Therapeutic Efficacy and Safety of Intraperitoneally Administered ²¹¹At-Labeled Gold Nanoparticles for Peritoneally...

Background/Objectives: Peritoneal dissemination of malignancies leads to poor prognoses, and no effective treatment currently exists. The difficulty of treating such malignancies is likely because systemically administered drugs cannot easily target malignant cells in the abdominal cavity. High intraperitoneal drug retention, non-toxicity towards normal tissues, and successful targeting of malignant cells are important for an effective therapy. The aim of this study was to evaluate an intraperitoneally administered astatine-labeled, integrin-targeted nanodrug, mPEG(Mn:350)-S-AuNP[²¹¹At]-c[RGDfK(C)] ([²¹¹At]AuNP@PEG/RGD), with respect to its kinetics, therapeutic efficacy, and safety. Methods: C6 rat glioma cells (10⁷), and BxPC3 (10⁷) and PANC-1 (10⁷) human pancreatic cancer cells were seeded intraperitoneally into nude mice, and [²¹¹At]AuNP@PEG/RGD (0.979 ± 0.194 MBq for C6 models (n = 3), 1.139 ± 0.035 MBq for BxPC3 models (n = 10), and 1.308 ± 0.039 MBq for PANC-1 models (n = 10) per mouse) or saline were intraperitoneally administered 4-7 days later. Cytotoxicity against malignant cells, pharmacokinetics after administration, therapeutic efficacy, and safety in abdominal organs were evaluated. Results: Intraperitoneally administered [²¹¹At]AuNP@PEG/RGD accumulated exclusively in the peritoneal cavity for a long period of time and showed minimal systemic diffusion through the blood. In the C6 model, the intraperitoneal tumor mass was significantly lower in the treated group compared with that of the controls (p = 0.05). For the BxPC3 (median survival time: control/treated = 41/65 days, p < 0.001) and PANC-1 (median survival time: control/treated = 19/35 days, p < 0.001) peritoneal dissemination models, survival analysis revealed that [²¹¹At]AuNP@PEG/RGD significantly prolonged overall survival. Although transient weight loss, leukopenia, and thrombocytopenia were observed at one week post-administration, a short recovery trend was evident thereafter. One month after administration, no abnormalities were found in hematological tests or histological analyses of intra-abdominal organs. Conclusions: The intraperitoneal administration of astatine-labeled integrin-targeted [²¹¹At]AuNP@PEG/RGD nanoparticles showed promising findings in terms of safety and efficacy for treating peritoneally disseminated malignant tumors.