Amgen Inc. on Thursday announced the preliminary results of its $5 billion share buy-back, saying it will purchase around 83.3 million shares at $60 a share.

The Thousand Oaks biotech, which closed its tender offer on Wednesday, will retire about 9.5 percent of its outstanding stock – but at a premium.

Shares were trading at $55 when the buyback was announced Nov. 7, and Amgen had previously agreed to pay between $54 and $60 a share through a modified Dutch auction. The process allows shareholders to say how much stock they wish to sell back and at which price within a specified range.

The purchase, which totals nearly $5 billion, will use up about half of the company’s $10 billion current buyback authorization from the board.

Shares of Amgen closed up 6 cents, or less than 1 percent, to $58.40 on the Nasdaq.