ALBERT

Beschreibung: Background: Prognosis of diffuse large B-cell lymphoma (DLBCL) and other aggressive lymphoma entities has improved with the advent of Rituximab, and R-CHOP-21 and variants is SOC. Nevertheless, a substantial proportion of patients fail first line treatment. Salvage therapies are often effective. However, no more than 25-50% achieve a long term remission even when consolidative high dose chemotherapy (HDT) followed by hematopoietic stem cell transplantation (SCT) is applied. In case of failure or intolerance to HDT, regimen like Gemcitabine/Oxaliplatin are applied but show limited efficacy, indicating the need for new treatments. Obinutuzumab (GA101) is a type II anti-CD20 antibody. Superiority of Obinutuzumab could be demonstrated in xenograft models of mantle cell lymphoma and DLBCL. Although desirable, cumulative dose-related, progressive cardiotoxicity eliminates anthracyclins from higher treatment lines. With Pixantrone, a drug structurally related to anthracyclines and especially anthracenediones, a re-exposition against this drug class has been shown to be feasible. In 70 heavily pre-treated patients, a best ORR of 40% (20% CR/CRu) was observed (Pettengell et al). Experiences from further antibody drug combinations lead to the assumption that the effects of Pixantrone will be augmented by a monoclonal antibody without increasing toxicity. We thus initiated a trial combining both agents for the first time. The trial has opened in Q4/2015 and recruitment is ongoing. Overall, a total of up 70 patients will be enrolled for a number of 64 evaluable patients. Primary endpoint will be the objective overall response rate, with secondary endpoints being safety, PFS and OS. Methods: this is a multicenter, national, prospective trial. Inclusion criteria: patients were eligible if they had histologically proven DLBCL, FL grade IIIb or transformed indolent lymphoma, CD20 positive disease, no curative option available, relapsed disease, measurable disease, ECOG 〈 3, sufficient bone marrow reserve, no severe concomitant diseases and given informed consent. There was no upper limit or prior treatment lines. Treatment consisted of Pixantrone 50mg/m² day 1, 8 and 15 of each cycle, Obinutuzumab 1000 mg flat dose day 1, 8 and 15 of cycle one and day 1 of each subsequent cycle. A total of 6 cycles was planned with interim staging after 3 cycles. Results: 24 patients (pts) have been included until now. Concerning clinical characteristics, all were caucasian, 12 were female and the other 12 male and median age was 75 years. Most of the patients suffered from DLBCL (18 pts, 82%). Median number of prior therapies was 2 (1 to 6). Until now 55 evaluable cycles of chemotherapy (median 2 cycles (0 to 6)) have been performed. At this time, the treatment seems to be well tolerated, with no unforeseen side effects. Observed toxicity was predominantly hematologic. The following hematologic adverse events of grade 3/4 were noted: leukopenia (4 pts, 17%), neutropenia (6 pts, 25%), granulocytopenia (1 pts, 4%), as well as thrombocytopenia (2 pts). Non-hematologic grade 3/4 adverse events were observed in at least two patients: hypertension (2 pts) and pelvic pain (2 pts). Response: currently, best responses were 4 PR, 1 SD, and 8 PD in 13 patients evaluable so far. Four patients died, all after progression of lymphoma. Summary: the combination of Obinutuzumab and Pixantrone seems to be feasible and safe with early signs of efficacy. Updated results of this trial in progress with a focus on safety will be presented. Disclosures Hess: Janssen: Honoraria; Novartis: Honoraria; Pfizer: Honoraria; Celgene: Honoraria; Roche, CTI, Pfizer, Celgene: Research Funding; Roche: Honoraria. Marks:Pfizer: Honoraria. Witzens-Harig:Roche: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Dreyling:Roche: Consultancy, Honoraria, Research Funding, Speakers Bureau. Viardot:Amgen: Consultancy; Janssen: Consultancy; BMS: Consultancy; Roche: Honoraria; Takeda: Other: travel support; Pfizer: Honoraria. Keller:Spectrum Pharmaceutical: Consultancy, Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Honoraria; Pfizer: Consultancy, Honoraria.

