Renin inhibitors: novel agents for renoprotection or a better angiotensin receptor blocker for blood pressure lowering?

Therapeutic Implications of Renin-Angiotensin System Modulators in Alzheimer's Dementia

The Renin-Angiotensin System (RAS) has attracted considerable interest beyond its traditional cardiovascular role due to emerging data indicating its potential involvement in neurodegenerative diseases, including Alzheimer's dementia (AD). This review investigates the therapeutic implications of RAS modulators, specifically focusing on angiotensin-converting enzyme inhibitors (ACEIs), angiotensin receptor blockers (ARBs), and renin inhibitors in AD. ACEIs, commonly used for hypertension, show promise in AD by reducing angiotensin (Ang) II levels. This reduction is significant as Ang II contributes to neuroinflammation, oxidative stress, and β-amyloid (Aβ) accumulation, all implicated in AD pathogenesis. ARBs, known for vasodilation, exhibit neuroprotection by blocking Ang II receptors, improving cerebral blood flow and cognitive decline in AD models. Renin inhibitors offer a novel approach by targeting the initial RAS step, displaying anti-inflammatory and antioxidant effects that mitigate AD degeneration. Preclinical studies demonstrate RAS regulation's favorable impact on neuroinflammation, neuronal damage, cognitive function, and Aβ metabolism. Clinical trials on RAS modulators in AD are limited, but with promising results, ARBs being more effective that ACEIs in reducing cognitive decline. The varied roles of ACEIs, ARBs, and renin inhibitors in RAS modulation present a promising avenue for AD therapeutic intervention, requiring further research to potentially transform AD treatment strategies.

Renin inhibition in the treatment of diabetic kidney disease

Inhibition of the RAAS (renin–angiotensin–aldosterone system) plays a pivotal role in the prevention and treatment of diabetic nephropathy and a spectrum of other proteinuric kidney diseases. Despite documented beneficial effects of RAAS inhibitors in diabetic patients with nephropathy, reversal of the progressive course of this disorder or at least long-term stabilization of renal function are often difficult to achieve, and many patients still progress to end-stage renal disease. Incomplete inhibition of the RAAS has been postulated as one of reasons for unsatisfactory therapeutic responses to RAAS inhibition in some patients. Inhibition of renin, a rate-limiting step in the RAAS activation cascade, could overcome at least some of the abovementioned problems associated with the treatment with traditional RAAS inhibitors. The present review focuses on experimental and clinical studies evaluating the two principal approaches to renin inhibition, namely direct renin inhibition with aliskiren and inhibition of the (pro)renin receptor. Moreover, the possibilities of renin inhibition and nephroprotection by interventions primarily aiming at non-RAAS targets, such as vitamin D, urocortins or inhibition of the succinate receptor GPR91 and cyclo-oxygenase-2, are also discussed.

Exemplification of the challenges associated with utilising fluorescence intensity based assays in discovery

IMPORTANCE OF THE FIELD

Despite the advances in the understanding of biological processes, significant challenges still face those engaged in small molecule drug discovery. To complicate matters further, researchers are often overwhelmed with a range of off-the-shelf as well as bespoke assay formats to choose from when initiating a drug discovery programme. Although fluorescence intensity based assays have traditionally been adopted in drug discovery programmes for a wide range of target classes, it is essential to fully validate the chosen readouts to confirm that they accurately reflect the underlying biological mechanism under investigation.

AREAS COVERED IN THIS REVIEW

This review exemplifies the challenges that are often encountered with fluorescence intensity based assays and particular attention is paid to compound interference, the protease, deacetylating enzyme and kinase enzyme target classes.

WHAT THE READER WILL GAIN

Designing a critical path in early stage drug discovery, which combines several diverse and minimally overlapping readout modes, will maximise the chance that compound activities will translate between the primary assay (utilised in the initial screening campaign) and secondary assay (utilised to evaluate the confirmed hits identified in the primary assay, usually a cell based assay) formats in a meaningful way. However, this is not always the case as is amply demonstrated across both academia and the pharmaceutical industry. Paying insufficient attention to these points can lead to the early termination of drug discovery programmes, not for want of resources or confidence in the rationale underlying the target, but instead because decision making has been driven by assay data originating from a different biological mechanism than the one under investigation.

TAKE HOME MESSAGE

Although fluorescence intensity based assays are likely to remain popular for many target classes in drug discovery, in particular in small molecule screening campaigns, it is essential that at the outset they are sufficiently well validated so that compounds are likely to exhibit profiles that are confirmed in subsequent assays.

Aliskiren-based stepped-care treatment algorithm provides effective blood pressure control

AIMS

Recent guidelines for the management of hypertension recommend an individualised stepped-care treatment approach in mild-to-moderate hypertensive patients, to achieve blood pressure (BP) goals. This study evaluated the probability of patients achieving BP targets with an aliskiren-based stepped-care treatment regimen.

METHODS

This was a 24-week, open-label, non-comparator study design that included six sequential 4-week treatment periods in patients with mild-to-moderate hypertension. Over the potential 24 weeks of active treatment, incremental therapy included the following add-on therapies at 4-week intervals: aliskiren 150-300 mg once daily, hydrochlorothiazide (HCTZ) 12.5-25 mg once daily, and finally amlodipine 5-10 mg once daily, as needed to achieve target BP. Subjects achieving BP targets following any given 4 weeks of therapy were considered study completers, while subjects not achieving their clinical BP target entered into the next step of incremental therapy. The primary efficacy end-point was the estimated cumulative probability of patients achieving BP target.

RESULTS

Of 256 patients treated, 232 (90.6%) completed the study. Baseline mean sitting BP was 155.7/91.7 mmHg. At study end-point, the estimated cumulative probability of reaching BP target was 86.12%. The stepped-care treatment regimen was well tolerated at the maximal recommended doses of all the individual complimentary therapies.

CONCLUSION

An aliskiren-based stepped-care treatment regimen that subsequently included both HCTZ and amlodipine is effective in achieving BP goals in approximately 90% of patients with mild-to-moderate hypertension.

What is the role of renin inhibition in the treatment of diabetic kidney disease?

Inhibition of the renin-angiotensin-aldosterone system (RAAS) plays a pivotal role in preventing and treating diabetic nephropathy. However, despite documented beneficial effects of RAAS inhibitors in diabetic patients with nephropathy, reversal of the progressive course of this disorder or at least long-term stabilization of renal function are often difficult to achieve, and many patients still progress to end-stage renal disease. Incomplete inhibition of the RAAS has been postulated as one of the reasons for unsatisfactory therapeutic responses to RAAS inhibition in some patients. Inhibition of renin, a rate-limiting step in the RAAS activation cascade, is the logical approach to overcome at least some of the above-mentioned problems associated with the treatment with traditional RAAS inhibitors. This article focuses on experimental and clinical studies evaluating the two principal approaches to renin inhibition: direct renin inhibition with competitive inhibitors (eg, aliskiren) and inhibition of the (pro)renin receptor.