B7-33 (Relaxin)
Relaxin-2 Analog | Anti-Fibrotic & Cardiovascular
Community Research
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B7-33 is a single-chain peptide analog of human relaxin-2 that selectively activates the relaxin family peptide receptor 1 (RXFP1). Unlike native relaxin-2, which requires a complex two-chain A/B structure connected by disulfide bonds, B7-33 achieves RXFP1 activation with a much simpler single-chain design. This makes it significantly easier and more cost-effective to synthesize. Preclinical research demonstrates potent anti-fibrotic, vasodilatory, and cardioprotective properties, positioning B7-33 as a promising therapeutic candidate for fibrotic diseases, heart failure, and vascular dysfunction.
Selectively activates RXFP1, the primary receptor for relaxin-2, triggering downstream signaling cascades that inhibit fibroblast activation and collagen deposition, promote extracellular matrix remodeling via increased matrix metalloproteinase (MMP) activity, enhance nitric oxide-mediated vasodilation, and reduce inflammatory cytokine expression. B7-33 appears to preferentially engage pERK1/2 signaling pathways while showing reduced cAMP activation compared to native relaxin-2, suggesting biased agonism at RXFP1.
Molecular Data
Single-chain analog of relaxin-2 B-chain Complex or non-standard sequence format
Research Indications
Reduces myocardial fibrosis and collagen deposition, attenuating adverse cardiac remodeling in preclinical heart failure models.
Enhances nitric oxide-mediated vasodilation, reducing vascular resistance and improving blood flow in preclinical studies.
Demonstrates cardioprotective effects in animal models of heart failure, improving cardiac function and reducing fibrotic burden.
Inhibits fibroblast differentiation into myofibroblasts and reduces extracellular matrix deposition in multiple organ systems.
Shows protective effects against kidney fibrosis progression in preclinical disease models.
Dosing Protocols
Subcutaneous injection is the primary route studied in preclinical research. Dosing protocols are based on animal model data and have not been validated in human trials.
| Goal | Dose | Frequency | Route |
|---|---|---|---|
| Anti-fibrotic / Cardiovascular support | 100-250 mcg | 1x daily | SubQ |
Reconstitution Instructions
- Bacteriostatic water (BAC)
- Insulin syringes (0.5-1 mL)
- Alcohol swabs
- Peptide vial
- Sterile work surface
- 1 Clean work area and hands thoroughly
- 2 Calculate required BAC water volume using calculator
- 3 Draw BAC water into syringe
- 4 Inject slowly down vial side (not directly onto powder)
- 5 Gently swirl until dissolved (never shake)
- 6 Store in refrigerator, use within 28 days
Interactions
What to Expect
Side Effects & Safety
Common Side Effects
- Injection site reactions (redness, mild irritation)
- Potential transient hypotension due to vasodilatory effects
Stop Signs - Discontinue if:
- Persistent or symptomatic hypotension (dizziness, lightheadedness, fainting)
- Severe injection site reactions or signs of infection
- Allergic reactions (rash, swelling, difficulty breathing)
Contraindications
- Pre-existing hypotension or conditions exacerbated by vasodilation
- Pregnancy or breastfeeding (no safety data available)
- Concurrent use of potent antihypertensive agents without medical supervision
- No human safety data exists -- all protocols are extrapolated from preclinical research
Quality Checklist
Good Signs
- White to off-white lyophilized powder
- Clear solution after reconstitution with no particles
- Intact vacuum seal on vial
Warning Signs
- Slight clumping that dissolves with gentle swirling (may occur from shipping)
Bad Signs
- Discolored or wet powder indicating degradation
- Cloudy solution, visible particles, or precipitates after reconstitution
- Broken or missing vacuum seal
References
- A single-chain peptide derived from the relaxin B-chain selectively activates RXFP1Hossain, M.A., et al.Chemical Science (2016)
Identified B7-33 as a single-chain relaxin analog that selectively activates RXFP1, demonstrating that a simplified single-chain peptide can replicate key signaling functions of native two-chain relaxin-2.
- The single-chain relaxin mimetic, B7-33, maintains anti-fibrotic activity in liver and kidney fibrosis modelsHossain, M.A., et al.British Journal of Pharmacology (2020)
B7-33 reduced fibrosis markers in both liver and kidney fibrosis models, demonstrating organ-protective anti-fibrotic effects comparable to native relaxin-2 despite its simplified structure.
- The relaxin receptor as a therapeutic target -- perspectives from evolution and drug targetingBathgate, R.A.D., et al.Pharmacology & Therapeutics (2018)
Comprehensive review of RXFP1 as a drug target, discussing relaxin-2 and analogs including B7-33 for cardiovascular, fibrotic, and reproductive indications.
- B7-33 replicates the vasoprotective effects of relaxin in mouse models of cardiovascular diseaseMarshall, S.A., et al.Annals of the New York Academy of Sciences (2017)
B7-33 replicated the vasoprotective and anti-fibrotic effects of native relaxin in mouse models, reducing vascular stiffness and improving cardiovascular outcomes.
- The role of relaxin and its receptor (RXFP1) in the pathogenesis and treatment of fibrotic diseasesSamuel, C.S., et al.Molecular and Cellular Endocrinology (2017)
Reviews the anti-fibrotic mechanisms of relaxin/RXFP1 signaling, including inhibition of TGF-beta-driven fibroblast activation and collagen synthesis, with implications for simplified analogs like B7-33.
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Disclaimer
This information is for educational and research purposes only. Consult a healthcare professional before use.