Abstract 5645: NW006-296, a novel ROR1 targeting ADC, demonstrates compelling anti-tumor efficacy in preclinical studies.

Abstract Background: Receptor tyrosine kinase-like orphan receptor 1 (ROR1) was found broadly expressed in both hematological malignancies and solid tumors whereas its expression was largely absent from normal blood lymphocytes and adult tissues, making it an attractive tumor target being explored clinically via mAb, bi-specific abs, CAR-T and ADC. While several ROR1-targeting ADCs with different MoA payloads are in development, we engineered NW006-296, a novel ADC comprising a humanized anti-ROR1 antibody site-specifically conjugated to monomethyl auristatin E (MMAE), aiming to achieve a homogeneous and stable therapeutic agent. NW006-296 was assessed in vitro and in vivo to evaluate its therapeutic potential. Methods: A library of ROR1-binding clones was screened for affinity, cell binding and internalization. Then the selected antibody is conjugated via cleavable linker to MMAE with drug-to-antibody ratio (DAR) of 4. The binding ability of the conjugates to human ROR1 is tested by enzyme-linked immunosorbent assay (ELISA). Finally, the anti-tumor efficacy of ROR1-targeting ADC is assessed in vitro through cell cytotoxicity assays and in vivo in multiple cell-line-derived xenograft (CDX) models. In detail, mice were treated with single (3 mg/kg, MDA-MB-231 and 5 mg/kg, U2932) and multiple (1 mg/kg or 3 mg/kg in HT-29; 3 mg/kg or 5 mg/kg in NAMALWA) doses of the ROR1-targeting ADC. Results: The lead antibody showed low nanomolar affinity to human ROR1 (KD=3.9 nM), strong binding to ROR1-expressing cells (EC50=0.4 nM, 0.3 nM, 0.5 nM for MDA-MB-231, HT-29 and NAMALWA, separately) and robust internalization in ROR1-expressing cells. Conjugation to the payload did not compromise binding of the antibody to human ROR1. NW006-296 showed potent cytotoxicity against the previous ROR1-expressing cells in vitro cell cytotoxicity assays. Furthermore, NW006-296 demonstrated significant dose-dependent anti-tumor activity, with tumor regression observed in both in vivo models used. When compared to the benchmark ADC (MK-2140), NW006-296 demonstrated superior anti-tumor activity in all CDX models investigated. Intriguingly, NW006-296 remained potent anti-tumor efficacy more than 40 days after the drug withdrawal in the U2932 CDX model, while the tumor re-growth in the benchmark ADC treating group regressed during therapy. Additionally, NW006-296 was well tolerated in mice as indicated preliminarily by no body weight loss occurring. Conclusions: NW006-296 has compelling anti-tumor efficacy and supports clinical development for ROR1-targeting ADCs across a broad spectrum of cancers. Further preclinical safety assessment, pharmacokinetics and IND-enabling studies are on-going with the goal to develop NW006-296 as a transformative therapeutic candidate for the treatment of colorectal cancer, breast cancer and hematological malignancies. Citation Format: Zhaoyu Gou, Liqian Zhou, Li Liu, Zikuo Zhang, Gang Liu, Yiran Wu, Dan Mi, Jiabao Liu, Yaolan Dai, Zhijian Li, Wenting Luo, Bin Liu, Desi Pan, Zhigang Guo. NW006-296, a novel ROR1 targeting ADC, demonstrates compelling anti-tumor efficacy in preclinical studies 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 5645.