In a report that appears in the journal Nature as an advanced online publication, researchers describe one of the first studies to demonstrate the value of “co-clinical” trials, in which drugs targeting cancers with specific genetic mutations are tested simultaneously in patients and in lab animals with the same type of tumor. The arrangement enables investigators to use information from the animal studies to predict how specific patients will respond to the drugs, and to design follow-up trials in which the drugs undergo more extensive testing in patients. The Nature paper focused on non-small cell lung cancers that carry a mutation in the gene Kras. By conducting a mouse study that paralleled a human clinical trial, researchers found that a two-drug therapy shrank lung cancer tumors in mice with one set of mutations but not another. The findings may help scientists understand why some human patients respond to the drugs while others don’t.