Radiolabeled peptide conjugates for targeting of the bombesin receptor superfamily subtypes

Research laboratories around the world are currently focusing their efforts toward the development of radiometallated, site-directed, diagnostic/therapeutic agents based upon small peptides such as octreotide, neurotensin, α-melanocyte stimulating hormone, vasointestinal peptide and others. Bombesin (BBN) or derivatives of bombesin are also of significant interest. Bombesin is a 14-amino-acid peptide with very high affinity for the BB2 or gastrin-releasing peptide receptor (GRPr). Over-expression of the GRPr on a variety of human cancers (i.e., breast, prostate, pancreatic, small cell lung, etc.) provides potential efficacy toward development of radiometallated BBN derivatives for targeting and, hence, diagnosis/treatment of these specific diseases. New derivatives are being developed that are also capable of targeting the BB1 and BB3 receptor subtypes that are over-expressed on cancer cells. This review highlights some of the more recent developments toward design of BBN receptor-specific radiopharmaceuticals that have taken place over the past 2 years.