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BACKGROUND: Relapsed/refractory (R/R) B-cell non-Hodgkin lymphoma (B-NHL) remains an area of high unmet patient need and no curative options are currently available. Odronextamab (REGN1979) is a first-in-class, hinge-stabilized, fully human IgG4-based bispecific antibody that binds to CD20-expressing cells and CD3 on T cells, targeting CD20+ cells via T-cell-mediated cytotoxicity independent of T-cell receptor recognition. The safety, tolerability, and anti-tumor activity of odronextamab monotherapy was evaluated in a global, multicenter, Phase 1 study in heavily pretreated patients with R/R B-NHL (NCT02990951; Bannerji et al, ASH 2019). Intravenous infusion of odronextamab has demonstrated an acceptable safety profile at doses up to 320 mg weekly (QW), and the maximum tolerated dose was not reached. Broad and durable anti-tumor responses were observed in both indolent and aggressive lymphomas, including in patients who progressed after prior CAR T-cell therapy. An assessment of pharmacokinetics, efficacy and safety data from the Phase 1 study informed the recommended Phase 2 dosing regimens. METHODS: This global, Phase 2, open-label, multi-cohort study (R1979-ONC-1625; NCT03888105) is designed to assess the anti-tumor activity and safety of odronextamab in patients with B-NHL. There are five disease-specific cohorts, each with independent parallel enrollment. The study includes patients with: (1) R/R follicular lymphoma (FL) Grade 1-3a after ≥2 prior lines of systemic therapy, including an anti-CD20 antibody and an alkylating agent; (2) R/R diffuse large B-cell lymphoma (DLBCL) after ≥2 lines of systemic therapy, including an anti-CD20 antibody and an alkylating agent; (3) R/R mantle cell lymphoma (MCL) following or with failure to tolerate Bruton's tyrosine kinase inhibitor therapy; (4) R/R marginal zone lymphoma (MZL) after ≥2 lines of systemic therapy; (5) other R/R B-NHL subtypes, excluding Waldenström macroglobulinemia, after ≥2 lines of systemic therapy (Fig. 1). Estimated total enrollment is 481 patients. Key eligibility criteria are: age ≥18 years; not appropriate for other approved therapy with established benefit; ≥1 bi-dimensionally measurable nodal lesion of ≥1.5 cm; Eastern Cooperative Oncology Group performance status ≤1; and adequate bone marrow, renal, and hepatic function. Key exclusion criteria are: prior anti-CD20 x CD3 bispecific antibody therapy; prior CAR T-cell therapy; primary central nervous system (CNS) lymphoma or known involvement by non-primary CNS NHL; and history of allogeneic hematopoietic stem cell transplantation. Odronextamab is administered using a step-up dose schedule consisting of an initial dose at Week (W)1, an intermediate dose at W2, and thereafter, a fixed weekly dose until W12 followed by maintenance Q2W dosing until progression or discontinuation (Fig. 2). The dose for indolent B-NHL is 80 mg QW followed by 160 mg Q2W, and for aggressive B-NHL is 160 mg QW followed by 320 mg Q2W. All patients with durable complete responses of 9 months will transition from Q2W to Q4W dosing. The primary endpoint for each cohort is objective response rate (ORR) by independent central review, as assessed from first dose until completion of 28 weeks of study treatment, or study withdrawal. Secondary endpoints include complete response (CR) rate, progression-free survival, duration of response, disease control rate (DCR), overall survival, incidence and severity of treatment-emergent adverse events, pharmacokinetics, immunogenicity, and patient-reported outcomes. ORR, CR rate and DCR with a two-sided 95% confidence interval (CI) will be summarized. Time-to-event endpoints will be summarized by median and corresponding 95% CI using the Kaplan-Meier method. The study is actively accruing patients at sites across North America, Europe, and Asia-Pacific. Disclosures Kim: AstraZeneca: Consultancy; Novartis: Consultancy; Takeda: Consultancy; Sanofi: Consultancy; F. Hoffmann-La Roche Ltd/Genentech, Inc.: Consultancy; Voronoi: Consultancy; Boryung: Consultancy; AstraZeneca and Korea Health Industry Development Institute: Research Funding. Stevens:Amgen, MorphoSys: Consultancy. Poon:Astrazeneca, Pfizer, Takeda, Janssen, Roche, Novartis: Honoraria. Le Gouill:Loxo Oncology at Lilly: Consultancy; Roche Genentech, Janssen-Cilag and Abbvie, Celgene, Jazz pharmaceutical, Gilead-kite, Loxo, Daiichi-Sankyo and Servier: Honoraria. Carpio:Takeda, Regeneron: Consultancy. Keating:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Taiho: Membership on an entity's Board of Directors or advisory committees; Shire: Membership on an entity's Board of Directors or advisory committees; Servier: Membership on an entity's Board of Directors or advisory committees; Seattle Genetics: Consultancy; Sanofi: Membership on an entity's Board of Directors or advisory committees; Merck: Membership on an entity's Board of Directors or advisory committees; Janssen: Membership on an entity's Board of Directors or advisory committees; Hoffman La Roche: Membership on an entity's Board of Directors or advisory committees; Takeda: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Adriaens:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company, Patents & Royalties: Dosing regime that mitigates cytokine release syndrome for therapeutic antibodies (status: pending). Ufkin:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Sabir:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Li:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Jankovic:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Zhu:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Brouwer-Visser:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Leng:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Sirulnik:Regeneron Pharmaceuticals, Inc.: Current Employment, Current equity holder in publicly-traded company. Chaudhry:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Ambati:Regeneron Pharmaceuticals, Inc: Current Employment, Current equity holder in publicly-traded company. Won Seog:Roche, Takeda, J&J, Kyowa-Kirin, Celltrion ,Pfizer, Donga: Research Funding. OffLabel Disclosure: The Trial in Progress abstract will report on use of odronextamab in a Phase 2 clinical trial of patients with B-NHL

Purpose: Nesvacumab (REGN910) is a fully human immunoglobulin G1 (IgG1) monoclonal antibody that specifically binds and inactivates the Tie2 receptor ligand Ang2 with high affinity, but shows no binding to Ang1. The main objectives of this trial were to determine the safety, tolerability, dose-limiting toxicities (DLT), and recommended phase II dose (RP2D) of nesvacumab. Experimental Design: Nesvacumab was administered intravenously every two weeks with dose escalations from 1 to 20 mg/kg in patients with advanced solid tumors. Results: A total of 47 patients were treated with nesvacumab. No patients in the dose escalation phase experienced DLTs, therefore a maximum tolerated dose (MTD) was not reached. The most common nesvacumab-related adverse events were fatigue (23.4%), peripheral edema (21.3%), decreased appetite, and diarrhea (each 10.6%; all grade ≤ 2). Nesvacumab was characterized by linear kinetics and had a terminal half-life of 6.35 to 9.66 days in a dose-independent manner. Best response by RECIST 1.1 in 43 evaluable patients included 1 partial response (adrenocortical carcinoma) of 24 weeks duration. Two patients with hepatocellular carcinoma had stable disease (SD) > 16 weeks, with tumor regression and >50% decrease in α-fetoprotein. Analyses of putative angiogenesis biomarkers in serum and tumor biopsies were uninformative for treatment duration. Conclusions: Nesvacumab safety profile was acceptable at all dose levels tested. Preliminary antitumor activity was observed in patients with treatment-refractory advanced solid tumors. On the basis of cumulative safety, antitumor activity, pharmacokinetic and pharmacodynamic data, the 20 mg/kg dose was determined to be the RP2D. Clin Cancer Res; 22(6); 1348–55. ©2015 AACR.

Background REGN1979 is an anti-CD20 x anti-CD3 bispecific IgG4 antibody (Ab) modified to reduce Fc binding. Engaging both targets results in CD20-specific, local T-cell activation and cytotoxicity, a mechanism of action distinct from standard anti-CD20 Abs. Dose escalation is complete and a recommended Ph 2 dose has been determined. We report Ph 1 safety and efficacy results of REGN1979 in patients (pts) with R/R B-NHL previously treated with anti-CD20 Abs, including pts with progressive disease after anti-CD19 CAR T-cell (CAR T) therapy. Methods Primary objectives are to determine safety, tolerability, and occurrence of dose limiting toxicities (DLTs). Other objectives are to assess antitumor activity, pharmacokinetics (PK), and pharmacodynamics. Eligible pts with R/R B-NHL must have received prior CD20-directed therapy. Treatment consists of 12 weekly intravenous doses of REGN1979 followed by every 2-week dosing for 12 doses (36 weeks total). Results As of June 3, 2019, 96 pts (diffuse large cell B-cell lymphoma [DLBCL] [n=53], follicular lymphoma [FL] grade [Gr] 1-3a [n=25], mantle cell lymphoma [n=6], marginal zone lymphoma [n=6], or other [FL Gr 3b, FL unknown, FL ungraded, or Waldenström macroglobulinemia ] [n=6]) were treated with REGN1979 0.03-320 mg and received a median of 9 doses (range 1-24). Pts had a median of 3 prior lines of therapy (range 1-11); 12 pts with prior CAR T therapy were included in the safety analysis of which 6 were included in the efficacy analysis. Twenty-four pts remain on treatment; 18 completed treatment; 54 discontinued early (35 due to progressive disease [PD]). No pts with B-NHL experienced a DLT. The most common treatment-emergent adverse events (AEs) were pyrexia (n=74), CRS (n=55), chills (n=49), infections and infestations (n=47), fatigue (n=36), increased C-reactive protein (n=32), and anemia (n=32). Seven pts experienced Gr 3 CRS. The severity of CRS symptoms declined through optimized pre-medication even with REGN1979 dose escalation. Most common Gr 3 or 4 AEs were anemia (n=19), decreased lymphocytes/lymphopenia (n=19), infections and infestations (n=18), decreased neutrophils/neutropenia (n=17), and hypophosphatemia/decreased blood phosphorus (n=16). No pts had seizures or grade 4/5 neurologic AEs. Gr 3 neurologic AEs included depressed level of consciousness (unrelated), somnolence, and syncope (n=1 each). Neurological events were transient and none required permanent treatment termination. Five pts discontinued due to AEs: Gr 3 hemolysis; Gr 3 fatigue; Gr 2 and Gr 3 pneumonia; and Gr 3 neck abscess (1 each). Eleven pts died on study: PD (n=6), gastric perforation (n=1), cardiac arrest (n=1), lung infection (n=1), multi-organ failure (n=1), pneumonia (n=1). The Table and Figure show efficacy and duration of response for R/R DLBCL by dose level. Pts who had opportunity for response assessment at Week 12 were included in the analysis of response. Emerging data suggest increasing efficacy with higher doses in R/R DLBCL, with 5 of 8 pts treated at 80/160/320 mg achieving CR; at these doses 2 of 3 pts achieved CR after failure of CAR T therapy. Data also suggest increasing efficacy with increasing doses in R/R FL, but maximum efficacy appears to be achieved at lower doses than in DLBCL; in pts with FL Gr 1-3a treated at ≥5 mg, the ORR was 93% (13/14), and the CR rate was 71.4% (10/14). REGN1979 concentrations in serum increased linearly with dose during the first five weeks. Elevated levels of serum cytokines were observed, mostly in week 1, and no correlation was observed with clinical efficacy. Immunohistological analysis of malignant lymph node tissue demonstrated that pts with high and low CD20 expression achieved clinical response. Relapse among responders was seen with either maintenance or loss of CD20 expression, suggesting antigen-dependent and independent disease escape mechanisms. Conclusions/Summary Tolerability of REGN1979 has been demonstrated at doses up to the final dose level of 320 mg weekly, with no observed DLTs in pts with B-NHL. No pts discontinued due to neurologic AE. Activity was observed broadly in heavily pretreated R/R B-NHL pts treated with REGN1979. With increasing dose, more resistant tumors such as R/R DLBCL are showing benefit, even in pts with prior CAR T therapy failure. Based on these efficacy findings, a global Ph 2 study is underway to evaluate REGN1979 monotherapy in R/R FL Gr 1-3a, R/R DLBCL, and other R/R B-NHL subtypes. Disclosures Bannerji: AbbVie, Inc: Consultancy, travel support; Gilead: Other: travel support; Gilead: Other: travel support; Pharmacyclics: Other: travel support; Merck: Other: travel support, Patents & Royalties: IP rights; AbbVie, Inc: Consultancy; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Celgene: Consultancy; Celgene: Consultancy; Merck: Other: travel support, Patents & Royalties: IP rights; Pharmacyclics: Other: travel support. Allan:Acerta Pharma: Consultancy; Sunesis Pharmaceuticals: Consultancy, Membership on an entity's Board of Directors or advisory committees; AbbVie, Inc: Consultancy, Membership on an entity's Board of Directors or advisory committees; Pharmacyclics LLC, an AbbVie company: Consultancy; Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Consultancy; Verastem Oncology, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy, Honoraria. Arnason:Celgene/Juno: Consultancy; Regeneron Pharmaceuticals, Inc.: Consultancy. Brown:AstraZeneca: Consultancy; Acerta Pharma: Consultancy; Morphosys: Other: Data safety monitoring boards ; Sun Pharmaceuticals, Inc: Research Funding; Sun: Research Funding; Verastem: Consultancy, Research Funding; TG Therapeutics: Consultancy; Teva: Honoraria; Sunesis: Consultancy; Pharmacyclics: Consultancy; Pfizer: Consultancy; Janssen: Honoraria; Invectys: Other: other; Loxo: Consultancy, Research Funding; Novartis: Consultancy; Octapharma: Consultancy; Kite: Consultancy, Research Funding; Dynamo Therapeutics: Consultancy; Catapult Therapeutics: Consultancy; BeiGene: Consultancy; Gilead: Consultancy, Research Funding; Genentech/Roche: Consultancy. Advani:Kyowa Kirin Pharmaceutical Developments, Inc.: Consultancy; Seattle Genetics: Consultancy, Research Funding; Celmed: Consultancy, Membership on an entity's Board of Directors or advisory committees; Forty-Seven: Research Funding; Roche/Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kura: Research Funding; Bayer: Consultancy, Membership on an entity's Board of Directors or advisory committees; Millennium: Research Funding; Gilead Sciences, Inc./Kite Pharma, Inc.: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Bristol-Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Research Funding; Infinity Pharma: Research Funding; Janssen: Research Funding; Merck: Research Funding; Takeda: Consultancy, Membership on an entity's Board of Directors or advisory committees; Cell Medica, Ltd: Consultancy; Autolus: Consultancy, Membership on an entity's Board of Directors or advisory committees; Agensys: Research Funding; AstraZeneca: Consultancy, Membership on an entity's Board of Directors or advisory committees; Stanford University: Employment, Equity Ownership; Regeneron: Research Funding; Pharmacyclics: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Ansell:Seattle Genetics: Research Funding; Trillium: Research Funding; Seattle Genetics: Research Funding; Trillium: Research Funding; Regeneron: Research Funding; Mayo Clinic Rochester: Employment; Regeneron: Research Funding; LAM Therapeutics: Research Funding; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Mayo Clinic Rochester: Employment; Mayo Clinic Rochester: Employment; LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; Regeneron: Research Funding; Bristol-Myers Squibb: Research Funding; Trillium: Research Funding; Bristol-Myers Squibb: Research Funding; Affimed: Research Funding; Bristol-Myers Squibb: Research Funding; LAM Therapeutics: Research Funding; Seattle Genetics: Research Funding; Affimed: Research Funding; Mayo Clinic Rochester: Employment; Seattle Genetics: Research Funding; Seattle Genetics: Research Funding; Affimed: Research Funding; Affimed: Research Funding; Trillium: Research Funding; LAM Therapeutics: Research Funding; Affimed: Research Funding; Bristol-Myers Squibb: Research Funding; LAM Therapeutics: Research Funding; Regeneron: Research Funding; Regeneron: Research Funding; Affimed: Research Funding; Affimed: Research Funding; Regeneron: Research Funding; Bristol-Myers Squibb: Research Funding; LAM Therapeutics: Research Funding; Bristol-Myers Squibb: Research Funding; LAM Therapeutics: Research Funding; Trillium: Research Funding; Seattle Genetics: Research Funding; Affimed: Research Funding; Regeneron: Research Funding; Trillium: Research Funding; LAM Therapeutics: Research Funding; LAM Therapeutics: Research Funding; Trillium: Research Funding; Mayo Clinic Rochester: Employment; Regeneron: Research Funding; Trillium: Research Funding; Seattle Genetics: Research Funding; Bristol-Myers Squibb: Research Funding; Trillium: Research Funding; Affimed: Research Funding; Bristol-Myers Squibb: Research Funding; Mayo Clinic Rochester: Employment; Mayo Clinic Rochester: Employment; Mayo Clinic Rochester: Employment; Regeneron: Research Funding; Mayo Clinic Rochester: Employment. O'Brien:Pfizer: Consultancy, Honoraria, Research Funding; AbbVie: Consultancy, Honoraria; Acerta: Research Funding; Alexion: Consultancy; Amgen: Consultancy; Aptose Biosciences, Inc: Consultancy; Astellas: Consultancy; Celgene: Consultancy; Eisai: Consultancy; Gilead: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; Kite: Research Funding; Janssen: Consultancy, Honoraria; Pharmacyclics LLC, an AbbVie Company: Consultancy, Research Funding; Regeneron: Research Funding; Verastem: Consultancy; Sunesis: Consultancy, Research Funding; Vaniam Group LLC: Consultancy; TG Therapeutics: Consultancy, Research Funding. Chavez:Janssen Pharmaceuticals, Inc.: Speakers Bureau; Kite Pharmaceuticals, Inc.: Membership on an entity's Board of Directors or advisory committees; Genentech: Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees. Duell:Regeneron Pharmaceuticals, Inc.: Research Funding. Martin:I-MAB: Consultancy; Karyopharm: Consultancy; Celgene: Consultancy; Janssen: Consultancy; Sandoz: Consultancy; Teneobio: Consultancy. Charnas:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ambati:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Adriaens:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ufkin:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Zhu:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Li:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Gasparini:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ibrahim:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Jankovic:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Fiaschi:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Aina:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Zhang:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Deering:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Hamon:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Thurston:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Murphy:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Weinreich:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Yancopoulos:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Lowy:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Sternberg:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Topp:Amgen: 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; 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. OffLabel Disclosure: The data described in the abstract will report on use REGN1979 in a Phase 1 clinical trial of patients with B-NHL.

