Recombinant human relaxin in the treatment of scleroderma. A randomized, double-blind, placebo-controlled trial

The role of macrophages in asthma-related fibrosis and remodelling

Airway remodelling significantly contributes to the progressive loss of lung function and heightened symptom severity in chronic asthma. Additionally, it often persists and demonstrates reduced responsiveness to the mainstay treatments. The excessive deposition of collagen and extracellular matrix proteins leads to subepithelial fibrosis and airway remodelling, resulting in increased stiffness and decreased elasticity in the airway. Studies have emphasized the crucial role of subepithelial fibrosis in the pathogenesis of asthma. Fibrotic processes eventually cause airway narrowing, reduced lung function, and exacerbation of asthma symptoms. Macrophages play a crucial role in this process by producing pro-fibrotic cytokines, growth factors, and enzymes such as matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Additionally, identification of novel genetic markers has provided evidence for a strong genetic component in fibrosis within macrophage regulated fibrosis. Although macrophages contribute to the progression of airway remodelling and subepithelial fibrosis, interventions targeting macrophage-driven fibrotic changes have not yet been developed. This review synthesizes research on the intricate pathways through which macrophages contribute to subepithelial fibrosis in chronic asthma and its' pathological features. Understanding the interplay between macrophages, fibrosis, and asthma pathogenesis is essential for developing effective therapeutic strategies to manage severe asthma and improve patient outcomes.

Optimization of Single Relaxin B-Chain Peptide Leads to the Identification of R2R01, a Potent, Long-Acting RXFP1 Agonist for Cardiovascular and Renal Diseases

Peptide 1, a C18 fatty acid-modified single-chain relaxin analogue, was recently identified as a potent, selective, and long-lasting relaxin family peptide receptor 1 (RXFP1) agonist. Further advanced pharmacokinetic profiling of this compound highlighted elevated levels of oxidative metabolism occurring in dogs and mini pigs but only marginally in rats. This study aimed to design long-lasting relaxin analogues with increased stability against metabolic oxidation while securing subnanomolar RXFP1 potency. Key structural elements, including fatty acid chain length, attachment position, and linker structure, were modified to reduce oxidative metabolism and improve pharmacokinetic parameters. Additionally, incorporating α-methyl lysine (Mly) at position 30, alongside other selective sequence mutations, resulted in several analogues with subnanomolar RXFP1 potency and improved duration of action compared to 1. Compound 21 (R2R01) was then selected as a candidate for an in-depth characterization. It is currently undergoing phase 2 clinical development for renal and cardiovascular diseases.

The renoprotective efficacy and safety of genetically-engineered human bone marrow-derived mesenchymal stromal cells expressing anti-fibrotic cargo

BACKGROUND

Kidney fibrosis is a hallmark of chronic kidney disease (CKD) and compromises the viability of transplanted human bone marrow-derived mesenchymal stromal cells (BM-MSCs). Hence, BM-MSCs were genetically-engineered to express the anti-fibrotic and renoprotective hormone, human relaxin-2 (RLX) and green fluorescent protein (BM-MSCs-eRLX + GFP), which enabled BM-MSCs-eRLX + GFP delivery via a single intravenous injection.

METHODS

BM-MSCs were lentiviral-transduced with human relaxin-2 cDNA and GFP, under a eukaryotic translation elongation factor-1α promoter (BM-MSCs-eRLX + GFP) or GFP alone (BM-MSCs-eGFP). The ability of BM-MSCs-eRLX + GFP to differentiate, proliferate, migrate, produce RLX and cytokines was evaluated in vitro, whilst BM-MSC-eRLX + GFP vs BM-MSCs-eGFP homing to the injured kidney and renoprotective effects were evaluated in preclinical models of ischemia reperfusion injury (IRI) and high salt (HS)-induced hypertensive CKD in vivo. The long-term safety of BM-MSCs-RLX + GFP was also determined 9-months after treatment cessation in vivo.

RESULTS

When cultured for 3- or 7-days in vitro, 1 × 106 BM-MSCs-eRLX + GFP produced therapeutic RLX levels, and secreted an enhanced but finely-tuned cytokine profile without compromising their proliferation or differentiation capacity compared to naïve BM-MSCs. BM-MSCs-eRLX + GFP were identified in the kidney 2-weeks post-administration and retained the therapeutic effects of RLX in vivo. 1-2 × 106 BM-MSCs-eRLX + GFP attenuated the IRI- or therapeutically abrogated the HS-induced tubular epithelial damage and interstitial fibrosis, and significantly reduced the HS-induced hypertension, glomerulosclerosis and proteinuria. This was to an equivalent extent as RLX and BM-MSCs administered separately but to a broader extent than BM-MSCs-eGFP or the angiotensin-converting enzyme inhibitor, perindopril. Additionally, these renoprotective effects of BM-MSCs-eRLX + GFP were maintained in the presence of perindopril co-treatment, highlighting their suitability as adjunct therapies to ACE inhibition. Importantly, no major long-term adverse effects of BM-MSCs-eRLX + GFP were observed.

CONCLUSIONS

BM-MSCs-eRLX + GFP produced greater renoprotective and therapeutic efficacy over that of BM-MSCs-eGFP or ACE inhibition, and may represent a novel and safe treatment option for acute kidney injury and hypertensive CKD.

Relaxin as a treatment for musculoskeletal fibrosis: What we know and future directions

Fibrotic changes in musculoskeletal diseases arise from the abnormal buildup of fibrotic tissue around the joints, leading to limited mobility, compromised joint function, and diminished quality of life. Relaxin (RLX) attenuates fibrosis by accelerating collagen degradation and inhibiting excessive extracellular matrix (ECM) production. Further, RLX disrupts myofibroblast activation by modulating the TGF-β/Smads signaling pathways, which reduces connective tissue fibrosis. However, the mechanisms and effects of RLX in musculoskeletal pathologies are emerging as increasing research focuses on relaxin's impact on skin, ligaments, tendons, cartilage, joint capsules, connective tissues, and muscles. This review delineates the actions of relaxin within the musculoskeletal system and the challenges to its clinical application. Relaxin shows significant potential in both in vivo and in vitro studies for broadly managing musculoskeletal fibrosis; however, challenges such as short biological half-life and sex-specific responses may pose hurdles for clinical use.

R2R01: A long-acting single-chain peptide agonist of RXFP1 for renal and cardiovascular diseases

BACKGROUND

The therapeutic potential of relaxin for heart failure and renal disease in clinical trials is hampered by the short half-life of serelaxin. Optimization of fatty acid-acetylated single-chain peptide analogues of relaxin culminated in the design and synthesis of R2R01, a potent and selective RXFP1 agonist with subcutaneous bioavailability and extended half-life.

EXPERIMENTAL APPROACH

Cellular assays and pharmacological models of RXFP1 activation were used to validate the potency and selectivity of R2R01. Increased renal blood flow was used as a translational marker of R2R01 activity. Human mastocytes (LAD2 cells) were used to study potential pseudo-allergic reactions and CD4+ T-cells to study immunogenicity. The pharmacokinetics of R2R01 were characterized in rats and minipigs.

KEY RESULTS

In vitro, R2R01 had comparable potency and efficacy to relaxin as an agonist for human RXFP1. In vivo, subcutaneous administration of R2R01 increased heart rate and renal blood flow in normotensive and hypertensive rat and did not show evidence of tachyphylaxis. R2R01 also increased nipple length in rats, used as a chronic model of RXFP1 engagement. Pharmacokinetic studies showed that R2R01 has a significantly extended terminal half-life. The in vitro assays with LAD2 cells and CD4+ T-cells showed that R2R01 had low potential for pseudo-allergic and immunogenic reactions, respectively.

