Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA; Department of Pediatrics, Division of Pulmonary and Sleep Medicine, UAB, Birmingham, AL, USA. Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA; Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, UAB, Birmingham, AL, USA. CFF Therapeutics Development Network Coordinating Center, Seattle Children's Research Institute, Seattle 98105, WA, USA. CFF Therapeutics Development Network Coordinating Center, Seattle Children's Research Institute, Seattle 98105, WA, USA; Department of Pediatrics, Division of Pulmonary and Sleep Medicine, University of Washington, Seattle, WA, USA. Cystic Fibrosis Foundation, Bethesda, MD, USA. Department of Pediatrics, Children's Hospital Colorado, University of Colorado School of Medicine, Aurora, CO, USA. Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), Birmingham, AL, USA; Department of Pediatrics, Division of Pulmonary and Sleep Medicine, UAB, Birmingham, AL, USA; Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, UAB, Birmingham, AL, USA. Electronic address: smrowe@uab.edu.