Thousand Oaks-based Amgen is buying a leukemia drug maker for $1.2 billion in a bid to boost its blockbuster drug lineup.

Amgen, the world’s largest biotech company, said Jan. 26 that it will purchase Maryland-based Micromet, maker of an experimental leukemia drug. Investors of Microment will receive $11 a share in cash.

Micromet currently has no drugs on the market. The deal, Amgen’s largest since 2005, would give the Thousand Oaks company the compound blinatumomab, which is being tested against the blood cancers such as acute lymphoblastic leukemia and non-Hodgkin’s lymphoma. It would also give Amgen an experimental new addition to its drug pipeline, which is threatened by biosimilars, the biotech industry’s equivalent of generic pharmaceuticals.

The two companies road-tested their merger in July, when Micromet agreed to license three anti-bodies to Amgen in a deal then valued at $990 million.

“The acquisition of Micromet is an opportunity to acquire an innovative oncology asset with global rights and a validated technology platform with broad potential clinical applications,” Amgen CEO and Chairman Kevin Sharer said in a statement.

With $15 billion in annual sales and a market capitalization of $60 billion, Amgen is one of the largest drug makers in the world. But it has struggled in recent years to find new blockbuster drugs. Its only megahit in the last five years has been denosumab, an osteoporosis treatment.

In 2011, after years of consistent profits but lackluster stock performance, the company set in place its first dividend payment. Late in the year, Amgen cut 380 research and development jobs – the majority at its Ventura County headquarters – and issued a $5 billion share buyback.

The company also set aside $780 million to settle federal and state charges that it engaged in an illegal kickback scheme, though the settlement is not yet final. And Sharer, the company’s longtime CEO, announced his retirement last year. Robert Bradway, the current chief operating officer and president, will replace him in May.

Micromet would be the Amgen’s largest acquisition since the Thousand Oaks-based firm bought Abgenix for $2.2 billion in cash in 2005.

Under the terms of the deal, Amgen will buy Micromet in two phases. A subsidiary of Amgen would acquire all of the outstanding shares of Micromet’s common stock for $11 per share in cash. The parent company will then buy any remaining shares at the the same price.

The deal is expected to close in the first quarter, Amgen said, and will be further discussed in its fourth-quarter earnings call slated for after the markets close on Thursday.

Amgen’s shares slipped 2.1 percent to $67.81 in mid-morning trading after the Micromet announcement.