CONCLUSION AND IMPLICATIONS

R2R01 is a potent RXFP1 agonist with an extended half-life that increases renal blood flow in various settings including normotensive and hypertensive conditions. The preclinical efficacy and safety data supported clinical development of R2R01 as a potential new therapy for renal and cardiovascular diseases.

Human recombinant relaxin-2 (serelaxin) regulates the proteome, lipidome, lipid metabolism and inflammatory profile of rat visceral adipose tissue

Recombinant human relaxin-2 (serelaxin) has been widely proven as a novel drug with myriad effects at different cardiovascular levels, which support its potential therapeutic efficacy in several cardiovascular diseases (CVD). Considering these effects, together with the influence of relaxin-2 on adipocyte physiology and adipokine secretion, and the connection between visceral adipose tissue (VAT) dysfunction and the development of CVD, we could hypothesize that relaxin-2 may regulate VAT metabolism. Our objective was to evaluate the impact of a 2-week serelaxin treatment on the proteome and lipidome of VAT from Sprague-Dawley rats. We found that serelaxin increased 1 polyunsaturated fatty acid and 6 lysophosphatidylcholines and decreased 4 triglycerides in VAT employing ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) based platforms, and that regulates 47 phosphoproteins using SWATH/MS analysis. Through RT-PCR, we found that serelaxin treatment also caused an effect on VAT lipolysis through an increase in the mRNA expression of hormone-sensitive lipase (HSL) and a decrease in the expression of adipose triglyceride lipase (ATGL), together with a reduction in the VAT expression of the fatty acid transporter cluster of differentiation 36 (Cd36). Serelaxin also caused an anti-inflammatory effect in VAT by the decrease in the mRNA expression of tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), chemerin, and its receptor. In conclusion, our results highlight the regulatory role of serelaxin in the VAT proteome and lipidome, lipolytic function, and inflammatory profile, suggesting the implication of several mechanisms supporting the potential benefit of serelaxin for the prevention of obesity and metabolic disorders.

Role of rituximab in the treatment of systemic sclerosis: A literature review

This literature review aimed to evaluate the effectiveness of rituximab (RTX) in patients with systemic sclerosis (SSc). PubMed was searched for articles, published through 31 March 2022, on any controlled studies using RTX in the treatment of SSc. Of 85 identified articles, 9 were selected by title/abstract screening and full text examination. All nine articles reported outcomes of forced vital capacity (%FVC), and seven reported those of modified Rodnan skin scores (mRSS). The results showed that among the seven controlled studies evaluating skin lesions in patients with SSc, four showed a significant improvement of mRSS by RTX when compared with a control group, whereas three showed no significant effect. Among the nine controlled studies evaluating lung lesions, five showed a significant improvement of %FVC compared with a control group, whereas four showed no significant effect. In conclusion, RTX may be effective in the treatment of skin and lung lesions in patients with SSc. The profiles of SSc patients for whom RTX was indicated were unclear, although patients with diffuse cutaneous SSc and those positive for anti-topoisomerase I antibody were considered potential targets. Additional studies are needed to assess the long-term effectiveness of RTX in the treatment of patients with SSc.

Injured Endothelial Cell: A Risk Factor for Pulmonary Fibrosis

The pathological features of pulmonary fibrosis (PF) are the abnormal activation and proliferation of myofibroblasts and the extraordinary deposition of the extracellular matrix (ECM). However, the pathogenesis of PF is still indistinct. In recent years, many researchers have realized that endothelial cells had a crucial role in the development of PF. Studies have demonstrated that about 16% of the fibroblasts in the lung tissue of fibrotic mice were derived from endothelial cells. Endothelial cells transdifferentiated into mesenchymal cells via the endothelial-mesenchymal transition (E(nd)MT), leading to the excessive proliferation of endothelial-derived mesenchymal cells and the accumulation of fibroblasts and ECM. This suggested that endothelial cells, a significant component of the vascular barrier, played an essential role in PF. Herein, this review discusses E(nd)MT and its contribution to the activation of other cells in PF, which could provide new ideas for further understanding the source and activation mechanism of fibroblasts and the pathogenesis of PF.

Relaxin in fibrotic ligament diseases: Its regulatory role and mechanism

Fibrotic ligament diseases (FLDs) are diseases caused by the pathological accumulation of periarticular fibrotic tissue, leading to functional disability around joint and poor life quality. Relaxin (RLX) has been reported to be involved in the development of fibrotic lung and liver diseases. Previous studies have shown that RLX can block pro-fibrotic process by reducing the excess extracellular matrix (ECM) formation and accelerating collagen degradation in vitro and in vivo. Recent studies have shown that RLX can attenuate connective tissue fibrosis by suppressing TGF-β/Smads signaling pathways to inhibit the activation of myofibroblasts. However, the specific roles and mechanisms of RLX in FLDs remain unclear. Therefore, in this review, we confirmed the protective effect of RLX in FLDs and summarized its mechanism including cells, key cytokines and signaling pathways involved. In this article, we outline the potential therapeutic role of RLX and look forward to the application of RLX in the clinical translation of FLDs.

Minimally invasive, sustained-release relaxin-2 microparticles reverse arthrofibrosis

Substantial advances in biotherapeutics are distinctly lacking for musculoskeletal diseases. Musculoskeletal diseases are biomechanically complex and localized, highlighting the need for novel therapies capable of addressing these issues. All frontline treatment options for arthrofibrosis, a debilitating musculoskeletal disease, fail to treat the disease etiology-the accumulation of fibrotic tissue within the joint space. For millions of patients each year, the lack of modern and effective treatment options necessitates surgery in an attempt to regain joint range of motion (ROM) and escape prolonged pain. Human relaxin-2 (RLX), an endogenous peptide hormone with antifibrotic and antifibrogenic activity, is a promising biotherapeutic candidate for musculoskeletal fibrosis. However, RLX has previously faltered through multiple clinical programs because of pharmacokinetic barriers. Here, we describe the design and in vitro characterization of a tailored drug delivery system for the sustained release of RLX. Drug-loaded, polymeric microparticles released RLX over a multiweek time frame without altering peptide structure or bioactivity. In vivo, intraarticular administration of microparticles in rats resulted in prolonged, localized concentrations of RLX with reduced systemic drug exposure. Furthermore, a single injection of RLX-loaded microparticles restored joint ROM and architecture in an atraumatic rat model of arthrofibrosis with clinically derived end points. Finally, confirmation of RLX receptor expression, RXFP1, in multiple human tissues relevant to arthrofibrosis suggests the clinical translational potential of RLX when administered in a sustained and targeted manner.

Relaxin-2 as a Potential Biomarker in Cardiovascular Diseases

The pleiotropic hormone relaxin-2 plays a pivotal role in the physiology and pathology of the cardiovascular system. Relaxin-2 exerts relevant regulatory functions in cardiovascular tissues through the specific receptor relaxin family peptide receptor 1 (RXFP1) in the regulation of cardiac metabolism; the induction of vasodilatation; the reversion of fibrosis and hypertrophy; the reduction of inflammation, oxidative stress, and apoptosis; and the stimulation of angiogenesis, with inotropic and chronotropic effects as well. Recent preclinical and clinical outcomes have encouraged the potential use of relaxin-2 (or its recombinant form, known as serelaxin) as a therapeutic strategy during cardiac injury and/or in patients suffering from different cardiovascular disarrangements, especially heart failure. Furthermore, relaxin-2 has been proposed as a promising biomarker of cardiovascular health and disease. In this review, we emphasize the relevance of the endogenous hormone relaxin-2 as a useful diagnostic biomarker in different backgrounds of cardiovascular pathology, such as heart failure, atrial fibrillation, myocardial infarction, ischemic heart disease, aortic valve disease, hypertension, and atherosclerosis, which could be relevant in daily clinical practice and could contribute to comprehending the specific role of relaxin-2 in cardiovascular diseases.

