TGFB1 and pulmonary arterial hypertension: Sotatercept is a novel, first-in-class recombinant fusion protein that isundergoing evaluation in PAH.89 Sotatercept binds activins and GDFs to restore homeostasisbetween pro- and antiproliferative signals in the TGF-β superfamilypathway, which are imbalanced in PAH.