Dataset Information

Efficient 1-step radiolabeling of monoclonal antibodies to high specific activity with 225Ac for ?-particle radioimmunotherapy of cancer.

ABSTRACT: Targeted ?-particle radiation using the radioisotope (225)Ac is a promising form of therapy for various types of cancer. Historic obstacles to the use of (225)Ac have been the difficulty in finding suitable chelators to stably attach it to targeting vehicles such as peptides and monoclonal antibodies, the low specific activities of the products, and the lack of cost-effective radiolabeling procedures. We initially solved the first problem with a procedure involving 2 chemical steps that has been used as a standard in preclinical and clinical studies. However, this procedure involves the loss of 90% of the input (225)Ac. A more efficient, economical process is needed to facilitate the more widespread use of (225)Ac.We conjugated representative antibodies with 2 forms of DOTA as well as other chelators as controls. We developed conditions to radiolabel these constructs in 1 chemical step and characterized their stability, immunoreactivity, biodistribution, and therapeutic efficacy in healthy and tumor-bearing mice.DOTA-antibody constructs were labeled to a wide range of specific activities in 1 chemical step at 37°C. Radiochemical yields were approximately 10-fold higher, and specific activities were up to 30-fold higher than with the previous approach. The products retained immunoreactivity and were stable to serum challenge in vitro and in mice. Labeling kinetics of DOTA-antibody constructs linked through a benzyl isothiocyanate linkage were more favorable than those linked through an N-hydroxysuccinimide linkage. Tissue distribution was similar but not identical between the constructs. The constructs produced specific therapeutic responses in a mouse model of acute myeloid leukemia.We have characterized an efficient, 1-step radiolabeling method that produces stable, therapeutically active conjugates of antibodies with (225)Ac at high specific activity. We propose that this technology greatly expands the possible clinical applications of (225)Ac monoclonal antibodies.

SUBMITTER: Maguire WF

PROVIDER: S-EPMC4406251 | biostudies-literature | 2014 Sep

REPOSITORIES: biostudies-literature

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Publications

Efficient 1-step radiolabeling of monoclonal antibodies to high specific activity with 225Ac for α-particle radioimmunotherapy of cancer.

Maguire William F WF McDevitt Michael R MR Smith-Jones Peter M PM Scheinberg David A DA

Journal of nuclear medicine : official publication, Society of Nuclear Medicine 20140630 9

<h4>Unlabelled</h4>Targeted α-particle radiation using the radioisotope (225)Ac is a promising form of therapy for various types of cancer. Historic obstacles to the use of (225)Ac have been the difficulty in finding suitable chelators to stably attach it to targeting vehicles such as peptides and monoclonal antibodies, the low specific activities of the products, and the lack of cost-effective radiolabeling procedures. We initially solved the first problem with a procedure involving 2 chemical ...[more]

PMID: 24982438

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Project description:To develop imaging and therapeutic agents, antibodies are often conjugated randomly to a chelator/radioisotope or drug using a primary amine (NH2) of lysine or sulfhydryl (SH) of cysteine. Random conjugation to NH2 or SH groups can require extreme conditions and may affect target recognition/binding and must therefore be tested. In the present study, nimotuzumab was site-specifically labeled using ∆N-SpyCatcher/SpyTag with different chelators and radiometals. Nimotuzumab is a well-tolerated anti-EGFR antibody with low skin toxicities. First, ΔN-SpyCatcher was reduced using tris(2-carboxyethyl)phosphine (TCEP), which was followed by desferoxamine-maleimide (DFO-mal) conjugation to yield a reactive ΔN-SpyCatcher-DFO. The ΔN-SpyCatcher-DFO was reacted with nimotuzumab-SpyTag to obtain stable nimotuzumab-SpyTag-∆N-SpyCatcher-DFO. Radiolabeling was performed with 89Zr, and the conjugate was used for the in vivo microPET imaging of EGFR-positive MDA-MB-468 xenografts. Similarly, ∆N-SpyCatcher was conjugated to an eighteen-membered macrocyclic chelator macropa-maleimide and used to radiolabel nimotuzumab-SpyTag with actinium-225 (225Ac) for in vivo radiotherapy studies. All constructs were characterized using biolayer interferometry, flow cytometry, radioligand binding assays, HPLC, and bioanalyzer. MicroPET/CT imaging showed a good tumor uptake of 89Zr-nimotuzumab-SpyTag-∆N-SpyCatcher with 6.0 ± 0.6%IA/cc (n = 3) at 48 h post injection. The EC50 of 225Ac-nimotuzumab-SpyTag-∆N-SpyCatcher and 225Ac-control-IgG-SpyTag-∆N-SpyCatcher against an EGFR-positive cell-line (MDA-MB-468) was 3.7 ± 3.3 Bq/mL (0.04 ± 0.03 nM) and 18.5 ± 4.4 Bq/mL (0.2 ± 0.04 nM), respectively. In mice bearing MDA-MB-468 EGFR-positive xenografts, 225Ac-nimotuzumab-SpyTag-∆N-SpyCatcher significantly (p = 0.0017) prolonged the survival of mice (64 days) compared to 225Ac-control IgG (28.5 days), nimotuzumab (28.5 days), or PBS-treated mice (30 days). The results showed that the conjugation and labeling using SpyTag/∆N-SpyCatcher to nimotuzumab did not significantly (p > 0.05) alter the receptor binding of nimotuzumab compared with a non-specific conjugation approach. 225Ac-nimotuzumab-SpyTag-∆N-SpyCatcher was effective in vitro and in an EGFR-positive triple negative breast cancer xenograft model.

Dataset Information

Efficient 1-step radiolabeling of monoclonal antibodies to high specific activity with 225Ac for ?-particle radioimmunotherapy of cancer.

Publications

Efficient 1-step radiolabeling of monoclonal antibodies to high specific activity with 225Ac for α-particle radioimmunotherapy of cancer.

Similar Datasets

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