Relaxin as an anti-fibrotic treatment: Perspectives, challenges and future directions

Fibrosis refers to the scarring and hardening of tissues, which results from a failed immune system-coordinated wound healing response to chronic organ injury and which manifests from the aberrant accumulation of various extracellular matrix components (ECM), primarily collagen. Despite being a hallmark of prolonged tissue damage and related dysfunction, and commonly associated with high morbidity and mortality, there are currently no effective cures for its regression. An emerging therapy that meets several criteria of an effective anti-fibrotic treatment, is the recombinant drug-based form of the human hormone, relaxin (also referred to as serelaxin, which is bioactive in several other species). This review outlines the broad anti-fibrotic and related organ-protective roles of relaxin, mainly from studies conducted in preclinical models of ageing and fibrotic disease, including its ability to ameliorate several aspects of fibrosis progression and maturation, from immune cell infiltration, pro-inflammatory and pro-fibrotic cytokine secretion, oxidative stress, organ hypertrophy, cell apoptosis, myofibroblast differentiation and ECM production, to its ability to facilitate established ECM degradation. Studies that have compared and/or combined these therapeutic effects of relaxin with current standard of care medication have also been discussed, along with the main challenges that have hindered the translation of the anti-fibrotic efficacy of relaxin to the clinic. The review then outlines the future directions as to where scientists and several pharmaceutical companies that have recognized the therapeutic potential of relaxin are working towards, to progress its development as a treatment for human patients suffering from various fibrotic diseases.

Relaxin has beneficial effects on liver lipidome and metabolic enzymes

Relaxin is an insulin-like hormone with pleiotropic protective effects in several organs, including the liver. We aimed to characterize its role in the control of hepatic metabolism in healthy rats. Sprague-Dawley rats were treated with human recombinant relaxin-2 for 2 weeks. The hepatic metabolic profile was analyzed using UHPLC-MS platforms. Hepatic gene expression of key enzymes of desaturation (Fads1/Fads2) of n-6 and n-3 polyunsaturated fatty acids (PUFAs), of phosphatidylethanolamine (PE) N-methyltransferase (Pemt), of fatty acid translocase Cd36, and of glucose-6-phosphate isomerase (Gpi) were quantified by Real Time-PCR. Activation of 5'AMP-activated protein kinase (AMPK) was analyzed by Western Blot. Relaxin-2 significantly modified the hepatic levels of 19 glycerophospholipids, 2 saturated (SFA) and 1 monounsaturated (MUFA) fatty acids (FA), 3 diglycerides, 1 sphingomyelin, 2 aminoacids, 5 nucleosides, 2 nucleotides, 1 carboxylic acid, 1 redox electron carrier, and 1 vitamin. The most noteworthy changes corresponded to the substantially decreased lysoglycerophospholipids, and to the clearly increased FA (16:1n-7/16:0) and MUFA + PUFA/SFA ratios, suggesting enhanced desaturase activity. Hepatic gene expression of Fads1, Fads2, and Pemt, which mediates lipid balance and liver health, was increased by relaxin-2, while mRNA levels of the main regulator of hepatic FA uptake Cd36, and of the essential glycolysis enzyme Gpi, were decreased. Relaxin-2 augmented the hepatic activation of the hepatoprotector and master regulator of energy homeostasis AMPK. Relaxin-2 treatment also rised FADS1, FADS2, and PEMT gene expression in cultured Hep G2 cells. Our results bring to light the hepatic metabolic features stimulated by relaxin, a promising hepatoprotective molecule.

Human Recombinant Relaxin (Serelaxin) as Anti-fibrotic Agent: Pharmacology, Limitations and Actual Perspectives

Relaxin (recombinant human relaxin-2 hormone; RLX-2; serelaxin) had raised expectations as a new medication for fibrotic diseases. A plethora of in vitro and in vivo studies have offered convincing demonstrations that relaxin promotes remodelling of connective tissue extracellular matrix mediated by inhibition of multiple fibrogenic pathways, especially the downstream signalling of transforming growth factor (TGF)-β1, a major pro-fibrotic cytokine, and the recruitment and activation of myofibroblast, the main fibrosis-generating cells. However, all clinical trials with relaxin in patients with fibrotic diseases gave inconclusive results. In this review, we have summarized the molecular mechanisms of fibrosis, highlighting those which can be effectively targeted by relaxin. Then, we have performed a critical reappraisal of the clinical trials performed to-date with relaxin as anti-fibrotic drug, in order to highlight their key points of strength and weakness and to identify some future opportunities for the therapeutic use of relaxin, or its analogues, in fibrotic diseases and pathologic scarring which, in our opinion, deserve to be investigated.

Clinical Treatment Options in Scleroderma: Recommendations and Comprehensive Review

There are two major clinical subsets of scleroderma: (i) systemic sclerosis (SSc) is a complex systemic autoimmune disorder characterized by inflammation, vasculopathy, and excessive fibrosis of the skin and multiple internal organs and (ii) localized scleroderma (LoS), also known as morphea, is confined to the skin and/or subcutaneous tissues resulting in collagen deposition and subsequent fibrosis. SSc is rare but is associated with significant morbidity and mortality compared with other rheumatic diseases. Fatal outcomes in SSc often originate from organ complications of the disease, such as lung fibrosis, pulmonary artery hypertension (PAH), and scleroderma renal crisis (SRC). Current treatment modalities in SSc have focused on targeting vascular damage, fibrosis, and regulation of inflammation as well as autoimmune responses. Some drugs previously used in an attempt to suppress fibrosis, like D-penicillamine (D-Pen) or colchicine, have been disappointing in clinical practice despite anecdotal evidence of their advantages. Some canonical medications, including glucocorticoids, immunosuppressants, and vasodilators, have had some success in treating various manifestations in SSc patients. Increasing evidence suggests that some biologic agents targeting collagen, cytokines, and cell surface molecules might have promising therapeutic effects in SSc. In recent years, hematopoietic stem cell transplantation (HSCT), mostly autologous, has made great progress as a promising treatment option in severe and refractory SSc. Due to the complexity and heterogeneity of SSc, there are currently no optimal treatments for all aspects of the disease. As for LoS, local skin-targeted therapy is generally used, including topical application of glucocorticoids or other immunomodulatory ointments and ultraviolet (UV) irradiation. In addition, systemic immunosuppressants are also utilized in several forms of LoS. Here, we comprehensively discuss current treatment options for scleroderma, encompassing old, new, and future potential treatment options. In addition, we summarize data from new clinical trials that have the potential to modify the disease process and improve long-term outcomes in SSc.

Efficacy, Safety, and Tolerability of Treatments for Systemic Sclerosis-Related Interstitial Lung Disease: A Systematic Review and Network Meta-Analysis

BACKGROUND

There is a paucity of head-to-head comparisons of the efficacy and harms of pharmacological treatments for systemic sclerosis-related interstitial lung disease (SSc-ILD).

METHODS

We conducted a network meta-analysis (NMA) in order to compare the effects of different treatments with the placebo on change in forced vital capacity (FVC), change in diffusion lung capacity for CO (DLCO), serious adverse events (SAEs), discontinuation for adverse events and mortality in SSc-ILD. Standardized mean difference (SMD) and log odds ratio were estimated using NMA with fixed effects.

