Peptide LibraryB7-33
Also known as: Single-chain relaxin-2 analog, RXFP1 agonist peptide
B7-33 (also called Single-chain relaxin-2 analog or RXFP1 agonist peptide) is a relaxin-2 analog in the RXFP1 agonist class. B7-33 is a single-chain minimised analog of human relaxin-2, engineered to retain receptor activity in a much smaller and more synthetically tractable molecule than the two-chain native hormone.
For research use only.
Key Facts
- CAS
- —
- Molecular Weight (MW)
- ~5 kDa
- Half-life
- Short; stabilized vs native relaxin-2
- FDA status
- Not Approved
- Evidence level
- Insufficient Evidence
- Human dose established
- No
- Administration Route
- Not established in humans
- Frequency
- Not established in humans
- Last updated
- Nov 7, 2026
- Reviewed
- Nov 7, 2026
- Targets
- RXFP1 (relaxin family peptide receptor 1)
Vendor price snapshot
Each vendor's price is the median price per mg of its own listings; with fewer than 3 vendors there is no typical range. From public vendor listings collected in Nov 2026, so confirm the live price on the vendor site. Peptide Library does not sell peptides.
- Vendors listing this peptide
- 2
- Listed offers
- 2
- Price per mg
- $8.00/mg
Research summary
Single-chain relaxin-2 analog designed at Monash University as an RXFP1 agonist for anti-fibrotic and vasodilatory research. Preclinical; not FDA-approved.
Research evidence
- Regulatory review (FDA label)None in reviewed sources
- Controlled human trialsNone in reviewed sources
- Early or uncontrolled human studiesNone in reviewed sources
- Lab & animal studies2 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 B7-33 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.
B7-33 dosage: no established human dose
B7-33 has no established human dosage. It is a single-chain peptide based on the B chain of human relaxin-2, and it has only been tested in animals and cells. In mice with drug-induced heart damage it was injected under the skin at 0.25 mg/kg a day for a week.
No established human dosage.
Human clinical evidence: None identified.
Preclinical research: B7-33 was designed to activate the relaxin receptor RXFP1 with a much smaller molecule than relaxin, favouring the ERK pathway over cyclic AMP. It reduced organ fibrosis in rodent heart and lung models and, unlike relaxin, did not promote prostate tumour growth in mice. No human study of B7-33 was found in PubMed or ClinicalTrials.gov, and rodent mg/kg amounts do not convert to a human dose.
Animal dosing is not converted into a human dose anywhere on this page. Where research figures appear below, they are reported as studied, not recommended.
| Human dosing established | No |
|---|---|
| Route | Not established in humans |
| Evidence level | Insufficient Evidence |
| Last reviewed | 2026-11-07 |
Preclinical and analog research
Not human dosing evidence. Listed for completeness and never extrapolated to a human dose.
| Study / context | Population | Dose | Route | Frequency | Duration | Outcome studied | Source |
|---|---|---|---|---|---|---|---|
| Preclinical — B7-33 in isoprenaline-induced cardiomyopathy in mice (2023)Preclinical · Animal study | Adult male mice | 0.25 mg/kg a day (non-human) | Subcutaneous | Daily | Days 7–14 after injury | Less heart fibrosis, inflammation and cardiomyocyte enlargement, similar to relaxin | The single-chain relaxin mimetic, B7-33, maintains the cardioprotective effects of relaxin and more rapidly reduces left ventricular fibrosis compared to perindopril in an experimental model of cardiomyopathy. Biomed Pharmacother. 2023. |
| Preclinical — B7-33 after myocardial ischaemia-reperfusion in mice (2020)Preclinical · Animal and cell study | Adult male mice | Not stated in the indexed abstract for the animals; 50 and 100 nmol/L in isolated heart cells (non-human) | Not stated in the indexed abstract | — | — | Smaller infarct (22% versus 45%) and better preserved heart function than vehicle | B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice. J Am Heart Assoc. 2020. |
Where sources disagree
- B7-33 and serelaxin (recombinant relaxin-2) are different molecules. Serelaxin's human heart-failure trials are not evidence for a B7-33 dose.
