[Crystalline polymorphism of eflucimibe]. / Polymorphisme cristallin de l'éflucimibe.

The importance, in therapeutics, of the concept of bioavailability and on-going quality research in the formulation of a drug has prompted us to examine the crystalline polymorphism of eflucimibe as from the research phase. This study has been carried out by re-crystallization of the product in organic solvents having a different polarity in a variety of experimental temperature and pressure conditions, then, subsequently, by re-cooling the previously dissolved substance. The analytical methods applied to identify and then describe the polymorphic forms are thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray powder diffraction from synchrotron radiation (XRPD), infrared spectrometry (IR), solid-state nuclear magnetic resonance spectrometry (SSNMR) and lastly maximum solubility measurements. By means of XRPD, two polymorphic forms called A and B have been clearly identified at ambient temperature. These two crystalline forms were obtained in a reproducible way, then described by DSC, XRPD, IR and SSNMR. Differential scanning calorimetry analysis has shown for polymorphic form A two endothermic phenomena with low energy at about 35 masculine and 118 degrees C attributed by XRDP to conformational polymorphism. The complex endothermic event that extends between 75 masculine and 105 degrees C appears to correspond to successive alterations of a lamellar structure. The solid-solid transition observed at 110 degrees C is due to a change of crystalline phase, then the melting point occurring at about 130 degrees C. For form B, two changes of crystalline phase are clearly observed at about 80 masculine and 120 degrees C. The reversibility of these changes was observed by thermomicroscopy in polarized light. Form A, which is less soluble in absolute ethanol than form B, is the more stable thermodynamically in the temperature range from 25 masculine to 50 degrees C where the data have been obtained. The Van't Hoff diagram layout for each polymorphic form appears to reveal an A<-->B transition temperature in a temperature range lower than 25 degrees C. This study, undertaken as from the research phase, has enabled us to highlight the polymorphism of this new chemical entity by means of XRDP by explaining the nature of the endothermic phenomena observed by DSC, and lastly identify the thermodynamically more stable polymorphic form, thus contributing to a better knowledge of this future drug.

5-HT1A receptor activation and antidepressant-like effects: F 13714 has high efficacy and marked antidepressant potential.

To examine further the hypothesis that the magnitude of the intrinsic activity of agonists at 5-HT1A receptors determines the magnitude of their psychotropic activity, we studied the relationship between the maximal receptor activation produced by various 5-HT1A receptor ligands and their antidepressant-like effects (i.e., decreased immobility in the forced swimming test in rats). Using three different in vitro assays suitable to measure differences among high, intermediate, and low efficacy 5-HT1A receptor agonists, ligands were identified with intrinsic activities ranging from low-negative (i.e., the inverse agonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane-carboxamide (WAY 100635)) to high-positive (i.e., 3-chloro-4-fluorophenyl-(4-fluoro-4-[[(5-methyl-6-methylamino-pyridin-2-ylmethyl)-amino]-methyl]-piperidin-1-yl-methanone (F 13714)). In addition, novel compounds with intermediate intrinsic activity, like buspirone, but with high selectivity for 5-HT1A receptors, unlike buspirone, were identified. The maximal effects of the 5-HT1A receptor ligands in the forced swimming test correlated positively (rS=0.91, P<0.005) with the rank order of their intrinsic activity at 5-HT1A receptors. This relationship constitutes evidence that the magnitude of the psychotropic activity of 5-HT1A receptor ligands is a positive function of their intrinsic activity at the receptor, and suggests that F 13714, which had maximal effects in the forced swimming test significantly larger than any of the other compounds examined here, did so because of its higher intrinsic activity at 5-HT1A receptors.

F 12511, a novel ACAT inhibitor, and atorvastatin regulate endogenous hypercholesterolemia in a synergistic manner in New Zealand rabbits fed a casein-enriched diet.

