Automated and manual synthesis of [⁶⁸Ga]Ga-DOTA-4AH29 intended for PET-imaging of FAP-expression

Fibroblast activation protein is a well-established target for tumour imaging, and single-domain antibodies (sdAb) offer favourable pharmacokinetic properties for PET applications. However, the translation of sdAb-based radiotracers into robust and clinically applicable manufacturing processes remains limited. Previously, preclinical protocol for the production of [⁶⁸Ga]Ga-DOTA-4AH29 has been reported. In this study, this process was adapted for clinical use. Both a manual, kit-based approach and automated synthesis on two different platforms were developed. Process robustness was assessed through a stress study evaluating key parameters, and compatibility with two ⁶⁸Ga generator systems was investigated.

Efficient radiolabelling was achieved at 50 °C for 10 min, with radiochemical conversion exceeding 90% and no need for purification. Both automated and manual processes showed consistent performance, with radiochemical purities of 99.5 ± 0.5% (n = 9) and 96.3 ± 1.5% (n = 8) as determined by iTLC and SE-HPLC respectively, with associated non-decay-corrected radiochemical yields of 78.3 ± 3.3% (n = 9) and 76.9 ± 2.1% (n = 8). The main source of activity loss was the radioactive decay of ⁶⁸Ga.The process remained stable across a range of activities and buffer conditions. Comparable results were obtained with both ⁶⁸Ga generator systems, with no observable impact on product quality. The final product was stable for at least 3 h at RT, with preserved binding capacity.

A robust and reproducible manufacturing process for [⁶⁸Ga]Ga-DOTA-4AH29 was established, supporting both automated and manual clinical production. This approach will facilitate broader access to sdAb-based PET imaging across clinical centres.