B7-33 is a simplified single-chain synthetic peptide derived from the B-chain of human H2 relaxin. Native relaxin features a complicated two-chain structure with multiple disulfide crosslinks, which brings high barriers for chemical synthesis and formulation. B7-33 was engineered to preserve the core RXFP1 receptor binding domain while abandoning the dual-chain architecture, greatly lowering synthetic difficulty for laboratory exploration.

This peptide acts as a functionally biased RXFP1 agonist. It preferentially triggers pERK1/2 and MMP-2 signalling cascades rather than cAMP signalling, separating anti-fibrotic activity from some relaxin-related vascular side effects observed in native relaxin research. It is widely adopted for in vitro and preclinical studies focusing on organ fibrosis, myocardial remodelling, vascular protection and extracellular matrix degradation. Researchers use it to explore scar reduction mechanisms after tissue injury, especially in cardiac and pulmonary fibrosis models.

It is produced via solid-phase peptide synthesis followed by multi-step chromatographic purification and lyophilization. The lyophilized format stabilizes the linear peptide backbone against hydrolysis. B7-33 exhibits relatively short serum half-life in aqueous environment. Once reconstituted, aliquot the solution and avoid repeated freeze-thaw cycles to prevent peptide degradation. Minimize exposure to room temperature and moisture during powder weighing.