Beschreibung: Activating KRAS mutations are detected in a substantial number of hematologic malignancies. In a murine T-cell acute lymphoblastic leukemia (T-ALL) model, we previously showed that expression of oncogenic Kras induced a premalignant state accompanied with an arrest in T-cell differentiation and acquisition of somatic Notch1 mutations. These findings prompted us to investigate whether the expression of oncogenic KRAS directly affects DNA damage repair. Applying divergent, but complementary, genetic approaches, we demonstrate that the expression of KRAS mutants is associated with increased expression of DNA ligase 3α, poly(ADP-ribose) polymerase 1 (PARP1), and X-ray repair cross-complementing protein 1 (XRCC1), all essential components of the error-prone, alternative nonhomologous end-joining (alt-NHEJ) pathway. Functional studies revealed delayed repair kinetics, increased misrepair of DNA double-strand breaks, and the preferential use of microhomologous DNA sequences for end joining. Similar effects were observed in primary murine T-ALL blasts. We further show that KRAS-mutated cells, but not KRAS wild-type cells, rely on the alt-NHEJ repair pathway on genotoxic stress. RNA interference–mediated knockdown of DNA ligase 3α abolished resistance to apoptotic cell death in KRAS-mutated cells. Our data indicate that targeting components of the alt-NHEJ pathway sensitizes KRAS-mutated leukemic cells to standard chemotherapeutics and represents a promising approach for inducing synthetic lethal vulnerability in cells harboring otherwise nondruggable KRAS mutations.

Beschreibung: Background and Aims: Patients after allogeneic hematopoietic stem cell transplantation (HSCT) suffer from immunodeficiency, in part due to long-term immunosuppressive medication e.g. by calcineurin inhibitors like cyclosporine A (CsA). Additionally, these patients have an increased risk for opportunistic fungal infections like invasive aspergillosis (IA). The nuclear factor of activated T cells (NFAT) is known as an important transcription factor in signaling-pathways downstream of calcineurin in the adaptive immune systems, e.g. in T cells, but also plays an important role in innate immune response as indicated by recent data in rodent models. These studies showed a relevant impact of NFAT-/calcineurin inhibition on the innate immune response by polymorphonuclear neutrophils (PMN) in a candida sepsis model. To clarify whether this is also relevant in humans, we investigated the role of NFAT signaling pathways in PMN activation and effector functions in healthy volunteer donors and patients under immunosuppressive treatment with CsA after HSCT. Methods: Firstly, we performed in vitro experiments using PMN from healthy donors analyzing their effector functions in absence or presence of CsA in titrated doses according to therapeutic levels. In detail, we examined phagocytosis, activation, generation of reactive oxygen species (ROS) and release of inflammatory mediators like IL-8 and TNF-α. After activation with lipopolysaccharide (LPS) and zymosan, phagocytosis and activation-induced shedding of CD62L were measured by flow cytometry using polychromatic microspheres and matching surface markers (CD11b, CD62L, CD66b). In addition, generation of ROS was analyzed by dichlorofluorescein assay (DCF), whereas activation-induced release of inflammatory mediators was measured by enzyme-linked immunosorbent assay (ELISA) and intracellular flow cytometry. In addition, blood samples of patients after HSCT under continuous CsA medication (n=6) and healthy volunteer donors (n=6) were analyzed ex vivo at two different time points after allogeneic HSCT (day 25-35 and 125-135) concerning their PMN effector functions in the same manner as described above. Results: Analysis of healthy donors PMN in vitro showed that CsA had no significant influence on expression of activation markers and shedding of CD62L. Moreover, no substantial influence of CsA on generation of ROS was detected compared to untreated controls (5245 RFU +/- 354 (CsA) vs. 5763 +/- 520 (control) after stimulation with LPS, mean +/- SEM). Furthermore, activation-induced synthesis of IL-8 was not reduced in presence of CsA (519pg/ml +/- 81 vs. 463 +/- 131 (control) after stimulation with LPS). In contrast, CsA rather enhanced phagocytosis after stimulation with LPS (83.5% +/- 1.7 vs. 71.0 +/- 1.5 (control)). Regarding the ex vivo analysis of HSCT patient and healthy donor blood samples, production of ROS was not affected under CsA