 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 at the American Thoracic Society 2021 International Conference ATS 2021 preliminary interim data from the SPECTRA Phase 2 trial of sotatercept in patients with pulmonary arterial hypertension PAH. The findings, presented during the session Cli 