Amgen Inc. has licensed three experimental cancer antibodies from Maryland drug developer Micromet Inc. in a deal that could be worth almost $1 billion.

The Thousand Oaks biotech giant, which is interested in the antibodies as treatments for solid tumors, on Monday said it has agreed to pay Rockville-based Micromet $14.3 million upfront then reimburse Micromet for research and development costs.

Micromet could get more than $487 million in payments if the drugs reach development milestones, get regulatory approval, and reach certain sales targets. In addition, there would be royalties on any sales and other payments for a total of $990 million.

Traditional chemotherapy drugs attack tumor cells and healthy cells at the same time, while Micromet’s approach has been developing therapies that train the immune system to target tumor cells and spare healthy cells.

Amgen shares closed down 74 cents, or 1.3 percent, to $56.90 on the Nasdaq.