Biodistribution of 68Ga-NODA-Aminoglucose in Intact and Tumor-Bearing Mice

We studied the biodistribution of ⁶⁸Ga-NODA-aminoglucose (⁶⁸Ga-NODA-AG) in normal mice and mice with experimental model of colon adenocarcinoma tumor. It was shown that ⁶⁸Ga-NODA-aminoglucose was retained in the tumor for 3 h after injection and demonstrated high level of accumulation in the tumor. Rapid clearance of radioactivity from other organs was observed. The results suggest that ⁶⁸Ga-NODA-aminoglucose is a promising agent for tumor visualization by positron emission tomography.

A Comparative Study of the Pharmacokinetics of Bis- and Pentaphosphonic Acids Labeled with Gallium-68 in Rats with Experimental Model of Bone Callus

We analyzed biodistribution of ⁶⁸Ga-labeled hydroxyethylidenediphosphonic acid (⁶⁸Ga-HEDP) and diethylenetriaminepentakis(methylenephosphonic acid) (⁶⁸Ga-DTPMP) in Wistar rats with experimental model of bone callus. It was shown that the content of ⁶⁸Ga-DTPMP and ⁶⁸Ga-HEDP in bone callus was ~1.5-fold higher than in intact femur. ⁶⁸Ga-DTPMP was characterized by higher stability in vivo, higher uptake in the bone tissue, and lower uptake in others visceral organs in comparison with ⁶⁸Ga-HEDP. Thus, ⁶⁸Ga-DTPMP had more suitable pharmacokinetic properties than ⁶⁸Ga-HEDP.

Experimental Study of the Biodistribution of New Bone-Seeking Compounds Based on Phosphonic Acids and Gallium-68

We investigate biodistribution of gallium-labeled hydroxyethylidenediphosphonic acid (⁶⁸Ga-HEDP) and diethylenetriaminepentakis(methylenephosphonic acid) (⁶⁸Ga-DTPMP) in intact Wistar rats. It was shown that ⁶⁸Ga-DTPMP accumulated mainly in the bone tissue providing high femur/blood and femur/muscle ratios and had high stability in vivo. In contrast, ⁶⁸Ga-HEDP was characterized by low stability and high uptake of radioactivity in blood throughout the study. So ⁶⁸Ga-DTPMP can be considered as a new prospective radiotracer in oncology for imaging bone tissue metastasis by positron emission tomography.

Nuclear nanomedicine using Si nanoparticles as safe and effective carriers of 188Re radionuclide for cancer therapy

Nuclear nanomedicine, with its targeting ability and heavily loading capacity, along with its enhanced retention to avoid rapid clearance as faced with molecular radiopharmaceuticals, provides unique opportunities to treat tumors and metastasis. Despite these promises, this field has seen limited activities, primarily because of a lack of suitable nanocarriers, which are safe, excretable and have favorable pharmacokinetics to efficiently deliver and retain radionuclides in a tumor. Here, we introduce biodegradable laser-synthesized Si nanoparticles having round shape, controllable low-dispersion size, and being free of any toxic impurities, as highly suitable carriers of therapeutic 188Re radionuclide. The conjugation of the polyethylene glycol-coated Si nanoparticles with radioactive 188Re takes merely 1 hour, compared to its half-life of 17 hours. When intravenously administered in a Wistar rat model, the conjugates demonstrate free circulation in the blood stream to reach all organs and target tumors, which is radically in contrast with that of the 188Re salt that mostly accumulates in the thyroid gland. We also show that the nanoparticles ensure excellent retention of 188Re in tumor, not possible with the salt, which enables one to maximize the therapeutic effect, as well as exhibit a complete time-delayed conjugate bioelimination. Finally, our tests on rat survival demonstrate excellent therapeutic effect (72% survival compared to 0% of the control group). Combined with a series of imaging and therapeutic functionalities based on unique intrinsic properties of Si nanoparticles, the proposed biodegradable complex promises a major advancement in nuclear nanomedicine.

[New Radiopharmaceuticals Based on Prostate-Specific Inhibitors of Membrane Antigen for Diagnostics and Therapy of Metastatic Prostate Cancer]

About 10.7% cases of prostate cancer were registered in Russia in 2011 (40,000 patients). More than half of cancer cases were revealed in advanced (III-IV) stages when metastases inevitably developed quickly. Clinical problem of early diagnostics and treatment of metastatic prostate cancer is still not solved. Anatomical imaging techniques have low sensitivity and specificity for the detection of this disease. Metabolic visualization methods which use prostate specific antigen (PSA) as a marker are also ineffective. This article describes prostate-specific membrane antigens (PSMA) that are proposed as a marker for diagnostics and therapy of prostate cancer. The most promising PSMA-based radiopharmaceutical agent for diagnostics has been developed and clinically tested in the European countries. These pharmaceuticals are based on small peptide molecules modified with urea, and have the highest affinity to PSMA. Favorable phannacokinetics, rapid accumulation in the tumor and rapid excretion from the body are beneficial features of these pharmaceuticals.