therapy (35.1% +/- 9.4 vs. 31.1 +/- 6.6 (control) after stimulation with zymosan). Furthermore, CsA medication showed a stimulating effect on PMN phagocytosis which is in line with our in vitro data (58.4% +/- 7.1 vs. 44.3 +/- 2.3 (control) after stimulation with LPS). Interestingly, in several patients an increased production of IL-8 and TNF-α was detectable after stimulation with zymosan (IL-8: 9.1% +/- 3.6 vs. 1.5 +/- 0.3 (control); TNF-α: 16.6% +/- 6.2 vs. 1.0 +/- 0.4 (control)). Conclusions: In contrast to previous results by others in murine model systems, we found an increased phagocytic activity in vitro and ex vivo in human PMN upon NFAT/calcineurin inhibition, whereas other effector mechanisms were unaffected. In addition, HSCT patients under CsA treatment displayed enhanced inflammatory mediators production in PMN. It is currently unclear whether these findings are clinically relevant for the innate immune response after HSCT, e. g. in terms of anti-fungal immunity. Further studies are needed to address whether these enhanced PMN functions in the presence of CsA contribute to a dysregulated innate immune response in humans. Alternatively, our discrepant results may be due to differences in PMN functionality and CsA responsiveness in mice and man. However, while CsA strongly suppresses adaptive immune responses, i.e. T-cell responses in graft-versus-host disease (GvHD), our results so far suggest that CsA does not affect innate immune effector functions by humans PMN in a comparable way. Disclosures Radsak: Celgene: Research Funding.

Beschreibung: Background: Patients with primary refractory acute myeloid leukemia (AML) have a dismal outcome. Only allogeneic stem cell transplantion (SCT) currently offers the chance of cure to these patients. In order to improve outcome after allogeneic SCT, one important prerequisite is to increase response rates prior to SCT. Aims: To evaluate the impact of all-trans retinoic acid (ATRA) and gemtuzumab ozogamicin (GO) given as adjunct to high-dose cytarabine-based salvage therapy in younger adult patients with primary refractory AML on achievement of response. Consecutive allogeneic SCT was intended in all patients. Methods: Main inclusion criteria of the AMLSG 05-04 trial (NCT00143975) were refractory AML following one cycle of ICE (idarubicin, cytarabine, etoposide); and age 18 to 60 years. Dose and schedule of the GO-A-HAM regimen were as follows: GO 3mg/m2, day 1; cytarabine 3g/m2 bid., days 1–3; mitoxantrone 12mg/m2, days 2,3; ATRA 45mg/m2, days 3–5, 15mg/m2 days 6–28. Primary endpoint of the study was CR rate. Safety endpoints comprised early / hypoplastic (ED/HD) death rate, liver toxicity CTC grade 3–5, and rate of veno occlusive disease (VOD) after allogeneic SCT. Results: Between September 2004 and June 2007, 94 patients (median age, 48 yrs; range, 22 to 62) were enrolled. Distribution of cytogenetics was as follows: adverse, n=29 [abn(3q), −5/5q-, −7/7q-, abn(12p), abn(17p), complex]; other n=57 [core binding factor (n=3), cytogenetically normal AML (n=37), various aberrations (n=18)]. FLT3-ITD was present in 18 (22%) of 82 analyzed patients. Response to GO-A-HAM was as follows: CR, n=28 (30%); CRi, n=19 (20%); PR, n=11 (12%); refractory disease (RD), n= 34 (36%); and ED/HD, n=2 (2%). In a logistic regression analysis for achievement of CR, the only significant variable was adverse cytogenetics (OR 0.34, p=0.02). The rate of severe liver toxicity was 0%, the incidence of neutropenic fever was 52%, platelet and neutrophil recovery times from start of treatment were 21 and 22 days, respectively. Following GO-A-HAM, allogeneic SCT was actually performed in 60 patients (64%): matched related (n=14) or unrelated donor (n=42); haploidentical related donor, n=4. All SCT were performed within 3 months after GO-A-HAM, intermediate/severe VOD developed in 5 patients after SCT (9%, 95%-confidence interval (CI) 4–19%), mild VOD in 3 patients. Survival analyses revealed that patients with adverse cytogenetics and/or FLT3-ITD (n=45) had a significantly (p=0.001) inferior overall survival after one year of 38% compared to all other patients (n=39) of 81%. The proportions of patients receiving an allogeneic SCT were similar in both groups (68% and 66%, respectively). Conclusions: The GO-A-HAM regimen is feasible and effective as salvage therapy. However, cytogenetics still remains the most significant variable for achievement of response. Allogeneic SCT after GO-A-HAM was not associated with an increased VOD-rate.

