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Biomedical robotic systems continue to hold unlimited potential for surgical procedures. Robotized laser endoscopic tools provide surgeons with increased accuracy in the laser ablation of tissue and tumors. The research here catalogs the design and implementation of a new laser endoscopic tool for tissue ablation. A novel feature of this new device is the inclusion of a feedback loop that measures the position of the laser beam via a photodetector sensor. The scale of this new device was governed by the dimensions of the photodetector sensor. The tip of the laser's fiber optic cable is controlled by the torque interaction between permanent magnet rings surrounding the fiber-optic and the custom-designed solenoid coils. Prior to building the physical test-bed, the system was modeled and simulated using comsol software. In preclinical trials, the physical experimental results showed that the designed prototype laser scanner system accurately tracks different ablation patterns and gives a consistent output position for the laser beam; however, the heat diffusion into the tissue around the desired line of the geometric shape would give wider ablation margins than was desirable.

170 Background: CRC is the 4th leading cause of global cancer-related deaths, and novel therapeutic strategies for advanced CRC are urgently needed. Adoptive cell therapy (ACT) is effective in treating hematological malignancies; however, ACT in solid tumors is hindered by target antigen identification, restricted migration into tumors, and survival in the tumor microenvironment (TME) due to immunosuppressive signals and scarcity of nutrients. NK cells are central to anti-tumor immunity and can directly eliminate tumor cells without prior sensitization. Through cytokine reprogramming, NK cells can also gain memory-like features that augment their anti-tumor potential. WU-NK-101 is a cytokine-reprogrammed, expanded, cryopreserved, off-the-shelf NK cell product derived from peripheral blood mononuclear cells, with no additional engineering. Methods: WU-NK-101 ± Ctx was evaluated in vitro in 2D cytotoxicity assays in complete (N) and TME-aligned medias. WU-NK-101 cytotoxicity was further assessed against primary CRC surgical samples in native-TME-aligned 3D assays. Proteomic analysis was performed using tandem-mass spectrometry. In vivo efficacy of WU-NK-101 ± Ctx was evaluated in NSG mice bearing LoVo xenograft CRC tumors. Cell trafficking/penetration to TME was measured by tracking labeled WU-NK-101 ± trastuzumab in NSG mice bearing subcutaneous SKOV-3 xenografts. Results: Compared to conventional NK cells (cNK), WU-NK-101 had a unique phenotype consistent with rapid activation and proliferation (higher expression of activating receptors, Ki67, and GZMB), and showed enhanced in vitro cytotoxicity. WU-NK-101 also exhibited potent cytotoxicity against LoVo CRC tumors in vivo, which was further enhanced in combination with Ctx. Antibody combination improved WU-NK-101 penetration, and persistence in TME. WU-NK-101’s metabolic profile was consistent with aerobic (Warburg) glycolysis, potentially facilitating effector functions in the TME. WU-NK-101 also showed enhanced metabolic fitness and flexibility, as proteins in several metabolic pathways were upregulated in TME vs N media. Consistent with this, WU-NK-101 had increased cell-surface expression of nutrient transporters. While cNK and T cells cytotoxicity was significantly suppressed in TME-aligned media, WU-NK-101’s function was not impacted. Conclusions: We show that WU-NK-101 exerted potent activity against CRC, and in combination with Ctx showed improved intra-tumor infiltration/persistence and anti-tumor activity. Also, WU-NK-101 cells had enhanced metabolic fitness/flexibility and decreased susceptibility to immunosuppression, overcoming limitations encountered by ACT for solid tumors. A Phase 1b clinical trial is in development, which may reshape ACT in CRC and other EGFR-expressing tumors. [Table: see text]

Children with acute myeloid leukemia (AML) have a poor prognosis despite the intensification of chemotherapy. Future efforts to improve outcomes should focus on more precise targeting of leukemia cells. CD123, or IL3RA, is expressed on the surface of nearly all pediatric AML samples and is a high-priority target for immunotherapy. The efficacy of an investigational dual-affinity retargeting antibody (DART) molecule (CD123 × CD3; MGD006 or flotetuzumab) was assessed in two distinct patient-derived xenograft (PDX) models of pediatric AML. MGD006 simultaneously binds to CD123 on target cells and CD3 on effector T cells, thereby activating T cells and redirecting them to induce cytotoxicity in target cells. The concurrent treatment of cytarabine and MGD006 was performed to determine the effect of cytarabine on T-cell counts and MGD006 activity. Treatment with MGD006 along with an allogeneic human T-cell infusion to act as effector cells induced durable responses in both PDX models, with CD123 positivity. This effect was sustained in mice treated with a combination of MGD006 and cytarabine in the presence of T cells. MGD006 enhanced T-cell proliferation and decreased the burden of AML blasts in the peripheral blood with or without cytarabine treatment. These data demonstrate the efficacy of MGD006 in prolonging survival in pediatric AML PDX models in the presence of effector T cells and show that the inclusion of cytarabine in the treatment regimen does not interfere with MGD006 activity.

Introduction. Approximately 40% of patients (pts) with newly diagnosed AML either fail to achieve complete remission with intensive induction therapy or experience disease recurrence after a short remission (CR1 6 months), the probability of response for PIF/ER pts is particularly poor (~12%) with median expected overall survival of ~3.5 month and no approved therapy for this specific population. We have recently shown that increased immune infiltration of the tumor microenvironment (TME) is associated with induction failure and poor prognosis; conversely, an infiltrated TME predisposes for immunotherapy response1. We provide an update of the first-in-human study of flotetuzumab (FLZ), an investigational CD123 x CD3 bispecific DART® molecule currently in clinical development for PIF/ER AML pts. Methods. In this phase of the study, PIF is defined as being refractory to induction with: ≥1 high-intensity cytarabine-based chemotherapy (CTx) cycles, or ≥2 but ≤4 Bcl-2 inhibitor-based combinations, or gemtuzumab ozogamicin only. ER is defined as relapse following CR1 < 6 months. Pts who receive up to one prior salvage attempt are included. Pts whose AML recurred following HSCT are excluded. The recommended Phase 2 dose (RP2D) of FLZ is 500 ng/kg/day administered as a continuous infusion in 28-day cycles following a step-up ('priming') lead-in dose during Cycle 1 Week 1. Disease status is assessed by modified IWG criteria. Duration of response is measured from initial response to relapse or death. Results. As of July 1, 2020, 38 PIF/ER (as defined above) AML patients have been treated at the RP2D (median age 63yrs [range 28-81]; 31.6% [12] pts female). Most pts (63.2%, 24/38) were PIF and the large majority (94.7%, 36/38) had non-favorable risk by ELN 2017 criteria (25 pts adverse, 11 pts intermediate); 34.2% (13/38) had secondary AML. For ER pts, median duration of CR1 was 2.9 months (range: 0.7-4.0 months). Cytokine release syndrome (CRS) was the most frequently reported treatment related adverse event (TRAE), with all pts experiencing mild-to-moderate (grade ≤ 2) CRS. No grade ≥ 3 CRS events have been reported in this cohort. Most CRS events (51.5%) occurred in the first week of treatment during step-up dosing. The incidence of CRS progressively decreased during dosing at RP2D (34.8% in week 2, 4.5% in week 3, and 6.1% in week 4), allowing outpatient treatment in most cases. Neurologic AEs have been infrequent, with the most prominent event being grade 1 or grade 2 headache in 23.7% (9/38) treated at the RP2D. Two pts experienced grade 3 confusion of short duration (1-2 days) that was fully reversible. Over half (57.9%) of pts had evidence of antileukemic activity (reduction in blast count) with a median decrease of 92.7% in BM blasts (Fig. 1). The overall complete response rate (CRR, Conclusion: FLZ demonstrated encouraging activity in pts with PIF/ER AML, a population with poor prognosis and high unmet medical need, with 42.1% achieving CRR and over half of those receiving a stem cell transplant. Treatment is tolerable with a minimum 8 day inpatient treatment. The study is currently enrolling patients [NCT02152956] 1 Vadakekolathu J, Minden MD, Hood T, Church SE, Reeder S, Altmann H et al. Immune landscapes predict chemotherapy resistance and immunotherapy response in acute myeloid leukemia. Sci Trans Med 2020. Disclosures Aldoss: abbvie: Consultancy, Research Funding; agios: Honoraria; kite: Consultancy; autolus limited: Consultancy; JAZZ: Honoraria, Speakers Bureau; Amgen: Consultancy; Agios: Consultancy. Uy:Genentech: Consultancy; Agios: Consultancy; Pfizer: Consultancy; Jazz Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Astellas Pharma: Honoraria. Emadi:Amgen: Membership on an entity's Board of Directors or advisory committees; NewLink Genetics: Research Funding; Jazz Pharmaceuticals: Research Funding; Genentech: Membership on an entity's Board of Directors or advisory committees; KinaRx: Other: co-founder and scientific advisor; Servier: Membership on an entity's Board of Directors or advisory committees. Walter:Aptevo Therapeutics: Research Funding. Foster:Daiichi Sankyo: Consultancy; Bellicum Pharmaceuticals: Research Funding; Macrogenics: Consultancy, Research Funding. Arellano:Hanmi: Research Funding; Gilead Sciences, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cephalon Oncology: Research Funding. Wieduwilt:Amgen: Research Funding; Macrogeneics: Research Funding; Leadiant: Research Funding; Merck: Research Funding; Shire: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees. Michaelis:Jazz Pharmaceuticals: Research Funding. Stiff:Kite, a Gilead Company: Research Funding; Gamida Cell: Research Funding; Atara: Research Funding; Unum: Research Funding; Delta-Fly: Research Funding; Macrogenics: Research Funding; Amgen: Research Funding. Advani:Novartis: Consultancy, Other: advisory board; Pfizer: Honoraria, Research Funding; Takeda: Research Funding; OBI: Research Funding; Kite: Other: Advisory board/ honoraria; Amgen: Consultancy, Other: steering committee/ honoraria, Research Funding; Seattle Genetics: Other: Advisory board/ honoraria, Research Funding; Immunogen: Research Funding; Glycomimetics: Consultancy, Other: Steering committee/ honoraria, Research Funding; Macrogenics: Research Funding; Abbvie: Research Funding. Wermke:MacroGenics: Honoraria. Erba:AbbVie, Daiichi Sankyo, Forma, ImmunoGen, Jazz Pharmaceuticals, MacroGenics, Novartis, PTC: Research Funding; Glycomimetics: Other: member of Scientific Steering Committee; Celgene: Other: chair of the Scientific Steering Committee; Covance (AbbVie): Other: chair of the Independent Review Committee; AbbVie, Agios, Celgene, Incyte, Jazz Pharmaceuticals, and Novartis: Speakers Bureau; AbbVie, Agios, Amgen, Astellas, Celgene, Daiichi Sankyo, Glycomimetics, ImmunoGen, Incyte, Jazz Pharmaceuticals, MacroGenics, Novartis, and Pfizer: Consultancy. Topp:Amgen, Boehringer Ingelheim, KITE, Regeneron, Roche: Research Funding; Amgen, KITE, Novartis, Regeneron, Roche: Consultancy. Ravandi:Abbvie: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Macrogenics: Research Funding; Celgene: Consultancy, Honoraria; AstraZeneca: Consultancy, Honoraria; Orsenix: Consultancy, Honoraria, Research Funding. Muth:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Collins:IQVIA: Other: I have worked as a contractor for IQVIA in the past, within the past 24 months.; MacroGenics: Current equity holder in publicly-traded company, Other: I currently work as a contractor for MacroGenics. Guo:Macrogenics: Current Employment. Tran:MacroGenics: Current Employment. Kaminker:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Patel:MacroGenics: Current Employment. Bakkacha:MacroGenics: Current Employment. Jacobs:MacroGenics: Current Employment. Seiler:MacroGenics: Current Employment. Rutella:Kura Oncology: Research Funding; MacroGenics Inc.: Research Funding; NanoString Technologies Inc.: Research Funding. Bonvini:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Davidson-Moncada:Macrogenics: Current Employment. DiPersio:Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees.

