Abstract 5100: Combination of κλ bispecific antibodies targeting innate (CEAxCD47, NILK-2401) and adaptive immunity (CEAxCD3, NILK-2301 and CEAxCD28, NILK-3301) for next generation immunotherapy of CEA-expressing cancers
Authors: Seckinger Anja , Nouveau Lise , Majocchi Sara , Moine Valéry , Buatois Vanessa , Daubeuf Bruno , Gueneau Franck , Ravn Ulla , Masternak Krzysztof , Poitevin Yves , Rousset Emeline , Magistrelli Giovanni , Malinge Pauline , Shang Limin , Fischer Nicolas , Strein Klaus , Ferlin Walter , Hose Dirk 
Published: April 2023

Abstract
Background: The CEAxCD3 bispecific antibody (bsAb) NILK-2301 couples CEA (CEACAM5) on cancer cells and CD3 on T-cells inducing T-cell activation (signal 1) and tumor cell killing (TDCC). T-cell activation can be boosted by CEA-targeted CD28-costimulation (NILK-3301; signal 2). NILK-2401, carrying a fully effective IgG1 Fc, induces antibody-dependent phagocytosis (ADCP) and antibody-dependent cytotoxicity (ADCC) of tumor cells by co-targeting CEA and the innate immune checkpoint CD47 (“don’t eat me” signal). We present here next generation immunotherapy to overcome limited single class activity in CEA-expressing solid cancers.
Methods: BsAbs were generated using LCB’s fully human κλ body platform. TDCC, ADCP, and ADCC with human PBMC or monocyte-derived macrophages were assessed using CEA+ colorectal (n=3), lung (n=2), and gastric (n=2) cancer lines. Combination activity of NILK-2401 + NILK-2301 (± NILK-3301) was assessed by flow cytometry. In vivo activity was tested in xenograft NOG or NSG/human PMBC-, HIS-, and hSIRPα/hCD47/hCD3/hCD28 transgenic mice. Safety data include binding to other CEACAMs, cytokine release in whole blood, erythrophagocytosis, platelet activation, exclusion of superagonism (NILK-3301), as well as PK- and tolerability in cynomolgus monkeys and Tg32-mice.
Results: NILK-2301 induced dose-dependent killing of all tested cell lines, which was also visualized by live cell imaging. Combination of NILK-2301 (1 nM) + NILK-3301 vs. NILK-2301 alone (10 nM) increased TDCC (3-8-fold), T-cell activation (CD25, CD69, HLA-DR), cytokine secretion (interferon-γ, granzyme B, perforin), and CD4+/CD8+ T-cell proliferation. NILK-2401 blocked CD47-SIRPα interaction and induced ADCP/ADCC-mediated elimination of all cell lines. NILK-2301 + NILK-2401 treatment increased maximum activity (Emax) and reduced necessary dose of the T-cell bsAb to reach Emax. E.g., Emax of 30% killing (NILK-2301 alone) was increased in combination with NILK-2401 at 0.1/1/10 µg/mL to 40%, 80%, and 80%. In vivo, NILK-2301 (10 mg/kg IV, BIW) decreased tumor progression. NILK-2301/-3301 combination induced tumor regression in 8/8 mice. NILK-2401 delayed tumor growth vs. mean of control in 100% (15/15) of mice and prevented establishment of detectable tumors (&gt;50mm3) in 53% (8/15). Results of double and quadruple transgenic mice, including triple bsAb combinations, will be presented at the meeting. No relevant safety signals were detected.
Conclusions: NILK-2301 and NILK-2401 are active as single agents. Addition of NILK-2401 or NILK-3301 to NILK-2301 significantly increases activity, already at 10 -100x lower CEAxCD3 doses. GMP drug substance has been produced for NILK-2301 and NILK-2401. Generation of the clonal cell line for NILK-3301 clinical material production is ongoing.
Citation Format: Anja Seckinger, Lise Nouveau, Sara Majocchi, Valéry Moine, Vanessa Buatois, Bruno Daubeuf, Franck Gueneau, Ulla Ravn, Krzysztof Masternak, Yves Poitevin, Emeline Rousset, Giovanni Magistrelli, Pauline Malinge, Limin Shang, Nicolas Fischer, Klaus Strein, Walter Ferlin, Dirk Hose. Combination of κλ bispecific antibodies targeting innate (CEAxCD47, NILK-2401) and adaptive immunity (CEAxCD3, NILK-2301 and CEAxCD28, NILK-3301) for next generation immunotherapy of CEA-expressing cancers. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5100.