Beschreibung: The clinical value of chemotherapy sensitization of acute myeloid leukemia (AML) with G-CSF priming has remained controversial. Cytarabine is a key constituent of remission induction chemotherapy. The effect of G-CSF priming has not been investigated in relationship with variable dose levels of cytarabine. We randomized 917 AML patients to receive G-CSF (456 patients) or no G-CSF (461 patients) at the days of chemotherapy. In the initial part of the study, 406 patients were also randomized between 2 cytarabine regimens comparing conventional-dose (199 patients) versus escalated-dose (207 patients) cytarabine in cycles 1 and 2. We found that patients after induction chemotherapy plus G-CSF had similar overall survival (43% vs 40%, P = .88), event-free survival (37% vs 31%, P = .29), and relapse rates (34% vs 36%, P = .77) at 5 years as those not receiving G-CSF. However, patients treated with the escalated-dose cytarabine regimen benefited from G-CSF priming, with improved event-free survival (P = .01) and overall survival (P = .003), compared with patients without G-CSF undergoing escalated-dose cytarabine treatment. A significant survival advantage of sensitizing AML for chemotherapy with G-CSF was not apparent in the entire study group, but it was seen in patients treated with escalated-dose cytarabine during remission induction. The HOVON-42 study is registered under The Netherlands Trial Registry (www.trialregister.nl) as #NTR230.

Beschreibung: Transfer of tumor antigen–specific T-cell receptors (TCRs) into human T cells aims at redirecting their cytotoxicity toward tumors. Efficacy and safety may be affected by pairing of natural and introduced TCRα/β chains potentially leading to autoimmunity. We hypothesized that a novel single-chain (sc)TCR framework relying on the coexpression of the TCRα constant α (Cα) domain would prevent undesired pairing while preserving structural and functional similarity to a fully assembled double-chain (dc)TCR/CD3 complex. We confirmed this hypothesis for a murine p53-specific scTCR. Substantial effector function was observed only in the presence of a murine Cα domain preceded by a TCRα signal peptide for shuttling to the cell membrane. The generalization to a human gp100-specific TCR required the murinization of both C domains. Structural and functional T-cell avidities of an accessory disulfide-linked scTCR gp100/Cα were higher than those of a dcTCR. Antigen-dependent phosphorylation of the proximal effector ζ-chain–associated protein kinase 70 at tyrosine 319 was not impaired, reflecting its molecular integrity in signaling. In melanoma-engrafted nonobese diabetic/severe combined immunodeficient mice, adoptive transfer of scTCR gp100/Cα transduced T cells conferred superior delay in tumor growth among primary and long-term secondary tumor challenges. We conclude that the novel scTCR constitutes a reliable means to immunotherapeutically target hematologic malignancies.

Beschreibung: Adoptive cellular immunotherapy inducing a graft-versus-tumor (GVT) effect is the therapeutic mainstay of allogeneic hematopoietic stem cell transplantation (ASCT) for high-risk leukemias. Autologous immunotherapies using vaccines or adoptive transfer of ex vivo–manipulated lymphocytes are clinically explored in patients with various cancer entities. Main reason for failure of ASCT and cancer immunotherapy is progression of the underlying malignancy, which is more prevalent in patients with advanced disease. Elucidating the molecular mechanisms contributing to immune escape will help to develop strategies for the improvement of immunologic cancer treatment. To this end, we have undertaken functional screening and expression cloning of factors mediating resistance to antigen-specific cytotoxic T lymphocytes (CTLs). We have identified Cdc42, a GTPase regulating actin dynamics and growth factor signaling that is highly expressed in invasive cancers, as determinator of cancer cell susceptibility to antigen-specific CTLs in vitro and adoptively transferred immune effectors in vivo. Cdc42 prevents CTL-induced apoptosis via mitogen-activated protein kinase (MAPK) signaling and posttranscriptional stabilization of Bcl-2. Pharmacologic inhibition of MAPK/extracellular signal–regulated kinase (ERK) kinase (MEK) overcomes Cdc42-mediated immunoresistance and activation of Bcl-2 in vivo. In conclusion, Cdc42 signaling contributes to immune escape of cancer. Targeting Cdc42 may improve the efficacy of cancer immunotherapies.

