ALBERT

Description: Despite recent advancements, approximately 50% of patients with acute myeloid leukemia (AML) do not respond to induction therapy (primary induction failure, PIF) or relapse after

Description: The optimal source of donor hematopoietic stem cells (HSC) is controversial. Granulocyte colony stimulating factor (G-CSF) mobilized peripheral blood (G-PB) has replaced bone marrow (BM) as the most common allograft source in adults but is associated with donor morbidity and higher rates of chronic graft versus host disease (GVHD) compared to BM. The CXCR4 antagonist plerixafor (Px) mobilizes HSC into the PB (Px-PB) faster than G-CSF and preliminary data suggest both quantitative and qualitative differences in allograft content that may impact clinical outcomes. We sought to assess the efficacy and safety of transplanted allografts collected following mobilization with Px alone in HLA-identical sibling transplantation. This was a Phase II, two-strata, multi-center prospective trial (NCT01696461) to evaluate Px-PB allografts prior to reduced intensity conditioning (RIC) and myeloablative conditioning (MAC) based hematopoietic cell transplantation (HCT). Patients aged 18-65 years with an HLA-ID sibling donor and a hematological malignancy suitable for HCT were eligible. The primary objective was to determine the proportion of donors whose cells could be successfully mobilized and collected with a sufficient CD34+ cell dose using Px as the sole mobilizing agent. Px mobilization was considered successful if ≥ 2.0x10^6 CD34+ cells/kg recipient weight were collected in no more than two leukapheresis (LP) collections. All donors receiving Px were included in the analysis of the primary objective based on the intention-to-treat principle. Secondary objectives included the incidence of acute and chronic adverse events in donors, rates of hematopoietic engraftment, donor chimerism, rates of acute and chronic GVHD, non-relapse mortality (NRM), progression free survival (PFS) and overall survival (OS) for the recipients. From July 2013 to December 2014, 64 donor/recipient pairs were enrolled at 12 centers. Donors received Px at 240μg/kg subcutaneously 4 hours prior to LP. LP was performed processing at least 4X blood volume for up to two consecutive days (a third day was allowed for low CD34+ cell yields after 2 LP procedures) to achieve a target CD34+ cell dose of ≥ 4.0 x 10^6/kg recipient weight with a minimum goal of ≥ 2.0 x 10^6/kg. All allografts were cryopreserved. GVHD prophylaxis included cyclosporine or tacrolimus in combination with methotrexate, mycophenolate mofetil, or sirolimus. G-CSF was given routinely post HCT only to MAC recipients. Patient demographics are provided in Table 1. The median donor age was 56 years (18-65). 64% of the donors were male. Donors underwent one (23%), two (72%), or three (5%) LP procedures. 63 of 64 (98%) donors achieved the primary objective. The median total CD34+ cell dose/kg recipient weight collected within 2 days was 4.6 (0.9-9.6). Maximal donor toxicity following Px injection and LP was grades 0 (30%), 1 (52%), 2 (17%), and 3 (2%). Bloating, flatulence, abdominal pain, headache, paresthesisas, injection site reaction, and dizziness were the most commonly observed toxicities. Bone pain was not observed. The one grade 3 toxicity was a vasovagal episode felt related to LP and unlikely to Px. Toxicities typically resolved within a week of LP. The median follow up is 6.3 months. Median days to ANC (〉0.5 x10^9/L) and Platelet count (〉20 x 10^9/L) recovery were 13.5 (10-148) and 19 (1-76) after MAC and 14.5 (0-25) and 18 (0-141) after RIC, respectively. The cumulative incidence of acute GVHD grades 2-4 and 3-4 at day 100 were 47% (95% CI: 30-64) and 9% (95% CI: 2-22) after MAC and 19% (95% CI: 6-38) and 5% (95% CI: 0-18) after RIC. Probability of NRM at day 100 was 4% (95% CI: 0-13) and 0% after MAC and RIC, respectively. The probability of OS at day 100 was 97% (95% CI: 88-100) and 90% (95% CI: 78-98) after MAC and RIC, respectively. In conclusion, this is the first multi-center trial to demonstrate that as an alternative to G-CSF, Plerixafor rapidly, safely, and effectively mobilizes sufficient numbers of CD34+ cells from HLA-ID sibling donors for HCT following both RIC and MAC regimens. Engraftment was generally prompt and early results of secondary endpoints in recipients are encouraging. Longer follow-up and more extensive analysis of donor allografts and recipient outcomes will be presented at the time of the meeting. Research support was provided in part by Genzyme, a Sanofi Company. Table 1. Characteristics of recipients Table 1. Characteristics of recipients Disclosures Chen: Bayer: Consultancy, Research Funding. Devine:Genzyme: Research Funding.

