PeptideCompareB7-33 — EU research guide.
B7-33 is a laboratory-made peptide of 27 amino acids, designed as a shortened single-chain version of human relaxin-2. It has been studied in cells and rodents for anti-fibrotic and cardiovascular effects; no human trial was found.
What is B7-33?
B7-33 is a synthetic peptide of 27 amino acids, designed by a University of Melbourne / Florey Institute group as a shortened, single-chain version of human relaxin-2, which normally consists of two chains linked by disulfide bonds. It comprises residues 7-29 of the relaxin-2 B chain, with two cysteines replaced by serine and four C-terminal residues (KRSL) added. It binds the relaxin receptor RXFP1 with lower affinity than relaxin (reported pKi 5.54) and is described as a functionally selective agonist that preferentially activates the pERK pathway with little cAMP signalling. The authors suggest this bias may explain why it keeps anti-fibrotic activity while avoiding some effects of full relaxin.
What does the research show?
All data found come from cells and animals. No human trial of B7-33 was found, and a 2025 review in Frontiers in Pharmacology likewise reports only preclinical evidence. In the original Chemical Science paper (Hossain et al. 2016), B7-33 was tested in three rodent models (rat myocardial infarction, mouse isoprenaline-induced cardiomyopathy and mouse allergic airways disease) and reduced organ collagen in each; in the cardiomyopathy model interstitial collagen fell by about 51% and total collagen by about 47% (P below 0.01). Unlike relaxin, it did not promote prostate tumour growth in mice. Later mouse and rat studies reported vasoprotective effects (Marshall 2017), reduced adverse remodelling after myocardial infarction (Devarakonda 2020) and a faster reduction of left ventricular fibrosis than the ACE inhibitor perindopril in a 7-day cardiomyopathy model (Alam 2023). Most of this work comes from one collaborating research network, and independent replication was not verified. In vitro, unmodified B7-33 had a half-life of about 6 minutes in human serum at 37 °C (Praveen 2023); no in-vivo half-life was found.
EU legal status
No marketing authorisation for B7-33 was found, and it is not an approved medicine in the EU. The absence of human trials rests on the literature reviewed, because ClinicalTrials.gov and the EMA register could not be queried directly. One vendor's homepage states that its products are sold as research chemicals for in-vitro laboratory use only (the B7-33 product page itself was not seen). B7-33 is not listed by name on the WADA Prohibited List, although the S0 class for non-approved substances may apply (read from a mirror copy of the 2026 list).
Molecular information
Pharmacokinetics
Potency retained over time
Each line is one storage condition: it starts at 100% and falls as potency is lost. Above the dashed 80% line the material is considered reliable — hover for exact values.
⚠ Modelled per compound from molecular structure — chain length, cyclisation, oxidation- and deamidation-prone residues and light sensitivity. Indicative only, not lab-measured per batch.
B7-33 across EU suppliers
COA-verified EU vendors · Updated monthly
References
- Describes the design of B7-33, its biased signalling at RXFP1, three rodent fibrosis models and the absence of prostate tumour promotion in mice. Hossain MA, Kocan M, Yao ST, Royce SG, Nair VB, Siwek C, Patil NA, Harrison IP, Rosengren KJ, Selemidis S, Summers RJ, Wade JD, Bathgate RAD, Samuel CS. 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. DOIPubMed 30155023
- Rat and mouse artery studies in which B7-33 enhanced bradykinin-mediated relaxation and prevented endothelial dysfunction, similar to serelaxin. Marshall SA, O'Sullivan K, Ng HHH, Bathgate RAD, Parry LJ, Hossain MA, Leo CH. B7-33 replicates the vasoprotective functions of human relaxin-2 (serelaxin). Eur J Pharmacol 2017;807:190-197. DOIPubMed 28478069
- Mouse myocardial infarction study reporting reduced adverse cardiac remodelling (title and authors confirmed; abstract, volume and pages were not read). 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. DOIPubMed 32295457
- Mouse cardiomyopathy model in which B7-33 and relaxin reduced fibrosis, inflammation and hypertrophy, with a faster anti-fibrotic effect than perindopril within 7 days. Alam F, Gaspari TA, Kemp-Harper BK, Low E, Aw A, Ferens D, Spizzo I, Jefferis AM, Praveen P, Widdop RE, Bathgate RAD, Hossain MA, Samuel CS. 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. DOIPubMed 36753958
- In-vitro study giving a human serum half-life of about 6 minutes for unmodified B7-33 and about 60 minutes for a lipidated derivative. Praveen P, Wang C, Handley TNG, Wu H, Samuel CS, Bathgate RAD, Hossain MA. A lipidated single-B-chain derivative of relaxin exhibits improved in vitro serum stability without altering activity. Int J Mol Sci 2023;24(7):6616. DOIPubMed 37047588