Three months ahead of schedule, the FDA approved Kalydeco (ivacaftor), a new cystic fibrosis drug from Vertex Pharmaceuticals Inc., of Cambridge, Mass. The drug targets the G551D mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene in cystic fibrosis, which affects about 4 percent of patients with the disease, or about 1,200 patients in the U.S.