B7-33 (Biased RXFP1 Relaxin B-Chain Analogue)

✅ Synthetic 33-aa single-chain relaxin-B-chain analogue
✅ Biased RXFP1 agonist — ERK1/2 anti-fibrotic without cAMP pro-cancer signalling
✅ Hossain/Howe (Florey Institute) 2017 Nat Commun engineered alternative to Serelaxin
✅ Cardiac/kidney/liver/lung fibrosis research; pre-eclampsia models
✅ ~MW 3,800 Da; published 25-50 µg/kg/d SC mouse dosing

B7-33 contains synthetic 33-aa relaxin-B-chain analogue research peptide.

SKU: N/A Κατηγορία: Πεπτίδια Ετικέτα: anti-fibrotic peptide, B7-33, cardiac fibrosis research, relaxin analogue, έρευνα πεπτιδίου, RXFP1 biased agonist

✓ Ιατρικά ελεγμένο από Morgan Ellis — Ερευνητής Φαρμακευτικής · 8 χρόνια εμπειρία · Τελευταία αναθεώρηση: Μάιος 2026

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Quick Answer — What is B7-33?

B7-33 is a synthetic 33-amino-acid single-chain relaxin-B-chain peptide analogue developed by Hossain, Howe and colleagues at the Florey Institute (Melbourne, Australia) and published in Nature Communications (2017). Where native relaxin-2 (the canonical fibrosis-treating hormone, clinically Serelaxin) is a two-chain disulfide-linked A/B-chain peptide that activates both RXFP1 (anti-fibrotic) and RXFP2 (pro-cancer-cell-survival) receptors, B7-33 is a biased RXFP1 agonist — single-chain B-only design that selectively engages RXFP1’s anti-fibrotic signalling (ERK1/2 pathway → MMP-2 upregulation → ECM degradation) while avoiding RXFP1’s pro-cancer cAMP signalling that contributed to Serelaxin’s discontinuation. Published research applications: heart failure, liver / kidney / lung / cardiac fibrosis, pre-eclampsia. For laboratory research use only.

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Προδιαγραφή	Λεπτομέρεια
Compound Class	Synthetic 33-aa single-chain relaxin-B-chain analogue; biased RXFP1 receptor agonist (anti-fibrotic ERK pathway, with reduced cAMP pro-survival signalling)
Chemical Name	B7-33 (relaxin B-chain 7-33 analogue with stabilising modifications; Hossain et al. 2017 Nat Commun)
Αριθμός CAS	Research-grade peptide — no widely-registered single CAS; identification by published sequence and supplier COA
Μοριακός Τύπος	Single-chain 33-residue B-chain analogue — sequence-derived approximate MF C₁₆₄H₂₅₂N₅₀O₄₅S₂; published MW ~3,728 Da (Hossain & Bathgate 2015, J Med Chem).
Sequence Length / MW	33 amino acids derived from H2-relaxin B-chain with N- and C-terminal modifications for solubility / stability; MW ~3,800 Da
Mechanism	Biased RXFP1 agonist. Selectively activates ERK1/2 → MMP-2 / MMP-9 upregulation → collagen-degradation / extracellular-matrix-remodelling pathway (the anti-fibrotic arm of RXFP1 signalling) while showing reduced engagement of cAMP-mediated RXFP1 signalling (the pathway implicated in Serelaxin’s adverse cardiac event signal and the pro-cancer-cell-survival effect that complicated relaxin clinical development).
Form / Purity / Storage	Lyophilized white-to-off-white powder, ≥99% HPLC. Store 2–8 °C short-term, −20 °C long-term (≥36 months). Reconstituted: 2–8 °C, use within 30 days.
Ερευνητική Χρήση	For laboratory research use only. Not on the WADA Prohibited List. Preclinical research compound.

Mechanism of Action — Biased RXFP1 Agonism (ERK without cAMP)

B7-33 was designed by the Hossain / Howe / Bathgate group at the Florey Institute as an answer to the “Serelaxin problem”. Serelaxin (recombinant human relaxin-2) had completed Phase III trials for acute heart failure but failed to gain FDA approval — partly because of mixed cardiovascular safety signals attributed to RXFP1’s dual signalling (anti-fibrotic ERK pathway helpful; cAMP pathway potentially pro-arrhythmic and pro-cancer-cell-survival).

