Abstract 3756: Optimization of the LIPA targeting agent for the treatment of ovarian cancer

Abstract Background: Ovarian cancer (OCa) is the most lethal form of gynecologic cancer in the United States, with a five-year survival rate below 20%. Tumor resistance to chemotherapy and poor clinical outcomes are driven by intratumoral and intertumoral heterogeneity. There is a critical need for novel therapies to overcome these challenges. Recent findings indicate that elevated basal levels of endoplasmic reticulum stress (ERS) in OCa represent a significant vulnerability and identified LIPA as a novel target for inducing ERS in cancer cells with the oligobenzamide ERX-41. In this study, we have synthesized and tested several derivatives of ERX-41 for lead optimization, established ERX-208 as the optimized lead, validated its mechanism of action. Methods: ERX-208 activity was validated in 17 OCa cell lines, representing five major histological subtypes. Mechanistic studies involved Western blotting, IHC, RNA-seq, mutagenesis, docking, and CRISPR/Cas9 knockout. PK and toxicology studies were conducted in C57BL/6 mice, and preclinical assessments in cell line-derived xenograft (CDX), patient-derived xenograft (PDX), and patient-derived explant (PDE) models. Results: After the screening of a curated oligobenzamide library derived from ERX-41, ERX-208 was identified as a more potent analog, by virtue of its ability to potently reduce the cell viability and promoting ERS in OCa cells. ERX-208 reduced the viability of 17 different OCa cell lines, with an IC50 range of 50-100 nM, in comparison to ERX-41, which showed an IC50 around 500 nM. Importantly, ERX-208 had minimal impact on the viability of normal ovarian surface epithelial cells, indicating a selective action against cancerous cells. Treatment with ERX-208 resulted in a significant decrease in colony formation and induced apoptosis. Mechanistic studies, including RNA-seq, Western blot analysis, TEM, and RT-qPCR revealed the activation of ERS as early as five hours post-treatment, suggesting a rapid onset of action. These studies also identified LIPA as a potential therapeutic target, with the activity of ERX-208 being notably diminished when LIPA was knocked out or when specific amino acids involved in ERX-208 interaction were mutated, as determined through docking studies. Further pre-clinical studies, including dose-range, MTD and PK assessments, indicated that a 10 mg/kg was the minimal amount required to achieve 50% efficacy without causing toxicity. ERX-208 treatment effectively reduced tumor growth in OCa CDXs, PDXs, and PDEs models. IHC analyses revealed a marked decrease in tumor cell proliferation, as evidenced by Ki67 expression, and demonstrated an increase in ERS markers, including GRP78 and p-PERK. Conclusions: These findings suggest that ERX-208 is a promising candidate as a therapeutic agent in OCa treatment. Since a related analog of ERX-208, ERX-315 is in clinical trials, these data strongly support the evaluation of ERX-208 in patients with OCa. Citation Format: Suryavathi Viswanadhapalli, Tae-Kyung Lee, Kara Kassees, Gaurav Sharma, Rahul Gopalam, Karla Parra, Tanner Reese, Michael Hsieh, Uday P. Pratap, Xue Yang, Behnam Ebrahimi, Chia-Yuan Chen, Scott Elmore, Henry Neal, Christian Cervantes, Zhenming Xu, Edward Kost, Gangadhara Reddy Sareddy, Rajeshwar Rao TekmalJung-Mo Ahn, Ganesh V. Raj, Ratna K. Vadlamudi. Optimization of the LIPA targeting agent for the treatment of ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 3756.