Non-peptide angiotensin type 1 receptor antagonists in the treatment of hypertension

Prediction of Degradation Profiles for Various Sartans under Solvent-Free Mechanochemical Conditions

For the approval of a drug, the stability data must be submitted to regulatory authorities. Such analyses are often time-consuming and cost-intensive. Forced degradation studies are mainly carried out under harsh conditions in the dissolved state, often leading to extraneous degradation profiles for a solid drug. Oxidative mechanochemical degradation offers the possibility of generating realistic degradation profiles. In this study, a sustainable mechanochemical procedure is presented for the degradation of five active pharmaceutical ingredients (APIs) from the sartan family: losartan potassium, irbesartan, valsartan, olmesartan medoxomil, and telmisartan. High-resolution mass spectrometry enabled the detection of impurities already present in untreated APIs and allowed the elucidation of degradation products. Significant degradation profiles could already be obtained after 15-60 min of ball milling time. Many of the identified degradation products are described in the literature and pharmacopoeias, emphasizing the significance of our results and the applicability of this approach to predict degradation profiles for drugs in the solid state.

High affinity rigidified AT2 receptor ligands with indane scaffolds

Rigidification of the isobutyl side chain of drug-like AT2 receptor agonists and antagonists that are structurally related to the first reported selective AT2 receptor agonist 1 (C21) delivered bioactive indane derivatives. Four enantiomer pairs were synthesized and the enantiomers were isolated in an optical purity >99%. The enantiomers 7a, 7b, 8a, 8b, 9a, 9b, 10a and 10b bind to the AT2 receptor with moderate (K i = 54-223 nM) to high affinity (K i = 2.2-7.0 nM). The enantiomer with positive optical rotation (+) exhibited the highest affinity at the receptor. The indane derivatives 7b and 10a are among the most potent AT2 receptor antagonists reported so far. As illustrated by the enantiomer pairs 7a/b and 10a/b, an alteration at the stereogenic center has a pronounced impact on the activation process of the AT2 receptor, and can convert agonists to antagonists and vice versa.

Comparison of Monotherapy with Irbesartan 150 mg or Amlodipine 5 mg for Treatment of Mild-to-Moderate Hypertension

Objective. The primary objective of this study was to compare the antihypertensive efficacy of the angiotensin II receptor blocker irbesartan 150 mg and the calcium channel blocker amlodipine 5 mg in the treatment of patients with seated diastolic blood pressure (DBP) 95—110 mmHg.

Design. Multicentre, randomised, double-blind, comparative pilot study.

Methods. Subjects were 18—65 years of age, with DBP 95—110 mmHg, and of non-African American origin. Following a three-week, single-blind, placebo lead-in period, 181 subjects were randomised in a 1:1 ratio to receive once-daily irbesartan 150 mg (n=89) or amlodipine 5 mg (n=92) for four weeks. Trough (24±3 hours post-dosing) BP measurements were obtained at baseline and at Weeks 2 and 4 under standardised, controlled conditions. Response was defined as DBP <90 mmHg or a reductionfrom baseline of ≥10 mmHg.

Results. After four weeks of treatment, the mean (±SE) decrease from baseline in DBP was 9.4±0.6 mmHg in the irbesartan group vs. 9.6±0.6 mmHg in the amlodipine group (p=0.806). The mean decrease from baseline in seated systolic BP was 12.2±1.0 mmHg in the irbesartan group vs. 12.0±1.0 mmHg in the amlodipine group (p=0.885). Overall, 62% of subjects in the irbesartan group and 63% in the amlodipine group had a response (p=0.609), and 54% and 56% of patients (p=0.596), respectively, had their DBP normalised (<90 mmHg). Adverse events were reported by 21.3% of patients receiving irbesartan and 20.7% receiving amlodipine.

Conclusions. Irbesartan 150 mg demonstrated comparable efficacy to amlodipine 5 mg, thereby confirming its value as an antihypertensive treatment option in non-African American patients with DBP 95—110 mmHg.

Postnatal acute renal failure after fetal exposure to angiotensin receptor blockers

Maternal hypertensive treatment with angiotensin receptor blockers (ARBs) during the second and third trimester of pregnancy is associated with several fetal and neonatal complications, and potential adverse outcomes. We report a neonate presenting with transient renal acute failure during the first days of life after maternal treatment with ARBs. Women who became pregnant while taking one of these drugs must modify antihypertensive therapy with a different class drug as soon as pregnancy is recognised.

Pharmacokinetics of CS-866, a New Angiotensin II Receptor Blocker, in Healthy Subjects

CS-866, a novel angiotensin II receptor blocker, is rapidly and completely metabolized to RNH-6270, its active metabolite. The pharmacokinetics of RNH-6270 following oral CS-866 or intravenous RNH-6270 administration was determined in 104 healthy male volunteers. The pharmacokinetics of RNH-6270 was linear over dose ranges of 1 to 32 mg (intravenous RNH-6270 administration) and 10 to 160 mg (oral CS-866 administration). The time to maximum plasma concentration of RNH-6270 after oral CS-866 administration ranged from 1.4 to 2.8 hours, and the terminal elimination half-life ranged from 12 to 18 hours. Absolute bioavailability of RNH-6270 after oral administration of CS-866 was 26%. Administration of CS-866 once daily for 10 days did not result in drug accumulation. When administered intravenously, RNH-6270 has a volume of distribution of 15 to 25 L. Approximately 35% to 50% of RNH-6270 is excreted unchanged in the urine. CS-866 was safe and well tolerated at doses of up to 160 mg/day.

