Citations

Abstract Background: It has been known for approximately 19 years that germline mutations in RUNX1, lead to familial platelet disorder with predisposition to myeloid malignancy (FPD-MM, OMIM 601399). Since that time researchers have identified a broad range of different RUNX1 mutations, in over 100 families. In large families, the diagnosis of malignancy shows variable penetrance among family members with the same mutation; some carriers of RUNX1 mutations do not develop malignancy. The causes of this heterogeneity are currently not known, complicating counselling and risk analysis for individual carriers. Recent advances in genetic sequencing technology applied by many FPD-MM research groups around the world have highlighted their value in understanding the somatic genetic changes that are associated with development of malignancies in germline RUNX1 mutation carriers. Collectively this information could lead to powerful insights essential for more precise risk assessment, monitoring, and therapeutic intervention. Specifically, a growing catalogue of somatic mutations associated with germline RUNX1 malignancy offers the opportunity for informed monitoring of asymptomatic RUNX1 carriers for additional high-risk somatic mutations, in turn providing the possibility for early therapeutic intervention to arrest the leukemic process. The challenge in advancing these goals for FPD-MM is the relative rarity of the disorder in individual populations. Global data sharing in a highly interactive FPD-MM research community offers a solution to this problem that benefits all patients world-wide. Aims: To create a global RUNX1 network through identifying and contacting researchers and clinicians with known and novel germline RUNX1 families, seeking their collaboration to share genomics data. To create a RUNX1.db portal to collectively house and analyse genomics data from germline RUNX1 carriers, with associated phenotype and clinical information, such that researchers have an ongoing means by which to combine their data with those generated by other groups around the world. Methods: RUNX1 network : Through existing collaborative networks, a systematic review of the literature, and referrals from initial contacts, we have identified a global network of researchers managing FPD-MM cases and families. RUNX1.db: We have adapted a custom-built variant analysis platform, VariantGrid, that is a visual web application and database designed to help scientists manage and analyse DNA variants that can be used to aggregate and analyse multiple datasets. Results: Preliminary analysis of aggregated data from the literature suggests there are features of germline RUNX1 syndrome that can be ascertained. These include frequent somatic mutation of RUNX1 in malignancy development, as well as mutations in genes associated with clonal hematopoiesis that may precede development of overt leukemia. This analysis also suggests that different types of germline RUNX1 mutations may be associated with different combinations of somatic mutations in the tumour. To further this analysis, we have identified over 70 groups internationally that either manage RUNX1 families or have identified potential germline carriers through genomics initiatives. This represents a large and growing resource for both scientific studies and clinical programs to benefit individuals with FPD-MM. Many of these groups have generated NGS data sets from patient samples which will be available for analysis through this portal. Further details and activities of the network, and results from the genomics aggregation database will be presented. Conclusion: We have created a global RUNX1 network, aggregated their data, and generated a RUNX1.db genomics portal for the continuous curation of genomics data from germline RUNX1 carriers. A preliminary analysis has already identified specific features of germline RUNX1 mutated malignancies that have clinical importance. Ongoing scientific and clinical studies through the RUNX1 