Reconstitution
Common research vial sizes: 10 mg.
| Vial | Bacteriostatic water | Concentration | Per 0.01 mL |
|---|---|---|---|
| 10 mg | 2 mL | 5 mg/mL | 50 mcg per 0.01 mL |
These figures are arithmetic only — they convert a vial and a volume into a concentration. They are not a recommendation to take any dose.
Calculate reconstitution & dose →Handling & administration
- Timing Notes
- Studied for anti-fibrotic / vasodilatory effects.
Sequence & molecular data
| Molecular formula | Synthetic single-chain peptide (≈5 kDa) |
|---|---|
| Molecular weight | ~5 kDa |
| Half-life | Short; stabilized vs native relaxin-2 |
| Appearance | White lyophilized powder (research) |
| Formulation | Lyophilized Powder |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
B7-33 is a single-chain minimised analog of human relaxin-2, engineered to retain receptor activity in a much smaller and more synthetically tractable molecule than the two-chain native hormone. It activates RXFP1, a G protein-coupled receptor expressed on vascular smooth muscle, endothelium and fibroblasts. A notable feature reported for B7-33 is biased signalling: it favours the ERK1/2 pathway over the cyclic AMP pathway that native relaxin also engages, which has been proposed to underlie antifibrotic activity with less of the vasodilatory response. In cardiac and renal models this manifests as reduced collagen deposition and matrix remodelling. It is preclinical with no human data.
Origin
Engineered single-chain human relaxin-2 analog.
Targets
Studies
- The single-chain relaxin mimetic, B7-33, maintains the cardioprotective effects of relaxin and more rapidly reduces left ventricular fibrosis compared to perindopril in an experimental model of cardiomyopathy
- B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice
- Coatings Releasing the Relaxin Peptide Analogue B7-33 Reduce Fibrotic Encapsulation
- B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin)
- Single chain peptide agonists of relaxin receptors
Research statistics
12 PubMed publications · 0.0% human clinical research · 0 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
B7-33 is not an FDA-approved product. It is sold for laboratory research and has no approved medical use.
| FDA status | Not Approved |
|---|---|
| Availability | Research-Only |
| WADA (sport) | Unknown / Not Listed |
| Library classification | Research-Only |
How FDA approval, compounding and research-only status differ
Benefits
B7-33 side effects
B7-33 has no controlled human safety data. The effects below are reported, not established, and absence from the list is not evidence of safety.
Side Effects
- No established human dose
- Hypotension theoretical
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
B7-33: frequently asked questions
What is B7-33?
Single-chain relaxin-2 analog designed at Monash University as an RXFP1 agonist for anti-fibrotic and vasodilatory research. Preclinical; not FDA-approved.
How does B7-33 work?
B7-33 is a single-chain minimised analog of human relaxin-2, engineered to retain receptor activity in a much smaller and more synthetically tractable molecule than the two-chain native hormone. It activates RXFP1, a G protein-coupled receptor expressed on vascular smooth muscle, endothelium and fibroblasts.
Is B7-33 FDA approved?
No. B7-33 is investigational: it is in clinical development and has not been approved by the FDA for any indication. Investigational status means trials are ongoing or complete but regulatory review has not resulted in approval, and efficacy and safety are still being established.
What is the half-life of B7-33?
Reported half-life for B7-33 is Short; stabilized vs native relaxin-2. Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.
References
- The single-chain relaxin mimetic, B7-33, maintains the cardioprotective effects of relaxin and more rapidly reduces left ventricular fibrosis compared to perindopril in an experimental model of cardiomyopathy — Biomed Pharmacother, 2023External reference
- B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice — J Am Heart Assoc, 2020External reference
- Coatings Releasing the Relaxin Peptide Analogue B7-33 Reduce Fibrotic Encapsulation — ACS Appl Mater Interfaces, 2019External reference
- B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin) — Eur J Pharmacol, 2017External reference
- Single chain peptide agonists of relaxin receptors — Mol Cell Endocrinol, 2019External reference
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Nov 7, 2026 · Version 3
This B7-33 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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