Objectives Our aim was to design, synthesize and test in vivo and in vitro a new chimeric peptide that would combine the beneficial properties of 2 distinct natriuretic peptides with a biological profile that goes beyond native peptides. Background Studies have established the beneficial vascular and antiproliferative properties of C-type natriuretic peptide (CNP). While lacking renal actions, CNP is less hypotensive than the cardiac peptides atrial natriuretic peptide and B-type natriuretic peptide but unloads the heart due to venodilation. Dendroaspis natriuretic peptide is a potent natriuretic and diuretic peptide that is markedly hypotensive and functions via a separate guanylyl cyclase receptor compared with CNP. Methods Here we engineered a novel chimeric peptide CD-NP that represents the fusion of the 22-amino acid peptide CNP together with the 15-amino acid linear C-terminus of Dendroaspis natriuretic peptide. We also determined in vitro in cardiac fibroblasts cyclic guanosine monophosphate-activating and antiproliferative properties of CD-NP. Results Our studies demonstrate in vivo that CD-NP is natriuretic and diuretic, glomerular filtration rate enhancing, cardiac unloading, and renin inhibiting. CD-NP also demonstrates less hypotensive properties when compared with B-type natriuretic peptide. In addition, CD-NP in vitro activates cyclic guanosine monophosphate and inhibits cardiac fibroblast proliferation. Conclusions The current findings advance an innovative design strategy in natriuretic peptide drug discovery and development to create therapeutic peptides with favorable properties that may be preferable to those associated with native natriuretic peptides.

CD-NP is a novel chimeric natriuretic peptide (NP) consisting of the 22-amino-acid (AA) human C-type natriuretic peptide (CNP), a venodilating peptide with limited renal actions and minimal effects on blood pressure, and the 15-AA C-terminus of Dendroaspis NP (DNP). The rationale for the design of CD-NP was to enhance the renal actions of CNP, the ligand for natriuretic peptide receptor-B, but without inducing excessive hypotension. Here we report the first-in-human studies for CD-NP, which represent the first successful clinical testing of a chimeric NP demonstrating in normal human volunteers that CD-NP possesses cyclic guanosine monophosphate-activating, natriuretic, and aldosterone-suppressing properties without inducing excessive hypotension, laying the foundation for additional studies on this first-in-class new cardiovascular therapeutic in human heart failure, which are now underway worldwide. KeywordsChimeric natriuretic peptide; CD-NP; C-type natriuretic peptide; Dendroaspis natriuretic peptide The design of novel chimeric peptides that are engineered to enhance the favorable properties of native peptides and delete or minimize unfavorable biological actions is an emerging therapeutic strategy in drug discovery.1 , 2 The novel chimeric natriuretic peptide, CD-NP,3 is being developed for the treatment of acute heart failure (AHF); there is a tremendous unmet need for therapy for this rapidly increasing cardiovascular syndrome, which has poor outcomes, and new drugs have repeatedly failed in clinical development.4 CD-NP represents the fusion of the 22-amino-acid (AA) human C-type natriuretic peptide (CNP) with the 15-AA C-terminus of Dendroaspis natriuretic peptide (DNP) (Figure 1).3 The rationale for its design was based on our knowledge that CNP,5 an endothelial6 , 7 cellderived peptide, which mediates favorable cardiovascular hemodynamic effects via the natriuretic peptide receptor (NPR)-B and the second messenger cyclic guanosine monophosphate (cGMP), unloads the heart without inducing excessive hypotension.8 These cardiovascular properties are based on the previous demonstration that CNP primarily

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These studies establish that DNP is a potent natriuretic and diuretic peptide with tubular actions linked to cGMP and that DNP may play a physiological role in the regulation of sodium excretion.

Background-Neutral endopeptidase 24.11 (NEP) is a metalloprotease that is localized in the greatest abundance in the kidney and degrades natriuretic peptides, such as atrial natriuretic peptide (ANP). Mild congestive heart failure (CHF) is characterized by increases in circulating ANP without activation of the renin-angiotensin-aldosterone system (RAAS) or sodium retention. In contrast, severe CHF is characterized by sodium retention and coactivation of both ANP and the RAAS. Methods and Results-We defined the acute cardiorenal actions of the NEP inhibitor candoxatrilat (8 g ⅐ kg Ϫ1 ⅐ min Ϫ1 ) in 4 groups of anesthetized dogs (normal, nϭ8; mild CHF, nϭ6; severe CHF, nϭ5; and severe CHF with chronic AT 1 receptor antagonism, nϭ5). Mild CHF was produced by rapid ventricular pacing at 180 bpm for 10 days and severe CHF at 245 bpm for 10 days. In mild CHF, urinary sodium excretion and glomerular filtration rate were greatest in response to acute NEP inhibition compared with the response in either control animals or those with severe CHF. Furthermore, an increase in glomerular filtration rate was observed only in mild CHF in association with increases in renal blood flow and decreases in renal vascular resistance and distal tubular sodium reabsorption. Urinary ANP and cGMP excretion, markers for renal biological actions of ANP, were greatest in mild CHF. The renal actions observed in mild CHF were attenuated in severe CHF and not restored by chronic AT 1 receptor antagonism. Conclusions-The results of the present study demonstrate that acute NEP inhibition in mild CHF results in marked increases in renal hemodynamics and sodium excretion that exceed that observed in control animals and severe CHF. These studies underscore the potential therapeutic role for NEP inhibition to enhance renal function in mild CHF, an important phase of CHF that is marked by selective activation of endogenous ANP in the absence of an activated RAAS.