Keros Therapeutics Inc. announced preliminary results from a phase I trial of its engineered ligand trap KER-012 that gave its team confidence to proceed with larger studies in pulmonary arterial hypertension (PAH) and potentially some bone diseases. But company shares (NASDAQ:KROS) fell 16.6% to $38.50 May 18, following the announcement, perhaps over concerns about trial subjects that emerged in a company-hosted investor call.