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Preliminary Therapy Evaluation of Ac-225-DOTA-c (RGDyK) Demonstrates that Cerenkov Radiation Derived from Ac-225 Daughter Decay Can Be Detected by Optical Imaging for In Vivo Tumor Visualization
Journal article   Open access   Peer reviewed

Preliminary Therapy Evaluation of Ac-225-DOTA-c (RGDyK) Demonstrates that Cerenkov Radiation Derived from Ac-225 Daughter Decay Can Be Detected by Optical Imaging for In Vivo Tumor Visualization

Darpan N. Pandya, Roy Hantgan, Mikalai M. Budzevich, Nancy D. Kock, David L. Morse, Izadora Batista, Akiva Mintz, King C. Li and Thaddeus J. Wadas
Theranostics, Vol.6(5), pp.698-709
01/01/2016
DOI: 10.7150/thno.14338
PMCID: PMC4805664
PMID: 27022417
url
https://doi.org/10.7150/thno.14338View
Published (Version of record) Open Access

Abstract

The theranostic potential of Ac-225-based radiopharmaceuticals continues to increase as researchers seek innovative ways to harness the nuclear decay of this radioisotope for therapeutic and imaging applications. This communication describes the evaluation of Ac-225-DOTA-c(RGDyK) in both biodistribution and Cerenkov luminescence imaging (CLI) studies. Initially, La-DOTA-c(RGDyK) was prepared as a non-radioactive surrogate to evaluate methodologies that would contribute to an optimized radiochemical synthetic strategy and estimate the radioactive conjugate's affinity for alpha(v)beta(3), using surface plasmon resonance spectroscopy. Surface plasmon resonance spectroscopy studies revealed the IC50 and K-i of La-DOTA-c(RGDyK) to be 33 +/- 13 nM and 26 +/- 11 nM, respectively, and suggest that the complexation of the La3+ ion to the conjugate did not significantly alter integrin binding. Furthermore, use of this surrogate allowed optimization of radiochemical synthesis strategies to prepare Ac-225-DOTA-c(RGDyK) with high radiochemical purity and specific activity similar to other Ac-225-based radiopharmaceuticals. This radiopharmaceutical was highly stable in vitro. In vivo biodistribution studies confirmed the radiotracer's ability to target alpha(v)beta(3) integrin with specificity; specificity was detected in tumor-bearing animals using Cerenkov luminescence imaging. Furthermore, tumor growth control was achieved using non-toxic doses of the radiopharmaceutical in U87mg tumor-bearing nude mice. To our knowledge, this is the first report to describe the CLI of alpha(v)beta(+)(3) tumors in live animals using the daughter products derived from Ac-225 decay in situ. This concept holds promise to further enhance development of targeted alpha particle therapy.
Life Sciences & Biomedicine Medicine, Research & Experimental Research & Experimental Medicine Science & Technology

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