Combining two types of cystic fibrosis drugs may cancel out the benefits of one of the medications. In cultures of human cells, ivacaftor, the cystic fibrosis drug sold under the trade name Kalydeco, may destabilize proteins. These proteins are disease-related and are targeted and corrected by drugs such as lumacaftor, two teams report July 23 in Science Translational Medicine. The findings contrast with positive results recently released from one of the two large clinical trials that combine ivacaftor and lumacaftor.