CP-70,030 and CP-75,998: The first non-peptide antagonists of bombesin and gastrin releasing peptide

PD 176252--the first high affinity non-peptide gastrin-releasing peptide (BB2) receptor antagonist

In this paper we describe the development of a novel series of non-peptide, "balanced" neuromedin-B preferring (BB1)/gastrin-releasing peptide preferring (BB2) receptor ligands as exemplified by PD 176252. PD 176252, which exhibits nanomolar affinity for both the BB1 (Ki = 0.15 nM) and BB2 (Ki = 1.0 nM) receptors, has been demonstrated to be a competitive antagonist at these bombesin receptor subtypes.

Gastrin releasing peptide-preferring bombesin binding sites in human lung

Characterization of bombesin binding sites in healthy human lung was performed through direct binding techniques. There was limited binding in the absence of trypsin and chymotrypsin inhibitors, suggesting important activities of both enzymes in human lung and/or increased sensitivity of the bombesin sites toward them. In human lung membranes, bombesin, gastrin releasing peptide (GRP) and GRP-preferring bombesin receptor antagonists displaced [125I-Tyr4]bombesin binding with high affinities (36-177 nM), whereas neuromedin B possessed a lower affinity of 2878 nM. [D-F5Phe6,D-Ala11]bombesin-(6-13)-methyl ester, the most active GRP-preferring bombesin antagonist as yet reported, had the highest affinity among all antagonists tested whereas neuromedin B had the lowest affinity. These data demonstrate that the bombesin binding sites in the human lung are of the GRP-preferring type.