Several top-tier firms from around the globe advised on Thermo Fisher Scientific’s $11.5 billion acquisition of the German genetic testing company Qiagen—the biggest health care acquisition so far this year.

Wachtell, Lipton, Rosen & Katz had the lead role advising Thermo Fisher, while Linklaters was the lead firm advising Qiagen, with Amsterdam-based De Brauw Blackstone Westbroek and Mintz, Levin, Cohn, Ferris, Glovsky and Popeo also serving as legal counsel.