Japanese drugmaker Daiichi Sankyo Co Ltd has agreed to acquire U.S. biopharmaceutical company Ambit Biosciences Corp in a deal valued up to $410 million as it looks to build its presence in oncology, the companies said.

The companies said in a joint statement that Daiichi Sankyo would acquire all outstanding common stock of San Diego-based Ambit Biosciences for $15 per share in cash through a tender offer, or about $315 million, and merge it with a subsidiary of Daiichi Sankyo. Ambit shares closed at $8.20 on Friday.

Ambit Biosciences shareholders will also be eligible for an additional cash payment if certain milestones are reached, which would bring the total transaction to $410 million on a fully diluted basis, they said.