COPENHAGEN (Reuters) - Denmark's Novo Nordisk, the world's biggest insulin producer, said on Monday it got the final go-ahead from authorities to market its long-acting diabetes drug Tresiba in Europe. Novo Nordisk said in a statement that the European Commission had granted marketing authorization for Tresiba and another insulin, Ryzodeg. Novo Nordisk, the world's biggest insulin producer, has estimated that Tresiba, the brand name for the active ingredient degludec, could become a blockbuster drug. A drug reaches blockbuster status when it generates more than $1 billion in annual sales. ...