Calcitonin gene-related peptide (CGRP) is one of the most potent endogenous vasodilators known. This peptide is increased during migraine attacks and has been implicated in the pathogenesis of migraine headache. Here we report on the ®rst small molecule selective CGRP antagonist: BIBN4096BS. In vitro, this compound is extremely potent at primate CGRP receptors exhibiting an a nity (K i ) for human CGRP receptors of 14.4+6.3 (n=4) pM. In an in vivo model, BIBN4096BS in doses between 1 and 30 mg kg 71 (i.v.) inhibited the e ects of CGRP, released by stimulation of the trigeminal ganglion, on facial blood¯ow in marmoset monkeys. It is concluded that BIBN4096BS is a potent and selective CGRP antagonist.
Telmisartan is a potent, long-lasting, nonpeptide antagonist of the angiotensin II type-1 (AT 1 ) receptor that is indicated for the treatment of essential hypertension. It selectively and insurmountably inhibits stimulation of the AT 1 receptor by angiotensin II without affecting other receptor systems involved in cardiovascular regulation. Very high lipophilicity, a unique feature of telmisartan, coupled with a high volume of distribution, indicate that the compound offers the clinically important advantage of good tissue penetration. Telmisartan is not a prodrug and has a longer terminal elimination half-life than other commercially available sartans (~24 h), making it suitable for once-daily dosing. The compound is not metabolized by cytochrome P450 isoenzymes and has a low risk for P450-based drug interactions. In animal models, telmisartan exhibits pronounced cardioand reno-protective effects in animals with severe, essential hypertension. In clinical studies, telmisartan shows comparable antihypertensive activity to members of other major antihypertensive classes, such as ACE inhibitors, beta blockers and calcium antagonists. These trials have confirmed the placebo-like safety and tolerability of telmisartan in hypertensive patients. Based on these data, telmisartan offers advantages over other sartans and represents an important new treatment option for hypertension.
The NAD(+)-dependent protein deacetylase SIRT1 is linked to cellular survival pathways by virtue of keeping the tumor suppressor gene p53 and members of the forkhead transcription factor family deacetylated. To validate SIRT1 as a therapeutic anti-cancer target, we performed immunohistochemistry experiments to study the in vivo expression of SIRT1 in cancer specimens. We show that human SIRT1 is highly expressed in cancer cell lines as well as in tissue samples from colon carcinoma patients. Interestingly, there is a strong cytosolic component in the SIRT1 expression pattern. We further characterized SIRT1 in p53-wild-type and -mutant cell lines and show that SIRT1 mRNA-knockdown leads to a p53-independent decrease of cell proliferation and induction of apoptosis. In addition, SIRT1 expression has been found to be inducible upon DNA damage. A previously discovered small molecule SIRT1 inhibitor with nanomolar in vitro activity has been tested in cancer relevant assays. The SIRT1 inhibitory compound showed no potent anti-proliferative activity despite hitting its molecular target within tumor cells. From these studies we conclude that it may not be sufficient to block the catalytic function of SIRT1, and that its survival effects may be mainly brought about by means other then the deacetylase function. The increased cytosolic expression of SIRT1 in cancer cells could be an indicator of such novel functions.
CGRP Y0-28-37 is known as a selective CGRP1 receptor antagonist. In order to elucidate the essential requirements for its receptor interaction, we performed a variety of systematic approaches by modifying the C-terminal segments CGRP Y0-28-37 and CGRP 27-37. N-Terminal and C-terminal segments have been synthesized, as well as chimeras which combine segments of CGRP, adrenomedullin, and amylin. Furthermore, we carried out an Ala scan, a Phe scan, a D-amino acid scan and a Pro scan of CGRP 27-37. Additionally, single amino acids were replaced by those with similar biophysical properties. Receptor binding studies of all analogs were performed at human neuroblastoma cells SK-N-MC, which selectively express the hCGRP1 receptor. On the basis of the obtained results, we synthesized a series of ligands with multiple amino acid replacements in order to optimize the exchange at each position. This approach yielded to a series of high affinity ligands, including [D31,P34,F35] CGRP 27-37 which exhibits a 100-fold increased affinity compared to the unmodified segment. So far, this is the smallest CGRP analog that shows affinity in the nanomolar range.
