The article describes the development of a novel immunoassay for the quantification of BNP fragments cleaved by neprilysin. The study shows that the concentration of the neprilysin cleaved BNP fragments varies in patients with heart failure and that the ratio of cleaved BNP/total BNP does not correlate with the concentration of total BNP making it an independent parameter. The results obtained in this study indicate that it might be possible to prescreen patients that would benefit from neprilysin inhibition treatment (Entresto™) using the novel immunoassay. The assay could also be used for monitor the efficacy of the treatment.