F 12511, a novel ACAT inhibitor, lowers plasma cholesterol levels in New Zealand rabbits fed a cholesterol-free casein-rich diet. In rabbits endogenous hypercholesterolemia pre-established for 8 weeks was used to compare treatments with F 12511 and atorvastatin for a further 8-week period, and to determine whether both agents act synergistically. F 12511 appears to be 3-4-fold more potent than atorvastatin in reducing total plasma cholesterol (active doses ranging from 0.16 to 2.5 and from 1.25 to 10 mg/kg per day, respectively) while the hypocholesterolemic efficacy of both compounds at 2.5 mg/kg per day amounted to 70 and 45%, respectively. A reduction by as much as 75% of esterified cholesterol in liver mediated by F 12511 could account for the decrease of plasma VLDL, LDL and apo B-100, whereas a reduction of the LDL production rate has been described as the main mechanism underlying the atorvastatin effect. F 12511 modified adrenal cholesterol balance only at the largest dose studied. In a further experiment the co-administration of threshold doses of F 12511 and atorvastatin (0.63 and 1.25 mg/kg per day, respectively) lowered plasma total cholesterol and apo B-100 containing lipoproteins to a greater extent and more rapidly than either agent alone. In the liver a decrease by atorvastatin in free cholesterol substrate for ACAT may amplify the effect of F 12511 on cholesteryl ester content leading to a diminution, in at least an additive manner, of the assembly and secretion of atherogenic lipoproteins in New Zealand rabbits which have developed an endogenous hypercholesterolemia. Thus, the combination of the ACAT inhibitor F 12511 with atorvastatin can represent a better approach than either agent alone to regulate lipoprotein metabolism in certain pathophysiological situations.

Lack of toxic effects of F 12511, a novel potent inhibitor of acyl-coenzyme A: cholesterol O-acyltransferase, on human adrenocortical cells in culture.

Inhibition of acyl-coenzyme A: cholesterol O-acyltransferase (EC 2.3.1.26; ACAT) reduces intracellular cholesteryl esters that are substrates for steroidogenesis in adrenal cells. The adrenal side effects of ACAT inhibitors remain a key point for their development as antiatherosclerotic agents. The aim of this study was to characterize the effects of a novel and powerful ACAT inhibitor, F 12511 (S)-2',3',5'-trimethyl-4'-hydroxy-alpha-dodecylthio-phenylacetanilide, on the NCI-H295R cell line, which has functional properties comparable to those of normal human adrenal cells. F 12511 incubated with cultured cells for 4-72 hr strongly inhibited cholesteryl oleate formation. The concentrations required to produce 50% inhibition (IC50) values) ranged from 20 to 50 nM; in the presence of low-density lipoproteins (LDL), this effect was paralleled by a decrease in cholesteryl ester mass and an increase in intracellular free cholesterol. At concentrations 100-fold larger than the IC(50) value for up to 48 hr, F 12511 reduced neither the basal release of cortisol and aldosterone nor the production of cortisol stimulated by forskolin. F 12511 did not modify the mRNA levels of the steroidogenic enzyme genes cytochrome P450 cholesterol side-chain cleavage (P450scc), cytochrome P450 17alpha-hydroxylase (P450c17), or cytochrome P450 21-hydroxylase (P450c21) or those of the LDL receptor and high-density lipoprotein scavenger receptor class B, type I (SR-BI) genes, either in the presence or absence of adenosine 3',5'-cyclic monophosphate stimulation for 24 hr. Exposure to F 12511 at up to 3 microM for 24 or 48 hr did not result in significant change in morphological and ultrastructural characteristics; the cytoplasm contained large numbers of mitochondria with intact crystae, and the same typical features of secretory activity were observed in NCI-H295R control cells. Exposure to 3 microM of F 12511 for 96 hr also did not affect cell viability. These data demonstrate that reduction of the substrate for steroidogenesis by the ACAT inhibitor F 12511 impairs neither steroid production nor transcription of genes involved in steroidogenesis and lipoprotein uptake in the pluripotent human adrenal cell line NCI-H295R.

Immunological quantitation and localization of ACAT-1 and ACAT-2 in human liver and small intestine.

By using specific anti-ACAT-1 antibodies in immunodepletion studies, we previously found that ACAT-1, a 50-kDa protein, plays a major catalytic role in the adult human liver, adrenal glands, macrophages, and kidneys but not in the intestine. Acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity in the intestine may be largely derived from a different ACAT protein. To test this hypothesis, we produced specific polyclonal anti-ACAT-2 antibodies that quantitatively immunodepleted human ACAT-2, a 46-kDa protein expressed in Chinese hamster ovary cells. In hepatocyte-like HepG2 cells, ACAT-1 comprises 85-90% of the total ACAT activity, with the remainder attributed to ACAT-2. In adult intestines, most of the ACAT activity can be immunodepleted by anti-ACAT-2. ACAT-1 and ACAT-2 do not form hetero-oligomeric complexes. In differentiating intestinal enterocyte-like Caco-2 cells, ACAT-2 protein content increases by 5-10-fold in 6 days, whereas ACAT-1 protein content remains relatively constant. In the small intestine, ACAT-2 is concentrated at the apices of the villi, whereas ACAT-1 is uniformly distributed along the villus-crypt axis. In the human liver, ACAT-1 is present in both fetal and adult hepatocytes. In contrast, ACAT-2 is evident in fetal but not adult hepatocytes. Our results collectively suggest that in humans, ACAT-2 performs significant catalytic roles in the fetal liver and in intestinal enterocytes.

