CoStim was a biotechnology company based in Cambridge, Massachusetts whose focus was cancer immunotherapy, that is, drugs that harnessed a patient’s own immune system. In particular, the company sought drugs that blocked the signals from cancer that shut down the immune response. One of the products the company worked on targeted the immune checkpoint molecule PD1. The company was involved in monoclonal antibody drug development.
CoStim was founded in 2012 by the venture capital firm MPM Capital as well as cancer researchers from the Dana–Farber Cancer Institute and Brigham and Women's Hospital. Later Atlas Venture also invested in the company.
CoStim was acquired by the major pharmaceutical company Novartis for an undisclosed sum in February 2014.