RESULTS

Nine randomized clinical trials (926 participants) comparing eight interventions and the placebo for an average follow-up of one year were included. Compared to the placebo, only rituximab significantly reduced FVC decline (SMD (95% CI) = 1.00 (0.39 to 1.61)). Suitable data on FVC outcome for nintedanib were not available for the analysis. No treatments influenced DLCO. Safety and mortality were also not different across treatments and the placebo, although there were few reported events. Cyclophosphamide and pomalidomide were less tolerated than the placebo, mycophenolate, and nintedanib.

CONCLUSION

Only rituximab significantly reduced lung function decline compared to the placebo. However, direct head-to-head comparison studies are required to confirm these findings and to better determine the safety profile of various treatments.

Specificity of the T Cell Response to Protein Biopharmaceuticals

The anti-drug antibody (ADA) response is an undesired humoral response raised against protein biopharmaceuticals (BPs) which can dramatically disturb their therapeutic properties. One particularity of the ADA response resides in the nature of the immunogens, which are usually human(ized) proteins and are therefore expected to be tolerated. CD4 T cells initiate, maintain and regulate the ADA response and are therefore key players of this immune response. Over the last decade, advances have been made in characterizing the T cell responses developed by patients treated with BPs. Epitope specificity and phenotypes of BP-specific T cells have been reported and highlight the effector and regulatory roles of T cells in the ADA response. BP-specific T cell responses are assessed in healthy subjects to anticipate the immunogenicity of BP prior to their testing in clinical trials. Immunogenicity prediction, also called preclinical immunogenicity assessment, aims at identifying immunogenic BPs and immunogenic BP sequences before any BP injection in humans. All of the approaches that have been developed to date rely on the detection of BP-specific T cells in donors who have never been exposed to BPs. The number of BP-specific T cells circulating in the blood of these donors is therefore limited. T cell assays using cells collected from healthy donors might reveal the weak tolerance induced by BPs, whose endogenous form is expressed at a low level. These BPs have a complete human sequence, but the level of their endogenous form appears insufficient to promote the negative selection of autoreactive T cell clones. Multiple T cell epitopes have also been identified in therapeutic antibodies and some other BPs. The pattern of identified T cell epitopes differs across the antibodies, notwithstanding their humanized, human or chimeric nature. However, in all antibodies, the non-germline amino acid sequences mainly found in the CDRs appear to be the main driver of immunogenicity, provided they can be presented by HLA class II molecules. Considering the fact that the BP field is expanding to include new formats and gene and cell therapies, we face new challenges in understanding and mastering the immunogenicity of new biological products.

Recombinant human H2 relaxin (serelaxin) as a cardiovascular drug: aiming at the right target

Serelaxin (recombinant human relaxin-2 hormone; RLX-2) had raised expectations as a new medication for cardiovascular diseases. Evidence from preclinical studies indicated that serelaxin has chronotropic, inotropic, and anti-arrhythmic actions on the myocardium and cardioprotective effects mediated by vasodilation, angiogenesis, and inhibition of inflammation and fibrosis. However, clinical trials with serelaxin in patients with acute heart failure (AHF) gave inconclusive results. A critical reappraisal of the comprehensive cardiovascular actions of serelaxin clearly delineates acute myocardial infarction (AMI) as a feasible therapeutic target. Serelaxin acts at multiple levels on the pathogenic mechanisms of AMI and previous in vivo studies suggest that its administration at reperfusion affords myocardial salvage. Thus, serelaxin could be an effective adjunctive medical therapy to coronary angioplasty.

Serelaxin alleviates cardiac fibrosis through inhibiting endothelial-to-mesenchymal transition via RXFP1

Rationale: Cardiac fibrosis is an integral constituent of every form of chronic heart disease, and persistence of fibrosis reduces tissue compliance and accelerates the progression to heart failure. Relaxin-2 is a human hormone, which has various physiological functions such as mediating renal vasodilation in pregnancy. Its recombinant form Serelaxin has recently been tested in clinical trials as a therapy for acute heart failure but did not meet its primary endpoints. The aim of this study is to examine whether Serelaxin has an anti-fibrotic effect in the heart and therefore could be beneficial in chronic heart failure. Methods: We utilized two different cardiac fibrosis mouse models (ascending aortic constriction (AAC) and Angiotensin II (ATII) administration via osmotic minipumps) to assess the anti-fibrotic potential of Serelaxin. Histological analysis, immunofluorescence staining and molecular analysis were performed to assess the fibrosis level and indicate endothelial cells which are undergoing EndMT. In vitro TGFβ1-induced endothelial-to-mesenchymal transition (EndMT) assays were performed in human coronary artery endothelial cells and mouse cardiac endothelial cells (MCECs) and were examined using molecular methods. Chromatin immunoprecipitation-qPCR assay was utilized to identify the Serelaxin effect on chromatin remodeling in the Rxfp1 promoter region in MCECs. Results: Our results demonstrate a significant and dose-dependent anti-fibrotic effect of Serelaxin in the heart in both models. We further show that Serelaxin mediates this effect, at least in part, through inhibition of EndMT through the endothelial Relaxin family peptide receptor 1 (RXFP1). We further demonstrate that Serelaxin administration is able to increase its own receptor expression (RXFP1) through epigenetic regulation in form of histone modifications by attenuating TGFβ-pSMAD2/3 signaling in endothelial cells. Conclusions: This study is the first to identify that Serelaxin increases the expression of its own receptor RXFP1 and that this mediates the inhibition of EndMT and cardiac fibrosis, suggesting that Serelaxin may have a beneficial effect as anti-fibrotic therapy in chronic heart failure.

The relaxin family peptide receptor 1 (RXFP1): An emerging player in human health and disease

Background

Relaxin/relaxin family peptide receptor 1 (RXFP1) signaling is important for both normal physiology and disease. Strong preclinical evidence supports relaxin as a potent antifibrotic molecule. However, relaxin‐based therapy failed in clinical trial in patients with systemic sclerosis. We and others have discovered that aberrant expression of RXFP1 may contribute to the abnormal relaxin/RXFP1 signaling in different diseases. Reduced RXFP1 expression and alternative splicing transcripts with potential functional consequences have been observed in fibrotic tissues. A relative decrease in RXFP1 expression in fibrotic tissues—specifically lung and skin—may explain a potential insensitivity to relaxin. In addition, receptor dimerization also plays important roles in relaxin/RXFP1 signaling.

Methods

This review describes the tissue specific expression, characteristics of the splicing variants, and homo/heterodimerization of RXFP1 in both normal physiological function and human diseases. We discuss the potential implications of these molecular features for developing therapeutics to restore relaxin/RXFP1 signaling and to harness relaxin's potential antifibrotic effects.

Results

Relaxin/RXFP1 signaling is important in both normal physiology and in human diseases. Reduced expression of RXFP1 in fibrotic lung and skin tissues surrenders both relaxin/RXFP1 signaling and their responsiveness to exogenous relaxin treatments. Alternative splicing and receptor dimerization are also important in regulating relaxin/RXFP1 signaling.

Conclusions

Understanding the molecular mechanisms that drive aberrant expression of RXFP1 in disease and the functional roles of alternative splicing and receptor dimerization will provide insight into therapeutic targets that may restore the relaxin responsiveness of fibrotic tissues.

