B7-33 10 mg

B7-33 10 mg research-grade lyophilized peptide powder in a glass vial. B7-33 is a synthetic single-chain analog of the B-chain of human Relaxin-2, engineered to selectively activate the Relaxin Family Peptide Receptor 1 (RXFP1) in experimental models of fibrosis, cardiometabolic function and vascular biology.

Research Overview

B7-33 is a functionally selective single-B-chain analog of human Relaxin-2 designed to preferentially signal through RXFP1. In experimental models, it is used to study RXFP1-mediated ERK signaling, extracellular matrix remodeling and organ protection pathways without activating insulin or IGF receptors. Research focuses on anti-fibrotic, cardioprotective and vasoprotective mechanisms in vitro and in vivo.

Primary Research Areas

• RXFP1 receptor signaling: Studies on biased agonism at RXFP1, including ERK1/2 activation and cAMP-independent signaling profiles in relaxin receptor–expressing cells [1].
• Anti-fibrotic & extracellular matrix research: Experimental fibrosis models evaluating modulation of collagen deposition, matrix metalloproteinases and tissue remodeling pathways [1,2].
• Cardiovascular & vascular models: In vitro and in vivo systems investigating vasodilation, endothelial function and cardioprotective signaling under stress conditions [2,3,4].
• Pain from an inflamed paw: mice with a swollen, inflamed hind paw became much less sensitive to touch and heat after B7-33 was injected into a brain ventricle, but only at 30 minutes; the effect faded quickly. It went into the brain, not under the skin [5].
• It did not feed prostate tumours: unlike full relaxin, whose strong cAMP signalling has been tied to tumour-promoting effects, B7-33 did not make prostate tumours grow in the study that introduced it. That is the main reason its designers built it this way; the comparison was in animals [1].
• Scarring in a blocked kidney: mice with one ureter tied off were given B7-33 at 0.25 mg/kg a day for a week. Scar collagen came out thinner and less cross-linked, and the collagen-clearing enzyme MMP-2 rose while its brake TIMP-1 fell. The kidney was injured on purpose, not diseased [6].
• Gone from the blood in minutes: in serum in the laboratory, B7-33 survives only about six minutes, which is why chemists bolted fatty acids onto it and stretched that to sixty. Plain peptide is therefore very short-acting; this was a stability test, not a measurement in an animal [7].
• Swallowed only inside a carrier: stuck to coated iron-oxide nanoparticles and given by mouth every three days, B7-33 outperformed the standard heart drug perindopril at reducing scar in mice with established heart muscle disease. Free peptide was not given orally; the carrier is what got it past the gut [8].

References

1. Hossain MA, Kocan M, Yao ST, et al. A single-chain derivative of the relaxin hormone is a functionally selective agonist of the G protein-coupled receptor, RXFP1. Chem Sci. 2016;7(6):3805-3819. PMID 30155023. doi:10.1039/c5sc04754d
2. Alam F, Gaspari TA, Kemp-Harper BK, et al. 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. Biomed Pharmacother. 2023;160:114370. PMID 36753958. doi:10.1016/j.biopha.2023.114370
3. Marshall SA, O’Sullivan K, Ng HH, et al. B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin). Eur J Pharmacol. 2017;807:190-197. PMID 28478069. doi:10.1016/j.ejphar.2017.05.005
4. Devarakonda T, Mauro AG, Guzman G, et al. B7-33, a Functionally Selective Relaxin Receptor 1 Agonist, Attenuates Myocardial Infarction-Related Adverse Cardiac Remodeling in Mice. J Am Heart Assoc. 2020;9(8):e015748. PMID 32295457. doi:10.1161/JAHA.119.015748
5. Abboud C, Brochoire L, Drouet A, et al. Analgesic effect of central relaxin receptor activation on persistent inflammatory pain in mice: behavioral and neurochemical data. Pain Rep. 2021;6(2):e937. PMID 34159282. doi:10.1097/PR9.0000000000000937
6. Bhuiyan S, Shen M, Chelvaretnam S, et al. Assessment of renal fibrosis and anti-fibrotic agents using a novel diagnostic and stain-free second-harmonic generation platform. FASEB J. 2021;35(5):e21595. PMID 33908676. doi:10.1096/fj.202002053RRR
7. Praveen P, Wang C, Handley TNG, et al. A Lipidated Single-B-Chain Derivative of Relaxin Exhibits Improved In Vitro Serum Stability without Altering Activity. Int J Mol Sci. 2023;24(7). PMID 37047588. doi:10.3390/ijms24076616
8. Somanader-Livera DVN, Wei C, Wang C, et al. Immune cell uptake of glycinated nanoparticles conjugated to anti-fibrotic peptides enables their prolonged activity and oral administration. J Biomed Sci. 2025;32(1):104. PMID 41382190. doi:10.1186/s12929-025-01198-8