In the frame of “precision medicine”, the scandium radionuclides have recently received considerable interest, providing personalised adjustment of radiation characteristics to optimize the efficiency of medical care or therapeutic benefit for particular groups of patients. Radionuclides of scandium, namely scandium-43 and scandium-44 (43/44Sc) as positron emitters and scandium-47 (47Sc), beta-radiation emitter, seem to fit ideally into the concept of theranostic pair. This paper aims to review the work on scandium isotopes production, coordination chemistry, radiolabeling, preclinical studies and the very first clinical studies. Finally, standardized procedures for scandium-based radiopharmaceuticals have been proposed as a basis to pave the way for elaboration of the Ph.Eur. monographs for perspective scandium radionuclides.

64Cu is considered to be one of the most promising radioisotope in radiotheragnostics (combining therapeutics with diagnostics) because its positron emission is suitable for PET imaging while the combination of...

The radiosynthesis, as well as the in vivo and ex vivo biodistribution of the 11C radiolabelled 3‐(4,5‐diphenyl‐1,3‐oxazol‐2‐yl)propanal oxime (6, [11C]SZV 1287) are reported. SZV 1287 is a novel semicarbazide‐sensitive amine oxidase (SSAO) inhibitor and a promising candidate to be a novel analgesic for the treatment of neuropathic pain. Its radiolabelling was developed via a four‐step radiosynthesis which started from the reaction of a Grignard reagent with [11C]CO2 to produce [11C]oxaprozin (3). In the next step this carboxylic acid 3 was directly reduced to yield the corresponding aldehyde, which was then converted into the oxime. [11C]SZV 1287 was administered to male NMRI mice. The animals were examined with dynamic PET/MR imaging for 90 minutes. Biodistribution studies were performed at 10, 30, 60 and 120 minutes post injection. The accumulation of the labelled compound was observed in the brain of the animals. The main excretion pathway was found to be through the liver and intestines. These studies provide preliminary information for pharmacokinetic characterization of the SZV 1287.

Tumor hypoxia induces angiogenesis, which is required for tumor cell survival. The aminopeptidase N receptor (APN/CD13) is an excellent marker of angiogenesis since it is overexpressed in angiogenic blood vessels and in tumor cells. Asparagine-glycine-arginine (NGR) peptide analogs bind selectively to the APN/CD13 recepto, therefore, they are important vector molecules in the development of a PET radiotracer which is capable of detecting APN-rich tumors. To investigate the effect of glycosylation and pegylation on in-vivo efficacy of an NGR-based radiotracer, two 68Ga-labeled radioglycopeptides were synthesized. A lactosamine derivative was applied to glycosylation of the NGR derivative and PEG4 moiety was used for pegylation. The receptor targeting potential and biodistribution of the radiopeptides were evaluated with in vivo PET imaging studies and ex vivo tissue distribution studies using B16-F10 melanoma tumor-bearing mice. According to these studies, all synthesized radiopeptides were capable of detecting APN expression in B16-F10 melanoma tumor. In addition, lower hepatic uptake, higher tumor-to background (T/M) ratio and prolonged circulation time were observed for the novel [68Ga]-10 radiotracer due to pegylation and glycosylation, resulting in more contrasting PET imaging. These in vivo PET imaging results correlated well with the ex vivo tissue distribution data.

Hypoxia promotes angiogenesis, which is crucial for tumor growth, and induces malignant progression and increases the therapeutic resistance. Positron emission tomography (PET) enables the detection of the hypoxic regions in tumors using 2-nitroimidazole-based radiopharmaceuticals. We describe here a physicochemical study of the Sc(DO3AM-NI) complex, which indicates: (a) relatively slow formation of the Sc(DO3AM-NI) chelate in acidic solution; (b) lower thermodynamic stability than the reference Sc(DOTA); (c) however, it is substantially more inert and consequently can be regarded as an excellent Sc-binder system. In addition, we report a comparison of 44Sc-labeled DO3AM-NI with its known 68Ga-labeled analog as a hypoxia PET probe. The in vivo and ex vivo biodistributions of 44Sc- and 68Ga-labeled DO3AM-NI in healthy and KB tumor-bearing SCID mice were examined 90 and 240 min after intravenous injection. No significant difference was found between the accumulation of 44Sc- and 68Ga-labeled DO3AM-NI in KB tumors. However, a significantly higher accumulation of [68Ga]Ga(DO3AM-NI) was found in liver, spleen, kidney, intestine, lung, heart and brain than for [44Sc]Sc(DO3AM-NI), leading to a lower tumor/background ratio. The tumor-to-muscle (T/M) ratio of [44Sc]Sc(DO3AM-NI) was approximately 10–15-fold higher than that of [68Ga]Ga(DO3AM-NI) at all time points. Thus, [44Sc]Sc(DO3AM-NI) allows the visualization of KB tumors with higher resolution, making it a promising hypoxia-specific PET radiotracer.