Development of Semiautomated Module for Preparation of 131I Labeled Lipiodol for Liver Cancer Therapy.

Intra-arterial injection of 131I Lipiodol is an effective treatment option for primary hepatocellular carcinoma as it delivers high radiation dose to liver tumor tissue with minimal accumulation in adjacent normal tissue. The present article demonstrates design, fabrication, and utilization of a semiautomated radiosynthesis module for preparation of 131I labeled Lipiodol. The radiolabeling method was standardized for preparation of patient dose of 131I labeled Lipiodol radiochemical yield (RCY); radiochemical purity (RCP) and pharmaceutical purity of the product were determined using optimized procedures. Sterile and apyrogenic 131I labeled Lipiodol in >60% RCY could be prepared with >95% RCP. Preclinical evaluation in animals indicated retention of more than 90% of activity at 24 hours postportal vein injection. This is the first report demonstrating potential application of simple user friendly and safe semiautomated system for routine production of 131I labeled Lipiodol, which is adaptable at centralized hospital radiopharmacies. The described prototype module can be modified as per demand for preparation of other therapeutic radiopharmaceuticals.

Allocation of 14C assimilated in late spring to tissue and biochemical stem components of cork oak (Quercus suber L.) over the seasons.

Carbon distribution in the stem of 2-year-old cork oak plants was studied by (14)CO(2) pulse labeling in late spring in order to trace the allocation of photoassimilates to tissue and biochemical stem components of cork oak. The fate of (14)C photoassimilated carbon was followed during two periods: the first 72 h (short-term study) and the first 52 weeks (long-term study) after the (14)CO(2) photosynthetic assimilation. The results showed that (14)C allocation to stem tissues was dependent on the time passed since photoassimilation and on the season of the year. In the first 3 h all (14)C was found in the polar extractives. After 3 h, it started to be allocated to other stem fractions. In 1 day, (14)C was allocated mostly to vascular cambium and, to a lesser extent, to primary phloem; no presence of (14)C was recorded for the periderm. However, translocation of (14)C to phellem was observed from 1 week after (14)CO(2) pulse labeling. The phellogen was not completely active in its entire circumference at labeling, unlike the vascular cambium; this was the tissue that accumulated most photoassimilated (14)C at the earliest sampling. The fraction of leaf-assimilated (14)C that was used by the stem peaked at 57% 1 week after (14)CO(2) plant exposure. The time lag between C photoassimilation and suberin accumulation was ∼8 h, but the most active period for suberin accumulation was between 3 and 7 days. Suberin, which represented only 1.77% of the stem weight, acted as a highly effective sink for the carbon photoassimilated in late spring since suberin specific radioactivity was much higher than for any other stem component as early as only 1 week after (14)C plant labeling. This trend was maintained throughout the whole experiment. The examination of microautoradiographs taken over 1 year provided a new method for quantifying xylem growth. Using this approach it was found that there was more secondary xylem growth in late spring than in other times of the year, because the calculated average cell division time was much shorter.

Instrumentation and radiopharmaceutical validation.

Although the promise of new positron emission tomography (PET) imaging agents is great, the process of bringing these agents to commercialization remains in its infancy. There are no PET products today that have gone through the full clinical and chemistry development process required to gain marketing approval by the US Food and Drug Administration (FDA). The purpose of this paper was to review validation from the perspective of the chemistry, manufacturing and controls (CMC) section of an FDA filing, as well as the validation requirements described in FDA good manufacturing practice (GMP) regulations, guidance documents and general chapters of the US Pharmacopeia (USP). The review includes discussion of validation from development to commercial production of PET radiopharmaceuticals with a special emphasis on equipment and instrumentation used in production and testing. The goal is to stimulate a dialog that leads to the standardization of industry practices and regulatory requirements for validation practices in PET.

Development of acetylated HDD kit for preparation of 188Re-HDD/lipiodol.

