Arg-Gly-Asp constrained within cyclic pentapeptides. Strong and selective inhibitors of cell adhesion to vitronectin and laminin fragment P1.

Cyclic Arg-Gly-Asp-Phe-Val peptides with either D-Phe or D-Val residues were 20- to more than 100-fold better inhibitors of cell adhesion to vitronectin and/or laminin fragment P1 when compared to a linear variant or Gly-Arg-Gly-Asp-Ser. No or only little increase in inhibitory capacity was observed for fibronectin adhesion and for the binding of platelet receptor alpha IIb beta 3 to fibrinogen. NMR studies of the two most active cyclic peptides showed for both an all-trans conformation with a beta II' and gamma turn. Subtle conformational differences, however, exist between both peptides and may contribute to selectivity of inhibition.