network will enhance the power of aggregated data analysis, with RUNX1.db providing a central link, driving new insights that benefit patients. Disclosures Natsoulis: Imago BioSciences, Inc.: Consultancy, Equity Ownership. Guzman:Cellectis: Research Funding. DiNardo:Bayer: Honoraria; Karyopharm: Honoraria; Celgene: Honoraria; Agios: Consultancy; Medimmune: Honoraria; Abbvie: Honoraria. Borate:Novartis: Consultancy; Agios: Consultancy. Wei:Amgen: Honoraria, Other: Advisory committee, Research Funding; Pfizer: Honoraria, Other: Advisory committee; Celgene: Honoraria, Other: Advisory committee, Research Funding; Abbvie: Honoraria, Other: Advisory board, Research Funding, Speakers Bureau; Servier: Consultancy, Honoraria, Other: Advisory committee, Research Funding; Novartis: Honoraria, Other: Advisory committee, Research Funding, Speakers Bureau. Dokal:MRC, Bloodwise, Telomerase Activator Sciences: Research Funding; The Gary Woodward Dyskeratosis Congenita Trust: Membership on an entity's Board of Directors or advisory committees; Action Medical Research, European School of Haematology: Membership on an entity's Board of Directors or advisory committees; Barts and The London School of Medicine and Dentistry, Queen Mary University of London,: Employment, Research Funding; Telomerase Activator Sciences: Research Funding; Barts and The London, Queen Mary University of London: Employment; Gary Woodward Dyskeratois Congenita Trust: Membership on an entity's Board of Directors or advisory committees. Hiwase:Novartis: Research Funding; Celgene: Research Funding. Branford:Cepheid: Honoraria; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Qiagen: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Kramer:Roche: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; Bayer: Research Funding; Daiichi Sankyo: Consultancy. Owen:Merck: Honoraria; Teva: Honoraria; AbbVie: Research Funding; Pharmacyclics: Research Funding; Janssen: Honoraria, Research Funding; Celgene: Research Funding; AstraZeneca: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Honoraria, Research Funding. Fitzgibbon:Epizyme: Consultancy, Research Funding; Gilead: Consultancy. Rienhoff:Imago BioSciences, Inc.: Employment, Equity Ownership, Membership on an entity's Board of Directors or advisory committees. Kurokawa:Astellas Pharma: Research Funding; Sumitomo Dainippon Pharma: Research Funding; Nippon Sinyaku: Honoraria, Research Funding; Kyowa Hakko Kirin: Honoraria, Research Funding; Eizai: Research Funding; MSD: Honoraria, Research Funding; Ono Pharmaceutical: Honoraria, Research Funding; Pfizer: Research Funding; Takeda Pharmaceutical: Research Funding; Otsuka Pharmaceutical: Research Funding; Teijin Pharma: Research Funding; Chugai Pharmaceutical: Research Funding.

Abstract Introduction: The most effective initial therapy for older adults with CLL has not yet been established due to the lack of comparison of chemoimmunotherapy (CIT) and targeted therapy with the Bruton's Tyrosine Kinase (BTK) inhibitor ibrutinib. CIT has been the gold standard since studies showing that addition of CD20 antibody to chemotherapy prolongs survival. Bendamustine plus rituximab (BR) is one standard, more aggressive CIT regimen for patients (pts) age 65 or older. While ibrutinib has been FDA approved for untreated CLL since 2016, it has only been compared to chlorambucil, which is relatively ineffective, and never before to aggressive CIT. Additionally, the benefit of the addition of rituximab to ibrutinib in this setting has not been prospectively studied in a phase 3 trial. As part of a randomized phase 3 trial, the Alliance sought to answer these important clinical questions. Pts and Methods: Alliance A041202 is a multicenter NCI National Clinical Trials Network phase 3 study comparing BR (Arm 1) with ibrutinib (Arm 2) and the combination of ibrutinib plus rituximab (Arm 3) to determine whether ibrutinib-containing regimens are superior to CIT in terms of PFS. Additionally, this study sought to determine if adding