ALBERT

Description: Background: Current treatment options for R/R AML are highly inadequate. CD33 is expressed in 〉99% of AML cases. BiTE®s have been effective in R/R Acute Lymphoblastic Leukemia. AMG 330 is a BiTE® that binds CD33 and CD3 on T cells, facilitating T-cell destruction of CD33+ cells. The objectives of this ongoing study are to evaluate the safety, pharmacokinetics, and pharmacodynamics of AMG 330 in R/R AML and to estimate the maximum tolerated dose. Methods: This was a phase 1 dose escalation study evaluating AMG 330 as a continuous IV infusion in patients with R/R AML, with single-patient cohorts for the first 3 doses and subsequently 3-6 patients per cohort (NCT#02520427). Response was per revised IWG criteria with the addition of complete response (CR) with partial hematologic recovery. After completing the first cycle without dose-limiting toxicity (DLT), up to 5 additional cycles could be given for benefit. After the 30 μg/day (d) cohort, risk mitigation measures for cytokine release syndrome (CRS) were put in place, including step-dosing and pretreatment with a single dose of corticosteroids. The modified treatment regimen consisted of an initial run-in dose of 10 μg/d × 4d followed by the target dose. A 2-step regimen was then tested, ie 10 μg/d, 60 μg/d, and then the target dose, for a treatment duration of 14d or 28d, followed by 1-4 weeks off treatment. Results: As of June 14, 2018, 35 patients had enrolled in 12 dose cohorts with a target dose range of 0.5-480 μg/d in this ongoing study. Over half (20/35, 57%) of patients were male and the median age was 58 (range: 18-80) years; 14/35 (40%) have previously received a stem cell transplant. Median AML disease duration at baseline was 1.3 (range: 0.3-9.6) years, median proportion of blasts at baseline was 37% (range: 3%-95%), and the median # of prior treatments was 4 (range: 1-15). Median baseline ANC was 0.2 (range: 0-8.6) × 109/L. Patients received a median of 1 (range: 1-6) cycle with AMG 330; 31/35 (89%) patients discontinued treatment for disease progression (n=24), adverse events (AEs; n=5, 2 treatment-related), and patient request (n=2). One patient completed the maximum of 6 cycles allowed and 3 patients are still receiving study drug. Serious AEs (SAEs) were seen in 23/35 (66%) patients (treatment-related in 15 patients); SAEs seen in 〉1 patient included CRS (n=11), febrile neutropenia (n=6), pneumonia (n=4), leukopenia (n=3), thrombocytopenia (n=2), and subdural hematoma (n=2); 1 patient died on study due to AML progression (not treatment-related). One patient each in the 10 μg/d and 30 μg/d cohorts (no lead-in) experienced severe CRS; CRS signs and symptoms resolved in 1d with corticosteroids, vasopressors, and IV fluids, and interruption of AMG 330. There were DLTs of grade 2 CRS and grade 4 ventricular fibrillation with a target dose of 480 μg/d; the target dose was then decreased to 240 μg/d. Two patients had a CR at a target dose of 240 μg/d (lead-in of 10 μg/d→60 μg/d); 1 patient each at target doses of 120 μg/d and 240 μg/d had a CRi and 1 patient who received 1.5 μg/d had a morphologic leukemia-free state (MLFS,

Description: Peripheral (mature) T-cell lymphomas (PTCL) are represented by distinct lymphoma entities, many of which with a rather unfavourable clinical outcome as compared to B-cell lymphomas. Standard treatment regimens have not been established, except in primary cutaneous T-cell lymphomas (PCTCL). With regard to the unfavourable prognosis we designed a treatment protocol using chemoimmunotherapy in peripheral T-cell lymphomas except PCTCL and ALK-positive large cell anaplastic T-cell lymphomas, consisting of alemtuzumab 3, 10, 30, 30 mg, days 1–4, fludarabine (Flu) 25 mg/m2 days 2–4, cyclophosphamide (CP) 600 mg/m2 day 3, and doxorubicin (Dox) 50 mg/m2 day 4. Included