Cited by 1Pregnancy-related medical researchCardiac Fibrosis and RemodelingApelin-related biomedical research

Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

Open access
Du, Xiao-Jun·2025·Cardiovascular Research

Abstract

Xiao-Jun Du, MBBS, PhD; Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases, Cardiovascular Research, , cvaf057, https://

AI snapshot

Written from the paper’s full text.

TL;DR

This editorial reviews the state of relaxin receptor (RXFP1)-targeted therapy for cardiovascular disease, prompted by a new study of the long-acting relaxin analogue AZD3427 in non-human primates with heart failure. It argues that the field is reviving after the RELAX-AHF failure, while flagging unresolved questions about chronic RXFP activation, mechanism, and delivery.

Key findings

The commentary highlights that AZD3427, an Fc-fused human relaxin with half-life extended to roughly 120 h, improved LVEF and stroke volume and lowered peripheral vascular resistance in aged non-human primates with HFrEF, with LVEF gains beginning at week 5 and continuing across 21 weeks of once-weekly subcutaneous dosing, then declining slowly over an 18-week washout. Unlike serelaxin in patients, AZD3427 produced no heart-rate increase and no improvement in the urinary albumin-to-creatinine ratio in this model. The author notes that the RELAX-AHF phase-III trial of serelaxin failed its primary endpoints of 6-month total and cardiovascular adverse events despite hemodynamic and biomarker benefits, and that relaxin as a peptide drug suffers from short action (<5 h), i.v. infusion requirement, nonlinear dose–response, and high production cost. He also points to ongoing development of oral small-molecule RXFP1 agonists, including AZD5462 (derived from ML290, itself found by screening 367,000 compounds), now in a 24-week phase IIb trial in stable chronic heart failure.

Methods

This is a narrative editorial/commentary, not an original study; it has no primary data, sample, or statistical analysis of its own. Its evidence base is the accompanying Papworth et al. paper on AZD3427 in non-human primates, the RELAX-AHF trial series and related serelaxin literature, a phase Ia/b first-in-human AZD3427 study, and prior reports on RXFP1 small-molecule agonists and relaxin fusion proteins/mRNA therapeutics. The author's assessment is organized around methodological strengths of the Papworth study (aged high-fat-diet NHP HFrEF model with comorbidities, randomized double-blind design, serial echocardiography, 18-week washout, ex vivo receptor pharmacology) and around gaps in knowledge of chronic RXFP activation.

Limitations

The author states that the reason for the slow onset and gradual loss of hemodynamic benefit with AZD3427 is unclear, possibly involving peripheral vascular resistance, ventricular performance, and pathological remodelling, and notes that myocardial tissue profiling was not performed. He also notes that the sustained rise in plasma renin with AZD3427 in HF animals is unexplained, and that differences from serelaxin results may stem from species, biological age, treatment duration, disease type, or differing RXFP signalling. Evident from the text itself: this is a single-author editorial without primary data, so its conclusions rest on interpretation of others' work; the comparison between AZD3427 in monkeys and serelaxin in patients is cross-species and cross-disease, and the author explicitly says the mechanisms of binding and activation by novel agonists, biased signalling, and long-term efficacy in HFpEF or acutely decompensated HF remain untested.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1093/cvr/cvaf057

Cites

10 of 10 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

20 of 42 cited sources checked · 11 supported · 0 flagged · accuracy not yet measured

  • Premisecitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    The RELAX-AHF phase-III clinical trial failed to achieve its primary end-points of lowering 6-month total and cardiovascular adverse events.

    “However, the RELAX -AHF phase-III clinical trial failed in achieving the primary end -points of lowering the 6-month total and cardiovascular adverse events, 3”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [3] Metra, 2019, . Effects of serelaxin in patients with acute heart failure, N Engl J Med source

      The Primary and Key Secondary End Points section reports that RELAX-AHF-2 did not significantly reduce cardiovascular death at 180 days and that death from any cause was similar between groups. But the claim names RELAX-AHF rather than RELAX-AHF-2 and calls both six-month outcomes primary end points; the Primary and Secondary End Points section identifies all-cause death as secondary and worsening heart failure at 5 days as the other primary end point. The indexed passages provide no page number. (LLM, conf=0.88)

      Experimental — accuracy not yet measured
  • Premisecitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    AZD3427 was developed by fusion of the human IgG Fc portion to human relaxin.

    “AZD3427 was developed by the fusion of human IgG Fc portion to human relaxin.7”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [7] Connolly, 2024, Novel relaxin receptor RXFP1 agonist AZD3427 in the treatment of heart failure: a phase 1a/b, first-in-human, randomized, single-blind, placebo-controlled study, J Am Heart Assoc source

      The introductory passage under Abstract > Registration describes AZD3427 as a fusion protein containing the Fc portion of human IgG1. It says that portion is linked to a peptide sequence derived from human relaxin, not to human relaxin itself. (LLM, conf=0.85)

      Experimental — accuracy not yet measured
  • Premisecitation

    LVEF exhibited a slow and progressive decline during the 18-week washout period towards the pre-treatment baseline.