Beschreibung: Background SIRT1 is a NAD+ dependent histone deacetylase, which has been shown to act as an important regulator of apoptosis, DNA-repair and is involved in the maintenance of genetic integrity under conditions of cellular stress. Beside deacetylation of histones H4K16, SIRT1 has numeral other substrates including KU70, FOXO1 or p53. SIRT1 deacetylates p53 at lysine 382 thereby reducing its transcriptional activity followed by loss of p53 dependent apoptosis in response to cell damage. The activity of SIRT1 is negatively regulated by DBC1 (Deleted in Breast Cancer 1) and involves protein–protein interaction (Kim et al., Nature 2008). Recent reports have demonstrated increased expression of SIRT1 in leukemic cells. Of note, SIRT1 seems to be specifically essential to maintain stem cell activity in CML leukemic stem cells (Li et al, Cancer Cell, 2012), however the role of SIRT1 in acute myeloid leukemia (AML) and in the context of other oncogenic tyrosine kinases is poorly understood. Aims To characterize the role of SIRT1 in acute myeloid leukemia in the context of defined genetic backgrounds. Methods To investigate the functional role of SIRT1 we performed expression analysis studies. Inhibition of SIRT1 was achieved by shRNA experiments and pharmacological targeting. Functional consequences were addressed by immunoblotting, co-immunoprecipitation, cell death assays, gamma-H2AX staining and xenotransplantion experiments. Results SIRT1 protein expression analysis in primary human AML samples (n=20) and cell lines (n=13) showed preferential high expression levels in cells harboring FLT3-ITD mutations or oncogenic KRAS/NRAS. Inhibition of FLT3 signaling using shRNA-mediated knockdown of FLT3 or upon treatment with tyrosine kinase inhibitors caused a time and dose dependent suppression of SIRT1 expression accompanied by an increase in p53 acetylation. Vice versa, overexpression of FLT3-ITD in BaF/3 cells or in several murine leukemia models (e.g. MLL/AF9 +/-FLT3-ITD; AML1/ETO +/-FLT3-ITD) induced significant upregulation of SIRT1. Targeting SIRT1 using the SIRT1/2 inhibitor Tenovin-6 (TV-6) or knockdown of SIRT1 resulted in a slight increase in apoptotic cell death in primary AML samples and cell lines. In contrast, inhibition of SIRT1 significantly sensitized to FLT3 inhibitor therapy. Of note, the combination of TV-6 and midostaurin inhibited colony growth and replating activity in MLL-AF9 or AML1-ETO cells harboring FLT3-ITD mutations. Further, knockdown of SIRT1 in the AML cell line MV4-11 expressing a doxycycline-regulated SIRT-shRNA resulted in prolonged survival in a xenotransplantation model. The observed effects prompted us to investigate whether mutated FLT3 is directly involved in the regulation of SIRT1. Inhibition of FLT3-ITD kinase activity caused an increased phosphorylation of the physiological SIRT1-inhibitor DBC1 followed by binding of SIRT1 as revealed by co-immunoprecipitation experiments. We also noticed a slight increase in ATM/ATR phosphorylation and an increase in ATM-DBC1 binding upon FLT3-ITD inhibition indicating SIRT1 inhibition via the ATM-DBC1-SIRT1 axis. These effects were substantially enhanced upon treatment with genotoxic agents (cytarabine; irradiation) in combination with midostaurin compared to either agent alone and were accompanied by increased p53 acetylation and an increased number of gamma-H2AX foci. Conclusion SIRT1 is overexpressed in AML cells and partially regulated by FLT3-ITD or oncogenic RAS. In FLT3-ITD mutated cells SIRT1 is constitutively activated, likely via the inhibition of the physiological inhibitor DBC1. Pharmacologic targeting of SIRT1 sensitizes AML cells to TKI therapy or genotoxic agents and partially restored the FLT3-ITD associated defective stress response pathway ATM-DBC1-SIRT1 resulting in activation of p53. Disclosures: Kindler: Novartis: Membership on an entity’s Board of Directors or advisory committees.