[Pharmacokinetic and dosimetric characteristics of new radiopharmaceutical based on complexes of 103Pd and albumin microspheres]

Results of the study of absorbed dose formed in organs and tissues of mice after administration of new therapeutic radiopharmaceutical on the base of 103Pd and albumin microspheres (MSA) are presented. Pharmacokinetic parameters of preparation distribution in the body of animals were experimentally determined and then absorbed doses were calculated using MCNP code for the developed mathematical model of mouse. It was shown that absorption of 103Pd-MSA in tumor, physical properties of 103Pd and daughter radionuclide 103mRh provide a targeted irradiation of tumor as compared with the adjusting tissues and critical organs. In administration to tumor muscle tissue of the leg of experimental animals after 15 days following the injection of 103Pd-MSA the accumulated absorbed dose was 15 times less than corresponding one in tumor. In a critical organ (kidneys) the accumulated absorbed dose was 20 times less than in tumor. The work performed as a stage of pre-clinical testing of the radiopharmaceutical.

[The behavior of 125I microspheres of serum albumin in the body of rabbits administered the preparation selectively into the renal artery]

Intraarterial selective injection of serum albumin microspheres into the kidney resulted in embolization of the vessels with microspheres of different sizes. In vivo radiometry made it possible to improve the localization of microspheres and their distribution in the animals' bodies at varying time of observation. Pathomorphological investigations showed optimum sizes of microspheres causing prolonged retention of microparticles at the site of injection without considerable morphological changes of body tissues. The method of using microspheres as a radionuclide carrier was shown to hold promise for therapeutic purposes.

[Study of local capillary circulation using labeled albumin microspheres during osteotomy of the maxilla (experimental study)]

The authors presented the results of experiments on 14 random bred dogs in whom fragmentary osteotomy of the maxilla at the level of 7 perpendicular 7 teeth was performed with subsequent investigation of the volumetric blood flow rate in soft and osseous tissues of the osteotomized fragment using labeled albumin microspheres. The animals were divided into 4 groups (the study group and control groups). The volumetric blood flow rate was investigated over time with the monitoring of the CV system 1 (the 2nd group), 6 (the 3rd group) and 24 h (the 4th group) after operation. The total reduction of the blood flow in the tissues of the osteotomized fragment as compared to that of the control group was 54.5% (in the 1st group), 39.3% (in the 2nd group) and 41% (in the 3rd group). The results of the study showed correlation between the blood flow rate reduction in the soft tissue structures and osseous tissue.

[Effectiveness of the antitumor action of bleomycetin in short-term hyperglycemia]

Experimental studies on rats with sarcoma 45 showed that antitumor efficacy of bleomycetin could be markedly increased by inducing short-term hyperglycemia. It was noted that the theoretical value of the additive effect of these factors was lower than the experimental one. This is in favour of the synergistic mechanism of bleomycetin action under conditions of hyperglycemia.

[57Co-bleomycetin distribution in the body of experimental animals with hyperglycemia]

Distribution of 57Co-bleomycetin in organs and tissues of rats with experimental short-term hyperglycemia was studied. Hyperglycemia was induced by intraperitoneal administration of 40 per cent glucose solution in doses of 1 to 10.4 g/kg. The labeled antitumor antibiotic was also administered intraperitoneally (0.2-0.8 MBq per animal). The data on both the external radiometry in the area under the animal limb and the radiometry of separate organs and tissues showed that hyperglycemia markedly altered pharmacokinetics of the labeled antibiotic and retarded its elimination. With respect to the lungs it even increased the drug tropism and accumulation. This information may be useful in radionuclide diagnosis and therapy in particular of lung cancer. The time course of glucose concentration in blood was not an adequate criterion of hyperglycemia influence since the influence of hyperglycemia on retarding the drug elimination was also observed when the level of glucose in blood did not differ from the initial one.

[Characteristics of 57Co-bleomycetin accumulation in the primary tumor and in its metastases to the lungs in mice with Lewis carcinoma]

Distribution of 57Co-bleomycin was studied in mice with Lewis carcinoma implanted into different parts of the body. It was found that organ distribution of the labeled antibiotic did not depend on the tumor localization. The accumulation level of 57Co-bleomycin in Lewis carcinoma implanted subcutaneously into the pad foot was 3 times higher than that in the healthy pad. Resection of the primary tumor stimulated metastasis to the lungs resulting in relatively selective accumulation of the antibiotic in the lungs. The levels of 57Co-bleomycin in the lungs the main part of which was affected with metastases were 3--7 times higher than the respective control values.

[57Co-bleomycetin pharmacokinetics in the body of mice with LIO-1 lymphosarcoma]

Pharmacokinetics of 57Co-bleomycetin was studied on mice with lymphosarcoma LIO-1. It was found that at early periods of intravenous administration of the labeled antibiotic, i.e. within the period from 5 minutes to 1 hour its higher levels are detected in the liver, kidneys, blood serum, lungs, intestine and tumor. At later periods the drug levels in the organs and tissues gradually decrease and by the 72nd hour the concentration of 57Co-bleomycetin in the blood serum appears to be 30 times lower as that after 5 minutes. In the muscles and tumor its concentrations by that period are 15 and 2 times lower respectively. Radiometry of the animals showed that within the first 24 hours more than 85 per cent of 57Co-bleomycetin was excreted from the mice.

[Effect of 57Co-bleomycetin on the immune response induced in mice by ram erythrocytes]

The effect of 57Co-bleomycin on the immune response induced by sheep red cells was studied on mice. It was found that the immune response was not suppressed when the labeled antibiotic was used in a single dose of 5-20 mg/kg. By the 5th day the level of 57Co-bleomycin in the skin, thymus and blood was 3-10 times higher than that of 57CoCl2 and in the spleen it was 1.3-1.5 times higher.