e.g. analysis of lytic synapse formation by FACS and confocal microscopy) were performed to define in more detail the characteristics and potential mechanisms of ruxolitinib-induced NK cell dysfunction. Results: In addition to our recent finding that ruxolitinib induces NK cell dysfunction in vitro (e.g. reduced killing, degranulation and IFN-γ production), we here demonstrate that NK cell proliferation and cytokine-induced receptor expression as well as cytokine signalling are drastically impaired by ruxolitinib. Interestingly, reduced killing is at least in part due to a reduced capacity to form a mature lytic synapse with target cells. The significance of the in vitrofindings is underscored by a dramatically reduced proportion and absolute number of NK cells in ruxolitinib-treated MPN patients when compared to treatment-naïve patients or to healthy controls (mean percentage of NK cell frequency: ruxolitinib-naïve MPN patients 12.63% ±1.81; healthy donors 13.51% ±1.44; ruxolitinib-treated patients 5.47% ±1.27). A systematic analysis of NK cell receptor expression revealed that the reduction of NK cells in ruxolitinib-exposed individuals is most likely due to an impaired NK cell differentiation and maturation process, as reflected by a significantly increased ratio of immature to mature NK cells. Finally, the endogenous functional NK cell defect in MPN is further aggravated by intake of the JAK inhibitor ruxolitinib. Conclusion: We here provide compelling in vitro and in vivo evidence that inhibition of the JAK/STAT-pathway by ruxolitinib exerts substantial effects on the NK cell compartment in MPN patients due to the inhibition of NK cell differentiation and NK cell key functions. Our data may help to better understand the increased rate of severe infections and complement recent reports on ruxolitinib-induced immune dysfunction. Disclosures Koschmieder: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Travel, Accomodation, Expenses Other. Brümmendorf:Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties, Research Funding. Wolf:Novartis: Consultancy, Honoraria, Research Funding, Travel and Accommodation Other.

Recently, mutations in the transcription factor CCAAT/ enhancer binding protein alpha (C/EBPalpha) have been described in acute myeloid leukemia (AML). We performed a mutational analysis of the C/EBPalpha gene in the myelodysplastic syndromes and AML with antecedent MDS. No mutations were found in patients with refractory anemia (0/27), refractory anemia with ringed sideroblasts (0/7), refractory anemia with excess of blasts (RAEB 0/16) or chronic myelomonocytic leukemia (CMML 0/5). One out of 13 patients with RAEB-T/AML secondary to MDS showed a mutation in the C/EBPalpha gene. In this patient a 4 bp insertion disrupted codon 69 in one allele. This novel +1 frame shift is predicted to result in a truncated protein of 107 amino acids. However, the dominant protein translated was the C/EBPalpha isoform p30, which was previously shown to inhibit the DNA-binding and transactivation properties of C/EBPalpha p42. Interestingly this mutation could not be detected at diagnosis in the initial RAEB and RAEB-T stage. The mutation appeared at relapse after chemotherapy for RAEB-T. We conclude that the C/EBPalpha mutation was not essential for the initial blast accumulation. The emergence of a bast clone carrying a C/EBPalpha mutation at relapse indicates that this mutation may confer a growth advantage in a myeloid cell with an established differentiation block.

A prospective, randomized, double-blind placebo-controlled trial was designed to evaluate the impact of granulocyte/macrophage-colony-stimulating factor (GM-CSF) on the efficacy of sequential high-dose cytosine arabinoside/mitoxantrone chemotherapy (S-HAM) in adult patients with high-risk myelodysplastic syndromes (MDS). GM-CSF or placebo was given subcutaneously once daily at a dose of 250 microg/m2, starting 48 h prior to chemotherapy, and continued until neutrophil recovery. Owing to high toxicity and slow patient recruitement the study was closed and unblinded after 31 patients had been enrolled; 15 were randomized to receive placebo and 16 to receive GM-CSF. A total of 29 patients were evaluable for response; their median age was 57 years. Ten patients achieved a complete remission (34.5%), 9 patients had persistent MDS (31%), 10 patients died within 6 weeks after the onset of treatment (early death) (34.5%). The median remission duration was 190 days (range: 2.5-45 months). Among the 29 evaluable patients no significant differences could be found between the two study arms regarding complete remission rate [GM-CSF: 31% (5/16) versus placebo: 38% (5/13) P = 0.45], rate of persistent MDS [GM-CSF: 25% (4/16) versus 38% (5/13) P = 0.35), early death rate [44% (7/16) versus 23% (3/13) P = 0.22] and remission duration (GM-CSF: 87 days versus placebo 221 days). Duration of granulocytopenia (median: 33 days with GM-CSF) versus 35 days with placebo) and frequency of infectious episodes were not significantly influenced by GM-CSF. The small number of patients finally analyzed means that no definite conclusions about the effect of GM-CSF can be reached.

