A decade ago, Daiichi-Sankyo (TYO:4568) announced its plan to acquire small molecule pharmaceutical specialist Plexxikon for $935 million. Now, the company has announced a reorganization of its R&D structure that involves closing the R&D subsidiary Plexxikon on March 31, 2022. Plexxikon has approximately 60 employees. The unit was instrumental in developing two commercialized drugs, Zelboraf…