Factbox: Testing 'safety switches' for CAR T cancer therapies

By Ransdell Pierson NEW YORK (Reuters) - Drugmakers are building safety "switches" that can be used to turn off powerful cancer therapies known as CAR T cells when they cause life-threatening inflammation or attack healthy tissue. Conversely, they can be used to boost activity of the engineered T cells against tough solid tumors. Several biotechnology companies are beginning to test such switches in clinical trials. Below are details of their plans: * Bellicum Pharmaceuticals Inc has developed a "switch" by genetically programming a CAR T cell to kill itself when exposed to a drug called rimiducid, originally used to control cells modified by gene therapy. Rimiducid, a pill, is given to patients if they develop life-threatening side effects. The company aims in 2016 to begin a trial of BPX-401, a CAR T cell for leukemias and lymphomas that targets a protein called CD19 found on the surface of blood cancer cells. The therapy will come equipped with the switch. * Ziopharm Oncology Inc plans trials this year on a handful of CAR T cell therapies. At least one of the treatments would incorporate a switch meant to work like a rheostat - either accelerating or decreasing activity of the CAR T cell as desired. Developed by Intrexon Corp, the switch is controlled by veledimex, a drug developed to stimulate the immune system. * Juno Therapeutics Inc has built safety switches into at least two of its experimental CAR T cells, including JCAR014 for patients with advanced leukemias. * Kite Pharma Inc, a leader in the emerging CAR T cell field, says it has decided against using suicide switches until it better understands its CAR T cells. * Bluebird Bio Inc and Swiss drugmaker Novartis AG, other major players in the CAR T cell field, have not disclosed whether they are working on switches. * Cellectis SA is developing a switch that is activated by Rituxan, an infused cancer drug from Roche Holding AG. The company's CAR T cell treatment program, partnered with Pfizer Inc, is considered behind Bellicum and Intrexon. (Reporting by Ransdell Pierson, editing by John Pickering)