We have recently shown that bone marrow (BM) RNA profiles stratify patients with acute myeloid leukemia (AML) into immune-infiltrated and immune-depleted subtypes and that type I/II interferon (IFN)-related gene signatures associate with complete response to flotetuzumab (FLZ), an investigational CD123×CD3 bispecific DART molecule. Within the AML tumor microenvironment CD8+ T cells exhibit features of immune exhaustion and senescence (IES). IES are dysfunctional states driven by metabolic alterations in the tumor microenvironment (TME) and emerging targets for cancer immunotherapy. The aim of the current study was to determine whether IES predicts response of relapsed-refractory (R/R) AML to FLZ in the CP-MGD006-01 clinical trial. Based on prior knowledge and gene set enrichment analysis, we derived a 61-gene IES signature score from RNA-sequencing datasets (TCGA and Beat-AML Master Trial; 162 and 281 patients, respectively). The immunotherapy cohort included 139 BM samples from 71 patients with R/R AML treated with FLZ at the RP2D of 500 ng/kg/day (NCT02152956). BM samples were collected at time of study entry (n=71; n=66 with response data) and longitudinally post-cycle (PC)1 (n=40), PC2 (n=18), PC3 and 4 (n=4) and end of treatment (n=6). AML status at study entry was classified as primary induction failure (PIF, defined as lack of response to at least 2 induction treatment cycles), and early (ER) or late relapse (LR), defined as complete remission (CR) of 50% decrease or decrease to 5-25% BM blasts. RNAs were profiled on the PanCancer IO 360™ gene expression panel on the nCounter® platform. Formalin-fixed paraffin embedded BM biopsies were profiled using the human IO protein and RNA panels on the GeoMx® digital spatial profiler (DSP). The 61 genes in the IES signature included T/NK-cell markers (granzymes, CD8A, KLRD1, KLRK1), immune checkpoints (ICOS, CTLA4, EOMES), IFNG and IFN-stimulated genes (CXCR6, IFIH1, IL10RA, GBP1), and were enriched in KEGG pathways related to Th1/Th2 differentiation, TCR signaling, cytokine-cytokine receptor interaction, NK-mediated cytotoxicity and CD28 costimulation (false discovery rate In conclusion, features of IES were associated with response to FLZ. T-cell functional rejuvenation by FLZ could benefit patients with R/R AML by counteracting pre-existing immune dysfunction. Figure Disclosures Church: NanoString Technologies, Inc.: Current Employment. Uy:Pfizer: Consultancy; Agios: Consultancy; Genentech: Consultancy; Jazz Pharmaceuticals: Consultancy; Astellas Pharma: Honoraria; Daiichi Sankyo: Consultancy. Emadi:Genentech: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; NewLink Genetics: Research Funding; Jazz Pharmaceuticals: Research Funding; KinaRx: Other: co-founder and scientific advisor; Servier: Membership on an entity's Board of Directors or advisory committees. Walter:Aptevo Therapeutics: Research Funding. Foster:Bellicum Pharmaceuticals: Research Funding; Macrogenics: Consultancy, Research Funding; Daiichi Sankyo: Consultancy. Arellano:Cephalon Oncology: Research Funding; Hanmi: Research Funding; Gilead Sciences, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees. Wieduwilt:Amgen: Research Funding; Leadiant: Research Funding; Merck: Research Funding; Shire: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Macrogeneics: Research Funding. Michaelis:Jazz Pharmaceuticals: Research Funding. Stiff:Kite, a Gilead Company: Research Funding; Gamida Cell: Research Funding; Atara: Research Funding; Unum: Research Funding; Delta-Fly: Research Funding; Macrogenics: Research Funding; Amgen: Research Funding. Advani:Takeda: Research Funding; Immunogen: Research Funding; Glycomimetics: Consultancy, Other: Steering committee/ honoraria, Research Funding; Macrogenics: Research Funding; Abbvie: Research Funding; Seattle Genetics: Other: Advisory board/ honoraria, Research Funding; Amgen: Consultancy, Other: steering committee/ honoraria, Research Funding; Kite: Other: Advisory board/ honoraria; Pfizer: Honoraria, Research Funding; Novartis: Consultancy, Other: advisory board; OBI: Research Funding. Wermke:MacroGenics: Honoraria. Erba:AbbVie, Daiichi Sankyo, Forma, ImmunoGen, Jazz Pharmaceuticals, MacroGenics, Novartis, PTC: Research Funding; AbbVie, Agios, Celgene, Incyte, Jazz Pharmaceuticals, and Novartis: Speakers Bureau; AbbVie, Agios, Amgen, Astellas, Celgene, Daiichi Sankyo, Glycomimetics, ImmunoGen, Incyte, Jazz Pharmaceuticals, MacroGenics, Novartis, and Pfizer: Consultancy; Glycomimetics: Other: member of Scientific Steering Committee; Celgene: Other: chair of the Scientific Steering Committee; Covance (AbbVie): Other: chair of the Independent Review Committee. Ravandi:Orsenix: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Macrogenics: Research Funding; Xencor: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria. Topp:Amgen, KITE, Novartis, Regeneron, Roche: Consultancy; Amgen, Boehringer Ingelheim, KITE, Regeneron, Roche: Research Funding. Muth:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Kaminker:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Gojo:Amgen: Research Funding; Merck: Research Funding; Amphivena: Research Funding; Genentech: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees. Luznik:AbbVie: Consultancy; WindMil Therapeutics: Patents & Royalties: Patent holder; Merck: Research Funding, Speakers Bureau; Genentech: Research Funding. DiPersio:Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Davidson-Moncada:Macrogenics: Current Employment. Rutella:NanoString Technologies, Inc.: Research Funding; MacroGenics, Inc.: Research Funding; Kura Oncology: Research Funding.

Introduction: CRS is a potentially life-threatening toxicity observed following T cell-redirecting therapies. CRS is associated with elevated cytokines, including IL6, IFNγ, TNFα, IL2 and GM-CSF. Glucocorticosteroids (GC) and the IL6 receptor blocking antibody tocilizumab (TCZ) can reduce CRS severity; however, CRS may still occur and limit the therapeutic window of novel immunotherapeutic agents. Disruption of cytokine signaling via Janus kinase (JAK) pathway interference may represent a complementary approach to blocking CRS. Ruxolitinib (RUX), an oral JAK1/2 inhibitor approved for the treatment of myelofibrosis and polycythemia vera, interferes with signaling of several cytokines, including IFNγ and IL6, via blockade of the JAK/STAT pathway. We hypothesized that RUX may reduce the frequency and severity of CRS in R/R AML patients (pts) undergoing treatment with flotetuzumab (FLZ), an investigational CD123 x CD3 bispecific DART® molecule. Methods: Relapse/refractory (including primary induction failure, early relapse and late relapse) AML pts were included in this study. RUX pts were treated at a single site, Washington University, St. Louis, MO. RUX was dosed at 10 mg or 20mg BID days -1 through 14. Comparator (non-RUX) pts (n=23) were treated at other clinical sites. FLZ was administered at 500 ng/kg/day continuously in 28-day cycles following multi-step lead-in dosing in week 1 of cycle 1. CRS was graded per Lee criteria1. Results: As of July 1st, 2020, 10 R/R AML pts, median age 65 (range 40-82) years, have been enrolled and treated in the RUX cohort (6 at 10mg, 4 at 20 mg of RUX). All pts had non-favorable risk by ELN 2017 criteria (8 adverse and 2 intermediate); 1 (10.0%) pt had secondary AML; pt characteristics in the RUX and non-RUX cohorts were balanced, except for median baseline BM blasts which was higher in non-RUX pts: 15% (range 5-72) vs (40% (range 7-84), RUX and non-RUX pts respectively. Cytokine analysis showed statistically significant (p Conclusion: Prophylactic RUX produced a clear difference in cytokine profiles but no discernable improvement in clinical CRS or response rates in FLZ treated patients. A larger study may be required to determine the prophylactic role of RUX in CRS. References: 1. Lee DW, Gardner R, Porter DL, Louis CU, Ahmed N, Jensen M et al. Current concepts in the diagnosis and management of cytokine release syndrome. Blood 2014; 124(2): 188-195. doi: 10.1182/blood-2014-05-552729 Disclosures Uy: Pfizer: Consultancy; Agios: Consultancy; Genentech: Consultancy; Jazz Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Astellas Pharma: Honoraria. Aldoss:abbvie: Consultancy, Research Funding; kite: Consultancy; agios: Honoraria; autolus limited: Consultancy; JAZZ: Honoraria, Speakers Bureau; Amgen: Consultancy; Agios: Consultancy. Arellano:Cephalon Oncology: Research Funding; Gilead Sciences, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Hanmi: Research Funding. Foster:Daiichi Sankyo: Consultancy; Bellicum Pharmaceuticals: Research Funding; Macrogenics: Consultancy, Research Funding. Ravandi:Celgene: Consultancy, Honoraria; Xencor: Consultancy, Honoraria, Research Funding; Macrogenics: Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Orsenix: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding. Advani:Takeda: Research Funding; Glycomimetics: Consultancy, Other: Steering committee/ honoraria, Research Funding; Macrogenics: Research Funding; Abbvie: Research Funding; Immunogen: Research Funding; Seattle Genetics: Other: Advisory board/ honoraria, Research Funding; Amgen: Consultancy, Other: steering committee/ honoraria, Research Funding; Kite: Other: Advisory board/ honoraria; Pfizer: Honoraria, Research Funding; Novartis: Consultancy, Other: advisory board; OBI: Research Funding. Wieduwilt:Macrogeneics: Research Funding; Amgen: Research Funding; Leadiant: Research Funding; Merck: Research Funding; Shire: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees. Emadi:Genentech: Membership on an entity's Board of Directors or advisory committees; Amgen: Membership on an entity's Board of Directors or advisory committees; NewLink Genetics: Research Funding; Jazz Pharmaceuticals: Research Funding; KinaRx: Other: co-founder and scientific advisor; Servier: Membership on an entity's Board of Directors or advisory committees. Michaelis:Jazz Pharmaceuticals: Research Funding. Stiff:Macrogenics: Research Funding; Kite, a Gilead Company: Research Funding; Delta-Fly: Research Funding; Unum: Research Funding; Atara: Research Funding; Gamida Cell: Research Funding; Amgen: Research Funding. Wermke:MacroGenics: Honoraria. Topp:Amgen, Boehringer Ingelheim, KITE, Regeneron, Roche: Research Funding; Amgen, KITE, Novartis, Regeneron, Roche: Consultancy. Muth:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Collins:MacroGenics: Current equity holder in publicly-traded company, Other: I currently work as a contractor for MacroGenics; IQVIA: Other: I have worked as a contractor for IQVIA in the past, within the past 24 months.. Guo:Macrogenics: Current Employment. Tran:MacroGenics: Current Employment. Kaminker:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Patel:MacroGenics: Current Employment. Bakkacha:MacroGenics: Current Employment. Jacobs:MacroGenics: Current Employment. Seiler:MacroGenics: Current Employment. Rutella:MacroGenics Inc.: Research Funding; Kura Oncology: Research Funding; NanoString Technologies Inc.: Research Funding. Walter:Aptevo Therapeutics: Research Funding. Bonvini:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Davidson-Moncada:Macrogenics: Current Employment. DiPersio:Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees.

Somatic TP53 mutations and 17p deletions with genomic loss of TP53 occur in 37% to 46% of acute myeloid leukemia (AML) with adverse-risk cytogenetics and correlate with primary induction failure, high risk of relapse, and dismal prognosis. Herein, we aimed to characterize the immune landscape of TP53-mutated AML and determine whether TP53 abnormalities identify a patient subgroup that may benefit from immunotherapy with flotetuzumab, an investigational CD123 × CD3 bispecific dual-affinity retargeting antibody (DART) molecule. The NanoString PanCancer IO360 assay was used to profile 64 diagnostic bone marrow (BM) samples from patients with TP53-mutated (n = 42) and TP53-wild-type (TP53-WT) AML (n = 22) and 45 BM samples from patients who received flotetuzumab for relapsed/refractory (R/R) AML (15 cases with TP53 mutations and/or 17p deletion). The comparison between TP53-mutated and TP53-WT primary BM samples showed higher expression of IFNG, FOXP3, immune checkpoints, markers of immune senescence, and phosphatidylinositol 3-kinase-Akt and NF-κB signaling intermediates in the former cohort and allowed the discovery of a 34-gene immune classifier prognostic for survival in independent validation series. Finally, 7 out of 15 patients (47%) with R/R AML and TP53 abnormalities showed complete responses to flotetuzumab (

