More than half of patients with lung cancer responded to an experimental drug from Amgen Inc. that targets a genetic driver of the disease previously considered impervious to treatment. The highest dose of Amgens AMG 510 shrank tumors in seven of 13 patients and the disease was stable in the remaining six. According to Bloomberg, nine remain in the study and are still taking the daily pill. The German News Agency reported that one patients cancer progressed after initially responding to treatment, while three others subsequently died, according to results presented at the World Conference on Lung Cancer in Barcelona. The findings show researchers may have identified a way to counter KRAS, a common gene in human tumors. The form of the gene targeted by AMG 510 occurs in about 13 percent of non-small cell lung cancers. Previously, finding a KRAS mutation could only be used to rule out treatment. "If we can expand this and show in a large body of patients that we have response rates on the order of 50 percent or somewhere near that, that is very clinically relevant and meaningful. The drug is still in its early days. We need to see if some of these responses will deepen over time,” Bloomberg quoted Dave Reese, Amgens head of research and development, as saying. Lung cancer kills 142,000 Americans each year.