TY - JOUR
T1 - Copper-64 radiolabeling and biological evaluation of bifunctional chelators for radiopharmaceutical development
AU - De Silva, Ravindra A.
AU - Jain, Sandeep
AU - Lears, Kimberly A.
AU - Chong, Hyun Soon
AU - Kang, Chi Soo
AU - Sun, Xiang
AU - Rogers, Buck E.
N1 - Funding Information:
This work was supported by the Department of Radiation Oncology, Washington University School of Medicine and NIH grant R01 CA136695 . Drs. De Silva and Jain were supported by a DOE Integrated Research Training Program of Excellence in Radiochemistry (DE-SC0002032). Dr. Nilantha Bandara is thanked for his assistance in assembling of the manuscript.
Funding Information:
Financial Support: Supported by the Department of Radiation Oncology, Washington University School of Medicine, NIH grant RO1 CA136695 and a DOE Integrated Radiochemistry Research Project of Excellence Grant (DE- SC00002032 ).
PY - 2012/11
Y1 - 2012/11
N2 - Introduction: The development of novel bifunctional chelates for attaching copper-64 to biomolecules has been an active area of research for several years. However, many of these 64Cu-chelates have poor in vivo stability or harsh radiolabeling conditions. Methods: In this study, two triazacyclononane analogs; C-NE3TA (4-carboxymethyl-7-[2-(carboxymethyl-amino)-3-(4-nitro-phenyl)-propyl]-[1,4,7]triazo-nan-1-yl-acetic acid) and N-NE3TA (4-carboxymethyl-7-[2-[carboxymethyl-(4-nitro-benzyl)-amino]-ethyl]-[1,4,7]triazonan-1-yl-acetic acid) were evaluated for their labeling efficiency with 64Cu at room temperature and evaluated in vitro and in vivo. In vitro studies included complexation kinetics with Cu(II) using a spectrophotometric method and rat serum stability, while the in vivo biodistribution was evaluated using SCID mice. Results: C-NE3TA and N-NE3TA were labeled at >95% efficiency up to ~3.4Ci/μmol. Both C-NE3TA and N-NE3TA formed complexes with Cu(II) almost immediately, with the Cu(II) complexation by C-NE3TA being faster than the formation of Cu(II)-N-NE3TA. Both 64Cu-N-NE3TA and 64Cu-C-NE3TA were 96.1% and 90.5% intact after 48h incubation in rat serum, respectively. This is compared to 64Cu complexes of the control chelators, p-NH2-Bn-DOTA and p-NH2-Bn-NOTA, with 93.9% and 97.9% retention of 64Cu in the complex, respectively. In vivo evaluation of 64Cu-N-NE3TA and 64Cu-C-NE3TA demonstrates good clearance from normal tissues except for the liver, where 59% and 51% of the radioactivity is retained at 24h compared to 1h for 64Cu-N-NE3TA and 64Cu-C-NE3TA, respectively. This compares to 78% and 3% retention for 64Cu-p-NH2-Bn-DOTA and 64Cu-p-NH2-Bn-NOTA. Conclusions: These studies demonstrate that while N-NE3TA and C-NE3TA appear to be superior chelators for 64Cu than p-NH2-Bn-DOTA, they are not better than p-NH2-Bn-NOTA. Nevertheless, it may still be interesting to evaluate these chelators after conjugation to biomolecules.
AB - Introduction: The development of novel bifunctional chelates for attaching copper-64 to biomolecules has been an active area of research for several years. However, many of these 64Cu-chelates have poor in vivo stability or harsh radiolabeling conditions. Methods: In this study, two triazacyclononane analogs; C-NE3TA (4-carboxymethyl-7-[2-(carboxymethyl-amino)-3-(4-nitro-phenyl)-propyl]-[1,4,7]triazo-nan-1-yl-acetic acid) and N-NE3TA (4-carboxymethyl-7-[2-[carboxymethyl-(4-nitro-benzyl)-amino]-ethyl]-[1,4,7]triazonan-1-yl-acetic acid) were evaluated for their labeling efficiency with 64Cu at room temperature and evaluated in vitro and in vivo. In vitro studies included complexation kinetics with Cu(II) using a spectrophotometric method and rat serum stability, while the in vivo biodistribution was evaluated using SCID mice. Results: C-NE3TA and N-NE3TA were labeled at >95% efficiency up to ~3.4Ci/μmol. Both C-NE3TA and N-NE3TA formed complexes with Cu(II) almost immediately, with the Cu(II) complexation by C-NE3TA being faster than the formation of Cu(II)-N-NE3TA. Both 64Cu-N-NE3TA and 64Cu-C-NE3TA were 96.1% and 90.5% intact after 48h incubation in rat serum, respectively. This is compared to 64Cu complexes of the control chelators, p-NH2-Bn-DOTA and p-NH2-Bn-NOTA, with 93.9% and 97.9% retention of 64Cu in the complex, respectively. In vivo evaluation of 64Cu-N-NE3TA and 64Cu-C-NE3TA demonstrates good clearance from normal tissues except for the liver, where 59% and 51% of the radioactivity is retained at 24h compared to 1h for 64Cu-N-NE3TA and 64Cu-C-NE3TA, respectively. This compares to 78% and 3% retention for 64Cu-p-NH2-Bn-DOTA and 64Cu-p-NH2-Bn-NOTA. Conclusions: These studies demonstrate that while N-NE3TA and C-NE3TA appear to be superior chelators for 64Cu than p-NH2-Bn-DOTA, they are not better than p-NH2-Bn-NOTA. Nevertheless, it may still be interesting to evaluate these chelators after conjugation to biomolecules.
KW - Bifunctional chelators
KW - Biodistribution
KW - Copper-64
KW - Serum stability
UR - https://www.scopus.com/pages/publications/84867849110
U2 - 10.1016/j.nucmedbio.2012.05.009
DO - 10.1016/j.nucmedbio.2012.05.009
M3 - Article
C2 - 22743158
AN - SCOPUS:84867849110
SN - 0969-8051
VL - 39
SP - 1099
EP - 1104
JO - Nuclear Medicine and Biology
JF - Nuclear Medicine and Biology
IS - 8
ER -