Background Tebotelimab, also known as MGD013, is an investigational, Fc bearing bispecific tetravalent DART molecule designed to bind PD-1 and LAG-3 and sustain/restore the function of exhausted T cells.1 Margetuximab, an investigational Fc-engineered anti-HER2 monoclonal antibody, has similar HER2 binding and antiproliferative properties to trastuzumab, but with enhanced Fc-mediated effector function. In vitro studies have demonstrated upregulation of LAG-3/PD-L1 expression on immune cells after margetuximab exposure, along with enhanced lytic activity of immune cells primed by margetuximab in the presence of tebotelimab. Methods This study characterizes safety, PK/PD, and preliminary antitumor activity of tebotelimab plus margetuximab in patients with advanced HER2+ malignancies. A one-step 3+3 dose escalation phase of tebotelimab (300 and 600 mg) combined with margetuximab 15 mg/kg, both every 3 weeks, was followed by cohort expansion of patients with breast, gastric or gastroesophageal, and other HER2+ tumors. Results At data-cutoff, 31 patients (2.0 median lines of prior therapy; 64.5% with prior HER2-directed therapy) were treated. Median duration of treatment is 10.3 weeks with 17 patients remaining on treatment. No maximum tolerated dose was defined. Treatment-related adverse events (TRAEs) occurred in 23/31 (74.2%) patients, most commonly diarrhea (n=6), nausea, ALT increased (n=5, each), AST increased, and myalgia (n=4, each). The rate of Grade 3 TRAEs was 19.4%, with no Grade 4–5 TRAEs observed. Immune-related AEs were consistent with events observed with anti-PD-1 antibodies and were manageable with supportive treatment. Among 20 response-evaluable patients (i.e., received on-treatment scan), 8 objective responses (6 confirmed) per RECIST v1.1 have been observed, including a confirmed complete response (cholangiocarcinoma) and 7 partial responses (breast [2], microsatellite stable colorectal cancer [2], esophageal adenocarcinoma [1], ovarian cancer [1], and microsatellite stable gastroesophageal junction carcinoma).1 Immunohistochemistry (IHC) of available baseline tumor specimens (n=17) demonstrated low PD-L1 expression with combined positive scores of either 0 (n=16) or 1 (n=1, colorectal cancer). Investigations into other potential correlative biomarkers, including LAG-3 and PD-1 by IHC and gene expression profiling by NanoString, remain ongoing. Conclusions Tebotelimab in combination with margetuximab has demonstrated an acceptable safety profile and encouraging early evidence of anti-tumor activity, with a preliminary overall response rate (ORR) of 40% (8/20) [including unconfirmed responses] among late-line patients with various advanced HER2+ malignancies. Trial Registration NCT03219268 Ethics Approval This study was approved by each Institution’s Ethics Board prior to enrollment of subjects. Reference Luke J, et al. A phase I, first-in-human, open-label, dose-escalation study of MGD013, a bispecific DART molecule binding PD–1 and LAG–3, in patients with unresectable or metastatic neoplasms. J Clin Oncol38: 2020 (suppl; abstr 3004).

Acute myeloid leukemia (AML) is a molecularly and clinically heterogeneous hematological malignancy. Although immunotherapy may be an attractive modality to exploit in patients with AML, the ability to predict the groups of patients and the types of cancer that will respond to immune targeting remains limited. This study dissected the complexity of the immune architecture of AML at high resolution and assessed its influence on therapeutic response. Using 442 primary bone marrow samples from three independent cohorts of children and adults with AML, we defined immune-infiltrated and immune-depleted disease classes and revealed critical differences in immune gene expression across age groups and molecular disease subtypes. Importantly, interferon (IFN)-γ-related mRNA profiles were predictive for both chemotherapy resistance and response of primary refractory/relapsed AML to flotetuzumab immunotherapy. Our compendium of microenvironmental gene and protein profiles provides insights into the immuno-biology of AML and could inform the delivery of personalized immunotherapies to IFN-γ-dominant AML subtypes.

PurposeSomatic TP53 mutations and 17p deletions with genomic loss of TP53 occur in 37-46% of acute myeloid leukemia (AML) cases with adverse risk cytogenetics and are associated with primary induction failure (PIF), high risk of relapse and dismal prognosis. Herein, we aimed to characterize the immune landscape of TP53 mutated AML and to determine whether TP53 abnormalities identify a patient subgroup that may benefit from T-cell targeting immunotherapy approaches.Experimental DesignThe NanoString Pan-Cancer IO 360™ assay was used for the immune transcriptomic analysis of 64 diagnostic bone marrow (BM) samples from adults with TP53 mutated AML (n=42) or TP53 wild type AML (n=22), and 35 BM samples from heavily pretreated patients with relapsed/refractory (R/R) AML (11 cases with TP53 mutations and/or 17p deletion with genomic loss of TP53) who received immunotherapy with flotetuzumab, an investigational CD123×CD3 bispecific DART® molecule (NCT02152956). In silico data series included The Cancer Genome Atlas (TCGA) cohort and a Dutch–Belgian Cooperative Trial Group for Hematology–Oncology (HOVON) cohort.ResultsAll TCGA cases with TP53 mutations (n=13) expressed higher levels of negative immune checkpoints, inflammatory chemokines, interferon (IFN)-γ-inducible molecules, and had a higher tumor inflammation signature (TIS) score, compared with TCGA cases with other risk-defining molecular lesions. The comparison between TP53 mutated and TP53 wild type primary BM samples showed higher expression of IFNG, FoxP3, immune checkpoints and markers of exhaustion and senescence in the former cohort and allowed the computation of a 34-gene immune classifier prognostic for overall survival. In vitro modeling experiments with AML cell lines showed heightened expression of IFN-γ and inflammation pathway genes in KG-1 cells (loss-of-function mutation of TP53) compared with Kasumi-1 cells (gain-of-function mutation of TP53). Finally, 5 out of 11 (45.5%) patients with R/R AML and TP53 abnormalities showed evidence of anti-leukemic activity of flotetuzumab immunotherapy and had higher TIS, FoxP3, CD8 T-cell abundance, inflammatory chemokine and PD1 gene expression scores at baseline compared with non-responders.ConclusionsThis study provides evidence for a correlation between IFN-γ-dominant immune subtypes and TP53 abnormalities. The anti-leukemic activity with flotetuzumab encourages further study of this immunotherapeutic approach in this patient subgroup.

Background: MGD013 is an investigational, first-in-class, Fc-bearing bispecific tetravalent DART molecule designed to bind PD-1 and LAG-3 and sustain/restore the function of exhausted T cells (1). MGD013 demonstrates in vitro ligand blocking properties and improved T-cell responses beyond that observed with anti-PD-1 and anti-LAG-3 benchmark antibodies alone or in combination. PD-1 targeted therapy with nivolumab in patients (pts) with relapsed or refractory (R/R) diffuse large B cell lymphoma (DLBCL) has yielded modest efficacy (2). LAG-3, highly expressed in DLBCL (3), has emerged as another therapeutic target of interest in this population with continued unmet need. Methods: This study characterizes the safety, tolerability, dose-limiting toxicities, maximum tolerated dose, PK/PD, and antitumor activity of MGD013 in pts with advanced solid and hematologic malignancies. R/R DLBCL pts are being treated at the recommended Phase 2 dose of 600 mg every two weeks in Cohort Expansion. Results: At data-cutoff, 17 DLBCL pts received MGD013 (2.5 median prior lines of therapy, 41.2% with prior CAR-T therapy). Treatment-related adverse events (TRAEs) occurred in 11/17 (64.7%) pts, with no same TRAE occurring in > 1 patient except pyrexia (n=3). One grade ≥ 3 TRAE occurred (pneumonia), and no events of tumor lysis syndrome were observed. Among 11 response-evaluable pts (i.e. received at least one on-treatment scan), 1 complete response (CR) and 3 partial responses (PRs) per the Lugano Classification were observed. Analyses of available pre-treatment tumor biopsy samples corresponding to responding pts demonstrated relatively high levels of LAG-3, PD-1, and PD-L1 by IHC. More comprehensive translational analyses were undertaken for the pt with CR, observed after a single MGD013 infusion in a 28-year-old male in relapse 6 months after CD19-directed CAR T-cell therapy. In contrast to a pre-CAR T biopsy specimen demonstrating no LAG-3 or PD-1 expression, IHC analysis of a lymph node specimen biopsied post-CAR T and prior to MGD013 treatment revealed high levels of both LAG-3 and PD-1 on both infiltrating T-cells and malignant B-cells. Consistent with CD19 CAR T resistance, no CD19 expression was evident. MHC class II and PD-L1 expression were observed, which when bound to LAG-3 and PD-1, respectively, form immune checkpoints that can decrease T cell function. Following MGD013 treatment, serum IFN-γ markedly increased to >140-fold above baseline. No significant changes were observed for IL-6 or IL-2. Expansion of circulating CD3+CD8+ and CD3+CD4-CD8- T-cell subsets and associated cytolytic markers (i.e., perforin, granzyme B) were observed following MGD013 treatment. The patient underwent allogeneic stem cell transplant (allo-SCT) and remains in remission 14 months post-MGD013 and 12 months post-allo-SCT. Further correlative biomarker analyses are underway in the ongoing clinical trial. Conclusion: MGD013, a novel molecule designed to coordinately block PD-1 and LAG-3, has preliminarily demonstrated an acceptable safety profile and encouraging early evidence of anti-tumor activity in R/R DLBCL pts with and without prior treatment with CAR T. Biomarker analyses confirmed expression of both PD-1 and LAG-3 axes in responding pts with evidence of pharmacodynamic responses consistent with the ability of MGD013 to enhance T-cell function. References: 1. Luke JJ, Patel MR, Hamilton E, et al. A phase I, first-in-human, open-label, dose-escalation study of MGD013, a bispecific DART molecule binding PD-1 and LAG-3, in patients with unresectable or metastatic neoplasms. J Clin Oncol 38: 2020 (suppl; abstr 3004). 2. Keane C, Law SC, Gould C, et al. LAG3: a novel immune checkpoint expressed by multiple lymphocyte subsets in diffuse large B-cell lymphoma. Blood Adv. 2020;4(7):1367-1377. doi:10.1182/bloodadvances.2019001390 3. Ansell SM, Minnema MC, Johnson P, et al., Nivolumab for Relapsed/Refractory Diffuse Large B-Cell Lymphoma in Patients Ineligible for or Having Failed Autologous Transplantation: A Single-Arm, Phase II Study. J Clin Oncol, 2019. 37(6): p. 481-489. Disclosures Wang: Verastem Oncology: Membership on an entity's Board of Directors or advisory committees; Curio Science: Honoraria; Putnam LLC: Honoraria. Asch:Astellas Pharma: Research Funding; Cartesian: Research Funding; Forty Seven: Research Funding; Juno: Research Funding; MacroGenics: Research Funding; MEI Pharma: Patents & Royalties: Provisional patent submitted (I), Research Funding. Hamad:Novartis: Honoraria; Abbvie: Honoraria. Weickhardt:Merck: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding; Ipsen: Membership on an entity's Board of Directors or advisory committees; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Ulahannan:Merck Co. Inc: Research Funding; Bayer: Membership on an entity's Board of Directors or advisory committees; G1 Therapeutics, Inc.: Research Funding; ArQule, Inc.: Research Funding; Evelo Biosciences, Inc.: Research Funding; Incyte: Membership on an entity's Board of Directors or advisory committees, Research Funding; Klus Pharma, Inc.: Research Funding; Isofol: Research Funding; GlaxoSmithKline GSK: Research Funding; Mersana Therapeutics: Research Funding; Macrogenics: Research Funding; Celgene Corporation: Research Funding; Boehringer Ingelheim: Research Funding; Array: Membership on an entity's Board of Directors or advisory committees; Ciclomed LLC: Research Funding; AbbVie, Inc.: Research Funding; AstraZeneca: Research Funding; Bristol-Myers Squibb: Research Funding; Syros: Membership on an entity's Board of Directors or advisory committees; Exelxis: Membership on an entity's Board of Directors or advisory committees. Koucheki:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Sun:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Li:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Chen:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Zhang:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Muth:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Kaminker:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Moore:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Sumrow:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company.

