Abstract 4547: TRO-02, a conditionally activated EGFR-targeting ADC incorporating TROCADTM and TROSIGTM platforms, shows enhanced tumor selectivity and potent efficacy

Abstract Epidermal growth factor receptor (EGFR) represents a validated therapeutic target across multiple solid tumor indications, including non-small cell lung cancer, head and neck squamous cell carcinoma, and colorectal cancer. However, EGFR expression in normal epithelial tissues, particularly skin, has limited the therapeutic window of EGFR-targeted therapies, often causing dose-limiting toxicities that impair clinical efficacy. To overcome this challenge, we developed TRO-02, a novel conditionally activated EGFR-targeting antibody-drug conjugate (ADC) that selectively activates in the tumor microenvironment while remaining masked in healthy tissues. TRO-02 is a DAR8-type ADC generated by conjugating a potent topoisomerase I inhibitor to panitumumab via a cleavable, stable, and hydrophilic TROSIGTM linker. Furthermore, it incorporates our proprietary TROCADTM platform, which provides dual functions: (1) masking the panitumumab to prevent EGFR binding until proteolytic cleavage by tumor-associated proteases, and (2) guiding the ADC to the tumors by targeting annexin A1, which is highly expressed on tumor vasculature and facilitates transcytosis. This dual mechanism allows TRO-02 achieve both specific activation within the tumor microenvironment and selective tumor delivery. In vitro, the masked TRO-02 exhibited approximately 100-fold weaker binding to EGFR than the activated ADC, confirming effective suppression of target engagement. The unmasked TRO-02 displayed sub-nanomolar cytotoxicity against EGFR-expressing tumor cells, whereas the masked form showed markedly reduced cytotoxicity, with 30- to 100-fold lower potency depending on the cell type compared with the unmasked form. In MDA-MB-231 xenograft model, a single dose of 0.3 and 1 mg/kg achieved 65% and 98 % tumor growth inhibition, respectively. Rat plasma stability studies showed high stability, with >85% of intact ADC remaining after 7 days of incubation. Furthermore, pharmacokinetic analysis in rats demonstrated favorable PK properties (t1/2 = 4.47 days, AUC = 163.52 day·μg/mL, CL = 25.05 mL/day/kg, Vd = 0.08 L/kg at 4 mg/kg), indicating high in vivo stability and low clearance. Collectively, these findings demonstrate that TRO-02 is a conditionally activated EGFR-targeting ADC with improved therapeutic index, achieving potent antitumor efficacy while minimizing on-target/off-tumor toxicity. Citation Format: Young Hun Lee, Do Hyeon Kim, Eun Young Shim, Eunhyun Choi, Jong Un Cho, Myoungki Baek, Sung Ho Woo. TRO-02, a conditionally activated EGFR-targeting ADC incorporating TROCADTM and TROSIGTM platforms, shows enhanced tumor selectivity and potent efficacy [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 4547.