Beschreibung: Introduction Starvation of tumor cells from the amino acid arginine has recently gained particular interest because of the downregulation of the rate-limiting enzyme argininosuccinate synthethase 1 (ASS1) in various cancer entities. ASS1-deficient cells cannot resynthesize arginine from citrulline and are therefore considered arginine auxotrophic. The arginine depleting enzyme arginine deiminase (ADI-PEG20, Polaris Pharmaceuticals) is currently tested in phase I-III clinical trials for different arginine auxotrophic cancers. The natural arginine analogue canavanine can compete with arginine for arginyl-tRNA-binding sites and consequently be incorporated into nascent proteins instead of arginine. Canavanine could therefore potentially further disturb intracellular protein homeostasis, especially under arginine deprivation. The sensitivity of myeloma cells towards arginine depletion strategies has not been analyzed so far. Methods Human myeloma cell lines and CD138-sorted primary human myeloma cells from patient bone marrow were screened for ASS1 expression by western blotting (WB). The cells were cultured in arginine free medium and assessed for proliferation and metabolic activity (CFSE/MTT assays), apoptosis (caspase-3 cleavage) and cell death (annexinV/propidium iodide). Canavanine was supplied in both arginine-sufficient and -deficient conditions. The level of intracellular protein stress was determined by WB and/or flow cytometry analysis for ubiquitinated proteins, phosphorylated eukaryotic initiation factor 2α (peIF2α) and the spliced isoform of the X-Box binding protein 1 (Xbp1s). Repetitive ADI-PEG20 ± canavanine application i.p. were tested in vivo in an U266 myeloma xenograft model in NOD/SCID/IL2Rcg-/- (NSG) mice. Arginine and canavanine levels in plasma were determined by HPLC. Tumor growth was measured, mice were assessed for survival, weight and side effects. Tumor tissues were analyzed for caspase-3 cleavage and Ki67 expression by immunohistochemistry. Results 5 of 6 myeloma cell lines were negative for ASS1. Also, ASS1 was either not or only weakly expressed in the majority of primary CD138+ myeloma patient samples. Arginine starvation induced an arrest of cell proliferation and/or metabolic activity of primary myeloma cells and myeloma cell lines after 18-24 h. Addition of citrulline could only rescue ASS1 positive myeloma cells due to the intracellular resynthesis of arginine. Arginine starvation alone led to delayed induction of apoptosis (e.g. 35% cell death of NCI-H929 cells after 72 h of treatment). Addition of 100 mM canavanine strongly increased cell death specifically in the context of arginine deficiency (e.g. cell death in NCI-H929 cells: 87% after 24 h, 100 % after 48h) while it was non-toxic and had no effect on cell viability under physiological arginine conditions. Co-application of canavanine induced ubiquitination of cellular proteins and led to the prolongation of a fatal unfolded protein response (UPR) as measured by markedly elevated Xbp1s levels. Prolonged UPR ultimately led to the induction of apoptosis as reflected by annexin V binding and caspase-3 cleavage. In an U266 myeloma NSG xenograft model, systemic arginine depletion by ADI-PEG20 suppressed tumor growth in vivo and significantly prolonged median survival of mice when compared with the control group (22±3 vs. 15±3 days). Canavanine treatment alone had no influence on viability (13±0 days). However, the combination of ADI-PEG20 and canavanine demonstrated the longest median survival (27±7 days). Histological examination of explanted tumors showed the highest rates of caspase-3 cleavage in the ADI-PEG20/canavanine group. Conclusion Myeloma cells are mostly arginine auxotrophic and can be selectively targeted by arginine starvation. Combination of arginine depletion with the arginine analogue canavanine leads to a highly efficient and specific tumor cell eradication and should be further optimized in multiple myeloma preclinical models. Disclosures Bomalaski: Polaris Pharmaceuticals Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees.