Emerging Clinical Activity of REGN1979, an Anti-CD20 x Anti-CD3 Bispecific Antibody, in Patients with Relapsed/Refractory Follicular Lymphoma (FL), Diffuse Large B-Cell Lymphoma (DLBCL), and Other B-Cell Non-Hodgkin Lymphoma (B-NHL) Subtypes (2018)

Abstract 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 &amp; 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.