Radiotheranostic Agent Cu-cyclam-RAFT-c(-RGDfK-) for Management of Peritoneal Metastasis in Ovarian Cancer.

Purpose: Ovarian cancer peritoneal metastases (OCPMs) are a pathophysiologically heterogeneous group of tumors that are rarely curable. αβ integrin (αβ) is overexpressed on tumoral neovessels and frequently on ovarian cancer cells. Here, using two clinically relevant αβ-positive OCPM mouse models, we studied the theranostic potential of an αβ-specific radiopeptide, Cu-cyclam-RAFT-c(-RGDfK-) (Cu-RaftRGD), and its intra- and intertumoral distribution in relation to the tumor microenvironment.

Experimental Design: αβ-expressing peritoneal and subcutaneous models of ovarian carcinoma (IGR-OV1 and NIH:OVCAR-3) were established in nude mice. Cu-RaftRGD was administered either intravenously or intraperitoneally. We performed intratumoral distribution (ITD) studies, PET/CT imaging and quantification, biodistribution assay and radiation dosimetry, and therapeutic efficacy and toxicity studies.

Results: Intraperitoneal administration was an efficient route for targeting Cu-RaftRGD to OCPMs with excellent tumor penetration. Using the fluorescence surrogate, Cy5.5-RaftRGD, in our unique high-resolution multifluorescence analysis, we found that the ITD of Cu-RaftRGD was spatially distinct from, but complementary to, that of hypoxia. Cu-RaftRGD-based PET enabled clear visualization of multiple OCPM deposits and ascites and biodistribution analysis demonstrated an inverse correlation between tumor uptake and tumor size (1.2-17.2 mm). Cu-RaftRGD at a radiotherapeutic dose (148 MBq/0.357 nmol) showed antitumor activities by inhibiting tumor cell proliferation and inducing apoptosis, with negligible toxicity.

Conclusions: Collectively, these results demonstrate the all-in-one potential of Cu-RaftRGD for imaging guided radiotherapy of OCPM by targeting both tumoral neovessels and cancerous cells. On the basis of the ITD finding, we propose that pairing αβ- and hypoxia-targeted radiotherapies could improve therapeutic efficacy by overcoming the heterogeneity of ITD encountered with single-agent treatments.