Therapeutic Targeting of Vascular Remodeling and Right Heart Failure in Pulmonary Arterial Hypertension with a HIF-2α Inhibitor

Rationale: Pulmonary arterial hypertension (PAH) is a devastating disease characterized by progressive vasoconstriction and obliterative vascular remodeling that leads to right heart failure (RHF) and death. Current therapies do not target vascular remodeling and RHF, and result in only modest improvement of morbidity and mortality. Objectives: To determine whether targeting HIF-2 alpha (hypoxia-inducible factor-2 alpha) with a HIF-2 alpha-selective inhibitor could reverse PAH and RHF in various rodent PAH models. Methods: HIF-2 alpha and its downstream genes were evaluated in lung samples and pulmonary arterial endothelial cells and smooth muscle cells from patients with idiopathic PAH as well as various rodent PAH models. A HIF-2 alpha-selective inhibitor was used in human lung microvascular endothelial cells and in Egln1(Tie2Cre) mice, and in Sugen 5416/hypoxia- or monocrotaline-exposed rats. Measurements and Main Results: Upregulation of HIF-2 alpha and its target genes was observed in lung tissues and isolated pulmonary arterial endothelial cells from patients with idiopathic PAH and three distinct rodent PAH models. Pharmacological inhibition of HIF-2 alpha by the HIF-2 alpha translation inhibitor C76 (compound 76) reduced right ventricular systolic pressure and right ventricular hypertrophy and inhibited RHF and fibrosis as well as obliterative pulmonary vascular remodeling in Egln1(Tie2C)(re) mice and Sugen 5416/hypoxia PAH rats. Treatment of monocrotaline-exposed PAH rats with C76 also reversed right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary vascular remodeling; prevented RHF; and promoted survival. Conclusions: These findings demonstrate that pharmacological inhibition of HIF-2 alpha is a promising novel therapeutic strategy for the treatment of severe vascular remodeling and right heart failure in patients with PAH.