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Original research
Longitudinal effects of ivacaftor and medicine possession ratio in people with the Gly551Asp mutation: a 5-year study
  1. Ruth Marian Mitchell1,
  2. Andrew M Jones1,2,
  3. Katie Stocking3,
  4. Philip Foden4,
  5. Peter J Barry1,2
  1. 1 Manchester Adult Cystic Fibrosis Centre, Wythenshawe Hospital, Manchester University NHS Foundation Trust, Manchester, UK
  2. 2 Division of Infection, Immunity and Respiratory Medicine, School of Biological Sciences, The University of Manchester, Manchester, UK
  3. 3 Centre for Biostatistics, Division of Population Health, Health Services Research and Primary Care, The University of Manchester, Manchester, UK
  4. 4 Department of Medical Statistics, Manchester University NHS Foundation Trust, Manchester, UK
  1. Correspondence to Dr Peter J Barry, Manchester Adult Cystic Fibrosis Centre, Manchester University NHS Foundation Trust, Manchester, UK; peter.barry{at}mft.nhs.uk

Abstract

Introduction Ivacaftor was the first therapy licensed to address the underlying defect in cystic fibrosis (CF). The improvements in lung function, nutritional status and pulmonary exacerbations in patients carrying a Gly551Asp mutation were greater than previously seen in clinical trials for other therapies. Limited data are available regarding long-term outcomes and adherence to ivacaftor outside clinical trials.

Methods We conducted a 5-year single-centre retrospective study of people with CF carrying the Gly551Asp mutation who received ivacaftor. Clinical outcome data were extracted from medical notes and databases. Drug delivery data were used to assess medicine possession ratio (MPR).

Results 35 people were included. After commencing ivacaftor, FEV1 improved by 9.6% (SE±1.59%) predicted by 6 months. Thereafter, FEV1 declined, and at 5 years had returned to pre-ivacaftor baseline. Ivacaftor did not alter annual rate of FEV1 decline (1.57% pre vs 1.82% post, p=0.74). Body mass index (BMI) increased for 4 years. There was a significant reduction in inpatient and total intravenous antibiotic days sustained over 5 years. MPR remained high but declined over time (−2.5±0.9% per year, p=0.007). FEV1 was better maintained in patients with higher MPRs.

Conclusion The addition of ivacaftor provides acute benefits for people with the Gly551Asp mutation and established lung disease. We report a sustained reduction in intravenous antibiotic use but following acute improvement in lung function, decline continues, and patients will continue to require medical observation and optimisation. Strategies to maintain high adherence should be a priority to prolong the benefits of ivacaftor.

  • cystic fibrosis

Data availability statement

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Data availability statement

The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.

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Footnotes

  • Contributors RMM—study design, data collection, statistical analysis and writing of the manuscript. AJ—study design, manuscript writing. PF—statistical advice. KS—statistical advice. PB—study design, manuscript writing.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests PJB has received consultancy fees, lecture fees from Vertex pharmaceuticals; their institution has received a grant to organise an educational event and PJB is the local principal investigator on trials sponsored by Vertex pharmaceuticals. RMM, AMJ, KS and PF have no conflicts of interest to declare.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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