Angiotensin-II mediates nonmuscle myosin II activation and expression and contributes to human keloid disease progression

Aberrant fibroblast migration in response to fibrogenic peptides plays a significant role in keloid pathogenesis. Angiotensin II (Ang II) is an octapeptide hormone recently implicated as a mediator of organ fibrosis and cutaneous repair. Ang II promotes cell migration but its role in keloid fibroblast phenotypic behavior has not been studied. We investigated Ang II signaling in keloid fibroblast behavior as a potential mechanism of disease. Primary human keloid fibroblasts were stimulated to migrate in the presence of Ang II and Ang II receptor 1 (AT₁), Ang II receptor 2 (AT₂) or nonmuscle myosin II (NMM II) antagonists. Keloid and the surrounding normal dermis were immunostained for NMM IIA, NMM IIB, AT₂ and AT₁ expression. Primary human keloid fibroblasts were stimulated to migrate with Ang II and the increased migration was inhibited by the AT₁ antagonist EMD66684, but not the AT₂ antagonist PD123319. Inhibition of the promigratory motor protein NMM II by addition of the specific NMM II antagonist blebbistatin inhibited Ang II-stimulated migration. Ang II stimulation of NMM II protein expression was prevented by AT₁ blockade but not by AT₂ antagonists. Immunostaining demonstrated increased NMM IIA, NMM IIB and AT₁ expression in keloid fibroblasts compared with scant staining in normal surrounding dermis. AT₂ immunostaining was absent in keloid and normal human dermal fibroblasts. These results indicate that Ang II mediates keloid fibroblast migration and possibly pathogenesis through AT₁ activation and upregulation of NMM II.

Development of selective non-peptide angiotensin II type 2 receptor agonists

The development of the first drug-like selective angiotensin II type 2 (AT(2)) receptor agonist (22) derived from the non-selective angiotensin II type 1 (AT( 1)) receptor/AT(2) receptor agonist L-162,313 is presented. Compound 22 with a K(i) value of 0.4 nM for the AT( 2) receptor and a K(i) > 10 microM for the AT(1) receptor induces outgrowth of neurite cells, stimulates p42/p44( mapk), enhances in vivo duodenal alkaline secretion in Sprague-Dawley rats and lowers the mean arterial blood pressure in anaesthetised spontaneously hypertensive rats. Thus, the peptidomimetic 22 exerts a similar biological response as the endogenous peptide angiotensin II after selective activation of the AT(2) receptor. In addition, Compound 22 has a bioavailability of 20-30% after oral administration and a half-life estimated to four hours in the rat. Compound 22 will therefore serve as a valuable research tool enabling studies of the function of the AT(2) receptor in more detail.

Blood pressure goal achievement with olmesartan medoxomil-based treatment: additional analysis of the OLMEBEST study

Aims

Guidelines recommend blood pressure (BP) in hypertensive patients should be <140 systolic BP (SBP) and <90 diastolic BP (DBP) mmHg. This analysis assessed goal rate achievement in hypertensive patients receiving olmesartan-based treatment in the OLMEBEST study.

Methods

Patients with essential hypertension (DBP ≥ 90 mmHg and <110 mmHg) received open-label olmesartan medoxomil 20 mg/day (n = 2306). After 8 weeks, patients with DBP ≥ 90 mmHg (n = 627) were randomized to 4 weeks’ double-blind treatment with olmesartan 40 mg/day monotherapy or olmesartan 20 mg/day plus hydrochlorothiazide (HCTZ) 12.5 mg/day. For this analysis, the numbers and proportions of patients who achieved SBP < 140 mmHg and/or DBP < 90 mmHg at the end of the 4 weeks were calculated.

Results

In patients who achieved DBP normalization (<90 mmHg) at week 8 (n = 1546) and continued open-label olmesartan 20 mg/day, 66.7% achieved SBP/DBP < 140/90 mmHg at Week 12. In patients who did not achieve DBP normalization at Week 8, 26.8% of those randomized to olmesartan 40 mg/day and 42.5% of those randomized to olmesartan 20 mg/day plus HCTZ 12.5 mg/day achieved a SBP/DBP < 140/90 mmHg at Week 12.

Conclusion

Olmesartan 40 mg/day and olmesartan 20 mg/day plus HCTZ 12.5 mg/day allow substantial proportions of patients to achieve BP goals.

Pharmacogenomics and antihypertensive drugs: a path toward personalized medicine

Pharmacogenomics focuses on genes and the transcriptome and proteome. It has the potential to enhance healthcare management by improving disease diagnosis and implementing treatments adapted to each patient. Previously, pharmacogenetics of candidate genes focused on clinical research. It is now extended by using genome-wide approaches to elucidate the inherited basis of differences between individuals in their response to drugs. We summarize relevant polymorphisms of genes involved in the pharmacokinetics and pharmacodynamics of antihypertensive drugs and we give an overview of the state of pharmacogenomic research in hypertension medicine. Even if things are getting better, current pharmacogenetic studies still lack power, adequate selection of candidate genes and knowledge of their functions at the physiological level. Finally, some specific end point phenotypes (i.e., peptides or proteins related to the metabolic cycle targeted by the drug) should be integrated to propose data that are easily applicable to personalized medicine.

Efficacy and tolerability of olmesartan medoxomil in patients with mild to moderate essential hypertension: the OLMEBEST Study

BACKGROUND AND OBJECTIVE

Achieving target BP is important to control the increased cardiovascular risk associated with uncontrolled hypertension. However, failure to respond to therapy is common with all classes of antihypertensive agents. Angiotensin II type 1 receptor antagonists (angiotensin receptor blockers [ARBs]) possess many of the positive features of angiotensin-converting enzyme inhibitors, with fewer adverse effects. However, many patients fail to respond adequately to low-dose monotherapy. This study examined whether olmesartan medoxomil dose titration and olmesartan medoxomil/hydrochlorothiazide combination therapy were therapeutically equivalent in patients with mild to moderate essential hypertension who had shown an inadequate response to low-dose olmesartan medoxomil monotherapy.

