Development of a small RGD peptide fibrinogen receptor antagonist with potent antiaggregatory activity in vitro.
The development of potent antithrombotic agents from the fibrinogen platelet receptor binding sequences Fg-alpha 572-575 -Arg-Gly-Asp-Ser- and Fg-gamma 400-411 -HHLGGAKQAGDV, believed to be a cryptic RGD-type sequence, is described. The tetrapeptide Ac-RGDS-NH2 itself is capable of inhibiting platelet aggregation in vitro at high concentrations, IC50 91.3 +/- 0.1 microM [in vitro antiaggregatory activity employing dog platelet rich plasma (PRP)/ADP], due to low platelet fibrinogen receptor affinity, Ki 2.9 +/- 1.9 microM (purified, reconstituted human platelet GPIIb/IIIa), relative to fibrinogen, Ki 38.0 +/- 6.0 nM. The peptide is also unstable to plasma, suffering total loss of in vitro activity upon incubation in PRP for 3 h (T1/2 90 min). Only modest improvements in potency were achieved with linear analogues of Ac-RGDS-NH2, while dramatic results were achieved with cyclic analogues, culminating in the cyclic disulfide Ac-cyclo-S,S-[Cys-(N alpha-Me)Arg-Gly-Asp-Pen]-NH2 (SK&F 106760) with improved plasma stability (100% activity after 3 h), affinity (Ki 58 +/- 20 nM purified human receptor), and potency (IC50 0.36 +/- 0.4 microM dog PRP/ADP). The affinity of this peptide is 2 orders of magnitude greater than that of Ac-RGDS-NH2. The affinity of the analogue is also comparable to fibrinogen. This peptide constitutes a first potent small peptide entry into the class of novel antithrombotic agents called fibrinogen receptor antagonists.
Samanen
J
J
Department of Peptidomimetic Research, SmithKline Beecham Pharmaceuticals Research and Development, King of Prussia, Pennsylvania 19406-0939.
Ali
F
F
Romoff
T
T
Calvo
R
R
Sorenson
E
E
Vasko
J
J
Storer
B
B
Berry
D
D
Bennett
D
D
Strohsacker
M
M
D000595:Amino Acid Sequence; D000818:Animals; D003500:Cyclization; D004285:Dogs; D004355:Drug Stability; D005340:Fibrinogen / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D010974:Platelet Aggregation; D010975:Platelet Aggregation Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013329:Structure-Activity Relationship
D009842:Oligopeptides; D010446:Peptide Fragments; D010456:Peptides, Cyclic; D010975:Platelet Aggregation Inhibitors; D010980:Platelet Membrane Glycoproteins; C071275:SK&F 106760; D005340:Fibrinogen; C046617:arginyl-glycyl-aspartyl-serine