Development of a high-affinity anti-ROR1 variable region for broad anti-cancer immunotherapy.

Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an emerging target in cancer immunotherapy, recognized for its consistent and elevated expression across several epithelial tumors, including triple-negative breast cancer (TNBC). TNBC is an aggressive and difficult-to-treat cancer, with limited effective therapeutic options currently available. Therapeutic approaches centered on targeting ROR1 have therefore become increasingly popular, with ROR1 chimeric antigen receptor (CAR) T cells currently in clinical trials to treat TNBC patients. While ROR1-targeting therapies have shown promising preclinical results, single arm treatment has often shown low efficacy as well as off-target toxicity. Natural killer (NK) cell-based immunotherapies, such as antibody-dependent cell cytotoxicity-inducing monoclonal antibodies and CAR NK cells, have also been shown to induce cancer cell cytotoxicity; however, with less toxicity compared with CAR T cells. Here, we developed and characterized a phage-derived single-chain fragment variable (scFv) against a highly specific ROR1 region and generated scFv-derived chimeric monoclonal antibodies and anti-ROR1-CAR NK cells, which show anti-cancer efficacy against TNBC cells. Additionally, we found TGF-β inhibition using either small-molecule inhibitors or CRISPR-Cas9-edited NK cells could further enhance ROR1-targeting therapy persistence and efficacy in controlling TNBC tumor growth.