were patients with primary diagnosis or with first or second relapse. Rationales for this regimen were proven efficacy of CP and Dox in T-cell lymphomas, high efficacy of Flu and CP (FC) in other lymphomas and the possible synergism of antibodies with cytotoxic drugs. So far, 23 patients have been included, 18 are evaluable for response and toxicity. Of the latter, 10 patients were diagnosed with PTCL-NOS, 5 with AILD, one with enteropathy-associated T-cell lymphoma, one with NK-cell lymphoma, and one with T-PLL. 9 patients were enrolled with primary diagnosis and 9 patients in relapse. The median age was 60 years (range 21–77); the median non-age adjusted IPI 2.5 (0–4), 2 in patients with primary diagnosis and 3 in patients with relapse. The overall response rate was 61% (11/18). In patients with primary diagnosis the CR rate was 78% (7/9), one patient achieved no change, and one patient died from treatment associated complications before response could be evaluated. All responding patients are in ongoing CR at 2+, 2+, 6+, 11+, 15+,16+, and 17+ months. In the group of relapsed patients one CR and 3 PR (44%) were observed. The main toxicity was leukocytopenia (81% grade III and IV of all evaluable treatment cycles), other grade III and IV toxicities included anemia (18%), thrombocytopenia (39%), infections (18%) nausea/emesis (9%), and allergic reactions (4%). Ten (56%) patients reactivated CMV without CMV-related disease and one patient with suspected CMV-peumonia. In conclusion, this is the first study demonstrating that alemtuzumab can be integrated into a triple-agent chemotherapy regimen. The combination is effective in the first-line treatment of peripheral T-cell lymphomas, however, regarding the general outcome a longer follow-up period of a larger patient population is required.

Description: The CD33-targeting bispecific T-cell engager (BiTE) AMG 330 proved to be highly efficient in mediating cytolysis of acute myeloid leukemia (AML) cells in vitro and in mouse models. Yet, T-cell activation is correlated with upregulation of programmed cell death-ligand 1 (PD-L1) and other inhibitory checkpoints on AML cells that confer adaptive immune resistance. PD-1 and PD-L1 blocking agents may counteract T-cell dysfunction, however, at the expense of broadly distributed immune-related adverse events (irAEs). We developed a bifunctional checkpoint inhibitory T cell–engaging (CiTE) antibody that combines T-cell redirection to CD33 on AML cells with locally restricted immune checkpoint blockade. This is accomplished by fusing the extracellular domain of PD-1 (PD-1ex), which naturally holds a low affinity to PD-L1, to an αCD3.αCD33 BiTE-like scaffold. By a synergistic effect of checkpoint blockade and avidity-dependent binding, the PD-1ex attachment increases T-cell activation (3.3-fold elevation of interferon-γ) and leads to efficient and highly selective cytotoxicity against CD33+PD-L1+ cell lines (50% effective concentration = 2.3-26.9 pM) as well as patient-derived AML cells (n = 8). In a murine xenograft model, the CiTE induces complete AML eradication without initial signs of irAEs as measured by body weight loss. We conclude that our molecule preferentially targets AML cells, whereas high-affinity blockers, such as clinically approved anticancer agents, also address PD-L1+ non-AML cells. By combining the high efficacy of T-cell engagers with immune checkpoint blockade in a single molecule, we expect to minimize irAEs associated with the systemic application of immune checkpoint inhibitors and suggest high therapeutic potential, particularly for patients with relapsed/ refractory AML.

Description: Key Points CD33 expression levels in AML correlate with specific disease characteristics. Potent cytotoxicity against primary AML blasts is mediated by a CD33/CD3-bispecific antibody.