METHODS

This was a prospective, parallel group, partially randomised, double-blind study set in 463 centres in nine European countries. 2306 male and female adult patients aged 18-75 years with mild to moderate essential hypertension (sitting diastolic BP [DBP] > or =90mm Hg and <110mm Hg) were enrolled. All enrolled patients received open-label olmesartan medoxomil 20mg once daily for 8 weeks. At the end of this period, patients whose BP had not normalised (sitting DBP > or =90mm Hg) were randomised to receive olmesartan medoxomil monotherapy (40mg once daily, n = 302) or olmesartan medoxomil (20mg once daily)/hydrochlorothiazide (12.5mg once daily) combination therapy (n = 325) for 4 weeks. The main outcome measure was change in mean sitting DBP during randomised treatment.

RESULTS

After 8 weeks of open-label treatment with olmesartan medoxomil 20 mg/day, 76% of patients showed a DBP response (sitting DBP <90mm Hg or reduction of > or =10mm Hg). During the randomised phase of the study, both treatments were associated with further improvements in sitting SBP/DBP: a reduction of 5.3/5.1mm Hg with olmesartan medoxomil 40 mg/day, and a reduction of 10.8/7.9mm Hg with olmesartan medoxomil/hydrochlorothiazide combination therapy. Final mean BPs of 145.3/90.9mm Hg (olmesartan medoxomil 40 mg/day) and 140.7/88.7mm Hg (olmesartan medoxomil 20mg + hydrochlorothiazide) were achieved, compared with a mean BP of 160.8/100.5mm Hg at baseline. The two treatments were not therapeutically equivalent. Sitting DBP showed a response and was normalised (<90mm Hg) in 62% and 47% of olmesartan medoxomil monotherapy patients, respectively. In the combination therapy group, these endpoints were achieved by 71% (response) and 59% (normalisation) of patients. Treatment with olmesartan medoxomil 40 mg/day was associated with a lower frequency of adverse events than olmesartan medoxomil/hydrochlorothiazide combination therapy (21.5% vs 28.3%, respectively).

CONCLUSION

For patients who did not achieve adequate BP control after initial treatment with olmesartan medoxomil 20 mg/day, olmesartan medoxomil dose titration (to 40 mg/day) or addition of hydrochlorothiazide (12.5 mg/day) elicited a sitting DBP response in the majority of patients who had failed to respond to low-dose monotherapy, and normalisation of sitting DBP in approximately 50% of patients. Both these strategies represent effective and well tolerated treatment options in patients who show an inadequate response to low-dose monotherapy with olmesartan medoxomil.

Novel insights in the treatment of diabetic nephropathy

Diabetes is currently one of the leading causes of end-stage renal failure requiring renal replacement therapy in the Western World. About 15% to 20% of type 1 diabetic patients and 30% to 40% of type 2 diabetic patients will eventually develop end-stage renal failure. To prevent the development or progression of diabetic kidney disease, good glycaemic control remains the cornerstone in the management of diabetic patients. Beyond glycaemic control, other metabolic factors have been shown to be involved in the development of diabetic kidney disease, i.e. advanced glycation endproducts (AGEs) and the aldose reductase pathway. Furthermore, an adequate control of high blood pressure and treatment of microalbuminuria are major therapeutic targes. To achieve adequate blood pressure control, a combination therapy with different classes of antihypertensive agents is often necessary, especially including angiotensin-converting enzyme inhibitors and angiotensin receptor blockers. Other vasoactive factors involved in diabetic nephropathy such as endothelin and nitric oxide will be covered briefly. Besides hyperglycaemia and high blood pressure, other risk factors have been identified in the development or progression of diabetic kidney disease: smoking, hyperlipidaemia, obesity and high protein intake. Their impact on renal function will be highlighted. Finally, recent research has also identified intracellular pathways such as the diacylglycerol-protein kinase C pathway and several growth factors, such as growth hormone, insulin-like growth factor, transforming growth factor-beta, vascular endothelial growth factor, and platelet derived growth factor as players in diabetic kidney disease.

Antihypertensive activity of angiotensin II AT1 receptor antagonists: a systematic review of studies with 24 h ambulatory blood pressure monitoring

OBJECTIVE

To perform a systematic review of the antihypertensive activity of the angiotensin II AT1 receptor antagonists (ARB).

METHODS

Studies in which blood pressure (BP) was measured using ambulatory BP monitoring for at least 24 h were collected from MEDLINE. Data for each treatment group, ARB, placebo or the drug used for its comparison were obtained from the selected studies. Only studies with a minimum of quality criteria were selected. The final study group contained 36 publications, with a total of 47 patient cohorts receiving ARB in monotherapy, 10 with placebo, 10 with amlodipine, and five with enalapril. The reduction in clinical and ambulatory BP during 24 h, day, night and the last 4-h period for each of the drugs analysed were calculated and adjusted by age, sex, number of participants and by the initial BP level.

RESULTS

The global antihypertensive activity of ARB differs from that observed with amlodipine in the sense that the magnitude of the reduction in the BP values does not essentially depend on the initial BP values nor on the dose used. When only ARB were considered, the drug used was a determinant for systolic BP reduction, whereas for diastolic BP the influence was on the BP reduction and the duration of the antihypertensive activity. The dose used had a particular influence on the duration of the antihypertensive activity for both systolic and diastolic BP.

CONCLUSION

Among the ARB, the influence is on duration more than on the magnitude of BP reduction. Dose, therefore, is an important factor in the duration of antihypertensive activity.

