The US Food and Drug Administration last week approved Vertex Pharmaceuticals' Kalydeco (ivacaftor) for cystic fibrosis patients six and older who harbor one of eight mutations in the CFTR gene.
The FDA first approved Kalydeco in late 2012 for cystic fibrosis patients six and older who have at least one copy of the G551D mutation. In addition to this mutation, the drug is now approved for cystic fibrosis patients who have the G178R, S549N, S549R, G551S, G1244E, S1251N, S1255P and G1349D mutations.
In the US, there are 30,000 people with cystic fibrosis. Approximately 4 percent of cystic fibrosis patients harbor the G551D mutation. Vertex estimates that 150 people ages six and older have one of the additional eight mutations that Kalydeco is now indicated to treat.
Mutations in the CFTR gene result in defective or missing proteins that cause cystic fibrosis, a disease that is characterized by a buildup of sticky mucus that becomes infected and hinders breathing. Kalydeco helps normalize CFTR protein function in people harboring the G551D and these other eight mutations.
The FDA granted Vertex Breakthrough Therapy designation for Kalydeco in late 2012. As part of the latest supplementary NDA, the company submitted data from a two-part, randomized, Phase III, cross-over trial involving 39 cystic fibrosis patients who had one of nine mutations: G178R, S549N, S549R, G551S, G1244E, S1251N, S1255P, G1349D or G970R.
Vertex showed in this study that Kalydeco treatment significantly improved lung function (FEV1) in patients and adverse events associated with the drug in these patients were similar to how patients with the G551D mutation reacted to the drug in earlier studies.
"Based on data from four patients with the G970R mutation enrolled in the study, the efficacy of Kalydeco in patients with the G970R mutation could not be established to support approval in the U.S," the company said. Worldwide, Vertex estimated that less than a dozen cystic fibrosis patients have the G970R mutation, including two patients in the US.
Vertex has submitted data from the same study to expand Kalydeco's indication in Europe, Canada, and Australia. The company estimates that in Europe and Australia an additional 250 cystic fibrosis patients have these eight other mutations.