Amgen Inc. on Wednesday said it has completed its tender offer for shares of cancer therapy developer Micromet Inc., which it is buying for $1.16 billion.

The Thousand Oaks biotech giant said 84.7 million Micromet shares had been tendered as of midnight, which is about 88 percent of total shares. Amgen will buy additional shares directly from the Rockville, Md. company to bring its ownership up to at least 90 percent.

Amgen in January agreed to buy Micromet for $11 a share, a 33 percent premium to the stock’s closing price the day before the deal was announced. Micromet stock will stop trading on the Nasdaq after the markets close this afternoon.

The deal bolsters Amgen’s drug pipeline. Micromet, which becomes a subsidiary, is developing an experimental antibody-based drug called blinatumomab. Antibody drugs work with the body’s immune system to kill cancer cells.

Amgen shares were up 52 cents, or less than 1 percent, to $67.06 in midday trading on the Nasdaq.