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Objective: Detection and resection of all malignant lesions is pivotal in staging and cytoreductive surgery (CRS) of endometrial cancer (EC). Intraoperative EC detection could be enhanced using OTL-38, a fluorescent-labelled folate receptor-α (FRα) targeted imaging agent. The objectives of this study were to investigate which subgroups of high-risk EC patients express FRα and assess feasibility of intraoperative EC detection using OTL-38., Results: FRα expression on TMA was significantly correlated with tumor type ( p < 0.01). Eighty-two percent of serous and clear cell carcinomas showed FRα expression. Four patients were enrolled in the clinical study. Using fluorescence imaging all omental ( n = 3) and lymph node (LN) metastases ( n = 16) could be clearly identified, including one otherwise undetected omental metastasis. However, false-positive fluorescence was identified in 17/50 non-metastatic LNs, caused by OTL-38 targeting of FRβ, expressed by tumor-associated activated macrophages., Conclusions: This study describes high FRα expression in serous and clear cell EC and demonstrates the first experience of intraoperative FRα-targeted tumor detection in patients with these subtypes of EC. Although all metastases could be clearly identified using OTL-38, the role of tumor-associated macrophages should be further evaluated., Methods: Immunohistochemical (IHC) staining of FRα expression was performed on tissue micro arrays (TMA) of 116 patients with high-risk EC features. Patients with either serous or clear cell EC, planned for staging or CRS, were eligible for inclusion in the clinical study and received an intravenous dose of 0.0125 mg/kg OTL-38, 2-3 hours prior to surgery. Resected lesions, identified by standard-of-care and/or fluorescence imaging, were histopathologically assessed for FRα and tumor status., Competing Interests: CONFLICTS OF INTEREST The Centre for Human Drug Research (a not-for-profit foundation) and the Leiden University Medical Center received financial compensation, study drug and equipment for the execution of this study from On Target Laboratories LLC.

Incomplete resections and damage to critical structures increase morbidity and mortality of patients with cancer. Targeted intraoperative fluorescence imaging aids surgeons by providing real-time visualization of tumors and vital structures. This study evaluated the tumor-targeted zwitterionic near-infrared fluorescent peptide cRGD-ZW800-1 as tracer for intraoperative imaging of multiple cancer types. cRGD-ZW800-1 was validated in vitro on glioblastoma (U-87 MG) and colorectal (HT-29) cell lines. Subsequently, the tracer was tested in orthotopic mouse models with HT-29, breast (MCF-7), pancreatic (BxPC-3), and oral (OSC-19) tumors. Dose-ranging studies, including doses of 0.25, 1.0, 10, and 30 nmol, in xenograft tumor models suggest an optimal dose of 10 nmol, corresponding to a human equivalent dose of 63 μg/kg, and an optimal imaging window between 2 and 24 h post-injection. The mean half-life of cRGD-ZW800-1 in blood was 25 min. Biodistribution at 4 h showed the highest fluorescence signals in tumors and kidneys. In vitro and in vivo competition experiments showed significantly lower fluorescence signals when U-87 MG cells (minus 36%, p = 0.02) or HT-29 tumor bearing mice (TBR at 4 h 3.2 ± 0.5 vs 1.8 ± 0.4, p = 0.03) were simultaneously treated with unlabeled cRGD. cRGD-ZW800-1 visualized in vivo all colorectal, breast, pancreatic, and oral tumor xenografts in mice. Screening for off-target interactions, cRGD-ZW800-1 showed only inhibition of COX-2, likely due to binding of cRGD-ZW800-1 to integrin αVβ3. Due to its recognition of various integrins, which are expressed on malignant and neoangiogenic cells, it is expected that cRGD-ZW800-1 will provide a sensitive and generic tool to visualize cancer during surgery.