Neprilysin Inhibition and Natriuretic Peptides

Neprilysin inhibition natriuretic peptides sacubitril

Introduction

I'll pull up research on neprilysin inhibition, natriuretic peptides, and sacubitril — covering mechanisms, clinical trial data, and biomarker effects.

Mechanism: What neprilysin actually does

Neprilysin (NEP) is a membrane-bound zinc metalloendopeptidase that cleaves a broad array of vasoactive peptides at the extracellular surface. Its primary cardiovascular substrates include ANP, BNP, CNP, bradykinin, adrenomedullin, substance P, angiotensin II, and endothelin-1. Sacubitril is a prodrug: after oral ingestion it is hydrolyzed by esterases to its active metabolite LBQ657, which inhibits NEP. Because standalone NEP inhibition would paradoxically raise angiotensin II (another NEP substrate), it is combined with the ARB valsartan in a 1:1 molar supramolecular complex — the ARNI sacubitril/valsartan (LCZ696, Entresto).

The natriuretic peptide story is more complicated than it appears

The conventional narrative — "sacubitril augments BNP" — turns out to be an oversimplification. A mechanistic clinical study by Nogué et al. in European Journal of Heart Failure found that ANP, not BNP, is the principal natriuretic peptide affected by NEP inhibition in heart failure. When 23 HFrEF patients were initiated on sacubitril/valsartan, ANP more than doubled within the first three weeks (+106%), and increases were sustained and even larger in those with higher baseline ANP concentrations (+188% vs +44%). BNP changes were inconsistent across assays, and CNP showed no consistent change.

Why does BNP respond differently? Two converging findings explain this. First, in human plasma the major circulating form of BNP is actually proBNP (the 108-amino acid precursor), and proBNP is structurally resistant to neprilysin cleavage. Mature BNP(1-32) is a NEP substrate, but most of what clinical assays measure isn't the mature form. Second, a 2025 paper in Scientific Reports identified a close NEP homolog, neprilysin 2 (NEP2), expressed in cardiomyocytes and endothelial cells, which can cleave ANP and BNP and — critically — is insensitive to sacubitrilat at the concentrations studied. This means a parallel degradation pathway for natriuretic peptides remains active even under sacubitril therapy.

There is also an endogenous feedback circuit: a JACC Heart Failure study in 638 emergency department patients found that when plasma BNP rises above about 916 pg/mL in acute decompensated heart failure, circulating NEP activity is markedly suppressed — suggesting that high BNP itself functions as an endogenous NEP inhibitor. The Singh et al. review in Heart coined this "autoinhibition" and proposed that sacubitril/valsartan may be pre-emptively inducing this same surge earlier in the decompensation trajectory.

Beyond natriuretic peptides, NEP inhibition raises bradykinin (explaining the angioedema risk, which is why concurrent ACEi use is contraindicated and a 36-hour washout is required), adrenomedullin, and substance P — each of which contributes to vasodilatation and potentially to the drug's efficacy.

Biomarker implications for clinical monitoring

Because BNP is a direct NEP substrate (even if much of circulating BNP is proBNP), neprilysin inhibition raises immunoreactive BNP, potentially making BNP a misleadingly elevated biomarker of cardiac status in patients on sacubitril/valsartan. NT-proBNP is not cleaved by NEP and typically declines with treatment, reflecting genuine hemodynamic improvement. The practical recommendation from multiple authors is to use NT-proBNP (not BNP) as the monitoring biomarker in patients on ARNI therapy.

PARADIGM-HF and clinical evidence

The clinical anchor for this mechanism is PARADIGM-HF, the landmark phase 3 RCT that enrolled 8,442 HFrEF patients (EF ≤40%) on background therapy (93% on beta-blockers, 56% on mineralocorticoid antagonists) and randomized them to sacubitril/valsartan 200 mg twice daily vs. enalapril 10 mg twice daily. The trial was stopped early by the DSMB after a median follow-up of 27 months due to overwhelming benefit: the primary composite of CV death or HF hospitalization occurred in 21.8% of the sacubitril/valsartan group vs. 26.5% with enalapril, roughly a 20% relative risk reduction. All-cause mortality was 17.0% vs. 19.8%. Number needed to treat to prevent one death was about 35. Sacubitril/valsartan caused more hypotension but less renal impairment, hyperkalemia, and cough than enalapril. Angioedema was rare but more frequent. The benefit was consistent across age subgroups in PARADIGM-HF.

For HFpEF (PARAGON-HF), results were less clear-cut. A systematic review and meta-analysis found sacubitril/valsartan significantly reduced first HF hospitalization (around a 14% relative reduction) and improved quality-of-life scores (KCCQ), but did not demonstrate a statistically significant reduction in all-cause or CV mortality when pooled across HFrEF and HFpEF populations.

The mechanistic picture is evolving — the role of NEP2, the relative contributions of different NEP substrates to clinical benefit, and the optimal biomarker strategy all remain active research questions, making this a richer area than the standard "more natriuretic peptides = better" framing suggests.