Preclinical Study of the PSMA-Targeting Fluorescent and PET Imaging Tracer [⁶⁸Ga]Ga-NYM036 for Prostate Cancer...

Prostate-specific membrane antigen (PSMA) is a biomarker and molecular imaging target with the potential for the development and application of theranostic radiopharmaceuticals. Our study designed and developed PSMA-targeted small-molecule structures with diagnostic and therapeutic significance and screened out a precursor molecular structure NYM036 with PET diagnostic and fluorescence imaging potential and mainly explored the PET imaging biodistribution and fluorescence imaging of [⁶⁸Ga]Ga-NYM036 in prostate cancer model mice. After design and optimization, a small-molecule structure (named NYM036) characterized with fluorescence imaging and radionuclide-labeling functions was obtained. In the LNcaP prostate cancer mouse model, the preclinical targeted imaging efficacy and biodistribution of [⁶⁸Ga]Ga-NYM036 were studied using microPET/CT imaging. The feasibility of using the fluorescence imaging function of [⁶⁸Ga]Ga-NYM036 for tumor boundary differentiation and surgical navigation was verified through live fluorescence imaging and simulation of the surgical resection of prostate cancer. MicroPET/CT imaging in LNcaP tumor-bearing mice showed that [⁶⁸Ga]Ga-NYM036 had quite a low accumulation in nontarget organs (except for kidneys) and a high uptake in tumors. Blocked with 10-fold of the mass dose of NYM036, the radioactive uptake in tumors decreased significantly (%ID/g-mean, from 20.91 ± 3.11 to 4.12 ± 0.54, P < 0.001), with the tumor-to-muscle ratio decreased from 16.85 ± 5.09 to 3.57 ± 0.66, but the radiouptakes in other organs had no obvious change. [⁶⁸Ga]Ga-NYM036 had a high and fast biodistribution in tumors, and the high target uptake lasted at least for 3 h after injection (%ID/g-mean value: 1 h, 22.05 ± 3.72; 3 h, 25.11 ± 4.87). The acute toxicity experiments conducted in ICR mice showed the good safety of [⁶⁸Ga]Ga-NYM036. Fluorescence imaging and tumor resection surgery with [⁶⁸Ga]Ga-NYM036 in LNcaP tumor-bearing mice displayed that the nuclide-labeled PSMA-targeting radiotracer [⁶⁸Ga]Ga-NYM036, which was coupled via a covalent bond with the Cy7 fluorescent dye, has a significant imaging effect and a good surgical navigation function for tumor tissues in the LNcaP prostate cancer mouse model. The PET imaging analysis results of radioactive uptakes for tumors and multiple organ tissues showed that [⁶⁸Ga]Ga-NYM036 has a good targeting capability for tumors, a low uptake in nontarget organs, and a good PET imaging efficiency in prostate cancer models. [⁶⁸Ga]Ga-NYM036 PET imaging may be applied to diagnosis and preoperative planning, and its fluorescence imaging function can be used in intraoperative navigation and postoperative efficacy evaluation, helping to achieve precise clearance surgery and subsequent treatment of prostate cancer.