As with prior studies (19) of other BET inhibitors in PAH rats, in both rat models, we observed a reduction of indices of disease, including reduced pulmonary vascular muscularization [via alpha-smooth muscle actin (α-SMA) stain], right ventricular systolic pressure (RVSP), and Fulton index (Fig. 4, F to H and N to P). Here, ACTA1 is linked to pulmonary arterial hypertension.