A lipiodol solution of (188)Re-4-hexadecyl-2,2,9,9-tetramethyl-4,7-diaza-1,10-decanedithiol ((188)Re-HDD/lipiodol) is in clinical study for liver cancer therapy. However, formulation of it is difficult due to highly active and unstable sulfhydryl groups. We produced new kits using diacetylated HDD (AHDD), in which sulfhydryl groups are protected. We found that AHDD kit can replace HDD kit due to an increased stability for formulation, the better radiolabeling efficiency (78%) and the equivalent biodistribution pattern in mice.

A kit formulation for the preparation of 188Re-lipiodol: preclinical studies and preliminary therapeutic evaluation in patients with unresectable hepatocellular carcinoma.

A lyophilized kit formulation for the efficient labelling of lipiodol with generator-produced rhenium-188 is described. The preliminary preparation of the lipophilic complex bis-(diethyldithiocarbamato)nitrido rhenium-188 (188ReN-DEDC) was carried out using a two-vial kit containing S-methyl-N-methyl-dithiocarbazate, SnCl2 and sodium oxalate in the first vial, and diethyldithiocarbamate and a carbonate buffer in the second vial. After mixing of the reaction solution with lipiodol, the complex 188ReN-DEDC was quantitatively extracted and retained by this hydrophobic substance, thus allowing the stable incorporation of the beta-emitting radionuclide. The radiochemical purity of the complex 188ReN-DEDC was 97+/-2%. The activity extracted into the lipiodol phase was 96+/-3% of the initial activity, indicating that the complex 188ReN-DEDC was almost quantitatively removed from the aqueous reaction solution. In vitro stability studies in human plasma, at 37 degrees C, demonstrated the release of less than 15% of the activity within three half-lives. The biodistribution of Re-lipiodol in non-tumour-bearing Wistar rats at 6, 24, 48 and 72 h after intraportal venous injection showed one-third of total activity in the liver at 6 h, declining to 2% retention at 72 h. Bowel uptake at 6 and 24 h declined to low levels at 48 and 72 h. Renal activity peaked at 1.7%, diminishing to 0.6% over 48 h. Rat whole body gamma imaging showed gut activity in addition to hepatic uptake at 6 and 24 h, but only liver was evident from 48 to 72 h. Kidneys were not demonstrable at any imaging time point. In nine patients, activity was localized in the tumours immediately following intrahepatic arterial injection. Computed tomography/single-photon emission computed tomography (CT/SPECT) imaging at 1 and 24 h confirmed the retention of 188Re-lipiodol in the hepatoma, with minimal gut uptake and no lung activity over 24 h. These patients were subsequently treated with activities of 2.5-5 GBq of 188Re-lipiodol fractions without adverse effects. Six patients followed for up to 2 years in the pilot study achieved stable disease and there was objective partial response in one patient. Repeated treatments were performed on two to three occasions in three patients without evident toxicity. An additional patient given 6 GBq of 188Re-lipiodol demonstrated myelosuppression, which recovered with granulocyte colony-stimulating factor (GCSF) and platelet support. It is concluded that 188Re-lipiodol, prepared using our novel kit formulation, is stable in vivo and provides safe and effective therapy of unresectable hepatocellular carcinoma when given via the hepatic artery, either alone or in combination with transarterial chemoembolization.

Of flux and flooding: the advantages and problems of different isotopic methods for quantifying protein turnover in vivo : II. Methods based on the incorporation of a tracer.

The most common methods for measuring the incorporation of tracer amino acids into tissue protein are the constant tracer infusion and the flooding dose. The flooding dose is an attractive method for measuring tissue protein synthesis because of its convenience and precision. A primary assumption of the method, that the free amino acid precursor pools are equilibrated with the true precursor pool, aminoacyl-transfer RNA, has recently been validated. When short labelling periods are involved, the large dose of amino acid does not appear to alter protein synthesis. The constant tracer infusion is a satisfactory method from a theoretical point of view, but its use requires the measurement of the protein synthetic precursor pool. The best estimate of the aminoacyl-tRNA precursor pool for the constant infusion method appears to be the acid-soluble tissue pool in muscle and VLDL apolipoprotein B-100 in the liver. The experimental approach chosen for measuring tissue protein synthesis should be dictated by the question being addressed.