The pharmacokinetics and pharmacodynamics of a new thromboxane synthetase inhibitor, 6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid (DP-1904), in man after single oral administration

Effect of DP-1904, a thromboxane synthetase inhibitor, on antigen- and spasmogen-induced bronchoconstriction in rodents

The effect of DP-1904 [6-(1-imidazolylmethyl)-5,6,7,8-tetra-hydronaphthalene-2-car boxylic acid hydrochloride], a selective thromboxane synthetase inhibitor, was examined on antigen- and spasmogen-induced bronchoconstriction in rodents. Oral administration of DP-1904 (1, 3, 10 mg/kg) as well as OKY-046 (sodium (E)-3[4-(1-imidazolylmethyl)-phenyl]-2-propanoate, 100 mg/kg), significantly inhibited immunoglobulin G-mediated bronchoconstriction in actively sensitized guinea pigs. Immunoglobulin E-mediated bronchoconstriction in actively sensitized rats was also inhibited by both DP-1904 (1, 10 mg/kg) and OKY-046 (100 mg/kg). DP-1904 (3-30 mg/kg) and OKY-046 (30 mg/kg) suppressed leukotriene D4-induced bronchoconstriction in guinea pigs. In these models, the endogenous levels of thromboxanes significantly increased following the stimulus (antigen and leukotriene D4). DP-1904 (10 mg/kg) inhibited the increase in thromboxane level in both plasma and bronchial alveolar lavage fluid. These actions of DP-1904 persisted for more than 12 h, indicating a long-lasting effect of DP-1904 on bronchoconstriction. The results showed that the biological activity of DP-1904 in our rodents models is more potent than that of OKY-046 (Ozagrel), which is available as an anti-asthma agent in Japan.

Effects of DP-1904, a thromboxane synthetase inhibitor, on the antigen-induced airway hyperresponsiveness and infiltration of inflammatory cells in guinea-pigs

The effect of DP-1904, a novel thromboxane (TX) synthetase inhibitor, on airway hyperresponsiveness was studied in actively sensitized guinea-pigs. Airway hyperresponsiveness to intravenous ACh was observed at 3 and 7 h after aerosolized antigen challenge. In the model, a significant correlation between increases of respiratory resistance and microvascular leakage was observed, corresponding to the elevation of TXB2 in bronchoalveolar lavage fluid (BALF) in the early phase. DP-1904, at doses of 3 mg/kg or higher given orally one hour prior to the antigen challenge, inhibited the TXB2 production and the development of airway hyperresponsiveness in the early phase. Further, DP-1904 significantly suppressed the accumulation of lymphocytes in BALF and airway hyperresponsiveness in the late phase, although it only slightly decreased the mobilization of eosinophils and neutrophils. The results suggest that TXA2 is possibly involved in the development of airway hyperresponsiveness, and DP-1904 prevented the airway hyperresponsiveness via inhibition of TXA2 production and regulation of inflammatory cells.

Pharmacokinetic-pharmacodynamic modelling of DP-1904, a novel thromboxane synthetase inhibitor in rabbits, based on an indirect response model

A new imidazole derivative, DP-1904, produces a selective, potent and long-acting inhibition of thromboxane A2 (TXA2) syntheses and platelet aggregation. This study was designed to investigate the pharmacokinetics and pharmacodynamics (PK/PD) of DP-1904. DP-1904 disappeared from plasma with a half-life of 20 min after i.v. dosing, and the bioavailability after oral dosing was approximately 70%. The level of serum TXB2, which is a pharmacological marker for thromboxane synthetase inhibition, was measured to characterize the pharmacodynamics of DP-1904. A marked reduction of serum TXB2 was exhibited within 1 h after both i.v. and oral doses, reflecting the rapid onset of action of DP-1904. Serum TXB2 returned to the basal level much more slowly after oral dosing than after i.v. dosing, due to the longer half-life after oral dosing. An Emax model was employed to fit the pharmacological data after oral dosing, and IC50 and Emax values were estimated to be 5.0 ng/ml and 81%, respectively. In order to test its predictability, the PK/PD model was then used to predict a pharmacological profile after i.v. dosing; good agreement between the observed and predicted values was achieved. Thus, the present modelling procedure may be useful for optimizing the therapeutic regimens of DP-1904.