Comorbidity burden in systemic sclerosis: beyond disease-specific complications

Systemic sclerosis (SSc) is a chronic, systemic disease characterized by fibrosis of the skin and internal organs, vasculopathy, and auto-immune activation. On the top of severe organ involvement such as interstitial lung and myocardial fibrosis, pulmonary hypertension, and renal crisis, individuals diagnosed with SSc may suffer from a number of comorbidities. This is a narrative review according to published recommendations and we searched the online databases MEDLINE and EMBASE using as key words the following terms: systemic sclerosis, scleroderma, myocardial fibrosis in combination with micro- and macro-vascular disease, cardiac involvement, atherosclerosis, cardiovascular disease and coronary arteries, infections, cancer, depression, osteoporosis, and dyslipidemia. Although data are usually inconclusive it appears that comorbidities with significant impact on life expectancy, namely cardiovascular disease, infections, and cancer as well as phycological disorders affecting emotional and mental health are highly prevalent in SSc population. Thereafter, the aim of this review is to summarize the occurrence and the clinical significance of such comorbidities in SSc population and to discuss how rheumatologists can incorporate the management of these conditions in daily clinical practice.

Healthy Donors Exhibit a CD4 T Cell Repertoire Specific to the Immunogenic Human Hormone H2-Relaxin before Injection

H2-relaxin (RLN2) is a two-chain peptide hormone structurally related to insulin with a therapeutic potential in multiple indications. However, multiple injections of human RLN2 induced anti-RLN2 Abs in patients, hampering its clinical development. As T cell activation is required to produce Abs, we wondered whether T cells specific for RLN2 might be already present in the human blood before any injection. We therefore quantified the RLN2-specific T cell repertoire using PBMCs collected from healthy donors. CD4 T cells were stimulated in multiple replicates by weekly rounds of stimulation by dendritic cells loaded with RLN2, and their specificity was assessed by IFN-γ ELISPOT. The number of specific T cell lines was used to estimate the frequency of circulating T cells. In vitro T cell response was demonstrated in 18 of the 23 healthy donors, leading to the generation of 70 independent RLN2-specific T cell lines. The mean frequency of RLN2-specific CD4 T cells was similar to that of T cells specific for known immunogenic therapeutic proteins. Using overlapping peptides, we identified multiple T cell epitopes hosted in the N-terminal parts of the α- and β-chains and common to multiple donors, in agreement with their capacity to bind to multiple HLA-DR molecules. Our results provide important clues to the immunogenicity of RLN2 and highlight the weak central immune tolerance induced against this self-hormone.

Relaxin gene therapy: A promising new treatment option for various diseases with aberrant fibrosis or irregular angiogenesis

Relaxin (RLX) is an insulin-like polypeptide hormone that was initially introduced for its pregnancy-related function. Subsequent studies revealed that RLX possesses anti-fibrotic functions in tumors and nonreproductive tissues, such as skin, lungs, and others. This aspect of the RLX has been explored for the treatment of various illnesses, such as cardiac fibrosis, liver fibrosis, and solid tumors. With gene therapy coming into age with increasing number of products being approved by regulatory bodies in Europe and United States, we aim to discuss how RLX have been utilized in scope of gene therapy for treatment of various illnesses.

Relaxin and fibrosis: Emerging targets, challenges, and future directions

The peptide hormone relaxin is well-known for its anti-fibrotic actions in several organs, particularly from numerous studies conducted in animals. Acting through its cognate G protein-coupled receptor, relaxin family peptide receptor 1 (RXFP1), serelaxin (recombinant human relaxin) has been shown to consistently inhibit the excessive extracellular matrix production (fibrosis) that results from the aberrant wound-healing response to tissue injury and/or chronic inflammation, and at multiple levels. Furthermore, it can reduce established scarring by promoting the degradation of aberrant extracellular matrix components. Following on from the review that describes the mechanisms and signaling pathways associated with the extracellular matrix remodeling effects of serelaxin (Ng et al., 2019), this review focuses on newly identified tissue targets of serelaxin therapy in fibrosis, and the limitations associated with (se)relaxin research.

Relaxin and extracellular matrix remodeling: Mechanisms and signaling pathways

Fibrosis is associated with accumulation of excess fibrillar collagen, leading to tissue dysfunction. Numerous processes, including inflammation, myofibroblast activation, and endothelial-to-mesenchymal transition, play a role in the establishment and progression of fibrosis. Relaxin is a peptide hormone with well-known antifibrotic properties that result from its action on numerous cellular targets to reduce fibrosis. Relaxin activates multiple signal transduction pathways as a mechanism to suppress inflammation and myofibroblast activation in fibrosis. In this review, the general mechanisms underlying fibrotic diseases are described, along with the current state of knowledge regarding cellular targets of relaxin. Finally, an overview is presented summarizing the signaling pathways activated by relaxin and other relaxin family peptide receptor agonists to suppress fibrosis.

Relaxin-2 for heart failure with preserved ejection fraction (HFpEF): Rationale for future clinical trials

Heart Failure with preserved Ejection Fraction (HFpEF), a distinct sub-entity of chronic heart failure characterized by generalized inflammatory non-compliance of the cardio-vascular system, is associated with high mortality and still an unmet medical need. Many novel and promising therapeutic approaches have failed in large studies. This review focuses on basic research, pre-clinical and clinical findings that may account for the potential benefit of relaxin-2 in HFpEF. The peptide combines short-term hemodynamic advantages, such as moderate blood pressure decline and functional endothelin-1 antagonism, with a wealth of protective effects harboring long-term benefits, such as anti-inflammatory, anti-fibrotic, and anti-oxidative actions. These pleiotropic effects are exerted through a complex and intricate signaling cascade involving the relaxin-family peptide receptor-1, the glucocorticoid receptor, the nitric oxide system, and a cell type-dependent variety of down-stream mediators.

Effects of human relaxin-2 (serelaxin) on hypoxic pulmonary vasoconstriction during acute hypoxia in a sheep model

Purpose

Hypoxia induces pulmonary vasoconstriction with a subsequent increase of pulmonary artery pressure (PAP), which can result in pulmonary hypertension. Serelaxin has shown an increase of pulmonary hemodynamic parameters after serelaxin injection. We therefore investigated the response of pulmonary hemodynamic parameters after serelaxin administration in a clinically relevant model.

Methods

Six controls and six sheep that received 30 μg/kg serelaxin underwent right heart catheterization during a 12-minute hypoxia period (inhalation of 5% oxygen and 95% nitrogen) and subsequent reoxygenation. Systolic, diastolic, and mean values of both PAP (respectively, PAPs, PAPd, and PAPm) and pulmonary capillary wedge pressure (respectively, PCWPs, PCWPd, and PCWPm), blood gases, heart rate (HR), and both peripheral and pulmonary arterial oxygen saturation were obtained. Cardiac output (CO), stroke volume (SV), pulmonary vascular resistance (PVR), pulmonary arterial compliance (PAcompl), and systemic vascular resistance (SVR) were calculated.

Results

The key findings of the current study are that serelaxin prevents the rise of PAPs (p≤0.001), PAPm, PCWPm, PCWPs (p≤0.03), and PAPd (p≤0.05) during hypoxia, while it simultaneously increases CO and SV (p≤0.001). Similar courses of decreases of PAPm, PAPd, PAPs, CO, SVR (p≤0.001), and PCWPd (p≤0.03) as compared to hypoxic values were observed during reoxygenation. In direct comparison, the experimental groups differed during hypoxia in regard to HR, PAPm, PVR, and SVR (p≤0.03), and during reoxygenation in regard to HR (p≤0.001), PAPm, PAPs, PAPd, PVR, SVR (p≤0.03), and PCWPd (p≤0.05).

