Therapeutic Efficacy of 177Lu-Labeled A20FMDV2 Peptides Targeting ανß6.

ABSTRACT

Integrin ανß6 promotes migration and invasion of cancer cells, and its overexpression often correlates with poor survival. Therefore, targeting ανß6 with radioactive peptides would be beneficial for cancer imaging and therapy. Previous studies have successfully developed radiotracers based on the peptide A20FMDV2 that showed good binding specificity for ανß6. However, one concern of these ανß6 integrin-targeting probes is that their rapid blood clearance and low tumor uptake would preclude them from being used for therapeutic purposes. In this study, albumin binders were used to increase tumor uptake for therapeutic applications while the non-albumin peptide was evaluated as a potential positron emission tomography (PET) imaging agent. All peptides used the DOTA chelator for radiolabeling with either 68Ga for imaging or 177Lu for therapy. PET imaging with [68Ga]Ga-DOTA-(PEG28)2-A20FMDV2 revealed specific tumor uptake in ανß6-positive tumors. Albumin-binding peptides EB-DOTA-(PEG28)2-A20FMDV2 and IBA-DOTA-(PEG28)2-A20FMDV2 were radiolabeled with 177Lu. Biodistribution studies in normal mice showed longer blood circulation times for the albumin binding peptides compared to the non-albumin peptide. Therapy studies in mice demonstrated that both 177Lu-labeled albumin binding peptides resulted in significant tumor growth inhibition. We believe these are the first studies to demonstrate the therapeutic efficacy of a radiolabeled peptide targeting an ανß6-positive tumor.