Bilastine: a new H1 -antihistamine with an optimal profile for updosing in urticaria

This review set out to examine published papers detailing the efficacy of bilastine in skin models and urticaria to assess whether it meets the optimal profile for updosing in urticaria, that is, strong clinical efficacy and freedom from unwanted side effects, particularly sedation. Bilastine is a highly effective H₁ -antihistamine even when used at the basic dose of 20 mg daily. Its facilitated uptake after oral dosage gives it a rapid onset and long duration of action. In both wheal and flare studies and in urticaria updosing fourfold showed increased effectiveness. With respect to somnolence, bilastine is a substrate for P-glycoprotein, a membrane pump which prevents it crossing the blood-brain barrier. Consequently, bilastine is a practically 'non-sedating' H₁ -antihistamine. In conclusion, the excellent profile of bilastine in both efficacy and safety make it the ideal H₁ -antihistamine for updosing the daily dose fourfold in difficult-to-treat urticaria as recommended by the EAACI/GA² LEN/EDF/WAO guideline for the management of urticaria.

Synthesis and 5-HT3 receptor affinity of new quinolinecarboxylic acid derivatives

A series of quinolinecarboxylic acid amides and an ester with a quinuclidine moiety were synthesized and their in vitro affinities at 5-HT3, 5-HT4, and D2 receptors evaluated by radioligand binding assays. Highest affinity at 5-HT3 receptor corresponded to derivative 5 with Ki = 9.9 nM and with selectivity over 5-HT4 and D2 receptors. Compounds displayed moderate 5-HT3 antagonist activity (ED50 = 10.5-21.5 microg/kg i.v.). The obtained data suggest that the 5-HT3 receptor sites can accommodate the acyl group of the 2-quinoline derivatives. The results indicate the existence of an optimal distance between the lone electron pair of the quinoline nitrogen atom and the azabicyclic nitrogen atom, and a no-pharmacophoric pocket in the 5-HT3 receptor which would hold the fragment at the position 4 of the quinoline ring.

2,3-Dihydro-2-oxo-1H-benzimidazole-1-carboxamides with selective affinity for the 5-HT(4) receptor: synthesis and structure-affinity and structure-activity relationships of a new series of partial agonist and antagonist derivatives

A series of 2,3-dihydro-2-oxo-1H-benzimidazole-1-carboxamide derivatives bearing a piperazine moiety was synthesized. Their in vitro 5-HT(4), 5-HT(3), and D(2) receptors affinities were evaluated by radioligand binding assay. For selected compounds functional studies at the 5-HT(4) receptor were made by using precontracted (by carbachol) preparations of rat esophageal tunica muscularis mucosae (TMM). The influence of the 3-substituent of the benzimidazole ring, the 4-substituent of the piperazine moiety, and the alkylene spacer was studied. Compounds with an ethyl or a cyclopropyl substituent in the 3-position of the benzimidazole ring showed moderate to high affinity (K(i) = 6.7-75.4 nM) for the 5-HT(4) receptor with selectivity over 5-HT(3) and D(2) receptors and moderate antagonist activity (pK(b) = 6.19-7.73). Compounds with an isopropyl substituent in the 3-benzimidazole position exhibited moderate and selective 5-HT(4) affinity (K(i) >/= 38.9 nM) and a partial agonist activity (5a, i.a. = 0.94) higher than that of the reference compound BIMU 8 (i.a. = 0.70). This reversal of the pharmacological activity due only to a small structural difference might confirm the existence of two binding sites on the 5-HT(4) receptor. In the alkylene spacer, a two-methylene chain is favorable to optimize the affinity and the antagonist or the partial agonist activity. In the ethyl and cyclopropyl series, 5-HT(4) antagonist activity seems to be unrelated to the size of the 4-substituent of the piperazine moiety, whereas a methyl group is optimal for high partial agonist activity in the isopropyl series; however, the presence of a butyl substituent is a favorable pattern for 5-HT(4) antagonism and even causes a reversal of the pharmacological profile in the isopropyl series (5h, pK(b) = 7.94). N-Butyl quaternization of 5a led to an improvement in affinity for the 5-HT(4) receptor and mantained the high partial agonist activity (5r, K(i) = 66.3 nM, i.a. = 0.93).

New 2-piperazinylbenzimidazole derivatives as 5-HT3 antagonists. Synthesis and pharmacological evaluation

A series of 2-piperazinylbenzimidazole derivatives were prepared and evaluated as 5-HT3 receptor antagonists. Their 5-HT3 receptor affinities were evaluated by radioligand binding assays, and their abilities to inhibit the 5-HT-induced Bezold-Jarisch reflex in anesthetized rats were determined. Compound 7e (lerisetron, pKi = 9.2) exhibited higher affinity for the 5-HT3 receptor than did tropisetron and granisetron, while compound 7q (pKi = 7.5) had very low affinity for this receptor, showing that substitution on the N1 atom of the benzimidazole ring is essential for affinity and activity. The effect of substitution on the aromatic ring of benzimidazole by several substituents in different positions is also discussed. A strong correlation between the 5-HT3 antagonistic activity of the studied compounds and the position of substitution on the aromatic ring was established. Thus, while the 4-methoxy derivative 7m showed weak affinity for the 5-HT3 receptor (pKi = 6.7), the 7-methoxy derivative 7n exhibited the highest affinity (pKi = 9.4). Compounds 7e and 7n are now under further investigation as drugs for the treatment of nausea and emesis evoked by cancer chemotherapy and radiation.

