Arg-Gly-Asp constrained within cyclic pentapoptides 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 or platelet receptor αIIbβ3 to fibrinogen. NMR studies of the two most active cyclic peptides showed for both an all-trans conformation with a βII′ and γ turn. Subtle conformational differences, however, exist between both peptides and may contribute to selectivity or inhibition.