Introduction: Somatic TP53 mutations and deletions of 17p, to which TP53 is mapped, (TP53mut) occur in 8-10% of de novo Acute myeloid leukemia (AML) and in up to 37-46% of patients (pts) with adverse-risk cytogenetics and treatment-related myeloid neoplasms and confer a poor prognosis. In addition to its well-characterized function as a tumor suppressor, emerging evidence implicates mutant TP53 in activating genes involved in immune response and inflammation such as chemokines, cytokines and extracellular matrix modulators. An analysis of The Cancer Genome Atlas (TCGA) transcriptomic data showed that TP53 mutations, in 30 diverse cancer types, correlated with increased leukocyte infiltration into tumors with higher proportions of PD-L1-expressing CD8+ T cells and increased expression of T-cell effector genes and interferon (IFN)-γ-related genes. We recently characterized tumor microenvironmental (TME) immune gene sets that capture elements of both type I- and IFN-γ-driven biology and stratify AML into immune-infiltrated and immune-depleted subtypes. Our immune classifier predicted survival in patients receiving cytarabine-based induction and immunotherapy with flotetuzumab (FLZ), an investigational CD123×CD3 bispecific DART® molecule. We hypothesized that TP53-mutated AML represents immune-infiltrated AML that would be particularly responsive to FLZ. Methods: Fifteen TP53mut AML pts have been treated with FLZ on clinical trial CP-MGD006-01 (NCT#02152956). Disease status was assessed by modified International Working Group (IWG) criteria. Specifically, overall response rate (ORR), collectively complete response, defined as 50% decrease or decrease to 5-25% BM blasts. Microenvironmental RNAs were profiled using the PanCancer IO 360™ gene expression panel on the nCounter® platform. Baseline formalin-fixed paraffin embedded BM samples were evaluated for PD-L1, FoxP3, CD8 and CD3 expression by immunohistochemistry (IHC). Slides were stained using a Leica BondRx autostainer. Fluorescence was imaged using a Polaris Vectra 3 and analyzed using inForm software. A density-based clustering algorithm developed and run in QuPath was used to quantify T-cell 'hotspots". Results: Baseline (BL) BM samples for immune gene expression profiling were available in 13 pts with TP53mut (median age 61yrs [range 27-81]; 46.7% [7] pts female); among these, 77% (10/13) had high or intermediate immune infiltration in the TME compared with pts with 33% (10/30) TP53-WT AML (pt characteristics in the TP53-WT AML cohort were balanced) (Fig. 1A). IHC analysis confirmed high CD8+ T-cell, regulatory T cell (Treg) and PD-L1+ cell infiltration in TP53mut BL BM samples (Fig. 1B). ORR was 60% (9/15), with 47% (7/15) achieving complete response. In the TP53mut subgroup, the reduction of BM blasts relative to baseline averaged 51.2% (Fig. 1C). Time on treatment and time to death and/or censoring are summarized in Fig. 1D, including three pts who proceeded to receive allogeneic hematopoietic stem cell transplantation (HSCT). In pts who achieved a complete remission (CR, CRi), median OS was 10.3 months. Furthermore, the tumor inflammation signature (TIS), inflammatory chemokine, Treg and IFN-γ gene expression scores were significantly higher at baseline in pts with complete remission compared with non-responders (Fig. 1E), highlighting the association between response to T-cell engagers and a T cell-infiltrated TME. Conclusion: TP53 mutated AML is associated with immune infiltration in the TME and FLZ immunotherapy demonstrated activity in pts with TP53 alterations. This suggests that FLZ immunotherapy may alleviate the negative prognostic immunological impact of TP53 mutation. Figure 1 Disclosures Lai: Abbvie: Consultancy; Agios: Consultancy; Macrogenics: Consultancy; Astellas: Speakers Bureau; Jazz: Speakers Bureau. Church:NanoString Technologies, Inc.: Current Employment. Advani:Novartis: Consultancy, Other: advisory board; Abbvie: Research Funding; Pfizer: Honoraria, Research Funding; Kite: Other: Advisory board/ honoraria; Amgen: Consultancy, Other: steering committee/ honoraria, Research Funding; Seattle Genetics: Other: Advisory board/ honoraria, Research Funding; Immunogen: Research Funding; Glycomimetics: Consultancy, Other: Steering committee/ honoraria, Research Funding; Macrogenics: Research Funding; OBI: Research Funding; Takeda: Research Funding. Wieduwilt:Macrogeneics: Research Funding; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Shire: Research Funding; Merck: Research Funding; Leadiant: Research Funding; Amgen: Research Funding. Arellano:Hanmi: Research Funding; Cephalon Oncology: Research Funding; Gilead Sciences, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees. Uy:Pfizer: Consultancy; Agios: Consultancy; Genentech: Consultancy; Jazz Pharmaceuticals: Consultancy; Daiichi Sankyo: Consultancy; Astellas Pharma: Honoraria. Ravandi:Macrogenics: Research Funding; Abbvie: Consultancy, Honoraria, Research Funding; AstraZeneca: Consultancy, Honoraria; Orsenix: Consultancy, Honoraria, Research Funding; BMS: Consultancy, Honoraria, Research Funding; Amgen: Consultancy, Honoraria, Research Funding; Jazz Pharmaceuticals: Consultancy, Honoraria, Research Funding; Astellas: Consultancy, Honoraria, Research Funding; Xencor: Consultancy, Honoraria, Research Funding; Celgene: Consultancy, Honoraria. Foster:Bellicum Pharmaceuticals: Research Funding; Daiichi Sankyo: Consultancy; Macrogenics: Consultancy, Research Funding. Stiff:Atara: Research Funding; Delta-Fly: Research Funding; Kite, a Gilead Company: Research Funding; Amgen: Research Funding; Unum: Research Funding; Gamida Cell: Research Funding; Macrogenics: Research Funding. Emadi:NewLink Genetics: Research Funding; Amgen: Membership on an entity's Board of Directors or advisory committees; Genentech: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; KinaRx: Other: co-founder and scientific advisor; Jazz Pharmaceuticals: Research Funding. Walter:Aptevo Therapeutics: Research Funding. Tran:MacroGenics: Current Employment. Kaminker:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Muth:MacroGenics, Inc.: Current Employment, Current equity holder in publicly-traded company. Guo:Macrogenics: Current Employment. Gojo:Genentech: Research Funding; BMS: Membership on an entity's Board of Directors or advisory committees; Amphivena: Research Funding; Amgen: Research Funding; Merck: Research Funding. DiPersio:Magenta Therapeutics: Membership on an entity's Board of Directors or advisory committees. Davidson-Moncada:Macrogenics: Current Employment. Rutella:MacroGenics, Inc.: Research Funding; NanoString Technologies, Inc.: Research Funding; Kura Oncology: Research Funding.

Approximately 50% of acute myeloid leukemia (AML) patients do not respond to induction therapy (primary induction failure [PIF]) or relapse after

This study dissected the complexity of the immune architecture of acute myeloid leukemia (AML) at high resolution and assessed its influence on therapeutic response. Using 387 primary bone marrow samples from three discovery cohorts of children and adults with AML, we defined immune-infiltrated and immune-depleted disease subtypes and unraveled critical differences in immune gene expression across age groups and disease stages. Importantly, interferon (IFN)-γ-related mRNA profiles were predictive for both chemotherapy resistance and response of primary refractory/relapsed AML to flotetuzumab immunotherapy. Our compendium of microenvironmental gene and protein profiles sheds novel insights into the immuno-biology of AML and will inform the delivery of personalized immunotherapies to IFN-γ-dominant AML subtypes.

Background Despite improvements in treatments, the 5-year survival of GEA patients (pts) is disappointing. Individual molecular subtypes display preferential responses to PD-1 blockade. M, an investigational Fc-optimized anti-HER2 monoclonal antibody, is being tested in combination with P in HER2+ GEA post trastuzumab. We present gene expression data from archival FFPE biopsies. Methods 55 pt samples were assessed by NanoString PanCancer IO360™ assay. Immune signature scores are presented as fold changes (FC) and analyzed by unpaired t-test. Associations examined include baseline IHC PD-L1 (pos vs neg) and HER2 expression (IHC3+ vs 2+), ERBB2 mRNA, inflamed tumor microenvironment (TME), radiographic response, and GC vs GEJ. Results ERBB2 mRNA was increased in pts with HER2 IHC3+ vs 2 + (5.6 FC, p Conclusions Our study documents for the first time ERBB2 expression and inflamed TME in GEA, which can help differentiate immunologically between GC and GEJ tumors. Clinical trial identification NCT02689284. Legal entity responsible for the study MacroGenics, Inc. Funding MacroGenics, Inc. Disclosure S. Rutella: Leadership role: Society for Immunotherapy of Cancer; Research grant / Funding (institution): John and Lucille van Geest Foundation. S.E. Church: Shareholder / Stockholder / Stock options, Full / Part-time employment: NanoString Technologies. A.H. Sullivan: Shareholder / Stockholder / Stock options, Full / Part-time employment: NanoString Technologies. S. Warren: Shareholder / Stockholder / Stock options, Full / Part-time employment: NanoString Technologies. J. Baughman: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. J. Muth: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. H. Park: Research grant / Funding (institution): Amgen; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): BeiGene; Research grant / Funding (institution): Bristol-Myers Squibb; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): EMD Serono; Research grant / Funding (institution): Gilead Sciences; Research grant / Funding (institution): Incyte; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): Macrogenics; Research grant / Funding (institution): MedImmune; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Merck; Research grant / Funding (institution): Millennium; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Puma Biotechnology; Research grant / Funding (institution): Regeneron; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Taiho Pharmaceutical; Research grant / Funding (institution): Vertex. H. Uronis: Shareholder / Stockholder / Stock options, Full / Part-time employment: GeneCentric; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Bristol-Myers Squibb; Research grant / Funding (institution): Advaxis; Research grant / Funding (institution): Genentech/Roche; Research grant / Funding (institution): Lycera; Research grant / Funding (institution): Macrogenics. Y. Kang: Advisory / Consultancy: Bristol-Myers Squibb; Advisory / Consultancy, Research grant / Funding (self): DAE HWA Pharmaceutical; Advisory / Consultancy: Lilly/ImClone; Advisory / Consultancy: Merck Serono; Advisory / Consultancy: Ono Pharmaceutical; Advisory / Consultancy: Roche/Genentech; Advisory / Consultancy: Taiho Pharmaceutical; Research grant / Funding (self): LSK Biopharma. M.C.H. Ng: Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: MSD Oncology; Honoraria (self), Travel / Accommodation / Expenses: Taiho Pharmaceutical; Advisory / Consultancy: Bristol-Myers Squibb; Research grant / Funding (institution): ASLAN Pharmaceuticals. P. Enzinger: Advisory / Consultancy: Astellas Pharma; Advisory / Consultancy: Five Prime Therapeutics; Advisory / Consultancy: Merck; Advisory / Consultancy: Taiho Pharmaceutical. K.W. Lee: Research grant / Funding (institution): Array BioPharma; Research grant / Funding (institution): ASLAN Pharmaceuticals; Research grant / Funding (institution): AstraZeneca/MedImmune; Research grant / Funding (institution): Five Prime Therapeutics; Research grant / Funding (institution): Green Cross Corp; Research grant / Funding (institution): LSK BioPharma; Research grant / Funding (institution): Macrogenics; Research grant / Funding (institution): Merck KGaA; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Pharmacyclics. K. Huber: Full / Part-time employment: Macrogenics, Inc. A. Wynter-Horton: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. D. Li: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. Y. Bang: Advisory / Consultancy, Research grant / Funding (institution): AstraZeneca/MedImmune; Advisory / Consultancy, Research grant / Funding (institution): Bayer; Advisory / Consultancy, Research grant / Funding (institution): BeiGene; Advisory / Consultancy, Research grant / Funding (institution): Green Cross; Advisory / Consultancy: Hanmi; Advisory / Consultancy, Research grant / Funding (institution): Merck Serono; Advisory / Consultancy, Research grant / Funding (institution): MSD Oncology; Advisory / Consultancy, Research grant / Funding (institution): Novartis; Advisory / Consultancy: Samyang; Advisory / Consultancy, Research grant / Funding (institution): Taiho Pharmaceutical; Research grant / Funding (institution): Astellas Pharma; Research grant / Funding (institution): Boehringer Ingelheim; Research grant / Funding (institution): Boston Biomedical; Research grant / Funding (institution): Bristol-Myers Squibb; Research grant / Funding (institution): CKD; Research grant / Funding (institution): Curis; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): Five Prime Therapeutics; Research grant / Funding (institution): Genentech/Roche; Research grant / Funding (institution): GlaxoSmithKline; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): Macrogenics; Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Takeda. J. Davidson-Moncada: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. D.V. Catenacci: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Bristol-Myers Squibb; Honoraria (self): Five Prime Therapeutics; Honoraria (self), Speaker Bureau / Expert testimony: Foundation Medicine; Honoraria (self), Advisory / Consultancy: Genentech/Roche; Honoraria (self): Genmab; Honoraria (self): Gritstone Oncology; Honoraria (self), Speaker Bureau / Expert testimony: Guardant Health; Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self), Advisory / Consultancy: Merck; Honoraria (self): NantOmics; Honoraria (self): OncoPlex Diagnostics; Honoraria (self), Advisory / Consultancy: Taiho Pharmaceuticsal; Advisory / Consultancy: Astellas Pharma. All other authors have declared no conflicts of interest.

