Study Results

• What We Learned:

  In people with CF already taking ivacaftor, a once daily dose of VX-561 (250 mg) was determined to result in a small additional reduction of sweat chloride (-6.5 mmol/L) and a small additional improvement in lung function, as measured by FEV1 (+2.7 percentage points) than the ivacaftor control group taken twice daily.  The safety profile of VX-561 was also similar to ivacaftor.  Based on these results, Vertex has replaced ivacaftor with VX-561 (250 mg) in new studies of triple combination CFTR modulators to enable once per day dosing.

• Primary Findings:

  Effectiveness:

  Overall, the study enrolled 77 participants between May 2019 and April 2020.  All participants were required to be receiving ivacaftor clinically at the start of the study; thus those participants randomized to continue receiving ivacaftor (ivacaftor control) were not expected to see changes in sweat chloride or FEV1.  The two lower doses of VX-561 (25 and 50 mg) were discontinued early by the sponsor and only the 150 mg and 250 mg doses VX-561 were included in analyses of efficacy.   After 12 weeks of dosing, both the 150 mg and 250 mg doses of VX-561 resulted in slightly improved lung function, as measured by FEV1 ( +3.1 and +2.7 percentage points respectively) compared with the ivacaftor control (-0.8 percentage points). The 250 mg dose of VX-561 resulted in the greatest reduction in sweat chloride (-6.5 mmol/L) compared with an increase of 3.3 mmol/L for the 150 mg VX-561 dose and 0.9 mmol/L for the ivacaftor control.

   

  Safety:

  Both the 150 mg and 250 mg doses of VX-561 were generally safe and well-tolerated. Similar to what has been seen for ivacaftor, one participant in the 250 mg dose group experienced elevated liver enzymes.

• Citation:

For current information about the overall development status of this drug, please check the Drug Development Pipeline.