The fibroblast activation
protein (FAP) is heavily expressed in fibroblasts associated with the tumor microenvironment, while the prostate-specific membrane
antigen (PSMA) is expressed in the neovasculature of malignant angiogenic processes. Previously, we reported that [177Lu]
lutetium sesquioxide-iFAP/iPSMA nanoparticles ([177Lu]Lu-iFAP/iPSMA) inhibit HCT116
tumor progression in mice. Understanding the toxicity of [177Lu]Lu-iFAP/iPSMA in healthy tissues, as well as at the tissue and cellular level in pathological settings, is essential to demonstrate the nanosystem safety for treating patients. It is equally important to demonstrate that [177Lu]Lu-iFAP/iPSMA can be prepared under good manufacturing practices (GMP) with reproducible
pharmaceutical-grade quality characteristics. This research aimed to prepare [177Lu]Lu-iFAP/iPSMA under GMP-compliant
radiopharmaceutical processes and evaluate its toxicity in cell cultures and murine
biological systems under pathological environments. [177Lu]Lu2O3 nanoparticles were formulated as radiocolloidal solutions with FAP and PSMA inhibitor
ligands (iFAP and iPSMA),
sodium citrate, and
gelatin, followed by heating at 121 °C (103-kPa pressure) for 15 min. Three consecutive batches were manufactured. The final product was analyzed according to conventional pharmacopeial methods. The Lu content in the formulations was determined by X-ray fluorescence. [177Lu]Lu-iFAP/iPSMA performance in
cancer cells was evaluated in vitro by immunofluorescence. Histopathological toxicity in healthy and
tumor tissues was assessed in HCT116
tumor-bearing mice. Immunohistochemical assays were performed to corroborate FAP and PSMA
tumor expression. Acute genotoxicity was evaluated using the micronuclei assay. The results showed that the batches manufactured under GMP conditions were reproducible. Radiocolloidal solutions were sterile and free of bacterial
endotoxins, with radionuclidic and radiochemical purity greater than 99%. The
lutetium content was 0.10 ± 0.02 mg/mL (0.9 GBq/mg). Significant inhibition of cell proliferation in vitro and in
tumors was observed due to the accumulation of nanoparticles in the fibroblasts (FAP+) and neovasculature (PSMA+) of the tumor microenvironment. No histopathological damage was detected in healthy tissues. The data obtained in this research provide new evidence on the selective toxicity to malignant
tumors and the absence of histological changes in healthy tissues after
intravenous injection of [177Lu]Lu-iFAP/iPSMA in mammalian hosts. The easy preparation under GMP conditions and the toxicity features provide the added value needed for [177Lu]Lu-iFAP/iPSMA clinical translation.