Infrared-based module for the synthesis of 68Ga-labeled radiotracers

68Ga-DOTA and analogs: Current status and future perspectives

The construction of the ⁶⁸Ge/⁶⁸Ga generator has increased application of radiopharmaceuticals labeled with this isotope in medicine. ⁶⁸Ga-PET is widely employed in the management of neuroendocrine tumors but favorable chemistry with tri- and tetraaza-ring molecules has opened wide range of ⁶⁸Ga application in other fields of PET imaging. This review covers the radiopharmaceuticals labeled with gallium in molecular imaging and shows perspectives on the use of gallium-68 as a substitute for technetium-99, fluorine-18 and carbon-11 in some applications.

Prospective of ⁶⁸Ga-radiopharmaceutical development

Positron Emission Tomography (PET) experienced accelerated development and has become an established method for medical research and clinical routine diagnostics on patient individualized basis. Development and availability of new radiopharmaceuticals specific for particular diseases is one of the driving forces of the expansion of clinical PET. The future development of the ⁶⁸Ga-radiopharmaceuticals must be put in the context of several aspects such as role of PET in nuclear medicine, unmet medical needs, identification of new biomarkers, targets and corresponding ligands, production and availability of ⁶⁸Ga, automation of the radiopharmaceutical production, progress of positron emission tomography technologies and image analysis methodologies for improved quantitation accuracy, PET radiopharmaceutical regulations as well as advances in radiopharmaceutical chemistry. The review presents the prospects of the ⁶⁸Ga-based radiopharmaceutical development on the basis of the current status of these aspects as well as wide range and variety of imaging agents.

(68)Ga-labeled DOTA-peptides and (68)Ga-labeled radiopharmaceuticals for positron emission tomography: current status of research, clinical applications, and future perspectives

In this review we give an overview of current knowledge of (68)Ga-labeled pharmaceuticals, with focus on imaging receptor-mediated processes. A major advantage of a (68)Ge/(68)Ga generator is its continuous source of (68)Ga, independently from an on-site cyclotron. The increase in knowledge of purification and concentration of the eluate and the complex ligand chemistry has led to (68)Ga-labeled pharmaceuticals with major clinical impact. (68)Ga-labeled pharmaceuticals have the potential to cover all today's clinical options with (99m)Tc, with the concordant higher resolution of positron emission tomography (PET) in comparison with single photon emission computed tomography. (68)Ga-labeled analogs of octreotide, such as DOTATOC, DOTANOC, and DOTA-TATE, are in clinical application in nuclear medicine, and these analogs are now the most frequently applied of all (68)Ga-labeled pharmaceuticals. All the above-mentioned items in favor of successful application of (68)Ga-labeled radiopharmaceuticals for imaging in patients are strong arguments for the development of a (68)Ge/(68)Ga generator with Marketing Authorization and thus to provide pharmaceutical grade eluate. Moreover, now not one United States Food and Drug Administration-approved or European Medicines Agency-approved (68)Ga-radiopharmaceutical is available. As soon as these are achieved, a whole new radiopharmacy providing PET radiopharmaceuticals might develop.

Nanoceria-PAN composite-based advanced sorbent material: a major step forward in the field of clinical-grade 68Ge/68Ga generator

The (68)Ge/(68)Ga generator has high potential for clinical positron emission tomography (PET) imaging. However, because of the unavailability of a suitable sorbent material, the commercially available (68)Ge/(68)Ga generators are not directly adaptable for the preparation of (68)Ga-labeled radiopharmaceuticals. In view of this, a new nanoceria-polyacrylonitrile (PAN) composite sorbent has been synthesized by decomposition of a cerium oxalate precursor to cerium oxide and its subsequent incorporation in PAN matrix for the development of a clinical grade (68)Ge/(68)Ga generator. The X-ray diffraction (XRD) studies and BET nitrogen adsorption technique revealed that nanocrystalline ceria had an average particle size of approximately 10 nm, surface area of 72 +/- 3 m(2)/g and an average pore size of 3.8 +/- 0.1 A. Investigation of the distribution ratio (K(d)) values for the prepared sorbent in 0.01 N HCl medium revealed the suitability of the sorbent for the quantitative retention of (68)Ge and efficient elution of clinical grade (68)Ga. A 370 MBq (10 mCi) (68)Ge/(68)Ga chromatographic generator was developed using this sorbent. (68)Ga could be regularly eluted from this generator with >80% elution yield. The eluted (68)Ga possess high radionuclidic purity (<1 x 10(-5)% of (68)Ge impurity), chemical purity (<0.1 ppm of Ce, Fe and Mn ions) and was amenable for the preparation of (68)Ga-labeled radiopharmaceuticals. The generator gave a consistent performance with respect to the elution yield and purity of (68)Ga over an extended period of 7 months.

A fully automated synthesis for the preparation of 68Ga-labelled peptides

BACKGROUND

Generator-produced Ga has attracted increasing interest for radiolabelling peptides used in PET applications. So far, the synthesis of Ga-peptide radiopharmaceuticals is mainly based on semi-automated systems. Here we describe a fully automated approach for the synthesis of Ga-labelled peptides.

METHOD

A commercially available Ga generator was eluted with 0.1 mol . l HCl. Reaction parameters such as buffer conditions, pH range, reaction temperature and time, volume of reaction solution and generator fraction were optimized for labelling DOTA-Tyr-octreotide (DOTATOC). Reaction yields, pH, radiochemical purity, sterility, endotoxins, breakthrough of Ge and final Ge content were determined. A fully automated radiopharmaceutical synthesis device based on a modular concept for remote-controlled processing was developed and evaluated for a number of DOTA-derivatized peptides.

RESULTS

DOTATOC could be labelled in almost quantitative yields by heating 10-50 nmol peptide at pH 3.5-4.0 for 5 min at 95 degrees C in 1.5 ml. Purification using a reversed-phase cartridge was required to avoid any potential Ge breakthrough: final activities of Ge were below 100 Bq . ml. Automated synthesis resulted in overall decay-corrected reaction yields of about 60% within 10 min. Even after 1 year using a 1110 MBq generator more than 130 MBq Ga-DOTATOC could be obtained. Moreover, it was demonstrated that a variety of DOTA-derivatized peptides can be labelled using identical reaction conditions with high yields.

CONCLUSION

The system described allows the fully automated, efficient and rapid preparation of Ga-DOTA-derivatized peptides. It has been used successfully and reliably for routine preparations in clinical studies.