A new treatment approach for patients with the most common form of cystic fibrosis could be on the horizon after Vertex filed its promising therapy in the US and Europe.

The group’s fully co-formulated combination of lumacaftor and ivacaftor has been developed by the firm for patients aged 12 years and older who carry two copies of the F508del mutation.

The regimen is the first to target the underlying cause of CF in people with two copies of this mutation, the most common form of the disease, affecting around 8,500 (over 12’s) in the US and 12,000 in Europe.

The submissions are based on Phase III data released in April showing mean absolute improvements in lung function (percent predicted forced expiratory volume in one second, or ppFEV1) of between 2.6 and 4.0 percentage points from baseline versus placebo, with mean relative improvements of 4.3% to 6.7%.

If this effect is sustained long-term it could make a real difference to patents, given that, on average, those with two copies of the F508del can currently expect to lose nearly two percent of their lung function each year, the firm said.

In the US, the lumacaftor/ivacaftor combo has received Breakthrough Therapy Designation and Vertex is seeking a priority review of its application to shorten the review time from around 12 to eight months. An accelerated review has already been granted in Europe.