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Trapidil (triazolopyrimidine), a platelet-derived growth factor antagonist, reduces restenosis after percutaneous transluminal coronary angioplasty. Results of the randomized, double-blind STARC study. Studio Trapidil versus Aspirin nella Restenosi Coronarica.

BACKGROUND: Trapidil is an antiplatelet drug with specific platelet-derived growth factor antagonism and antiproliferative effects in the rat and rabbit models after balloon angioplasty. METHODS AND RESULTS: The Studio Trapidil versus Aspirin nella Restenosi Coronarica (STARC) is a multicentric, randomized, double-blind trial to assess the effects of trapidil in angiographic restenosis prevention after percutaneous transluminal coronary angioplasty (PTCA). Patients received either trapidil 100 mg TID or aspirin at the same dosage at least 3 days before angioplasty and for 6 months thereafter. Coronary angiograms before PTCA, after PTCA, and at 6-month follow-up were quantitatively analyzed with manual calipers. Of the initial 384 patients recruited, 254 were evaluable for restenosis analysis (128 trapidil, 126 aspirin). Restenosis, defined as a loss of initial percent gain after PTCA of at least 50% (primary end point), occurred in 24.2% of the trapidil group and 39.7% of the aspirin group (P < .01). A similar result was obtained when restenosis per vessel was considered (trapidil, 23.3%; aspirin, 36.9%; P = .018). Clinical events at follow-up were similar in the two groups except that recurrent angina was significantly more frequent in the aspirin group, 43.7% versus 25.8% in the trapidil group (P < .01). Trapidil was well tolerated: only 6 patients had to discontinue the drug because of side effects, which was not different from the aspirin group. CONCLUSIONS: Trapidil reduces restenosis after PTCA at the dosage of 100 mg TID and favorably influences the clinical outcome thereafter.

Aged↗

[The effectiveness of trapidil and trapidil derivatives on drug-induced heart arrhythmias in the rat and guinea pig].

Trapidil and some selected derivatives of trapidil were investigated in ouabain induced arrhythmia in guinea-pigs and in aconitine induced arrhythmia in rats. In both models trapidil exerted a marked antiarrhythmic effect. Investigations on ouabain induced arrhythmia showed that three derivatives were more effective than trapidil concerning the threshold for premature ventricular beats and flutter. One derivative only was able to decrease the sensitivity for fibrillation in the same order of magnitude as trapidil. On aconitine induced arrhythmia all derivatives of trapidil were less effective in elevating the threshold of arrhythmia than trapidil itself, but three derivatives showed antiarrhythmic properties.

Aconitine↗

Influence of aspirin, molsidomine, trapidil, and some trapidil derivatives on arachidonic acid induced reversible thrombocyte aggregation in the rabbit.

For testing antiaggregatory activity of substances in vivo we used transient decrease of circulating platelet number in rabbit blood after rapid i. v. injection of arachidonic acid (AA) as sign of increased thrombocyte aggregates within the tissues. We tested aspirin, molsidomine, trapidil, and 6 trapidil derivatives. Antiaggregatory effects of aspirin, molsidomine, and trapidil confirm former reports and reliability of the used model. 4 trapidil derivatives were effective in doses lower than trapidil itself.

Animals↗

[The effect of trapidil and the trapidil derivative AR 12463 on blood pressure and thromboxane formation in spontaneously hypertensive rats].

The trapidil derivative AR 12463 has a much more stronger inhibiting effect than trapidil on different atherosclerotic parameters of the cell cultures obtained from normal intima and fatty streaks of human aorta, on thromboxane (TX) formation and on the aggregation of human platelets in vitro, and on the activity of phosphodiesterase. In addition to these present results, AR 12463 reduced significantly the mean arterial blood pressure of spontaneously hypertensive rats (at a dosage of 20 mg/kg/d administered orally for 2 weeks) in contrast to the same dosage of trapidil. Simultaneously, TX formation is significantly reduced in serum by 48% in aorta thoracica by 29%, and in aorta abdominalis by 19%. Due to these properties, AR 12463 seems to be suitable for a therapeutic and prophylactic strategy in chronic ischemic diseases.

