Biodistribution Studies of a New Antitumor Compound Based on Nanoporous Nanodiamond Composite Labeled with Rhenium-188

This study evaluated a new drug delivery system for local radiotherapy on the base of nanoporous nanodiamond composites (NDC) labeled with β-emitting radionuclide rhenium-188. The biodistribution of labeled compound was assessed after intratumoral (i.t.) and intramuscular (i.m.) injection. 24 mice-bearing solid Ehrlich carcinoma xenografts received i.t. injections of 0.370 ± 0.074 MBq 188Re-nanoporous diamond composites. Another 24 intact mice were injected with the same preparation intramuscularly. The samples of different organs and tissues were collected for gamma count. After i.t. and i.m. administration of 188Re-nanoporous NDC a considerable amount of radioactivity retained at the site of injection. In tumor tissue the total amount of activity decreased from 92.68 % to 9.63 % of injected dose (ID) throughout the study. The removal of injected activity from muscular tissue was faster as compared with tumor tissue, and declined from 81.06 % to 8.40 % ID for up to 72 h. Therefore, after i.m. injection the accumulation of radioactivity in healthy organs and tissues was slightly higher than after i.t. injection. In conclusion, it was demonstrated that 188Renanoporous diamond composites had the potential radiotherapeutic significance. Keywords: composite materials, nanodiamond, rhenium-188, cancer radiotherapy, local radiotherapy

Preliminary Biological Evaluation of Leucine Labeled with Gallium-68—A Potential Agent for Tumor Imaging

Amino acids are important nutrients for proliferating tumor cells, so their transport is generally increased in many malignant tumor cells. Radiolabeled amino acids are of great interest as they can be alternative or complement tracers to the already wellestablished radiopharmaceuticals such as 18F-FDG. The purpose of this study was to synthesize and characterize a novel 68Ga labeled leucine analog, 68Ga-leucine, as a potential imaging agent for tumors which may not be amenable to imaging by 18F-FDG PET. Biodistribution studies of 68Ga-leucine were performed in Wistar rats with transplanted cholangioma RS-1 xenografts after intravenous injection. 68Ga-leucine demonstrated high in vivo stability. Accumulation of 68Ga-leucine at xenograft tumors was about 2-4 higher as compared with 68GaCl3 and reached 0.79% ID/g. Among the soft tissue organs, only kidney had a relatively high uptake. The amount of radioactivity in other organs didn’t exceed 1% ID/g. The results suggest that 68Ga-leucine has the potential to be a new additional diagnostic tool for PET imaging of tumors. Keywords: gallium-68, leucine, radiolabeled amino acids, positron emission tomography, tumor imaging

Preclinical Evaluation of Antitumor Efficacy of a New Radiopharmaceutical Based on Thermoresponsive Carrier and Samarium-153

This work is devoted to studying the in vivo antitumor efficacy of the new injection radiopharmaceutical based on thermoresponsive polymer and β−-emitting radionuclide samarium-153 (153Sm-KARP-CheM). The study of in vivo antitumor efficacy was performed using mice F1 and C57Bl/6 with transplanted subcutaneously sarcoma S37 and melanoma B16, respectively. The animals received single intratumoral bolus injections of 37 MBq (1 mCi), or 18.5 MBq (0.5 mCi) of 153Sm-KARP-CheM, or saline in a volume 0.1 ml. The efficacy of antitumortreatment was evaluated using tumor growth inhibition index (TGI, %) and increase of average life span (ILS, %). The most meaningful therapeutic efficacy after intratumoral injection of 153Sm-KARPCheM was observed in melanoma-bearing mice C57Bl/6. The highest values of TGI for melanoma B16 were 79.5% and 79.6% after treatment with 18.5 MBq or 37 MBq, respectively. An increase of average life span by 17.1% was found in group of melanoma-bearing mice treated with 37 MBq of 153Sm-KARP-CheM only. Tumor growth inhibition of sarcoma S37 was slightly lower as compared with melanoma B16: 62.5% and 59.0% in 37 MBq and 18.5 MBq groups, respectively. 153Sm-KARP-CheM didn’t increase average life span of treated animals. In conclusion, 153Sm-KARP-CheM seems to be effective radiopharmaceutical for local tumor radiotherapy. Keywords: thermoresponsive polymer, samarium-153, radionuclide therapy of cancer, sarcoma S37, melanoma B16, antitumor efficacy