Description: Adoptive transfer of polyclonal EBV-specific T cell lines has been used as prophylaxis and therapy in patients with EBV-associated malignancies. However, this strategy is time-consuming and demands difficult generation of lymphoblastoid cell lines (LCLs) and corresponding T cells for each individual patient. We applied an alternative strategy to confer T cell immunity against EBV-antigens by isolating EBV antigen-specific T cell receptors (TCRs) for transduction of primary human T cells for adoptive therapy. Previously, we have demonstrated the feasibility of using peptide-pulsed dendritic cells (DC) for generating high-affinity EBV antigen-specific T cell lines and T cell clones. Based on this strategy, T cell clones directed against LMP2a and EBNA3a were generated and functionally analyzed. Monospecificity was demonstrated by homogeneous double staining with CD8 and appropriate tetramers. High avidity of T cell clones (〈 0.01 μM) was shown by peptide titration in an ELISPOT assay for IFN-γ secretion. In addition, the cytokine secretion profiles of some of the T cell clones were tested by cytokine bead array assay. High secretion levels of IFN-γ, IL-2 as well as TNF-α after stimulation with the EBNA3a- or LMP2a-peptide were shown for the corresponding T cell clones. Potent TCRs from one LMP2a-specific, HLA-A2-restricted and one EBNA3a-specific, HLA-B8-restricted T cell clone were isolated and cloned into the retroviral vector MP71. Transduction efficiency of TCR-deficient T cell lines was 〉 40% (TCR-LMP2a) and 〉 30% (TCR-EBNA3a) as measured by tetramer staining. Both TCR-LMP2a- and TCR-EBNA3a-redirected T cell lines were functional as indicated by NFAT-mediated luciferase expression upon TCR-MHC-peptide ligation. Primary human T cells were successfully transduced with TCR-LMP2a (∼ 12% tetramer-positive) and TCR-EBNA3a (∼ 3% tetramer-positive). Importantly, both TCRs conferred similar cytolytic activity against EBV-transformed B cell lines. Our data support the development of TCR-transduced T cells for adoptive transfer in EBV-associated malignancies, including Hodgkin′ s disease and nasopharyngeal carcinoma in which only subdominant EBV antigens are expressed. The feasibility and the therapeutic potential of TCR-transduced T cells for adoptive transfer have already been shown in a clinical phase I trial in patients with metastatic melanoma. We believe that redirecting human PBLs is a rapid and efficient tool toward adoptive transfer in EBV-associated malignancies.

Description: Background: In acute myeloid leukemia (AML), detection of minimal residual disease (MRD) by flow cytometry is an adverse prognostic factor besides pre-treatment risk classifications, including cytogenetic and molecular aberrations. High dimensional multiparameter flow cytometry (MPFC) offers improved sensitivity and specificity, however manual analysis is increasingly challenging. In this study, we explore the value of the recently proposed viSNE algorithm to quantify MRD levels in patients with AML achieving complete remission (CR) after intensive induction chemotherapy. Methods: Bone marrow samples from patients with AML (excluding patients with acute promyelocytic leukemia) were analyzed by 8-10 MPFC using a NAVIOS flow cytometer (Beckman Coulter, Brea, CA, USA). Only patients achieving a CR or CR with incomplete blood count recovery (CRi) post-induction were included in this analysis. Manual gating of MRD flow data was performed as described previously (Köhnke et al., Leukemia 2014) using a cutoff for MRD positivity of 0.1%. The viSNE algorithm was performed as described previously (Amir et al., Nat. Biotech. 2013) and MRD positivity was defined as the presence of a distinct cluster of 〉100 cells which consisted of 〉90% patient cells. Kaplan-Meier estimator and log-rank test as well as Cox's proportional hazards regression model were used to analyze survival data. Results: Post-induction flow cytometry and clinical data of 38 patients with AML achieving CR (n=34) or CRi (n=4) were available for analysis (median age 53 years; de-novo AML n=32, tAML n=1, sAML n=5). Most patients belonged to the intermediate cytogenetic risk group (MRC favorable n=5, intermediate n=22, adverse n=11). 19/38 patients were MRD positive post-induction by manual gating. 