--- title: "Serelaxin" canonical_url: https://peptidelibrary.app/library/serelaxin description: "Recombinant form of the human hormone relaxin-2, investigated for acute heart failure. A large phase 3 outcomes trial did not meet its primary endpoints and development was discontinued. Not FDA-approved." updated: 2026-11-07 publisher: Peptide Library notice: "Research and educational use only. Not medical advice." --- # Serelaxin Serelaxin is a research peptide in the Relaxin Receptor Agonist class. Serelaxin binds the relaxin family peptide receptor 1, a G protein-coupled receptor expressed on vascular smooth muscle and endothelium. Signalling raises cyclic AMP and increases nitric oxide and endothelin type B receptor activity, producing systemic and renal vasodilation, and has additionally been reported to have antifibrotic effects mediated through reduced TGF-beta signalling. Recombinant form of the human hormone relaxin-2, investigated for acute heart failure. A large phase 3 outcomes trial did not meet its primary endpoints and development was discontinued. Not FDA-approved. ## Classification - Type: Recombinant human relaxin-2 / discontinued - Mechanism class: Relaxin Receptor Agonist - Development stage: Development discontinued - Regulatory class: Withdrawn or rejected, not approved ## Mechanism Serelaxin binds the relaxin family peptide receptor 1, a G protein-coupled receptor expressed on vascular smooth muscle and endothelium. Signalling raises cyclic AMP and increases nitric oxide and endothelin type B receptor activity, producing systemic and renal vasodilation, and has additionally been reported to have antifibrotic effects mediated through reduced TGF-beta signalling. ## Properties - Molecular formula: C256H408N74O74S8 - Molecular weight: 5,963 g/mol - CAS number: 99489-94-8 - Studied routes: Intravenous ## Evidence - Evidence level: Clinical Trial Evidence - Highest documented: Controlled human trials - Human trials: 2 - Controlled human trials: 2 - Preclinical sources: 0 - Latest source: 2019 Each step shows whether the sources Peptide Library has reviewed include that kind of research. Counts are reviewed sources, not every study ever published. Reviews and programme summaries that describe human use are shown as "reported", not as trials, and registered trials without published results are listed but not counted. A higher step means research has progressed further; it does not mean a compound works better or is safer. Compounds whose evidence has not been reviewed yet show "Not reviewed" instead of a guess. ### Studies 1. Serelaxin, recombinant human relaxin-2, for treatment of acute heart failure (RELAX-AHF): a randomised, placebo-controlled trial. Lancet. 2013. 2013. Controlled human trial. Population: Adults hospitalised for acute heart failure with dyspnoea, congestion, raised natriuretic peptides, mild-to-moderate renal insufficiency and systolic blood pressure above 125 mm Hg (n=1,161). Improved dyspnoea on the visual analogue scale (one primary endpoint) but not on the Likert scale (the other); no effect on cardiovascular death or readmission at 60 days; fewer deaths at day 180 was a prespecified additional endpoint [Source](https://pubmed.ncbi.nlm.nih.gov/23141816/) 2. Effects of Serelaxin in Patients with Acute Heart Failure. N Engl J Med. 2019. 2019. Controlled human trial. Population: Adults hospitalised for acute heart failure meeting the same criteria (6,545 analysed). Both primary endpoints missed: cardiovascular death at 180 days 8.7% versus 8.9% (HR 0.98) and worsening heart failure at 5 days 6.9% versus 7.7% (HR 0.89); adverse events similar [Source](https://pubmed.ncbi.nlm.nih.gov/31433919/) ## Safety Human safety basis: Clinical trial reports Key limitations: Not approved by the FDA for any use.. ## Regulatory status Serelaxin was withdrawn from the market or rejected for approval. It is not an approved product. - FDA status: Withdrawn / Rejected - Availability: Research-Only ## Frequently asked questions ### What is Serelaxin? Recombinant form of the human hormone relaxin-2, investigated for acute heart failure. A large phase 3 outcomes trial did not meet its primary endpoints and development was discontinued. Not FDA-approved. ### How does Serelaxin work? Serelaxin binds the relaxin family peptide receptor 1, a G protein-coupled receptor expressed on vascular smooth muscle and endothelium. Signalling raises cyclic AMP and increases nitric oxide and endothelin type B receptor activity, producing systemic and renal vasodilation, and has additionally been reported to have antifibrotic effects mediated through reduced TGF-beta signalling. ### Is Serelaxin FDA approved? No. Serelaxin is not currently FDA-approved. Its development or marketing was discontinued, which can happen for commercial reasons as well as safety or efficacy ones. Any material available today is not an approved product. ### What peptides are similar to Serelaxin? Compounds most often compared with Serelaxin include ARA 290 (Cibinetide), Atosiban and Carbetocin. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ. ## References - [Serelaxin, recombinant human relaxin-2, for heart failure patients: A systematic review and meta-analysis — Medicine (Baltimore), 2018](https://pubmed.ncbi.nlm.nih.gov/29923986/) - [Effects of Serelaxin in Patients with Acute Heart Failure — N Engl J Med, 2019](https://pubmed.ncbi.nlm.nih.gov/31433919/) - [Serelaxin, recombinant human relaxin-2, for treatment of acute heart failure (RELAX-AHF): a randomised, placebo-controlled trial — Lancet, 2013](https://pubmed.ncbi.nlm.nih.gov/23141816/) - [Human Recombinant Relaxin (Serelaxin) as Anti-fibrotic Agent: Pharmacology, Limitations and Actual Perspectives — Curr Mol Med, 2022](https://pubmed.ncbi.nlm.nih.gov/33687895/) - [Serelaxin and acute heart failure — Heart, 2016](https://pubmed.ncbi.nlm.nih.gov/26603680/)