Abstract 3210: Raptamer-drug conjugates as molecularly targeted cancer therapeutics

Abstract The use of aptamers as a therapeutic targeting moiety holds the promise of building on the success of antibody-drug conjugates (ADCs). While ADCs are an attractive modality, they face limitations, including limited penetration into solid tumors and a complicated production process for large-scale manufacturing. Aptamers have several potential advantages over antibodies as a targeting moiety including: (i) a smaller size that enables better tumor penetration; (ii) chemical synthesis which allows rapid scale-up and ease of incorporating modifications; (iii) a superior safety profile from lack of immunogenicity and (iv) room temperature stability. Therefore, the use of aptamers in conjunction with drugs (similar to ADCs) holds promise for development of targeted therapeutics. We have identified a novel therapeutic target for certain cancers (COF-01) using proteomics data and immunohistochemistry from patient-derived tumors. Both the COF-01 protein and related mRNA expression was shown to be significantly increased in non-small cell lung cancer, head and neck cancer and pancreatic cancer. Here, we present a new therapeutic approach that targets COF-01-positive cancer cells using next generation aptamer conjugates. We performed a cell- and protein-based selection using our proprietary bead-based combinatorial libraries to generate next-generation base-modified ssDNA aptamers (Raptamers) against COF-01. Binding affinities of the COF-01 Raptamer candidates were determined by concentration curves using biolayer interferometry. The dissociation constants for the COF-01 Raptamers ranged from 80 nM - 200 nM. COF-01-specific Raptamer-drug conjugates (Rap-DCs) were developed by conjugating the Raptamers to monomethyl auristatin E via a cleavable linker. In vitro efficacy data showed the COF-01 Rap-DC can selectively induce cytotoxicity in different types of COF-01-positive human cancer cells (A431, CAL 27, BxPC-3). There was a significant decrease in cell viability of COF-01-positive cells when compared to COF-01-negative control cells (IC50 values ranged from 5. 19 nM - 14. 11 nM). In vivo efficacy testing in a COF-01-postive cell-derived xenograft mouse model showed a significant decrease in tumor volume in animals treated with the COF-01 Rap-DC when compared to saline- and erlotinib-treated controls. This provides proof-of concept for the use of high-affinity Raptamers against novel molecular targets, such as COF-01. This platform can be used to develop Rap-DCs against emergent neo-antigens on cancer cells that have escaped chemotherapy. Citation Format: Stephanie P. Vega, Nancy E. Ward, Uksha Saini, Leniher Castan-Chibas, Garima Kaushik, Daniel Ciznadija, Dev Chatterjee, Michael J. Heffernan, Atul Varadhachary, Michael Ritchie. Raptamer-drug conjugates as molecularly targeted cancer therapeutics abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3210.