Firibastat: An Oral First-in-Class Brain Aminopeptidase A Inhibitor for Systemic Hypertension

Bioinformatic characterization of ENPEP, the gene encoding a potential cofactor for SARS-CoV-2 infection

Research on SARS-CoV-2, the viral pathogen that causes COVID-19, has identified angiotensin converting enzyme 2 (ACE2) as the primary viral receptor. Several genes that encode viral cofactors, such as TMPRSS2, NRP1, CTSL, and possibly KIM1, have since been discovered. Glutamyl aminopeptidase (APA), encoded by the gene ENPEP, is another cofactor candidate due to similarities in its biological role and high correlation with ACE2 and other human coronavirus receptors, such as aminopeptidase N (APN) and dipeptidyl peptidase 4 (DPP4). Recent studies have proposed a role for ENPEP as a viral receptor in humans, and ENPEP and ACE2 are both closely involved in the renin-angiotensin-aldosterone system proposed to play an important role in SARS-CoV-2 pathophysiology. We performed bioinformatic analyses using publicly available bulk (>17,000 samples from 49 distinct tissues) and single-cell (>2.5 million cells) RNA-Seq gene expression datasets to evaluate the expression and function of the ENPEP gene. We also investigated age- and sex-related changes in ENPEP expression. Overall, expression of ENPEP was highest in the small intestine enterocyte brush border and the kidney cortex. ENPEP is widely expressed in a subset of vascular smooth muscle cells (likely pericytes) in systemic vasculature, the heart, and the brain. ENPEP is expressed at low levels in the lower respiratory epithelium. In the lung, ENPEP is most highly expressed in para-alveolar fibroblasts. Single-cell data revealed ENPEP expression in a substantial fraction of ependymal cells, a finding not reported before in humans. Age increases ENPEP expression in skeletal muscle and the prostate, while decreasing it in the heart and aorta. Angiogenesis was found to be a central biological function associated with the ENPEP gene. Tissue-specific roles, such as protein digestion and fat metabolism, were also identified in the intestine. In the liver, the gene is linked to the complement system, a connection that has not yet been thoroughly investigated. Expression of ENPEP and ACE2 is strongly correlated in the small intestine and renal cortex. Both overall and in blood vessels, ENPEP and ACE2 have a stronger correlation than many other genes associated with SARS-CoV-2, such as TMPRSS2, CTSL, and NRP1. Possible interaction between glutamyl aminopeptidase and SARS-CoV-2 should be investigated experimentally.

Aminopeptidase A: A Novel Therapeutic Target for Hypertension Management

The renin-angiotensin system (RAS) is crucial for regulating and understanding the pathophysiology of hypertension. However, there has been little focus on the breakdown of the active peptide, angiotensin II (AngII). Given that animals lacking aminopeptidase A (APA) exhibit hypertension, it may be concluded that APA is a crucial enzyme in regulating blood pressure by breaking down AngII. It has been also seen that the elevated blood pressure in the spontaneously hypertensive rat (SHR) is caused by the activation of the RAS and a concurrent reduction in renal angiotensin-converting enzyme (ACE) activity. The activity of APA is elevated at the beginning of pre-eclampsia and decreases below the levels seen during a normal pregnancy as pre-eclampsia progresses (particularly, in severe cases). The activity of Serum APA is also heightened after hormone replacement treatment (HRT), perhaps as a response to increasing levels of AngII. Therefore, it is crucial to examine the connection between the activation of the RAS, the levels of AngII in the bloodstream, and the presence of APA in hypertension conditions.

Metabolic resistance of Aβ3pE-42, a target epitope of the anti-Alzheimer therapeutic antibody, donanemab

The amyloid β peptide (Aβ), starting with pyroglutamate (pE) at position 3 and ending at position 42 (Aβ3pE-42), predominantly accumulates in the brains of Alzheimer's disease. Consistently, donanemab, a therapeutic antibody raised against Aβ3pE-42, has been shown to be effective in recent clinical trials. Although the primary Aβ produced physiologically is Aβ1-40/42, an explanation for how and why this physiological Aβ is converted to the pathological form remains elusive. Here, we present experimental evidence that accounts for the aging-associated Aβ3pE-42 deposition: Aβ3pE-42 was metabolically more stable than other Aβx-42 variants; deficiency of neprilysin, the major Aβ-degrading enzyme, induced a relatively selective deposition of Aβ3pE-42 in both APP transgenic and App knock-in mouse brains; Aβ3pE-42 deposition always colocalized with Pittsburgh compound B-positive cored plaques in APP transgenic mouse brains; and under aberrant conditions, such as a significant reduction in neprilysin activity, aminopeptidases, dipeptidyl peptidases, and glutaminyl-peptide cyclotransferase-like were up-regulated in the progression of aging, and a proportion of Aβ1-42 may be processed to Aβ3pE-42. Our findings suggest that anti-Aβ therapies are more effective if given before Aβ3pE-42 deposition.

[New therapeutic targets in hypertension]

Even though a large number of antihypertensive drugs are suitable for hypertension treatment, some new therapeutic targets are recently under development. Most are focused in the treatment of resistant hypertension, added to the drugs currently available for treating such condition. Others have specific particularities in their duration of action, which allows their use once per month or every six months and could become alternatives to the current antihypertensive treatment. Most interesting therapeutic targets are the renin-angiotensin-aldosterone system, through interference with the RNA of the angiotensinogen, the inhibition of brain aminopeptidase III, the inhibition of aldosterone synthase, and new non-steroidal aldosterone receptor antagonists. In addition, dual endothelin receptor antagonists or agonists of the NPR1 receptor, the main effector of natriuretic peptides are other new interesting therapeutic possibilities. In this paper, we review clinical data on the development of the most interesting molecules acting through these new therapeutic targets.

Firibastat: a Novel Treatment for Hypertension

PURPOSE OF REVIEW

The purpose of this review is to discuss the unique mechanism of firibastat, a new antihypertension medication. Hypertension continues to be a highly prevalent public health issue.

RECENT FINDINGS

Firibastat is a novel agent developed to treat hypertension. As the first member in the class of centrally acting agents to target the brain renin angiotensin system, firibastat offers new pathways to consider and enhances the regimen of agents currently available to treat hypertension. Recent clinical trials have demonstrated effectiveness and safety in mild hypertension as well as resistant hypertension. This review introduces firibastat as a new therapeutic class of treatment for hypertension focused on the renin angiotensin system in the brain. Early studies have shown a significant reduction in blood pressure with minimal side effects particularly in patients who are difficult to treat.