6-Ketoprostaglandin F1 alpha↗

Inhibition of thromboxane A2 production by trapidil and trapidil derivatives in the arachidonic acid-injected rat.

Trapidil and four selected 5,7-disubstituted s-triazolo (1,5-a)pyrimidine derivatives (AR 12456, AR 12463, AR 12464, AR 12465) which have already been shown to possess inhibitory effects on arachidonic acid(AA)-induced aggregation and thromboxane A2(TXA2) formation in human and rabbit platelets in vitro diminished the AA-stimulated TXA2 production in murine blood in vivo. The inhibitory effects of the derivatives were generally stronger than those of trapidil. The strongest inhibitor of TXA2 formation was the derivative AR 12456. These in vivo results correspond well with our previous in vitro findings.

3',5'-Cyclic-AMP Phosphodiesterases↗

Effects of trapidil and trapidil derivatives on arachidonic acid and prostaglandin endoperoxide analogue U 46619-induced blood pressure changes in rats.

The influence of trapidil (T) and two selected 5,7-disubstituted s-triazolo (1,5-a)pyrimidine derivatives (TD: AR 12456 and AR 12463) on arachidonic acid(AA)- and prostaglandin endoperoxide analogue U 46619-induced blood pressure changes in normotensive rats was investigated in comparison with the cyclooxygenase inhibitor acetylsalicylic acid (ASA) and the thromboxane A2 (TXA2) antagonist BM 13177. ASA and AR 12456 completely eliminated the second blood pressure depression after injection of AA and simultaneously diminished TXA2, TXB2 and 6-keto-PGF1a formation in murine blood, whereas BM 13177 prevented the return of the blood pressure to preinjection level after the initial brief fall in arterial pressure. BM 13177 and AR 12463 reduced the rise in U 46619-provoked blood pressure by 75% and 58%, respectively. Trapidil had no effect on blood pressure changes stimulated by AA and U 46619.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗

[Thromboxane A2 antagonistic effect of antiangina drugs, with special reference to trapidil and trapidil derivatives].

In isolated perfused guinea pig hearts and in the cardiocirculatory system of anaesthetized rabbits the thromboxane A2-agonist U 46619 shows cardiodepressive effects. The contraction force of isolated auricle preparations from guinea pigs was enhanced. Antianginous drugs (dipyridamole, propranolol, verapamil, nitroglycerin and trapidil) induced a significant inhibition of the U 46619 effects. Oxyfedrine remained ineffective. The efficiency of some derivatives of trapidil was markedly diminished or abolished in comparison with the original substance. Because of the different chemical structure of the active drugs the TXA2-antagonism is regarded to be caused by a functional influence on the cellular membrane and the calcium transport. Nevertheless the inhibition of the TXA2-effects by antianginous drugs seems to be a factor for the therapeutic use of these substances.

Anesthesia↗

Trapidil derivatives as potential antiatherosclerotic drugs.

Trapidil, a triazolopyrimidine, and its derivatives are coronary vasodilating drugs. Trapidil reduces the serum level of low density lipoprotein- and very low density lipoprotein-cholesterol and increases the serum level of high density lipoprotein-cholesterol in hyperlipemic patients. The present study demonstrates that trapidil and five different trapidil derivatives inhibit the proliferation of cells cultured from grossly normal intima and fatty streaks of human aorta. The inhibiting effect of trapidil derivatives is about 60%, similar to the standard substance 3-isobutyl-1-methyl-xanthine (MIX). In cells cultured from atherosclerotic plaques trapidil and trapidil derivatives reduced the content of cholesteryl esters by 36% for trapidil and between 47% and 68% for 4 of 5 trapidil derivatives, respectively. The trapidil derivative AR 12463 (5-piperidino-7-[N-(n-amyl)-N-(beta-hydroxyethyl)amino]-s-triazolo[1,5- a]pyrimidine) reduces the free cholesterol content by 29%, but the other trapidil derivatives are without effect on this parameter. Four of five derivatives decrease the content of triglycerides by 53 to 70%. The synthesis of collagen is inhibited by the trapidil derivative AR 12463 (25%). Trapidil and other derivatives have a smaller or no effect on the synthesis of collagen. These effects of trapidil derivatives point to potential antiatherosclerotic properties. The possible mechanisms are discussed.