    “Likewise, LVEF exhibited a slow and progressive decline during the 18-week washout period towards the pre-treatment baseline.6”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] Papworth, 2025, A novel long-acting relaxin-2 fusion, AZD3427, improves cardiac performance in non-human primates with cardiac dysfunction, Cardiovasc Res source
  • Study design and conductcitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    The study was a randomized and double-blind drug trial.

    “this study was a randomized and double-blind drug trial.”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] Papworth, 2025, A novel long-acting relaxin-2 fusion, AZD3427, improves cardiac performance in non-human primates with cardiac dysfunction, Cardiovasc Res source

      Methods, ‘NHP study cohort and design,’ says the non-human primates were randomized to vehicle or AZD3427 treatment groups. Methods, ‘Imaging and HDO,’ says assessors were blinded to treatment assignment, but does not establish that the study was double-blind. (LLM, conf=0.90)

      Experimental — accuracy not yet measured
  • Premisecitation

    Papworth et al found no evidence for heart rate increment by AZD3427 treatment in the NHP model.

    “Papworth et al found no evidence for either heart rate increment or improvement of renal parameter urinary albumin creatinine ratio (UACR) by AZD3427 treatment in the NHP model.6”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] Papworth, 2025, A novel long-acting relaxin-2 fusion, AZD3427, improves cardiac performance in non-human primates with cardiac dysfunction, Cardiovasc Res source
  • May combine two claims. 10
  • Classified as probably not a substantial claim. 2
  • May combine two claims.

    Premisecitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    Despite the RELAX-AHF trial failure, clinical benefits in haemodynamics and biomarker profile were demonstrated.

    “despite the demonstration of clinical benefits in haemodynamics and biomarker profile.4,5”
    Quote in the paperSubstantial claim2 of 2 sources checked
    • cites [4] Teerlink, 2020, Effects of serelaxin in patients admitted for acute heart failure: a meta-analysis, Eur J Heart Fail source
    • cites [5] Grand, 2022, Blood pressure drops during hospitalization for acute heart failure treated with serelaxin: a patient-level analysis of 4 randomized controlled trials, Circ Heart Fail source

      The Conclusions (page unavailable) say that blood-pressure drops appeared less harmful in patients treated with serelaxin than in those receiving usual care or placebo, providing limited support for a haemodynamic benefit. The paper does not demonstrate a benefit in biomarker profile; it uses NT-proBNP in its analyses but does not report an improvement in it with serelaxin. (LLM, conf=0.82)

      Experimental — accuracy not yet measured
  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductcitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    The study included an 18-week washout observation, which is helpful to confirm the efficacy of AZD3427.

    “the authors astutely included an 18-week period of washout observation, which is helpful to confirm the efficacy of AZD3427.”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [6] Papworth, 2025, A novel long-acting relaxin-2 fusion, AZD3427, improves cardiac performance in non-human primates with cardiac dysfunction, Cardiovasc Res source
  • May combine two claims.

    Premisecitation

    Papworth et al showed improvement in LVEF starting from week-5 and progressively further improving throughout the 21-week treatment without a sign of reaching a plateau.

    “Papworth et al clearly showed improvement in LVEF starting from week-5 and progressively further improving throughout the 21-week period of treatment without a sign of reaching a plateau.6”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] Papworth, 2025, A novel long-acting relaxin-2 fusion, AZD3427, improves cardiac performance in non-human primates with cardiac dysfunction, Cardiovasc Res source

      The Results (page unavailable) report improved ejection fraction in treated non-human primates at 21 weeks, and the Discussion says EF had not reached a pharmacodynamic steady state by then, supporting the no-plateau point. The Methods list an assessment at Week 5, but our copy does not state that improvement began then or that EF increased progressively at every assessment through Week 21. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
  • May combine two claims.

    Premisecitation

    A NIH team identified two lead hits following screening of 367,000 compounds, including a lead ML290, from which a derivative AZD5462 was obtained.

    “a NIH team identified two lead hits following meticulous screening of 367,000 compounds, 9 including a lead ML290, from which a derivative AZD5462 was obtained (Figure ). 10”
    Quote in the paperNot a substantial claim1 of 2 sources checked
    • cites [9] Chen, 2013, Identification of small-molecule agonists of human relaxin family receptor 1 (RXFP1) by using a homogenous cell-based cAMP assay, J Biomol Screen source
    • cites [10] Granberg, 2024, Discovery of clinical candidate AZD5462, a celective oral allosteric RXFP1 agonist for treatment of heart failure, J Med Chem source
  • May combine two claims.