DP-1904, a specific inhibitor of thromboxane A2 synthesizing enzyme, suppresses ICAM-1 expression by stimulated vascular endothelial cells

Intercellular adhesion molecule-1 (ICAM-1) is an antigen that is strongly expressed by vascular endothelial cells at sites of local inflammation and participates in the development of inflammation. In the present study, vascular endothelial cells were stimulated by inflammatory cytokines that promote thromboxane A2 synthesis to observe their effects on the expression and shedding of ICAM-1 on the cell surface. In addition, the suppressive effects of DP-1904 ([+/-]-6-[1-imidazolylmethyl]-5,6,7,8-tetrahydronaphthalene-2- carboxylic acid hydrochloride hemihydrate), a thromboxane A2 synthesis inhibitor, on ICAM-1 expression were evaluated. ICAM-1 expression on the surface of human umbilical vein endothelial cells was increased significantly by stimulation with interleukin-1 beta, tumor necrosis factor alpha (TNF alpha), thrombin and platelet-activating factor (PAF). DP-1904, an inhibitor of thromboxane A2 synthesis, significantly suppressed the expression of ICAM-1 on the surface of human vascular endothelial cells that had been stimulated by TNF alpha or PAF. These findings suggest that an enhanced expression of thromboxane A2 on human vascular endothelial cells is closely related to the expression of ICAM-1 on the surface of these cells.

A thromboxane A2 synthetase inhibitor retards hypertensive rat diabetic nephropathy

Spontaneously hypertensive rats (SHR) were injected with streptozotocin (STZ-SHR) to induce diabetes. The effect of DP-1904, a thromboxane A2 synthetase inhibitor, on diabetic nephropathy was then studied by administering it for 5 months (1 or 10 mg/kg). DP-1904 did not affect renal 6-keto prostaglandin (PG)F1 alpha production in STZ-SHR, but markedly inhibited renal thromboxane (TX) B2 production, so that the 6-keto PGF1 alpha/TXB2 ratio was significantly increased (P less than 0.05). STZ-SHR showed significant uraemia and proteinuria, plus increases in urinary gamma-glutamyl-transpeptidase and urinary N-acetyl-beta-glucosaminidase. DP-1904 significantly decreased (P less than 0.01) the urinary changes. STZ-SHR also showed an increase in mesangial periodic acid-Schiff-positive substance and in relative renal weight, both of which were significantly inhibited by DP-1904 (P less than 0.05). Thus, DP-1904 inhibited both TXB2 production and the progression of renal damage in STZ-SHR.

The pharmacokinetics and pharmacodynamics of a new thromboxane synthetase inhibitor, 6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid (DP-1904) in man after repeated oral doses

The pharmacokinetics of DP-1904, a new potent and selective thromboxane synthetase inhibitor, and its effects on ex-vivo prostanoid formation have been studied in groups of Japanese normal male volunteers, who received repeated oral doses of 200 mg every 12 h for 4 doses, or 400 mg every 24 h for 2 doses, or 200 mg every 12 h for 14 doses. The drug was well tolerated by all subjects without evidence of adverse reactions. Repeated administration showed no significant changes in half-lives, tmax values, cmax values and AUC values. DP-1904 did not exhibit time-dependent kinetics. Its plasma levels were lower than the quantifiable level (50 ng mL-1) at 12 h after each dose. These data suggest no significant accumulation of DP-1904 in normal volunteers. DP-1904 reduced the serum thromboxane B2 by about 80% during the medication, the serum concentrations returning to about 44, 75 and 20% of the predrug control values at 36 h after the last 200 mg doses and 48 h after the last 400 mg dose.