Enlarge Image Vulnerable. A new type of drug blocks a tumor cell's shield (left) against T cells (knights) so that they can attack. Credit: Ryan Snook, www.ryansnook.com A type of drug that helps the body's immune system attack tumors is showing promise. In early clinical trials involving several hundred patients with various kinds of advanced cancer, up to one-quarter of those who received the treatment saw their tumors shrink, and some are still alive more than a year later. The results are the latest good news for so-called immunotherapy treatments that work by overcoming a tumor's ability to evade...