Background NHL is the most common hematological malignancy. Among a heterogeneous group of NHLs, 85-90% are of B-cell origin and include follicular lymphoma (FL), diffuse large B-cell lymphoma (DLBCL), mantle cell lymphoma (MCL), marginal zone lymphoma (MZL), and several other B-NHLs. Anti-CD20 Abs in combination with chemotherapy are the standard of care for the treatment of B-NHLs; however, despite initial responses, many patients relapse, often with progressively shorter response durations in subsequent lines of therapy and poor outcome. REGN1979 is a CD20 x CD3 bispecific IgG4 Ab that binds to CD3+ T-cells and CD20+ B-cells, targeting CD20+ tumor cells via T-cell-mediated cytotoxicity. An ongoing Phase 1 study in patients with B-cell malignancies is evaluating the safety, tolerability, and efficacy of REGN1979 as monotherapy (NCT02290951). Preliminary data from the Phase 1 study showed broad antitumor activity with REGN1979 in heavily pretreated R/R B-NHL patients, including some with progression after prior chimeric antigen receptor T (CAR T)-cell therapy. REGN1979 has been tolerated at doses up to 320 mg weekly, with no observed dose limiting toxicities. These data informed the dosage regimen of the current Phase 2 study. Methods This open-label, multi-center, Phase 2 study (NCT03888105) is evaluating the efficacy and safety of REGN1979 in six disease-specific cohorts, each comprising a single arm with independent parallel enrollment: patients with R/R FL Grade 1-3a after ≥2 prior lines of systemic therapy, including an anti-CD20 antibody and an alkylating agent; patients with R/R DLBCL after ≥2 prior lines of systemic therapy (patients in this cohort may not have received prior CAR T-cell therapy); patients with R/R DLBCL after CAR T-cell therapy failure; patients with MCL that have relapsed after or are refractory to Bruton's tyrosine kinase (BTK) inhibitor therapy (patients with R/R MCL who have demonstrated intolerance to BTK inhibitor therapy may also be enrolled); patients with R/R MZL that have relapsed after or are refractory to ≥1 prior line of systemic therapy; patients with R/R other B-NHL subtypes, excluding Waldenström macroglobulinemia, after ≥1 prior line of systemic therapy including an anti-CD20 antibody. The initial screening period of up to 28 days is followed by a weekly dosing period where REGN1979 is administered in gradually increasing doses to achieve target nominal dose by Week 4 and continued through Week 12. Patients then receive REGN1979 every two weeks for up to 86 weeks (total treatment period of 98 weeks). The post-treatment follow-up period will continue for up to 96 weeks after the last dose of study treatment. Approximately 481 patients will be enrolled at sites across the US, Canada, Europe, and the Asia-Pacific region. Key eligibility criteria are: age ≥18 years; ≥1 bi-dimensionally measurable nodal lesion of ≥1.5 cm; Eastern Cooperative Oncology Group performance status of 0 or 1; and adequate bone marrow and hepatic functions. Key exclusion criteria include primary central nervous system (CNS) lymphoma or involvement by non-primary CNS NHL; treatment with systemic anti-lymphoma therapy within five half-lives or 28 days prior to first administration of REGN1979; and history of allogeneic hematopoietic stem cell transplantation. The primary endpoint for each disease-specific cohort is objective response rate (ORR) according to the Lugano Classification of response in malignant lymphoma by independent central review. Secondary endpoints include complete response (CR) rate, progression-free survival, duration of response, disease control rate (DCR), duration of disease control, overall survival; incidence and severity of treatment-emergent adverse events; patient-reported outcomes; pharmacokinetics; and immunogenicity responses. The primary endpoint, ORR, will be summarized along with a two-sided 95% confidence interval (CI). Other efficacy endpoints, such as CR rate and DCR, will be summarized using the same approach as for ORR. The time to event endpoints will be summarized, where appropriate, by median and the corresponding 95% CI using the Kaplan-Meier method. The study is recruiting in FL grade 1-3a cohort and recruitment in other disease-specific cohorts is planned. Disclosures Topp: Boehringer Ingelheim: 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; 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. Duell:Regeneron Pharmaceuticals, Inc.: Research Funding. Li:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Jankovic:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Lowy:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Sternberg:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Adriaens:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Peterman:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ambati:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Bannerji:AbbVie, Inc: Consultancy, travel support; Celgene: Consultancy; Pharmacyclics: Other: travel support; Pharmacyclics: Other: travel support; Gilead: Other: travel support; Gilead: Other: travel support; AbbVie, Inc: Consultancy; Merck: Other: travel support, Patents & Royalties: IP rights; Celgene: Consultancy; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Regeneron Pharmaceuticals, Inc.: Consultancy, Other: travel support, Research Funding; Merck: Other: travel support, Patents & Royalties: IP rights. OffLabel Disclosure: The abstract outlines data on the use of REGN1979 in a Phase 1 trial in patients with relapsed/refractory B-cell non-Hodgkin lymphoma and describes the design of a Phase 2 trial in a similar patient population.

