Sacubitril/valsartan (LCZ696) is a supramolecular sodium complex that delivers three pharmacologically active analytes after oral ingestion. Sacubitril, a prodrug, is rapidly cleaved by esterases to the active neprilysin inhibitor sacubitrilat (LBQ657), reaching peak plasma concentrations within approximately 1.5–2 hours. Valsartan, the angiotensin receptor blocker component, reaches peak concentrations within 2–3 hours. Both moieties distribute extensively into cardiac, renal, and vascular tissues — the sites where their complementary targets reside.

Neprilysin inhibition by sacubitrilat. Neprilysin (neutral endopeptidase 24.11; NEP) is a membrane-bound zinc metalloprotease that cleaves a broad array of vasoactive peptides, with susceptibility to degradation greatest for CNP > ANP > BNP. Sacubitrilat binds to the enzyme's active site and blocks this proteolytic activity. The immediate consequence is an accumulation of the intact natriuretic peptides ANP, BNP, and CNP in the circulation and in cardiac and renal tissues. Beyond natriuretic peptides, NEP also degrades bradykinin, substance P, and adrenomedullin; inhibition of neprilysin therefore simultaneously raises circulating levels of these vasodilator peptides alongside the natriuretic peptides, contributing to the drug's overall hemodynamic effect.

Natriuretic peptide receptor activation and cGMP signaling. Accumulated ANP and BNP bind to natriuretic peptide receptor-A (NPR-A, a membrane-bound guanylyl cyclase), while CNP engages NPR-B. Ligand binding activates the intrinsic guanylyl cyclase domain, synthesizing the second messenger cyclic 3′,5′-guanosine monophosphate (cGMP) across a wide variety of tissues and cell types. Elevated intracellular cGMP activates cGMP-dependent protein kinase G (PKG), which phosphorylates numerous downstream substrates. In vascular smooth muscle, PKG-mediated phosphorylation of RhoA at Ser188 suppresses RhoA/ROCK-driven cytoskeletal contraction and fibrogenic signaling, directly mediating vasodilation and anti-fibrotic effects. In the kidney, PKG activation increases glomerular filtration rate, promotes natriuresis, and drives diuresis by modulating tubular sodium handling.

Anti-remodeling and anti-fibrotic signaling. In cardiomyocytes, the cGMP–PKG axis phosphorylates the regulator of G-protein signaling subtype 4 (RGS4), thereby blunting Gαq signaling downstream of the AT1 receptor and inhibiting activation of transient receptor potential C6 (TRPC6) — two pathways that otherwise drive pathological hypertrophy and calcium overload. PKG also attenuates genomic actions of the cardiac mineralocorticoid receptor, reducing aldosterone-driven fibrotic gene expression. CNP, acting through NPR-B in cardiac fibroblasts, provides an additional anti-fibrotic brake: paracrine CNP/GC-B/cGMP signaling in cardiac fibroblasts directly opposes TGF-β– and angiotensin II–driven collagen deposition and myofibroblast differentiation. Consistent with these mechanisms, clinical data from HFrEF patients treated with sacubitril/valsartan show significant reductions in serum markers of collagen synthesis (PINP and PIIINP) that correlate with echocardiographic reverse remodeling.

AT1 receptor blockade by valsartan. Valsartan acts at a distinct molecular target, selectively and competitively blocking the angiotensin II type-1 receptor (AT1R). Because neprilysin also cleaves angiotensin I and II, sacubitrilat inhibition raises circulating angiotensin II — a pharmacological rationale that makes concurrent AT1R blockade essential. Valsartan's AT1R blockade prevents angiotensin II–mediated vasoconstriction, aldosterone secretion, and sympathetic activation. In the Val-HeFT trial, AT1R blockade with valsartan produced a sustained 17.4% reduction in plasma aldosterone sustained over two years in patients with heart failure, translating to reduced sodium retention and attenuated profibrotic aldosterone signaling. Valsartan's displacement of angiotensin II from AT1Rs also redistributs angiotensin II toward the AT2 receptor, which activates counter-regulatory vasodilatory and antiapoptotic pathways.

Parallel substrates and broader effects. Sacubitrilat-mediated NEP inhibition also prevents breakdown of adrenomedullin and substance P, contributing to additional vasodilation and possible cardioprotective effects. These non-natriuretic-peptide substrates — bradykinin, substance P, and adrenomedullin — may contribute meaningfully to sacubitril/valsartan's efficacy beyond natriuretic peptide augmentation alone. Mechanistic studies in HFrEF patients also reveal that sacubitril/valsartan downregulates miR-425 and miR1-3p, restoring proANP processing and increasing levels of multiple proANP-derived bioactive peptides by mechanisms beyond direct NEP inhibition.

The clinical translation of these converging molecular events was demonstrated in PARADIGM-HF, where the dual mechanism — enhanced natriuretic peptide signaling plus RAAS suppression — reduced cardiovascular death or heart failure hospitalization by 20% and all-cause mortality by 16% compared with enalapril. This dual action addresses two principal pathophysiological drivers of heart failure: chronic activation of the renin-angiotensin-aldosterone system and attenuated sensitivity to natriuretic peptides — a combination that produces greater neurohormonal modulation than either mechanism alone can achieve.