Future strategies for mitigation and treatment of chronic radiation-induced normal tissue injury

Until the mid-1990s, radiation-induced normal-tissue injury was generally assumed to be solely caused by the delayed mitotic death of parenchymal or vascular cells, and these injuries were held to be progressive and untreatable. From this assumption, it followed that postirradiation interventions would be unlikely to reduce either the incidence or the severity of radiation-induced normal tissue injury. It is now clear that parenchymal and vascular cells are active participants in the response to radiation injury, an observation that allows for the possibility of pharmacologic mitigation and/or treatment of these injuries. Mitigation or treatment of chronic radiation injuries has now been experimentally shown in multiple organ systems (eg, lung, kidney, and brain), with different pharmacologic agents (eg, angiotensin-converting enzyme inhibitors, pentoxifylline, and superoxide dismutase mimetics) and with seemingly different mechanisms (eg, suppression of the renin-angiotensin system and suppression of chronic oxidative stress). Unfortunately, the mechanistic basis for most of the experimental successes has not been established, and assessment of the utility of these agents for clinical use has been slow. Clinical development of pharmacologic approaches to mitigation or treatment of chronic radiation injuries could lead to significant improvement in survival and quality of life for radiotherapy patients and for victims of radiation accidents or nuclear terrorism.

Intraindividual Blood Pressure Responses to Angiotensin‐Converting Enzyme Inhibition and Angiotensin Receptor Blockade

This study aims to test the hypothesis that in some hypertensive subjects the blood pressure (BP) response to angiotensin-converting enzyme inhibition differs from that to angiotensin receptor blockade (ARB); a responder to angiotensin-converting enzyme inhibition may not respond to ARB or the opposite. A randomized, open-label, crossover, comparative trial of lisinopril 20 mg compared with telmisartan 80 mg (5 weeks per treatment period) was conducted in 32 untreated hypertensives using 24-hour ambulatory BP monitoring. Subjects were classified as "responders" and "nonresponders" using an arbitrary threshold of ambulatory BP response (> or =10 mm Hg systolic or > or =5 diastolic) or the median response achieved by each drug. No difference was detected between the drugs in their effect on ambulatory BP (mean difference 1.2+/-7.1/0.7+/-5.1 mm Hg, systolic/diastolic). Significant correlations were found between the antihypertensive responses to the two drugs (r=0.77, p<0.001). Using the arbitrary response criterion, there was a difference between the drugs in the responses in 28%/13% of subjects (9/4 patients) for systolic/diastolic BP (19%/25% using the median response criterion). These data suggest that in some hypertensive patients the BP response to angiotensin-converting enzyme inhibition may fail to predict the response to ARB. It appears that there are differences in the antihypertensive action of angiotensin-converting enzyme inhibitors and ARBs that may be clinically important.

Synthesis and Characterization of R2PNP(iBuNCH2CH2)3N: A New Bulky Electron-Rich Phosphine for Efficient Pd-Assisted Suzuki−Miyaura Cross-Coupling Reactions

Pro-azaphosphatrane 1a [P(iBuNCH2CH2)3N] reacts with iodine under mild conditions to give [IP(iBuNCH2CH2)3N]I in excellent yield, which on subsequent reaction with ammonia followed by deprotonation with KOtBu provided HN=P(iBuNCH2CH2)3N (3a) in quantitative yield. Reaction of 3a with R'2PCl afforded sterically bulky electron-rich phosphines of the type R'2PN=P(iBuNCH2CH2)3N (4) [R'=Ph (4a), iPr (4b), tBu (4c)]. The Pd(OAc)2/4c catalyst system was particularly efficient for the coupling of arylboronic acids with aryl bromides as well as aryl chlorides to give biaryls in excellent yields.

Highly Efficient Non-Palladium-Catalyzed Controlled Synthesis and X-ray Analysis of Functionalized 1,2-Diaryl-, 1,2,3-Triaryl-, and 1,2,3,4-Tetraarylbenzenes

A general, two-step, highly efficient synthesis of 1,2-diaryl-, 1,2,3-triaryl-, and 1,2,3,4-tetraarylbenzenes from simple stitching of alpha-oxo-ketene-S,S-acetals and active methylene compounds via a lactone intermediate is described. This procedure offers easy access to highly functionalized arylated benzenes that contain sterically demanding groups in good to excellent yields. The novelty of the procedure lies in the construction of aromatic compounds with the desired conformational flexibility along the molecular axis in a transition-metal-free environment through easily accessible precursors. Crystal analysis of these arylated benzene scaffolds showed that the peripheral aryl rings are arranged in a propeller-like fashion with respect to the central benzene ring. Examination of the crystal packing in the structure of a 1,2,3,4-tetraarylbenzene revealed an N...pi interaction between molecules related by a two-fold screw axis running in the direction of the a axis. Interestingly, the repeating array of N...pi interactions around the axis of this 1,2,3,4-tetraarylbenzene forces the molecules into a helical pattern.

Evaluation of enalapril+losartan treatment with cardiopulmonary exercise test in patients with left ventricular dysfunction