rituximab to ibrutinib would prolong PFS over ibrutinib alone. At time of progression, pts on Arm 1 could cross over to Arm 2. Eligible pts were those age ≥ 65 years with previously untreated, symptomatic CLL. Pts had a CrCl ≥ 40 mL/min, bilirubin ≤ 1.5 x ULN, and no significant life-limiting intercurrent illness or need for warfarin treatment. Pts were stratified based upon Rai stage, Zap-70 methylation performed centrally, and del(17)(p13.1) or del(11)(q22.3) by local interphase cytogenetics and were randomized 1:1:1 to each arm. With 166 pts per arm, the trial was powered to detect an improvement in 2-year PFS from 61% in Arm 1 to 75% in Arms 2 or 3 (HR=0.586) using two one-sided log-rank tests with type I error rate of 2.5% and 90% power. The Alliance Data and Safety Monitoring Board approved the data release after meeting the protocol-defined efficacy threshold at a planned interim analysis with a one-sided critical value of 0.001538. These data were locked July 2, 2018; updated results will be presented at the meeting. Results: Between 12/9/2013 and 5/16/2016, 547 pts were registered and randomized (Arms 1: 183, 2: 182, and 3: 182). Median age was 71 years and 67% of pts were men. High-risk Rai stage (stage III/IV) was seen in 54%, unmethylated Zap-70 in 53%, and del(17p) or del(11q) by local FISH in 28%. Local vs centralized FISH was performed for del(11q) and del(17p) with agreement between local and central results in 94% (Kappa=0.80) and 97% (Kappa=0.76) of pts, respectively. 525 (96%) pts were eligible and included in the primary PFS analysis (Arms 1: 176, 2: 178, and 3: 171). With median follow-up of 32 months (mo), median PFS was 41 mo in Arm 1 and has not been reached in Arms 2 or 3 (HR comparing Arm 2 to 1 is 0.40 with one-sided p<0.0001; HR comparing Arm 3 to 1 is 0.41 with one-sided p<0.0001; HR comparing Arm 3 to 2 is 1.01 with one-sided p=0.48). 2-year PFS estimates were 74%, 87% in 2, and 88% in Arms 1, 2, and 3 respectively. At this time, there are no significant differences in overall survival (OS) among arms (p=0.87), median OS has not been reached for any arm, and 2-year OS estimates were 95%, 90%, and 94% in Arms 1, 2, and 3, respectively. Adverse events (AEs) were compared among arms using Fisher's exact tests. Grade 3+ treatment-emergent AEs were seen in 428 of 537 evaluable pts with 61%, 41%, and 38% of pts experiencing Grade 3+ heme AEs (p<0.0001) and 60%, 72%, and 71% of pts experiencing Grade 3+ non-heme AEs (p=0.03) in Arms 1, 2, and 3 respectively. Grade 5 AEs were seen in 5 (2.8%), 14 (7.8%), and 14 (7.7%) pts (p=0.07). Unexplained or unwitnessed death over the entire observation period was seen in 2 (1.1%), 7 (3.9%), and 4 (2.2%) pts (p=0.24) in Arms 1, 2, and 3 respectively. Conclusions: This international phase 3 trial demonstrates that ibrutinib produces superior PFS to standard CIT in older pts with CLL and justifies it as a standard of care treatment for pts age 65 and older. The addition of rituximab does not prolong PFS with ibrutinib. While ibrutinib represents a major therapeutic advance, toxicities and also cost justify future efforts to reduce the need for long-term continuous treatment. Support: K23CA178183, R01CA183444, U10CA180821, U10CA180882, U24CA196171, Clinicaltrials.gov identifier: NCT01886872 Figure. Figure. Disclosures Ding: Merck: Research Funding. Bartlett:Astra Zeneca: Research Funding; ImaginAB: Research Funding; Seattle Genetics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pharmacyclics: Research Funding; Bristol-Meyers Squibb: Research Funding; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Genentech: Research Funding; Pharmacyclics: Research Funding; Affimed: Research Funding; Janssen: Research Funding; Novartis: Research Funding; Merck & Co: Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Acerta: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Immune Design: Research Funding; Forty Seven: Research Funding; Novartis: Research Funding; Millennium: Research