Angioedema Risk in Neprilysin Inhibition

Reviewed literature on neprilysin inhibition, bradykinin, and angioedema risk.

Neprilysin degrades bradykinin (and substance P) alongside its better-known role on natriuretic peptides, so any NEP inhibitor will tend to raise bradykinin levels — and bradykinin is the main mediator of non-histaminergic, ACE-inhibitor-style angioedema (Campbell 2018). ACE has the dominant low-Km role in plasma and most vascular beds, but neprilysin contributes meaningfully in tissue compartments (renal tubules, cardiac interstitium, brush-border membranes), which is why inhibiting it on top of ACE — not in isolation — is where the angioedema signal blows up (Campbell 2018).

The cleanest clinical demonstration is omapatrilat, a single molecule inhibiting ACE + NEP (and also aminopeptidase P, NEP2, ECE-1). In the OCTAVE hypertension trial (n=25,302), angioedema occurred in 2.17% on omapatrilat vs 0.68% on enalapril — a ~3-fold excess, with 88 of the omapatrilat cases on day 1, often within hours of the first dose, and two events involving airway compromise (Shi et al. 2018). That signal killed the program. In the OVERTURE heart-failure trial the absolute rates were much lower (0.8% vs 0.5%) and not significantly different, which is generally read as HF patients having a suppressed kallikrein-kinin system and being less susceptible (Campbell 2018 +1).

Sacubitril/valsartan was deliberately engineered around this. Pairing NEP inhibition with an ARB (rather than an ACE inhibitor) avoids the synergistic block of bradykinin degradation, and LBQ657 is more selective than omapatrilat's broader peptidase profile (Shi et al. 2018). In PARADIGM-HF, adjudicated angioedema during the double-blind phase was 0.45% on sacubitril/valsartan vs 0.24% on enalapril (RR 1.9, 95% CI 0.8–4.5) — numerically higher but not statistically significant, no airway compromise, no deaths (Shi et al. 2018). A 36-hour washout between ACEi and ARNI is built into the label specifically to avoid overlapping ACE + NEP inhibition (Shi et al. 2018). Caveats worth knowing: PARADIGM-HF excluded patients with prior ACEi/ARB-induced angioedema and used sequential run-ins, both of which deplete susceptibles before randomization (Shi et al. 2018).

Real-world data are broadly reassuring. A large FDA Sentinel propensity-matched cohort found no excess risk of angioedema for sacubitril/valsartan vs ACE inhibitors (HR 0.18, 95% CI 0.11–0.29) or vs ARBs (HR 0.59, 95% CI 0.35–1.01) in new users (Eworuke et al. 2023). The important nuance: patients who switched from an ACEi or ARB to sacubitril/valsartan within 14 days had ~2-fold higher angioedema risk than de novo ARNI starters (HR 1.98 for recent ACEi switch, HR 2.45 for recent ARB switch) — consistent with residual ACE inhibition overlapping NEP inhibition (Eworuke et al. 2023). Black patients carry higher baseline risk on any RAAS modulator and showed the same pattern with ARNI (2.35% vs 0.47% in PARADIGM-HF black subgroup, though n is small) (Shi et al. 2018).

Practical picture: the bradykinin-angioedema risk from NEP inhibition is real but modest in isolation; it becomes clinically important when NEP inhibition is stacked on ACE inhibition (omapatrilat, or improper ACEi→ARNI switches). Pairing NEP inhibition with an ARB and honoring the 36-hour washout is what makes ARNI therapy tolerable.