B7-33

Also known as (B7-33)H2, single-chain relaxin analog, H2 relaxin B-chain mimetic

A 24-amino-acid single-chain functional analog of H2 relaxin that acts as a biased RXFP1 agonist with anti-fibrotic activity in preclinical models.

Molecular weight2987.75 g/mol

Half-lifeShort — native B7-33 has limited serum stability (minutes); lipidated derivatives were engineered to extend it.

CategoryHealing & Recovery

Typical use cases

✓ Anti-fibrosis research✓ Cardiac fibrosis models✓ Renal/pulmonary fibrosis studies✓ Relaxin/RXFP1 signaling research

Dosing guidelines

StartingNo established human research dose; animal studies dosed by body weight (commonly ~0.1–0.5 mg/kg in rodents).

MaintenanceNot established in humans; community ranges sometimes cite ~100–400 mcg, unvalidated.

Max (studied)Undefined — no human dose-ranging or toxicology data; hedge any figure.

Titration

Typically flat-dosed in the limited literature; no validated titration scheme.

Reconstitution

6 mg vial: ~2 mL bacteriostatic water yields ~3 mg/mL.

Injection sites

Subcutaneous in research handling (e.g. abdomen), rotate sites.

Storage & handling

Lyophilized: stable months cool/dark, longer frozen. Reconstituted: refrigerate (2–8 °C).

Side effects

Unknown human safety profile (preclinical only) Moderate · Rare
Theoretical vasodilation / blood-pressure effects (relaxin class) Moderate · Rare
Injection-site reaction Mild · Uncommon

Research summary

B7-33 is a single-B-chain relaxin mimetic that signals as a biased agonist at the RXFP1 receptor, preferentially activating the ERK1/2–MMP pathway tied to collagen breakdown while largely avoiding the cAMP signaling of native relaxin. Preclinical work reports reduced fibrosis in heart, lung and kidney tissue and cardioprotective effects in animal models, but there are no completed human clinical trials, and native B7-33 has poor serum stability that has prompted lipidated-analog development. Educational only — not medical advice.

Key references

Hossain et al., Chem. Sci. (2016) — a single-chain relaxin derivative is a functionally selective RXFP1 agonist
Marshall et al., Pharmacol. Res. (2017) — B7-33 single-chain relaxin mimetic reduces fibrosis

Related compounds

BPC-157 → TB-500 →

Where to buy

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Educational reference only — not medical advice. Dosing figures are commonly-cited ranges, not prescriptions. Consult a qualified clinician.

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