UPDATE 1-Gilead to buy back up to $1 billion in stock

* Gilead authorizes $1 bln share buyback through Jan. 2011

* Timing will depend on price, corporate, market (Updates with timing, details)

BOSTON Jan 29 (Reuters) - Biotechnology company Gilead Sciences Inc (GILD.O), a leading developer of drugs to treat HIV, said on Friday it has authorized the repurchase of up to $1 billion of its shares through January 2011.

Gilead, which is considered by analysts to be one of the most well-run companies in the sector, said the repurchases may be made in the open market or in privately negotiated transactions.

On Tuesday the company reported a stronger-than-expected increase in its fourth-quarter earnings as sales of its HIV drugs and royalties on sales of the flu drug Tamiflu. (Reporting by Toni Clarke, editing by Gerald E. McCormick)