Introduction REGN1979 is an anti-CD20 x anti-CD3 bispecific IgG4 antibody (Ab) modified to reduce Fc binding. Engaging both targets results in CD20-specific, local T-cell activation and cytotoxicity, a mechanism of action distinct from standard anti-CD20 Abs. We report updated promising efficacy results of a Phase 1 trial of REGN1979 in patients (pts) with relapsed/refactory (R/R) B-NHL previously treated with anti-CD20 Abs. Methods The primary objectives of the study are to determine safety, tolerability, and occurrence of dose limiting toxicities (DLTs). Other objectives include assessment of preliminary antitumor activity, pharmacokinetics (PK), and pharmacodynamics. Eligible pts with R/R NHL must have received at least 1 prior CD20-directed therapy. Treatment consists of 12 weekly doses of REGN1979 followed by every 2 week dosing for 12 doses for a total of 36 weeks. Guidelines are provided for management of cytokine release syndrome (CRS) and include steroids and/or tocilizumab at investigator discretion. Results As of June 1, 2018, 54 pts with B-NHL were treated with REGN1979 monotherapy: DLBCL (pt number [n]=30), FL (n=16), MCL (n=5), MZL (n=2), and WM (n=1). The median number of prior regimens was 3 (range, 1-11); 41 pts were refractory to their last prior systemic therapy, 18 had bulky disease, and 6 had prior HSCT. Pts were treated with REGN1979 0.03-27 mg and received a median of 7 (range, 1-24) doses. Eight pts remain on treatment, 13 completed treatment, and 33 discontinued therapy prior to the planned 36 wks (majority [n=22] due to progressive disease [PD]). There have been no DLTs to date. The most common treatment-related treatment-emergent adverse events (TR-TEAEs) included infusion-related reactions (IRR) or CRS; 26 pts experienced CRS (Grade 1-2, n=23; Grade 3, n=3) with a median duration of CRS of 2 (range 1-15) days. Six pts received tocilizumab. The severity of CRS symptoms declined through optimized pre-medication even with REGN1979 dose escalation. Other common Grade ≥3 TR-TEAEs were lymphocytopenia/ decreased lymphocyte count (n=8); neutropenia/ decreased neutrophil count (n=7); and thrombocytopenia/ decreased platelet count, hypotension, hypophosphatemia, and anemia (each n=3). Seventeen pts experienced a nervous system event including headache, dizziness, paraesthesia, dysgeusia, and peripheral neuropathy with no Grade ≥3 events; no neurologic event required termination of study drug. Seven pts died on study: PD (n=5), gastric perforation (n=1), and cardiac arrest (n=1). TEAEs leading to premature discontinuation of REGN1979 were Grade 3 fatigue (n=1), Grade 3 hemolysis (n=1), and Grade 2 pyrexia/Grade 2 tachycardia (n=1). Among 27 pts treated with REGN1979 ≥5 mg (dose associated with tumor killing in pre-clinical data), the overall response rate (ORR) was 55.6% (5 complete response [CR] and 10 partial response [PR]; Table/Figure). Responses were seen in 7/7 FL Grade 1-3a pts (5 CR, 2 PR), 6/15 DLBCL pts (all PR), 2/2 MCL pts (all PR). At 18 mg and 27 mg of REGN1979, 4 of 4 pts with DLBCL had best response of PR. Post data cut-off, 1 pt with a DLBCL best response of PR converted to CR. PK and pharmacodynamic assessments suggest that for pts treated with REGN1979 5-18 mg, best exposures in the first 3 weeks appear to linearly increase with dose. In pts treated with up to REGN1979 18 mg, a maximum mean Ctrough of 1.6 mcg/mL was observed in the first 3 weeks of weekly dosing. Studies of peripheral blood biomarkers demonstrated depletion of peripheral B lymphocytes, transient margination of circulating T-cells, and elevated circulating cytokines following REGN1979 dosing. Increased peak cytokine levels (IL-6, IL-10, and TNF-alpha) were observed in pts with CRS. Immunohistological analysis of malignant lymph node tissue demonstrated a decrease of CD20 expression in responding pts; among the responders, subsequent relapse was associated with either maintenance of CD20 expression or further CD20 loss, suggesting antigen-dependent and independent disease escape mechanisms. Conclusions REGN1979 displays efficacy and an acceptable safety profile in pts with R/R B-NHL. Most TR-TEAEs were IRR/CRS and have been well managed with supportive care. No significant neurological toxicity has been observed. At doses of 5-27 mg of REGN1979, the preliminary ORR was 100% in pts with FL Grade 1-3a and 40.0% in pts with DLBCL. This promising efficacy warrants further clinical investigation. Disclosures Bannerji: Regeneron Pharmaceuticals, Inc.: Consultancy; AbbVie, Inc.: Consultancy. Arnason:Regeneron Pharmaceuticals, Inc.: Consultancy. Advani:Bayer Healthcare Pharmaceuticals: Other: Consultancy/Advisory Role; Janssen Pharmaceutical: Other: Institutional Research Support; Bristol Myers Squibb: Other: Consultancy/Advisory role and Institutional Research Support; Pharmacyclics: Other: Institutional Research Support; Takeda: Other: Consultancy/Advisory Role; Millenium: Other: Institutional Research Support; Gilead/Kite: Other: Consultancy/Advisory Role; Infinity: Other: Institutional Research Support; Merck: Other: Institutional Research Support; Forty Seven, Inc: Other: Institutional Research Support; Cell Medica: Other: Consultancy/Advisory Role; Agensys: Other: Institutional Research Support; Celgene: Other: Institutional Research Support; Seattle Genetics: Other: Consultancy/Advisory role, Institutional Research