Scott I. Klein

Constrained β-alanine based GpIIb/IIIa antagonists

The concepts of centrally constrained and peptide based fibrinogen receptor antagonists have been successfully combined into a single series of analogs which have been demonstrated to be potent inhibitors of platelet aggregation.

O-benzyl hydroxyproline as a bioisostere for Phe-Pro: Novel dipeptide thrombin inhibitors

Abstract A series of analogs were prepared based on the known thrombin inhibitor PPACK, in which the D-Phe-Pro dipeptide has been replaced by trans-4-O-benzyl hydroxyproline. One of these analogs is a more potent inhibitor of thrombin, and is more selective, than PPACK itself.

Anti-thrombotic activity of RG13965, a novel platelet fibrinogen receptor antagonist

RG13965, a pseudotetrapeptide analogue of Arg-Gly-Asp (RGD), inhibited collagen-induced dog, monkey, human, hamster, mouse, and pig platelet aggregation in vitro with IC50 values of 3.7, 4.6, 6.3, 126, 136 and 1600 microM, respectively. RG13965 (3, 10, and 30 mg/kg, i.v.) decreased the incidence of collagen/epinephrine-induced thrombosis in mice from 90% in untreated animals to 63, 37, and 0%, respectively. In hamsters, RG13965 (10 and 30 mg/kg, i.v.) prolonged the time required for formation of a hemostatic plug in severed mesenteric arteries by 1.6- and 3.6-fold, respectively. In a canine model of repetitive platelet thrombus formation in the coronary artery, RG13965 (0.1, 0.3, and 1 mg/kg, i.v.) reversibly inhibited cyclic flow reductions (CFRs) and inhibited ADP-induced ex vivo platelet aggregation by 29, 57, and 77%, respectively. RG13965 (1 mg/kg) completely inhibited CFRs for at least 40 min. Platelet count was not altered at any dose and template bleeding time was prolonged modestly (1.8-fold) at only the highest dose. RG13965 dose-dependently and reversibly inhibited thrombus formation at doses which did not completely inhibit ex vivo platelet aggregation and only modestly prolonged template bleeding time.

Non-peptide fibrinogen receptor antagonists based upon a 4-substituted piperidine scaffold

Abstract Structure-activity relationships developed from work with peptide based fibrinogen receptor antagonists have been successfully applied to the development of simple and highly potent nonpeptide agents of the same class.

Conformationally flexible platelet aggregation inhibitors based on the tetrapeptide Arg-Gly-Asp-Arg

Summary A series of nonpeptide fibrinogen receptor antagonists based upon the tetrapeptide Arg-Gly-Asp-Arg were prepared. These relatively simple derivatives incorporate a high degree of conformational flexibility that was anticipated to allow them to attain the requisite conformation for binding to the platelet fibrinogen receptor. Optimization of the distances between the required acidic and basic functional groups led eventually to compound 7, which is a one hundred-fold more potent inhibitor of platelet aggregation than the peptide it is based upon.