How Stabilizers and Peptide Design Keep Cancer-Imaging Compounds from Breaking Down

Researchers compared the stability of two lutetium-177-labeled peptides — the AMBA agonist and RM1 antagonist — that target the gastrin-releasing peptide receptor found on prostate cancer cells. They tested stability in acetate buffer and in sera from mice, dogs, and humans at different radioconcentrations and storage temperatures. They also tested whether adding ascorbic acid or gentisic acid could prevent degradation.

For peptide-based cancer imaging to work in the clinic, the radiolabeled peptide must remain stable long enough to reach the tumor and produce a clear image. This study addressed a practical barrier — figuring out how to keep these peptides from degrading — and identified both a better peptide candidate (antagonist over agonist) and effective stabilizers that could extend shelf life.

Targeted peptide imaging is a growing field in cancer diagnostics and theranostics — using the same peptide to both find and treat tumors. Stability is one of the biggest practical hurdles for getting peptide radiopharmaceuticals from the lab to the clinic. This work helps solve that problem for GRPR-targeting compounds, which are being developed for prostate cancer detection alongside the more established PSMA-targeting agents.

This is an in-vitro stability study — it tests how well the peptides hold up in buffer and blood serum, not how well they perform in living patients. No imaging or therapeutic outcomes were measured. The study focused on lutetium-177 labeling specifically, so results may differ with other radioisotopes.