The aim of this study was to evaluate the effects of the combination of enalapril and losartan in patients with left ventricular systolic dysfunction by means of cardiopulmonary exercise test (CPET). Patients with left-ventricular systolic dysfunction and ejection fractions of 40% or less were included to the study. All patients were under the treatment of enalapril 20 mg once daily. The study group consisted of 20 patients (18 men, 2 women; mean age +/- standard deviation: 62.4 +/-6.5 years) and the comparison group consisted of 10 (8 men, 2 women; mean age 59.3 +/-11.9 years). The dose of 50 mg of losartan once daily was given additionally to the study patients. Breath-by-breath CPET was performed before administration of losartan and then 6-8 weeks later in the study group and 2 times with an interval of 6-8 weeks in the control group without any change in the treatment protocol. In the study group the average exercise times were 361 +/-192 and 454 +/-205 seconds (p = 0.001) before and after the study. Peak oxygen consumption ( VO2) values were 1,209 +/-366 and 1,284 +/-398 mL/minute before and after the study (p = 0.01). Anaerobic threshold VO2 values were 785 +/-187 and 855 +/-217 mL/minute before and after the study, respectively (p = 0.01). Peak heart rates (HR) were 141 +/-28 and 143 +/-22/minute (p = 0.35); peak VO2/HR values were 9.02 +/-3.1 and 9.3 +/-3 mL/minute (p = 0.4) before and after the study, respectively. On the other hand, in the control group, average exercise times were 556 +/-250 and 528 +/-251 seconds (p = 0.8); peak VO2 values were 1,502 +/-537 and 1,450 +/-501 mL/minute (p = 0.2); and anaerobic threshold VO2 values were 1,005 +/-338 and 975 +/-319 mL/min (p = 0.7), before and after the study respectively. At the highest comparable exercise stage for both tests in the study group the expired volume/oxygen consumption ( VE/ VO2) ratio declined from 35.1 +/-6.2 to 32.4 +/-5.6 (p = 0.007). VE values declined from 37.5 +/-10.9 to 33.9 +/-10.1 L (p = 0.02); heart rate declined from 140 +/-27 to 132 +/-21/minute (p = 0.02). No significant change was observed in the mentioned values for the control group. Addition of losartan to the standard therapy in patients with left ventricular systolic dysfunction improved exercise capacity and caused lower heart rate and ventilation requirements for the same exercise level.

Suzuki−Miyaura Cross-Coupling Reactions of Aryl Tellurides with Potassium Aryltrifluoroborate Salts

[reaction: see text] Palladium(0)-catalyzed cross-coupling between potassium aryltrifluoroborate salts and aryl tellurides proceeds readily to afford the desired biaryls in good to excellent yield. The reaction seems to be unaffected by the presence of electron-withdrawing or electron-donating substituents in both the potassium aryltrifluoroborate salts and aryl tellurides partners. Biaryls containing a variety of functional groups can be prepared. A chemoselectivity study was also carried out using aryl tellurides bearing halogen atoms in the same compound. In addition, this new version of the Suzuki-Miyaura cross-coupling reaction was monitored by electrospray ionization mass spectrometry where some reaction intermediates were detected and analyzed.

Comparison of antihypertensive effects of an angiotensin-converting enzyme inhibitor, a calcium antagonist and a diuretic in patients with hypertension not controlled by angiotensin receptor blocker monotherapy

OBJECTIVE

To compare the additional antihypertensive effects of an angiotensin-converting enzyme inhibitor (ACEI), a dihydropyridine calcium antagonist and a diuretic in patients whose hypertension is not controlled by full-dose angiotensin receptor blocker (ARB) monotherapy.

DESIGN AND METHODS

Individuals with an ambulatory blood pressure (ABP) that was not controlled by valsartan 160 mg once daily were allocated randomly to two groups: those in group A (n = 35) were assigned randomly to treatment with benazepril 20 mg once daily or chlorthalidone 12.5 mg once daily, whereas patients in group B (n = 29) were assigned randomly to benazepril 20 mg once daily or amlodipine 5 mg once daily. All individuals continued to receive background valsartan 160 mg once daily. After 5 weeks, patients crossed over to the alternative valsartan-based combination treatment of each group for a second 5-week period. Twenty-four-hour ABP monitoring was performed before the random allocation to groups and at the end of each randomized combination pharmacotherapy period.

RESULTS

Sixty-four individuals completed the study: 32 men and 32 women (mean +/- SD age 48.2 +/- 7.9 years, average 24-h ABP on valsartan monotherapy 143.4 +/- 12.6/87.7 +/- 7.8 mmHg). Significant additional antihypertensive effects on the average 24-h ABP were obtained with benazepril (8.6 +/- 8.8/6.3 +/- 6.7 mmHg), amlodipine (15.2 +/- 12.9/9.9 +/- 6.8 mmHg) and chlorthalidone (13.5 +/- 11.6/9.5 +/- 7.7 mmHg) (P < 0.001 for all additional antihypertensive effects). The additional effects of amlodipine and chlorthalidone added to valsartan were approximately 6/3.5 mmHg (P < 0.05) greater than that of benazepril.

CONCLUSIONS

In patients in whom hypertension was not controlled by full-dose ARB monotherapy, a diuretic, a calcium antagonist or an ACE inhibitor provided significant additional antihypertensive effect. The antihypertensive effects of the ARB-diuretic and the ARB-calcium antagonist combinations were superior to that of the ARB-ACE inhibitor combination.

Angiotensin II receptor antagonist treatment during pregnancy

Angiotensin II (A-II) is the main effector of the renin-angiotensin system. A-II functions by binding its type 1 (AT1) receptors to cause vasoconstriction and retention of sodium and fluid. Several AT1 receptor antagonists-a group of drugs collectively called "sartans"-have been marketed during the past few years for treatment of hypertension and heart failure. At least 15 case reports describe oligohydramnios, fetal growth retardation, pulmonary hypoplasia, limb contractures, and calvarial hypoplasia in various combinations in association with maternal losartan, candesartan, valsartan, or telmisartan treatment during the second or third trimester of pregnancy. Stillbirth or neonatal death is frequent in these reports, and surviving infants may exhibit renal damage. The fetal abnormalities, which are strikingly similar to those produced by maternal treatment with angiotensin-converting enzyme (ACE) inhibitors during the second and third trimesters of pregnancy, are probably related to extreme sensitivity of the fetus to the hypotensive action of these drugs. Very little information is available regarding the outcome of human pregnancies in which the mother was treated with an AT1 receptor antagonist during the first trimester, but animal studies have not demonstrated teratogenic effects after maternal treatment with large doses of AT1 receptor antagonists during organogenesis. We conclude that pharmacological suppression of the fetal renin-angiotensin system through ACE inhibition or AT1 receptor blockade seems to disrupt fetal vascular perfusion and renal function. We recommend that maternal treatment with AT1 receptor antagonists be avoided during the second and third trimesters of pregnancy and that women who become pregnant while taking one of these medications be changed to an antihypertensive drug of a different class as soon as the pregnancy is recognized.