12/19 patients deemed MRD positive relapsed, whereas 3/19 patients deemed MRD negative relapsed. Therefore, MRD positivity by manual gating correlated with reduced relapse free survival (median RFS for MRD positive patients: 7.5 months vs. median not reached for MRD negative patients, log-rank test p=0.017). For overall survival (OS), no significant impact of MRD positivity could be detected so far (p=0.3), however follow-up was short (median follow-up 9.3 months). MRD positivity by manual gating remained an independent risk factor for RFS (HR 4.8, p=0.021) when compared to genetic risk and age. MRD positivity by viSNE clustering was seen in 19/38 patients. 10/19 patients deemed MRD positive by viSNE relapsed, while 5/19 deemed MRD negative by viSNE experienced a relapse. This resulted in a trend towards shorter RFS for MRD positivity by viSNE (median RFS 9.9 months vs. 19.0 months for MRD negative patients, p=0.185). Among the patients deemed MRD positive by viSNE who did not relapse, i.e. false-positive patients, follow-up was very short (

Description: Acute myeloid leukemia (AML) is a highly heterogeneous disease. Numerous cytogenetic and molecular markers distinguish different biological and prognostic groups. Immunological effects play an important role for the treatment of AML, especially for the eradication of minimal residual disease, as proven by the success of allogeneic stem cell transplantation and some autologous immunotherapeutic strategies. However, various immunosuppressive factors dampen these potential effects. For several malignancies, the relevance of coinhibitory receptor ligand interactions that influence the interaction of tumor cells with specific immune effector cells such as T and NK cells has recently been proven by clinical studies with respective blocking antibodies. In order to investigate the potential significance of this mechanism in AML, we measured the surface expression of a broad panel of immune checkpoint proteins (CD80, CD86, CD273, CD274, CD275, CD276, B7-H4, HVEM, OX40L) on 209 AML samples at initial diagnosis by flow cytometry. The specific fluorescence intensity of these markers on the CD33 positive blast cell population was correlated with morphologic, cytogenetic and molecular characteristics of the disease. Subsequently, we analyzed the potential prognostic significance of immune checkpoint protein expression on overall and relapse-free survival after achievement of complete remission (median observation time: 225 days). All patients were included in the AML registry of the AML Cooperative Group and treated according to their treatment recommendations. A few of these molecules (CD80, CD273, CD275, B7-H4) were not detectable in the majority of cases and thus do not seem to play a role in the interaction of AML blast cells with immune effector cells, but others showed a significant and patient-specific expression. We found that AMLs of monocytic lineage (M4 or M5 according to FAB) expressed higher levels of CD86 (p 〈 0.001) and CD276 (p 〈 0.001), compared to the other morphologic subgroups. The FLT3-ITD correlated with lower expression of CD274 (p=0.001) and CD276 (p = 0.007), while the prognostically favorable subgroup with an isolated NPM1 mutation (without accompanying FLT3-ITD) and normal karyotype correlated with higher expression of CD86 (p = 0.049) and CD276 (p = 0.033) and lower expression of OX-40L (p = 0.039). The patients with very high expression of both CD86 and CD274 had a worse overall (p = 0.006) and relapse-free (p = 0.040) survival. Of particular interest was the analysis of HVEM, a member of the TNF-receptor superfamily, which has rarely been described in the context of AML so far. Its expression was reduced both in the groups with FLT3-ITD (p = 0.001) and with NPM1mut/FLT3wt/CN (p = 0.049), but highly increased in leukemias with normal karyotype and biallelic CEBPA mutation (p = 0.008). Of note, a high expression of HVEM correlated with significantly higher relapse-free survival within the prognostically intermediate group according to ELN (p = 0.005). We thus for the first time provide evidence that the profile of immune checkpoint molecules on CD33 positive leukemic cells correlates with molecular disease characteristics in AML and may even possess prognostic information, especially for relapse. Based on these data, we are currently evaluating different immune checkpoint molecules for their potential as therapeutic targets with respect to boosting antileukemic immune responses. Disclosures: No relevant conflicts of interest to declare.

