Abstract 5465: A novel CD3 VHH—based multi-specific T cell engager platform and multiple leads for gastric cancer and auto-immune disease

Abstract T cell engagers (TCEs) have recent approvals and great potential in the treatment of various diseases such as cancer and auto-immune diseases. The challenge of TCE in solid tumor is the therapeutic window due to limited tumor specific targets, and the CD3 arm requires fine tuning for specific targets and indications. The anti-CD3 used in current TCEs are monoclonal based and are limited in diversity of epitope and potency, which narrows the full potential of TCEs. VHHs being single domain, are ideal for bi- and multi-specific molecule design and engineering. We have identified anti-CD3 VHHs with diverse portfolio using in house llama, alpaca, and camel immunization with cells, protein and mRNA. We utilized VHHMAb® platform to capture full repertoire of the binders. The humanized anti-CD3 VHHs are diverse in epitope, affinity, T cells activation and in T cell dependent cytotoxicity. We have identified NHP cross binding anti-CD3 with great value for pre-clinical evaluation of TCE. We utilized in house developed AI-powered lead design for optimal TCE structure for best synapse between T cell and target cells. AI powered method was also used to design the TCEs for better developability attributes such as expression, solubility, aggregation. The TCEs, we have generated are with all single domain VHHs (anti-CD3 and TAA targeting) and are first of such kind. Colorectal cancer (CRC) has huge unmet clinical need as current treatments have limited clinical efficacy. We have identified targets which are differentially and restrictively expressed in the CRC in comparison to healthy tissues. Beside the tumor specific expression, the specific epitope on target have impact on effective T cell mediated killing of TCE. The membrane proximal domains are desired for TCE. With the VHHMAb® platform we have identified sets of VHHs which target different domains of two novel CRC targets. These VHHs are cross species (hu, NHP and mouse) binders that provide seamless path of pre-clinical to clinical development. With the binders of diverse epitopes on tumor antigen and various affinity and potency anti-CD3 VHH, we have generated TCEs that are functionally the best possible. Therapeutic efficacy, durability and safety are unmet medical needs in auto-immune diseases. For single target therapeutics, relapse due to antigen escape is one of the major problems. We have identified VHHs with NHP cross binding for multiple B cell targets of auto-immune diseases. Due to the single domain and modular nature of VHHs, we have generated TCEs with multi-targeting for better efficacy, durability and potentially overcome the relapse. Conclusion: We have generated diverse humanized anti-CD3 VHHs, different epitope and domain binding VHHs for target antigens. Due to modular nature of VHHs, we have generated multiple potentially FIC and or BIC TCE lead molecules which are composed of all VVHs arms, for CRC and auto-immune diseases. Citation Format: Toya N. Baral, Jia Yu, Weihong Wang, Huiyuan Tang, John Lee, Leo Ng, Jing Yu, Peng Bo, Yong Wang, Jiaguo Li, Xinhao Wang, Qijun Qian, Wenfeng Xu. A novel CD3 VHH—based multi-specific T cell engager platform and multiple leads for gastric cancer and auto-immune disease [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5465.