From hyperglycemia to diabetic kidney disease: the role of metabolic, hemodynamic, intracellular factors and growth factors/cytokines

At present, diabetic kidney disease affects about 15-25% of type 1 and 30-40% of type 2 diabetic patients. Several decades of extensive research has elucidated various pathways to be implicated in the development of diabetic kidney disease. This review focuses on the metabolic factors beyond blood glucose that are involved in the pathogenesis of diabetic kidney disease, i.e., advanced glycation end-products and the aldose reductase system. Furthermore, the contribution of hemodynamic factors, the renin-angiotensin system, the endothelin system, and the nitric oxide system, as well as the prominent role of the intracellular signaling molecule protein kinase C are discussed. Finally, the respective roles of TGF-beta, GH and IGFs, vascular endothelial growth factor, and platelet-derived growth factor are covered. The complex interplay between these different pathways will be highlighted. A brief introduction to each system and description of its expression in the normal kidney is followed by in vitro, experimental, and clinical evidence addressing the role of the system in diabetic kidney disease. Finally, well-known and potential therapeutic strategies targeting each system are discussed, ending with an overall conclusion.

Impact of angiotensin II type 2 receptor blockade on experimental radiation nephropathy

In the rat, blockade of angiotensin II type 1 receptors diminishes the functional changes that occur after kidney irradiation. It has been hypothesized that some of the beneficial effects of angiotensin II type 1 blockers in renal disease are caused by a rise in angiotensin II that stimulates the angiotensin II type 2 receptor. If this hypothesis applied in this model, blockade of the type 2 receptor should exacerbate radiation nephropathy and/or counteract the beneficial effects of type 1 receptor blockade. To assess this hypothesis, rats were given total-body irradiation plus bone marrow transplantation and then treated for 12 weeks with a type 1 receptor blocker (L158,809), a type 2 blocker (PD123319), both blockers, or no blockers. Rats were assessed for renal function (proteinuria, hypertension, azotemia) and renal failure for up to 62 weeks. Contrary to the hypothesis, the type 2 blocker alone produced a temporary delay in the development of radiation nephropathy, and it substantially enhanced the efficacy of the type 1 blocker. This implies that both type 1 and type 2 angiotensin receptors need to be blocked to achieve the maximum level of prophylaxis of radiation nephropathy. We speculate that the beneficial effect of the angiotensin II type 2 receptor blocker is due to a reduction in radiation-induced renal cell proliferation or fibrosis.

Losartan's molecular basis of interaction with membranes and AT1 receptor

Physicochemical methods were used to study the thermal and dynamic changes caused by losartan in the membrane bilayers. In addition, molecular modeling was implemented to explore its topography both in membranes and AT(1) receptor. Its incorporation resulted in the modification of thermal profile of dipalmitoyl phosphatidylcholine (DPPC) bilayers in a concentration dependent way up to 20mol% as it is depicted from the combination of differential scanning calorimetry (DSC) and MAS data. In particular, the presence of losartan caused lowering of the phase transition temperature and abolishment of the pretransition. T(1) experiments revealed the location of the drug into the membrane bilayers. The use of a combination of biophysical methods along with docking experiments brought out a possible two-step mechanism which involves incorporation of losartan at the interface of membrane bilayers and diffusion in the upper parts of AT(1) receptor helices IV-VII.

First Reported Nonpeptide AT1Receptor Agonist (L-162,313) Acts as an AT2Receptor Agonist in Vivo

In this investigation, it is demonstrated that the first nonpeptide AT(1) receptor agonist L-162,313 (1), disclosed in 1994, also acts as an agonist at the AT(2) receptor. In anesthetized rats, administration of compound 1 intravenously or locally in the duodenum increased duodenal mucosal alkaline secretion, effects that were sensitive to the selective AT(2) receptor antagonist PD-123,319. The data strongly suggest that 1 is an AT(2) receptor agonist in vivo. To the best of our knowledge, this substance is the first nonpeptidic low-molecular weight compound with an agonistic effect mediated through the AT(2) receptor.

14C-labeled and large-scale synthesis of the angiotensin-(1-7)-receptor agonist AVE 0991 by cross-coupling reactions

The synthesis of (14)C-labeled AVE 0991 ((14)()C-1a) and large-scale synthesis of AVE 0991 (1a) are described. In the key step of the synthesis, the C-C coupling reaction of the imidazole (2) and thiophene (3) building blocks was studied under Suzuki and Stille reaction conditions, respectively. Suzuki reaction gave only moderate yields, whereas the best results were obtained under Stille reaction conditions with up to 64% yield.