B7-33’s design hypothesis: the relaxin B-chain alone (the chain that mediates RXFP1 binding) can be engineered into a stable single-chain peptide that activates only the ERK1/2 / MMP-upregulation anti-fibrotic arm of RXFP1 signalling while skipping the cAMP-mediated pro-cancer/pro-arrhythmic arm. The published 2017 Nature Communications paper confirmed this: B7-33 produces measurable RXFP1-ERK1/2 activation but minimal cAMP elevation — defined biased agonism. In published mouse models of cardiac fibrosis, kidney fibrosis, and pre-eclampsia, B7-33 produced equivalent or greater anti-fibrotic efficacy compared with native relaxin without the cAMP-mediated complications.

Published Research Applications

RXFP1 biased-agonist pharmacology — canonical example of receptor-pathway biasing in published peptide-engineering literature
Cardiac fibrosis research — ischaemic and hypertensive cardiomyopathy models; collagen-deposition and ECM-remodelling readouts
Kidney / liver / lung fibrosis research — MMP-2/9 upregulation and ECM degradation in chronic fibrotic models
Pre-eclampsia research — published in pregnant-mouse models; relaxin axis is centrally involved in normal-pregnancy haemodynamic adaptation
Heart failure preclinical research — alternative to Serelaxin for clinical-translational research where the biased-signalling profile is more favourable
Acute kidney injury research — RXFP1-mediated renal-tubular protection studies

For broader context see related research peptides: BPC-157 (tissue repair), TB-500 (recovery), GHK-Cu (skin and connective tissue remodelling). Browse the full peptide research catalog.

Available Strengths

Vial Strength	Pack Sizes
2 mg — research-protocol standard for in-vitro RXFP1 pharmacology and short-cycle in-vivo work	10 or 20 vials
10 mg — extended chronic-dosing fibrosis models, multi-cohort sample sizes; lowest per-mg cost	10 or 20 vials

💧 Need BAC water? Reconstituting any lyophilized vial requires sterile bacteriostatic water. Pair this product with our BAC Water (Bacteriostatic Water) — 30 mL multi-dose vial, 0.9% benzyl-alcohol-preserved, USP-grade.

Storage and Reconstitution

Lyophilized 2–8 °C short-term, −20 °C long-term. Reconstitute with bacteriostatic water (1.0 mL per 2 mg vial → 2 mg/mL; 1.0 mL per 10 mg vial → 10 mg/mL). Avoid freeze-thaw.

FAQ

How is B7-33 different from Serelaxin / native relaxin-2?

Native relaxin-2 is a two-chain (A + B) disulfide-linked peptide that activates both pathways downstream of RXFP1 — the anti-fibrotic ERK arm and the cAMP pro-survival arm. Serelaxin is recombinant native relaxin-2; it failed Phase III for acute heart failure partly due to cAMP-pathway adverse signals. B7-33 is a single-chain B-only analogue that selectively engages the anti-fibrotic ERK arm without the cAMP-pathway signal.

Has B7-33 been in clinical trials?

B7-33 remains a preclinical research compound; no formal Phase I/II human clinical trials have been completed to date.

What dose ranges are used in research?

Mouse in-vivo published protocols use 25–50 µg/kg SC daily for 2–4 weeks. Cell-culture in-vitro work uses nanomolar concentrations.

Why order research compounds from MedsBase: Lyophilized HPLC ≥99% peptides & compounds · COA available on request · Discreet temperature-stable packaging · Worldwide courier · Reshipment Assurance on every order · 1,400+ verified κριτικές πελατών

Other Tissue-Repair / Anti-Fibrotic Research Peptides

BPC-157 — Pentadecapeptide tissue-repair research compound
TB-500 — Thymosin Beta-4 fragment, recovery
GHK-Cu — Copper-binding tripeptide, skin / connective tissue remodelling
GLOW Blend — BPC-157 + GHK-Cu + TB-500 stack
Στοίβα Επιθεραπείας Πεπτιδίων — BPC-157 + TB-500 bundle
BAC Water (Bacteriostatic Water) — Required for reconstituting any lyophilized vial — sterile, 0.9% benzyl-alcohol-preserved diluent