Copper-64: An Optimal Radionuclide for the Routine Preparation of PET Imaging Radiotracers from GMP-Lyophilized Gelatin-NOTA-Peptide Kits

Copper-64 is increasingly recognized for its advantages in positron emission tomography (PET) imaging and theranostic applications due to its favorable half-life, decay profile, and high spatial resolution. This research addresses the need for reliable, high-purity PET radiotracers by developing GMP-grade lyophilized kits for one-step preparation of 64Cu-NOTA-peptides using gelatin as a chelating agent for metallic impurities and NOTA for selective copper binding. The approach was applied to five peptide analogs formulated for fast 64Cu labeling: NOTA-iPSMA, NOTA-TOC, NOTA-iPD-L1, NOTA-iFAP, and NOTA-UBI 29–41, which were preclinically evaluated to enable the precise molecular imaging of cancer and infection. Each multidose kit included 0.5 μmol of the NOTA-peptide and 25 mg of gelatin, labeled with 925 MBq of 64Cu. The radiochemical purity of the 64Cu-NOTA-peptides exceeded 98% (mean 99.2% ± 0.3%) without the need for additional purification. The 64Cu-radiotracers remained stable for at least 24 h at room temperature and showed high stability in human serum. In preclinical studies, saturation-binding assays demonstrated that affinity (Kd) was less than 10 nM in all 64Cu-NOTA-peptides, with tumor-to-lung ratios ranging from 14 to 290 at 2 h post-injection and low liver uptake (2.95% ± 1.36% ID/g). The research demonstrated that these formulations, which include peptides specific to PSMA, SSTR2, PD-L1, FAP, and infection sites, offer excellent in vivo performance and high PET imaging quality in mice with induced tumors or infection sites. The findings support the use of gelatin-NOTA-peptide kits as a standardized and practical solution for producing 64Cu-labeled peptides, facilitating routine clinical PET imaging, and advancing personalized molecular diagnostics.