Antihypertensive efficacy and safety of olmesartan medoxomil compared with amlodipine for mild-to-moderate hypertension

The antihypertensive efficacy of the angiotensin II receptor blocker olmesartan medoxomil has been shown to compare favourably with that of other antihypertensive agents. This randomized, double-blind study compared the antihypertensive efficacy of the starting dose of olmesartan medoxomil with that of the calcium channel blocker amlodipine besylate (amlodipine) in subjects with mild-to-moderate hypertension. Following a 4-week, single-blind, placebo run-in period, 440 subjects aged >/=18 years were randomized to the starting dose of olmesartan medoxomil (20 mg/day), amlodipine (5 mg/day), or placebo for 8 weeks. Subjects were evaluated by 24-h ambulatory blood pressure monitoring (ABPM) and by seated cuff blood pressure (BP) measurements at trough. The primary end point was the change from baseline in mean 24-h diastolic blood pressure (DBP) by ABPM at Week 8. Secondary end points included change from baseline in mean 24-h ambulatory systolic blood pressure (SBP) at 8 weeks, change from baseline in mean seated trough cuff DBP and SBP measurements, and response and control rates for DBP <90 and <85 mmHg. Control rates for SBP <140 and <130 mmHg were also calculated. Olmesartan medoxomil and amlodipine produced significantly greater reductions in ambulatory and seated DBP and SBP compared with placebo. Mean reductions in ambulatory and seated BP were similar between the two active agents; however, in the olmesartan medoxomil group, significantly more patients achieved the SBP goal of <130 mmHg and the DBP goal of <85 mmHg. Both drugs were well tolerated at the recommended starting dose. Although amlodipine was associated with a higher incidence of oedema, this did not reach statistical significance. Olmesartan medoxomil is an effective antihypertensive agent, with BP-lowering efficacy at the starting dose similar to that of amlodipine, and is associated with more patients achieving the rigorous BP goals of SBP <130 mmHg and DBP <85 mmHg.

Conformational and biological studies for a pair of novel synthetic AT1 antagonists: stereoelectronic requirements for antihypertensive efficacy

One of the major systems which interferes with the disease of hypertension, is the Renin Angiotensin Aldosterone System (RAS). The octapeptide hormone angiotensin II is the active product of RAS which causes vasoconstriction when binds to the AT(1) receptor. In the last years, there has been a development of drugs which block the Angiotensin II from binding the AT(1) receptor and are called AT(1) antagonists. In an effort to comprehend their stereoelectronic features, a study has been initiated to compare the conformational properties of drugs already marketed for the treatment of hypertension and others which are designed and synthesized in our laboratory possessing structural characteristics necessary for antihypertensive activity. In this study, two synthetic non-peptide AT(1) antagonists, are structurally elucidated and their conformational properties and bioactivity are compared to the prototype and first approved drug of this category in the market; losartan (trade name: COZAAR).

A review of olmesartan medoxomil monotherapy: antihypertensive efficacy similar to that of other angiotensin II receptor blocker/hydrochlorothiazide combinations?

Angiotensin II receptor blockers (ARBs) have been available in the United States since 1995. These agents have demonstrated antihypertensive efficacy at least similar to that of agents from other antihypertensive classes. Recent large-scale, randomized, controlled clinical trials have demonstrated that ARBs offer cardiovascular and renal protective benefits independent of their effects on systemic blood pressure (BP), which make them valuable as first-line antihypertensive agents, especially in high-risk patients. However, as is the case with other antihypertensive classes, monotherapy with the first-available ARBs (losartan potassium, valsartan, and irbesartan) may not provide sufficient BP reduction to achieve currently recommended BP goals in many patients. The diuretic hydrochlorothiazide is frequently added to enhance the ability of ARBs to lower BP. Several head-to-head comparison studies have shown differences in antihypertensive efficacy among the available ARBs. The newest ARB, olmesartan medoxomil, was recently compared with losartan potassium, irbesartan, and valsartan in a prospective, head-to-head, randomized trial. In this study, olmesartan medoxomil demonstrated a significantly greater reduction in diastolic BP, the primary end point, compared with the other three ARBs. Further, a review of the absolute reductions in diastolic BP achieved with olmesartan medoxomil monotherapy appears comparable to that of previously available ARBs when they are used in combination with hydrochlorothiazide. These comparisons may have important clinical implications regarding the optimal choice of first-line antihypertensive therapy.

Antihypertensive efficacy of olmesartan compared with other antihypertensive drugs

The therapeutic profile of olmesartan medoxomil, which is a recently developed angiotensin II (A II) receptor blocker, has been compared with four commonly used antihypertensive therapeutic drugs (atenolol, captopril, felodipine and losartan) in five separate multicentre, randomised, double-blind, parallel-group, phase III trials. The trials were designed to compare the efficacy of individually optimised dosages of olmesartan medoxomil and the comparator agent. The primary efficacy variable in all trials was the mean change from baseline to week 12 in trough mean sitting diastolic blood pressure (DBP). Olmesartan medoxomil (10-20 mg once daily (o.d.)) showed similar efficacy to atenolol (50-100 mg o.d.), both in patients with mild-to-moderate hypertension and, when given together with hydrochlorothiazide (HCTZ) 25 mg o.d., in patients with moderate-to-severe hypertension. Olmesartan medoxomil (20-40 mg o.d.) was also similar in efficacy to felodipine (5-10 mg o.d.) in reducing BP in patients with mild-to-moderate hypertension. Compared with captopril (12.5-50 mg twice daily (b.i.d.)) and losartan (50-100 mg o.d.), in patients with mild-to-moderate hypertension, olmesartan medoxomil (5-20 mg o.d. and 10-20 mg o.d., respectively) was significantly superior in terms of lowering DBP from baseline to week 12. In terms of the secondary efficacy variable, which was mean change from baseline to week 12 in trough mean sitting systolic BP, olmesartan showed significant superiority to atenolol, captopril and losartan in patients with mild-to-moderate hypertension. In the longer term, compared with losartan, a lower percentage of olmesartan-treated patients required concomitant HCTZ after 12 weeks of therapy. Olmesartan was well tolerated in all studies.