Support; Kura: Other: Institutional Research Support; Roche/Genentech: Other: Consultancy/Advisory Role, Institutional Research Support; Kyowa: Other: Consulting/Advisory Role; Regeneron Pharmaceuticals, Inc.: Other: Institutional Research Support; Autolus: Other: Consultancy/Advisory Role; AstraZeneca: Other: Consultancy/Advisory Role. Brown:Acerta / Astra-Zeneca: Membership on an entity's Board of Directors or advisory committees; Verastem: Consultancy, Research Funding; Pharmacyclics: Consultancy; Celgene: Consultancy; Genentech: Consultancy; TG Therapeutics: Consultancy; Morphosys: Membership on an entity's Board of Directors or advisory committees; Janssen: Consultancy; Abbvie: Consultancy; Gilead: Consultancy, Research Funding; Sun Pharmaceutical Industries: Research Funding; Sunesis: Consultancy; Loxo: Consultancy; Beigene: Membership on an entity's Board of Directors or advisory committees; Invectys: Membership on an entity's Board of Directors or advisory committees; Roche/Genentech: Consultancy; Boehringer: Consultancy. Allan:Genentech: Membership on an entity's Board of Directors or advisory committees; Verastem: Membership on an entity's Board of Directors or advisory committees; Sunesis: Membership on an entity's Board of Directors or advisory committees; AbbVie: Membership on an entity's Board of Directors or advisory committees; Acerta: Consultancy. Ansell:Bristol-Myers Squibb: Research Funding; Affimed: Research Funding; Regeneron: Research Funding; Merck & Co: Research Funding; LAM Therapeutics: Research Funding; Seattle Genetics: Research Funding; Trillium: Research Funding; Celldex: Research Funding; Takeda: Research Funding; Pfizer: Research Funding. O'Brien:Kite Pharma: Research Funding; Aptose Biosciences Inc.: Consultancy; Pharmacyclics: Consultancy, Research Funding; GlaxoSmithKline: Consultancy; Astellas: Consultancy; Sunesis: Consultancy, Research Funding; Alexion: Consultancy; Amgen: Consultancy; TG Therapeutics: Consultancy, Research Funding; Pfizer: Consultancy, Research Funding; Vaniam Group LLC: Consultancy; Regeneron: Research Funding; Janssen: Consultancy; Celgene: Consultancy; Abbvie: Consultancy; Acerta: Research Funding; Gilead: Consultancy, Research Funding. Chavez:Genentech: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Merck: Research Funding; Kite: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Janssen: Speakers Bureau; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees; Humanigen: Consultancy. Lowy:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Charnas:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Sternberg:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ambati:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Adriaens:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Ufkin:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Yan:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Li:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Navarro:Regeneron Pharmaceuticals, Inc.: Employment. Gasparini:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Jankovic:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Fiaschi:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Zhang:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Hamon:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Thurston:Regeneron Pharmaceuticals, Inc.: Employment, Equity Ownership. Topp:Amgen: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel, Research Funding; F. Hoffmann-La Roche Ltd: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer Ingelheim: Research Funding; Regeneron Pharmaceuticals, Inc.: Honoraria, Research Funding.

Purpose: Enoticumab (REGN421) is a fully human IgG1 monoclonal antibody that binds human Dll4 and disrupts Notch-mediated signaling. The main objectives of this trial were to determine the safety, dose-limiting toxicities (DLT), pharmacokinetics (PK), and recommended phase II dose (RP2D) of enoticumab. Experimental Design: Enoticumab was administered intravenously, with dose escalations from 0.25 to 4 mg/kg every 3 weeks (Q3W) and 0.75 to 3 mg/kg every 2 weeks (Q2W). Results: Of 53 enrolled patients, 31 patients were treated Q3W and 22 patients were treated Q2W. Two DLTs occurred: grade 3 nausea (0.5 mg/kg Q3W) and grade 3 abdominal pain (1 mg/kg Q2W). An MTD was not reached on either schedule. The most frequent adverse events (AE) were fatigue, nausea, vomiting, hypertension, headache, and anorexia. Six treatment-related serious AEs were reported in 4 patients: brain natriuretic peptide (BNP) increase (0.25 mg/kg Q3W, Gr1), troponin I increase (4 mg/kg Q3W, Gr3), right ventricular dysfunction and pulmonary hypertension (1.5 mg/kg Q2W, both Gr3), and left ventricular dysfunction and pulmonary hypertension (3 mg/kg Q2W, both Gr3). Enoticumab was characterized by nonlinear, target-mediated PK, and had a terminal half-life of 8 to 9 days. With multiple Q2W or Q3W dosing, accumulation was not observed. Antitumor activity included two partial responses (non–small cell lung cancer bronchoalveolar-type with a β-catenin mutation, and ovarian cancer) and 16 patients with stable disease (3> 6 months). Conclusions: Enoticumab was tolerated, with RP2D of 4 mg/kg Q3W and 3 mg/kg Q2W based on PK profile and clinical activity. Responses and SD were noted in ovarian cancer and other solid tumors. Clin Cancer Res; 21(12); 2695–703. ©2015 AACR.

