Plexxikon

About Plexxikon

Plexxikon was a biopharmaceutical company focused on the discovery and development of small molecule drugs to treat various human diseases. The company was founded in 2001 by Joseph Schlessinger, a professor of pharmacology at Yale University, and Sung-Hou Kim, a professor at the University of California, Berkeley. The firm operated with a distinct research and development model centered on its proprietary Scaffold-Based Drug Discovery™ platform. This platform utilized structural biology to guide the chemical design process, enabling the creation of targeted pharmaceuticals.

The company's business model was centered on building a pipeline of pharmaceutical products and forming strategic partnerships for development and commercialization. A key collaboration was with Roche for the co-development and co-promotion of its lead drug candidate. Plexxikon's primary therapeutic focus areas included oncology, central nervous system disorders, and autoimmune diseases. One of its most notable achievements was the development of Zelboraf® (vemurafenib), a targeted therapy for melanoma patients with a specific gene mutation. This drug, co-developed with Roche, gained FDA approval in 2011. Another significant product developed by the company is Turalio (pexidartinib), for treating tenosynovial giant cell tumors.

In a significant milestone, the Japanese pharmaceutical giant Daiichi Sankyo acquired Plexxikon in April 2011 for approximately $805 million, with an additional $130 million in potential milestone payments. Following the acquisition, Plexxikon continued to operate as an independent unit, retaining its name and facilities in Berkeley, California. However, in a strategic shift to focus on its antibody-drug conjugate (ADC) portfolio, Daiichi Sankyo announced the closure of the Plexxikon subsidiary, which took effect on March 31, 2022. The research pipeline and some employees transitioned, with some former assets and leadership forming a new company, Opna Bio, to continue the development of Plexxikon's research.