Funding. Brander:BeiGene: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; TG Therapeutics: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Genentech: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Novartis: Consultancy, Other: DSMB; AbbVie: Consultancy, Honoraria, Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; Pharmacyclics, an AbbVie Company: Consultancy, Honoraria, Research Funding; Teva: Consultancy, Honoraria; Acerta: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding; DTRM: Other: Institutional research funding for non investigator initiated clinical trial, Research Funding. Barr:AbbVie, Gilead: Consultancy. Parikh:Gilead: Honoraria; Pharmacyclics: Honoraria, Research Funding; MorphoSys: Research Funding; Janssen: Research Funding; AstraZeneca: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Coutre:Celgene: Research Funding; Janssen: Consultancy, Honoraria, Research Funding; Pharmacyclics LLC, an AbbVie Company: Honoraria, Research Funding; Gilead: Research Funding; Beigene: Consultancy; AbbVie: Consultancy, Research Funding. Lozanski:Novartis: Research Funding; BI: Research Funding; Genentech: Research Funding; Stem Line: Research Funding; Coulter: Research Funding; Beckman: Research Funding. Larson:Ariad/Takeda: Consultancy, Research Funding; BristolMyers Squibb: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Novartis: Consultancy, Research Funding. Erba:Amgen: Research Funding; Juno: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Daiichi Sankyo: Consultancy, Research Funding; MacroGenics: Consultancy; Juno: Research Funding; Janssen: Research Funding; Seattle Genetics: Consultancy, Research Funding; Janssen: Research Funding; Juno: Research Funding; Agios: Consultancy, Speakers Bureau; MacroGenics: Consultancy; Incyte: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Research Funding; Takeda/Millenium: Research Funding; Novartis: Consultancy, Speakers Bureau; Takeda/Millenium: Research Funding; Incyte: Consultancy, Speakers Bureau; MacroGenics: Consultancy; Celgene: Consultancy, Speakers Bureau; Janssen: Research Funding; Novartis: Consultancy, Speakers Bureau; Celgene: Consultancy, Speakers Bureau; Astellas: Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; MacroGenics: Consultancy; Daiichi Sankyo: Consultancy, Research Funding; Pfizer: Consultancy, Other: grant; Astellas: Research Funding; Juno: Research Funding; Janssen: Research Funding; Novartis: Consultancy, Speakers Bureau; Amgen: Research Funding; Agios: Consultancy, Speakers Bureau; Astellas: Research Funding; Agios: Consultancy, Speakers Bureau; Novartis: Consultancy, Speakers Bureau; Amgen: Research Funding; Pfizer: Consultancy, Other: grant; Pfizer: Consultancy, Other: grant; Astellas: Research Funding; Amgen: Research Funding; Agios: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Incyte: Consultancy, Speakers Bureau; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Pfizer: Consultancy, Other: grant; Jazz: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Seattle Genetics: Consultancy, Research Funding; Jazz: Consultancy, Speakers Bureau; Seattle Genetics: Consultancy, Research Funding; Celgene: Consultancy, Speakers Bureau; Immunogen: Consultancy, Research Funding; Takeda/Millenium: Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee; Celgene: Consultancy, Speakers Bureau; Takeda/Millenium: Research Funding; Daiichi Sankyo: Consultancy, Research Funding; Glycomimetics: Consultancy, Other: Chair, Data and Safety Monitoring Committee. Owen:Janssen: Honoraria, Research Funding; Celgene: Research Funding; AstraZeneca: Honoraria, Research Funding; Pharmacyclics: Research Funding; F. Hoffmann-La Roche Ltd: Honoraria, Research Funding; AbbVie: Research Funding; Merck: Honoraria; Teva: Honoraria. Abramson:Bayer: Consultancy; Novartis: Consultancy; Merck: Consultancy; Karyopharm: Consultancy; Seattle Genetics: Consultancy; Verastem: Consultancy; Humanigen: Consultancy; Juno Therapeutics: Consultancy; Gilead: Consultancy; Celgene: Consultancy; Amgen: Consultancy.