Therapy for myelodysplastic syndromes (MDS) has been less than effective when based on low-dose treatment or supportive measures only, including hematopoietic growth factors. Recently, based on the percentage of bone marrow blasts, the number of cytopenic cell lines and cytogenetics, clinical risk groups have been defined more precisely. Recent studies applying intensive acute myeloid leukemia (AML)-type therapy to high-risk MDS have produced remissions ranging from 45 to 79%. Advances in the understanding of the biology of MDS clearly point to cytogenetics rather than morphologic subtype as being of prognostic relevance. Hence, new treatments need to be developed for patients with unfavorable karyotypes and complex abnormalities in particular. These MDS subtypes are characterized by low spontaneous proliferative activity and low autocrine production of hematopoietic growth factors. The subtypes are, however, highly sensitive to external stimulation by granulocyte-colony stimulating factor (G-CSF) and granulocyte macrophage-colony stimulating factor (GM-CSF). New therapies could emerge from these findings, for example, priming high-risk MDS patients with hematopoietic growth factors in combination with intensive AML-type treatment. Recent studies suggest that incorporating high-dose AraC into an intensive drug combination could further improve the outcome of high-risk MDS.

We report on a patient with Fanconi's anemia (FA) who developed a myelodysplastic syndrome (RAEB-T) with complex karyotypic abnormalities (trp 1q23q42, monosomy 20, trisomy 13) at the age of 28. The patient achieved a complete hematological and cytogenetic remission after treatment with sequential high-dose cytosine arabinoside/mitoxantrone followed by G-CSF (5 micrograms/kg). Bone marrow hypoplasia was prolonged with 38 days of granulocytopenia500/microliters and 62 days of platelet transfusion dependency. Nonhematological toxicity did not exceed that of patients without underlying FA. Remission duration was 7 months. This observation shows the feasibility of high-dose Ara C treatment in patients with FA and MDS. Although hematopoiesis remained clonal in remission, the suppression of the cytogenetically abnormal clones transiently reversed the antecedent long-lasting pancytopenia.

Thirty-one adult patients with high-risk myelodysplastic syndromes (MDS) were enrolled in a prospective randomized double-blind placebo-controlled trial evaluating the efficacy of sequential high-dose Ara C/mitoxantrone chemotherapy with or without GM-CSF. GM-CSF or placebo was given subcutaneously once daily at a dose of 250 micrograms/m2 starting 48 h prior to chemotherapy and continued until neutrophil recovery. This design allowed us to investigate the role of GM-CSF as a priming factor for the leukemic clone, as well as its effect on the recovery of normal hematopoiesis. Twenty-eight patients are currently evaluable for response. The patients reached a complete remission (36%), eight patients had persistent MDS (29%), and ten patients died within 6 weeks after the onset of treatment (early death). Infectious complications during cytopenia were the major cause of death (8/10). Median time to complete hematologic recovery (neutrophils500/microliter and platelets 20,000/microliter) and time to neutrophil recovery above 1500/microliter was 29 and 35 days, respectively. Median remission duration was 190 days (6.4 months). Analysis of prognostic subgroups showed a low CR rate (25%) and a high early-death rate (44%) in patients55 years of age, suggesting that the intensified treatment approach should be limited to younger patients. No data concerning the influence of GM-CSF on response to chemotherapy or duration of neutropenia are presently available.

