Peptides in Cardiology

Overview

Peptides play fundamental roles in cardiovascular physiology and have become indispensable tools in cardiac diagnostics and therapeutics. The natriuretic peptide system — comprising atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) — serves as both a critical biomarker platform and a therapeutic target. Beyond natriuretic peptides, research is expanding into peptide-based approaches for cardiac repair, anti-atherosclerotic therapy, antithrombotic agents, and blood pressure regulation.

The Natriuretic Peptide System

Biology

Natriuretic peptides are a family of hormonal peptides produced primarily by the heart in response to myocardial wall stress:

• ANP (Atrial Natriuretic Peptide) — A 28-amino-acid peptide secreted primarily by atrial cardiomyocytes in response to atrial stretch. ANP promotes natriuresis (sodium excretion), diuresis, and vasodilation, and inhibits the renin-angiotensin-aldosterone system (RAAS).
• BNP (B-type Natriuretic Peptide) — A 32-amino-acid peptide produced mainly by ventricular cardiomyocytes in response to volume overload and pressure overload. BNP shares similar physiological effects with ANP but is more closely associated with ventricular dysfunction.
• CNP (C-type Natriuretic Peptide) — Produced primarily by endothelial cells, CNP acts locally to regulate vascular tone and inhibit smooth muscle proliferation. It has less natriuretic activity but plays important roles in vascular remodeling.

All three peptides signal through natriuretic peptide receptors (NPR-A, NPR-B, NPR-C) and are degraded by the enzyme neprilysin and by receptor-mediated clearance through NPR-C.

BNP and NT-proBNP as Biomarkers

BNP and its amino-terminal cleavage fragment NT-proBNP are among the most clinically important peptide biomarkers in medicine:

• Heart failure diagnosis — Elevated BNP (greater than 100 pg/mL) or NT-proBNP (age-adjusted cutoffs) supports the diagnosis of heart failure in patients presenting with dyspnea. Normal levels have high negative predictive value for excluding heart failure.
• Prognosis — Serial BNP/NT-proBNP measurements predict outcomes in heart failure, acute coronary syndromes, and pulmonary embolism. Rising levels indicate worsening cardiac function.
• Guided therapy — BNP-guided heart failure management, where treatment is titrated to achieve target BNP levels, has been evaluated in multiple clinical trials with mixed but generally positive results.
• Screening — Population-level screening with natriuretic peptides to detect subclinical cardiac dysfunction is an active area of investigation.

NT-proBNP has a longer half-life than BNP (120 minutes vs. 20 minutes), making it more stable for laboratory measurement, though both are used clinically.

Therapeutic Natriuretic Peptides

Nesiritide

Nesiritide (recombinant BNP) was approved for acute decompensated heart failure, where it reduces pulmonary capillary wedge pressure and improves hemodynamics through vasodilation and natriuresis. However, its clinical use has been debated due to concerns about hypotension and the results of the ASCEND-HF trial, which showed symptomatic improvement but no reduction in mortality or rehospitalization.

Sacubitril/Valsartan (ARNI)

The most significant therapeutic advance leveraging the natriuretic peptide system is sacubitril/valsartan, an angiotensin receptor-neprilysin inhibitor (ARNI). Sacubitril inhibits neprilysin, the enzyme that degrades natriuretic peptides, thereby increasing endogenous ANP and BNP levels. Combined with valsartan (an angiotensin II receptor blocker), this dual mechanism provides complementary neurohormonal modulation.

The PARADIGM-HF trial demonstrated that sacubitril/valsartan reduced cardiovascular death and heart failure hospitalization by 20% compared to enalapril in patients with heart failure and reduced ejection fraction, establishing ARNI therapy as a cornerstone of heart failure treatment.

