A potential new treatment for the rare condition Wilson disease moved a step closer to reality after Alexion Pharmaceuticals Inc., now part of Astrazeneca plc, announced positive top-line results from a phase III trial of ALXN-1840 (tiomolibdate choline). Astrazeneca’s shares (NASDAQ:AZN) ticked up following the announcement, closing Aug. 26 at $58.76, up 18 cents. From the point of view of the big U.K. pharma, it’s a good piece of news as it hopes to build a rare disease franchise from its $39 billion acquisition of Alexion, which was completed last month.