BQ-123
Also known as: BQ 123, BQ‑123, Cyclo(-Asp-Pro-Phe-Leu-Leu-Arg-), cyclo(D-Asp-Pro-D-Val-Leu-D-Trp), Endothelin-A receptor antagonist BQ-123
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Summary
BQ-123 is a cyclic pentapeptide that selectively blocks endothelin‑A (ET_A) receptors. It is used primarily as a research tool to probe the role of endothelin‑1 in vascular tone, cardiac remodeling, and pregnancy‑related hypertension. The compound is administered intravenously or intracoronarily in experimental settings and has not received regulatory approval for therapeutic use.
Mechanism of Action
BQ-123 binds with high affinity to the ET_A receptor, preventing endothelin‑1 from activating the receptor’s G‑protein coupled signaling cascade. This inhibition reduces phosphoinositide hydrolysis, intracellular Ca²⁺ transients, and downstream protein kinase C activation, thereby attenuating vasoconstriction and positive inotropic effects that are mediated by ET‑1 in vascular smooth muscle and cardiac myocytes.
What the Research Shows
Pre‑clinical studies have shown that BQ-123 shifts endothelin‑1 concentration‑response curves to the right in isolated human resistance arteries, lowering maximal contractile force, especially in omental vessels from preeclamptic women. In rabbit ventricular myocardium, the peptide selectively blocks the ET_A1 subtype linked to ET‑3‑induced inotropy, implicating distinct ET_A subtypes. Review articles cite BQ-123 as a key pharmacological probe that helped define ET‑1’s contribution to cardiac hypertrophy, heart failure, and vascular pathology, though no human clinical trials have been reported. The peptide’s rapid plasma degradation and short half‑life limit its translational use.
Reported Benefits
Experimental data indicate that BQ-123 can specifically antagonize ET_A‑mediated vasoconstriction, providing a clearer understanding of endothelin’s role in hypertension, preeclampsia, and cardiac remodeling. In animal models, selective ET_A blockade has been suggested to improve outcomes in heart failure and myocardial injury, supporting its value as a research tool for developing more durable non‑peptide ET_A antagonists.
Limitations of the Evidence
The peptide is rapidly degraded by gastric enzymes and has a short plasma half‑life, restricting its use to intravenous or intracoronary administration in laboratory settings. No human safety or efficacy data exist, and its therapeutic potential remains speculative. Animal studies show mixed results, with some models indicating benefit and others showing no effect or possible adverse actions, underscoring the need for further investigation.
Safety Considerations
Human safety information for BQ-123 is not available; the compound is confined to experimental use. Potential risks include hypotension from abrupt ET_A blockade, but such effects have only been observed in isolated tissue studies. The short half‑life may limit systemic exposure, yet the lack of clinical data precludes definitive safety conclusions.
How It Is Administered
BQ-123 is administered as an aqueous solution via intravenous infusion or direct intracoronary injection in pre‑clinical and ex‑vivo experiments. Formulations are typically peptide solutions prepared under sterile conditions for short‑term use.
Routes of Administration
Goals & Uses
- Model hypertension mechanismsResearchModerate
- Hypertension researchCardiovascularModerate
- Pulmonary arterial hypertension (PAH) researchCardiovascularModerate
- Heart failure hemodynamic researchCardiovascularModerate
- Raynaud's phenomenon / peripheral vascular diseaseVascularLow
- Study endothelin‑A receptor functionResearchHigh
- Renal vascular physiologyRenalLow
Contraindications
- PregnancyPopulationHighPotential fetal risk or insufficient safety data
- Hypersensitivity to BQ-123 or peptide excipientsAllergic/ImmunologicHigh
- Severe hypotensionCardiovascularHigh
Adverse Effects
- Vasodilation / flushingCardiovascularCommon
- Injection site reactionsLocalUncommon
- HeadacheNeurologicUncommonPain in the head or upper neck
- HypotensionCardiovascularUnknownLow blood pressure
Drug Interactions
- Antihypertensive agentsModerate
- Endothelin-B (ETB) antagonistsModerate
- Phosphodiesterase-5 (PDE5) inhibitorsModerate
Population Constraints
- Pediatric populationsAgeRelative
- Patients with severe hepatic impairmentHepaticRelative
- Pregnant womenReproductiveAbsolute
Regulatory Status
- European UnionUnapprovedNot authorized for clinical use
- United StatesUnapprovedInvestigational reagent only
- United KingdomUnapprovedResearch chemical
Not approved for human therapeutic use; employed only in experimental and preclinical settings.
Evidence & Sources
- Journal ArticleModerateBayes M, Rabasseda X, Prous JR2002-01-01T00:00:00.000000Z
- Journal ArticleModerateRehsia NS, Dhalla NS2010-01-01T00:00:00.000000Z
- Journal ArticleModerateHoude M, Labonté J, D'Orléans-Juste P2011-01-01T00:00:00.000000Z
- Journal ArticleModerateDoggrell SA2002-01-01T00:00:00.000000Z
- Journal ArticleModerateWolff K, et al.1996-01-01T00:00:00.000000Z
- Journal ArticleModerateEndoh M, et al.1998-01-01T00:00:00.000000Z
Frequently Asked Questions
Is BQ-123 an approved drug for treating heart disease?
No. BQ-123 is a research‑grade peptide used to study endothelin‑A receptor function and has not been approved by regulatory agencies for any therapeutic indication.
How does BQ-123 differ from non‑peptide endothelin antagonists like bosentan?
BQ-123 is a selective ET_A receptor antagonist with a peptide backbone, requiring intravenous delivery and having a short half‑life, whereas bosentan is a non‑peptide, orally active, non‑selective ET receptor blocker used clinically for pulmonary hypertension.
Can BQ-123 be used to treat preeclampsia in patients?
Evidence is limited to ex‑vivo studies showing reduced endothelin‑1‑induced contraction in isolated vessels; there are no clinical trials or safety data to support its use in patients with preeclampsia.
What are the main challenges in developing BQ-123 as a drug?
Key challenges include rapid enzymatic degradation, short systemic half‑life, the need for parenteral administration, and the absence of human safety and efficacy data, all of which limit its translation from bench to bedside.
What experimental models have employed BQ-123?
BQ-123 has been used in isolated human resistance arteries, rabbit ventricular myocardium preparations, and various animal models of cardiac injury and hypertension to elucidate endothelin‑A receptor–mediated signaling.
What is BQ-123?
BQ-123 is a cyclic pentapeptide that selectively blocks endothelin‑A (ET_A) receptors. It is used primarily as a research tool to probe the role of endothelin‑1 in vascular tone, cardiac remodeling, and pregnancy‑related hypertension. The compound is administered intravenously or intracoronarily in experimental settings and has not received regulatory approval for therapeutic use.
What is BQ-123 used for?
BQ-123 is educationally associated with: Model hypertension mechanisms, Hypertension research, Pulmonary arterial hypertension (PAH) research, Heart failure hemodynamic research, Raynaud's phenomenon / peripheral vascular disease, Study endothelin‑A receptor function, Renal vascular physiology. Educational only — not medical advice.
How is BQ-123 administered?
Recorded routes of administration: Intracoronary, Intraperitoneal, Intravenous, Subcutaneous.
What are the potential side effects of BQ-123?
Reported adverse effects include: Vasodilation / flushing, Injection site reactions, Headache, Hypotension. This list is not exhaustive — consult a qualified clinician.
Who should avoid BQ-123?
Recorded contraindications: Pregnancy, Hypersensitivity to BQ-123 or peptide excipients, Severe hypotension. Consult a qualified clinician before use.