Arteriosclerosis↗

Effects of local delivery of trapidil on neointima formation in a rabbit angioplasty model.

1. Smooth muscle cell (SMC) proliferation can result in luminal reduction of a vessel following balloon angioplasty. This study was designed (i) to determine if local administration of trapidil (triazolopyrimidine) into a vessel wall reduces neointima formation, and (ii) to explore the mechanism involved in the subsequent reduction in cell proliferation. 2. Following balloon angioplasty in 40 anaesthetized New Zealand White rabbits, trapidil (50-200 mg) or its vehicle (saline) was injected into the dilated vessel wall of the right femoral artery. Experimental groups and time of investigation: (I) vehicle (2 weeks, n = 3), (II) trapidil-100 mg (2 weeks, n = 3), (III) vehicle (3 weeks, n = 8), (IV) trapidil-50 mg (3 weeks, n = 5); (V) trapidil-100 mg (3 weeks, n = 9) or (V) trapidil-200 mg (3 weeks, n = 7). 3. After 2 weeks, there was a significant reduction of intimal hyperplasia (expressed as intima to media area ratio) in the trapidil group compared with vehicle (0.44 +/- 0.04 vs 0.93 +/- 0.04, *P < 0.05) and also a significant reduction in cell proliferation (% ratio of BrdU-positive cells to total cell number: vehicle 14 +/- 2% vs trapidil 6 +/- 1%, *P < 0.05). 4. After 3 weeks, there was a dose-dependent reduction of intimal hyperplasia in the trapidil groups compared with vehicle (trapidil 50 mg 1.14 +/- 0.04; trapidil 100 mg 0.91 +/- 0.09*; trapidil 200 mg 0.77 +/- 0.09* vs vehicle 1.67 +/- 0.23, *P < 0.05). 5. Thus, the local administration of trapidil to the rabbit femoral artery reduces the neointima formation, which occurs 2 or 3 weeks after balloon angioplasty via a mechanism, which is dependent on inhibition of cell proliferation.

Angioplasty, Balloon↗

Antimitogenic effects of trapidil in coronary artery smooth muscle cells by direct activation of protein kinase A.

The triazolopyrimidine trapidil has been found in controlled clinical trials to prevent restenosis after vascular injury. Although trapidil is widely regarded as a platelet-derived growth factor receptor (PDGF) antagonist, its precise mode of action is still unknown. This study was designed to investigate the inhibition of mitogenesis by trapidil in cultured bovine coronary artery smooth muscle cells (SMC) and to identify major signal transduction pathways involved. Trapidil inhibited PDGF-BB-induced mitogenesis in SMC in a concentration-dependent manner. Comparable inhibitory effects were obtained after stimulation of smooth muscle cells by phorbol ester, which suggests that the action of trapidil was not restricted to PDGF receptor-mediated mechanisms. Trapidil also inhibited PDGF- and phorbol ester-induced mitogen-activated protein kinase as well as Raf-1 kinase activity. As a possible target of trapidil, stimulation of cellular protein kinase A (PKA) activity was detected. Trapidil also induced the phosphorylation of vasodilator-stimulated phosphoprotein in SMC. Antimitogenic effects of trapidil were completely abolished by PKA inhibitors. Neither a direct stimulation of cAMP formation nor a phosphodiesterase inhibition was observed at antimitogenic concentrations of trapidil. However, trapidil directly activated purified PKA holoenzyme in a cAMP-independent manner. In conclusion, trapidil exerts its antimitogenic effects on SMC by direct activation of PKA. Thus, PKA-mediated inhibition of the Raf-1/MAP kinase pathway may be involved in the antimitogenic actions of the compound.

Animals↗

Effects of the triazolopyrimidine trapidil on force of contraction, beating frequency and phosphodiesterase I--IV activity in guinea-pig hearts.

