A half-dozen Global 100 firms have grabbed roles on the proposed $32 billion merger between rare disease drug makers Shire plc and Baxalta Inc.

Dublin-based Shire announced Monday that it had struck a cash-and-stock deal to acquire Bannockburn, Illinois-based Baxalta after a five-month pursuit. Back in August, Shire announced a $30 billion all-stock takeover bid for Baxalta, which was promptly turned down by the target. But Shire sweetened its offer.