B7-33
Also known as: B7-33
B7-33 is a single-chain peptide analog of the hormone relaxin-2, engineered to retain its anti-fibrotic and vasodilatory actions while resisting rapid breakdown. It is studied chiefly for reducing scar tissue (fibrosis) in heart, lung, and kidney models.
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Mechanism of Action
B7-33 is a structurally simplified, single B-chain mimetic of human relaxin-2 that signals through the relaxin family peptide receptor 1 (RXFP1). Unlike native relaxin, it biases signaling toward the ERK1/2 pathway rather than cAMP accumulation, which preserves anti-fibrotic effects while limiting tumorigenic cAMP-driven proliferation. Activation of RXFP1 increases matrix metalloproteinase-2 (MMP-2) expression and reduces TGF-beta-driven collagen deposition by myofibroblasts. Downstream nitric oxide release contributes to its vasodilatory and tissue-protective profile.
- Half-life
- Estimated short (minutes to a few hours); engineered for improved stability over native relaxin
- Administration Routes
- subcutaneous
- Research Status
- Preclinical
Reported Benefits
- Reduces organ fibrosis (cardiac, renal, pulmonary) in animal models
- Promotes vasodilation and improved tissue perfusion
- Downregulates TGF-beta-driven collagen accumulation
- Upregulates collagen-degrading MMP-2 activity
- Investigated for protection against preeclampsia-related vascular dysfunction
- Smaller, more synthetically accessible than full-length relaxin
Potential Side Effects
- Possible hypotension from vasodilation
- Injection-site irritation or redness
- Reflex tachycardia in some animal models
- Largely uncharacterized human safety profile
Common Dosing
For research use only and not medical advice: animal studies have used roughly 25-500 mcg/kg administered subcutaneously; no validated human dosing exists.
The dosing information above is aggregated from research literature and anecdotal community reports for educational purposes only. It is not a recommendation, prescription, or medical advice. Peptides are sold as research chemicals only and are not intended for human use.
Contraindications
- Pregnancy and breastfeeding due to hormonal and vascular activity
- Pre-existing hypotension or significant cardiovascular disease
- Concurrent vasodilator or antihypertensive therapy without oversight
Human Relaxin-2
Human Relaxin-2 is a peptide hormone with vasodilatory and anti-fibrotic properties, also developed clinically as serelaxin. It is studied for cardiovascular and tissue-remodeling research.
BPC-157
A synthetic peptide fragment derived from a protein found in gastric juice, studied for its broad tissue-healing and cytoprotective effects. Popular in research for tendon, ligament, muscle, and gut repair.
TB-500 Fragment (1-4)
TB-500 Fragment 1-4 is the N-terminal tetrapeptide (Ac-SDKP) of thymosin beta-4, studied for anti-fibrotic and tissue-protective effects. This fragment is distinct from the actin-binding region and is associated with regulation of fibrosis and inflammation.
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A single-chain derivative of the relaxin hormone is a functionally selective agonist of the G protein-coupled receptor, RXFP1
2016
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B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin)
2017
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B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice
2020
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The single-chain relaxin mimetic, B7-33, maintains the cardioprotective effects of relaxin and more rapidly reduces left ventricular fibrosis compared to perindopril in an experimental model of cardiomyopathy
2023