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Since the discovery of the mutated CFTR gene in cystic fibrosis patients, scientists have been working on the development of gene therapy for this patient group. Recently, a gene therapy phase II clinical trial with 116 participants in the UK resulted in the halt of disease progression, although there was little effect. The article was published in The Lancet.

Cystic fibrosis (CF) is caused by the mutation of a chloride channel in mucus cells. It leads, among other things, to the production of thick mucus blocking the airways. The gene therapy places an intact CFTR gene in the cell nucleus which is subsequently translated into a functioning chloride channel and should therefore relief the symptoms of CF.

In the randomised, double-blind trial, patients were treated with 5 ml of a nebulised pGM169/GL67A gene-liposome complex or a saline solution every 28 days during a period of one year. The primary outcome was defined as the difference in lung function measured as FEV₁ before and after the treatment.

The resulting difference in lung function decline was small (-4% in the placebo group vs. -0.4% in the gene therapy group) but significant, and was most evident in patients with more severe disease. Professor Eric Alton, first author and coordinator of the UK Cystic Fibrosis Gene Therapy Consortium, points out: “It is the world’s first demonstration that repeated gene therapy can improve lung function.” Furthermore, the gene therapy was well tolerated.

However, the treatment still needs some fine-tuning. “The effects were modest and variable. This is not yet ready for clinical use”, says Alton. To improve the treatment response, the next steps will include the testing of higher dosages and the administration of the CFTR gene through virus particles instead of liposomes (fat particles) that were used for this trial.

Sources: The Guardian, The Lancet

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