CapVest Partners, the private-equity fund led by the Irish dealmaker Seamus Fitzpatrick, is acquiring a majority stake in German pharmaceutical company Stada Arzneimittel AG, in a transaction that values the business at €10 billion including debt. In a statement this morning, CapVest said it had signed a definitive agreement to acquire the controlling stake from Bain Capital and Cinven, two other private equity firms who will continue to hold minority stakes in the business. Founded in 1999, this is the largest ever deal by CapVest, which is best known in Ireland as the previous owner of the Mater Private hospital…