Approximately 40% of patients (pts) with newly diagnosed (AML) either fail to achieve complete remission with intensive induction therapy or experience disease recurrence after a short remission duration (< 6 months). These pts, herein considered to have primary refractory disease, are an extremely challenging population to treat, with only 14% achieving remission following conventional chemotherapy and with subsequent salvage attempts being nearly universally ineffective (1). Increased immune infiltration of the tumor microenvironment (TME) and high CD123 expression on AML blasts have been associated with primary induction failure and poor prognosis (2, 3). Flotetuzumab (FLZ), a CD123 x CD3 bispecific DART molecule, is currently being tested in a phase 1/2 study in pts with either relapsed or refractory (R/R) AML. We have previously reported FLZ activity in primary refractory AML (4); herein, we provide additional scientific rationale supporting the investigation of FLZ in this patient population. The recommended Phase 2 dose (RP2D) of FLZ identified in an ongoing Phase 1/2 study is 500 ng/kg/day administered as a 7 -day/week continuous infusion. Pts receive a lead-in dose during week (W) 1, followed by 500 ng/kg/day during W2-4 of Cycle 1, and a 4-day on/3-day off schedule for Cycle 2 and beyond. Disease status was assessed by modified IWG criteria; bone marrow (BM) samples were collected to investigate biomarkers, including CD123 receptor density (RD), and gene expression profiling using the NanoString PanCancer IO 360™ panel, which measures the expression of 770 genes, including 14 immune cell types and 32 immuno-oncology biological signatures. Gene expression comparisons are presented at fold change (FC) and a t-test was used for statistical analysis. Fifty pts with R/R AML received FLZ at the RP2D. Thirty (60%) pts had primary refractory AML: 24 failed ≥2 induction attempts and 6 recurred after remission of 30% decrease in BM blasts) was associated with increased baseline immune gene signatures, including significantly higher IFNγ scores (1.8 FC, p=0.0212; AUROC=0.74), and an increased tumor inflammation signature (TIS) score (1.658 FC, p=0.00827, AUROC=0.847 compared to non-responders. FLZ was well tolerated, with no increased cytokine release syndrome events in primary refractory pts (30% G1, 67% G2, 3% G3) compared to relapse pts (26% G1, 58% G2, 16% G3), notwithstanding the increased CD123 RD in the former. In conclusion, we show that FLZ elicits clinical response in heavily treated patients with poor response rates to primary therapy. We also show that increased IFNγ signaling gene expression scores in baseline BM appears to associate with response to FLZ therapy. Enrollment has been expanded to further define FLZ's activity specifically in pts with primary refractory AML, and candidate biomarkers to enable identification of pts more likely to respond to FLZ. Estey E, et al. Blood (1996), 88 (2) 756Vadakekolathu J, et al. Blood (2017) 130:3942Vergez F, et al. Haematologica (2011), 96(12):1792-8Uy GL, et al. Blood (2018) 132:764Duong V, et al. Leukemia (2013),13(6):711-5 Disclosures Uy: Astellas: Consultancy; Pfizer: Consultancy; Curis: Consultancy; GlycoMimetics: Consultancy. Aldoss:Agios: Consultancy, Honoraria; AUTO1: Consultancy; Jazz Pharmaceuticals: Honoraria, Other: travel/accommodation/expenses, Speakers Bureau; Helocyte: Consultancy, Honoraria, Other: travel/accommodation/expenses. Foster:Bellicum Pharmaceuticals, Inc: Research Funding; Daiichi Sankyo: Consultancy; MacroGenics: Research Funding; Celgene: Research Funding. Sallman:Celgene: Research Funding, Speakers Bureau; Celyad: Membership on an entity's Board of Directors or advisory committees; Incyte: Speakers Bureau; Jazz: Research Funding; Novartis: Speakers Bureau; Abbvie: Speakers Bureau. Sweet:Abbvie: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Celgene: Speakers Bureau; Stemline: Consultancy; Pfizer: Consultancy; Jazz: Speakers Bureau; Incyte: Research Funding. Rizzieri:AbbVie, Agios, AROG, Bayer, Celgene, Gilead, Jazz, Novartis, Pfizer, Sanofi, Seattle Genetics, Stemline, Teva: Other: Advisory Board; AROG, Bayer, Celgene, Celltron, Mustang, Pfizer, Seattle Genetics, Stemline: Consultancy; Celgene, Gilead, Seattle Genetics, Stemline: Other: Speaker; Stemline: Research Funding. Advani:Amgen: Research Funding; Macrogenics: Research Funding; Abbvie: Research Funding; Pfizer: Honoraria, Research Funding; Glycomimetics: Consultancy, Research Funding; Kite Pharmaceuticals: Consultancy. Emadi:Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; NewLink Genetics: Research Funding; Genentech: Consultancy, Honoraria; KinaRx: Membership on an entity's Board of Directors or advisory committees, Other: Co-Founder and Scientific Advisor, Patents & Royalties; Jazz Pharmaceuticals: Research Funding. Wieduwilt:Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen, Leadiant, Merck, Servier: Research Funding; Reata Pharmaceuticals: Equity Ownership. Vey:Novartis: Consultancy, Honoraria; Janssen: Honoraria. Church:NanoString Technologies, Inc.: Employment, Equity Ownership. Rettig:WashU: Patents & Royalties: Patent Application 16/401,950. Arellano:Gilead: Consultancy. Löwenberg:Up-to-Date", section editor leukemia: Membership on an entity's Board of Directors or advisory committees; Frame Pharmaceuticals: Equity Ownership; Elected member, Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Editorial Board "European Oncology & Haematology": Membership on an entity's Board of Directors or advisory committees; Clear Creek Bio Ltd: Consultancy, Honoraria; Abbvie: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Astex: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; CELYAD: Membership on an entity's Board of Directors or advisory committees; Chairman Scientific Committee and Member Executive Committee, European School of Hematology (ESH, Paris, France): Membership on an entity's Board of Directors or advisory committees; Chairman, Leukemia Cooperative Trial Group HOVON (Netherlands: Membership on an entity's Board of Directors or advisory committees; Supervisory Board, National Comprehensive Cancer Center (IKNL), Netherland: Membership on an entity's Board of Directors or advisory committees; Hoffman-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees; Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees. Ravandi:Selvita: Research Funding; Xencor: Consultancy, Research Funding; Menarini Ricerche: Research Funding; Macrogenix: Consultancy, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Cyclacel LTD: Research Funding. Muth:MacroGenics, Inc.: Employment, Equity Ownership. Tran:MacroGenics: Employment. Timmeny:MacroGenics, Inc.: Employment, Other: Stock Ownership. Topp:Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Regeneron Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Guo:Macrogenics: Employment. Zhao:MacroGenics, Inc.: Employment. Wigginton:MacroGenics, Inc.: Employment, Equity Ownership; Western Oncolytics: Other: clinical advisory board. Bonvini:MacroGenics, Inc.: Employment, Equity Ownership. Rutella:NanoString Technologies, Inc.: Research Funding; MacroGenics, Inc.: Research Funding. Walter:Seattle Genetics: Research Funding; Race Oncology: Consultancy; Pfizer: Consultancy, Research Funding; New Link Genetics: Consultancy; Kite Pharma: Consultancy; Agios: Consultancy; Amgen: Consultancy; Amphivena Therapeutics: Consultancy, Equity Ownership; Aptevo Therapeutics: Consultancy, Research Funding; Argenx BVBA: Consultancy; Astellas: Consultancy; BioLineRx: Consultancy; BiVictriX: Consultancy; Boehringer Ingelheim: Consultancy; Boston Biomedical: Consultancy; Covagen: Consultancy; Daiichi Sankyo: Consultancy; Jazz Pharmaceuticals: Consultancy. Davidson-Moncada:MacroGenics, Inc.: Employment, Equity Ownership. DiPersio:Amphivena Therapeutics: Consultancy, Research Funding; RiverVest Venture Partners Arch Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cellworks Group, Inc.: Membership on an entity's Board of Directors or advisory committees; NeoImmune Tech: Research Funding; Macrogenics: Research Funding, Speakers Bureau; Magenta Therapeutics: Equity Ownership; WUGEN: Equity Ownership, Patents & Royalties, Research Funding; Celgene: Consultancy; Incyte: Consultancy, Research Funding; Bioline Rx: Research Funding, Speakers Bureau; Karyopharm Therapeutics: Consultancy.

Introduction The infiltration of immune cells into tumors has been associated with therapeutic effects in preclinical models and patients with cancer. In AML, we have previously reported that immune infiltrated TME is predictive of failure to cytotoxic chemotherapy, but associated with response to immunotherapy, specifically FLZ (Uy ASH 2018, Rutella ASH 2018). Furthermore, FLZ also affects immune infiltration in the TME (Rutella ASH 2018). NK cells play an important role in AML control (Ruggieri Science 2012). FLZ (MGD006/S80880) is a humanized DART® molecule that bridges CD123 on AML with CD3 on T cells and mediates anticancer activity via T-cell activation and cytolytic activity against the bound cancer cell. While this is well described in vitro, little evidence of this interaction is available in vivo. Methods Patients (pts) were treated on the recommended phase 2 dose (RP2D) of FLZ (multi-step lead-in dose followed by 500ng/kg/day, in 28-day cycles). We studied the bone marrow (BM) tissue samples for 6 primary refractory pts at baseline and after treatment. Response assessment was performed at day 25±3 days of each cycle. Serial BM samples were evaluated using 2 different staining panels (PD-L1, FoxP3, CD8, CD3, CD103 / CD123, CD3, CD57, CD16) on consecutive slides. Slides were stained using a Leica BondRx autostainer and fluorescence imaged using a Polaris Vectra 3 and analyzed using inForm software. A density-based clustering algorithm developed and run in QuPath was used to quantify CD3+ T cell clusters. Results Six pts with primary refractory AML were included in this report. Pts were heavily pretreated (median prior lines of therapy was 3, range 2-9), and had adverse cytogenetic risk (ELN 2017). Three pts had a complete remission (CR) after 1 cycle of therapy (CR, CRh, CRi), two went on the receive allogeneic stem cell transplant (HSCT). In baseline BM samples, CD3 and CD8 cell infiltrates were higher in CR vs non-responders (CD3+ 18.3% ±6.9 vs 9.3% ±1.8; CD8+ 9.4% ±3.5 vs 4.8% ±1.2; mean±SEM). Two of the three CR patients, who underwent HSCT, developed clusters (Figure 1) in their on-treatment biopsies with 65 and 22 clusters of an average of 34 and 17 T cells per cluster, respectively. All clusters in CR pts were found on or adjacent to CD123+ cells. The BM biopsy of the CR pt with no detected clusters had no unequivocal evidence of residual/recurrent leukemic blasts. This pt had their dose interrupted early due to non-treatment related AE (infectious complication) and did not receive a full cycle of treatment; the response was transient and the pt relapsed shortly thereafter. NK cells (CD57+CD16+) were increased in post treatment biopsies of CR vs non-responders (0.93 ±0.31 vs 0.27 ±0.13; mean±SEM) with the largest fold increase in CR (28 vs 9). Lastly, post treatment biopsy PD-L1 expression was higher in non-responders than CR (23% vs 16%) with non-responders exhibiting the largest fold change in total PD-L1+ cells (10.9 vs 2.2). Summary Consistent with its proposed mechanism of action, these data highlight for the first time, the dynamic induction of an increase in T-cell infiltration, and clustering around CD123 AML cells in the bone marrow microenvironment of two AML patients that responded to FLZ. In pts with resistance to FLZ (non-responders) PD-L1 induction was significantly higher indicating that in some pts treatment with sequential check point inhibitor could obviate this mechanism of resistance A trial combining FLZ with sequential administration of a PD-1 inhibitor (MGA012) is currently recruiting pts. Figure 1. Baseline and on-treatment IHC of BM biopsies of a FLZ-treated CR pt showing cluster formation following treatment. Disclosures Bifulco: Ventana: Other: advisory board; PrimeVax: Equity Ownership, Other: ScientificBoard; BMS: Other: Advisory Board; Providnece: Patents & Royalties: Imaging processing; Halio Dx: Other: advisory board. Wigginton:macrogenics: Employment, Equity Ownership; western oncolytics: Consultancy, Other: consultancy. Muth:MacroGenics, Inc.: Employment, Equity Ownership. Davidson-Moncada:MacroGenics, Inc.: Employment, Equity Ownership. Fox:Akoya: Research Funding; Bristol Myers Squibb: Research Funding; Definiens: Membership on an entity's Board of Directors or advisory committees; Macrogenics: Research Funding; Ultivue: Membership on an entity's Board of Directors or advisory committees.

