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