B7-33

B7-33 is a 24-amino-acid single-chain peptide derived from human relaxin-2, designed by researchers at the Florey Institute and Monash University as a simplified, more stable mimic of the full relaxin hormone. Native relaxin is a two-chain hormone with disulfide bonds — difficult and expensive to manufacture. B7-33 keeps the relaxin-receptor-binding 'business end' while eliminating the structural complexity, making it a practical research tool for studying anti-fibrotic and cardiovascular effects of relaxin signaling. It is sold strictly for laboratory research.

Relaxin is a hormone best known for loosening ligaments during pregnancy, but it also has powerful effects on the heart, blood vessels, and scar tissue (fibrosis). Drug companies have tried to develop relaxin therapies for heart failure for years; serelaxin was one such drug. B7-33 is a smaller, simpler version of relaxin that researchers use to study the same biology more easily. The hottest research direction is anti-fibrotic: stopping or reversing scar tissue in heart, lung, and kidney models.

B7-33 binds and activates the relaxin family peptide receptor 1 (RXFP1) — the same receptor activated by native relaxin. Activation of RXFP1 triggers signaling that suppresses TGF-β-driven fibroblast-to-myofibroblast transition, reduces collagen deposition, and promotes vasodilation through nitric oxide. The net effect in animal models is reduced scar tissue formation and improved cardiac function after injury.

• •Cardiac fibrosis after infarction
• •Pulmonary fibrosis models
• •Renal fibrosis and chronic kidney disease
• •Vasodilation and blood pressure research
• •RXFP1 receptor pharmacology

B7-33 is a relatively new arrival on research-peptide forums and has more attention from longevity researchers than bodybuilders. Threads tend to focus on its anti-fibrotic potential — a frequent topic among people interested in heart and organ aging — and how it compares to serelaxin's mixed clinical history. It is far less mainstream than BPC-157 or TB-500.

“Relaxin's compact anti-scar version.”

B7-33 is sometimes discussed alongside BPC-157 in tissue-repair-focused protocols (BPC-157 for soft-tissue repair, B7-33 for the anti-fibrotic angle). Pairings are speculative and not based on published combination data.

B7-33 is a 24-amino-acid single-chain mimic of human relaxin-2 designed for easier manufacturing while preserving anti-fibrotic and vasodilatory activity. It is studied for cardiac, pulmonary, and renal fibrosis and is sold for laboratory research only.