Description: Background: The PTLD-1 trial has demonstrated the efficacy and safety of 4 cycles of weekly rituximab followed by 4 cycles of CHOP-21 + G-CSF in CD20-positive PTLD after solid organ transplantation. Median overall survival (OS) was 6.6 years, a clear improvement over the preceding rituximab monotherapy trials (2.4 years). However, response to rituximab induction predicted OS after completion of therapy. Based on the hypothesis that rituximab consolidation might be sufficient treatment for patients already in a complete response (CR) after rituximab induction, trial treatment was changed in 2007 through a protocol amendment introducing risk-stratified sequential treatment (RSST): rituximab consolidation for patients in CR after rituximab induction and R-CHOP-21 consolidation for all others. Methods: In this international, multicenter phase II trial (PTLD-1, 3rd amendment; NCT00590447), treatment-naïve adult solid organ transplant recipients diagnosed with CD20-positive PTLD were treated with rituximab (375 mg/m2 IV) on days 1, 8, 15 and 22. After restaging, patients in CR continued with four three-weekly courses of rituximab monotherapy while all others received 4 cycles of R-CHOP-21 + G-CSF. In case of disease progression during rituximab monotherapy R-CHOP was commenced immediately. The primary endpoint was treatment efficacy measured as response rates and response duration. Analysis was by intention to treat. This is the final analysis of 152 patients treated with RSST from 2007 to 2014 at centers in Germany (72), Belgium (36), France (24), Australia (7), Poland (7) and Italy (6) with a median follow-up of 4.5 years. The 70 patients treated with rituximab followed by CHOP-21 in the original PTLD-1 trial (median follow-up 5.1 years) served as a control population. Inclusion criteria and follow-up schedule were identical; there were no significant differences in the transplant- and lymphoma-related baseline factors listed below. Results: 115/152 patients were male. 69/152 were kidney, 40 liver, 18 lung, 15 heart, 5 heart/kidney, 3 kidney/pancreas and 2 heart/lung transplant recipients. Median age at diagnosis was 56 years. PTLD was late (〉 1 year after transplantation) in 120/152 (79%) of patients. 67/145 (46%) PTLD were EBV-associated. 130/152 patients had monomorphic, 20 polymorphic and 2 early lesion PTLD. The overall response rate (ORR) was 111/126 (88%, CR: 88/126 [70%]). Median duration of remission (DR) was not reached; the 3-year Kaplan-Meier estimate was 82% (compared to 71% in PTLD-1). In the intention-to-treat population (152 patients), the median time to progression (TTP) was not reached either. The 3-year Kaplan-Meier estimate was 78% (69% in PTLD-1). Median OS by intention-to-treat was 6.6 years (95% CI 5.5 - 7.6) with a 3-year estimate of 70% in comparison to 61% in PTLD-1. There was no significant difference in ORR, DR, TTP or OS between EBV-positive and EBV-negative PTLD. On the other hand, response to 4 applications of rituximab was a highly significant predictor of OS, TTP and progression-free survival (PFS) despite treatment stratification (all p

Description: Antibody-based immunotherapy represents a promising strategy to target and eliminate acute myeloid leukemia (AML) tumor cells. We evaluated BST1/CD157, a novel, slow internalizing surface antigen, for its suitability as immunotherapeutic target in AML. An Fc-optimized antibody against BST1/CD157 was developed (MEN1112/OBT357NF), which binds to the Fc-receptor on natural killer (NK) cells with enhanced affinity. The target antigen expression profile of BST1/CD157 on AML bulk cells as well as on leukemic stem cells (LSC) was analyzed with flow cytometry using a commercially available antibody. BST1/CD157 expression was detected in 〉 97% of AML patients at primary diagnosis (n=81) and at time of relapse (n=20) using specific fluorescence intensity (SFI, positivity: SFI 〉 1. 5). Importantly, BST1/CD157 was also expressed on CD34+/CD38-cells (n=20), the compartment with a high percentage of LSCs. Functional titration experiments of MEN1112/OBT357NF showed antibody-mediated lysis of U937 cells in the low picomolar range (EC50 = 30–140 pM) and demonstrated superior ADCC activity compared to its non Fc-engineered parental analogue. To evaluate the additive effect of the complement cascade, healthy donor (HD) monocytes were co-incubated with autologous NK cells and MEN1112/OBT357NF in the presence or absence of 5% donor serum. After 20 hours of incubation, a significantly enhanced lysis efficacy by MEN1112/OBT357NF through the addition of serum compared to control cultures without serum (p=0.02) was