F 11440, a potent, selective, high efficacy 5-HT1A receptor agonist with marked anxiolytic and antidepressant potential.

F 11440 (4-methyl-2-[4-(4-(pyrimidin-2-yl)-piperazino)-butyl]-2H, 4H-1,2,4-triazin-3,5-dione) was the outcome of a research effort guided by the hypothesis that the magnitude of the intrinsic activity of agonists at 5-HT1A receptors determines the magnitude of their antidepressant and anxiolytic-like effects. The affinity of F 11440 for 5-HT1A binding sites (pKi, 8.33) was higher than that of buspirone (pKi, 7.50), and somewhat lower than that of flesinoxan (pKi, 8.91). In vivo, F 11440 was 4- to 20-fold more potent than flesinoxan, and 30- to 60-fold more potent than buspirone, in exerting 5-HT1A agonist activity at pre- and postsynaptic receptors in rats (measured by, for example, its ability to decrease hippocampal extracellular serotonin (5-HT) levels and to increase plasma corticosterone levels, respectively). F 11440 did not have detectable antidopaminergic activity (unlike buspirone, which inhibited all of the directly observable behavioral effects of methylphenidate in rats), showed no evidence of antihistaminergic activity (unlike flesinoxan, which protected against the effects of a histamine aerosol in guinea pigs), and had a 70-fold separation between its 5-HT1A agonist and alpha-1 adrenergic antagonist properties (measured as the ability to inhibit the methoxamineinduced increase in blood pressure in rats), unlike flesinoxan, which showed a <3-fold separation. In HeLa cells expressing human 5-HT1A receptors, F 11440 decreased the forskolin-induced increase in AMP, and, based on its maximal effect, was found to have an intrinsic activity of 1.0 relative to that of 5-HT, which was significantly higher than that of buspirone (0.49), ipsapirone (0.46) and flesinoxan (0.93). Consistent with the aforementioned hypothesis, F 11440 produced anxiolytic- and antidepressant-like effects in animal models (i.e., increased punished responding in a pigeon conflict procedure and decreased immobility in a rat forced swimming test, respectively) that were more substantial than those of buspirone, ipsapirone and flesinoxan. Thus, F 11440, shown here to be a potent, selective, high efficacy 5-HT1A receptor agonist, appears to have the potential to exert marked anxiolytic and antidepressant activity in humans.

Evidence for partial agonist properties of daltroban (BM 13,505) at TP receptors in the anaesthetized open-chest rat.

We sought to determine whether the intrinsic pulmonary hypertensive activity of the purported thromboxane A2/prostanoid (TP) receptor antagonist, daltroban, was mediated by TP receptors, using the high efficacy TP receptor agonist, U-46619, and the silent TP receptor antagonist, SQ 29,548. In pentobarbitone-anesthetized, open-chest rats (n = 4-10 per group), non-cumulative injections of U-46619, dose-dependently increased mean pulmonary arterial pressure (MPAP) with an ED50 (geometric mean with 95% confidence limits in parentheses) of 1.4 (1.1-2.3) microg/kg i.v.. Daltroban increased MPAP in a bell-shaped manner, with an apparent ED50 [29 (21-35) microg/kg i.v.] being 21 fold less potent than that of U-46619. The maximal pulmonary hypertensive responses evoked by daltroban represented about half those induced by U-46619 (25.4+/-1.0 vs. 12.7+/-2 mmHg; P < 0.05 between groups). The TP receptor antagonist SQ 29,548 fully antagonized increases in MPAP evoked by equihypertensive doses of U-46619 (1.25 microg/kg) or daltroban (80 microg/kg). Further experiments were carried out to determine whether daltroban antagonized the pulmonary hypertensive responses evoked by the high efficacy agonist, U-46619, or by itself as receptor theory would predict for a partial agonist. Daltroban (10-2500 microg/kg) antagonized, although not fully, U-46619 (20 microg/kg)-evoked pulmonary hypertensive responses, since prominent intrinsic pulmonary hypertensive effects of daltroban were observed in the same range of doses. Furthermore, in contrast to U-46619 (1.25 microg/kg), daltroban (80 microg/kg) failed to evoke a second pulmonary hypertensive response following a previous injection, as would be expected for a partial agonist. Collectively, the results strongly suggest that daltroban behaves as a partial agonist at TP receptors in the pulmonary vascular bed of the rat in vivo.

