Cardiovascular & General; Hormonal & Sexual Health / Cardiovascular
Relaxin
Relaxin is best known as the hormone of pregnancy that loosens connective tissue, but its cardiovascular behaviour is what earns it a record here: it widens blood vessels through nitric oxide and prostacyclin, and in animals it reduces the scarring that stiffens a failing heart and kidney. A manufactured version, serelaxin, was given as a 48-hour drip to patients admitted with acute heart failure, and an earlier Phase 3 trial returned a positive result that an entire development programme was then built on. The confirmatory trial did not reproduce it. RELAX-AHF-2 randomised 6,545 patients and found cardiovascular death at 180 days at 8.7% against 8.9% on placebo, no difference in worsening heart failure, and no regulator has approved it.
Last updated
Mechanism
Binds the RXFP1 receptor on vascular, cardiac, and renal cells, driving nitric-oxide and prostacyclin vasodilation and anti-fibrotic signalling.
Reported effects
What sources associate with this compound. Reported categories, not outcomes we have graded — each would need its own citation and rung.
- Vasodilation research
- Acute heart failure trials
- Cardiac fibrosis research
Dosing on file unverified
48h IV infusion: 10, 30, 100, 250 µg/kg/day; Phase 3: 30 µg/kg/day; 48-h IV infusion: 10, 30, 100, or 250 µg/kg/day
Carried from a source that labels it unverified, and reproduced with that label attached. A record of what is reported, not a recommendation. No citation on this page establishes it.
Half-life, storage & sport
- Elimination half-life
- 4.6 h (human, IV) — study. Cardiovascular research 2025; healthy human subjects.
The half-life on file is 4.6 h, measured intravenously. On the schedule this record states — daily — each dose has fallen to 2.7% of its own peak by the time the next is given. Nothing accumulates, and there is no loading phase to run.
The rise is not modelled and the axis is not a blood level. No absorption rate constant and no volume of distribution are on file, so each dose appears at full height the instant it is given, and the axis is percent of this compound's own peak.
Literature on file 10
-
animal in vivo
Spray-Dried Formulations of Relaxin-H2 for Inhalation. graded on: an animal model — read from the indexed abstract — “rats”
-
animal in vivo
Relaxin inhibits renal interstitial fibrosis and promotes fatty acid metabolism after UUO via the AMPK/PGC1α signaling pathway. graded on: an animal model — read from the indexed abstract — “mice”
-
human observational
Association of Relaxin-1 Levels with Mortality in Sepsis and Septic Shock. graded on: an observational human design — read from the indexed abstract — “observational”
-
animal in vivo
Development of a long-acting relaxin for the treatment of pulmonary hypertension. graded on: an animal model — read from the indexed abstract — “rats”
-
in vitro
Identification and functional characterisation of the relaxin-like gonad-stimulating peptide receptor in sea cucumbers. graded on: cell-based receptor activation assays with sequence analysis and structural modelling — read from the abstract — “abstract review”
Not graded
5 citations whose study design could not be read from the title. Left ungraded rather than guessed at.
-
not graded
NCT00520806: A Phase II/III, Multicenter, Randomized, Double-blind, Placebo-Controlled Study to Evaluate the Efficacy and Safety of Relaxin in Subjects With Acute Heart Failure graded on: NCT00520806 is completed and has posted no results - a registration, not a reported outcome — “NCT00520806”
-
not graded
NCT00704665: A Randomized, Double-Blind, Placebo-Controlled Trial of Recombinant Human Relaxin in the Treatment of Systemic Sclerosis With Diffuse Scleroderma graded on: NCT00704665 is completed and has posted no results - a registration, not a reported outcome — “NCT00704665”
-
not graded
NCT00004380: Phase II Study of Recombinant Relaxin for Progressive Systemic Sclerosis graded on: NCT00004380 is completed and has posted no results - a registration, not a reported outcome — “NCT00004380”
-
not graded
NCT00259116: A Pilot Safety and Dose-Finding Trial of Intravenous Recombinant Human Relaxin (rhRlx) in Compensated Congestive Heart Failure graded on: NCT00259116 is completed and has posted no results - a registration, not a reported outcome — “NCT00259116”
-
not graded
NCT07359872: Relaxin Therapy for Atrial Fibrillation graded on: NCT07359872 is not yet recruiting and has posted no results - a registration, not a reported outcome — “NCT07359872”
Identity
- UniProt
- P04808 (RLN2)
Caveat on these identifiers
P04808 is prorelaxin H1 (RLN1); the main circulating human relaxin is relaxin-2 (P04090).
Notes unverified prose
Phase 2/3 (RELAX-AHF, Pre-RELAX-AHF); Phase 2/3 (RELAX-AHF); See Hormonal & Sexual Health
Not on file 8
8 of the 8 fields we track hold nothing on this record, and each says why. A blank field is a bug; a named absence is a finding.
- molecular weightnothing we hold supplies it
- molecular formulanothing we hold supplies it
- CAS registry numbernothing we hold supplies it
- PubChem identifiernothing we hold supplies it
- amino-acid sequencenothing we hold supplies it
- SMILES stringnothing we hold supplies it
- InChInothing we hold supplies it
- InChI keynothing we hold supplies it
Each field links to every other record missing the same thing. The full ledger holds 765 gaps across 163 records.
Listed prices 2
What 2 shops we track listed for Relaxin, read from their own public catalogues on 2026-09-14. We take no commission on these and they are not ranked by any payment — how vendors are scored.
Compare prices2 listings from 2 shops
| Vendor | Size | Price | Per mg |
|---|---|---|---|
| Peptides Warehouse | 10 mg | $38.59 USD | $3.86/mg |
| USA Peptide Sciences | 6 mg | $70.00 USD | $11.67/mg |
None of these shops lists your destination. Choose “Show all” to see every listing we hold.
Prices are the vendor's own listing, reproduced with the date we read it — never converted between currencies, and compared per milligram only where the vendor states the vial size.