Shares of San Diego-based Tracon Pharmaceuticals Inc. (NASDAQ:TCON) fell 49% to 66 cents Friday as the company decided to quit testing its lead candidate, carotuximab (TRC-105), in cancer. The decision followed advice from independent experts who saw no likely benefit from combining the drug with Votrient (pazopanib, Novartis AG) in the phase III advanced angiosarcoma trial called Tappas.