The effects of the triazolopyrimidine trapidil (5-methyl-7-diethylamino-s-triazolo [1,5-alpha]pyrimidine, CAS 15421-84-8) on force of contraction, beating frequency and phosphodiesterase (PDE) activity were investigated in isolated preparations from guinea-pig hearts. The effects of 3-isobutyl-1-methylxanthine (IBMX), theophylline and milrinone were studied for comparison. Trapidil exerted a concentration-dependent (1000-3000 mumol(s)/l) positive inotropic effect (EC50 562.4 mumol(s)/l) in guinea-pig papillary muscles. The positive inotropic effect was accompanied by a shortening of the duration of contraction as described for IBMX, or isoprenaline. The efficacy of trapidil was lower than that of IBMX or milrinone. Both agents maximally enhanced force of contraction to a 3fold (milrinone) or even 6fold greater amount (IBMX). The potency of trapidil was almost in the same order of magnitude as that of milrinone. The positive inotropic effect of trapidil is at least partially due to a cyclic adenosine monophosphate (cAMP)-dependent mechanism because carbachol antagonized the increase in force of contraction. Trapidil concentration-dependently but nonselectively inhibited the activities of cAMP PDE isoenzymes I-IV as did theophylline or IBMX. Based on IC50 values (275 mumol(s)/l on the average) trapidil had a potency similar to that of theophylline while IBMX was about one order of magnitude more potent. Regarding the inhibition of PDE III, IBMX was 49fold and milrinone 114fold more potent than trapidil. Trapidil revealed only a marginal positive chronotropic effect. The frequency of spontaneously beating right auricles was increased by 13% at most. Trapidil did not produce any tachyarrhythmias or contractures. It is concluded that the positive inotropic effect of trapidil is mainly due to PDE inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

1-Methyl-3-isobutylxanthine↗

Starc II, a multicenter randomized placebo-controlled double-blind clinical trial of trapidil for 1-year clinical events and angiographic restenosis reduction after coronary angioplasty and stenting.

The objective of this study was to investigate the effect of trapidil 200 mg t.i.d. in preventing the occurrence of death, of myocardial infarction and the need for repeat revascularization at 12 months after balloon PTCA with or without stenting. Coronary restenosis after stenting is still a major drawback of percutaneous coronary interventions (PCI) for 30-40% of patients. Trapidil has been shown to prevent restenosis after PTCA. Eligible patients were randomized to placebo or oral trapidil 200 mg t.i.d. at least 48 hr before PCI and continuing 6 months after a successful balloon angioplasty or stent implantation. Aspirin was given to all patients, and ticlopidine 250 mg b.i.d. to those who received a stent for 4 weeks. In a randomized subgroup of 216 patients, quantitative coronary angiography was performed also at 6-month follow-up. Out of the 933 patients enrolled, primary endpoint incidence was 20.3% in trapidil and 18.0% in placebo (P = 0.37). When recurrence or deterioration of angina was added to the combined endpoint, incidence was 27.4% in trapidil and 23.0% in placebo (P = 0.12). Restenosis rate in patients with 6-month angiography was 25.0% in trapidil arm vs. 30.1% in placebo (P = 0.43). Stent restenosis rate was similar in patients randomized to trapidil or placebo (30.2% vs. 23.8%, respectively; P = 0.44), while in patients treated with balloon angioplasty, it was lower in trapidil (17.1%) than in placebo (40.0%; P = 0.03). Oral trapidil 200 mg t.i.d. for 6 months in addition to aspirin did not influence the occurrence of major cardiac events after coronary angioplasty with or without stenting. In a prespecified subgroup of 191 patients treated with balloon angioplasty only, trapidil reduced angiographic restenosis.

Angioplasty, Balloon, Coronary↗

Trapidil protects ischemic hearts from reperfusion injury by stimulating PKAII activity.

