Curium, a radiopharmaceutical company backed by Irish-led private equity firm CapVest, has agreed to buy peer Lantheus Holdings in a deal worth up to $8 billion.   The transaction represents a total per-share consideration of up to $114.50 a share. The board of directors of Lantheus has unanimously approved the transaction, according to an announcement issued on Monday. The combined companies will create a radiopharmaceutical company spanning diagnostics and therapeutics, with the infrastructure and capabilities to serve patients in more than 70 countries. CapVest, which was founded by Seamus Fitzpatrick, established Curium in 2017 by merging IBA Molecular and Mallinckrodt…