Conclusion

The findings of this study suggest that serelaxin treatment improves pulmonary hemodynamic parameters during acute hypoxia.

Pulmonary hemodynamic effects and pulmonary arterial compliance during hypovolemic shock and reinfusion with human relaxin-2 (serelaxin) treatment in a sheep model

BACKGROUND

Previous studies on the recombinant form of human relaxin-2 (serelaxin) have shown a decrease of pulmonary hemodynamics after serelaxin injection. Currently, the effect of serelaxin treatment during hypovolemia in a large animal model remains mostly unknown.

METHODS

12 sheep were randomly assigned to a sham or serelaxin (30μg/kg serelaxin) group and underwent right heart catheterization. 50% of the estimated total blood volume were removed to induce hypovolemia, and subsequently retransfused 20 min later (reinfusion). Blood gases, heart rate, peripheral and pulmonary arterial oxygen saturation, systolic, diastolic and mean values of both pulmonary artery pressure (PAP) and pulmonary capillary wedge pressure (PCW) were measured. Cardiac output (CO), pulmonary vascular resistance (PVR), pulmonary arterial compliance (PAcompl) and systemic vascular resistance (SVR) were calculated.

RESULTS

Hypovolemia and shock led to a similar decrease of PAP and PCW in both groups (p≤0.001). CO, SV and PAcompl decreased only in the control group (p≤0.05) and remained higher in the serelaxin-treated group. The results of this study suggest that serelaxin treatment did not negatively influence hemodynamic parameters during hypovolemic shock.

CONCLUSION

The main conclusion of this study is that cardiopulmonary adaption mechanisms are not critically altered by serelaxin administration during severe hypovolemia and retransfusion.

Serelaxin as a novel therapeutic opposing fibrosis and contraction in lung diseases

The most common therapies for asthma and other chronic lung diseases are anti-inflammatory agents and bronchodilators. While these drugs oppose disease symptoms, they do not reverse established structural changes in the airways and their therapeutic efficacy is reduced with increasing disease severity. The peptide hormone, relaxin, is a Relaxin Family Peptide Receptor 1 (RXFP1) receptor agonist with unique combined effects in the lung that differentiates it from these existing therapies. Relaxin has previously been reported to have cardioprotective effects in acute heart failure as well anti-fibrotic actions in several organs. This review focuses on recent experimental evidence of the beneficial effects of chronic relaxin treatment in animal models of airways disease demonstrating inhibition of airway hyperresponsiveness and reversal of established fibrosis, consistent with potential therapeutic benefit. Of particular interest, accumulating evidence demonstrates that relaxin can also acutely oppose contraction by reducing the release of mast cell-derived bronchoconstrictors and by directly eliciting bronchodilation. When used in combination, chronic and acute treatment with relaxin has been shown to enhance responsiveness to both glucocorticoids and β₂-adrenoceptor agonists respectively. While the mechanisms underlying these beneficial actions remain to be fully elucidated, translation of these promising combined preclinical findings is critical in the development of relaxin as a novel alternative or adjunct therapeutic opposing multiple aspects of airway pathology in lung diseases.

Assessment of skin involvement in systemic sclerosis

Skin involvement in SSc is an important marker of disease activity, severity and prognosis, making the assessment of skin a key issue in SSc clinical research. We reviewed the published data assessing skin involvement in clinical trials and summarized the major conclusions important in SSc clinical research. A systematic literature review identified randomized controlled trials using skin outcomes in SSc. Analysis examined the validity of the different skin measures based on literature findings. Twenty-two randomized controlled trials were found. The average study duration was 10.2 (s.d. 4.5) months, mean (s.d.) sample size 32.4 (32.6) and 26.7 (27.8) in intervention and control arms, respectively. The 17-site modified Rodnan skin score is a fully validated primary outcome measure in diffuse cutaneous SSc. Skin histology seems to be an appropriate method for evaluation of skin thickness. These findings have important implications for clinical trial design targeting skin involvement in SSc.

Expression of RXFP1 Is Decreased in Idiopathic Pulmonary Fibrosis. Implications for Relaxin-based Therapies

RATIONALE

Relaxin is a hormone that has been considered as a potential therapy for patients with fibrotic diseases.

OBJECTIVES

To gauge the potential efficacy of relaxin-based therapies in idiopathic pulmonary fibrosis (IPF), we studied gene expression for relaxin/insulin-like family peptide receptor 1 (RXFP1) in IPF lungs and controls.

METHODS

We analyzed gene expression data obtained from the Lung Tissue Research Consortium and correlated RXFP1 gene expression data with cross-sectional clinical and demographic data. We also employed ex vivo donor and IPF lung fibroblasts to test RXFP1 expression in vitro. We tested CGEN25009, a relaxin-like peptide, in lung fibroblasts and in bleomycin injury.

MEASUREMENTS AND MAIN RESULTS

We found that RXFP1 is significantly decreased in IPF. In patients with IPF, the magnitude of RXFP1 gene expression correlated directly with diffusing capacity of the lung for carbon monoxide (P < 0.0001). Significantly less RXFP1 was detected in vitro in IPF fibroblasts than in donor controls. Transforming growth factor-β decreased RXFP1 in both donor and IPF lung fibroblasts. CGEN25009 was effective at decreasing bleomycin-induced, acid-soluble collagen deposition in vivo. The relaxin-like actions of CGEN25009 were abrogated by RXFP1 silencing in vitro, and, in comparison with donor lung fibroblasts, IPF lung fibroblasts exhibited decreased sensitivity to the relaxin-like effects of CGEN25009.

CONCLUSIONS

IPF is characterized by the loss of RXFP1 expression. RXFP1 expression is directly associated with pulmonary function in patients with IPF. The relaxin-like effects of CGEN25009 in vitro are dependent on expression of RXFP1. Our data suggest that patients with IPF with the highest RXFP1 expression would be predicted to be most sensitive to relaxin-based therapies.

Novel Anti-fibrotic Therapies

Fibrosis is a major player in cardiovascular disease, both as a contributor to the development of disease, as well as a post-injury response that drives progression. Despite the identification of many mechanisms responsible for cardiovascular fibrosis, to date no treatments have emerged that have effectively reduced the excess deposition of extracellular matrix associated with fibrotic conditions. Novel treatments have recently been identified that hold promise as potential therapeutic agents for cardiovascular diseases associated with fibrosis, as well as other fibrotic conditions. The purpose of this review is to provide an overview of emerging antifibrotic agents that have shown encouraging results in preclinical or early clinical studies, but have not yet been approved for use in human disease. One of these agents is bone morphogenetic protein-7 (BMP7), which has beneficial effects in multiple models of fibrotic disease. Another approach discussed involves altering the levels of micro-RNA (miR) species, including miR-29 and miR-101, which regulate the expression of fibrosis-related gene targets. Further, the antifibrotic potential of agonists of the peroxisome proliferator-activated receptors will be discussed. Finally, evidence will be reviewed in support of the polypeptide hormone relaxin. Relaxin is long known for its extracellular remodeling properties in pregnancy, and is rapidly emerging as an effective antifibrotic agent in a number of organ systems. Moreover, relaxin has potent vascular and renal effects that make it a particularly attractive approach for the treatment of cardiovascular diseases. In each case, the mechanism of action and the applicability to various fibrotic diseases will be discussed.

