Peptide-Based Imaging Probe Successfully Detects HER2-Positive Tumors in Mice

The ZHER2:342 Affibody molecule was synthesized using solid-phase peptide synthesis (Fmoc/tBu chemistry). A chelating peptide sequence (Gly-(d)Ala-Gly-Gly) was attached to enable technetium-99m labeling. Labeling efficiency and stability were assessed by reversed-phase HPLC. Biodistribution and imaging studies were performed in nude mice bearing either HER2-positive (SKOV-3) or HER2-negative (MDA-MB-231) tumor xenografts.

Knowing whether a tumor is HER2-positive is critical for selecting the right cancer treatment, but current methods typically require a tissue biopsy. A non-invasive imaging probe that can detect HER2 status throughout the body could revolutionize cancer diagnosis and treatment monitoring — allowing doctors to see HER2 expression in real time without surgery, and potentially detecting metastases that biopsies would miss.

Affibody molecules represent a class of engineered peptide-based binding proteins that are much smaller than antibodies, giving them advantages for molecular imaging including faster tumor penetration, quicker blood clearance, and higher contrast images. This work contributes to the broader development of peptide-based diagnostics that could complement or replace antibody-based approaches for cancer detection and monitoring.

This is a preclinical study in nude mice with implanted human tumor xenografts, which does not fully replicate human cancer biology. Only two cell lines were tested (one HER2-positive, one HER2-negative). The study did not assess imaging in the presence of more complex anatomical structures or in larger animals. Translation to human clinical use would require extensive further development including toxicity studies and regulatory approval.