Description: Altered DNA methylation is a well-known feature of acute myeloid leukemia (AML) genomes, but the mechanisms underlying these changes and their relevance for AML pathogenesis are unclear. We previously showed that DNMT3A is the predominant de novo methyltransferase expressed in AML cells, and that the DNMT3AR882H mutation in AML creates a dominant negative protein that reduces in vitro DNA methylation activity by ~80%. Since DNMT3A provides themajority of the methylation activity in AML cells, we hypothesized that AML samples with and without DNMT3AR882H could reveal novel insights about the role of this enzyme in AML initiation and progression. We performed whole-genome bisulfite sequencing (WGBS) of 38 primary human AML samples and 17 normal human hematopoietic cell samples, as well as a remission sample from a patient with a persistent DNMT3AR882H mutation, and blood samples from a non-leukemic patient with a constitutional DNMT3AR882H mutation. We first identified 3,848 differentially methylated regions ('DMRs') between DNMT3AR882H and DNMT3AWT AMLs, virtually all of which were hypomethylated in the DNMT3AR882H AMLs. Further, 28% (1,087/3,848) of these DMRs were also hypomethylated when compared to CD34 cells, implying that these regions are truly hypomethylated in the AML cells with the R882H mutation. In contrast, 72% (2,759/3,848) of the DMRs were unmethylated in bothDNMT3AR882H AMLs and CD34 cells, but were hypermethylated in the DNMT3AWT AML samples. These loci were associated with CpG dense regions, suggesting that they represent abnormal CpG island hypermethylation that occurs only in AML samples with wild-type DNMT3A. Analysis of 21 additional primary AML samples with wild-type DNMT3A identified 4,912 hypermethylated regions compared to CD34 cells, of which 4,544 (92%) were significantly less methylated in DNMT3AR882H AMLs, implying that functional DNMT3A mediates abnormal CpG island hypermethylation in AML. WGBS analysis of two non-leukemic hematopoietic samples with DNMT3AR882H mutations was also performed to understand the direct effects of DNMT3AR882H in non-transformed myeloid cells. These samples included peripheral blood (PB) neutrophils and monocytes from a newly identified 9-year old patient with an overgrowth syndrome and developmental delay (Tatton-Brown et. al., Nature Genetics 2014), who was found to have a heterozygous DNMT3AR882H mutation in all skin and peripheral blood cells. His CBC was normal, and he had no evidence of clonal hematopoiesis by exome sequencing. We identified 2,051 DMRs in his PB myeloid cells, all of which were hypomethylated compared to control PB myeloid cells from his healthy 13-year old brother (and also normal CD34 cells), demonstrating that DNMT3AR882H directly causes focal methylation loss. We also performed WGBS on cells expanded from single stem/progenitor cells from an AML patient with a persistent DNMT3AR882H mutation during remission. Expanded cells with DNMT3AR882H were hypomethylated relative to wild-type DNMT3A cells expanded from the same sample. The majority of the hypomethylated regions were also present in the patient's AML cells, implying that DNMT3AR882H-associated hypomethylation in pre-leukemic cells is maintained during AML progression. These findings demonstrate that DNMT3AR882H-associated hypomethylation precedes leukemia development, and may therefore represent an important initiating phenotype for AML. Our data also suggest that the abnormal hypermethylation of CpG islands in AML cells is DNMT3A-dependent, and must occur during disease progression. This hypermethylation is absent in AMLs with DNMT3AR882H, revealing that it is not required for leukemia progression. We therefore propose a model where DNMT3A-dependent DNA methylation in AML cells acts as a 'brake' that prevents abnormal self-renewal; the abnormal CpG island hypermethylation in DNMT3AWT AMLs may be an adaptive response that is ultimately overcome during leukemia progression. The absence of this 'braking' activity in AMLs with DNMT3AR882H may contribute directly to leukemia initiation. The restoration of DNMT3A activity in AML cells with the DNMT3AR882H mutation is therefore a therapeutic goal. Disclosures Spencer: Cofactor Genomics: Consultancy.

