After a drawn-out battle, the Swiss drugmaker finally clinched a deal for the 44 percent of the U.S. biotech group it doesn't already own for $46.8 billion.

The deal is expected to be earnings-per-share-accretive in the first year after closing, Roche said in a statement, and the combined group will generate around $17 billion in annual revenues.

Roche's initial bid was rejected last year and the Basel-based company turned hostile after several months, during which the financial crisis raised doubts about financing and Genentech's shares fell below the offer price.

After meeting Genentech investors, Roche then decided to increase its offer to $45.7 billion to gain control of all revenues for big-selling cancer drugs Avastin and Herceptin, as well as absorbing an attractive portfolio of new medicines.

(Reporting by Katie Reid and Jason Rhodes; Editing by Hans Peters)