What's on the label is the measured result — net peptide mass, not gross powder weight, plus RP-HPLC purity, on a lot-numbered COA for every batch.
Net peptide mass and RP-HPLC purity — a lot-numbered COA for every batch.
Net peptide mass + HPLC purity, per lot.
PCAC will review 7 peptides for the 503A bulks list, BPC-157, KPV, TB-500, MOTS-c, Emideltide, Semax, Epitalon. Read our briefing →
PCAC will review 7 peptides for the 503A bulks list. Read →
FDA PCAC reviews 7 peptides in July. Read →
Single-chain relaxin analog · RXFP1 agonist
PeptideXpo buyer fit
This PeptideXpo page is intentionally positioned for distributors, OEM buyers, and procurement teams comparing B7-33 inside a wider peptide catalog. It is not trying to be the deepest single-molecule monograph; the differentiated intent is assortment planning, export-ready documentation, fill-size comparison, and whether this SKU belongs in a broader buyer program.
Overview
B7-33 is a 27-amino-acid single-chain peptide analog of native relaxin-2 (H2-relaxin), engineered to retain the RXFP1 receptor agonism of the parent two-chain relaxin while being synthesizable as a simple single-chain peptide rather than the disulfide-bonded heterodimer of native relaxin. The molecule is a biased RXFP1 agonist, preferentially activating the ERK1/2 pathway downstream of RXFP1 while showing reduced activation of the cAMP pathway, a pharmacological profile that the developing group hypothesized would produce the anti-fibrotic and tissue-remodeling effects of relaxin without the dose-limiting cardiovascular effects associated with full-agonism dosing. PeptideXpo supplies B7-33 as a lyophilized 27-residue peptide at ≥99.0% HPLC purity. As a single-chain linear peptide (no disulfide bridges), B7-33 is significantly easier to synthesize than the native disulfide-bonded relaxin heterodimer, this is the practical advantage of the biased-agonist design beyond the pharmacology. The analytical packet covers peak-integration HPLC, mass spec, and sequence verification on request. Two fill sizes (2 mg and 10 mg) cover typical research workflows in fibrosis, cardiovascular, and tissue-remodeling research models.
Who buys this, and why
Repair peptides, BPC-157, TB-500, and related sequences, typically ship to research labs studying tissue-repair, gastrointestinal, or tendon-ligament models, and to compounding pharmacies that have validated the bulk active into their workflow. The synthesis itself is reliable, but analytical confirmation is where suppliers differ, buyers qualifying a new source should request sequence verification by tandem MS on the first batch and compare against the labelled sequence directly.
Primary buyer fit: academic and contract research laboratories.
Specifications
Documentation available on request
Regulatory note
Sold for research and commercial use under the buyer's local regulations. Not a finished dosage form and not labeled for human administration as shipped. Repair-class peptides are not approved drug products in most jurisdictions and should be handled accordingly in research, manufacturing, and reporting.
Frequently asked questions
Receptor signaling biology in the last decade has recognized that G-protein-coupled receptors (GPCRs) can engage multiple downstream signaling cascades, primarily G-protein-pathway and β-arrestin-pathway routes, and that different ligands can preferentially activate one cascade over the other. A 'biased' agonist is one that activates one downstream pathway more strongly than others. B7-33 is described as a biased RXFP1 agonist because it preferentially activates the ERK1/2 phosphorylation cascade (the pathway hypothesized to drive the anti-fibrotic and tissue-remodeling effects of relaxin) while showing reduced activation of the cAMP pathway (which contributes to relaxin's cardiovascular effects). The biased-agonist design strategy is intended to dissociate the desired therapeutic effects from the dose-limiting side effects.
Native human relaxin-2 (H2-relaxin) is a 53-amino-acid heterodimer with two chains connected by two interchain disulfide bonds plus one intrachain disulfide on the A-chain. Synthesizing the native molecule by SPPS requires synthesizing each chain separately, then performing controlled oxidative folding to form the three disulfide bonds in the correct regiochemistry, a process that produces 5-15% yield of the correctly-folded product against a background of scrambled disulfide isomers. B7-33 is a single 27-residue linear peptide with no disulfide bonds, synthesizable by routine SPPS at 50-80% yield. The simplification makes B7-33 substantially more accessible at research and commercial scale than native relaxin while preserving the RXFP1-agonism that drives the biological readouts of interest.