Description: Background:Allogeneic hematopoietic cell transplantation is a cornerstone of therapy for hematologic malignancies and often a patient's only curative intent treatment. Following development of post-transplant cyclophosphamide (PTCy) regimens, the use of haploidentical hematopoietic cell transplantation (haplo-HCT) has expanded. While overall outcomes for haploidentical transplantation appear to be excellent, its novel approach brings toxicities that are particular to its biological and clinical milieu. We recently described occurrence of severe cytokine release syndrome (CRS) after haplo-HCT. We further reported that severe CRS was associated with poor clinical outcomes, including transplant related mortality (TRM), overall survival (OS), and neutrophil engraftment (Abboud et al, BBMT, 2016). However, the factors predicting the occurrence of and long-term outcomes of patients who develop severe CRS after haplo-HCT is currently not known. Objective: To describe our clinical experience with CRS in an expanded cohort of haplo-HCT patients, its implication on clinical outcomes and elucidation of possible risk factors for the development of severe CRS. Patients and Methods: We performed a retrospective review of patients who had undergone peripheral blood T-Cell replete haplo-HCT with PTCy from July 2009 through March 2016 at our institution. A total of 137 patients were identified, 51% (74) were male, with a median age at transplant of 52 (19-73), a total of 40% (57) had active disease at the time of transplant. The most common diagnosis was AML (93 pts), followed by ALL (16 pts) and MDS (15 pts). Thirty-one percent (44 pts) had undergone prior transplant. In grading CRS, we used our approach modified from by Lee et al (Blood, 2014). Twenty-two patient, donor and disease characteristics were examined to identify predictors for the development of severe CRS. Results:One hundred and twenty-four (90%) of patients met criteria for CRS, and 26 (19%) suffered from severe (grade 3-4) CRS. Virtually all patients (99%) with CRS suffered from fevers. Patients with severe CRS had a significant delay in neutrophil (p 〈 0.0001) and platelet (p 〈 0.0001) engraftment compared to the patients who developed mild or no CRS (Figure 1A and 1B). Severe CRS was also associated with a high early transplant related mortality; the rate of death before post-transplant day 28 was 6.9 times higher for patients with grade 3-4 CRS compared with those with mild CRS (p 〈 0.0001, Figure 1C). Consistent with these findings, the development of severe CRS was associated with extremely poor survival. Median survival was 3 months for grade 3-4 CRS, 15 months for grade 1-2 CRS, and 13 months for no CRS. One-year OS was 4% for grade 3-4 CRS, 55% for grade 1-2 CRS, and 50% for no CRS (Figure 1D). There was no difference in the cumulative incidence of relapse, acute graft versus host disease, and chronic graft versus host disease (data not shown). A total of nine patients received Anti-IL-6 Therapy with tociluzimab (4 mg/kg of actual body weight), 4 of which suffered from severe CRS. In terms of predictive factors, the development of severe CRS was associated with disease risk index (p=0.037), HCT-CI score (p=0.005) and presence of a previous transplant (p=0.026) by univariate analysis. Risk and severity of CRS did not differ by age, ABO mismatch, age, CMV status of donor, donor sex, T-cell or CD34 cell dose. There was no difference in rates of CRS among patients in remission or with active disease at the time of transplant. Conclusions: Severe CRS after peripheral blood haplo-HCT is associated with high early TRM, poor OS and delayed neutrophil and platelet engraftment. Furthermore, patients with high DRI, high HCT-CI and prior HCT are at a higher risk for the development of severe CRS after haplo-HCT. We have previously shown the safety and potential efficacy of using anti-IL-6 therapy in these patients. Our current results suggest potential benefit to targeting this pathway prophylactically in patients at high risk for the development of severe CRS. Table Patient Characteristics Table. Patient Characteristics Figure CRS impacts neutrophil (A) and platelet (B) engraftment and is associated with high TRM (C) and poor OS (D). Figure. CRS impacts neutrophil (A) and platelet (B) engraftment and is associated with high TRM (C) and poor OS (D). Disclosures DiPersio: Incyte Corporation: Research Funding. Abboud:Gerson and Lehman Group: Consultancy; Merck: Research Funding; Teva: Research Funding, Speakers Bureau; Novartis: Research Funding; Pfizer: Research Funding; Seattle Genetics: Research Funding; Alexion: Honoraria; Baxalta: Honoraria; Pharmacyclics: Honoraria; Takeda: Honoraria; Cardinal: Honoraria. Fehniger:Affimed: Consultancy; Celgene: Research Funding; Fortress Biotech: Consultancy.