An ambulatory blood pressure monitoring study of the comparative antihypertensive efficacy of two angiotensin II receptor antagonists, irbesartan and valsartan

BACKGROUND

The primary objective of this study was to compare the change from baseline in mean diastolic ambulatory blood pressure (ABP) at 24 h post dose (trough measurement) after 8 weeks of treatment with irbesartan or valsartan in subjects with mild-to-moderate hypertension. Secondary objectives included comparing the mean changes from baseline in systolic ABP at trough; 24-h ABP; morning and night-time ABP; self-measured systolic blood pressure (SBP) and diastolic blood pressure (DBP); and office-measured SBP and DBP at trough.

DESIGN

After a 3-week, single blind, placebo lead-in period, 426 subjects were randomized to receive either irbesartan 150 mg or valsartan 80 mg for 8 weeks.

METHODS

Ambulatory blood pressure measurements were obtained at baseline and at week 8. Self-measured morning and evening DBP and SBP readings were obtained at home over a 7-day period at baseline and at week 8. Office-measured seated DBP and SBP measurements were obtained at trough, at baseline, and at week 8.

RESULTS

Irbesartan demonstrated significantly greater reductions than valsartan for mean change from baseline in diastolic ABP at trough (-6.73 versus -4.84 mmHg, respectively; P = 0.035). Irbesartan produced significantly greater reductions than valsartan for mean systolic ABP at trough (-11.62 versus -7.5 mmHg, respectively; P < 0.01) and for mean 24-h diastolic ABP (-6.38 versus -4.82 mmHg, respectively; P = 0.023) and systolic ABP (-10.24 versus -7.76 mmHg; P < 0.01). Irbesartan also produced significantly greater reductions than valsartan for office-measured seated DBP (-10.46 versus 7.28 mmHg, respectively; P < 0.01) and SBP (-16.23 versus -9.96 mmHg, respectively; P < 0.01) and for self-measured morning DBP (-6.28 versus -3.75 mmHg, respectively; P < 0.01) and SBP (-10.21 versus -6.97 mmHg, respectively; P < 0.01). Both drugs were well tolerated.

CONCLUSION

Irbesartan was more effective than valsartan in reducing DBP and SBP at trough and in providing greater overall 24-h blood pressure-lowering efficacy.

Synthesis and study of a cyclic angiotensin II antagonist analogue reveals the role of pi*--pi* interactions in the C-terminal aromatic residue for agonist activity and its structure resemblance with AT(1) non-peptide antagonists

The novel amide linked Angiotensin II (ANG II) cyclic analogue cyclo(3, 5) -[Sar(1)-Lys(3)-Glu(5)-Ile(8)] ANG II (18) has been designed, synthesized and bioassayed in anesthetized rabbits. The constrained cyclic analogue with a lactam amide bridge linking a Lys-Glu pair at positions 3 and 5 and possessing Ile at position 8, was synthesized by solution procedure using the maximum protection strategy. This analogue was found to be inhibitor of Angiotensin II. NMR spectroscopy coupled with computational analysis showed clustering between the side chains of the key aminoacids Tyr(4)-His(6)-Ile(8) similar to that observed with ANG II. The obtained data show that only pi*--pi* interactions observed in ANG II or its superagonist Sar(1) [ANG II] are missing. Therefore, it can be concluded that these interactions are essential for agonist activity. Conformational analysis comparisons between AT(1) antagonists losartan, eprosartan and irbesartan with C-terminal segment of cyclic compound 18 revealed structural similarities.

Discordant responses to two classes of drugs acting on the renin-angiotensin system

INTRODUCTION

Marked heterogeneity characterises blood pressure (BP)responses to antihypertensive drugs. The efficacy of drugs acting on the renin-angiotensin-aldosterone system(RAAS) is predicted (albeit weakly) by plasma renin activity (PRA) and it has been assumed that, within individuals, there would be concordance in efficacy between drugs acting at different sites to block the RAAS.

DESIGN

The present study was a randomised, double-blind,two-way, crossover study designed to evaluate intra-individual BP responses to an angiotensin II AT -receptor blocker (ARB), candesartan cilexetil, and anangiotensin-converting enzyme inhibitor (ACE-I), lisinopril, and to identify potential phenotypic characteristics of patients' responses to the drugs.

METHODS

92 patients with essential hypertension, (mean systolic/diastolic BP 160/101 mmHg) entered the trial,of whom 76 patients completed both treatments.

RESULTS

There was marked heterogeneity in response to the two drugs. 50% of patients responded (fall in diastolic BP of>10 mmHg or achieved diastolic pressure <90 mmHg)to both drugs; 16% were non-responders to both drugs; 20% responded to the ACE-I but not the ARB and 15% responded to the ARB but not to the ACE-I. Individual responses to the two drugs were poorly correlated (for diastolic pressure: r=0.19, p=0.11; for systolic pressure: r=-0.01, p=0.92). For the ACE-I, the fall in both systolic and diastolic BP was related to pre-treatment PRA (for diastolic pressure: r=0.31, p=0.008; for systolic pressure: r=0.24, p=0.04). In the case of the ARB, no relationship between the fall in BP and PRA was observed. These observations suggest that more complex mechanisms may be involved in BP reduction with ARBs than with ACE-I.

Insights into the functions of type 1 (AT1) angiotensin II receptors provided by gene targeting

The renin-angiotensin system (RAS) has a wide range of actions in biological processes ranging from development and reproduction to cardiovascular and renal functions. Most of these actions are mediated by the octapeptide hormone angiotensin II. The identified family of angiotensin II receptors is divided into two pharmacological classes: type 1 (AT1) and type 2 (AT2). The classically recognized actions of the RAS are primarily mediated by the AT1 subtype of angiotensin receptors, and these receptors are the targets of a new class of anti-hypertensive agents. In recent years, our understanding of the physiological functions of AT1 receptors has been advanced through the use of gene-targeting technology. In this review, we will summarize the emerging picture of AT1 receptor functions that has been provided by gene-targeting experiments.