Also known as Single-chain relaxin · relaxin B7-33
A 27-residue single-chain relaxin-2 analog and selective RXFP1 agonist — a simplified relaxin mimetic studied for anti-fibrotic effects.
Research refreshed
B7-33 is a single-chain peptide derived from the B-chain of human relaxin-2, the hormone best known for remodeling connective tissue in pregnancy. Native relaxin is a complex two-chain, disulfide-linked hormone that is hard to make; B7-33 strips it down to a single 27-residue chain that still activates relaxin’s main receptor, RXFP1. Its research interest is anti-fibrotic: like relaxin, it has reduced or reversed scarring (fibrosis) in preclinical heart and lung models, but as a far simpler, more manufacturable molecule.
B7-33 is an exercise in simplification. Human relaxin-2 is a powerful anti-fibrotic hormone, but it is a two-chain, disulfide-linked protein — expensive and difficult to produce, which has long limited its therapeutic use. Researchers at the Florey Institute engineered B7-33 as a minimal single-chain version: a 27-residue peptide based on relaxin’s B-chain that dispenses with the second chain while still switching on the relaxin receptor RXFP1.
What makes it notable is that the simplification did not cost the biology. In preclinical rodent models of heart and lung disease, B7-33 prevented or reversed fibrosis with potency similar to native relaxin, apparently through a functionally selective signal (via RXFP1–AT2 receptor complexes) that favors the collagen-degrading enzyme MMP-2. That combination — relaxin-like anti-fibrotic activity in a small, synthesizable peptide — is why it draws interest as a research compound. It is not FDA-approved.
Functionally selective agonist of the relaxin receptor RXFP1 — signaling (in part via RXFP1–angiotensin II type-2 receptor heterodimers) toward pERK1/2 and the collagen-degrading enzyme MMP-2, driving anti-fibrotic remodeling.
Behind every vial of B7-33 is the same exacting pipeline every research peptide runs — but the chemistry plays out differently for this molecule. Here is how B7-33, specifically, is brought into being.
B7-33 begins not as a powder but as a specification. Before a single bond is made, the target sequence, salt form, and purity threshold are written down as the contract the finished material must meet.
B7-33 is assembled by solid-phase peptide synthesis — the chain grows one protected residue at a time on resin, and what you fail to build cleanly here you pay to remove later. It also carries a disulfide bridge, an extra step beyond a plain chain that adds both capability and cost.
The crude mixture — B7-33 plus its deletions and side products — is then separated on preparative HPLC, and where the cut is taken decides the difference between a genuinely pure peptide and a barely-passable one.
A real batch of B7-33 proves itself: identity confirmed by mass spectrometry, purity read directly off an analytical HPLC trace, water and counterion content measured. That batch-specific certificate of analysis is the only honest way to know what is actually in a vial of B7-33 — and a short, cold, accountable chain of custody is how that purity survives the trip to your bench.
B7-33 is a 27-residue single-chain analog of the relaxin-2 B-chain — a deliberate simplification of native relaxin’s two-chain, disulfide-linked structure that makes it a practical linear solid-phase peptide. Coupling efficiency and deletion-sequence removal over its length are the main quality considerations.
Don't judge a vial by its cake. A fluffy, good-looking lyophilized powder reflects bulking agents and freeze-drying parameters — not purity. Insist on a batch-specific certificate of analysis.
B7-33 is a 27-residue single-chain analog of the relaxin-2 B-chain that activates the relaxin receptor RXFP1, studied as a simplified, anti-fibrotic relaxin mimetic.
Native relaxin-2 is a two-chain, disulfide-linked protein that is hard to make; B7-33 is a single 27-residue chain that still activates RXFP1, so it is far simpler to synthesize.
Chiefly fibrosis — it reduced or reversed scarring in preclinical heart and lung models — along with broader tissue-remodeling research.
No — it is an investigational research compound, not FDA-approved. This page is a research and educational reference.
Dosing protocols, mechanism, comparisons, and the latest trials — citation-backed answers grounded in PubMed, PubChem, and ClinicalTrials.gov.