Background: Cytokine release syndrome (CRS) management in acute myeloid leukemia (AML) patients treated with flotetuzumab, an investigational CD123xCD3 bispecific DART® molecule for T cell redirected therapy. CRS is a hallmark of T cell activating therapy and can be correlated with efficacy, specifically, with CAR-T cells(1). Identification of patients at risk for high grade CRS will help guide CRS management. Flotetuzumab (MGD006) is anovel CD123xCD3 bispecific DART® molecule in Phase 1/2 testing in patients with relapsed/ refractory AML. Several strategies have been successfully employed to mitigate CRS severity, some have been previously reported (2, 3). Here we report on further refinement of CRS management and subsequent investigation of potentiel predictive biomarkers of severity. Methods: The recommended phase 2 dose (RP2D) of flotetuzumab is 500ng/kg/d CIV. Week 1 comprises a step-wise lead-in dose (LID) (1-step: 100 ng/kg/day days 1-4; 2-step: 30ng/kg/d for 3days, 100ng/kg/d for 4days, or multi-step (MS) LID at 30, 60, 100, 200, 300, 400 and 500 ng/kg/day each for 24 hours) in order to improve flotetuzumab tolerability. Tocilizumab usage recommended early in CRS management. The relationships between immune cells (T-cell subsets, monocytes) and tumor burden (percent CD123+ AML blasts, CD123 expression) were further interrogated as potential determinants of CRS. Results: 50 patients have been treated at the RP2D. While almost all patients experienced IRR/CRS events, the majority of these patients experienced IRR/CRS that were mild-moderate in severity (28% Grade(G)1, 62% G2, and 8% G3), of short duration (median 1 day for G1, 2 days G2, 2.5 days G3), and resolved completely with no clinical sequalae reported. Most CRS events occured in the first week of treatment (38.3%) and gradually decreased with continuous dosing (24.8%, 7.4%, and 4.3% during weeks 2-4, respectively). Several key interventions have helped mitigate CRS severity. Sequential increment in steps of LID schedules (1 step, 2-step or multi-step LID) have successfully decreased CRS severity and incidence. For example, CRS mean grade±SEM for week 1 was 2.0±0.26 vs 1.4±0.72 vs 1.5±0.63 and for week 4, 0.67±0.42 vs 0.2 ±0.50 vs 0.1 ±0.50 (1 step, 2-step or multi-step LID, respectively). Moreover, LID improved overall tolerability. Introduction of early use of tocilizumab has helped forestall CRS development; 27 patients received tocilizumab (10 doses for G1, 27 for G2, and 2 for G3 events), only 5 pts have required steroids (4 for G2 and 1 for G3), and no pts have required vasopressor support. Blunting of CRS events did not impact antileukemic activity. CRS severity showed a relationship with baseline frequency of circulating CD4+ cells (mean 0.2 K/µL in patients with no CRS vs. 1.0 K/µL in G1 vs 1.6 K/µL in G ≥2, p < 0.000.1), and peak CRS grade in week 1. Conclusion: Like other T-cell activating therapies, flotetuzumab is associated with CRS. Several mitigating factors have helped to blunt the severity of CRS, including lead-in dosing and early tocilizumab usage. Circulating CD4+ cells at baseline continues to be associated with CRS risk, and may be a helpful marker to identify patients at increased risk for CRS. 1. Maude, SL. et al. Managing Cytokine Release Syndrome Associated With Novel T Cell-Engaging Therapies. Cancer J. 2014; 20(2): 119-122. 2. Jacobs, K, et al.Lead-in Dose Optimization to Mitigate Cytokine Release Syndrome in AML and MDS Patients Treated with Flotetuzumab, a CD123 x CD3 Dart® Molecule for T-Cell Redirected Therapy. Blood 2017 130:3856. 3. Jacobs, K, et al.Management of Cytokine Release Syndrome in AML Patients Treated with Flotetuzumab, a CD123 x CD3 Bispecific Dart® Molecule for T-Cell Redirected Therapy. Blood 2018 132:2738. Disclosures Bakkacha: Macrogenics,Inc: Employment, Equity Ownership. Uy:Astellas: Consultancy; Pfizer: Consultancy; Curis: Consultancy; GlycoMimetics: Consultancy. Aldoss:Helocyte: Consultancy, Honoraria, Other: travel/accommodation/expenses; AUTO1: Consultancy; Jazz Pharmaceuticals: Honoraria, Other: travel/accommodation/expenses, Speakers Bureau; Agios: Consultancy, Honoraria. Foster:Bellicum Pharmaceuticals, Inc: Research Funding; Daiichi Sankyo: Consultancy; MacroGenics: Research Funding; Celgene: Research Funding. Sallman:Celyad: Membership on an entity's Board of Directors or advisory committees. Sweet:Pfizer: Consultancy; Incyte: Research Funding; Agios: Membership on an entity's Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees; Celgene: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Stemline: Consultancy; Jazz: Speakers Bureau; Abbvie: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees. Rizzieri:Celgene, Gilead, Seattle Genetics, Stemline: Other: Speaker; AbbVie, Agios, AROG, Bayer, Celgene, Gilead, Jazz, Novartis, Pfizer, Sanofi, Seattle Genetics, Stemline, Teva: Other: Advisory Board; AROG, Bayer, Celgene, Celltron, Mustang, Pfizer, Seattle Genetics, Stemline: Consultancy; Stemline: Research Funding. Advani:Glycomimetics: Consultancy, Research Funding; Kite Pharmaceuticals: Consultancy; Amgen: Research Funding; Pfizer: Honoraria, Research Funding; Macrogenics: Research Funding; Abbvie: Research Funding. Emadi:Genentech: Consultancy, Honoraria; KinaRx: Membership on an entity's Board of Directors or advisory committees, Other: Co-Founder and Scientific Advisor, Patents & Royalties; NewLink Genetics: Research Funding; Jazz Pharmaceuticals: Research Funding; Amgen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees. Wieduwilt:Reata Pharmaceuticals: Equity Ownership; Daiichi Sankyo: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Amgen, Leadiant, Merck, Servier: Research Funding. Vey:Novartis: Consultancy, Honoraria; Janssen: Honoraria. Arellano:Gilead: Consultancy. Löwenberg:Up-to-Date", section editor leukemia: Membership on an entity's Board of Directors or advisory committees; Abbvie: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Astex: Membership on an entity's Board of Directors or advisory committees; Chairman, Leukemia Cooperative Trial Group HOVON (Netherlands: Membership on an entity's Board of Directors or advisory committees; Clear Creek Bio Ltd: Consultancy, Honoraria; Editorial Board "European Oncology & Haematology": Membership on an entity's Board of Directors or advisory committees; Elected member, Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Frame Pharmaceuticals: Equity Ownership; Hoffman-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees; Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Supervisory Board, National Comprehensive Cancer Center (IKNL), Netherland: Membership on an entity's Board of Directors or advisory committees; Chairman Scientific Committee and Member Executive Committee, European School of Hematology (ESH, Paris, France): Membership on an entity's Board of Directors or advisory committees; CELYAD: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees. Ravandi:Cyclacel LTD: Research Funding; Menarini Ricerche: Research Funding; Selvita: Research Funding; Xencor: Consultancy, Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Macrogenix: Consultancy, Research Funding. Tran:MacroGenics: Employment. Muth:MacroGenics, Inc.: Employment, Equity Ownership. Baughman:MacroGenics, Inc.: Employment, Equity Ownership. Timmeny:MacroGenics, Inc.: Employment, Other: Stock Ownership. Topp:Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Membership on an entity's Board of Directors or advisory committees; Roche: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Regeneron Pharmaceuticals, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer Ingelheim: Membership on an entity's Board of Directors or advisory committees, Research Funding; KITE: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Guo:Macrogenics: Employment. Zhao:MacroGenics, Inc.: Employment. Wigginton:macrogenics: Employment, Equity Ownership; western oncolytics: Consultancy, Other: consultancy. Bonvini:MacroGenics, Inc.: Employment, Equity Ownership. Walter:Daiichi Sankyo: Consultancy; Amgen: Consultancy; Agios: Consultancy; Boston Biomedical: Consultancy; Covagen: Consultancy; Amphivena Therapeutics: Consultancy, Equity Ownership; Aptevo Therapeutics: Consultancy, Research Funding; Argenx BVBA: Consultancy; Astellas: Consultancy; BioLineRx: Consultancy; BiVictriX: Consultancy; Boehringer Ingelheim: Consultancy; Pfizer: Consultancy, Research Funding; Race Oncology: Consultancy; Seattle Genetics: Research Funding; Jazz Pharmaceuticals: Consultancy; Kite Pharma: Consultancy; New Link Genetics: Consultancy. Davidson:Macrogenics,Inc: Employment, Equity Ownership. DiPersio:Incyte: Consultancy, Research Funding; Celgene: Consultancy; Karyopharm Therapeutics: Consultancy; Bioline Rx: Research Funding, Speakers Bureau; RiverVest Venture Partners Arch Oncology: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cellworks Group, Inc.: Membership on an entity's Board of Directors or advisory committees; Magenta Therapeutics: Equity Ownership; WUGEN: Equity Ownership, Patents & Royalties, Research Funding; Amphivena Therapeutics: Consultancy, Research Funding; NeoImmune Tech: Research Funding; Macrogenics: Research Funding, Speakers Bureau. Jacobs:Macrogenics,Inc: Employment, Equity Ownership.