The mighty fibroblast and its utility in scleroderma research

Fibroblasts are the effector cells of fibrosis characteristic of systemic sclerosis (SSc, scleroderma) and other fibrosing conditions. The excess production of extracellular matrix (ECM) proteins is the hallmark of fibrosis in different organs, such as skin and lung. Experiments designed to assess the pro-fibrotic capacity of factors, their signaling pathways, and potential inhibitors of their effects that are conducted in fibroblasts have paved the way for planning clinical trials in SSc. As such, fibroblasts have proven to be valuable tools in the search for effective anti-fibrotic therapies for fibrosis. Herein we highlight the characteristics of fibroblasts, their role in the etiology of fibrosis, utility in experimental assays, and contribution to drug development and clinical trials in SSc.

Anti-fibrotic actions of relaxin

Fibrosis refers to the hardening or scarring of tissues that usually results from aberrant wound healing in response to organ injury, and its manifestations in various organs have collectively been estimated to contribute to around 45-50% of deaths in the Western world. Despite this, there is currently no effective cure for the tissue structural and functional damage induced by fibrosis-related disorders. Relaxin meets several criteria of an effective anti-fibrotic based on its specific ability to inhibit pro-fibrotic cytokine and/or growth factor-mediated, but not normal/unstimulated, fibroblast proliferation, differentiation and matrix production. Furthermore, relaxin augments matrix degradation through its ability to up-regulate the release and activation of various matrix-degrading matrix metalloproteinases and/or being able to down-regulate tissue inhibitor of metalloproteinase activity. Relaxin can also indirectly suppress fibrosis through its other well-known (anti-inflammatory, antioxidant, anti-hypertrophic, anti-apoptotic, angiogenic, wound healing and vasodilator) properties. This review will outline the organ-specific and general anti-fibrotic significance of exogenously administered relaxin and its mechanisms of action that have been documented in various non-reproductive organs such as the cardiovascular system, kidney, lung, liver, skin and tendons. In addition, it will outline the influence of sex on relaxin's anti-fibrotic actions, highlighting its potential as an emerging anti-fibrotic therapeutic.

LINKED ARTICLES

This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.

Synthetic non-peptide low molecular weight agonists of the relaxin receptor 1

Relaxin is a small heterodimeric peptide hormone of the insulin/relaxin superfamily produced mainly in female and male reproductive organs. It has potent antifibrotic, vasodilatory and angiogenic effects and regulates the normal function of various physiological systems. Preclinical studies and recent clinical trials have shown the promise of recombinant relaxin as a therapeutic agent in the treatment of cardiovascular and fibrotic diseases. However, there are the universal drawbacks of peptide-based pharmacology that apply to relaxin: a short half-life in vivo requires its continuous delivery, and there are high costs of production, storage and treatment, as well as the possibility of immune responses. All these issues can be resolved by the development of low non-peptide MW agonists of the relaxin receptors which are stable, bioavailable, easily synthesized and specific. In this review, we describe the discovery and characterization of the first series of such compounds. The lead compound, ML290, binds to an allosteric site of the relaxin GPCR, RXFP1. ML290 shows high activity and efficacy, measured by cAMP response, in cells expressing endogenous or transfected RXFP1. Relaxin-like effects of ML290 were shown in various functional cellular assays in vitro. ML290 has excellent absorption, distribution, metabolism and excretion properties and in vivo stability. The identified series of low MW agonists does not activate rodent RXFP1 receptors and thus, the production of a RXFP1 humanized mouse model is needed for preclinical studies. The future analysis and clinical perspectives of relaxin receptor agonists are discussed.

LINKED ARTICLES

This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.

Simultaneously Targeting Myofibroblast Contractility and Extracellular Matrix Cross-Linking as a Therapeutic Concept in Airway Fibrosis

Fibrosis after solid organ transplantation is considered an irreversible process and remains the major cause of graft dysfunction and death with limited therapies. This remodeling is characterized by aberrant accumulation of contractile myofibroblasts that deposit excessive extracellular matrix (ECM) and increase tissue stiffness. Studies demonstrate, however, that a stiff ECM itself promotes fibroblast-to-myofibroblast differentiation, stimulating further ECM production. This creates a positive feedback loop that perpetuates fibrosis. We hypothesized that simultaneously targeting myofibroblast contractility with relaxin and ECM stiffness with lysyl oxidase inhibitors could break the feedback loop, reversing established fibrosis. To test this, we used the orthotopic tracheal transplantation (OTT) mouse model, which develops robust fibrotic airway remodeling. Mice with established fibrosis were treated with saline, mono-, or combination therapies. Although monotherapies had no effect, combining these agents decreased collagen deposition and promoted re-epithelialization of remodeled airways. Relaxin inhibited myofibroblast differentiation and contraction in a matrix-stiffness-dependent manner through prostaglandin E₂ (PGE₂ ). Furthermore, the effect of combination therapy was lost in PGE₂ receptor knockout and PGE₂ -inhibited OTT mice. This study revealed the important synergistic roles of cellular contractility and tissue stiffness in the maintenance of fibrotic tissue and suggests a new therapeutic principle for fibrosis.

Serelaxin in clinical development: past, present and future

The availability of highly purified recombinant human relaxin, serelaxin, has allowed clinical trials to be conducted in several indications and the elucidation of its pharmacology in human subjects. These studies have demonstrated that serelaxin has unique haemodynamic properties that are likely to contribute to organ protection and long-term outcome benefits in acute heart failure. Clinical observations support its consideration for therapeutic use in other patient populations, including those with chronic heart failure, coronary artery disease, portal hypertension and acute renal failure.

LINKED ARTICLES

This article is part of a themed section on Recent Progress in the Understanding of Relaxin Family Peptides and their Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.10/issuetoc.

Targeted Therapy in Systemic Sclerosis

Targeted therapies use an understanding of the pathophysiology of a disease in an individual patient. Although targeted therapy for systemic sclerosis (SSc, scleroderma) has not yet reached the level of patient-specific treatments, recent developments in the understanding of the global pathophysiology of the disease have led to new treatments based on the cells and pathways that have been shown to be involved in the disease pathogenesis. The presence of a B cell signature in skin biopsies has led to the trial of rituximab, an anti-CD20 antibody, in SSc. The well-known properties of transforming growth factor (TGF)-β in promoting collagen synthesis and secretion has led to a small trial of fresolimumab, a human IgG4 monoclonal antibody capable of neutralizing TGF-β. Evidence supporting important roles for interleukin-6 in the pathogenesis of SSc have led to a large trial of tocilizumab in SSc. Soluble guanylate cyclase (sGC) is an enzyme that catalyzes the production of cyclic guanosine monophosphate (cGMP) upon binding of nitric oxide (NO) to the sGC molecule. Processes such as cell growth and proliferation are regulated by cGMP. Evidence that sGC may play a role in SSc has led to a trial of riociguat, a molecule that sensitizes sGC to endogenous NO. Tyrosine kinases (TKs) are involved in a wide variety of physiologic and pathological processes including vascular remodeling and fibrogenesis such as occurs in SSc. This has led to a trial of nintedanib, a next-generation tyrosine-kinase (TK) inhibitor which targets multiple TKs, in SSc.

Serelaxin for the treatment of heart failure

Outcomes for patients with acute heart failure remain suboptimal and treatments principally target improvement of symptoms. To date there has been no therapy approved for acute heart failure shown to improve mortality or readmission risk post-discharge. Serelaxin, a recombinant form of the naturally occurring polypeptide hormone relaxin, has demonstrated promise in preclinical and early clinical trials as a potentially novel therapy for acute heart failure. It is postulated through its anti-fibrotic and vasodilatory effects that this agent can improve outcomes in both the short and long term in these patients. Randomized clinical data has suggested that the medication is safe and well tolerated. However, definitive outcomes data is currently being assessed in a large multi-center trial.