Designer Natriuretic Peptides

Researchers are engineering modified natriuretic peptides with enhanced properties:

• Cenderitide (CD-NP) — A chimeric peptide combining CNP with the C-terminal tail of Dendroaspis natriuretic peptide, designed to activate both NPR-A and NPR-B receptors for balanced cardiorenal protection
• MANP (mutant ANP) — Engineered ANP variants with increased resistance to neprilysin degradation and enhanced renal protective effects
• ZD100 — A designer peptide with combined natriuretic, anti-fibrotic, and anti-hypertrophic properties

Peptides in Cardiac Repair

After Myocardial Infarction

Peptide-based approaches to cardiac repair following myocardial infarction represent a growing research frontier:

• Self-assembling peptide hydrogels — Injectable peptide hydrogels that form scaffolds within infarcted myocardium, providing mechanical support, promoting angiogenesis, and serving as delivery vehicles for therapeutic cells or growth factors. Several candidates have shown promising preclinical results in reducing infarct size and improving ventricular function.
• Thymosin beta-4 (TB4) — A 43-amino-acid peptide involved in actin polymerization that has demonstrated cardioprotective effects in preclinical models, including reduction of infarct size, promotion of angiogenesis, and activation of resident cardiac progenitor cells.
• Peptide-based growth factor mimetics — Short peptides that mimic the receptor-binding domains of VEGF, FGF, and other angiogenic growth factors, designed to stimulate neovascularization in ischemic myocardium without the stability and cost issues of full-length protein delivery.

Anti-Fibrotic Peptides

Cardiac fibrosis contributes to heart failure progression. Peptide inhibitors of transforming growth factor-beta (TGF-beta) signaling and connective tissue growth factor (CTGF) are under investigation for their ability to reduce pathological fibrosis while preserving necessary wound healing.

Peptides in Hypertension

RAAS-Targeting Peptides

The renin-angiotensin-aldosterone system is a peptide cascade central to blood pressure regulation. Angiotensin II, an 8-amino-acid peptide, is the primary effector. Therapeutic interventions targeting this cascade include:

• ACE inhibitors (blocking angiotensin I to angiotensin II conversion)
• Angiotensin receptor blockers (blocking angiotensin II signaling)
• Direct renin inhibitors (blocking the initial cleavage of angiotensinogen)

Novel Antihypertensive Peptides

Research into novel peptide-based antihypertensive approaches includes:

• Angiotensin-(1-7) — A counter-regulatory peptide that opposes many effects of angiotensin II, promoting vasodilation and anti-inflammatory effects. Stabilized analogs and oral formulations are in development.
• Natriuretic peptide analogs — Long-acting ANP and BNP variants designed for chronic blood pressure management
• Food-derived antihypertensive peptides — ACE-inhibitory peptides derived from milk (lactotripeptides IPP and VPP), fish, and soy proteins, studied for their mild blood pressure-lowering effects

Antithrombotic Peptides

Peptides and peptide-derived agents play roles in anticoagulation and antiplatelet therapy:

• Bivalirudin — A 20-amino-acid synthetic peptide that directly inhibits thrombin. Used as an anticoagulant during percutaneous coronary intervention, bivalirudin offers predictable pharmacokinetics and a shorter duration of action compared to heparin.
• Eptifibatide (Integrilin) — A cyclic peptide glycoprotein IIb/IIIa inhibitor derived from the venom of the southeastern pygmy rattlesnake. It inhibits platelet aggregation and is used in acute coronary syndromes.
• Novel antithrombotic peptides — Peptide inhibitors of factor XIa and other coagulation factors are in development, aiming to provide anticoagulation with reduced bleeding risk.

Challenges and Outlook

Cardiovascular peptide therapeutics face challenges common to the broader field: short half-lives requiring continuous infusion or frequent dosing, the need for parenteral administration for most candidates, and the requirement for large clinical trials given the scale of cardiovascular disease populations. However, advances in half-life extension, oral peptide delivery, and self-assembling peptide technologies for local cardiac delivery are addressing these limitations.

The natriuretic peptide system, in particular, remains a rich source of therapeutic innovation, with designer peptides and neprilysin inhibition continuing to reshape heart failure management. Cardiac repair peptides represent a longer-term opportunity, with several candidates progressing through preclinical development toward early clinical trials.