Advancing infection imaging: A one-⁠step radioformulation strategy using antimicrobial peptide cold kit

For early detection of infections, timely treatment, and to help limit the growing problem of antibiotic resistance, there is a need for sensitive and specific infection imaging agents. Additionally, such formulations should be simple to prepare and cost-effective to support clinical translation. With this objective, an extemporaneous formulation of an infection imaging agent was prepared using a cold kit of Ubiquicidin (UBI) fragment enabling the detection of focal infections through positron emission tomography (PET).

A single-vial kit for the preparation of [⁶⁸Ga] Ga-NODAGA-UBI (29-41) was developed using in-house synthesized UBI (29-41) peptide conjugated to a suitable chelator for radiolabeling with positron emitter, Gallium-68. Six batches of cold kits were prepared and subjected to quality control evaluation to ensure reproducibility of the radiotracer formulation.

Patient doses of [⁶⁸Ga] Ga-NODAGA-UBI (29-41) were successfully prepared from the cold kits with high radiochemical purity. The radiolabeled formulation demonstrated stability in both serum and saline. In vitro studies with Staphylococcus aureus and in vivo evaluations through biodistribution and imaging in infection-bearing animal models showed significant uptake of the tracer at the sites of infection.

A reliable cold kit formulation of UBI (29-41) was successfully developed, enabling rapid and convenient preparation of [⁶⁸Ga] Ga-NODAGA-UBI (29-41) in hospital radiopharmacies. The availability of a cold kit for preparing the radioformulation is expected to accelerate multicentric clinical trials and support data generation to confirm the potential of [⁶⁸Ga] Ga-NODAGA-UBI (29-41) for detecting focal infections using PET.