DOVER, Del. (AP) — A Delaware judge has refused to delay the acquisition of Micromet Inc. by Amgen Inc., the world’s largest biotech company. The judge ruled that Micromet shareholders have not shown that the deal is unfair or that they are getting an inadequate price.

Amgen, based in Thousand Oaks, Calif., announced in January that it agreed to buy Rockville, Md.-based Micromet, a developer of cancer therapies, in a billion-dollar deal that would give Amgen Micromet’s experimental antibody-based drug blinatumomab.

Amgen’s tender offer of $11 per share was to expire at midnight Thursday.

Some Micromet shareholders challenged the deal, arguing at a hearing earlier this week that Micromet’s board rushed it through and did not adequately explore whether it could get a competing offer at a better price.

They also argued that the acquisition included unreasonable deal-protection measures aimed at thwarting potential competing bids, and that the Micromet board did not disclose “upside” financial projections that might have warranted a higher price.

“They pushed it though. There was almost no market check,” said Jason Leviton, an attorney for the shareholders.

In a ruling filed late Wednesday, Vice-Chancellor Donald Parsons said the Micromet shareholders were not entitled to a preliminary injunction because they had not shown a reasonable likelihood that they would succeed in proving that the deal was unfair and that Micromet directors breached their fiduciary duties, including their disclosure obligations.

Parsons noted that Micromet shareholders will receive a significant premium for their shares compared to the pre-announcement share price. He also said the deal was the result of a reasonable sale process and approved by an independent and disinterested board.

Micromet shares closed at $11 on Thursday. When it was announced in January, the $11-per-share offer represented a premium of 33 percent over the previous day’s closing price. Over the past year, Micromet shares traded as low $4.13.

Amgen shares fell 42 cents on Thursday to close at $67.59.

Micromet attorney Koji Fukumura argued at a Monday hearing that Amgen’s offer represented “an incredible premium” for Micromet shareholders.

Fukumura and Amgen attorney Robert Sacks also noted that Micromet had reached out to seven pharmaceutical companies, most of them aware of Micromet’s technology, but none expressed interest in making a competing bid.