demonstrated. For further functional characterization of MEN1112/OBT357NF standard chromium release assays using AML cell lines and NK cells from HDs were performed. In this setting, efficient target cell lysis (30–50%) at various effector cell:target (E:T) ratios (50:1–6:1) was observed. Compared to Rituximab-mediated lysis of RAJI cells, MEN1112/OBT357NF triggered more efficient target cell lysis at much lower effector cell concentrations (33% lysis of OCI-AML3 cells vs. 11% lysis of RAJI cells at E:T 6:1). Furthermore, the cytotoxic potential of NK cells from AML patients after intense double induction chemotherapy on AML cell lines was tested. The results were highly variable with efficient lysis in about one third of samples tested (n=10). As a positive control NK cells from HDs were used which showed superior lysis as compared to patient-derived NK cells. In an autologous set-up using NK cells from either primary diagnosis or at time of remission, we could show efficient lysis of primary AML cells in one of two patient samples (patient in complete remission) in the presence of MEN1112/OBT357NF. In summary, our analysis demonstrates that BST1/CD157 is a promising target antigen for antibody-based therapy in AML. The effective in-vitro ADCC activity supports further development of MEN1112/OBT35NF as an immunotherapy for patients with AML. Disclosures Krupka: Oxford BioTherapeutics Ltd: Research Funding. Jansen:Oxford BioTherapeutics Ltd: Research Funding. Aud:Oxford BioTherapeutics Ltd: Employment. Dusek:Oxford BioTherapeutics Ltd: Employment. Bisht:Oxford BioTherapeutics Ltd: Employment. Pombo-Villar:Oxford BioTherapeutics Ltd: Employment, Equity Ownership. Rohlff:Oxford BioTherapeutics Ltd: Employment. Subklewe:Oxford BioTherapeutics Ltd: Research Funding.

Description: The fms-related tyrosine kinase 3 (FLT3) receptor has been extensively studied over the past two decades with regards to oncogenic alterations that do not only serve as prognostic markers but also as targets for therapy in acute myeloid leukemia (AML). Internal tandem duplications (ITDs) became of special interest in this setting as they are associated with unfavorable prognosis. Due to sequence-dependent protein conformation changes, FLT3-ITD tends to auto-phosphorylate and displays a constitutive intracellular localization. As tyrosine kinase inhibitors (TKIs) efficiently block FLT3 auto-phosphorylation, we set out to study the effect of TKI on the subcellular localization of the FLT3 receptor and its mutants. We visualized FLT3 WT and its mutants (N676K, D835Y, W51 (ITD), NPOS (ITD), K644R, W51-K644R) in transiently transfected U2OS cells, using anti-FLT3 immunofluorescence in combination with confocal microscopy. Treatment with 50nM of the TKI AC220 for 6 hours restored the membrane localization of both ITD (Figure 1 A) and D835Y. The TKI-induced surface expression of FLT3-ITD was confirmed by flow cytometry (mean fluorescence intensity, MFI) of BaF3 cells stably expressing FLT3 WT or mutants and in the homozygous (ITD/ITD) AML cell line (MV4-11). Similar results were obtained in cells from an AML patient derived xenograft (pdx) with FLT3-ITD and loss of heterozygosity (LOH) (Figure 1 B). Western blot analysis showed increased glycosylation of FLT3-ITD after TKI-treatment (Figure 1 C) suggesting that auto-phosphorylation prevents physiological processing of the receptor, which is required for maturation and surface expression. To monitor the subcellular localization of FLT3 and its mutants in vivo we have generated a FLT3-GFP fusion. Proliferation assays in BaF3 cells confirmed that the C-terminal GFP-tag does not alter the function of FLT3. Upon FLT3-ligand (FL) stimulation of FLT3-GFP we observed FLT3-internalization by life cell imaging in U2OS cells. Conversely, TKI treatment increased cell surface expression of FLT3-GFP. Our findings have translational implications when considering FLT3 as a target for immunotherapy in AML, since FLT3 surface expression might facilitate antigen recognition. Especially FLT3-ITD positive patients with LOH may benefit from a combined TKI-immunotherapy approach. Therefore, we currently study the effect of AC220 on FLT3 antibody-dependent cellular cytotoxicity (ADCC), mediated by natural killer (NK) cells. Taken together, we discovered that TKI alters the subcellular localization and protein processing of specific FLT3 mutants. However, the complex interplay between the individual posttranslational modifications and their role in FLT3 traffic remains elusive. Disclosures Krupka: AMGEN Research (Munich): Research Funding. Subklewe:AMGEN Research (Munich): Research Funding.