Novartis, which spends up to $400m (£247.9m) a year on external lawyers, previously had a 15-firm global panel.
Many of the previous members, including Cravath Swaine & Moore, Kaye Scholer, Wachtell Lipton Rosen & Katz and WilmerHale, have been transferred to the US panel.
Following a review by the company’s UK legal head, the first UK panel includes A&O, Arnold & Porter, Freshfields, Covington & Burling, Linklaters and SJ Berwin. Linklaters will deal mainly with M&A and antitrust matters, while SJ Berwin will handle patent litigation.
Werlen has spent three years overhauling Novartis’s 250-lawyer team, dividing it into practice areas and appointing global heads of the different groups, including M&A, antitrust, litigation and capital markets.