NEW YORK ( TheStreet) - Japan's Otsuka Pharmaceutical Co. Ltd. announced an $886 million deal for oncology drug specialist Astex Pharmaceuticals Inc. to bolster its pipeline before the loss of a key patent. Otsuka,of Tokyo, said it would pay $8.50 per Astex share, a 27% premium to the shares' Tuesday close before rumors of a pending deal leaked. The stock gained 24% Wednesday. "I hope that this acquisition of Astex will strengthen not only our cancer portfolio but also our drug discovery research in the central nervous system field, through the acquisition of Astex's fragment-based drug design technology at its Cambridge, England, research headquarters and its California clinical oncology R&D department," said Otsuka president Taro Iwamoto in a statement. Astex, of Dublin, Calif., slipped to a second-quarter loss of $4.2 million, versus profit of $1.2 million in the same period a year earlier as it spent on research and failed to get royalties from a venture with MGI Pharma Inc. Revenue slid 17% to $16.6 million in the period. The agreement will help Otsuka defend against the loss of its patent on Abilify, a $4.5 billion-a-year antipsychotic drug, at the end of 2014. Otsuka's last major deal came two years ago when it launched a joint venture with Copenhagen-based H. Lundbeck A/S to develop and sell five psychiatric and neuroscience products. Lundbeck paid $200 million up front and may dole out as much as another $1.8 billion in royalties from drugs developed in the venture. They expanded the venture to include a new Alzheimer's treatment earlier this year. While two-thirds of Otsuka's sales are generated by its pharmaceuticals business, the company also has nutritional products, such as sports drinks and energy bars. The deal is just the latest in a long string of international acquisitions by pharmaceutical companies hoping to offset expiring patents -- and Japanese companies have played a key role, bolstered by a strong yen. Takeda Pharmaceutical Co. Ltd. in 2011 spent $12 billion on Switzerland's Nycomed International Management GmbH from a consortium of financial investors. It also spent $800 million on Philadelphia gout treatment maker URL Pharma Inc., which was also owned by financial investors.