Introduction: REGN1979 is a hinge-stabilized CD20xCD3bispecific full-length antibody (Ab) based on an IgG4isotype modified to reduce Fc binding. It is designed to bind T cells (via CD3) and CD20-expressing cells. Cross-linking results in specific, local T cell activation and engagement ofcytolytic functions, independent of T cell receptor mediated recognition. This mechanism of action (MOA) is distinct from approved anti-CD20 Abs, and may provide additional therapeutic benefit. This report describes safety and clinical outcomes in 25 patients (pts) treated with REGN1979. Methods: The study uses a 3+3 design to assess safety, pharmacokinetics (PK), pharmacodynamics (PD), and activity of REGN1979 inpts with NHL and CLL, in separate dose escalation cohorts. REGN1979 is administered IV over 1-4 hours, weekly (QW) for 4 doses followed by every 4 weeks (Q4W) for 5 doses. Each dose level (DL) consists of an initial starting dose followed by a higher (step-up) dose.Pts with either progressive disease (PD) after initial response or suboptimal initial response could be retreated. Results: As of clinical cut-off, 25pts had been enrolled and treated with REGN1979 at flat doses ranging from 0.03 - 3.0 mg: 20pts with NHLand 5pts with CLL. NHL subtypes included DLBCL (n=12), FL (n=6), and MCL (n=2). Allpts hada medianof3 (range 1-7) prior regimens, and received a median of 5 (range 2-9) doses of REGN1979. Sixpts remained on initial treatment, 3pts completed treatment, and 16pts discontinued treatment (14 for PD; 2 subject decision). Of 4pts who entered retreatment, 2pts remained ongoing. The most common treatment-related treatment-emergent AEs (TR-TEAEs) were pyrexia (56%), infusionrelated reaction (IRR) (40%), chills (36%), cytokine release syndrome (CRS) (28%), fatigue (24%), tachycardia (24%), hypomagnesaemia (20%) and hypotension (20%). Grade >= 3 TR-TEAEs occurred in 8 pts(32%): IRR (12%), CRS (8%), hypotension (8%), and pyrexia, tachycardia, dyspnea, anemia, hypoxia, hypertension, tachypnea, transaminases increased, and tumor pain each in 1 pt(4%). All were grade 3 with the exception of 1 ptwith grade 4 hypotension. There were no protocol-defined DLTs, nor grade 5 TEAE. No ptsdiscontinued REGN1979 due to TR-TEAE. IRR and CRS events were most commonly reported with the first administration of both initial and step-up dose with incidence and severity decreasing with increasing exposure. Tenptsreported at least one TR-SAE: CRS (24%), IRR (20%), and increased AST and tumor pain, each in 1pt(4%). Threeptswith aggressive lymphoma who discontinued REGN1979 due to PD died of their disease within 30 days of their last dose. Notably, modifications to pre-medication(s) and drug administration instructions have improved tolerability (fewer and less severe IRR/CRS). No clinically significant CNS TEAEs have been observed. CT-based (Cheson, 2007) anti-tumor activity was observed in 11 ptswith NHL: PR [n=4,median duration of 50d];SD [n=7, median duration of >196d]. The overall response rate (ORR) in NHL ptsacross DLs was 20%. In 2 highest dose levels, ORR was 27% (Fig 1). Of the 14pts evaluated by PET, 4pts had a partial metabolic response, withmedian duration of 244d perLugano Criteria. Twopts with CLL attained SD as best overall response. PK: REGN1979 concentrations in serum increased with increasing DL and were variable across pts. Variability was less at higher DLs and also decreased over time during therapy. At DLs tested, REGN1979 concentrations did not notably increase over time during treatment. PD/Cytokines: At the lowest dose tested, 0.03 mg, transient B-cell depletion was observed inpts with measurable circulating B cells.Samples from 12pts were available for cytokine analysis. Interim analysis indicates REGN1979 induces cytokine release as expected based on MOA. An increase in IL-6, IL-10 and to lesser extent IFN-γ was observed. The magnitude of cytokine response generally correlated with symptomatic IRR/CRS. Conclusion: REGN1979 demonstrated an acceptable safety profile at flat doses of 0.03 - 3.0 mg (< 1% of rituximab dose) inpts with NHL and CLL. Most TEAEs were associated with IRR/CRS, and were managed with supportive therapy and modification to REGN1979 administration. No clinically significant neurological toxicity was observed. Preliminary antitumor activity demonstrates increased activity at higher doses. Dose escalation and treatment schedule optimization continue. Disclosures Brown: Acetylon, Gilead: Research Funding; Celgene, Roche/Genentech, Gilead, Infinity, Janssen, Pharmacyclics, ProNai, Sun BioPharma: Consultancy. Arnason:Gilead: Consultancy. O'Brien:Pharmacyclics, LLC, an AbbVie Company: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria. Chavez:Janssen: Speakers Bureau. Ansell:BMS, Seattle Genetics, Merck, Celldex and Affimed: Research Funding. Topp:Amgen: Consultancy, Honoraria, Other: travel, Speakers Bureau; Roche: Honoraria, Other: travel; Boehringer: Consultancy, Other: Travel, Research Funding; Jazz: Consultancy; Pfizer: Consultancy, Other: Travel. Adriaens:Regeneron Pharmaceuticals Inc.: Employment, Equity Ownership. Ufkin:Regeneron Pharmaceuticals Inc.: Employment, Equity Ownership. Kostic:Regeneron Pharmaceuticals Inc.: Employment, Equity Ownership. Paccaly:Regeneron Pharmaceuticals Inc.: Employment, Equity Ownership. Gao:Regeneron Pharmaceuticals Inc: Employment, Equity Ownership. Trail:Regeneron Pharmaceuticals Inc: Employment, Equity Ownership. Lowy:Regeneron Pharmaceuticals Inc: Employment, Equity Ownership. Brownstein:Regeneron Pharmaceuticals Inc: Employment, Equity Ownership.

TPS3089 Background: REGN1979 is a human bispecific antibody based on an IgG4 isotype modified to reduce Fc binding, designed to bridge CD20-expressing cells to cytotoxic T-cells by binding to the C...

2522 Background: Nesvacumab (N) is a selective, human Ang-2 MAb, that potently blocks Ang2 signaling through the Tie2 receptor. Ziv-aflibercept (Z) is a recombinant human fusion protein and a decoy...

2540 Background: Nesvacumab (N) is an Ang2 selective, human MAb that potently blocks signaling through the Tie2 receptor, inhibiting tumor angiogenesis and growth. In mouse xenograft models of huma...

