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.
Department of Peptidomimetic Research, SmithKline Beecham Pharmaceuticals Research and Development, King of Prussia, Pennsylvania 19406-0939.
J
J
Samanen
F
F
Ali
T
T
Romoff
R
R
Calvo
E
E
Sorenson
J
J
Vasko
B
B
Storer
D
D
Berry
D
D
Bennett
M
M
Strohsacker
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