Investigation of the mechanism by which ketanserin prolongs the duration of the cardiac action potential.

Action potential duration (APD) lengthening is believed to underlie the cardiac arrhythmogenicity of ketanserin, a serotonin (5-HT)2A/2C receptor antagonist. We wished to determine (a) whether this activity involves blockade of 5-HT2A/2C receptors and (b) the precise mechanism of ketanserin-induced APD prolongation. APs were recorded in guinea pig isolated papillary muscles by conventional "floating" microelectrodes, and potassium currents in guinea pig isolated myocytes were recorded in the whole-cell configuration. Ketanserin (1-10 microM) increased APD (EC50 value for enhancing APD at 90% repolarization (APD90) 3.1 +/- 2.7 microM, n = 24), without affecting resting potential, maximum upstroke velocity (Vmax) or AP amplitude (APA). Pirenperone (10 microM), a ketanserin congener, similarly increased APD90 from 204 +/- 3 to 241 +/- 7 ms (p < 0.001, n = 6). No increase in APD was observed, however, with ritanserin or ICI 170809, even at high concentrations (10 microM, n = 6, respectively), two 5-HT2A/2C receptor antagonists chemically distinct from ketanserin, thereby excluding the involvement of 5-HT2A/2C receptors in mediating APD lengthening. That APD prolongation was mediated specifically by the benzolyl-piperidine moiety of ketanserin and pirenperone was confirmed by 1-propyl-4(4-fluorobenzoyl)piperidine (PFBP), which evoked APD lengthening effects remarkably similar to those produced by ketanserin and pirenperone (EC50 3.73 +/- 2.6 microM, n = 12). In isolated cardiomyocytes, ketanserin (1-32 microM) selectively and concentration-dependently reduced the IKr component of the delayed outward current (IK) without affecting the inward rectifier current, IK1. Thus, ketanserin (32 microM) significantly reduced IK at a potential value of -20 mV from 813 +/- 65 to 569 +/- 55 pA (p < 0.001, n = 6), whereas at a potential value of -110 mV, IK1 was not significantly affected (730 +/- 103 vs. 603 +/- 143 pA, respectively; n=6). The results demonstrate that APD is prolonged by ketanserin and congeners but not be chemically different 5-HT2A/2C receptor antagonists. The benzoyl-piperidine moiety appears to mediate the APD-prolonging effects of ketanserin and pirenperone specifically. Furthermore, ketanserin-induced APD lengthening does not appear to involve 5-HT2A/2C receptors but is consecutive to direct blockade of myocardial potassium channels.

Intrinsic activity of the non-prostanoid thromboxane A2 receptor antagonist, daltroban (BM 13,505), in human platelets in vitro and in the rat vasculature in vivo.

