Stimulating the apelin pathway offers beneficial vasodilatory haemodynamic effects (Maguire et al., 2009), increases cardiac contractility (Perjes et al., 2014), has been shown to improve cardiac output in PAH patients (Brash et al., 2018), and is suggested to address underlying drivers of PAH disease progression (Falcao-Pires et al., 2009; Alastalo et al., 2011; Yang et al., 2017; 2019). Here, APLN is linked to pulmonary arterial hypertension.