A therapy that replaces the faulty gene
responsible for cystic fibrosis in patients' lungs has produced
encouraging results in a major UK trial.
Credit: © iQoncept / Fotolia
For the first time gene therapy for cystic
fibrosis has shown a significant benefit in lung function compared with
placebo, in a phase 2 randomised trial published in The Lancet Respiratory Medicine
journal. The technique replaces the defective gene response for cystic
fibrosis by using inhaled molecules of DNA to deliver a normal working
copy of the gene to lung cells.
"Patients who received the gene therapy showed a significant, if
modest, benefit in tests of lung function compared with the placebo
group and there were no safety concerns," said senior author Professor
Eric Alton from the National Heart and Lung Institute at Imperial
College London. "Whilst the effect was inconsistent, with some patients
responding better than others, the results are encouraging."
Cystic fibrosis is a rare inherited disease caused by mutations in a
single gene called cystic fibrosis transmembrane conductance regulator
(CFTR) and affects 1 in every 2500 newborns in the UK and over 90000
people worldwide. Scientists have discovered around 2000 CFTR mutations
so far. These mutations make the lining of the lungs secrete unusually
thick mucus. This leads to recurrent life-threatening lung infections,
which result in lung damage that causes 90% of deaths in people with
cystic fibrosis.
Since the discovery of the genetic basis for cystic fibrosis in 1989,
scientists have developed a variety of viral and non-viral vector
systems for delivering a corrected CFTR gene back into lung cells.
Despite expectations of a rapid breakthrough, no cystic fibrosis gene
therapy trial so far has been able to show long-term clinical
improvement.
Coordinated by the UK Cystic Fibrosis Gene Therapy Consortium, the
two-year study involved 136 CF patients aged 12 years or older from
across the UK. Participants were randomly assigned to either 5ml of
nebulised (inhaled) pGM169/GL67A (gene therapy) or saline (placebo) at
monthly intervals over 1 year. Lung function was evaluated using a
common clinical measure of the volume of air forcibly exhaled in one
second (FEV1).
After a year of treatment, in the 62 patients who received the gene
therapy, FEV1 was 3.7% greater compared to placebo.* This was a result
of stabilisation of respiratory function rather than an improvement.
However, the effects were inconsistent, with some patients responding
better than others. In particular, in the half of patients with the
worst lung function at the start of the study, there was a doubling of
the treatment effect, with changes in FEV1 of 6.4%.
Overall, the gene therapy was well tolerated and patients in the
treatment and placebo groups experienced similar rates of adverse
events.
According to senior co-author Professor Stephen Hyde from the Gene
Medicine Research Group at the University of Oxford, "Stabilisation of
lung disease in itself is a worthwhile goal. We are actively pursuing
further studies of non-viral gene therapy looking at different doses and
combinations with other treatments, and more efficient vectors."
Senior co-author Dr Alastair Innes from Western General Hospital,
Edinburgh, UK adds, "Publication of this trial is a landmark for cystic
fibrosis patients and we are particularly grateful to the many patients
across the UK who gave their time and effort to participate and make
this collaborative venture a success."
This study was funded by a partnership between the UK Medical
Research Council (MRC) and the National Institute for Health Research
(NIHR).
*The 95% confidence interval for the effect size is 0.1% to 7.3%.
Thus, although the best estimate of the effect size is 3.7%, the data
are consistent with the true effect size lying anywhere in the range
0.1% to 7.3%. This interval straddles values from no effect to clear
clinical relevance.
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The above post is reprinted from
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