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Abstract 934: Identification of a GPC3 specific RNA aptamer and its use in cell specific targeted killing of GPC3 expressing tumors

Aptamers are short oligonucleotides that recognize specific molecular targets due to their folded three-dimensional structures. Aptamers are generated against a target molecule using a process called SELEX. This method allows the in vitro evolution of nucleic acid molecules with highly specific binding to target molecules. Here we describe a nuclease stable, fully modified 29OMethyl aptamer that recognizes Glypican-3 (GPC3) with high affinity and specificity. GPC3 is a heparan sulfate proteoglycan and cell surface oncofetal protein which is highly expressed on a variety of liver cancers, but not in healthy adult tissues. A conjugate comprising a GPC3 aptamer and Drug Maytansinoid (DM1), a membrane-permeable inhibitor of tubulin which can prevent cell division, is used to specifically target GPC3 expressing cells in vitro and in vivo. The aptamer-drug conjugate (GRX54) is capable of selectively killing a variety of GPC3 expressing liver cells in vitro and has significantly less toxicity in cells not expressing GPC3. The anti-tumor effect of GRX54 was tested in several tumor xenograft mouse models: Hep3B xenograft, Balb/c nude mice and NCI-H446 xenograft, Balb/c nude mice. GRX54 was administered at different doses via intraperitoneal injection (IP). For each group, mice were administered with vehicle or GRX54 once a day (QD) for 3, 5 or 7 days. Tumor weight and growth were measured. An anti-cancer drug Sorafenib Tosylate (30mg/kg, oral administration, once a day - Hep3B xenograft mouse model) or irinotecan (40mg/kg, i.p. twice a day for 4 days - NCI-H446 xenograft mouse model) were used as positive controls. GRX54 decreases Hep3B tumor volume in a Balb/c nude mouse xenograft model by ~30-45% depending on treatment schedule and NCI-H446 tumor volume by ~45-90% depending on treatment schedule. Together, our data show that GRX54 is a novel GPC3-targeting molecule capable of reducing tumor size with IP injection. Citation Format: Kristin M. Thompson, Christina McGuire, Jin Yuan, Aaron Ball, Justin Sonberg, Yuxun Wang, Shuhao Zhu. Identification of a GPC3 specific RNA aptamer and its use in cell specific targeted killing of GPC3 expressing tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 934.