The phenotype of the (pre)leukemic stem cell in AML and MDS has not been identified as yet. We have investigated whether cells with a stem cell-like immunophenotype (CD34+/CD38-) are involved in the leukemogenic process. In 12 patients with AML and in one patient with MDS the identification of (pre)leukemic cells was performed by classical cytogenetics. Highly purified (96-98% purity) cellular subpopulations were generated by fluoresence activated cell sorting according to the expression of CD34 and CD38. Following brief incubation with a cytokine cocktail (EPO, GCSF, GM-CSF, IL-3, SCF) the sorted subpopulations were processed for chromosome analysis. In 9/12 AML patients clonal karyotype abnormalities were observed in the unsorted material. In 7/9 cases the chromosomal changes found in unsorted specimens were also detected in the immature stem cell-like population (CD34+/CD38-). In 9/9 cases the karyotype abnormalities were diagnosed in the population of committed progenitors (CD34+/CD38+). Additional secondary abnormalities were also demonstrable in both subpopulations in a case of M4Eo with inv(16). In a patient with secondary MDS RA, 2 subpopulations, CD34+/CD38- and CD34+/CD38+, were sorted together (CD34+/ 38+ -) because of the rarity of available cells. Cytogenetic analysis revealed a mosaic of normal and abnormal cells with 5 different dependent cell clones. All abnormal cell clones were demonstrable in the CD34+, sorted cell population. The relevance of our findings for pathogenesis, autologous stem cell transplantation and targeted gene therapy are discussed.

Patients with high-risk myelodysplastic syndromes (MDS) face a poor prognosis with a median survival time of less than 12 months. The only curvative treatment known so far is allogeneic bone marrow transplantation which is available for younger patients with an HLA-matched sibling and hence for a minority of cases only. Acute myeloid leukemia (AML)-type combination chemotherapy can achieve complete remissions (CR) in the range of 15%–51%, however, remission duration is short (1, 2). Treatment failures are due to primary drug resistance and a high early death rate. The latter may be related to a longer duration of treatment-induced aplasia as compared to AML.

Background Pomalidomide (POM) in a 1-arm phase-1/-2 study and a randomized 4-arm phase-2 study in MPN-associated myelofibrosis improved anemia. Pomalidomide was evaluated at doses of 0.5 and 2.0 mg/d. Aims To evaluate efficacy of POM alone at two different doses and combined with prednisolone (PRED) in patients with MPN-associated myelofibrosis and cytopenia (ClinicalTrials.gov No. NCT00949364). Methods Main inclusion criteria were RBC-transfusion-dependence or hemoglobin Results 38 patients were treated in cohort-1 and 58 in cohort-2 (N=27, PRED-mo-4; N=31; PRED-mo-7). Median follow-up was 30 mo in cohort-1 and 10 mo in cohort-2. Median age was 72 y (range, 49-85 y). 34% were female, 72% had primary MF. Disease-stage at study-entry (DIPSS) was high-risk, 24%, intermediate-2 risk, 65% and intermediate-1 risk 12%; JAK2V617Fand MPLW515L were detected in 58% and 6% of patients; 76% of patients were RBC- and 17% platelet-transfusion-dependent. There were no significant differences in pretreatment characteristics between cohort-1 and cohort-2 or between the 2 arms of cohort-2. Median durations of POM treatment were 12, 8, and 4 mo, respectively. PRED was added in cohort-1 and in the PRED-month-4 as well as PRED-month-7 arms of cohort-2 in 50%, 59% and 26% of patients. Response-rates were: 34% (95%-CI, 21-50%), 19% (95%-CI, 8-37%) and 16% (95%-CI, 7-33%), respectively; p=0.086. Responses occurred after 6 mo (range, 1-15 mo), 7 mo (range, 1-12 mo) and 4 mo (range, 3-7 mo). Anemia responses were observed more frequently in cohort-1 (29% [95%-CI, 17-45%]) compared to cohort-2 (14% [95%-CI, 7-25%]; p=0.059). Platelet response in patients with platelets100/nL were achieved in 56% (95%-CI, 27-81%) and 25% (95%-CI, 9-53%; p=0.20). 13 patients (12 high risk) experienced blastic transformation; 4 patients developed solid neoplasms. Conclusions Response rate to POM at a dose of 2mg/d was higher compared to 0.5 mg/d. Early addition of PRED at 4 mo compared to 7 mo was associated with longer treatment duration. Disclosures: Schlenk: Novartis: Research Funding; Amgen: Research Funding; Chugai: Research Funding; Pfizer: Honoraria, Research Funding; Celgene: Honoraria, Research Funding; Ambit: Honoraria. Off Label Use: Pomalidomide in Myelofibrosis. Reiter:Sanofi: Honoraria. Gattermann:Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Hochhaus:Novartis: Consultancy, Honoraria, Research Funding, Travel Other; BMS: Consultancy, Honoraria, Research Funding; ARIAD: Consultancy, Honoraria; Pfizer: Consultancy. Platzbecker:Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Heidel:Novartis Inc.: Research Funding; Novartis Inc.: Honoraria.

