Daiichi Sankyo Completes Plexxikon Acquisition

Plexxikon to Continue as Independent Unit of Daiichi Sankyo

Berkeley, CA—April 4, 2011

Plexxikon Inc. today announced that its acquisition by Daiichi Sankyo Company, Limited, a Japan-based global pharmaceutical company, has been successfully completed. Clearance under the Hart Scott Rodino Antitrust Improvements Act has been received. Under the terms of the deal, Plexxikon shareholders will receive $805 million up-front, with near-term milestone payments associated with the approval of PLX4032 totaling an additional $130 million. Plexxikon will retain its name, employees and facilities in Berkeley, CA, and continue research and development operations as an independent unit of Daiichi Sankyo.

Plexxikon’s lead program is PLX4032 (vemurafenib), an oral, novel drug that targets the oncogenic BRAF mutation present in about half of melanoma cancers and about eight percent of all solid tumors. Earlier this year, Plexxikon reported that interim data from a Phase 3 controlled study of PLX4032 in previously untreated metastatic melanoma patients with the BRAF mutation met both co-primary endpoints of overall survival and improved progression-free survival.

The company and its co-development partner, Roche, plan to file for market approval in the U.S. and Europe this year, along with a filing for the companion diagnostic also being co-developed by the partners. Daiichi Sankyo will co-promote PLX4032 in the U.S., along with Roche’s U.S. commercial oncology unit, Genentech. Roche retains commercial rights outside the U.S.

In addition to PLX4032, Plexxikon has a pipeline of additional products in development and pre-development, including multiple agents to treat cancer. PLX3397 is an oral, selective kinase inhibitor co-targeting Fms, Kit and Flt3-ITD, and is currently being tested in Hodgkin lymphoma in a Phase 2 trial. Plexxikon plans to initiate several other Phase 2 trials with PLX3397 this year, including in AML, glioblastoma and metastatic breast cancer. Additionally, the company recently initiated a Phase 1 study for PLX5622, an oral agent directed to the treatment of rheumatoid arthritis.

Daiichi Sankyo Group, based in Tokyo, is dedicated to the creation and supply of innovative pharmaceutical products to address the diversified, unmet medical needs of patients in both mature and emerging markets.

About Plexxikon

Plexxikon Inc., a unit of Daiichi Sankyo Company, Limited, is a leader in the structure-guided discovery and development of novel small molecule pharmaceuticals to treat human disease. The company is developing a portfolio of clinical and preclinical stage compounds to address significant unmet medical needs in oncology, as well as cardio-renal disease, CNS disorders, autoimmune and neuro-inflammatory diseases. Plexxikon’s proprietary Scaffold-Based Drug DiscoveryTM platform integrates multiple state-of-the-art technologies, including structural screening as a key component that provides a significant competitive advantage over other drug discovery approaches. For more information, please visit www.plexxikon.com.

Contacts:

Kathleen Sereda Glaub
President
Plexxikon Inc.
+1 (510) 647-4009
kglaub@plexxikon.com  

For Plexxikon
Susan Kinkead
+1 (415) 751-3611
susan@kinkeadcomm.com

or

Jennifer Cook Williams
+1 (360) 668-3701
jennifer@cwcomm.org