Description: Recent success in immunomodulation of cancer has targeted immune checkpoints such as CTLA-4, PD-1 and PDL-1 to enhance adaptive immunity by stimulating production of tumor-selective, cytotoxic T cells. Anti-CD47mAbs enhance innate immunity by increasing the phagocytosis of tumor cells by macrophages leading to processing and presentation of tumor antigens to prime the adaptive T cell response. Many cancers, including hematologic cancers, up-regulate the expression of CD47 presumably to avoid immune destruction. Increased CD47 expression protects cancer cells from phagocytosis by sending a “don't eat me” signal to macrophages via SIRPalpha, an inhibitory receptor that prevents phagocytosis of CD47-bearing cells. CD47mAbs that block the CD47/SIRPalpha interaction (“blocking-only” mAbs) enhance phagocytosis of cancer cells in vitro. We have identified two CD47mAbs, Vx-1000 and Vx-1004, both of which block the CD47/SIRPalpha interaction and promote phagocytosis of tumor cells by macrophages equally well. However, Vx-1004 also has the unique property of killing cancer cells, but not normal blood cells, via a direct, cell-autonomous, cytotoxic mechanism. Therefore, Vx-1004 is a dual-function antibody. Vx-1004 selectively kills a variety of hematologic cancer cells in vitro, while Vx-1000, the blocking-only mAb, does not as assessed by annexin V staining and flow cytometry (Figure 1). In dose-response studies, cell death in leukemia cells was induced in 2 hrs by To determine if the tumor-toxic activity of Vx-1004 confers enhanced efficacy in vivo compared to Vx-1000, we compared them in two mouse hematologic cancer models: murine acute promyelocytic leukemia (APL) and B cell lymphoma (BCL). Briefly, 1x106 GFP-labeled C57BL/6 APL cells were injected IV into wild-type C57BL/6 mice that were then treated IP with 0.4 mg/kg of either Vx-1000 or Vx-1004 on the day of tumor injection and on days 3 and 6 following tumor injection, a very low dose and limited dosing regimen. On day 25, the blood of these mice was analyzed for the number of circulating APL cells. As shown in Figure 2, Vx-1000 did not significantly reduce tumor burden compared to the control group. In contrast, Vx-1004 significantly reduced tumor burden compared to controls, demonstrating greater efficacy of the dual-function CD47mAb. In addition, enhanced efficacy of Vx-1004 compared to Vx-1000 was demonstrated in BCL (Figure 3). In this model, NSG mice were injected with 1x106 murine A20 lymphoma cells subcutaneously and then treated with 0.4mg/kg/day of the CD47mAbs IP for the first five days following tumor injection. In this model, Vx-1000 also failed to inhibit tumor growth compared to controls while Vx-1004 significantly reduced tumor burden at 35 days compared to both the control and Vx-1000 groups, nearly four weeks after treatment was stopped. These data demonstrate increased anti-cancer efficacy with a dual-function CD47mAb that not only blocks the CD47/SIRPalpha interaction to increase phagocytosis of cancer cells, but also selectively kills cancer cells. These studies indicate that dual-function CD47mAbs may have better anti-tumor activity in vivo and support their use in human clinical trials. Figure 1 Figure 1. Disclosures Manning: Corvus Pharmaceutical: Employment, Equity Ownership. Capoccia:Corvus Pharmaceutical: Employment, Equity Ownership. Hiebsch:Corvus Pharmaceutical: Employment, Equity Ownership. Karr:Corvus Pharmaceutical: Employment, Equity Ownership. Frazier:Corvus Pharmaceutical: Consultancy, Equity Ownership.