Antibody and Nanobody Radiolabeling with Copper-64: Solid vs. Liquid Target Approach

Abstract

Antibody and nanobody-based copper-64 radiopharmaceuticals are increasingly being proposed as theranostic tools in multiple human diseases. While the production of copper-64 using solid targets has been established for many years, its use is limited due to the complexity of solid target systems, which are available in only a few cyclotrons worldwide. In contrast, liquid targets, available in virtually in all cyclotrons, constitute a practical and reliable alternative. In this study, we discuss the production, purification, and radiolabeling of antibodies and nanobodies using copper-64 obtained from both solid and liquid targets. Copper-64 production from solid targets was performed on a TR-19 cyclotron with an energy of 11.7 MeV, while liquid target production was obtained by bombarding a nickel-64 solution using an IBA Cyclone Kiube cyclotron with 16.9 MeV on target. Copper-64 was purified from both solid and liquid targets and used to radiolabel NODAGA-Nb, NOTA-Nb, and DOTA-Trastuzumab conjugates. Stability studies were conducted on all radioimmunoconjugates in mouse serum, PBS, and DTPA. Irradiation of the solid target yielded 13.5 ± 0.5 GBq with a beam current of 25 ± 1.2 μA and an irradiation time of 6 h. On the other hand, irradiation of the liquid target resulted in 2.8 ± 1.3 GBq at the end of bombardment (EOB) with a beam current of 54.5 ± 7.8 μA and an irradiation time of 4.1 ± 1.3 h. Successful radiolabeling of NODAGA-Nb, NOTA-Nb, and DOTA-Trastuzumab with copper-64 from both solid and liquid targets was achieved. Specific activities (SA) obtained with the solid target were 0.11, 0.19, and 0.33 MBq/μg for NODAGA-Nb, NOTA-Nb, and DOTA-trastuzumab, respectively. For the liquid target, the corresponding SA values were 0.15, 0.12, and 0.30 MBq/μg. Furthermore, all three radiopharmaceuticals demonstrated stability under the testing conditions. While solid targets have the potential to produce significantly higher activity in a single run, the liquid process offers advantages such as speed, ease of automation, and the feasibility of back-to-back production using a medical cyclotron. In this study, successful radiolabeling of antibodies and nanobodies was achieved using both solid and liquid targets approaches. The radiolabeled compounds exhibited high radiochemical purity and specific activity, rendering them suitable for subsequent in vivo pre-clinical imaging studies.

Neurotensin (8-13) and Neuromedin N Neuropeptides Radiolabelling with Copper-64 Produced on Solid or Liquid Targets

“…Copper-64 (LT) production on the IBA Cyclone Kiube Variable Energy cyclotron and the post-irradiation processing were previously published [ 11 ]. In brief, a 3–5 h irradiation time of ~100 mg enriched nickel-64 with 16.9 MeV protons on target (extracted energy 18 MeV) led to an average activity of 3.7 ± 0.2 GBq at EOB, (above 12 MBq/μAh).…”

“…Compared with previously reported studies, the [ 64 Cu]CuCl 2 solutions were prepared with higher activities and in higher radioactive concentrations [ 11 , 21 ]. For ST, the radioactive concentration previously obtained was 90 ± 3.4 MBq/μAh (at EOB), while in this study we increased it to 117.3 ± 14 MBq/μAh (at EOB).…”

“…The question is, if both routes are feasible for high-quality radiopharmaceutical preparation, especially when the resulting solutions are used for radiolabelling of specific targeting molecules. In our previous study we demonstrated the suitability of both liquid and solid target approaches to radiolabel antibodies and nanobodies with comparable specific activities and stability [ 11 ]. The present study was designed to optimise and compare the radiolabelling processes of neuropeptides using [ 64 Cu]CuCl 2 prepared by solid and liquid targets routes, respectively, and investigate the stability and affinity of the resulting radiolabelled peptides.…”

“…Neurotensin receptors were identified and localised in tumour cells of Ewing's sarcomas, meningiomas, astrocytomas, medulloblastomas, medullary thyroid cancers, and small cell lung cancers [18]. A pseudopeptide, the smallest active fragment of neurotensin, Neurotensin (8)(9)(10)(11)(12)(13) was developed to thwart the rapid in vivo degradation of full-chain peptide, bearing changes which stabilise the molecule against enzymatic degradation. NT (8)(9)(10)(11)(12)(13) binds to the same sites, with a higher affinity than NT does [19].…”

“…A pseudopeptide, the smallest active fragment of neurotensin, Neurotensin (8)(9)(10)(11)(12)(13) was developed to thwart the rapid in vivo degradation of full-chain peptide, bearing changes which stabilise the molecule against enzymatic degradation. NT (8)(9)(10)(11)(12)(13) binds to the same sites, with a higher affinity than NT does [19]. NN is a good marker of human colon cancer, in addition to NT, and recent studies suggest it might exert an autocrine-positive effect on human colon cancer growth [20].…”