TPS2618 Background: REGN910 is a selective, fully human Angiopoietin-2 (ANG-2) MAb, which potently blocks signaling through the Tie2 receptor. Ziv-aflibercept (ZAFL) is a recombinant human fusion protein that acts as a decoy receptor for vascular endothelial growth factor (VEGF)-A, VEGF-B, and placental growth factor (PlGF), thereby preventing the interaction of these ligands with their receptors. In several mouse xenograft models, combination of the 2 anti-angiogenic compounds, REGN910 and ZAFL, demonstrated significantly enhanced tumor growth inhibition relative to either agent alone, suggesting that dual angiogenic blockade is worth exploring in cancer patients. Methods: This phase 1b study employs a standard 3+3 dose escalation design exploring 5 different combination treatment dose levels of REGN910 and ZAFL. Once the recommended phase 2 dose (RD) of the combination treatment is determined, additional patients will be enrolled in a safety expansion cohort, for a planned total enrollment of up to 40 patients. The primary study objectives are to evaluate the safety and determine the RD of the 2 drugs in combination when both are administered IV every 2 weeks in patients with advanced solid tumors. Secondary endpoints include characterization of the PK and potential immunogenicity of REGN910 and ZAFL when given in combination, evaluation of correlative PD biomarkers related to REGN910 and ZAFL, and identification of antitumor activity. Enrollment to cohorts 1 and 2 has been completed without DLT. Enrollment to cohort 3 opened in December 2012. Updated enrollment status will be presented. Reference: ClinicalTrials.gov Identifier: NCT01688960. Clinical trial information: NCT01688960.

2517 Background: REGN910 is a selective, fully human Ang2 MAb that potently blocks signaling through the Tie2 receptor regulating tumor angiogenesis and growth. In multiple mouse xenograft models of human solid tumors, REGN910 inhibits tumor growth. Methods: This first-in-human phase I study (3+3 design) explored the safety, recommended phase II dose (RP2D), pharmacokinetics (PK), pharmacodynamics (PD) and antitumor activity of REGN910 as a single agent. REGN910 was given IV at escalating doses. At RP2D, expansion cohorts were initiated to confirm safety and assess anti-tumor activity in about 20 patients (pts). Results: 37 pts [17M/20F; median age 57 (range 22-82); ECOG PS 0(9)/1(28)] were enrolled. Twenty-three (23) pts were enrolled in the dose escalation cohorts. No DLTs were reported, and a MTD was not reached. Most common G1/2 treatment-related adverse events (TRAEs) were fatigue 7(19%), peripheral edema 6(17%), diarrhea 5(14%), abdominal distension 4(11%), and decreased appetite 4(11%). There were no ≥ Grade 3 TRAEs. A confirmed sustained PR (16 wks) was observed in 1 pt with adrenocortical cancer treated at 1 mg/kg. SD (range 6.9-46.8 wks) was reported for 17 of 32 (53%) pts evaluable for efficacy. Fourteen pts received treatment >16 wks. One pt with thyroid cancer had SD for 46 wks, and 1 pt with hepatocellular cancer had SD for 16 wks with ≥50% decline in alpha-fetoprotein. Across all dose levels, REGN910 pharmacokinetics appeared linear and dose-proportional. The PK profile was characterized by an initial distribution and a single mono-exponential elimination phase. Total circulating serum Ang2 levels appeared saturated following treatment in all cohorts, indicating systemic target engagement at all doses tested. Conclusions: Administration of REGN910 in patients with advanced cancer is well tolerated, with generally mild and moderate TRAEs. Dose escalation is completed, and enrollment to the expansion cohorts continues. The safety profile supports combination with chemotherapy and/or other anti-angiogenic agents. Clinical trial information: NCT01271972.

2502 Background: Dll4, a Notch receptor ligand, may have a role in tumor angiogenesis and is an emerging anticancer target. REGN421 (R) is a fully human IgG1mAb that binds human Dll4 and disrupts Notch-mediated signaling. Methods: Primary objectives of the dose escalation (3+3 design) trial were to determine safety and a recommended phase II dose (RP2D) of R in patients (pts) with advanced cancer. R was given IV at doses of 0.25, 0.5, 1, 2 and 4mg/kg every 3 weeks (Q3W) or 0.75, 1, 1.5, and 3mg/kg every 2 weeks (Q2W). Secondary objectives were PK, immunogenicity, and antitumor activity. Results: 53 pts (M/F=22/31, ECOG 0/1=18/35) were enrolled; 31 pts were treated Q3W at doses of 0.25 - 4 mg/kg; 22 pts were treated Q2W at doses of 0.75 - 3 mg/kg. Two DLTs occurred: Grade 3 (Gr3) nausea (0.5mg/kg Q3W) and Gr3 abdominal pain (1 mg/kg Q2W). A maximum tolerated dose was not reached on either schedule. Grade 3/4 AEs occurred in 29 pts; nausea, abdominal pain, dyspnea, hypoxia, and hypertension (HTN) were reported in ≥ 5%. Most frequent treatment related AEs were fatigue (30%), headache (26%), HTN (26%), and nausea (15%). Six treatment related SAEs (all reversed off treatment) were reported in 4 patients: BNP increase (0.25mg/kg, Gr1), troponin I increase (4mg/kg, Gr3), right ventricular dysfunction (1.5mg/kg, Gr3), left ventricular dysfunction (3mg/kg, Gr3) and 2 events of pulmonary HTN (1.5mg/kg, Gr 3, and 3mg/kg Gr3). Laboratory abnormalities (≥ Gr3) were neutropenia (3) and anemia (2), and elevated ALP (7), ALT (3), bilirubin (3), AST (2), and decreased albumin (1). Anti-tumor activity included 2 PRs (NSCLC BAL-type with a beta-catenin mutation and ovarian cancer [OvCa]), and 16 pts with SD (3 pts had SD > 6 months). Two of 8 pts with OvCa had CA125 responses. R had non-linear target-mediated PK without accumulation. The half-life of R at 3mg/kg Q2W was 7 days. No immunogenicity was observed. Conclusions: REGN421 had an acceptable safety profile, and RP2Ds of 4mg/kg Q3W and 3mg/kg Q2W. Responses and prolonged SD were noted in OvCa pts and other solid tumors. Dose escalation has concluded and disease specific expansion cohorts are ongoing. Clinical trial information: NCT00871559.

TPS159 Background: Angiopoietin-2 (Ang2) is a secreted growth factor that functions as a critical regulator of angiogenesis, blood vessel maturation and integrity of the vascular endothelium. The e...