Design of selective thrombin inhibitors based on the (R)-Phe-Pro-Arg sequence.

Potent and selective inhibitors of thrombin were sought based on the (R)-Phe-Pro-Arg sequence. The objective was to generate similar binding interactions to those achieved by potent competitive inhibitors of the argatroban type, so eliminating the need for covalent interaction with the catalytic serine function, as utilized by aldehyde and boronic acid type inhibitors. Improving the S(1) subsite interaction by substitution of arginine with a 4-alkoxybenzamidine residue provided potent lead 2 (K(i) = 0.

Antithrombotic activity in vivo of SDZ 217-766, a low-molecular weight thrombin inhibitor in comparison to heparin.

Antithrombotic potency of SDZ 217-766, a potent inhibitor of thrombin and other trypsin-like serine proteases, was studied in comparison with heparin in rat models of thrombin induced lung platelet accumulation, of thrombosis in arterio-venous shunt, and of venous thrombosis induced by tissue factor. Thrombin-induced platelet accumulation in the lung was inhibited dose-dependently by SDZ 217-766 following intravenous (i.v.

Platelet aggregation and fibrinogen binding in human, rhesus monkey, guinea-pig, hamster and rat blood: activation by ADP and a thrombin receptor peptide and inhibition by glycoprotein IIb/IIIa antagonists.

Platelet aggregation and fibrinogen binding in whole blood, induced either by ADP or by a 14 amino acid peptide mimicking an N-terminal region of the platelet thrombin receptor (TRP, thrombin receptor activating peptide), have been studied with blood from different species. Aggregation was assessed by counting the number of single platelets in blood before und after addition of the agonist with an automated cell counter. Both ADP (0.

Effects of a monoclonal antibody to glycoprotein IIb/IIIa (P256) and of enzymically derived fragments of P256 on human platelets.

The anti-platelet monoclonal antibody P256 is currently undergoing development for in vivo detection of thrombus. We have examined the actions of P256 and two fragments on human platelet function. P256, and its divalent fragment, caused aggregation at concentrations of 10(-9)-3 x 10(-8) M.

Measurement of fibrinogen binding to platelets in whole blood by flow cytometry: a micromethod for the detection of platelet activation.

Platelet fibrinogen binding in whole blood has been measured in vitro by flow cytometry using a commercially available, fluorescein isothiocyanate (FITC)-conjugated polyclonal antifibrinogen antibody. Fibrinogen-antifibrinogen immune complexes were formed in experimental conditions approaching antigen-antibody equivalence, but optimal reaction conditions in which their formation was prevented or minimized could be achieved. Immune complex formation was associated with fibrinogen binding to unstimulated platelets but did not significantly affect ADP-induced fibrinogen binding.