A phase 2 trial investigating the effects of the angiotensin II type 2 receptor agonist C21 in systemic sclerosis-related Raynaud's

Microvascular angiotensin II type 2 receptor function is enhanced in young females and declines in a model of murine aging

Introduction

Angiotensin II (AngII) affects cardiovascular health, mediating impacts through AngII type 1 (AT1R) and type 2 (AT2R) receptors. The present study investigated sex and aging-related differences in microvascular AngII receptor function in mice and humans.

Methods

Mesenteric resistance arteries (MRA) were isolated from 3-, 12-, and 18-month-old female and male C57/Bl6 mice. Wire myography was used to measure vasoconstriction to AngII and vasodilation to an AT2R agonist (compound 21, C21). Seven healthy adults (3 premenopausal women and 4 age-matched men) were recruited to participate in a study measuring cutaneous microvascular vasoconstriction to AngII in the presence and absence of 10 μM PD123319, an AT2R antagonist.

Results

In murine MRA, AngII-induced constriction increases by 18 months in females and by 12 months in males. AT2R-mediated vasodilation was reduced with age in females only, which corresponds with a female-specific decrease in mesenteric AT2R mRNA expression. AT2R inhibition enhances AngII-induced constriction in young female, but not male, mice. Clinical data support that premenopausal women have attenuated AngII constriction vs. men, which is abrogated by AT2R inhibition. AT2R expression is greater in primary aortic smooth muscle cells, but not endothelial cells, from young women compared with men.

Conclusions

These data demonstrate enhanced microvascular AT2R function in young female mice and young women. There is a female-specific loss of AT2R function with age in mice, concomitant with declining AT2R expression. These findings implicate AT2R as a sex-specific target for microvascular dysfunction and aging-associated cardiovascular disease.

Assessment of digital perfusion as a surrogate outcome in Raynaud's phenomenon clinical trials

OBJECTIVES

Measurement of digital perfusion, sometimes coupled with a cold challenge, has been widely used as an objective outcome in trials evaluating drug therapies in RP, in addition to patient-reported outcomes or to establish the proof-of-concept in preliminary studies. However, whether digital perfusion is a valid surrogate for clinical outcomes in RP trials has never been explored. The principal aim of this study was to evaluate the potential surrogacy of digital perfusion, by combining individual-level and trial-level data.

METHODS

We used individual data from a series of n-of-1 trials, and trial data from a network meta-analysis. We estimated individual-level surrogacy through coefficients of determination between digital perfusion and clinical outcomes (R2ind). We further calculated the coefficients of determination between treatment effect on the clinical outcomes and on digital perfusion, at the individual level (R2TEind) and at the trial level (R2trial), using non-weighted linear regression, with their 95% CI calculated through bootstrapping.

RESULTS

Results from 33 patients and 24 trials were included in the final analysis. At the individual level, there was no correlation between digital perfusion and clinical outcomes at rest and in response to various cooling tests (the highest R2ind was 0.03 [-0.07, 0.09]), and R2TEind was also very low 0.07 (0, 0.29). At the trial level, the highest value of R2trial was 0.1 (0, 0.477).

CONCLUSIONS

Digital perfusion, at rest or in response to a cold challenge, and whatever the method used, does not fulfil the criteria of a valid surrogate for existing patient-reported outcomes in RP trials.

[Update on targeted biopharmaceuticals in systemic sclerosis!]

Systemic sclerosis (SSc) is a rare connective tissue disease characterized by inflammation, fibrosis, and autoimmunity. Despite few clinical trials when compared to other autoimmune diseases, SSc has benefited from renewed interest over the past ten years and a large number of clinical trials have been performed or are underway. We present here the results of the trials published in the last 5 years in ScS according to the chosen endpoint criteria and describe the trials in progress or expected in the years to come.

Utilizing venous occlusion plethysmography to assess vascular effects: A study with buloxibutid, an angiotensin II type 2 receptor agonist

Buloxibutid (also known as C21) is a potent and selective angiotensin II type 2 receptor (AT2R) agonist, in development for oral treatment of fibrotic lung disease. This phase I, open-label, pharmacodynamic study investigated vascular effects of buloxibutid in five healthy male volunteers. Subjects were administered intra-arterial infusions of buloxibutid for 5 min in ascending doses of 3, 10, 30, 100, and 200 μg/min, infused sequentially in the forearm. Infusions of sodium nitroprusside (SNP) solution in doses of 0.8-3.2 μg/min were administered as a positive control. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Safety and tolerability of intra-arterial administrations of buloxibutid were evaluated. Following infusion of buloxibutid in doses of 3-200 μg/min, the range of increase in FBF was 27.8%, 17.2%, 37.0%, 28.5%, and 60.5%, compared to the respective baseline. The largest increase was observed in the highest dose group. Infusions of SNP as a positive control, increased FBF 230-320% compared to baseline. Three adverse events (AEs) of mild intensity, not related to buloxibutid or SNP, were reported for two subjects. Two of these AEs were related to study procedures. There were no clinically relevant changes in arterial blood pressure during the study period. Intra-arterial infusion of buloxibutid in low, ascending doses increased FBF, indicating that buloxibutid may be effective in conditions associated with endothelial dysfunction. Venous occlusion plethysmography was found to be a useful method to explore pharmacodynamic vascular effects of novel AT2R agonists, while avoiding systemic adverse effects.

Catch your breath: The protective role of the angiotensin AT2 receptor for the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease whereby excessive deposition of extracellular matrix proteins (ECM) ultimately leads to respiratory failure. While there have been advances in pharmacotherapies for pulmonary fibrosis, IPF remains an incurable and irreversible disease. There remains an unmet clinical need for treatments that reverse fibrosis, or at the very least have a more tolerable side effect profile than currently available treatments. Transforming growth factor β1(TGFβ1) is considered the main driver of fibrosis in IPF. However, as our understanding of the role of the pulmonary renin-angiotensin system (PRAS) in the pathogenesis of IPF increases, it is becoming clear that targeting angiotensin receptors represents a potential novel treatment strategy for IPF - in particular, via activation of the anti-fibrotic angiotensin type 2 receptor (AT2R). This review describes the current understanding of the pathophysiology of IPF and the mediators implicated in its pathogenesis; focusing on TGFβ1, angiotensin II and related peptides in the PRAS and their contribution to fibrotic processes in the lung. Preclinical and clinical assessment of currently available AT2R agonists and the development of novel, highly selective ligands for this receptor will also be described, with a focus on compound 21, currently in clinical trials for IPF. Collectively, this review provides evidence of the potential of AT2R as a novel therapeutic target for IPF.

Investigational drugs for the treatment of scleroderma: what's new?

INTRODUCTION

Systemic sclerosis (SSc) is an orphan, chronic, autoimmune, fibrotic disease with unknown etiology characterized by progressive fibrosis of the skin and internal organs. SSc has the highest mortality, the deadliest among the connective tissue diseases, despite the introduction of new treatment options in the past decades.

AREAS COVERED

The aim of the current systematic review was to investigate new targeted therapy and their impact on disease progression, mainly focusing on phase I and II clinical trials within the past three years.

EXPERT OPINION

Despite recent groundbreaking advancements in understanding SSc pathophysiology, early diagnosis and early introduction of effective targeted treatments within the optimal window of opportunity to prevent irreversible disease damage still represents a significant clinical challenge. Ongoing significant research for new molecular and epigenetics pathways is of fundamental importance to offer new perspectives on disease phenotype and for the development of personalized treatment strategies.