B7-33
Aliases: B7-33 relaxin mimetic
Last verified: 2026-09-24
The short version
B7-33 is a typical nice idea from academic peptide engineering: isolate just the part of relaxin that does the antifibrotic job. The animal data are neat and consistent. But the context of the relaxin field is instructive: serelaxin, the 'proud' recombinant relaxin with strong preclinical and early clinical story, failed in the large randomized trial for acute heart failure — an effect seen in small studies did not reproduce. B7-33 is a step further removed: nothing human. Buying a B7-33 vial today is buying a 2014 hypothesis.
Identity & type
- Molecular type
- peptide
- Molecular weight
- ~3 kDa
- Origin
- An engineered single-chain peptide based on relaxin's B-chain; related to serelaxin (recombinant relaxin that failed in phase 3).
Mechanism of action
A single-chain relaxin mimetic — an RXFP1 receptor agonist that in animal models of fibrosis and heart activates the cAMP/CREB pathway and reduces TGF-beta1-mediated fibroproliferation; designed to retain the antifibrotic effect without the hypotensive action of full relaxin.
not confirmed in humans
Dosing & routes
Official / clinical context
No official context exists.
Regulator-approved labeling and published study designs — never a recommendation.
Community-reported practice
Very rare in the community; occasionally in 'cardioprotective' stacks by analogy with BPC-157. No reported measurements.
Unverified self-reports. Not medical advice. Not endorsement.
Protocol — official vs community
Official / label
No approved protocol exists — preclinical agent. B7-33 has only animal-model data (fibrosis and cardiac models, µg/kg ranges); no human dose has ever been defined.
Duration: —
It is designed to keep relaxin's antifibrotic effect while dropping its hypotensive action — a design goal demonstrated in animals, not people.
Community (anecdotal)
Structured protocol data for this entry is coming.
Human evidence
None. No registered human trial.
Preclinical evidence
A solid mechanistically coherent series of animal studies — but context matters: the closer relative serelaxin failed in a large phase 3 (RELAX-AHF), showing how far preclinical fibrosis work must travel to become clinical proof.
Known risks
- Everything unknown — no human datatheoretical
- Unverified qualitycharacterized
Teal: characterized in clinical/labeling contexts. Amber: theoretical or reported outside controlled settings.
Unknowns & evidence gaps
- Everything — from pharmacokinetics to effect
Frequently asked questions
References
- B7-33 antifibrotic program — preclinical studies (Monash/Baker institutes)
- RELAX-AHF phase 3 — serelaxin in acute heart failure (negative), context for the relaxin class