Overcoming Therapy Resistance in Ovarian Cancer: From Molecular Mechanisms to Emerging Therapeutic Strategies

Background/Objectives: Epithelial ovarian cancer (EOC) remains a gynecologic malignancy with a poor prognosis, with a 5-year survival of approximately 29% in advanced-stage disease. Despite cytoreductive surgery and platinum- and taxane-based chemotherapy, most patients relapse within 2 years. Major therapeutic barriers include chemoresistance, molecular heterogeneity, and an immunosuppressive peritoneal microenvironment. This review summarizes emerging therapeutic strategies for EOC, their mechanisms of action, and their potential to overcome treatment resistance. Methods: PubMed/MEDLINE was searched for preclinical studies, phase I-III clinical trials, systematic reviews, and meta-analyses addressing novel ovarian cancer therapies and resistance mechanisms. Results: The review covers molecularly targeted therapies, immunotherapies, metabolic and epigenetic approaches, cellular and gene therapies, targeted drug-delivery systems, and locoregional and physical modalities. Strategies include PARP inhibitors, antiangiogenic agents, antibody-drug conjugates, pathway inhibitors, immune checkpoint inhibitors, cancer vaccines, adoptive cell therapies, metabolic and epigenetic modulators, CAR-T, CAR-NK, CRISPR/Cas9, HIPEC, PIPAC, ablation, photodynamic therapy, and sonodynamic therapy. Conclusions: The clinical maturity of these approaches varies substantially. PARP inhibitors, antiangiogenic agents, selected antibody-drug conjugates, MAPK-directed therapy in LGSOC, and HIPEC in selected settings have the strongest clinical support. Most immune combinations, metabolic and epigenetic therapies, adoptive cell therapies, gene-editing approaches, and novel delivery or physical modalities remain early clinical or predominantly preclinical. Progress will depend on biomarker-guided patient selection, reassessment of evolving resistance mechanisms, and rational treatment sequencing and combinations.