Abstract 6339: BCA101, a novel tumor-targeted bifunctional fusion antibody simultaneously inhibiting EGFR and TGF-β signaling with potential for durable tumor growth inhibition

Abstract Introduction: The suboptimal clinical efficacy EGFR-targeting therapeutics is attributed to both tumor intrinsic and tumor microenvironment (TME) derived acquired (extrinsic) resistance mechanisms. Intrinsic factors include activation of other receptor tyrosine kinases and key extrinsic resistance mechanism include the enhanced secretion of immunosuppressive factors such as IL-10 and TGF-β1. Here, we describe a first-in-class bifunctional monoclonal antibody fusion designed to simultaneously target EGFR and sequester TGF-β in the TME. Experimental Procedures: Functional activity of BCA101 was evaluated in multiple in vitro assays such as ELISA, inhibition of proliferation, antibody-dependent cellular toxicity, SMAD-reporter assay. Neutralization of TGF-β by BCA101 was demonstrated by epithelial-to-mesenchymal transition and tumor cell/immune cell co-culture assays. BCA101 tumor targeting was evaluated in a whole animal imaging study and efficacy studies were performed in nude xenograft models while combination studies with immune checkpoint inhibitors were performed in B16-EGFR syngeneic models. Results: BCA101 is an anti-EGFR IgG1 monoclonal antibody linked to an extracellular domain of human TGF-βRII. The TGF-β “trap” fused to light chain in BCA101 did not sterically interfere with its ability to bind EGFR, inhibit cell proliferation, or mediate antibody-dependent cellular cytotoxicity in vitro. BCA101 increased production of proinflammatory cytokines and key markers associated with T and NK cell activation, while suppressing VEGF secretion. Additionally, BCA101 inhibited differentiation of naïve CD4+ T cells to inducible T-regulatory (iTreg) cells when compared to cetuximab. In vivo, biodistribution studies showed that BCA101 localized to tumor tissues in xenograft mouse models, with comparable kinetics as cetuximab. TGF-β in tumors was neutralized to about 90% in animals dosed with 10 mg/kg of BCA101 compared to 54% in animals dosed with equimolar TGF-βRII-Fc. BCA101 had longer tumor tissue retention compared to cetuximab, further confirming improved tumor localization. In patient-derived xenograft mouse models of head and neck squamous cell carcinoma, BCA101 showed durable response post dose cessation as compared to cetuximab. In FaDu xenografts, BCA101 displayed early and durable response to cetuximab/cetuximab plus TGF-βRII-Fc combination. The combination of BCA101 and anti-PD1 antibody improved tumor inhibition in both B16-hEGFR expressing syngeneic mouse and in humanized HuNOG-EXL mice bearing human PC-3 xenograft models. Conclusion: These results support clinical development of BCA101, either as a monotherapy or in combination with immune checkpoint therapy. Citation Format: Srinivas Reddy Boreddy, Reshmi Nair, Prashant Kumar Pandey, Anshu Kuriakose, Arindam Banerjee, Chaitali Dey, Madhukara A R, Bhadravathi Marigowda Shivakumar, Hanumant Kulkarni, Milind Sagar, Prashantha Kumar M. V, Shiv Ram Krishn, Jaya Bhatnagar, Moni Abhram Kuriakose, Ram Bhupal Reddy, Amritha Suresh, Praveen Reddy Moole, Usha Bughani, Seng-Lai Tan, Pradip Nair, Rachel Salazar. BCA101, a novel tumor-targeted bifunctional fusion antibody simultaneously inhibiting EGFR and TGF-β signaling with potential for durable tumor growth inhibition. [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 6339.