Evaluation of p-Amidinophenyl Esters as Potential Antithrombotic Agents

Abstract

SummaryThree p-amidinophenyl esters have been synthesized and characterized as irreversible inhibitors of the vitamin-K dependent proteinases; factors IXa, Xa and thrombin (Turner et al. [4])+. In the present report we describe the in vitro and in vivo effects of these agents on standard coagulation tests in vitro and in blood from animals treated with the compounds. At a concentration of 500 μM, the three esters increased the activated partial thromboplastin time (PTT) of pooled human plasma 3 to 5-fold. The prothrombin time increased 1.4 to 3.7-fold under similar conditions. The p-amidinophenyl ester of cinnamic acid (CINN) showed the most pronounced effect on both assays. This ester also is the best inhibitor of human factors IXa and Xa, while the p-amidinophenyl ester of benzoic acid (BENZ) is a slightly better α-thrombin inhibitor (4). The effect of these esters on the thrombin clotting time correlated with in vitro kinetic measurements of α-thrombin inhibition rates. Both BENZ and CINN increased the assay endpoint more than 6-fold. The three esters also were studied using mouse plasma. A comparable effect on the PTT was noted. Intravenous administration of 300 αl of 1 mM CINN as a single bolus in mice caused a 2.3-fold increase in the PTT which remained 1.2-fold normal 2 h later. The BENZ and a-methyl-cinnamic acid (MECINN) esters were somewhat less effective as predicted from their in vitro effect on the PTT. This investigation and previous studies indicate that these compounds demonstrate low toxicity at therapeutic levels. It is concluded that the p-amidinophenyl esters may be useful in antithrombotic therapy.

Pharmacologic Aspects of the Development of Selective Synthetic Thrombin Inhibitors as Anticoagulants

“…[42][43][44][45] p-Amidinophenylesters may also inhibit thrombin and prolong clotting times. 46 FUT 175, chemically amidinonaphthyl-guanidinobenzoate, a rather nonselective proteinase inhibitor, is also proposed for anticoagulant and antithrombotic use. [47][48][49] The developments just mentioned show that several groups are going beyond the synthetic and biochemical work in this field and are evaluating the potential of various types of thrombin inhibitors as anticoagulant agents in vitro and in vivo.…”

The synthesis of arginylfluoroalkanes, their inhibition of trypsin and blood-coagulation serine proteinases and their anticoagulant activity

“…The potent Factor Xa inhibitor 1,2-bis-(5-amidinobenzofuran-2-yl)ethane also increases the APTT of human plasma 2-fold at 1.5 JM (Tidwell et al, 1980). Two other types of compounds that have been tested recently as antithrombotic agents are p-amidinophenyl esters (Turner et al, 1986;Pizzo et at., 1986) and isocoumarins. The p-amidinophenyl esters inhibit human thrombin and Factor Xa with kobS./[I] values of 0.2 x 104-2 x 10 M-1s and double the PT at 500 #M. Recently we have reported that 4-chloro-3-ethoxy-7-guanidinoisocoumarin can inhibit coagulation enzymes quite efficiently with kobs./[I] values of 2 x 104-50 x I04 M-1 s-1 and prolong the PT approx.…”

Thioester Chromogenic Substrates for Human Factor VIIa: Substituted Isocoumarins Are Inhibitors of Factor VIIa and In Vitro Anticoagulants

“…DABE (1,2-di[amidino-2-benzofuranyl)ethane) is a potent factor Xa inhibitor and shows anticoagulant activity in human plasma (9). In addition, pamidinophenyl esters inhibit factor IXa, factor Xa, and thrombin, and also are antithrombotic agents (10,11).…”