Abstract B098: A High-Throughput RNA-Based Screening Platform for Matching Patients to Antibody-Drug Conjugate Trials

Abstract Background: Antibody-drug conjugates (ADCs) represent a rapidly advancing therapeutic class in oncology, often requiring biomarker-based selection to identify eligible patients for clinical trials. Traditional IHC testing, while standard, is limited in throughput and multiplexing capacity. To address this, we developed and validated TARGET (Therapeutically Actionable RNA Guided Therapy) – a NanoString nCounter-based RNA expression platform designed for high-throughput pre-screening of FFPE tumor samples to support ADC trial enrollment. Methods: The assay was optimized and validated using 205 FFPE tumor samples. An initial cohort (n=95) was used to define RNA input requirements, establish quality control thresholds, and develop classification cutoffs. A second cohort (n=110) was used to evaluate classification performance. Expression thresholds for four ADC biomarkers (TACSTD2 (TROP2), FOLR1, NECTIN4, and ERBB2) were derived from RNA data and calibrated against IHC scores, with IHC 2+/3+ considered “high” and 0/1+ considered “low” protein expression. Biomarkers classified as “high” or “indeterminate” by RNA are advanced for confirmatory IHC testing; “low” expression markers are excluded from further testing. Assay robustness was assessed across operators, instruments, and reagent codeset lots. Results: The TARGET assay demonstrated strong concordance with IHC for all four biomarkers, with sensitivity ranging from 97.1% to 100% and specificity from 95.5% to 100%. Reproducibility across the full 402-gene panel was high (R2 > 0.98), and indeterminate rates remained low (6.6-13.2%). To support long-term clinical use, standardized calibration strategies were implemented to address lot-to-lot variation, using SKBR3 cell-line controls. Classification remained highly consistent across both stored and re-extracted RNA samples, with >95% concordance in 2x2 comparisons (screen vs. no-screen). High TROP2 expression was frequently observed across a wide range of epithelial malignancies, including breast, gastrointestinal, genitourinary, and gynecologic cancers. As expected, FOLR1 and NECTIN4 were commonly elevated in ovarian and urothelial carcinomas, respectively, but were also detected in other tumor types. High ERBB2 expression was observed in small subsets of cancers beyond breast and gastric origin. Conclusions: The TARGET assay enables reliable, scalable RNA-based pre-screening for ADC trials, facilitating efficient triage to IHC confirmation and expanding access to biomarker-matched therapies. Calibration strategies ensure consistent classification across assay lots, supporting sustainable clinical deployment. This approach is being integrated into a multicenter trial screening workflow and will be expanded to additional targets and tumor types. Citation Format: Hui Chen, Sujan Piya, Dzifa Yawa Duose, Amber Johnson, Francis A. San Lucas, Wei-Lien Wang, Jincy Veliyathu, Neelima Reddy, Bella Guerrouahen, Geeta Mantha, Hector Alvarez, Christina Bailey, Joseph Beechem, Erin Piazza, Burak Uzunparmak, Gabriela Raso, Sinchita Roy-Chowdhuri, Rajyalakshmi Luthra, Keyur P. Patel, Funda Meric-Bernstam. A High-Throughput RNA-Based Screening Platform for Matching Patients to Antibody-Drug Conjugate Trials [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2025 Oct 22-26; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2025;24(10 Suppl):Abstract nr B098.