1. We evaluated the effects of daltroban on (i) human platelet shape change and aggregation in vitro, and (ii) mean systemic and pulmonary arterial pressures (MAP and MPAP, respectively) as well as haematocrit, in anaesthetized, open-chest Sprague-Dawley rats, compared with those of a chemically distinct prostanoid thromboxane A2 (TxA2) receptor antagonist, SQ 29,548, and agonist, U-46619. 2. In human platelets in vitro, daltroban (10 nM-100 microM; n = 6 per group) concentration-dependently induced shape change, attaining at 50 microM, a maximum amplitude of 0.83 +/- 0.09 mV representing 46.4 +/- 4.8% of that evoked by U-46619 (1.78 +/- 0.20 mV at 0.2 microM; n = 9); and inhibited U-46619-induced platelet aggregation with an IC50 of 77 (41-161)nM. SQ 29,548 (10 nM-100 microM; n = 6 per group) failed to evoke any platelet shape change, but potently inhibited U-46619-induced platelet aggregation with an IC50 < 10 nM. 3. In anaesthetized rats in vivo, daltroban (10-2500 micrograms kg-1, i.v. infused over 2 min; n = 4-8 per group) produced a bell-shaped dose-response curve for MPAP and haematocrit, and evoked maximal increases of 12.7 +/- 2.1 mmHg and 5.8 +/- 1.5% at 80 micrograms kg-1 (n = 6) and 630 micrograms kg-1 (n = 8), respectively (both P < 0.05) with ED50s of 20 (16-29) and 217 (129-331) micrograms kg-1, respectively. By comparison, U-46619(0.16-20 microg kg-1, i.v.), induced dose-dependent increases in MPAP and haematocrit (25.4 +/- 1.0 mmHg and 16.1 +/- 2.9% at the highest dose; n = 12, both P<0.01), with ED50s of 1.8 (1.3-2.5) and 3.9(3.5- 5.4) microg kg- 1, respectively. Daltroban dose-dependently increased MAP with a maximum amplitude of 42.2 +/- 4.4 mmHg at a dose of 80 microg kg-1 [ED50 = 94 (64-125) microg kg-1], similar to that induced by U-46619 (41.3 +/- 9.6 mmHg) at a dose of 0.63 microg kg-1 [ED50= 0.22 (0.13-0.24) microg kg-1]. SQ 29,548(10-2500 microg kg-1, i.v.; n =4 per group) failed to modify significantly any of these parameters.4. Our results clearly demonstrate that daltroban, in a similar manner to the TxA2 analogue, U-46619,but unlike the TxA2 receptor antagonist, SQ 29,548, exhibits significant intrinsic activity in human platelets in vitro and in the rat vasculature in vivo, possibly through TxA2 receptor activation.

Prevention by specific chemical classes of alpha 1-adrenoceptor antagonists of veratrine-contractures in rat left atria independently of alpha 1-adrenoceptor blockade.

1. The putative direct protective effects of a series of chemically diverse alpha 1-adrenoceptor antagonists against veratrine alkaloid-induced tetanic contractures in rat isolated left atria have been investigated. 2. Atria were mounted in organ baths containing normal, oxygenated physiological salt solution (20 ml, pH 7.4), for isometric tension recording. Atria were electrically driven at 4 Hz and were maintained at 34 degrees C. Veratrine (100 micrograms ml-1) was applied to the atria to elicit tetanic (diastolic) contracture. 3. Concentration-dependent protective effects against veratrine-contractures, in the absence of negative inotropic responses, were observed with the quinazoline congeners, prazosin and doxazosin and with the benzodioxane-related compounds, WB 4101 and its thio analogue, benoxathian. IC50 concentrations and apparent Hill coefficients of all four drugs ranged from 0.27 to 0.93 microM, and from 0.86 to 1.09, respectively, and are consistent with interaction at a single site. 4. In contrast, no protective activity versus veratrine-contractures was observed with corynanthine, 5-methyl-urapidil, phenoxybenzamine, phentolamine or chloroethylclonidine (10 microM). 5. Contractures were prevented by prazosin at concentrations 2-3 log units higher than those which antagonized methoxamine-evoked inotropic responses. In addition, concomitant alpha 1-adrenoceptor occupancy by high concentrations of methoxamine (100 microM), phentolamine (10 microM, inactive per se in preventing contracture), or both drugs together, failed, in each case, to modify significantly the protective effects of prazosin or WB 4101 against veratrine-contractures. 6. Our findings demonstrate that alpha 1-adrenoceptor antagonists which prevent veratrine-contractures belong to specific chemical classes of the quinazoline- and benzodioxane-type. The mechanism by which these drugs afford protection is apparently independent of an interaction with defined alpha 1-adrenoceptors.

Characterization of polymorphs and solvates of 3-amino-1-(m-trifluoromethylphenyl)-6-methyl-1H-pyridazin-4-one.

The characterization of two polymorphs of the title compound (F2692; 1) by differential scanning calorimetry (DSC), microanalysis, proton nuclear magnetic resonance spectroscopy, thermogravimetry, thermomicroscopy, infrared spectroscopy, and X-ray diffractometry is described. Both polymorphs are crystalline, with form II being more stable at temperatures less than 160 degrees C. The thermal behavior was studied at different rates of heating, and the enthalpies of transition were calculated from DSC data. The transformation of aqueous suspensions of form I to the water-stable form II is described, and the heats of solution and intrinsic aqueous dissolution rates of both polymorphs were determined. 1 also formed solvates with dimethyl sulfoxide and 1-methyl-2-pyrrolidinone. The solvates were studied by thermogravimetry, DSC, and infrared spectroscopy.