Background In recent phase-I/II studies, pomalidomide (POM) has shown activity in myelofibrosis (MF) patients (pts) with anemia and/or thrombocytopenia. In the first cohort of the German multicenter MPNSG 01-09 phase-II trial, 38 MF pts were treated with POM 2 mg QD +/- prednisolone (PRED); 34% responded according to IWG-MRT criteria or became RBC-transfusion independent (Schlenk et al., ASH 2012). Additional 58 MF pts were treated in the second study cohort with POM 0.5 mg QD +/- PRED. Main inclusion criteria were age >50y, RBC-transfusion-dependency or Hb Aims To explore the presence of copy number alterations (CNAs), uniparental disomies (UPDs) and MPN-related gene mutations in the 01-09 study cohort and to correlate genetic parameters with treatment response. Methods Affymetrix 6.0 SNP arrays were used for genome-wide screening of CNAs and UPDs in 91% (87/96) of pts. Frequently mutated genes were analyzed in all pts using PCR-based techniques and sequence analysis of coding exons: JAK2 V617F, MPL W515L, ASXL1 (exon 12), EZH2 (exon 2-20), IDH1/2 (exons 4), SRSF2 (exon 1-2), and TP53(exon 4-10). Results In total, 78 CNAs were identified by SNP array analysis. The overall frequency of CNAs was 52% (45/87 pts); 24% (21 pts) showed ≥2 CNAs, while 7% (6 pts) had a complex genotype defined by ≥3 genomic aberrations. Recurrent large (>5 Mb) gains were trisomy 8 (7%; n=6), gain 1q, and trisomy 9 (5% each; n=4), whereas recurrent large losses were identified in 20q (11%; n=10), 5q (8%; n=7), 13q (7%; n=6), 7q/7 (6%; n=5), and 12p/12 (2%; n=2). Moreover, 20% (17/87) of pts showed 19 informative micro-deletions ( Large UPDs (>10 Mb) affecting a terminal end of the chromosome were present in 32% (28/87) of pts. The most frequent UPDs occurred in 9p including JAK2 (17%; n=15). Other recurrent UPDs mapped to 1p (5%; n=4), 4q, and 7q (2% each; n=2). UPDs in 9p were associated with JAK2 V617F in all pts, whereas 75% (3/4) of pts with UPD in 1p were MPLW515L mutated. Mutations in JAK2 (V617F) and MPL (W515L) were present in 55% (53/96) and 6% (6/96) of pts, respectively. The mutation frequencies for the remaining genes were 30% (ASXL1; n=29/96), 9% (SRSF2; n=9/96), 5% (EZH2; n=5/96), 2% (TP53; n=2/96), and 1% (IDH2; n=1/96). Taken together, at least one mutation was found in 79% (76/96) of pts, whereas 21% (20/96) of pts lacked any of these mutations; 28% (27/96) of pts showed ≥2 concurrent mutations. To evaluate genetic differences and predictive factors, pts were separated into a responder (R, n=23) and a non-responder (Non-R, n=73) group. Regarding DIPSS, Non-R pts were not associated with higher risk compared to R pts: 27% (20/73) high risk vs. 17% (4/23) (p=0.334), 61% (44/73) intermediate-II risk vs. 79% (18/23), and 12% (9/73) intermediate-I vs. 4% (1/23) (p=0.275). However, the overall frequency of CNAs was in trend higher in the Non-R group: 56% vs. 39% (p=0.159). Since the total number of genomic losses was similarly distributed (27% vs. 29%), the difference was mainly due to the higher frequency of large genomic gains/trisomies: 4% (R) vs. 22% (Non-R) (p=0.083). UPDs were similar frequent in R and Non-R pts (26% vs. 34%) (p=0.466). The total number of gene mutations was not different between both groups (n=25 in 23 R pts vs. n=77 in 73 Non-R pts) (p=0.475). However, genetic alterations being associated with unfavourable outcome were enriched in the Non-R group: ASXL1 mutation (39% vs. 22%), EZH2 mutation (5% vs. 0%), loss in 5q (30% vs. 4%), trisomy 8 (9% vs. 0%), 12p / ETV6 deletion (6% vs. 0%), 17p deletion / TP53 mutation (3% vs. 0%), and complex genotype (7% vs. 0%). Taken together, adverse genetic alterations were significantly more frequent in Non-R pts compared to R pts: 48% (35/73) vs. 22% (5/23) (p=0.026). Of note, adverse genetic alterations indicated high risk according to DIPSS in no more than 50% (12/24) of the pts. Conclusion Our study on a well-defined patient cohort with advanced MF revealed a high frequency of genetic alterations reflecting the molecular complexity of the disease. Pts with adverse genetic alterations identified by SNP-array and mutation analyses were not sufficiently represented by DIPSS and showed inferior response to POM +/- PRED. Disclosures: Reiter: Sanofi: Honoraria. Gattermann:Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Platzbecker:Celgene: Honoraria, Research Funding; Novartis: Honoraria, Research Funding. Hochhaus:Novartis: Consultancy, Honoraria, Research Funding, Travel Other; BMS: Consultancy, Honoraria, Research Funding; Pfizer: Consultancy, Honoraria; Ariad: Consultancy, Honoraria. Schlenk:Amgen: Research Funding; Pfizer: Research Funding; Novartis: Research Funding; Chugai: Research Funding; Ambit: Honoraria.