Abstract Introduction: Carfilzomib (CFZ) is a structurally- and mechanistically-novel proteasome inhibitor (PI) of the peptide epoxyketone class that exhibits a high level of selectivity for the unique N-terminal threonine active sites within the proteasome. CFZ is similar to bortezomib (BTZ; VELCADE®), in that it is a potent inhibitor of the chymotrypsin-like activity, but unlike BTZ, CFZ has shown minimal cross-reactivity with the other catalytic sites within the proteasome or across other protease classes. Preclinical human tumor xenograft models indicate that consecutive day (D1, D2) dosing resulting in 48 hours of proteasome suppression was superior to split dosing (D1, D4). Methods: This phase 1 sequential dose escalation trial tested an intensive proteasome inhibition schedule with CFZ administered as an intravenous push (IVP) daily (QD) for 5 consecutive days on a 14 day cycle. The doses administered ranged from 1.2 mg/m2 to 20 mg/m2. Multiple myeloma (MM), non-Hodgkin’s lymphoma (NHL) that included mantle cell lymphoma (MCL), Hodgkin’s disease (HD), or Waldenström’s macroglobulinemia (WM) were eligible if they had relapsed after 2 or more prior therapies. Results: A total of 29 subjects have been treated. The minimal effective dose (MED) was 11 mg/m2. A maximum of 80% proteasome inhibition was achieved in peripheral blood and mononuclear cells at ≥15 mg/m2. Five responses have occurred in 14 patients (6 MM, 3 MCL, 1 WM, 4 NHL) enrolled at ≥ the MED: 1 MM partial response (PR), 2 MM minimal responses (MR), 1 WM MR and one macroscopic CR in a patient with gastrointestinal MCL. Responses occurred in patients whose disease had failed therapy with BTZ, immunomodulatory agents, and stem cell transplant. Four NHL patients have had stable disease and remained on treatment for up to 7 months. Dose limiting toxicity reported at 20 mg/m2 included febrile neutropenia (reversible) and grade 4 thrombocytopenia. Grade 3 (25%) or grade 4 events (8%) were primarily hematologic events. Most withdrawals occurred due to the inconvenience of frequent visits, or progressive disease. Conclusions: This study demonstrates that intensive CFZ dosing leading to sustained proteasome inhibition is well tolerated. The selectivity of the epoxyketone class of PI may promote a favorable safety profile. Furthermore, antitumor responses in heavily pretreated patients suggest non-cross resistant activity. Phase 2 trials in MM and solid tumors are proceeding with an alternate IV schedule. An oral agent suitable for frequent dosing schedules is under development.

Abstract A 73-year-old woman with metastatic transitional cell carcinoma of the bladder developed vaginal bleeding a few days after undergoing radical cystectomy. She had no other signs of mucocutaneous bleeding. Coagulation studies revealed a markedly prolonged thrombin time (greater than 600 seconds), a slightly prolonged reptilase time (20 seconds), and mildly elevated fibrinogen (4.39 g/L), and fibrin D-dimer (200 to 500 ng/mL) levels. Treatment of the patient's plasma in vitro with protamine or barium sulfate normalized the thrombin time. The anticoagulant activity corresponded to 0.15 heparin U/mL when measured by a thrombin time assay using normal plasma as substrate and standardized with porcine heparin. The anticoagulant was quantitatively bound to and subsequently eluted with 1 mol/L NaCl from quaternary aminoethyl (QAE) Sephadex, and then isolated by affinity chromatography on immobilized antithrombin III. The isolated anticoagulant was shown to be sensitive to heparinase digestion. Therefore, the inhibitor has functional and chemical properties similar to those of high-affinity heparin. Thus far, this is the only anticoagulant of this type isolated from the plasma of a patient bearing a tumor other than plasma cell myeloma.

A 73-year-old woman with metastatic transitional cell carcinoma of the bladder developed vaginal bleeding a few days after undergoing radical cystectomy. She had no other signs of mucocutaneous bleeding. Coagulation studies revealed a markedly prolonged thrombin time (greater than 600 seconds), a slightly prolonged reptilase time (20 seconds), and mildly elevated fibrinogen (4.39 g/L), and fibrin D-dimer (200 to 500 ng/mL) levels. Treatment of the patient's plasma in vitro with protamine or barium sulfate normalized the thrombin time. The anticoagulant activity corresponded to 0.15 heparin U/mL when measured by a thrombin time assay using normal plasma as substrate and standardized with porcine heparin. The anticoagulant was quantitatively bound to and subsequently eluted with 1 mol/L NaCl from quaternary aminoethyl (QAE) Sephadex, and then isolated by affinity chromatography on immobilized antithrombin III. The isolated anticoagulant was shown to be sensitive to heparinase digestion. Therefore, the inhibitor has functional and chemical properties similar to those of high-affinity heparin. Thus far, this is the only anticoagulant of this type isolated from the plasma of a patient bearing a tumor other than plasma cell myeloma.

