89Zr-DFO-Mirvetuximab PET/CT Imaging for Companion Diagnosis and Response Evaluation in Ovarian Cancer

Epithelial ovarian cancer (EOC) is the fifth leading cause of cancer-related death in women, with approximately 320,000 new cases and 200,000 deaths annually worldwide, and its incidence is rising. Current treatment mainly relies on surgery, chemotherapy, and radiotherapy, but EOC frequently develops platinum resistance and recurrence. Mirvetuximab soravtansine, a folate receptor alpha (FRα)-targeting antibody-drug conjugate (ADC), was approved by the FDA in 2024 for FRα-positive, platinum-resistant EOC. However, it carries significant toxicities (ocular, interstitial lung disease, peripheral neuropathy) and a modest objective response rate of 33%, with rapid acquired resistance, underscoring the need for patient selection and response prediction via targeted imaging. FRα, a GPI-anchored cell-surface glycoprotein encoded by FOLR1, is minimally expressed in normal adult tissues but overexpressed in various epithelial tumors, including ovarian cancer. Its overexpression promotes invasion, metastasis, and potentially drug resistance, making it a promising theranostic target. While ¹⁸F-FDG PET/CT is widely used, it has limitations in detecting low-activity or small lesions and shows suboptimal sensitivity/specificity for nodal metastases. Radiolabeled folate probes (e.g., ⁹⁹ᵐTc-EC20) have demonstrated excellent FRα-targeting and clinical utility in selecting patients for FRα-directed therapies. Our team has developed ⁸⁹Zr-DFO-Mirvetuximab by conjugating the anti-FRα monoclonal antibody with the chelator p-isothiocyanatobenzyl-desferrioxamine B and radiolabeling with ⁸⁹Zr. Preclinically, this probe exhibited favorable stability, safety, and specific targeting of FRα-high tumors in xenograft models. Building on these results, we plan a clinical study enrolling 20 patients with newly diagnosed stage IV or first-recurrent EOC, who will undergo both ⁸⁹Zr-DFO-Mirvetuximab PET/CT and ¹⁸F-FDG PET/CT. The study aims to correlate radiotracer uptake with FRα expression and to demo