Wachtell, Lipton, Rosen & Katz and Kirkland & Ellis, along with the Magic Circle firms Slaughter and May and Clifford Chance, are advising on a £9.8 billion ($12.4 billion) trans-Atlantic joint venture between pharma giants GlaxoSmithKline and Pfizer.

Under the agreement, which was announced on Wednesday, the two public companies will combine their consumer health businesses into a joint venture, with anticipated sales expected to be close to £10 billion ($12.6 billion). GSK, which is headquartered in the U.K., will retain a 68 percent controlling interest, while U.S.-based Pfizer will have an equity interest of 32 percent. The joint venture will create the world’s largest over-the-counter medicines business.