Abstract In 12 normal subjects, DNA and RNA synthesis by individual marrow cells was studied in vitro by autoradiography after short-term incubation with tritiated nucleosides. The DNA labeling index and RNA synthesis rate were highest in normal immature cells. The DNA index was zero in all mature cells, including small lymphocytes and plasma cells. In the most actively proliferating normal immature cells, the RNA synthesis rate was about 5 times higher than in normal plasma cells. Since both normal immature cells and plasma cells are characterized by a high content of RNA and active protein synthesis, the results of the present study suggest that a high RNA turnover may not be necessary for protein synthesis to proceed in nonproliferating, protein-producing marrow cells. In 10 patients with myeloma and in two patients with primary macroglobulinemia, the abnormal plasma cells were found to be labeled with H3thymidine in each instance. The RNA synthesis rate was about 3 times greater in plasmocytoid myeloma cells than in mature plasma cells of normal marrows, and also about 3 times greater in lymphocytoid myeloma cells than in mature lymphocytes of normal marrows. The abnormal cells in the lymphoplasmocytic disorders apparently differ from their counterparts in normal marrows not only by a higher proliferative potential, but also by a much greater rate of RNA synthesis. In actively dividing normal bone marrow cells, high values for both DNA and RNA synthesis were found. By contrast, in the neoplastic lymphoplasma cells studied, a discrepancy was noted between relatively low values of DNA synthesis and high values of RNA synthesis. Production of abnormal proteins within long-lived neoplastic plasmocytic cells may account for this finding.

Abstract When oxalated or resin-decalcified human plasma was adsorbed with barium sulfate, equilibrated with 0.0175M phosphate buffer (pH 6.3), and chromatographed through diethylaminoethyl (DEAE) cellulose, most of the plasma’s fibrinogen emerged from the column and factor XII was detected. No factor VIII was found. A second buffer phase, in which 0.04M phosphate buffer (pH 5.9) was used, removed more protein but not fibrinogen or factor VIII. A third phase, 0.10M phosphate buffer (pH 5.6), produced additional fibrinogen and, unlike the first fibrinogen fraction, factor XIII; but again, no factor VIII. A fourth and final phase, 0.40 to 0.50M phosphate buffer (pH 5.3), removed factors VIII and V, and the eluate contained no fibrinogen. Although separation of fibrinogen into two components required the four-buffer system, maximal yields of factor VIII were achieved by compressing the first three buffer phases into one. Specific activities of about 50-fold, from large volumes of plasma, and 200-fold, from small volumes, were obtained. Refined factor VIII was unstable unless citrate was added to a concentration of 0.4 per cent.

Abstract Introduction The phagocytic activity of macrophages is regulated by activating ("eat") and inhibitory ("do not eat") signals. Under normal physiologic conditions, the ubiquitously expressed cell surface antigen CD47 suppresses phagocytosis by binding to signal regulatory protein alpha (SIRPα) on macrophages. It is hypothesized that overexpression of CD47 by cancer cells enables immune evasion. Blockade of CD47 results in phagocytosis of cells bearing "eat" signals and primes effective anti-tumor T cell responses. TTI-621(SIRPαFc)is a soluble recombinant fusion proteinconsisting of the CD47 binding domain of human SIRPα linked to the Fc region of human IgG1designed to both: 1) block the CD47 "do not eat" signal, and 2) engagemacrophage Fcγ receptors with IgG1 Fc to enhance phagocytosis and antitumor activity.In vitro, TTI-621 binds to normal human cells, platelets, a wide range of human primary tumor cells and cell lines, but only minimally to human erythrocytes. TTI-621 selectively promotes macrophage-mediated phagocytosis of hematologic and solid tumors over that observed with normal monocytes, and exhibits antitumor activity in xenograft mouse models. Methods A first-in-human, phase 1, open label, multicenter study (NCT02663518) is ongoing to evaluate the safety and tolerability, and to identify the maximum tolerated dose of TTI-621 in