Peptide LibrarySerelaxin
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.
For research use only.
Key Facts
- CAS
- 99489-94-8
- Molecular Weight (MW)
- 5963 g/mol
- Half-life
- —
- FDA status
- Withdrawn / Rejected
- Evidence level
- Clinical Trial Evidence
- Human dose established
- Yes
- Administration Route
- Intravenous
- Frequency
- Continuous intravenous infusion
- Last updated
- Nov 7, 2026
- Reviewed
- Nov 7, 2026
Research summary
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.
Research evidence
- Regulatory review (FDA label)None in reviewed sources
- Controlled human trials2 reviewed sources
- Early or uncontrolled human studiesNone in reviewed sources
- Lab & animal studiesNone in reviewed sources
How it works
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.
Peptide Library's Serelaxin profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
Serelaxin dosage evidence
Serelaxin has no approved dosage; there is no serelaxin label on DailyMed. Its human dosing comes from the RELAX-AHF trials in people hospitalised for acute heart failure, which gave a 48-hour intravenous infusion of 30 mcg/kg per day. RELAX-AHF met one of its two dyspnoea endpoints, but the larger RELAX-AHF-2 trial did not reduce cardiovascular death at 180 days or worsening heart failure at 5 days.
| Human dosing established | Yes |
|---|---|
| Route | Intravenous |
| Frequency | Continuous intravenous infusion |
| Duration studied | 48 hours, started within 16 hours of presentation |
| Evidence level | Clinical Trial Evidence |
| Last reviewed | 2026-11-07 |
Research-reported dosing
Doses as studied, one row per regimen. Different trials used different regimens; they are listed separately rather than averaged.
| Study / context | Population | Dose | Route | Frequency | Duration | Outcome studied | Source |
|---|---|---|---|---|---|---|---|
| RELAX-AHF — Lancet 2013 (NCT00520806)Clinical trial · Randomised, double-blind, placebo-controlled trial | 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) | 30 mcg/kg per day, or placebo, with standard care | Intravenous | Continuous infusion | 48 hours | 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 | Serelaxin, recombinant human relaxin-2, for treatment of acute heart failure (RELAX-AHF): a randomised, placebo-controlled trial. Lancet. 2013. |
| RELAX-AHF-2 — NEJM 2019 (NCT01870778)Clinical trial · Event-driven, randomised, double-blind, placebo-controlled trial | Adults hospitalised for acute heart failure meeting the same criteria (6,545 analysed) | 30 mcg/kg per day, or placebo, with standard care | Intravenous | Continuous infusion | 48 hours | 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 | Effects of Serelaxin in Patients with Acute Heart Failure. N Engl J Med. 2019. |
Where sources disagree
- Serelaxin is recombinant human relaxin-2. Its trial dose is weight-based and was given only as a 48-hour hospital infusion; no other route or schedule was tested in these trials.
- The fewer deaths at day 180 reported in RELAX-AHF were an additional endpoint; in the larger RELAX-AHF-2 trial, cardiovascular and all-cause death at 180 days did not differ from placebo.
Sequence & molecular data
| Molecular formula | C256H408N74O74S8 |
|---|---|
| Molecular weight | 5963 g/mol |
| CAS number | 99489-94-8 |
| PubChem CID | 71300755 |
| FDA UNII | W0122B976Y |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
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.
Studies
- Serelaxin, recombinant human relaxin-2, for heart failure patients: A systematic review and meta-analysis
- Effects of Serelaxin in Patients with Acute Heart Failure
- Serelaxin, recombinant human relaxin-2, for treatment of acute heart failure (RELAX-AHF): a randomised, placebo-controlled trial
- Human Recombinant Relaxin (Serelaxin) as Anti-fibrotic Agent: Pharmacology, Limitations and Actual Perspectives
- Serelaxin and acute heart failure
Research statistics
175 PubMed publications · 21.5% human clinical research · 17 registered trials
Counts of published research through 2026-11-01, not evidence that it works. Publications by year, study types and trials · How publications are counted
Regulatory & research status
Serelaxin was withdrawn from the market or rejected for approval. It is not an approved product.
| FDA status | Withdrawn / Rejected |
|---|---|
| Research status | Development discontinued |
| Availability | Research-Only |
| WADA (sport) | Unknown / Not Listed |
| Library classification | Clinical Trial |
How FDA approval, compounding and research-only status differ
Benefits
—
Serelaxin side effects
No side effects listed yet for this entry.
Storage & stability
This compound is not supplied as a powder to be mixed, so the freeze-dried powder and reconstitution handling described for research peptides does not apply. Storage conditions are product-specific: follow the label or packaging of the product itself.
Serelaxin: 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), 2018External reference
- Effects of Serelaxin in Patients with Acute Heart Failure — N Engl J Med, 2019External reference
- Serelaxin, recombinant human relaxin-2, for treatment of acute heart failure (RELAX-AHF): a randomised, placebo-controlled trial — Lancet, 2013External reference
- Human Recombinant Relaxin (Serelaxin) as Anti-fibrotic Agent: Pharmacology, Limitations and Actual Perspectives — Curr Mol Med, 2022External reference
- Serelaxin and acute heart failure — Heart, 2016External reference
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Nov 7, 2026 · Version 2
This Serelaxin profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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