The expression of a “stem cell like” blast immunophenotype (CD34+/CD38−) has been associated with a poor prognosis in AML. Advanced myelodysplastic syndromes and secondary AML’s are another patient population with an inferior prognosis. We hypothesized that a stem cell origin of these disorders results in a higher incidence of a CD34+/CD38− blast immunophenotype. This could be biologically related to a higher chemoresistence. The data presented here shows that a “stem cell like” blast immunophenotype is rare in RAEB. In addition there is no significant difference between primary AML and secondary AML or RAEB-T.

Tumour cells from a patient with recurrent testicular germ cell cancer and bone marrow infiltration were found to express CD33 and CD34 in the absence of other haemopoiesis-associated antigens. After myelosuppression and treatment with G-CSF for stem cell mobilization, CD34-positive tumour cells were detected in the peripheral blood in addition to normal haemopoietic progenitor cells. The tumour cells were decreased in the leukapheresis product. Retrospectively, the appearance of tumour cells in the peripheral blood after stem cell mobilization was the first indication of impending relapse.

Abstract 2840 Background: Pomalidomide in a single arm phase-I/II study and one randomized four arm phase-II study in primary myelofibrosis (MF) and post-polycythemia vera/essential thrombocythemia (post-PV/ET) MF showed efficacy in particular with respect to improvement in anemia. To date, pomalidomide has been evaluated in MF at two dose levels, 0.5mg and 2.0 mg/day. Aims: To evaluate clinical efficacy of pomalidomide alone and in combination with prednisolone (PRED) in patients with primary or post-PV/ET MF and cytopenia. Methods: The main inclusion criteria for primary or post-PV/ET MF patients were red blood cell (RBC)-transfusion-dependence or hemoglobin =50 years were eligible. Treatment consisted of pomalidomide (POM) 2mg/day; prednisone (PRED) 30mg/day was added in patients who did not respond (≤ stable disease) within three months of therapy. The primary endpoint was response assessed by IWG criteria and extended by the criterion red blood cell transfusion-independence (Gale RP et al., Leuk Res. 2011). Concurrent hydroxyurea in patients with proliferative disease and aspirin 100 mg/d in patients with platelets between 50/nl and 1000/nl were administered. The statistical design of the study was based on the Simon optimal two-stage design. Here we report on the first stage of the study. Median follow-up according to the method of Korn was 18 months. Results: Thirty-eight patients were treated with POM 2 mg/d, the median age was 71 years (range 51–83), 34% were female. Twenty-seven had primary and 11 post-PV/ET MF. Disease stage at study-entry according to the DIPSS was high-risk in 13 (34%), intermediate-2 risk in 22 (58%) and intermediate-1 risk in 3 (8%). Incidence of high-risk cytogenetics, JAK2 V617F mutation and MPL W515L mutation were 29% (10/34), 55% (21/38) and 18% (7/38), respectively. Twenty-seven