Despite significant advances in nuclear medicine for diagnosing and treating prostate cancer (PCa), research into new ligands with increasingly better biological properties is still ongoing. Prostate-specific membrane antigen (PSMA) ligands show great potential as radioisotope carriers for the diagnosis and therapy of patients with metastatic PCa. PSMA is expressed in most types of prostate cancer, and its expression is increased in poorly differentiated, metastatic, and hormone-refractory cancers; therefore, it may be a valuable target for the development of radiopharmaceuticals and radioligands, such as urea PSMA inhibitors, for the precise diagnosis, staging, and treatment of prostate cancer. Four developed PSMA-HYNIC inhibitors for technetium-99m labeling and subsequent diagnosis were subjected to preclinical in vitro and in vivo studies to evaluate and compare their diagnostic properties. Among the studied compounds, the PSMA-T4 (Glu-CO-Lys-L-Trp-4-Amc-HYNIC) inhibitor showed the best biological properties for the diagnosis of PCa metastases. [^99mTc]Tc-PSMA-T4 also showed effectiveness in single-photon emission computed tomography (SPECT) studies in humans, and soon, its usefulness will be extensively evaluated in phase 2/3 clinical trials.

There has been considerable interest in developing a monoclonal antibody (mAb) against-CD-20 (for example, Rituximab) modified by bifunctional chelating agents (BCA) for non-Hodgkin's lymphoma radioimmunotherapy. Therefore, many researchers have modified this monoclonal antibody by attaching different BCA moieties and evaluated their biological activities in terms of in vitro study and in vivo study in healthy and tumor xenografted rodents. This mini-perspective reviews the in vitro studies, the immunoreactivity and physiological distribution studies: organ-to-blood and the tumor-to-organ ratio of conjugates with different numbers of chelators per mAb. We set up a null hypothesis that states there is no statistical significance between the biological activity of monoclonal antibody (Rituximab) and the number of conjugated bifunctional chelators. Overall, we have concluded that there is no strong evidence for this hypothesis. However, the literature data should be questioned due to the potential lack of uniform study methodology.

Despite the tremendous development of oncology, prostate cancer remains a debilitating malignancy. One of the most promising approaches to addressing this issue is to exploit the advancements of nanomedicine in combination with well-established nuclear medicine and radiotherapy. Following this idea, we have developed a radioisotope nanocarrier platform of electron-beam-synthesized nanogels based on poly(acrylic acid). We have developed a functionalization protocol, showing the very high (>97%) efficiency of the conjugation in targeting a ligand–bombesin derivative. This engineered peptide can bind gastrin-releasing peptide receptors overexpressed in prostate cancer cells; moreover, it bears a radioisotope-chelating moiety. Our nanoplatform exhibits very promising performance in vitro; the radiolabeled nanocarriers maintained high radiochemical purity of >90% in both the labeling buffer and human serum for up to 14 days. The application of the targeted nanocarrier allowed also effective and specific uptake in PC-3 prostate cancer cells, up to almost 30% after 4 h, which is a statistically significant improvement in comparison to carrier-free radiolabeled peptides. Although our system requires further studies for more promising results in vivo, our study represents a vital advancement in radionanomedicine—one of many steps that will lead to effective therapy for castration-resistant prostate cancer.

Broad availability and cost-effectiveness of ⁹⁹Mo/^99mTc generators worldwide support the use, and thus the development, of novel ^99mTc-labelled radiopharmaceuticals. In recent years, preclinical and clinical developments for neuroendocrine neoplasms patient management focused on somatostatin receptor subtype 2 (SST₂) antagonists, mainly due to their superiority in SST₂-tumour targeting and improved diagnostic sensitivity over agonists. The goal of this work was to provide a reliable method for facile preparation of a ^99mTc-labelled SST₂ antagonist, [^99mTc]Tc-TECANT-1, in a hospital radiopharmacy setting, suitable for a multi-centre clinical trial. To ensure successful and reproducible on-site preparation of the radiopharmaceutical for human use shortly before administration, a freeze-dried three-vial kit was developed. The final composition of the kit was established based on the radiolabelling results obtained during the optimisation process, in which variables such as precursor content, pH and buffer, as well as kit formulations, were tested. Finally, the prepared GMP-grade batches met all predefined specification parameters together with long-term kit stability and stability of the product [^99mTc]Tc-TECANT-1. Furthermore, the selected precursor content complies with micro-dosing, based on an extended single-dose toxicity study, where histopathology NOEL was established at 0.5 mg/kg BW, being more than 1000 times higher than the planned human dose of 20 µg. In conclusion, [^99mTc]Tc-TECANT-1 is suitable to be advanced into a first-in-human clinical trial.

A selective, sensitive and low sample consumption GC method for determination of residual solvents in PSMA samples was developed. Selectivity with respect to solvents such as ethanol, diethyl ether, 2-propanole, acetonitrile, dichloromethane, used in manufacturing of PSMA-11, was obtained on two different GC systems and columns. In all these cases, good separation and other system suitability parameters were obtained. The values of detection limit (LOD) and limit of quantitation (LOQ) were estimated and verified experimentally for ethanol, diethyl ether, 2-propanol (IPA), acetonitrile (ACN) and dichloromethane. Full validation parameters i.e.: selectivity, limit of detection (LOD), limit of quantitation (LOQ), linearity, precision, accuracy, robustness and system suitability parameters are presented with respect to ACN and IPA. Accuracy and precision were measured on two GC systems. Statistical tests exhibit, that there are no significant differences in accuracy and precision between two GC systems

In EDDA (ethylenediamino-N,N'-diacetic acid), two main impurities, 2-oxopiperazine-1-ylacetic acid (OPPAA) and N-(2-aminoethylglycine) (AEG), were identified by LC-MS analysis. OPPAA is not commercially available. It was therefore synthesised and its structure was confirmed by elemental, 1H NMR, FT-IR and MS analysis, and an HPLC method with UV detection was developed to test its purity. It turned out that UV detection was inadequate for the analysis of EDDA purity - the results were not consistent with those obtained by titration and 1H NMR. Therefore, a method based on refractometric detection (RID) was developed. Validation of the method was performed, assessing system suitability (SST), limits of detection (LOD) and quantitation (LOQ), linearity, accuracy, precision and robustness. For both contaminants (AEG and OPPAA), a detection limit of 0.02% was achieved. A linear relationship between the signal of both contaminants was observed in the range of LOQ to 0.5 % vs EDDA. The method has satisfactory linearity and accuracy for both impurities and acceptable precision. The results obtained by three analysts were compared using statistical tests. Using refractometric detection, the results of OPPAA determination based on HPLC purity (as a percentage of the OPPAA peak area relative to the area of all signals) and relative to the standard are very similar.