ZURICH/LONDON (Reuters) – Drugmaker Shire (SHP.L) is preparing to make a new takeover offer for U.S. biotech firm Baxalta (BXLT.N) that if successful will create one of the world’s leading specialists in rare diseases, a source with direct knowledge of the situation said on Tuesday. The London-listed group has asked its advisers to renew its bid effort, the source said, almost four months after Baxalta rejected an unsolicited $30 billion offer that it said significantly undervalued the company. Shire’s bid preparations come three weeks after it announced its $5.9 billion purchase of U.S.