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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| Specyfikacja | Szczegóły |
|---|---|
| Klasa związku | Synthetic 33-aa single-chain relaxin-B-chain analogue; biased RXFP1 receptor agonist (anti-fibrotic ERK pathway, with reduced cAMP pro-survival signalling) |
| Nazwa chemiczna | B7-33 (relaxin B-chain 7-33 analogue with stabilising modifications; Hossain et al. 2017 Nat Commun) |
| Numer CAS | Research-grade peptide — no widely-registered single CAS; identification by published sequence and supplier COA |
| Wzór cząsteczkowy | 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 |
| Mechanizm | 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. |
| Do celów badawczych | 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.
Opublikowane zastosowania badawcze
- 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
| Mocowanie fiolki | Rozmiary opakowań |
|---|---|
| 2 mg — research-protocol standard for in-vitro RXFP1 pharmacology and short-cycle in-vivo work | 10 lub 20 fiolek |
| 10 mg — extended chronic-dosing fibrosis models, multi-cohort sample sizes; lowest per-mg cost | 10 lub 20 fiolek |
Przechowywanie i rekonstytucja
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.
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
- Mieszanka GLOW — BPC-157 + GHK-Cu + TB-500 stack
- Peptydowy zestaw regeneracyjny — BPC-157 + TB-500 bundle
- BAC Water (Woda bakteriostatyczna) — Wymagany do rekonstytucji każdej liofilizowanej fiolki — sterylny rozcieńczalnik z 0,9% benzylowym alkoholem jako środkiem konserwującym
























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