patients (71%) were RBC-transfusion- and 7 (18%) platelet-transfusion dependent. Median duration of treatment with POM was 11.4 months with 5 patients continue on treatment 24+ months. PRED was added after 3 months in 19 of 28 eligible patients. POM dose-reduction (n=8, 1mg/d; n=2, 0.5mg/d) was performed after a median time of 34 days (range 3–308 days) due to fatigue (n=2), thrombo- and/or neutropenia (n=7), rash (n=1). Seven patients with high risk characteristics (n=6 RBC-transfusion dependent, n=4 high risk cytogenetics) experienced transformation into blast phase (BP), the actuarial probability of transformation to BP measured from diagnosis was 6.0% (SE 4.1%) at 2 years and 22.4% (SE 8.4%) at 5 years. Response was observed in 14 patients (37%) after a median time of 4.8 months (n=1 complete remission, n=5 clinical improvement-platelets, n=3 clinical improvement-erythrocytes, n=5 red cell transfusion-independence); 8 responders received concomitant PRED and responded after a median of three months (range 0.8–11.7 months) of the addition of PRED. In 5 of 14 responders POM dose was reduced due to toxicity, notably before response occurred. Responses were observed within the first 3 months (n=4), between month 4 to 6 (n=4) and beyond month 6 (n=6) with the latest response seen at 12.7 months. There was no correlation between response and JAK2/MPL mutation status or cytogenetics. Basophilia defined as greater than 50% increase in absolute basophil count at month 3 was in trend associated with response (p=0.06). Conclusions: POM with or without PRED in patients with different risk groups of patients with primary and post-PV/ ET MF was effective with a response rate of 37%. Based on results of this first cohort the protocol was amended; i) POM dose has been adjusted to 0.5 mg/d, ii) up-front randomization of PRED at month 4 or month 7 in patients without response but stable disease to single agent POM was introduced. Disclosures: Schlenk: Celgene: Research Funding. Off Label Use: Pomalidomide is so far not approved for the treatment of primary and secondary myelofibrosis.

Four patients with myelodysplastic syndrome (MDS), one with t(1;7) and three with trisomy 8, were studied by immunophenotyping and fluorescence in situ hybridization (FISH) to assess cell lineage involvement. The t(1;7) was detected using a biotin-labeled chromosome 1 centromere-specific DNA probe. This aberration was present in CD34-positive stem cells, the erythroid cell lineage (GPA+), and the granulocytic/monocytic (CD13+ and CD64+) cell lineages. We were not able to demonstrate the abnormality in the lymphoid cell lineages. In the patients with trisomy 8, the aberration was detected with chromosome 8 centromere-specific DNA probe or by chromosome in situ suppression hybridization (CISS) with a chromosome 8-specific library probe. The trisomy was detected in stem cells, erythroid precursor cells, megakaryocytes, and granulocytes/monocytes. In these MDS patients, the chromosome aberrations appear to occur only in cells of myeloid lineage.