Conventional antibodies, by contrast, don't directly recruit T cells. "Unleashing the killing power of the T cell directly on the tumor cells allows a large increase in potency of these antibodies," said Dr. David Scheinberg, chairman of molecular pharmacology at Memorial Sloan Kettering Cancer Center. Investor excitement over these therapies have helped boost interest from companies including Amgen Inc and Roche and have fueled a jump in share prices of smaller firms such as Kite Pharma Inc, Juno Therapeutics and Bluebird Bio. "We take patients that have failed every treatment, every chemo combination, that have just two to six months to live. You give them a CAR, and within 3 to 4 weeks you can see massive tumors melting away," said Arie Belldegrun, chief executive officer of Kite. The company went public in June and announced a partnership with Amgen earlier this month.