patients (pts) with relapsed/refractory lymphomas using a 3+3 dose-escalation design. Once the optimal dose has been determined in the dose-escalation phase, multiple expansion cohorts will be enrolled comprising pts with various relapsed/refractory hematologic malignancies. Assessments include peripheral receptor occupancy, serum cytokine levels, pharmacokinetics, and immunogenicity. Eligible pts are adults with advanced, measurable, hematologic malignancies, who have progressed on standard anticancer therapy or for whom no other approved therapy exists. Pts are required to have baseline hemoglobin ≥10 g/dL, platelets ≥75 x 109/L, and be transfusion- and growth factor-independent. Pts with cutaneous T-cell lymphoma, high-grade lymphoma, and acute promyelocytic leukemia are excluded. TTI-621 is administered IV once weekly at protocol-defined doses. Treatment may continue until disease progression or unacceptable toxicity. Results Eleven pts (6M/5F, age 21-72 years) have been enrolled as of the data cut-off date of 28 July 2016. Lymphoma diagnoses included Hodgkin (N=4), diffuse large B cell (DLBCL) (N=4), follicular (N=2), and mantle cell (N=1). Treatment has been reasonably well tolerated by pts in the 0.05 mg/kg (N=3), 0.1 mg/kg (N=3), and 0.3 mg/kg (N=5) dose cohorts. The majority of pts experienced mild to moderate infusion-related events. Hemoglobin levels have remained stable or improved with treatment. Transient, dose-dependent decreases in platelets and leukocytes occurred in the hours following infusion in all pts without clinical sequelae. The 0.3 mg/kg dose was associated with reversible, dose-limiting toxicity (DLT) in 2 of 5 pts: one pt with G3 elevated ALT/AST and G4 platelet count, and a second pt with G4 platelet count who was transfused. Dosing at 0.2 mg/kg is now being explored. Aside from the DLTs and 2 non-DLT G3 platelet count (all in 0.3 mg/kg cohort), treatment-related adverse events have been ≤G2. CD47 receptor occupancy increased with each cohort, peaking at the end of infusion and remaining detectable 24 hrs after the 1st infusion in Cohort 3. Macrophage-associated cytokines, including MIP-1α and MIP-1β, increased during the 4 hrs after infusion. Six pts continue to receive weekly infusions of TTI-621; one pt with DLBCL and another with FL have experienced progression-free intervals of 161 and 70 days, respectively. Conclusions TTI-621 has been reasonably well tolerated. Pts retained stable hemoglobin levels consistent with minimal drug binding to erythrocytes. Manageable, dose-dependent thrombocytopenia was likely due to increased phagocytic clearance of platelets. TTI-621 binds to CD47+ cells in a dose-dependent manner, potently yielding increases in cytokines associated with augmented phagocytic activity. Enrollment continues at the 0.2 mg/kg dose level; updated data will be provided at the meeting. Figure 1 Figure 1. Figure 2 Figure 2. Disclosures Ansell: BMS, Seattle Genetics, Merck, Celldex and Affimed: Research Funding. Chen:Seattle Genetics: Consultancy, Honoraria, Research Funding, Speakers Bureau; Millenium: Consultancy, Research Funding, Speakers Bureau; Genentech: Consultancy, Speakers Bureau; Merck: Consultancy, Research Funding. Flinn:Janssen: Research Funding; Pharmacyclics LLC, an AbbVie Company: Research Funding; Gilead Sciences: Research Funding; ARIAD: Research Funding; RainTree Oncology Services: Equity Ownership. O'Connor:Bristol Myers Squibb: Research Funding; Spectrum: Research Funding; TG Therapeutics: Research Funding; Mundipharma: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Seattle Genetics: Research Funding; Bristol Myers Squibb: Research Funding; Mundipharma: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; TG Therapeutics: Research Funding. Johnson:Trillium Therapeutics: Employment. Irwin:Hoffmann La Roche: Employment, Equity Ownership; Trillium Therapeutics: Employment, Equity Ownership. Petrova:Trillium Therapeutics Inc: Employment, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Uger:Trillium Therapeutics: Employment, Membership on an entity's Board of Directors or advisory committees, Patents & Royalties. Sievers:Seattle Genetics: Employment, Equity Ownership; Trillium Therapeutics: Employment, Equity Ownership; MEI Pharma: Consultancy.