 CAMBRIDGE, Mass.--BUSINESS WIRE--Acceleron Pharma Inc. Nasdaq: XLRN, a leading biopharmaceutical company in the discovery, development, and commercialization of TGF-beta superfamily therapeutics to treat serious and rare diseases, today presented a set of preliminary interim data from the ongoing SPECTRA Phase 2 trial of sotatercept in patients with pulmonary arterial hypertension PAH. Initial data from the trial, which is designed to assess resting and exercise hemodynamics and peak oxyg 