Background T + chemo is standard 1st line therapy for HER2+ gastroesophageal adenocarcinoma; however, patients (pts) tend to progress in 6-8 months. Up to 40% show loss of HER2 expression post T, likely underlying the lack of efficacy of anti-HER2 agents in 2nd line therapy. We report here a clinical update and biomarker analysis of an ongoing study in pts receiving M, an anti-HER2 Fc-optimized mAb, plus P in HER2+ GEA pts in post T, 2nd line, chemotherapy-free treatment. Methods Endpoints described herein are safety, objective response rate (ORR), disease control rate (DCR), archival HER2 IHC level and/or ERBB2 amplification (amp) status pre-M+P in cell free DNA (cfDNA) by NGS (Guardant360), PD-L1 CPS by IHC (22C3 pharmDx), anti-HER2 T- cell immunity by ELISPOT on PBMCs, and NanoString PanCancer IO360™ assay on archival FFPE biopsies. Results 92 pts (66% GC, 34% GEJ) received 15mg/kg M+200mg P Q3W. 99% were MSS and 43% were PD-L1+(>1%). Related adverse events ≥grade 3 were 18.5%. Confirmed ORR was 19% with 54% DCR; interestingly, higher response rates occurred in GC vs GEJ (25% vs 7% ORR, p=0.047 and 64% vs 33% DCR, p=0.008). A higher proportion of GC vs GEJ cancers was HER2 3+ on archival IHC (90% vs 53%, p=0.0075), furthermore, a 5.3-fold greater fraction of GC vs GEJ pts showed upregulated tumor ERBB2 RNA expression (p 6-fold higher in GC vs GEJ (34.7% vs 5.5%, p=0.03) and associated with 53% confirmed ORR and 82% DCR in GC. GC pts with higher baseline T-cell immunity toward HER2 (p59 class II peptide) had greater probability of ORR (p=0.005). Conclusions In this study, M+P demonstrated tolerability and preliminary evidence of anti-tumor activity as a chemotherapy-free regimen in 2nd line HER2+ GC; biomarker analysis suggests an association with higher expression and retention of HER2 and PD-L1 together with pre-existing anti-HER2 immunity. Clinical trial identification NCT02689284. Legal entity responsible for the study MacroGenics, Inc. Funding MacroGenics, Inc. Disclosure H. Park: Research grant / Funding (institution): Ambrx; Research grant / Funding (institution): Amgen; Research grant / Funding (institution): Array BioPharma; Research grant / Funding (institution): AstraZeneca; Research grant / Funding (institution): Bayer; Research grant / Funding (institution): BeiGene; Research grant / Funding (institution): Bristol-Myers Squibb; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): EMD Serono; Research grant / Funding (institution): Gilead Sciences; Research grant / Funding (institution): GlaxoSmithKline; Research grant / Funding (institution): Incyte; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): MacroGenics; Research grant / Funding (institution): MedImmune; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Merck; Research grant / Funding (institution): Millennium; Research grant / Funding (institution): Novartis; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Puma Biotechnology; Research grant / Funding (institution): Regeneron; Research grant / Funding (institution): Roche; Research grant / Funding (institution): Taiho Pharmaceutical; Research grant / Funding (institution): Vertex. H. Uronis: Shareholder / Stockholder / Stock options, Full / Part-time employment: GeneCentric; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Bristol-Myers Squibb; Research grant / Funding (institution): Advaxis; Research grant / Funding (institution): Genentech/Roche; Research grant / Funding (institution): Lycera; Research grant / Funding (institution): MacroGenics; Research grant / Funding (institution): Merck. Y. Kang: Advisory / Consultancy: Bristol-Myers Squibb; Advisory / Consultancy, Research grant / Funding (institution): DAE HWA Pharmaceutical; Advisory / Consultancy: Lilly/Imclone; Advisory / Consultancy: Merck/Serano; Advisory / Consultancy: Ono Pharmaceutical; Advisory / Consultancy: Roche/Genentech; Research grant / Funding (institution): Taiho Pharmaceutical; Research grant / Funding (institution): LSK Biopharma. M.C.H. Ng: Honoraria (self), Advisory / Consultancy, Travel / Accommodation / Expenses: MSD Oncology; Honoraria (self), Travel / Accommodation / Expenses: Taiho Pharmaceutical; Advisory / Consultancy: Bristol-Myers Squibb; Research grant / Funding (institution): ASLAN Pharmaceuticals. P. Enzinger: Advisory / Consultancy: Astellas Pharma; Advisory / Consultancy: Five Prime Therapeutics; Advisory / Consultancy: Merck; Advisory / Consultancy: Taiho Pharmaceutical. K.W. Lee: Research grant / Funding (institution): Array BioPharma; Research grant / Funding (institution): ASLAN Pharmaceuticals; Research grant / Funding (institution): AstraZeneca/MedImmune; Research grant / Funding (institution): Five Prime Therapeutics; Research grant / Funding (institution): Green Cross Corp; Research grant / Funding (institution): LSK BioPharma; Research grant / Funding (institution): MacroGenics; Research grant / Funding (institution): Merck KGaA; Research grant / Funding (institution): MSD; Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Pharmacyclics; Honoraria (self): Bristol-Myers Squibb; Honoraria (self): Lilly; Research grant / Funding (institution): ALX Oncology. S. Rutella: Leadership role: Clinical & Biomarkers Data Sharing Subcommittee, Society for Immunotherapy of Cancer; Research grant / Funding (institution): John and Lucille van Geest Foundation. S.E. Church: Shareholder / Stockholder / Stock options, Full / Part-time employment: NanoString Technologies. J. Nordstrom: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. T. Wu: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. J. Yen: Shareholder / Stockholder / Stock options, Full / Part-time employment: Guardant Health. A. Franovic: Shareholder / Stockholder / Stock options, Full / Part-time employment: Guardant Health. J. Muth: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. M. Rosales: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. J. Davidson-Moncada: Shareholder / Stockholder / Stock options, Full / Part-time employment: MacroGenics, Inc. Y. Bang: Advisory / Consultancy, Research grant / Funding (institution): AstraZeneca/MedImmune; Advisory / Consultancy, Research grant / Funding (institution): Bayer; Advisory / Consultancy, Research grant / Funding (institution): Beigene; Advisory / Consultancy, Research grant / Funding (institution): Green Cross; Advisory / Consultancy: Hanmi; Advisory / Consultancy, Research grant / Funding (institution): Merck Serono; Advisory / Consultancy, Research grant / Funding (institution): MSD Oncology; Advisory / Consultancy, Research grant / Funding (institution): Novartis; Advisory / Consultancy: Samyang; Advisory / Consultancy, Research grant / Funding (institution): Taiho Pharmaceutical; Research grant / Funding (institution): Astellas Pharma; Research grant / Funding (institution): Boehringer Ingelheim; Research grant / Funding (institution): Boston Biomedical; Research grant / Funding (institution): Bristol-Myers Squibb; Research grant / Funding (institution): CKD; Research grant / Funding (institution): Curis; Research grant / Funding (institution): Daiichi Sankyo; Research grant / Funding (institution): Five Prime Therapeutics; Research grant / Funding (institution): Genentech/Roche; Research grant / Funding (institution): GlaxoSmithKline; Research grant / Funding (institution): Lilly; Research grant / Funding (institution): MacroGenics; Research grant / Funding (institution): Ono Pharmaceutical; Research grant / Funding (institution): Pfizer; Research grant / Funding (institution): Takeda. D.V. Catenacci: Honoraria (self), Advisory / Consultancy: Amgen; Honoraria (self), Advisory / Consultancy: Bristol-Myers Squibb; Honoraria (self): Five Prime Therapeutics; Honoraria (self), Speaker Bureau / Expert testimony: Foundation Medicine; Honoraria (self), Advisory / Consultancy: Genentech/Roche; Honoraria (self): GenMab; Honoraria (self): Gritstone Oncology; Honoraria (self), Speaker Bureau / Expert testimony: Guardant Health; Honoraria (self), Advisory / Consultancy: Lilly; Honoraria (self): Merck; Honoraria (self): NantOmics; Honoraria (self): OncoPlex Diagnostics; Honoraria (self), Advisory / Consultancy: Taiho Pharmaceutical; Advisory / Consultancy: Astellas Pharma. All other authors have declared no conflicts of interest.

1030 Background: Previous studies have shown that 44-71% of trastuzumab (T)-treated pts develop HER2-specific immunity (Clin Cancer Res 2007, 13:5133; Cancer Res 2016, 76:3702; Breast Cancer Res 2018, 20:52). M is an Fc-engineered mAb that shares similar HER2 binding and antiproliferative activity as T. The Fc region of M has been engineered for increased affinity to the activating FcγRIIIA (CD16A) and lower binding to the inhibitory FcγRIIB (CD32B), attributes that may enhance the mAb’s immune function, such as antigen presentation. Methods: HER2+ cancer pts who progressed on prior therapy received M (0.1-6 mg/kg QW for 3 of every 4 weeks [N = 34]; or 10-18 mg/kg Q3W [N = 32]) in phase 1 trial NCT01148849. PBMC and plasma were collected pre-dose and 50 days post-dose for 46 pts and > 4 years for 3 pts on long-term treatment. Response to HER2 or control antigens (Ag) was assessed by IFNγ ELISpot and antibody (Ab) ELISA. In 14 pts, T-cell antigen receptor (TCR) repertoire was assessed by immunosequencing. Results: Following M treatment, mean frequencies of IFNγ-producing T cells specific for intra- or extracellular fragments of HER2 increased by 2.5 to 6-fold (p < 0.0027, paired t test). Most (95%) of subjects responded to ≥2 of 6 (median = 5) HER2 Ag. Mean HER2-specific Ab concentration increased by 19-54% (p < 0.0001), with all subjects responding to ≥2 (median = 5) of the 6 Ag. A small 1.6-fold increase in IFNγ response to control CMV/EBV/Flu (but not tetanus or cyclin D1) peptides was observed; no increase in Ab response to control Ag was noted. Subsets of HER2-specific T-cell and Ab responses persisted during long-term treatment. Median TCR clonality increased by 54% (p = 0.003), with an average of 125 unique clones expanding, while overall TCR diversity remained unchanged (p = 0.19). Conclusions: Treatment of HER2+ cancer with M was associated with enhanced HER2-specific T-cell and Ab responses together with increased TCR clonality, indicative of a more focused T-cell repertoire. The high frequency of HER2-specific immunity in M-treated patients ( > 95%) is consistent with its enhanced Fc region contributing to linkage of innate and adaptive immune responses.

The first step in understanding the incentives provided to chief executive officers (CEOs) of large public firms is to measure their compensation accurately. This is not a straightforward task, as only partial information on compensation contracts is collected systematically (Execucomp, since 1992, for top executives of public U.S. firms). The source for the information is the compensation summary tables that the Securities and Exchange Commission mandates to be included in annual proxy statements. We show how to use this available data, together with stock price data in the Center for Research in Security Prices, to construct a measure of annual income that is based on realized compensation, rather than on the expected value of stock and option grants. We discuss the limitations of the available data to construct this measure and compare it to other measures recently used in the literature. We also propose a counterfactual exercise to project what annual income for CEOs in our sample would have been in different performance scenarios for their firm. We present our estimates of annual income and its sensitivity to performance for the period from 1993 to 2012, with a particular focus on the financial industry since the 2008 financial crisis.

Background: Flotetuzumab (FLZ; MGD006/S80880) is a novel CD123 x CD3 bispecific DART® protein being tested in a Phase 1/2 study (NCT02152956) in patients with relapsed/refractory acute myeloid leukemia (AML). As with all T-cell redirecting therapies, cytokine secretion, inherent in T-cell activation, with ensuing potential for cytokine release syndrome (CRS), remains an important side effect. We have previously reported that multi-step dosing mitigates CRS severity (1). CRS diagnosis and treatment is guided by the occurrence of non-specific clinical signs, such as fever, chills, hypotension and tachycardia. Therefore, identification of predictors of CRS will be useful for optimal pt. management. Here we report on potential biomarkers of CRS severity that may help guide CRS management. Methods: Data from pts treated with FLZ at RP2D (lead-in dose of 30ng/kg/d for 3d, 100ng/kg/d for 4d for week 1 followed by 500ng/kg/d CIV week 2-4 of cycle 1, and a 4d-on/3d-off schedule for Cycle 2 and beyond in 28-day cycles) was collected and analyzed. Incidence and severity of CRS were analyzed for correlation with cytokine levels and changes in BM blasts. Relation between immune cells (T-cell subsets, monocytes) with tumor burden, percent CD123+ AML blasts, and CD123 expression, were interrogated as potential determinants of CRS. Administration, dose and frequency of tocilizumab (TCZ), an IL-6 receptor antagonist, were evaluated for their relationship with CRS severity, frequency, CRP and cytokine levels. Results: 30 pts were dosed at RP2D. Most pts experienced mild to moderate CRS (G1 26.7%, G2 60%) of short duration (median 1 day(d), range 1-26 d) and were conservatively managed to full resolution. Grade ≥ 3 events occurred in 4/30 pts (13%), with vasopressors use in 2 pts, and a median duration of 2.5 d (range 2-13 d). CRS frequency decreased with time on treatment: 42% occurred within the first week (LID), 39.6% occurring in week 2 (step up to 500ng/kg/day) and 18% occurring during week 3 and 4. IL-6 levels showed the best relationship with CRS severity, as previously shown (1). IL-6 levels, however, did not correlate with response. Twenty pts (67%) received at least one dose of TCZ (median 2 doses/pt; range 1-12 doses). As anticipated, mean IL-6 levels increased after administration of TCZ. CRS severity showed a relationship with the baseline frequency of circulating CD4+ cells (median 47% in G1 vs 73% in G ≥2, p = 0.0082), while CD8+ cell frequency did not correlate with CRS. Disease burden (absolute AML blasts, % CD123 AML blasts), CD123 expression on AML blasts, monocytes levels or effector-to-target ratio in the peripheral blood did not show a relationship with CRS severity. Importantly, CRS severity was not correlated with FLZ anti-leukemic activity. Conclusion: The frequency of CD4+ cells at baseline may be a potential biomarker for identifying pts at risk of more severe CRS. Early use of TCZ can effectively modify the activity of IL-6, a significant contributor to CRS, and blunt CRS severity. Since severity of CRS and IL-6 levels did not correlate with FLZ anti-leukemic activity, blunting its severity should be aggressively pursued. Early identification of pts at greater CRS risk together with multistep dosing (1) and early use of TCZ can effectively manage CRS with no impact on FLZ anti-leukemic activity.Jacobs et al. ASH 2017, abstract #3856 Disclosures Jacobs: MacroGenics: Employment. Viero:Servier: Employment. Baughman:MacroGenics: Employment. Sun:MacroGenics: Employment. Ying:Macrogenics: Employment. Muth:MacroGenics: Employment. Hong:MacroGenics: Employment. Sweet:BMS: Honoraria; Agios: Consultancy; Phizer: Consultancy; Astellas: Consultancy; Jazz: Speakers Bureau; Jazz: Speakers Bureau; BMS: Honoraria; Novartis: Consultancy, Honoraria, Speakers Bureau; Celgene: Honoraria, Speakers Bureau; Agios: Consultancy; Phizer: Consultancy; Celgene: Honoraria, Speakers Bureau; Astellas: Consultancy; Novartis: Consultancy, Honoraria, Speakers Bureau. Uy:Curis: Consultancy; GlycoMimetics: Consultancy. Ravandi:Xencor: Research Funding; Macrogenix: Honoraria, Research Funding; Bristol-Myers Squibb: Research Funding; Astellas Pharmaceuticals: Consultancy, Honoraria; Abbvie: Research Funding; Jazz: Honoraria; Amgen: Honoraria, Research Funding, Speakers Bureau; Orsenix: Honoraria; Abbvie: Research Funding; Orsenix: Honoraria; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Sunesis: Honoraria; Sunesis: Honoraria; Xencor: Research Funding; Astellas Pharmaceuticals: Consultancy, Honoraria; Amgen: Honoraria, Research Funding, Speakers Bureau; Macrogenix: Honoraria, Research Funding; Jazz: Honoraria. Foster:Celgene: Research Funding; Macrogenics: Research Funding; Pfizer: Research Funding; Shire: Honoraria. Rizzieri:Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy; Arog: Consultancy, Membership on an entity's Board of Directors or advisory committees; Teva: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees. Arellano:Cephalon: Research Funding. Rettig:Amphivena Therapeutics: Research Funding; Novimmune: Research Funding. Topp:F. Hoffmann-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees, Research Funding; Regeneron Pharmaceuticals, Inc.: Honoraria, Research Funding; Boehringer Ingelheim: Research Funding; Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding. Lelièvre:Servier: Employment. Lowenberg:Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; international Scientific Advisory Board, Institute Gustave Roussy, Paris: Membership on an entity's Board of Directors or advisory committees; "Up-to-Date", section editor leukemia: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Astex: Consultancy; Supervisory Board, National Comprehensive Cancer Center (IKNL), Netherlands: Membership on an entity's Board of Directors or advisory committees; Editorial Board "European Oncology & Haematology": Membership on an entity's Board of Directors or advisory committees; Elected member, Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Chairman, Leukemia Cooperative Trial Group HOVON (Netherlands): Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees; Editorial Board "International Journal of Hematology": Membership on an entity's Board of Directors or advisory committees; Clear Creek Bio Ltd: Consultancy, Honoraria; Editorial Board "The Netherlands Journal of Medicine": Membership on an entity's Board of Directors or advisory committees; Chairman Scientific Committee and Member Executive Committee, European School of Hematology (ESH, Paris, France): Membership on an entity's Board of Directors or advisory committees. Wigginton:MacroGenics: Employment. Davidson-Moncada:MacroGenics: Employment.

