Angiotensin receptor blocker selectivity at the AT1- and AT2-receptors: conceptual and clinical effects

LP2, a cyclic angiotensin-(1-7) analog extended with an N-terminal D-lysine, impairs growth of patient-derived xenografts of colorectal carcinoma in mice

LP2 is a 4, 7 D, L lanthionine-stabilized analog of angiotensin-(1-7), with an N-terminal D-lysine, resistant to breakdown by peptidases. It is a specific agonist of the angiotensin II type 2 receptor. Consistent with its high specificity and stability, LP2 has shown excellent safety and pharmacokinetics in a first-in-human clinical phase Ia trial. Here, based on strong rationales, we studied the capacity of LP2 to inhibit the growth of patient-derived xenografts of colorectal cancer in mice. Prior to efficacy studies, immunohistochemistry on an untreated tissue array demonstrated that the AT₂R expression is reduced in human colorectal cancer and in stroma when compared to tumor adjacent tissue. Subsequent studies demonstrated that LP2 at a subcutaneously injected dose as low as 0.2 µg/kg/day inhibited patient-derived xenografts of colorectal carcinoma in mice. Kinome analyses and validation of elected kinase inhibition indicated that LP2-mediated AT₂R stimulation inhibited PI3K/AKT/mTOR which resulted in apoptosis via CDKs. LP2 acted synergistically with 5-FU and the EGFR inhibitor erlotinib. Taken together, the extremely low dose of LP2 at which antitumor activity is exerted, the synergism with selected drugs and, together with its excellent specificity, safety and stability, warrant further evaluation of LP2's inhibitory potential of colorectal cancer.

Angiotensin II as a morphogenic cytokine stimulating renal fibrogenesis

Inhibitors of the renin-angiotensin-aldosterone system attenuate glomerulosclerosis and interstitial fibrosis. Although the mechanisms underlying their antifibrotic effects are complex, angiotensin II (Ang II) emerges as a major profibrogenic cytokine. Ang II modulates renal cell growth, extracellular matrix synthesis, and degradation by multiple fibrotic pathways. One of the main targets of Ang II in renal fibrosis is TGFβ. Many, but not all, of the stimulatory effects of Ang II on fibrogenesis depend on the induction of TGFβ and its downstream mediators of matrix accumulation, inflammation, and apoptosis. However because of the difficulty in targeting TGFβ, connective tissue growth factor β (CTGF), a downstream mediator of TGFβ, has become a more promising antifibrotic target. Ang II can directly induce expression of renal CTGF and mediate epithelial-mesenchymal transition. Other profibrotic factors stimulated by Ang II include endothelin-1, plasminogen activator inhibitor-1, matrix metalloproteinase (MMP)-2, and a tissue inhibitor of metalloproteinase-2. Finally, connections among Ang II, hypoxia, and the induction of hypoxia-inducible factor-1α contribute to fibrogenesis. A better understanding of the multiple morphogenic effects of Ang II may be necessary to develop better strategies to halt the progression of renal disease.

Vascular cognitive impairment: current concepts and clinical developments

Vascular cognitive impairment (VCI) comprises a range of cognitive disorders related to cerebral vessel disease and has generally replaced the term multi-infarct dementia. Despite the heterogeneity of the VCI construct, some clinical patterns can be discerned, which enable subtypes, such as mixed dementia and VCI-no dementia, to be recognised. Diagnostic criteria for vascular dementia do not encompass the full range of the VCI construct, and clinical investigators now recognise the need for harmonised standards to study the many manifestations of VCI seen in daily practice and to inform the development of diagnostic criteria. Although executive dysfunction is a recognised feature of VCI, some data suggest a less exclusive role than was previously proposed. VCI might be preventable, although the evidence for this is not as complete as it is for the prevention of stroke. Future studies into specific therapies for VCI will need to consider the clinical features and outcomes carefully.

Pharmacokinetic-pharmacodynamic modeling of telmisartan using an indirect response model in spontaneously hypertensive rats

AIM

To investigate the pharmacokinetic (PK) and the pharmacodynamic (PD) properties of telmisartan in spontaneously hypertensive (SH) rats using an indirect response and effect-compartment link models, and compare two PK-PD models fitting quality.

METHODS

The SH rats received a single oral dose of 2, 4, and 8 mg/kg of telmisartan. The plasma concentrations of telmisartan were determined by the liquid chromatography-mass spectrum method. The mean arterial blood pressure was measured to characterize the pharmacodynamics of telmisartan by tail-cuff manometry. The relationship for the telmisartan concentration-hypotensive effect in the SH rats was characterized using an indirect response model.

