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Simple Summary: In the United States, ovarian cancer (OCa) is the most lethal of all gynecologic malignancies. Survival rates for OCa with clinically localized disease have been enhanced by presently approved therapies; however, the majority (~90%) of patients with high-grade serous OCa (HGSOC) relapse with incurable metastases. In this investigation, we explored the hypothesis that the elevated basal endoplasmic reticulum stress (ERS) in OCa could be a significant vulnerability, offering a potential strategy to address OCa heterogeneity. We specifically tested the utility of targeting increased ERS in OCa cells by engaging the novel target lysosomal acid lipase A (LIPA) using the unique compound ERX-41. Our findings indicate that ERX-41 is a new targeted therapy that specifically targets the LIPA protein through a distinct mechanism of action. Furthermore, our results reveal that the binding of ERX-41 to LIPA leads to the induction of ERS and cell death in OCa cells. Ovarian cancer (OCa) is the most lethal form of gynecologic cancer, and the tumor heterogeneities at the molecular, cellular, and tissue levels fuel tumor resistance to standard therapies and pose a substantial clinical challenge. Here, we tested the hypothesis that the heightened basal endoplasmic reticulum stress (ERS) observed in OCa represents an exploitable vulnerability and may overcome tumor heterogeneity. Our recent studies identified LIPA as a novel target to induce ERS in cancer cells using the small molecule ERX-41. However, the role of LIPA and theutility of ERX-41 to treat OCa remain unknown. Expression analysis using the TNMplot web tool, TCGA data sets, and immunohistochemistry analysis using a tumor tissue array showed that LIPA is highly expressed in OCa tissues, compared to normal tissues. ERX-41 treatment significantly reduced the cell viability and colony formation ability and promoted the apoptosis of OCa cells. Mechanistic studies revealed a robust and consistent induction of ERS markers, including CHOP, elF2α, PERK, and ATF4, upon ERX-41 treatment. In xenograft and PDX studies, ERX-41 treatment resulted in a significant reduction in tumor growth. Collectively, our results suggest that ERX-41 is a novel therapeutic agent that targets the LIPA with a unique mechanism of ERS induction, which could be exploited to treat heterogeneity in OCa. [ABSTRACT FROM AUTHOR]