Radiosynthesis of 64Cu-labelled cetuximab for clinical use

Objectives Cetuximab, a chimeric human-mouse monoclonal antibody against epidermal growth factor receptor (EGFR), shows anti-tumor effects by binding EGFR and inhibiting proliferation of tumor cells. We have optimized the synthesis condition of radiolabelled antibody for clinical use, and demonstrated 64Cu-labeled trastuzumab PET imaging in the patients with breast cancer at SNMMI 2012 annual meeting. In this presentation, we demonstrate the synthesis of 64Cu-labelled cetuximab and its quality evaluation for clinical use.

Methods The 64Ni (p, n) 64Cu nuclear reaction was performed with 12 MeV proton irradiation for 2 h using a small medical cyclotron. The produced 64Cu was purified by anion-exchange resin to be 64CuCl2 solution. Cetuximab IgG (Erbitax®) was added to tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) mono N-hydroxysuccinimide ester dissolved in water. After 3 h, crude DOTA-cetuximab was purified by PD-10 column, and phosphate buffered saline (PBS) buffer including DOTA-cetuximab was exchanged for sodium acetate buffer by filtration. The purified 64CuCl2 solution was added with DOTA-cetuximab in acetic acid buffer and conjugated for 1 h. After the reaction, 64Cu-DOTA-cetuximab was filtered through a 0.22 μm filter in a sterile vial. The product was checked the physiological and chemical quality including specific activity, and examined the affinity to ErbB1 protein. All procedures were carried out under laminar air flow (Class 100 air).

Results 64Cu-DOTA-cetuximab injections passed quality control testing against specifications: radioactivity (>150 MBq), volume (4-6 mL), half-time (12.4-13.0 h), clarity (clear) and color (none), pH (5.0-8.0), radiochemical purity (>95 %), protein abundance (<100 μg), specific activity (>100 GBq/μmol), ErbB1 immunoreactivity (< Kd: 1 nM), sterility (Japanese Pharmacopoeia), and endotoxin (< 0.25 EU/mL).

Conclusions 64Cu-DOTA cetuximab injections synthesized by our procedure passed all of quality control testing for clinical use.