Acute myeloid leukemia (AML) blasts and leukemia stem cells highly express the α chain of the IL-3 receptor (CD123), compared to normal hematopoietic stem cells. CD123 expression is associated with high-risk features, increased risk of induction failure and poor prognosis (Vergez F, et al. Haematologica 2011; 96: 1792-8). Flotetuzumab (FLZ), a CD123 × CD3 bispecific DART molecule, is being tested in a phase 1/2 study in patients with relapsed/refractory (R/R) AML. The recommended Phase 2 dose (RP2D) of FLZ is 500 ng/kg/day (d) administered as a 7-day/week continuous infusion. Patients receive a lead-in dose (30 ng/kg/d x 3d then 100 ng/kg/d x 4d) during week (W) 1, followed by 500 ng/kg/d during W2-4 of cycle 1, and a 4d on/3 d off schedule for cycle 2 and beyond. Disease status was assessed by modified IWG criteria; samples were collected to investigate candidate biomarkers, including CD123 receptor density/cell (RD), and gene expression profiling using the NanoString® PanCancer IO 360™ assay. This platform was used to assess the expression of 770 genes, including 14 immune cell types and 32 immuno-oncology biological signatures in bone marrow (BM) samples from patients treated with FLZ. Thirty patients with R/R AML, median age 64.5 years, received FLZ at the RP2D. Most patients enrolled had primary refractory disease (60% [18/30; 14 to cytotoxic chemotherapy (refractory to ≥ 2 induction attempts, or first CR with initial CR In conclusion, among this initial cohort of patients treated at the RP2D (500 ng/kg/day), FLZ demonstrates antileukemic activity with an acceptable safety profile, in particular, among refractory patients, a difficult-to-treat patient population that represents a significant area of unmet medical need. Enrollment to the current study has now been expanded to further define the antileukemic activity of FLZ in patients with refractory AML, and investigate candidate biomarkers to enable identification of patients more likely to respond to FLZ. In addition, studies are now being initiated to investigate opportunities to expand the antileukemic activity of FLZ via combined administration with either concurrent or sequenced anti-PD-1 checkpoint blockade. Disclosures Uy: GlycoMimetics: Consultancy; Curis: Consultancy. Rettig:Novimmune: Research Funding; Amphivena Therapeutics: Research Funding. Foster:Celgene: Research Funding; Macrogenics: Research Funding; Pfizer: Research Funding; Shire: Honoraria. Rizzieri:Arog: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Amgen: Consultancy, Membership on an entity's Board of Directors or advisory committees; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Consultancy; Teva: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Gilead: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Jazz: Consultancy, Membership on an entity's Board of Directors or advisory committees. Arellano:Cephalon: Research Funding. Topp:Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; Boehringer Ingelheim: Research Funding; Regeneron Pharmaceuticals, Inc.: Honoraria, Research Funding; F. Hoffmann-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees, Research Funding. Sweet:Phizer: Consultancy; BMS: Honoraria; BMS: Honoraria; Agios: Consultancy; Jazz: Speakers Bureau; Novartis: Consultancy, Honoraria, Speakers Bureau; Astellas: Consultancy; Astellas: Consultancy; Jazz: Speakers Bureau; Celgene: Honoraria, Speakers Bureau; Agios: Consultancy; Celgene: Honoraria, Speakers Bureau; Phizer: Consultancy; Novartis: Consultancy, Honoraria, Speakers Bureau. Ravandi:Abbvie: Research Funding; Xencor: Research Funding; Astellas Pharmaceuticals: Consultancy, Honoraria; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Jazz: Honoraria; Jazz: Honoraria; Macrogenix: Honoraria, Research Funding; Sunesis: Honoraria; Bristol-Myers Squibb: Research Funding; Seattle Genetics: Research Funding; Amgen: Honoraria, Research Funding, Speakers Bureau; Orsenix: Honoraria; Macrogenix: Honoraria, Research Funding; Amgen: Honoraria, Research Funding, Speakers Bureau; Xencor: Research Funding; Orsenix: Honoraria; Astellas Pharmaceuticals: Consultancy, Honoraria; Sunesis: Honoraria; Abbvie: Research Funding. Church:NanoString Technologies: Employment. Rutella:NanoString Technologies: Research Funding. Sun:MacroGenics: Employment. Yang:MacroGenics: Employment. Baughman:MacroGenics: Employment. Curtis:MacroGenics: Employment. Timmeny:MacroGenics: Employment. Cali:MacroGenics: Employment. Tran:MacroGenics: Employment. Muth:MacroGenics: Employment. La Motte-Mohs:MacroGenics: Employment, Equity Ownership. Poirot:Servier: Employment. Pallis:Servier: Employment. Cesano:NanoString Technologies: Employment. Bonvini:MacroGenics: Employment, Equity Ownership. Wigginton:MacroGenics: Employment. Lowenberg:Astex: Consultancy; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; Clear Creek Bio Ltd: Consultancy, Honoraria; Celgene: Membership on an entity's Board of Directors or advisory committees; Supervisory Board, National Comprehensive Cancer Center (IKNL), Netherlands: Membership on an entity's Board of Directors or advisory committees; Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; international Scientific Advisory Board, Institute Gustave Roussy, Paris: Membership on an entity's Board of Directors or advisory committees; Editorial Board "International Journal of Hematology": Membership on an entity's Board of Directors or advisory committees; Elected member, Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Chairman, Leukemia Cooperative Trial Group HOVON (Netherlands): Membership on an entity's Board of Directors or advisory committees; Chairman Scientific Committee and Member Executive Committee, European School of Hematology (ESH, Paris, France): Membership on an entity's Board of Directors or advisory committees; Editorial Board "The Netherlands Journal of Medicine": Membership on an entity's Board of Directors or advisory committees; "Up-to-Date", section editor leukemia: Membership on an entity's Board of Directors or advisory committees; Editorial Board "European Oncology & Haematology": Membership on an entity's Board of Directors or advisory committees. Davidson-Moncada:MacroGenics: Employment.

Background. The therapeutic approach in patients (pts) with acute myeloid leukemia (AML) has not changed substantially in >30 years. The introduction of new treatment strategies, including immunotherapy, remains a priority. Flotetuzumab, a CD123 × CD3 bispecific DART immunotherapy, is being tested in a phase 1/2 study of relapsed/refractory (R/R) AML. We previously showed that AML pts with an immune-enriched and IFN-γ-dominant tumor microenvironment (TME) experience significantly shorter relapse-free survival, suggesting refractoriness to standard induction chemotherapy (Vadakekolathu J, et al. Blood 2017; 130: 3942A). Herein, we report that an IFN-γ-dominant TME, while predicting resistance to standard therapy, is favoring response of AML to flotetuzumab. Methods. Gene expression was analyzed in 78 bone marrow (BM) samples (36 at baseline, 27 post-cycle 1 and 15 post-cycle 2) from 40 pts with relapsed or refractory AML enrolled in a phase 1/2 clinical trial of flotetuzumab (NCT#02152956). Thirty-six baseline BM samples were included in the analysis, of which 34 from pts who were treated at the target dose of ≥500 ng/kg/day. The NanoString PanCancer IO360™ assay was used to assess the expression of 770 genes, including the levels of 14 immune cell types and of 32 immuno-oncology signatures, and their correlation with response to flotetuzumab. Data are presented as score means per group±SEM and analyzed by unpaired t-test. Results. Gene expression analysis of BM samples at baseline stratifies flotetuzumab-treated pts into 3 clusters within an immunological continuum: immune-depleted, immune-exhausted and immune-enriched (Fig. 1A). Pts with primary-refractory disease (refractory to ≥2 induction attempts, first CR of Conclusions. We provide evidence for a range of immune gene expression profiles in AML, with primary refractory pts displaying an enhanced immune infiltration signature compared with relapse pts. Furthermore, an IFN-γ-related gene signature at baseline, a feature of primary refractory pts, was associated with clinical response to flotetuzumab. HMA-refractory pts showed an immune-rich but exhausted phenotype with PD-L1 expression, suggesting these pts may further benefit from flotetuzumab combination therapy with checkpoint inhibition (Rettig M, et al. Blood 2017; 130: 1365). Lastly, treatment with flotetuzumab further shifted the immune signature toward a more immune rich phenotype. The AML TME immune gene expression can influence susceptibility to therapy, with primary refractory AML showing an IFN-γ-dominant signature associated with response to flotetuzumab. Figure Figure. Disclosures Rutella: NanoString Technologies: Research Funding. Church:NanoString Technologies: Employment. Viboch:NanoString Technologies: Employment. Sullivan:NanoString Technologies: Employment. Hood:NanoString Technologies: Employment. Warren:NanoString Technologies: Employment. Cesano:NanoString Technologies: Employment. La Motte-Mohs:MacroGenics: Employment, Equity Ownership. Muth:MacroGenics: Employment. Lelièvre:Servier: Employment. Lowenberg:Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Agios Pharmaceuticals: Membership on an entity's Board of Directors or advisory committees; international Scientific Advisory Board, Institute Gustave Roussy, Paris: Membership on an entity's Board of Directors or advisory committees; Clear Creek Bio Ltd: Consultancy, Honoraria; Chairman Scientific Committee and Member Executive Committee, European School of Hematology (ESH, Paris, France): Membership on an entity's Board of Directors or advisory committees; Editorial Board "European Oncology & Haematology": Membership on an entity's Board of Directors or advisory committees; Editorial Board "The Netherlands Journal of Medicine": Membership on an entity's Board of Directors or advisory committees; Elected member, Royal Academy of Sciences and Arts, The Netherlands: Membership on an entity's Board of Directors or advisory committees; Supervisory Board, National Comprehensive Cancer Center (IKNL), Netherlands: Membership on an entity's Board of Directors or advisory committees; Chairman, Leukemia Cooperative Trial Group HOVON (Netherlands): Membership on an entity's Board of Directors or advisory committees; Editorial Board "International Journal of Hematology": Membership on an entity's Board of Directors or advisory committees; "Up-to-Date", section editor leukemia: Membership on an entity's Board of Directors or advisory committees; Astex: Consultancy; Celgene: Membership on an entity's Board of Directors or advisory committees. Davidson-Moncada:MacroGenics: Employment.

4030Background: T + chemo is standard 1st line therapy (tx) for HER2+ GEA patients (pts). However, pts typically progress within 6-8 months, with up to 30% demonstrating loss of HER2 positivity. No...

The goal of this proposal was to investigate the potential advantages of integrating III-V nitride structures on doped sapphire substrates and doped sapphire waveguide structures. III-V Nitride structures are typically grown on undoped synthetic sapphire or silicon carbide neither of which efficiently luminescence. However, Cr:Sapphire and especially Ti:Sapphire are very useful solid state laser materials used in ruby lasers (694 nm) and tunable (660-1100) Ti:sapphire, thus very efficient optical pumping powers on the order of several watts and supporting infrastructure to remove the heat is required. By confining the optical pump energy to the waveguide, simultaneous pump and signal beam confinement could potentially lead to a reduction in lasing threshold. Utilizing the red emission from the Cr in the sapphire could also permit the construction of white light LEDs. Ultimately, an integrated III-V Nitride optical pump for Ti:Sapphire could lead to the development of ultra compact tunable vibronic lasers for spectroscopy applications such as chemical and biological sensing.

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