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Clinical management of CF » CFTR modulators » CFTR modulators approved » Ivacaftor clinical trials

Ivacaftor clinical trials

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Phase III studies have been completed in adult and paediatric people with CF who have at least one copy of the G551D mutation in their CFTR gene. A summary of the pivotal trials (STRIVE1 and ENVISION2) is given below.

STRIVE: Phase 3 Study Design

Key inclusion criteria:

  • G551D mutation on at least one CFTR allele
  • Aged ≥12 years
  • FEV1 of 40 to 90% of the predicted value

STRIVE: Study endpoints

Primary endpoint:

  • Absolute change from baseline to week 24 in the percent of predicted FEV1

Secondary endpoints:

  • Change from baseline through week 48 in the percent of predicted FEV1
  • Time to first pulmonary exacerbation through week 24
  • Patient reported respiratory symptoms through week 24 and week 48
  • Change in weight from baseline to week 24 and week 48
  • Change from baseline in the concentration of sweat chloride through week 24 and week 48

STRIVE: FEV1% Predicted Absolute Change from Baseline

There was a sustained improvement lung function as measured by the the Forced Expiratory Volume in 1 second (FEV1)

STRIVE: Change from Baseline in Sweat Chloride

The average sweat chloride level was reduced to values below the diagnostic threshold for cystic fibrosis1

STRIVE: Change in CFQ-R Respiratory Domain Score (points)*

Patients with CF experienced improved quality of life
* Cystic Fibrosis Questionnaire Revised (CFQ-R) is a questionnaire designed to measure impact on overall health, daily life, perceived well-being and symptoms

STRIVE: Change from Baseline in Weight

The marked weight gain suggests improved nutrient absorption

STRIVE: Time-to-first Pulmonary Exacerbation

Patients treated with ivacaftor were 55% less likely to experience a pulmonary exacerbation through week 48

STRIVE: Safety Summary Through Week 48


According to the study, daily oral administration of ivacaftor over 48 weeks was not associated with a greater safety risk than that observed with placebo

STRIVE: Conclusions

Lung function improvements were rapid in onset and sustained throughout the 48 weeks.
There were sustained improvements in:
  • Weight gain
  • Respiratory systems
  • Risk of exacerbation
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  1. B Ramsey et al. NEJM 365:1663-72 (2011)