One week after Vertex Pharmaceuticals initiated its first Phase 3 study of VX-659 (tezacaftor and ivacaftor) regimen for people with cystic fibrosis, the company has announced it is initiating a second clinical study.

Last week’s announcement came on the heels of Vertex initiating the investigational triple combination for 360 people with CF who have one F508del mutation and one minimal function mutation. The latest study to be initiated intends to enroll 100 patients with two copies of the F508del mutation. Two copies of the F508del mutation is the most common genetic variation of CF.

The study’s primary endpoint is the mean absolute change from baseline in percent predicted forced expiratory volume in one second (ppFEV1) at week four of treatment.