OBJECTIVE: The cardioprotective effects of trapidil on ischemic reperfused (I/R) rabbit hearts were studied. Recently, we had shown that trapidil might activate protein kinase A (PKA). In this study, we examined the exact mode of PKA stimulating activity of trapidil. Finally, we investigated the effect of trapidil on the phosphorylation state of phospholamban (PLB), a major PKA target in the heart and key regulator of Ca(2+) sequestration via the sarcoplasmic reticulum Ca(2+)-ATPase. METHODS: Langendorff-hearts of New Zealand White rabbits were perfused at constant volume and subjected to global low-flow ischemia for 2 h, followed by 1 h of reperfusion. Subsequently, hearts were used for Western blot analysis of PLB phosphorylation. Furthermore, three different regulatory subunits and one catalytic subunit of PKA were overexpressed in E. coli. These PKA subunits were purified and used in an in vitro assay system to test the impact of trapidil on PKA activities in the absence and presence of cAMP. RESULTS: I/R resulted in a significant increase in left ventricular end-diastolic pressure and creatine kinase efflux in the hearts. Trapidil (10 microM) prevented these alterations. Using recombinant cAMP-free PKA isoforms, it was found that trapidil specifically stimulated PKAII but only did so in the presence of small amounts of added cAMP. Furthermore, the PKA-dependent 16Ser phosphorylation of PLB was markedly reduced in I/R. Trapidil largely normalized the 16Ser phosphorylation of PLB. CONCLUSIONS: The data demonstrate cardioprotective actions of trapidil in I/R and show a PKAII-dependent cAMP sensitizing effect of the compound. They also indicate PKA-dependent PLB phosphorylation as a target, suggesting an improved Ca(2+) uptake by the sarcoplasmic reticulum. This action might be involved in the cardioprotective effects of trapidil.

Animals↗

Pharmacokinetics of trapidil, an antagonist of platelet derived growth factor, in healthy subjects and in patients with liver cirrhosis.

1. Pharmacokinetic parameters of trapidil (an antagonist of platelet derived growth factor) were evaluated in 12 healthy male subjects (study I) and in a group of 10 patients with liver cirrhosis (Child B) and five control subjects, respectively (study II). 2. Investigations were carried out after a single dose trapidil (200 mg) and at steady state after application of 200 mg trapidil three times daily for 5 days (study 1) or 4 days (study II). 3. Study I: The concentration-time curves of the terminal elimination phase of trapidil exhibited a slight convexity which might reflect nonlinear kinetics. The AUC of trapidil obtained after the first dose (20.5 [+/- 7.0 s.d.] micrograms ml-1 h) was markedly higher than the AUC determined at steady state (13.2 [+/- 3.8 s.d.] micrograms ml-1 h), the non-parametric 90% confidence intervals of the ratio day 5/day 1 was 0.58-0.73 (point estimator 0.64). 4. Study II: AUC averaged (21.4 [+/- 9.1 s.d.] micrograms ml-1 h) in controls and (34.4 [+/- 14.9 s.d.] micrograms ml-1 h) in cirrhotic patients. The 90% confidence intervals for the difference group 1 vs group 2 was 0.95-2.97 (point estimator 1.48, P = 0.066). At steady state, AUC averaged (13.7 [+/- 5.7 s.d.] micrograms ml-1 h) in controls and (20.8 [+/- 6.8 s.d.] micrograms ml-1 h) in cirrhotic patients (90% confidence intervals group 1 vs group 2: 0.88-2.20 [point estimator 1.45, P = 0.05]). As seen in study I, the AUC of trapidil obtained after the first dose was markedly higher than the AUC determined at steady state, the non-parametric 90% confidence intervals of the ratio day 5/day 1 was 0.48-0.84 (point estimator 0.66) in control subjects and 0.54-0.72 (point estimator 0.64) in cirrhotic patients, respectively. 5. An inverse correlation was seen between the results of the monoethylglycinxilidid (MEGX)-test and the AUC of trapidil (single dose: r = -0.516, P = 0.048; steady state: r = -0.548, P = 0.042). 6. Results of study I and study II indicate an autoinduction of trapidil metabolism after repeated oral doses. Although trapidil elimination is decreased in patients with liver cirrhosis (study II), the elimination half-life at steady state is relatively short (2.4 [+/- 1.1 s.d.] h) and therefore should prevent cumulation of trapidil even in cirrhotic patients.

Adult↗

Inhibitory effect of trapidil on human meningioma cell proliferation via interruption of autocrine growth stimulation.