New (2-methoxyphenyl)piperazine derivatives as 5-HT1A receptor ligands with reduced alpha 1-adrenergic activity. Synthesis and structure-affinity relationships

New 2-(methoxyphenyl)piperazine derivatives 1 and 2 containing a terminal heteroaryl or cycloalkyl amide fragment were prepared and their 5-HT1A affinities evaluated by radioligand binding assays. The influence of the alkyl chain length or the amide group on affinity was evaluated. A four-carbon chain appears to be optimal when the amide fragment is a heteroaryl group. Derivatives with a cycloalkyl moiety displayed maximum affinity in the two methylene chain series. Electronic distribution within the amide region seems to have an influence on affinity in heteroaryl derivatives. Replacement of the heteroaryl moiety by a cycloalkyl group led to compounds with enhanced affinity. Increasing the lipophilicity of the cycloalkyl derivatives by annelation and/or saturation increased their affinity for the 5-HT1A sites. Compounds with cis-bicyclo[3.3.0]octane (2a, 2c), norbornane (2f, 2g), and norbornene (2h, 2i) groups bind at 5-HT1A sites with 2-10-fold higher affinity than NAN-190. Antagonist activity at alpha 1-adrenergic receptors was evaluated for compounds with high affinity at 5-HT1A sites. Compounds 2a, 2c, 2f, 2g, and 2h strongly bind (Ki = 0.12-0.63 nM) at 5-HT1A receptors and are devoid of antagonist activity at alpha 1-adrenergic receptors.

Synthesis and structural, conformational, biochemical, and pharmacological study of new compounds derived from tropane-3-spiro-4'(5')-imidazoline as potential 5-HT3 receptor antagonists

A series of tropane-3-spiro-4'(5')-imidazolines was synthesized and studied by 1H and 13C NMR spectroscopy, and the crystal structure of 2'-(1H-indol-3-yl)tropane-3-spiro-4'(5')-imidazoline hydrochloride 5(6)f was determined by X-ray diffraction. In CD3OD solution, compounds 5(6)a-f display the same preferred conformation. The pyrrolidine and piperidine rings adopt an envelope conformation flattened at N8 and a distorted chair conformation puckered at N8 and flattened at C3, respectively, with the N-substituent in the equatorial position with respect to the piperidine ring. This conformation is similar to that observed for compound 5(6)f in the solid state. From binding studies on the compounds synthesized, compound 5(6)d demonstrated the ability to efficiently displace the binding of [3H]GR65630 to bovine brain area postrema membranes to an extent comparable to MDL 72222. In the von Bezold-Jarisch reflex, compound 5(6)d was equipotent with metoclopramide. It is, therefore, likely that the imidazoline ring may provide a useful bioisosteric replacement for the carbonyl group in 5-HT3 antagonists.

Evaluation of bronchospasmolytic, antiallergic, anti-inflammatory, mucolytic and antitussive activities of decasilate in experimental models

The bronchospasmolytic, antiallergic, anti-inflammatory, mucolytic and antitussive activities of 8-(2-phenylethyl)-1-oxa-diazaspiro[4,5]decan-2-one 2-tiophenecarboxylate (decasilate, CAS 76652-72-7) have been evaluated using different experimental models. 1. Decasilate showed a remarkable spasmolytic activity against histamine-induced contractions in the isolated guinea-pig tracheal preparation with an IC50 of 2.7 x 10(-6) mol/l. In addition, the oral administration of decasilate (5-30 mg.kg-1) significantly reduced the histamine aerosol-induced bronchospasm in guinea-pigs. 2. Decasilate had a preventive effect against antigen-induced contractions of ileum segments from sensitized guinea-pigs (EC50 8.0 x 10(-6) mol/l) and relaxed them when added after the antigen challenge (IC50 9.5 x 10(-7) mol/l). 3. Both carrageenin- and dextran-induced rat hind paw oedemas were significantly reduced by the oral administration of decasilate with ED50 values of 169.5 and 34.5 mg.kg-1, respectively. However, it was ineffective against the cotton pellet-induced granuloma in the rat. 4. Furthermore, decasilate had a significant mucolytic activity in rabbits and reduced the number of tussive seizures induced by an aerosol of citric acid in guinea-pigs. The pharmacological profile of decasilate suggests that it might be useful in the management of chronic bronchitis.