Abstract 1079: Anti-cancer efficacy of TH1902, a SORT1 docetaxel peptide-drug conjugate, against ovarian and endometrial cancers xenografts alone or in combination with carboplatin
Authors: Marsolais Christian , Demeule Michel , Charfi Cyndia , Currie Jean-Christophe , Larocque Alain , Zgheib Alain , Béliveau Richard , Annabi Borhane 
Published: June 2022

Abstract
Effective, safe chemotherapy treatments for gynecological cancers remain a daunting challenge. One strategy to achieve greater selectivity and better anticancer drug delivery into cancer cells is to conjugate cytotoxic agents to specific peptide ligands that selectively target receptors abundantly expressed on these cells. Increased expression of sortilin (SORT1), a scavenging receptor, has been shown to be highly expressed in many cancers, including ovarian and endometrial cancers. The peptide-drug conjugate TH1902 (a peptide which targets SORT1 and is bis-linked to two docetaxel molecules) was investigated to determine whether it could be efficacious against SORT1-positive ovarian (ES-2, A-2780 and SKOV-3) and endometrial (AN3-CA) cancer models. The Alexa488-fluorescent peptide used to generate TH1902 was transported into ES-2 and SKOV-3 cells by a process requiring clathrin-coated vesicles, and which was strongly diminished by siRNA-mediated SORT1 silencing or by competition with SORT1 ligands. In vitro, TH1902 enabled an increase in apoptosis of over 2-fold compared to that of unconjugated docetaxel. The effects of TH1902 administration were also examined in multiple subcutaneous xenograft tumor models (ES-2, SKOV-3, A-2780 or AN3-CA cells). Following two weeks treatment at equivalent docetaxel doses, the ES-2 xenograft sizes in mice treated with vehicle or with docetaxel were statistically indistinguishable but there was a significant decrease in tumor size by 78% for mice treated with TH1902. In SKOV-3 xenografts, treatment with either drug both stopped tumor growth and induced similar tumor regressions. In AN3-CA xenografts, treatments administered at equivalent docetaxel maximum tolerated dose (MTD) induced similar initial tumor regressions. However, TH1902-treated mice showed prolonged tumors regression whereas tumors started to regrow upon docetaxel treatment interruption. At one quarter of the docetaxel MTD, TH1902 significantly inhibited AN3-CA tumor growth whereas docetaxel had minimal effect (-73% vs -11%, respectively). Mice bearing A-2780 xenograft tumors were treated with TH1902, paclitaxel or docetaxel alone, as well as with each in combination with carboplatin. Comparison of the tumor sizes between the various treatments showed that TH1902 alone caused stronger A-2780 tumor growth inhibition than did either of the unconjugated taxanes or carboplatin. Moreover, TH1902 combined with carboplatin also demonstrated better efficacy than did either of the taxane-carboplatin combinations. Overall, the results indicate that TH1902 possesses an in vivo efficacy superior to those of docetaxel against ovarian and endometrial cancers in the animal models tested, and that TH1902 could be safely combined with carboplatin to reach optimal inhibition of tumor growth.
Citation Format: Christian Marsolais, Michel Demeule, Cyndia Charfi, Jean-Christophe Currie, Alain Larocque, Alain Zgheib, Richard Béliveau, Borhane Annabi. Anti-cancer efficacy of TH1902, a SORT1 docetaxel peptide-drug conjugate, against ovarian and endometrial cancers xenografts alone or in combination with carboplatin [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 1079.