An experimental Amgen Inc drug that targets a specific genetic mutation reduced tumor size in around half of advanced lung cancer patients given the highest dose in a small, early-stage trial, the company said on Sunday. Out of 13 lung cancer patients taking a 960-milligram dose of AMG510, seven had tumors shrink by at least 30%, according to data presented in Barcelona at the World Conference on Lung Cancer. Cancer was stabilized in the other six high-dose patients. Nine of the 13, or 69%, are still taking the daily pill. Two of the partial responders have died, and another left the study due to cancer progression. One patient with stable disease also died.