{"title":"Synthesis, Radiolabeling, and Preclinical Evaluation of <sup>68</sup>Ga/<sup>177</sup>Lu-Labeled Leuprolide Peptide Analog for the Detection of Breast Cancer.","authors":"Subhani M Okarvi, Ibrahim Al-Jammaz","doi":"10.1089/cbr.2021.0370","DOIUrl":null,"url":null,"abstract":"<p><p><b><i>Objectives:</i></b> The expansion of novel and potent tumor receptor binding peptides is a promising approach for the precise targeting of various cancer. Leuprolide is a 9-residue peptide analog of gonadotropin-releasing hormone and is extensively used in the treatment of sex hormone-dependent tumors, including prostate, breast, and ovarian cancer. This preclinical study was undertaken to prepare a new radiolabeled leuprolide peptide for the detection of breast carcinoma. <b><i>Methods:</i></b> A 1,4,7,10-tetraazacyclododecane-<i>N,N</i>'<i>,N</i>''<i>,N</i>'''-tetraacetic acid (DOTA)-coupled 9-amino acid leuprolide peptide was synthesized after typical 9-fluorenylmethyl-oxycarbonyl-based solid-phase peptide synthesis and radiolabeled with both <sup>68</sup>Ga and <sup>177</sup>Lu radionuclides for theranostic use. The systemic pharmacokinetics was done in healthy balb/c mice. The <i>in vitro</i> tumor cell binding affinity was determined on MCF7, T47D, and MDA-MB-231 breast cancer cell lines. <i>In vivo</i> tumor targeting and micro positron-emission tomography imaging was performed on nude mice with MCF7 breast tumor xenografts. <b><i>Results:</i></b> The leuprolide peptide was conveniently synthesized by solid-phase synthesis strategy and its identity and purity were validated by mass spectrometry and high-performance liquid chromatography. The peptide radiolabeled efficiently (˃94%) with both diagnostic (<sup>68</sup>Ga) and therapeutic (<sup>177</sup>Lu) radionuclides and displayed nanomolar binding potency to all three tested MCF7, T47D, and MDA-MB-231 cell lines. Fast and favorable pharmacokinetics was observed for <sup>68</sup>Ga/<sup>177</sup>Lu-leuprolide in healthy Balb/c mice. In nude mice, <sup>68</sup>Ga-leuprolide peptide exhibited rapid clearance from the blood circulation with low to moderate (up to 5% ID/g) uptake/retention by the major body organs. The accumulation in the estrogen receptor-positive MCF7 tumor was 2.24% ± 0.62% ID/g at 45 min p.i, with good tumor to blood and muscle uptake ratios. The radiolabeled peptide was excreted primarily through the renal pathway. <b><i>Conclusion:</i></b> The encouraging results of this initial study demonstrate that additional testing of this leuprolide peptide seems to be indicated because of its convincing potential to be a new agent for the management of breast carcinoma.</p>","PeriodicalId":518937,"journal":{"name":"Cancer biotherapy & radiopharmaceuticals","volume":" ","pages":"372-383"},"PeriodicalIF":0.0000,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"2","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Cancer biotherapy & radiopharmaceuticals","FirstCategoryId":"3","ListUrlMain":"https://doi.org/10.1089/cbr.2021.0370","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2022/3/21 0:00:00","PubModel":"Epub","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 2
Abstract
Objectives: The expansion of novel and potent tumor receptor binding peptides is a promising approach for the precise targeting of various cancer. Leuprolide is a 9-residue peptide analog of gonadotropin-releasing hormone and is extensively used in the treatment of sex hormone-dependent tumors, including prostate, breast, and ovarian cancer. This preclinical study was undertaken to prepare a new radiolabeled leuprolide peptide for the detection of breast carcinoma. Methods: A 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA)-coupled 9-amino acid leuprolide peptide was synthesized after typical 9-fluorenylmethyl-oxycarbonyl-based solid-phase peptide synthesis and radiolabeled with both 68Ga and 177Lu radionuclides for theranostic use. The systemic pharmacokinetics was done in healthy balb/c mice. The in vitro tumor cell binding affinity was determined on MCF7, T47D, and MDA-MB-231 breast cancer cell lines. In vivo tumor targeting and micro positron-emission tomography imaging was performed on nude mice with MCF7 breast tumor xenografts. Results: The leuprolide peptide was conveniently synthesized by solid-phase synthesis strategy and its identity and purity were validated by mass spectrometry and high-performance liquid chromatography. The peptide radiolabeled efficiently (˃94%) with both diagnostic (68Ga) and therapeutic (177Lu) radionuclides and displayed nanomolar binding potency to all three tested MCF7, T47D, and MDA-MB-231 cell lines. Fast and favorable pharmacokinetics was observed for 68Ga/177Lu-leuprolide in healthy Balb/c mice. In nude mice, 68Ga-leuprolide peptide exhibited rapid clearance from the blood circulation with low to moderate (up to 5% ID/g) uptake/retention by the major body organs. The accumulation in the estrogen receptor-positive MCF7 tumor was 2.24% ± 0.62% ID/g at 45 min p.i, with good tumor to blood and muscle uptake ratios. The radiolabeled peptide was excreted primarily through the renal pathway. Conclusion: The encouraging results of this initial study demonstrate that additional testing of this leuprolide peptide seems to be indicated because of its convincing potential to be a new agent for the management of breast carcinoma.