Big Pharma leads the list of billion-dollar deals this week with a $40 billion, unsolicited bid made by Israel's Teva Pharmaceutical Industries Ltd. for fellow generic-drug maker Mylan N.V.

Both companies have recently been busy in the deal space. In late March, Teva turned to Goodwin Procter for counsel on its $3.2 billion buy of La Jolla, California-based orphan-drug maker Auspex Pharmaceuticals, which was advised by Cooley.

Last year Mylan sought a corporate tax advantage through a $5.3 billion deal with Abbott Laboratories to relocate some of its operations to the Netherlands. Cravath, Swaine & Moore, which worked on that deal for Mylan, also took the lead for the company earlier this month on its unsolicited $28.9 billion takeover bid for Irish drugmaker Perrigo, the latter advised by Wachtell, Lipton, Rosen & Katz and leading Irish firm A&L Goodbody. Perrigo rejected Mylan's offer this week.