Correct Answer: C. Omapatrilat
Omapatrilat is a vasopeptidase inhibitor that uniquely acts on BOTH angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP). This dual mechanism distinguishes it from other cardiovascular agents. ACE inhibition blocks conversion of angiotensin I to angiotensin II, reducing vasoconstriction and aldosterone secretion. Simultaneously, NEP inhibition prevents degradation of natriuretic peptides (ANP, BNP), enhancing their vasodilatory and natriuretic effects. This synergistic action provides superior hemodynamic benefits: reduced afterload via ACE inhibition plus enhanced preload reduction and vasodilation via natriuretic peptide preservation. In Indian clinical practice, omapatrilat was investigated for heart failure management, offering theoretical advantages over monotherapy ACE inhibitors. However, its development was halted globally due to angioedema risk in clinical trials, particularly in patients of African descent. The dual-target mechanism made it a landmark agent conceptually, even though it never reached routine clinical use in India. The question tests recognition that omapatrilat is the only agent among the options with dual ACE + NEP inhibitory activity.
Why the other options are wrong
A. Sacubitril — Sacubitril is a selective NEP inhibitor only, not an ACE inhibitor. It is always used in combination with valsartan (an ARB) in the fixed-dose formulation sacubitril/valsartan (Entresto), which provides NEP inhibition + ARB activity—not dual ACE + NEP inhibition. This is a common trap: students confuse sacubitril's role in the combination drug with dual inhibition, but sacubitril itself targets only NEP. B. Nesiritide — Nesiritide is a recombinant B-type natriuretic peptide (BNP) analog, not an enzyme inhibitor. It mimics the action of endogenous BNP but does not inhibit ACE or NEP. While it enhances natriuretic and vasodilatory effects, it lacks ACE inhibitory activity entirely. NBE often pairs nesiritide with natriuretic peptide therapy to distract from the enzyme-inhibitor mechanism required here. D. Losartan — Losartan is an angiotensin II receptor blocker (ARB) that blocks AT1 receptors, reducing angiotensin II effects. It does not inhibit ACE or NEP. While losartan is a cornerstone hypertension and heart failure agent in Indian practice, it acts downstream of ACE (blocking the receptor rather than enzyme) and has no NEP inhibitory activity, making it a single-mechanism agent.
High-Yield Facts
- Omapatrilat = ACE inhibitor + NEP inhibitor (vasopeptidase inhibitor); dual mechanism on both enzyme systems.
- Sacubitril = NEP inhibitor only; always paired with valsartan (ARB) in sacubitril/valsartan combination.
- Nesiritide = recombinant BNP analog; mimics natriuretic peptide action, not an enzyme inhibitor.
- Vasopeptidase inhibitors enhance natriuretic peptides while reducing angiotensin II—theoretical advantage in heart failure but angioedema risk halted development.
- NEP inhibition preserves ANP and BNP by blocking their degradation, enhancing vasodilation and sodium excretion.
Mnemonics
VASOPEPTIDASE = ACE + NEP Vasopeptidase inhibitors hit TWO enzymes: ACE (reduces Ang II) + NEP (preserves natriuretic peptides). Omapatrilat is the classic example. Use this when you see 'both marked areas' or 'dual mechanism' in CVS pharmacology. SAC-VAL = NEP + ARB (not ACE) Sacubitril/Valsartan (Entresto) = NEP inhibitor + ARB. NOT ACE inhibitor. Common trap: students think sacubitril is like omapatrilat, but it's only NEP.
NBE Trap
NBE exploits confusion between sacubitril (NEP-only) and omapatrilat (ACE + NEP dual inhibitor). Students familiar with sacubitril/valsartan (Entresto) in modern heart failure guidelines may incorrectly choose sacubitril, forgetting that omapatrilat is the only true vasopeptidase inhibitor with both ACE and NEP activity.
Clinical Pearl
In Indian heart failure clinics, sacubitril/valsartan (Entresto) has replaced omapatrilat as the modern dual-pathway agent, but omapatrilat remains a high-yield concept for NEET PG because it uniquely combines ACE + NEP inhibition in a single molecule—a distinction that defines vasopeptidase inhibitors and differentiates them from combination therapies.
_Reference: KD Tripathi Ch. 31 (Vasodilators & ACE Inhibitors); Harrison Ch. 233 (Heart Failure)_