Predicting toxic drug effects in humans would go a long way toward helping doctors choose better courses of treatment for their patients and helping drug companies create better drugs, says In the Pipeline's Derek Lowe. DARPA is now soliciting proposals for the creation of a "toxicology chip," the idea being to "grow a variety of human cell lines in small, three-dimensional cultures, all on the same chip or platform, and test drug candidates across them," Lowe says. The DARPA request specifies that the cell cultures need to be able to interact with each other in a "physiologically relevant manner" to reproduce as closely as possible the inner workings of the human body. Lowe calls the project "a serious engineering challenge," adding that there are a lot of questions to get past, such as which cells to use. Even if it is possible, DARPA's five-year limit on the project is too short a time limit to get anything meaningful done, he says. "And I think that there's still no way that any system like this will catch everything, of course," Lowe adds. "A system sufficient to do that would be like building your own in vitro human, which is a bit out of our reach."