Flexus Biosciences

About Flexus Biosciences

Flexus Biosciences operated as a biopharmaceutical firm with a sharp focus on the immuno-oncology sector, a market it entered upon its founding in 2013. The company was established by Terry Rosen and Juan Jaen, two seasoned professionals in drug discovery who had previously collaborated at Tularik. Their shared history, which began as students at the University of Michigan and continued through Tularik's acquisition by Amgen, formed the foundation of their partnership at Flexus. Rosen remained at Amgen for nearly a decade, ultimately serving as VP of Therapeutic Discovery, while Jaen took on the role of Chief Scientific Officer at ChemoCentryx before they reunited to launch Flexus.

The company's core business was the discovery and development of small-molecule therapeutics designed to counteract tumor immunosuppression. Flexus targeted enzymes like IDO1 (indoleamine 2,3-dioxygenase 1) and TDO (tryptophan 2,3-dioxygenase), which are exploited by cancer cells to create a microenvironment that suppresses the body's T-cell immune response. By inhibiting these enzymes, Flexus's drug candidates aimed to restore the immune system's ability to identify and attack tumors. This strategy involved creating a portfolio of IDO-selective, TDO-selective, and dual IDO/TDO inhibitors. The primary client for this technology was large pharmaceutical companies looking to expand their immuno-oncology pipelines, particularly for use in combination therapies.

A significant milestone for Flexus was its rapid trajectory from inception to a major acquisition. After securing $38 million in venture funding from prominent investors including Kleiner Perkins Caufield & Byers, The Column Group, and Celgene, the company advanced its lead preclinical candidate, F001287, an IDO1 inhibitor. This progress culminated in a landmark event in February 2015, less than two years after its founding, when Bristol-Myers Squibb announced its agreement to acquire Flexus. The acquisition, completed in April 2015, was valued at a potential $1.25 billion, comprising an $800 million upfront payment and up to $450 million in development milestones. The deal granted Bristol-Myers Squibb full rights to F001287 and the entire IDO/TDO discovery program, while assets not related to IDO/TDO were spun out into a new entity by the Flexus shareholders.