Abstract Epidermal growth factor receptor (EGFR) is overexpressed or mutated in many patients with non-small cell lung cancer (NSCLC). Targeting EGFR mutation by tyrosine kinase inhibitors (TKIs) has significantly improved overall survival (OS) in patients with EGFR mutations. However, many patients experience tumor recurrence due to various resistance mechanisms. Therefore, there is an unmet medical need for new treatment strategies for patients with EGFR-positive NSCLC, regardless of EGFR mutation status. ABN202 is an antibody-cytokine fusion protein (ACFP) that serves as a platform technology compromising the IFN-β mutein (ABN102) fused to various antibodies for specific tumor targeting. In a previous study, we designed ABN202 (αEGFR) to comprise an EGFR targeting antibody (Cetuximab) and IFN-β mutein (ABN102) and we confirmed anti-cancer activities of ABN202 against EGFR-positive NSCLC. In this study, the direct cytotoxicity of ABN202 (αEGFR) was evaluated in human NSCLC cell lines with various driving mutations and EGFR expression levels. The indirect immune activation was tested in human peripheral blood mononuclear cells (PBMCs) and human IFNAR1/2 knock-in (KI) mice. The in vivo efficacy was evaluated in human NSCLC xenograft mouse models and human IFNAR1/2 KI mouse models. ABN202 (αEGFR) demonstrates potent anti-tumor activity through direct cytotoxicity and indirect immune activation in NSCLC, regardless of EGFR mutation status. Taken together, we suggest that ABN202 (αEGFR) is a promising drug candidate against NSCLC, regardless of EGFR mutation status. Citation Format: Hee Geon Park, Sung Hun Cho, Ha Yeon Park, Mi Gyoung Jo, Ji Hyun Park, Myeung Ryun Seo, Ji Hyun Kim, Sung Youl Hong, Kyoung Song, Chan Gyu Lee, Hae Min Jeong, Sae Hyung Lee, Na Young Kim, Jun Young Choi, Young Kee Shin. Potent anti-tumor activity of ABN202 (anti-EGFR antibody-interferon-beta mutein) through direct cytotoxicity and indirect immune activation against non-small cell lung cancer, regardless of EGFR mutation status [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4084.

Abstract Background Malignant pleural mesothelioma (MPM) is a rare and highly fatal cancer primarily induced by asbestos exposure. The 5-year overall survival rate for MPM patients is less than 20%. Before the FDA approval of the combination of immune checkpoint inhibitors (Nivolumab + Ipilimumab, CHECKMATE-743), chemotherapy was the only systemic therapy for MPM. However, the predominant histological type of MPM, epithelioid MPM, comprising approximately 70% of cases, showed limited clinical benefits from immune checkpoint inhibitors when compared to non-epithelioid histology. Consequently, there is an unmet medical need to develop a new anti-cancer drug specifically for the treatment of epithelioid MPM. In this study, we discovered that V-domain Ig suppressor of T cell activation (VISTA), an immune checkpoint protein, and Mesothelin (MSLN), a tumor differentiation antigen, are co-expressed in epithelioid MPM. Subsequently, we developed a biomarker-based anti-VISTA x MSLN bispecific antibody (BsAb) and anti-VISTA x MSLN BsAb-IFN-β mutein fusion protein (trispecific immunocytokine) for the treatment of epithelioid MPM. Method We designed and screened various structures of the anti-VISTA x MSLN BsAb. To produce the trispecific immunocytokine, we fused IFN-β mutein (R27T/C17S), which exhibits improved stability, productivity, and pharmacokinetic properties compare to recombinant IFN-β. The in vitro efficacy of the trispecific immunocytokine was tested in human MPM cell lines, and its in vivo efficacy was evaluated in a human MPM xenograft mouse model and a human IFNAR1/2 Knock-in (KI) mouse model. Results We demonstrated a strong positive correlation between the expression levels of VISTA and MSLN in epithelioid MPM. The Anti-VISTA x MSLN BsAb showed improved binding affinity and antibody-dependent cell cytotoxicity (ADCC) activity. The trispecific immunocytokine displays analogous biological activities to both Anti-VISTA x MSLN BsAb and IFN-β mutein. The trispecific immunocytokine exhibited potent in vivo and in vitro anti-cancer activities against epithelioid MPM preclinical models, operating through both direct cytotoxicity and indirect activation of immune cells. Conclusion The trispecific immunocytokine demonstrated robust in vitro and in vivo anti-cancer efficacy in the epithelioid MPM model. Our findings suggest that the trispecific immunocytoine is a promising drug candidate for epithelioid MPM. Citation Format: Hee Geon Park, Hyeon Ju Kim, Myeung Ryun Seo, Ji Eun Park, Tae Won Kim, Jeung Hoo Choi, Jay Park, Kyoung Song, Chan Gyu Lee, Hae Min Jeong, Jun Young Choi, Yeong Jeong Jeon, Yoon La Choi, Sung Youl Hong, Young Kee Shin. The anti-VISTA x MSLN bispecific antibody-interferon beta mutein fusion protein: A trispecific immunocytokine with potent therapeutic efficacy against malignant pleural mesothelioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4085.