Shire Plc agreed to buy Baxalta Inc. for about $32 billion to become the world’s biggest maker of so-called orphan drugs for rare diseases.br The price includes 0.1482 of Shire’s American depositary receipts and $18 in cash for each Baxalta share held, the Dublin-based drugmaker said in a statement.br Baxalta had rebuffed an unsolicited $30 billion all-stock bid that valued the company at $45.23 a share in July.br The acquisition of the Deerfield, Illinois-based company boosts Shire’s position in the market for rare-disease treatments, which will grow by more than 60 percent over the next five years to $176 billion, according to market researcher EvaluatePharma.br The combined company would generate $20 billion in sales by 2020, Shire said.