Abbvie Inc.'s Skyrizi (risankizumab), a medicine for adults with moderate to severe plaque psoriasis, won FDA approval and is expected to be available in the U.S. in early May, the company said. Abbvie paid Boehringer Ingelheim GmbH (BI) $595 million up front for rights to the anti-IL-23 therapy and another asset in 2016 while promising further significant milestone and royalty payments to come for the German company.