    Study design and conductcitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    A HFrEF model was developed in aged NHPs by 2-year high-fat-diet feeding, leading to phenotypes simulating clinical conditions, including LV systolic dysfunction and comorbidities (obesity, dyslipidaemia, early signs of hypertension and diabetes).

    “a HFrEF model was developed in aged NHPs by 2-year high-fat-diet feeding, leading to phenotypes simulating clinical conditions, including LV systolic dysfunction and presence of comorbidities (e.g.obesity, dyslipidaemia, and early signs of hypertension and diabetes).”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [6] Papworth, 2025, A novel long-acting relaxin-2 fusion, AZD3427, improves cardiac performance in non-human primates with cardiac dysfunction, Cardiovasc Res source
  • May combine two claims.

    Premisecitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    Relaxin is a peptide hormone that binds primarily to RXFP1 and initiates complex signaling.

    “Relaxin is a peptide hormone that binds to the G protein-coupled relaxin family peptide receptor (RXFP), primarily RXFP1, initiating complex signaling.1,2”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [1] Bathgate, 2013, Relaxin family peptides and their receptors, Physiol Rev source
    • cites [2] Du, 2010, Cardiovascular effects of relaxin: from basic science to clinical therapy, Nat Rev Cardiol source
  • May combine two claims.

    Premisecitation
    § Revivifying research on relaxin receptor-targeted therapy for cardiovascular diseases

    Preclinical data suggest relaxin has beneficial cardiovascular effects, including lowering peripheral vascular resistance, improving renal function, and antagonizing fibrosis, inflammation, and ischemic injury.

    “Abundant preclinical data suggest beneficial cardiovascular effects of relaxin including lowering peripheral vascular resistance, improving renal function and antagonizing fibrosis, inflammation and ischemic injury.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [1] Bathgate, 2013, Relaxin family peptides and their receptors, Physiol Rev source
    • cites [2] Du, 2010, Cardiovascular effects of relaxin: from basic science to clinical therapy, Nat Rev Cardiol source
  • May combine two claims.

    Premisecitation

    According to the RELAX-AHF study, infusion with serelaxin (48 hours) induced rapid onset (from day-2) of favourable effects in biomarker profiles, hemodynamics (e.g. reduction in perivascular resistance, modest increase in heart rate) and renal function (estimated by creatinine or eGFR).

    “According to the RELAX-AHF study, infusion with serelaxin (48 hours) induced rapid onset (from day-2) of favourable effects in biomarker profiles, hemodynamics (e.g.reduction in perivascular resistance, modest increase in heart rate) and renal function (estimated by creatinine or eGFR).[3][4][5]”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [3][4][5]

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Interpretationreasoning

    Papworth et al present an important piece of translational research with the findings supporting further clinical development of AZD3427 for HF therapy.

    “Papwerth et al present an important piece of translational research with the findings supporting further clinical development of AZD3427 for HF therapy.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: The beneficial effects of AZD3427 in the NHP HFrEF model predict clinical benefit in human HF patients.
  • May combine two claims.

    Premisecitation

    Full activation of RXFP requires relaxin binding at both the ectodomain and the transmembrane loop, and the presence of the LDLa domain.

    “Full activation of RXFP requires relaxin binding at both the ectodomain and the transmembrane loop, and the presence of the LDLa domain (Figure ).1,2”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [1] Bathgate, 2013, Relaxin family peptides and their receptors, Physiol Rev source
    • cites [2] Du, 2010, Cardiovascular effects of relaxin: from basic science to clinical therapy, Nat Rev Cardiol source
10 of 10
  • The paper relies on this without support.

    The beneficial effects of AZD3427 in the NHP HFrEF model predict clinical benefit in human HF patients.

    “Papwerth et al present an important piece of translational research with the findings supporting further clinical development of AZD3427 for HF therapy.”
1 of 1

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Authors
Du, X.-J.
Affiliations
Baker Heart and Diabetes Institute (AU)
Corresponding author
Du, Xiao-Jun
Venue
Cardiovascular Research
Published
2025-04-17
Volume
121
Issue
6
Pages
836-838
ISSN
  • 0008-6363 (ISSN-L)
  • 1755-3245
OpenAlex
W4409556966
Cited by
1
References
10
Citations by year
2025: 1
Type
journal article
Language
en
Open access
Locations
  • Cardiovascular Research (publishedVersion)
  • PubMed (publishedVersion)
Funders
  • NHMRC of Australia
  • Nature Science Fund of China
Topics
  • Health Sciences › Medicine › Public Health, Environmental and Occupational Health › Pregnancy-related medical research
  • Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Cardiac Fibrosis and Remodeling
  • Health Sciences › Medicine › Pharmacology › Apelin-related biomedical research
Keywords
relaxin receptor, cardiovascular disease, relaxin, cardiovascular pharmacology

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