Relaxin deficiency results in increased expression of angiogenesis- and remodelling-related genes in the uterus of early pregnant mice but does not affect endometrial angiogenesis prior to implantation

BACKGROUND

Extensive uterine adaptations, including angiogenesis, occur prior to implantation in early pregnancy and are potentially regulated by the peptide hormone relaxin. This was investigated in two studies. First, we took a microarray approach using human endometrial stromal (HES) cells treated with relaxin in vitro to screen for target genes. Then we aimed to investigate whether or not relaxin deficiency in mice affected uterine expression of representative genes associated with angiogenesis and uterine remodeling, and also blood vessel proliferation in the pre-implantation mouse endometrium.

METHODS

Normal HES cells were isolated and treated with recombinant human relaxin (10 ng/ml) for 24 h before microarray analysis. Reverse transcriptase PCR was used to analyze gene expression of relaxin and its receptor (Rxfp1) in ovaries and uteri; quantitative PCR was used to analyze steroid receptor, angiogenesis and extracellular matrix remodeling genes in the uteri of wild type (Rln+/+) and Rln-/- mice on days 1-4 of pregnancy. Immunohistochemistry localized endometrial endothelial cell proliferation and mass spectrometry measured steroid hormones in the plasma.

RESULTS

Microarray analysis identified 63 well-characterized genes that were differentially regulated in HES cells after relaxin treatment. Expression of some of these genes was increased in the uterus of Rln+/+ mice by day 4 of pregnancy. There was significantly higher vascular endothelial growth factor A (VegfA), estrogen receptor 1 (Esr1), progesterone receptor (Pgr), Rxfp1, egl-9 family hypoxia-inducible factor 1 (Egln1), hypoxia inducible factor 1 alpha (Hif1α), matrix metalloproteinase 14 (Mmp14) and ankryn repeat domain 37 (Ankrd37) in Rln-/- compared to Rln+/+ mice on day 1. Progesterone receptor expression and plasma progesterone levels were higher in Rln-/- mice compared to Rln+/+ mice. However, endometrial angiogenesis was not advanced as pre-implantation endothelial cell proliferation did not differ between genotypes.

CONCLUSIONS

Relaxin treatment modulates expression of a variety of angiogenesis-related genes in HES cells. However, despite accelerated uterine gene expression of steroid receptor, progesterone and angiogenesis and extracellular matrix remodeling genes in Rln-/- mice, there was no impact on angiogenesis. We conclude that although relaxin deficiency results in phenotypic changes in the pre-implantation uterus, endogenous relaxin does not play a major role in pre-implantation angiogenesis in the mouse uterus.

International Union of Basic and Clinical Pharmacology. XCV. Recent advances in the understanding of the pharmacology and biological roles of relaxin family peptide receptors 1-4, the receptors for relaxin family peptides

Relaxin, insulin-like peptide 3 (INSL3), relaxin-3, and INSL5 are the cognate ligands for the relaxin family peptide (RXFP) receptors 1-4, respectively. RXFP1 activates pleiotropic signaling pathways including the signalosome protein complex that facilitates high-sensitivity signaling; coupling to Gα(s), Gα(i), and Gα(o) proteins; interaction with glucocorticoid receptors; and the formation of hetero-oligomers with distinctive pharmacological properties. In addition to relaxin-related ligands, RXFP1 is activated by Clq-tumor necrosis factor-related protein 8 and by small-molecular-weight agonists, such as ML290 [2-isopropoxy-N-(2-(3-(trifluoromethylsulfonyl)phenylcarbamoyl)phenyl)benzamide], that act allosterically. RXFP2 activates only the Gα(s)- and Gα(o)-coupled pathways. Relaxin-3 is primarily a neuropeptide, and its cognate receptor RXFP3 is a target for the treatment of depression, anxiety, and autism. A variety of peptide agonists, antagonists, biased agonists, and an allosteric modulator target RXFP3. Both RXFP3 and the related RXFP4 couple to Gα(i)/Gα(o) proteins. INSL5 has the properties of an incretin; it is secreted from the gut and is orexigenic. The expression of RXFP4 in gut, adipose tissue, and β-islets together with compromised glucose tolerance in INSL5 or RXFP4 knockout mice suggests a metabolic role. This review focuses on the many advances in our understanding of RXFP receptors in the last 5 years, their signal transduction mechanisms, the development of novel compounds that target RXFP1-4, the challenges facing the field, and current prospects for new therapeutics.

Recombinant human relaxin-2: (how) can a pregnancy hormone save lives in acute heart failure?

Acute heart failure (AHF) syndrome, characterized by pulmonary and/or venous congestion owing to increased cardiac filling pressures with or without diminished cardiac output, is still associated with high post-discharge mortality and hospitalization rates. Many novel and promising therapeutic approaches, among them endothelin-1, vasopressin and adenosine antagonists, calcium sensitization, and recombinant B-type natriuretic hormone, have failed in large studies. Likewise, the classic drugs, vasodilators, diuretics, and inotropes, have never been shown to lower mortality.The phase III trial RELAX-AHF tested recombinant human relaxin-2 (rhRlx) and found it to improve clinical symptoms moderately, to be neutral regarding the combination of death and hospitalization at day 60, to be safe, and to lower mortality at day 180. This review focuses on basic research and pre-clinical findings that may account for the benefit of rhRlx in AHF. The drug combines short-term hemodynamic advantages, such as moderate blood pressure decline and functional endothelin-1 antagonism, with a wealth of protective effects harboring long-term benefits, such as anti-inflammatory, anti-fibrotic, and anti-oxidative actions. These pleiotropic effects are exerted through a complex and intricate signaling cascade involving the relaxin-family peptide receptor-1, the glucocorticoid receptor, nitric oxide, and a cell type-dependent variety of kinases and transcription factors.

Twenty-two points to consider for clinical trials in systemic sclerosis, based on EULAR standards

OBJECTIVE

SSc is clinically and aetiopathogenically heterogeneous. Consensus standards for more uniform trial design and selection of outcome measures are needed. The objective of this study was to develop evidence-based points to consider (PTCs) for future clinical trials in SSc.

METHODS

Thirteen international SSc experts experienced in SSc clinical trial design were invited to participate. One researcher with experience in systematic literature review and three trainees were also included. A systematic review using PubMed and the Cochrane Central Register of Controlled Trials was conducted and PTCs when designing clinical trials in SSc were developed. As part of that development we conducted an Internet-based Delphi exercise regarding the main points to be made in the consensus statement. Consensus was defined as achieving a median score of ≥7 of 9.

RESULTS

By consensus, the experts decided to develop PTCs for each individual organ system. The current document provides a unifying outline on PTCs regarding general trial design, inclusion/exclusion criteria and analysis. Consensus was achieved regarding all the main points of the PTCs.

CONCLUSION

Using European League Against Rheumatism suggestions for PTCs, a general outline for PTCs for controlled clinical trials in SSc was developed. Specific outlines for individual organ systems are to be published separately. This general outline should lead to more uniform and higher-quality trials and clearly delineate areas where further research is needed.

Animal models of systemic sclerosis: their utility and limitations

Without doubt, animal models have provided significant insights into our understanding of the rheumatological diseases; however, no model has accurately replicated all aspects of any autoimmune disease. Recent years have seen a plethora of knockouts and transgenics that have contributed to our knowledge of the initiating events of systemic sclerosis, an autoimmune disease. In this review, the focus is on models of systemic sclerosis and how they have progressed our understanding of fibrosis and vasculopathy, and whether they are relevant to the pathogenesis of systemic sclerosis.