Roche Holding AG has owned a significant stake in Genentech Inc. since 1990, and as the Swiss drugmaker tries to take that stake to 100%, both companies have turned to law firms that helped craft the agreement governing their relationship.

Roche first bought a stake in San Francisco-based Genentech in 1990, with the buyer using Davis Polk & Wardwell, J.P. Morgan and Lehman Brothers Holdings Inc., and the seller tapping Brobeck, Phleger & Harrison LLP and Wachtell, Lipton, Rosen & Katz. The parties recut the deal in 1995, and in 1999, Roche bought in Genentech's public float and then reissued stock in the target. As part of the transaction, the parties signed an affiliation agreement on which Roche used Davis Polk and Genentech used Wilson Sonsini Goodrich & Rosati PC.

The companies are tapping the same law firms this time, with Davis Polk's John Butler, Arthur Golden and Christopher Mayer and Wilson's Larry Sonsini, Steve Bochner, Martin Korman and Mike Ringler taking lead roles. Davis has advised Roche since at least the late 1980s. The law firm's first major assignment was on Roche's failed hostile bid for Sterling Drug Inc., which ended up selling to Eastman Kodak Co. Davis has advised Roche on a variety of litigation and corporate matters since then and handled the legal work on Roche's $3.4 billion acquisition of Ventana Medical Systems Inc. last year.

Wilson has a long relationship with Genentech. The San Francisco biotech's chief compliance officer and former general counsel, Stephen G. Juelsgaard, joined Genentech in 1985 from Wilson, and Kleiner Perkins Caufield & Byers, the Silicon Valley venture capital firm that's long been close to Wilson, was an early investor in Genentech. Korman advised Genentech on its 2007 purchase of Tanox Inc. for $919 million.

For banking, Roche is using Greenhill & Co.'s Robert Greenhill, Jeff Buckalew and Ashish Contractor, who also advised the company on the Ventana deal. Citigroup Inc. also represented Roche on that acquisition, and last March Greenhill hired Michael Giaquinto, who was co-head of Citigroup's U.S. healthcare group. Genentech's special committee tapped Paul Dawes, Peter Kerman and John Newell of Latham & Watkins LLP along with David Woodhouse and Marshall Smith at Goldman, Sachs & Co. Goldman is using Scott Barshay and James Woolery at Cravath, Swaine & Moore LLP.

The three-person special committee includes Herbert W. Boyer, Genentech's co-founder; Debra L. Reed, the CEO of San Diego Gas & Electric and Southern California Gas Co., both of which are units of Sempra Energy; and Charles Sanders, Genentech's lead director and the CEO of Glaxo Inc. from 1989 to 1995. Sanders, a former Harvard Medical School professor and director of Massachusetts General Hospital, is also chairman of the board at Icagen Inc., whose CFO, Richard Katz, was a Goldman banker from 1996 to 2001, and Sanders was on the board of Fisher Scientific Inc. when it agreed to combine with Thermo Electron Corp. Fisher used Goldman on the deal.