Factor Xa (FXa) has materialized as a key enzyme for the intervention of the blood coagulation cascade and for the development of new antithrombotic agents. FXa is the lone enzyme responsible for the production of thrombin and therefore is an attractive target for the control of thrombus formation. We have designed and synthesized a unique series of quinoxalinone FXa inhibitors. This series resulted in 3-[4-[5-((2S,6R)-2,6-dimethylpiperidin-1-yl)pentyl]-3-oxo-3,4-dihydroquinoxolin-2-yl]benzamidine (35) with 0.83 nM activity against FXa and excellent selectivity over similar serine proteases. An X-ray crystal structure of compound 35 bound to trypsin along with molecular modeling has led to a predicted binding conformation of compound 35 in FXa. Compound 35 has also been proven to be efficacious in vivo in both the rabbit veno-venous shunt and dog electrolytic injury models. In addition, it was shown that compound 35 did not significantly increase bleeding times in a rabbit model except at the highest doses and plasma concentrations were elevated in a dose dependent manner following a bolus dose and continuous intravenous infusion.

A selective nonpeptide endotheli n A (ETA) receptor antagonist, CI-1020, was administered to beagle dogs intravenously (iv) for 4 hours to 4 weeks. One animal/sex received CI-1020 at 1 mg/kg/hr intravenousl y for 4, 8, or 24 hours to investigate onset of arteriopathy. Control animals (1/sex) received the vehicle only. To determine reversibility of arteriopathy, 8 dogs/sex were given CI-1020 at 1 mg/kg/hr for 4 days. Two dogs/sex were sacri ced 1, 3, 8, and 29 days following cessation of infusion. Lesion developmen t with prolonged exposure was investigated in 1 male dog. It was given CI-1020 by iv bolus at 120 mg/kg/day for 4 weeks and Monastral blue dye was administered iv to facilitate localization of vascular lesions. Coronary blood ow was determined in 4 dogs infused with CI-1020 at 0.3, 3, and 30 mg/kg for one hour at each dose. Macroscopically, hemorrhage or blue discoloration of Monastral blue was noted in the extramural coronary arteries along the coronary groove and atrium. Histologically, the earliest coronary changes were noted in animals sacri ced after 24 hours of treatment and characterized by medial hemorrhage and necrosis with a few in ltrating neutrophils. In the reversibility study, incidence and severity of arteriopathy was dependen t on time of sacri ce following cessation of infusion. Acute necrotizing in ammation of arteries was present in all animals (n 4) on day 1 postinfusion, whereas on day 8 postinfusion, lesions characterized by medial small pockets of trapped red cells, cell debris, and adventitial thickening were seen in 1 dog/sex. By day 29 postinfusion, coronary arteries were similar to controls. In the dog given daily IV bolus injections of CI-1020 for 4 weeks, arterial in ammatory lesions varied from acute to chronic, although most lesions were considered chronic active. Monastral blue pigments were noted in the wall of most arteries with chronic or chronic active lesions. Acute lesions were similar to those noted in day 1 postinfusion of the reversibility study. Medial smooth muscle necrosis and/or brosis with mixed in ammatory cell in ltrates characterized chronic or chronic active lesions. Smooth muscle proliferation and migration into the intima were also noted. There were no signi cant changes in coronary blood ow, coronary vascular resistance, or mean arterial blood pressure following CI-1020 infusion for 3 hours. In the 24-hour infusion study, plasma endothelin 1 (ET-1) levels were mildly elevated (1.5-4 fold) during CI-1020 infusion when compared to either pretest or control values. These results indicate that administration of endothelin antagonist (CI-1020) to dogs was associated with development of coronary arteriopathy, which was completely resolved within 29 days following cessation of treatment. With prolonged (4-week) CI-1020 treatment, arterial lesions at varying stages of developmen t (acute, chronic active, chronic) were seen, suggesting that tolerance to treatment (up to 4 weeks) does not occur.

No abstract

of the cardiotonic, imazodan (CI-914). Drug Dev. Res. 9:143-157, 1986. lmazodan is a novel pyridazinone derivative. It was evaluated in excised cardiac tissue, anesthetized dogs and monkeys, and conscious dogs. Imazodan, 10-5-10-3M, produced dose-dependent increases in guinea pig atrial and rabbit papillary muscle contractility. In anesthetized dogs and rhesus monkeys, imazodan, 0.001-1 .O mg/kg IV, produced dosedependent increases of 10-150% in myocardial contractility (dPldt max of left ventricular pressure), and decreases of 1-31% in aortic blood pressure. Heart rate increases were minimal (0-34%) in comparison to the changes in contractility and they occurred only at the higher doses. The positive inotropic action of imazodan was not blocked by @-adrenoceptor blockade with propranolol. Forelimb perfusion studies in the anesthetized dog demonstrated that imazodan produces a dose-dependent direct peripheral vasodilator action. This agent was also demonstrated to be a highly effective cardiotonic when administered orally (0.1-1 .O mg/kg) to conscious dogs. The results of these studies indicate that imazodan is an orally effective cardiotonic that possesses balanced positive inotrophic and peripheral vasodilator activities and possesses a wide margin of cardiac safety.

Recent reports suggest that delayed myocardial protection ("second window of preconditioning") occurs 24 hours after brief ischemic or thermal stress. In order to test this hypothesis, we subjected New Zealand White rabbits to a heating regimen (42 degrees C for 15-20 minutes). Twenty four hours later, the effect of heat stress on infarct size was determined by conducting a 30 minute ischemia/3 hour reperfusion protocol. In a separate group of rabbits, Western blot analysis was used to verify that the heating regimen increased expression of HSP72i. The size of the region at risk was delineated by infusion of Unisperse blue and infarcted myocardium was identified by incubation of left ventricular slices in triphenyl tetrazolium chloride. In contrast to expectations, induction of HSP72i with thermal stress was not effective in limiting infarct size in rabbits 24 hours later, calling into question the concept that heat stress induces delayed or "second window" myocardial protection.