Figure 11 shows that although publications on ET antagonists reached a peak in 2011, patenting and medicinal chemistry output was already declining by the late 1990s and only a small number of patents continue to be filed, most recently in 2015. This latter is a series of phenoxybutanoic acid derivatives with a lead compound identified as a potent and selective ETA antagonist with efficacy in animal models of hypoxia-induced PAH (Cai et al., 2015). Here, EDNRA is linked to pulmonary arterial hypertension.