Starting from the recently reported nonpeptidic angiotensin II (AII) receptor antagonists DuP753 (1) and Exp 7711 (2), we have designed and investigated novel substituted benzimidazoles. Systemic variation of several substituents at the benzimidazole ring positions 4-7 led to the finding that substitution in position 6 with acylamino groups results in highly active AII antagonists. Compounds with 6-membered lactam or sultam substituents in position 6 of benzimidazole showed receptor activities in the low nanomolar range but were only weakly active when given orally to rats. In contrast, analogous substitution of the benzimidazole moiety with basic heterocycles resulted in potent AII antagonists which were also well absorbed after oral application. The most active compound of this series, 33 (BIBR 277), was selected as a candidate for clinical development. On the basis of molecular modeling studies a binding model of this new class of AII antagonists to the AT1 receptor is proposed.
The pharmacological profile of BIBR 277, 4′‐[(1,4′‐dimethyl‐2′‐propyl[2,6′‐bi‐1H‐benzimidazol]‐1′‐yl)methyl]‐[1,1′‐biphenyl]‐2‐carboxylic acid, a novel, nonpeptide angiotensin II receptor antagonist has been investigated by use of receptor binding studies, enzymatic assays, functional in vitro assays in rabbit aorta as well as in vivo experiments in pithed, anaesthetized and conscious rats. BIBR 277 potently interacted with rat AT1 receptors (Ki 3.7 nm). Competitive receptor interaction was shown by radioligand saturation experiments performed in the presence of BIBR 277. The failure to inhibit radioligand binding to AT2 sites demonstrates the selectivity of BIBR 277 for AT1 receptors. This is further substantiated by the findings that BIBR 277 neither interacted with other receptor systems investigated nor affected the activity of components of the human renin‐angiotensin system, such as plasma renin or serum converting enzyme. In rabbit aorta, BIBR 277 had no agonistic properties and was shown to be an insurmountable antagonist of angiotensin II‐induced contractions (KB 0.33 nm). The antagonistic effect persisted even after several wash‐out procedures. However, this interaction was not irreversible since the insurmountable antagonism was concentration‐dependently reversed when BIBR 277 (0.1 μm) and the surmountable antagonist, losartan (0.1 and 1.0 μm) were incubated simultaneously. The specificity of BIBR 277 for the AT1 receptor was further substantiated in this preparation since micromolar concentrations of BIBR 277 neither affected potassium chloride and noradrenaline‐induced contractions nor acetylcholine‐mediated tissue relaxation. In pithed rats, i.v. administration of BIBR 277 (0.1, 0.3 and 1.0 mg kg−1) shifted the dose‐pressor response curve to angiotensin II dose‐dependently to the right with ED50 values of 0.23 μg kg−1 (control) and 1.4 μg kg−1, 4.7 μg kg−1 and 20 μg kg−1, respectively. As observed in the in vitro experiments no agonistic effect was detected and the maximum of the blood pressure response to angiotensin II at the highest dose of BIBR 277 was decreased by 29%. In anaesthetized rats, bolus i.v. administration of 0.1, 0.3 and 1.0 mg kg−1 BIBR 277 attenuated the blood pressure response to bolus i.v. injections of angiotensin II (0.1 μg kg−1). At the highest dose an almost complete blockade was observed even after 2 h. Single oral administration of BIBR 277 (0.3 and 1.0 mg kg−1) to conscious, chronically instrumented renovascular hypertensive rats dose‐dependently decreased the mean arterial blood pressure by 15 and 30 mmHg, respectively. At the higher dose a significant antihypertensive effect was maintained for more than 24 h. Moreover, consecutive daily dosing of 1 mg kg−1 orally resulted in a sustained reduction in blood pressure over the 4 day observation period. It is concluded that BIBR 277 is an effective and selective angiotensin II antagonist with antihypertensive activity after oral administration.
The nicotinamide adenine dinucleotide (NAD(+))-dependent protein deacetylase SIRT1 has been linked to fatty acid metabolism via suppression of peroxysome proliferator-activated receptor gamma (PPAR-gamma) and to inflammatory processes by deacetylating the transcription factor NF-kappaB. First, modulation of SIRT1 activity affects lipid accumulation in adipocytes, which has an impact on the etiology of a variety of human metabolic diseases such as obesity and insulin-resistant diabetes. Second, activation of SIRT1 suppresses inflammation via regulation of cytokine expression. Using high-throughput screening, the authors identified compounds with SIRT1 activating and inhibiting potential. The biological activity of these SIRT1-modulating compounds was confirmed in cell-based assays using mouse adipocytes, as well as human THP-1 monocytes. SIRT1 activators were found to be potent lipolytic agents, reducing the overall lipid content of fully differentiated NIH L1 adipocytes. In addition, the same compounds have anti-inflammatory properties, as became evident by the reduction of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha). In contrast, a SIRT1 inhibitory compound showed a stimulatory activity on the differentiation of adipocytes, a feature often linked to insulin sensitization.
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