RESULTS

The PK parameters showed dose proportionality, with a long terminal half-life of 16 h, a clearance of 0.15 Lxkg( -1) xh( -1), and a volume of distribution of 5.36 Lxkg( -1) in the study. For the indirect response PD model, the estimated K(in) were 36.6, 34.1, and 32.8 %.h( -1), K(out) were 36.7, 34.6, and 31.9 h( -1); the IC(50) values were 86.2, 95.8, and 91.1 ngxmL( -1); and the area under the effect curve (AUEC) were 762.8, 1490.5, and 2086.2 mmHg.h at three doses, respectively. For the effect-compartment model, the K(eo) were 29.4, 33.8, and 28.7 h( -1); the IC(50) values were 78.2, 85.7, and 80.9 ngxmL(-1), and the AUEC were 781.5, 1602.8, and 2215.7 mmHg.h at three doses, respectively.

CONCLUSION

According to Akaike's information criterion values, the proposed indirect response model provided a more appropriate and good-fitting PK/PD characterization of telmisartan than the effect-compartment link model in SH rats.

An Open-Label Study Investigating the Efficacy and Safety of 12–96 Weeks of Telmisartan Treatment in Patients with Hypertension

This open-label, multicentre, multinational trial evaluated the efficacy and safety of telmisartan used alone or as add-on therapy in 2121 adults with mild-to-moderate essential hypertension. Patients received telmisartan 40-80 mg once daily for 12 weeks and could participate in the study for up to 96 weeks, or until a marketed supply of telmisartan became available. Mean change from baseline in mean seated trough diastolic blood pressure (DBP) after 12 weeks' treatment, the primary endpoint, was −11.8 mmHg in the intent-to-treat population. The corresponding mean change in mean seated trough systolic blood pressure (SBP) was −20.2 mmHg. Both changes were statistically significant. Mean DBP and SBP reductions were apparent from week 4 and maintained throughout the treatment period. Telmisartan was well tolerated; the most common adverse events were headache (6%) and dizziness (3%), and 10% of adverse events were considered drug-related. In conclusion, telmisartan is an effective and well-tolerated drug when used as monotherapy or add-on treatment in this broad population of patients.

Treatment of hypertension with an angiotensin II-receptor antagonist compared with an angiotensin-converting enzyme inhibitor: a review of clinical studies of telmisartan and enalapril

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (ATII)-receptor antagonists suppress the effects of ATII and are effective antihypertensive agents. However, the use of ACE inhibitors is sometimes associated with intolerable side effects (eg, cough, angioedema), and patients may develop a compensatory rise in ATII levels. ATII-receptor antagonists have tolerability profiles similar to that of placebo and inhibit the effects of ATII more completely by blocking the AT1 receptor.

OBJECTIVE

This review summarizes clinical studies comparing the efficacy and tolerability of the ATII-receptor antagonist telmisartan with the ACE inhibitor enalapril in patients with hypertension.

METHODS

Randomized, controlled clinical trials comparing telmisartan with enalapril in patients with primary hypertension were identified through a PubMed search of the English-language literature from 1998 through 2001 and from bibliographic data provided by the manufacturer of telmisartan.

RESULTS

In 2 randomized, double-blind, placebo-controlled trials (total number of patients, 647), telmisartan 40 or 80 mg/d was at least as effective as enalapril 20 mg/d for lowering blood pressure (BP) in patients with mild to moderate hypertension. An open-label, titration-to-response study involving 86 patients with severe hypertension found that telmisartan 80 to 160 mg/d was as efficacious as enalapril 20 to 40 mg/d. The antihypertensive effects of telmisartan 20 to 80 mg/d and enalapril 5 to 20 mg/d were comparable in 278 elderly patients (age > or = 65 years) with mild to moderate hypertension enrolled in a 26-week, double-blind, dose-titration study. A double-blind, titration-to-response study in 71 patients with moderate renal impairment and mild to moderate hypertension found equivalent reductions in BP with telmisartan 40 to 80 mg/d and enalapril 10 to 20 mg/d without any clinically relevant decline in renal function. Telmisartan tended to be better tolerated than enalapril in this study, with fewer patients experiencing treatment-related adverse events (8.9% vs 26.9%, respectively).

CONCLUSIONS

Based on the literature included in this review, telmisartan and enalapril produced comparable reductions in BP in a broad range of patients with hypertension. Telmisartan appeared to have a better tolerability profile.