Abstract 3083: YT-DP: A glyco-conjugation-based dual-payloads ADC platform

Abstract Dual-payloads antibody-drug conjugates (ADCs) represent a promising next-generation modality to enhance antitumor efficacy, achieve synergistic effects, and overcome tumor heterogeneity and therapeutic resistance. However, their development faces several key challenges, including: (i) identifying payload combinations that maintain efficacy within a shared safety window without single-agent dominance; (ii) achieving precise and efficient assembly of distinct payloads into antibodies with controlled drug-to-antibody ratios (DARs); and (iii) ensuring robust stability, in vivo efficacy, and favorable safety profiles. To address these challenges, we developed YT-DP, a glyco-conjugation-based dual-payloads ADC platform that enables the incorporation of two distinct mechanism-of-action (MOA) payloads into a single antibody molecule through a one-step glyco-conjugation strategy. This system allows flexible DAR configurations (e.g., DAR 2+2 or DAR 2+4). The YT-DP platform integrates our proprietary cleavable-linker-topoisomerase I inhibitor payload (CLTp) technology (YT-CLTp) with a microtubule inhibitor (MTI) via the YTConju glyco-conjugation system. The YT-CLTp series comprises tunable payload candidates with adjustable target and bystander killing activities, demonstrating superior anti-tumor potency compared with “GGFG-Dxd” in multiple CDX models when conjugated to antibodies. We generated trastuzumab-based dual-payloads ADCs (Tras-DPs) containing an MTI and distinct CLTps at different DARs (DAR 2+2 and DAR 2+4). Tras-DPs exhibited high homogeneity, excellent thermal and plasma stability, and potent synergistic antitumor activity with strong by-stander effects. Notably, Tras-DPs demonstrated markedly superior antitumor activity compared with DS-8201, as well as the corresponding single-payload ADCs or their combinations, in CDX models. In addition, the dual-payloads ADCs showed favorable pharmacokinetic (PK) properties and safety profiles in rat studies. In summary, the YT-DP platform provides a robust and versatile strategy for constructing homogeneous, stable, and synergistic dual-payloads ADCs with tunable DARs. Its broad compatibility with various antibody formats, including Fc-containing bispecific antibodies, underscores its potential to enable next-generation ADCs with an enhanced therapeutic index. Citation Format: Yi Yang,Zhentao Song,Rui Yu,Jiangping Hu,Zhouyang Qian,Xinyue He,Guoli Yang,Ji Chen,Juntao Yu. YT-DP: A glyco-conjugation-based dual-payloads ADC platform [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3083.