FASTlab Radiosynthesis of the 18 F-labelled HER2-binding Affibody molecule [18 F]GE-226

An 18 F-labelled human epidermal growth factor receptor (HER2) receptor binding radiotracer is a potential tool to non-invasively identify HER2 positive tumour lesions in subjects with recurrent metastatic breast cancer. Having explored the manual radiochemistry to conjugate the Affibody molecule ZHER2:2891 with [18 F]4-fluorobenzaldehyde, we have developed and optimised a full protocol for the automated GE FASTlab synthesiser. Our chemometric model predicted the best radiochemical purity for a short conjugation time (2.8 minutes), a low temperature (65°C), and a medium Affibody molecule precursor amount (5.5 mg). Under these optimised conditions, [18 F]GE-226 was produced after solid-phase extraction purification with activity yield of 30% ± 7 (n = 18) and a radiochemical purity of 94% ± 2 (n = 18). The synthesis and purification was complete after 43 minutes and provided apparent molar activities of 12 to 30 GBq/μmol (n = 12) at the end of synthesis.