Daiichi said the acquisition of the privately-held company will help it obtain co-promotion rights in the United States for the late-stage oncology drug PLX4032, which is being jointly developed by Plexxikon and Roche. The deal is the latest in a series of acquisitions for Japanese drug makers as they look to make the most of the strong yen and boost their presence in more lucrative markets overseas, offsetting limited domestic opportunities. Daiichi said it will spend $805 million to buy the Berkeley-based drug maker, which was set up in 2001 and employs around 45 people. Additional potential payments totalling approximately $130 million will be made based on near-term launch targets with respect to the approval of melanoma drug PLX4032. Daiichi shares closed 0.39 percent higher at 1,759 yen in Tokyo Tuesday. On Monday, Japan's Fujifilm, which has been diversifying into healthcare, said it would buy US and British biopharmaceutical companies from America's Merck for a reported half a billion dollars. Earlier in February pharmaceutical company Kyowa Hakko Kirin, a subsidiary of drinks giant Kirin Holdings, said it will buy Britain's ProStrakan Group PLC in a deal worth 292 million pounds ($475 million). And Astellas Pharma said it had agreed to pay around $1.3 billion to US drug developer Aveo Pharmaceuticals to jointly develop an experimental cancer treatment.