Abstract 1077: Stability and safety evaluation of ELU001, a targeted C’Dot drug conjugate for the potential treatment of folate receptor alpha-overexpressing cancers

Abstract While several antibody-drug conjugates (ADCs) have shown efficacy in the treatment of solid tumors ADCs remain limited in their therapeutic efficacy due to long circulatory half-life and limited tumor penetration. Ultra-small (sub-10nm) C’Dot-drug-conjugates (CDCs) directly address this, exhibiting deep penetration and retention in solid tumor models, with limited systemic exposure following rapid renal clearance. CDCs can also achieve greater potency by delivering over 10x more payload and by binding to tumor cells with a higher avidity allowing effective killing of tumors with broader range of moderate to high expression of target antigens. ELU001 is a CDC that targets folate receptor alpha (FRα) overexpressing tumors via folic acid moieties on its surface and delivers an average of 21 exatecan topoisomerase-1 inhibitor molecules as its payload. FRα is overexpressed on a variety of tumors including ovarian, endometrial, triple negative breast and non-small cell lung, but is minimally expressed on normal tissues making it an attractive tumor-associated antigen for targeted drug delivery. ELU001 is highly stable in plasma and elicits antitumor efficacy in a variety of cell line and PDX-derived tumor models both in vitro and in vivo. In 15-day repeat dose toxicology and toxicokinetic studies performed in Wistar Han rats and Beagle dogs, ELU001 was well tolerated at up to 0.87 mg/kg/day in rats and 0.174 mg/kg/day in dogs based upon conjugated exatecan concentration when administered on a QWx3 schedule via a 1-hour infusion. Observed dose-related toxicities for both species were limited to the bone marrow and GI tract - the same organs as those observed when free payload (exatecan) was administered suggesting that the delivery of exatecan conjugated to the CDC did not broaden the tissue toxicity profile. Observed toxicities were recovered or substantially reduced by the end of a two-week recovery period. No drug-related hepatic, renal, pulmonary or ocular toxicities were observed and there were no drug-related deaths in the repeat dose toxicity study. TK parameters, estimated in the 15-day GLP studies revealed similar plasma exposure values in males and females for ELU001, Total Exatecan (conjugated and released) and Released Exatecan for rats and dogs, respectively. ELU001 exhibited an average circulatory half-life ranging from approximately 15 to 20 hrs in rats and 24 to 29 hrs in dogs with no accumulation of ELU001, Total Exatecan or Free Exatecan observed from day 1 to day 15. Based upon AUC0-last (hr*ng/ml) released payload levels in the circulation were less than approximately 0.3% and 0.1% of the total payload levels in the rat and the dog respectively. No ELU001 anti-drug antibodies were induced in either species. In summary, ELU001 has a favorable nonclinical safety/TK profile and is currently under evaluation in a clinical safety study - NCT05001282. Citation Format: Gregory P. Adams, Kai Ma, Feng Chen, Marion Scocca, Aranapakam Venkatesan, Cathy Reddick, Mary Hilgart, Thomas Gardinier, Fei Wu, Melik Turker, Peiming Chen, Tin Khor, Vaibhav Patel, Eliel Bayever. Stability and safety evaluation of ELU001, a targeted C’Dot drug conjugate for the potential treatment of folate receptor alpha-overexpressing cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1077.