Alternative RNA splicing may provide unique opportunities to identify drug targets and therapeutics. We identified an alternative spliced transcript for B-type natriuretic peptide (BNP) resulting from intronic retention. This transcript is present in failing human hearts and is reduced following mechanical unloading. The intron-retained transcript would generate a unique 34 amino acid (aa) carboxyl terminus while maintaining the remaining structure of native BNP. We generated antisera to this carboxyl terminus and identified immunoreactivity in failing human heart tissue. The alternatively spliced peptide (ASBNP) was synthesized and unlike BNP, failed to stimulate cGMP in vascular cells or vasorelax preconstricted arterial rings. This suggests that ASBNP may lack the dose-limiting effects of recombinant BNP. Given structural considerations, a carboxyl-terminal truncated form of ASBNP was generated (ASBNP.1) and was determined to retain the ability of BNP to stimulate cGMP in canine glomerular isolates and cultured human mesangial cells but lacked similar effects in vascular cells. In a canine-pacing model of heart failure, systemic infusion of ASBNP.1 did not alter mean arterial pressure but increased the glomerular filtration rate (GFR), suppressed plasma renin and angiotensin, while inducing natriuresis and diuresis. Consistent with its distinct in vivo effects, the activity of ASBNP.1 may not be explained through binding and activation of NPR-A or NPR-B. Thus, the biodesigner peptide ASBNP.1 enhances GFR associated with heart failure while lacking the vasoactive properties of BNP. These findings demonstrate that peptides with unique properties may be designed based on products of alternatively splicing.