In a previous study, the authors demonstrated that meningioma cells secrete platelet-derived growth factor (PDGF)-like molecules that stimulate their own growth in an autocrine manner. Based on that finding, a study was undertaken to examine the effect of trapidil, a drug known to have an antagonistic action against PDGF, on cell proliferation of human meningiomas in culture. Trapidil showed a dose-dependent inhibition of meningioma cell proliferation in the absence of any exogenous mitogenic stimulation. The maximum effect was observed at a concentration of 100 micrograms/ml, with the decrease in cell growth ranging from 16% to 54% compared to control samples. Trapidil similarly inhibited the basal deoxyribonucleic acid (DNA) synthesis assessed by [3H]-thymidine incorporation in three of seven meningiomas. While the conditioned medium generated from meningioma cells remarkably stimulated the proliferation of meningioma cells (166% to 277% of control), this effect was strikingly inhibited by the addition of trapidil. Trapidil also inhibited conditioned medium-stimulated DNA synthesis, even when there was no effect on basal DNA synthesis. Furthermore, trapidil significantly inhibited the epidermal growth factor (EGF)-stimulated proliferation of meningioma cells. This inhibitory effect on EGF-stimulated cell proliferation was also observed in nontumorous fibroblasts, demonstrating that trapidil is not an antagonist specific to PDGF. The addition of trapidil (30 micrograms/ml) in combination with bromocriptine (1 microM) showed an additive inhibitory effect on the meningioma cell growth compared to trapidil or bromocriptine alone. The overall results suggest that trapidil exhibits an inhibitory effect on meningioma cell proliferation through blocking the mitogenic stimulation induced by autocrine or exogenous growth factors, and may be considered as a possible new approach to the medical treatment of meningiomas.

Cell Division↗

[Effect of trapidil on experimental hyperlipemia and atherosclerosis induced by cholesterol diet in SPF Japanese white rabbits].

The effect of trapidil on experimental hyperlipemia and atherosclerosis induced by 1% cholesterol diet in SPF male rabbits (JW/KBL) was investigated by the determination of the lipid contents of the plasma and thoracic aorta and examination of morphological changes in the aorta. Trapidil inhibited the increase of total lipid (TL), total cholesterol (TC), free cholesterol (FC) and phospholipid (PL) by the cholesterol diet in all groups. The level of cholesterol (HDL-C) and phospholipid (HDL-PL) in high density lipoprotein (HDL) remained unchanged after the cholesterol diet and trapidil administration. The atherogenic index (TC-HDL-C/HDL-C, PL-HDL-PL/HDL-PL) was improved by the inhibition of TC and PL by the administration of trapidil. A morphological study of the aorta showed that trapidil inhibited lipid deposition. A microscopic observation of the intima by Sudan III stain showed that inhibition of lipid deposition corresponded with the quantity of trapidil administration. An observation of aorta using transmission electron microscopy (TEM) showed that trapidil inhibited the presence of form cells due to HCD. This inhibition corresponded with the quantity of trapidil administration; and no form cells were seen in the 50 mg/kg-administered group. An observation of intima using scanning electron microscopy (SEM) showed that trapidil inhibited the irregularly elevated regions by HCD. The structure of intima in the 50 mg/kg-administered group was similar to that of the control groups. The observation of the head angiogram showed that trapidil improved the stenosis in the lingual and temporal arteries which was caused by HCD.

Animals↗

In vitro effects of trapidil on fatty acid and prostaglandin metabolism in platelets.

The effects of trapidil, a coronary vasodilator and platelet aggregation inhibitor, on fatty acid metabolism and prostaglandin (PG) formation in platelets were studied using platelet suspensions from six normal subjects. The addition of trapidil to fatty acids in platelet phospholipids decreased palmitoleic acid and arachidonic acid, and increased an unidentified substance, X2 (palmitoleic acid, P < 0.05; arachidonic acid, P < 0.05; X2, P < 0.05). Thrombin stimulation following the addition of trapidil resulted in an increase in stearic acid and a decrease in arachidonic acid, compared with the trapidil-free control samples (stearic acid, P < 0.05; arachidonic acid, P < 0.02). The addition of trapidil tended to increase immunoreactive PGE (iPGE) and iPGF dose-dependently. On the other hand, thrombin stimulation following the addition of trapidil decreased the formation of thromboxane B2 (TXB2) significantly compared with the levels of TXB2 in the trapidil-free samples (10 micrograms/mL trapidil, P < 0.005, 100 micrograms/mL trapidil, P < 0.001). These results show that trapidil increased arachidonic acid mobilization in the platelets.

Blood Platelets↗