Cystic fibrosis is the most common genetic disease affecting Australians.

The recent approval of cystic fibrosis drugs (namely lumacaftor or tezacaftor) combined with the break-through drug ivacaftor targets the majority of patients with cystic fibrosis.
 
Unfortunately, the clinical outcome of these important combination drugs has been limited by our limited understanding of the way these drugs move (pharmacokinetics) and work (pharmacodynamics) in the human body.
 
Two new studies by Davies et al and Keating et al evaluate the patients’ improvement in health as well as safety of two new drugs – VX-445 and VX-659 – for the treatment of majority of adult cystic fibrosis patients who were already given standard therapy of tezacaftor and ivacaftor.  The trial showed that four weeks of the triple combination instead of the double combination yielded better outcomes in patient health and possibly long-term life expectancy. In the past, tremendous progress has been achieved in the treatment of CF. Targeting the mutant CFTR has proved effective in a limited number of patients.
 
The triple combinations represent promising breakthrough treatment strategies that cystic fibrosis patients have been waiting for. However, the long-term benefits will require further clinical and pharmacological assessment.  We are all hopefully awaiting the results of the ongoing long-term studies for these two new revolutionary drugs.

CF is the most common of the rare genetic disorders. There are around 3,000 people in Australia with CF. Patients typically have poor quality of life and reduced life expectancy because of effects the disease has on their lungs.

These studies are the latest in a series of clinical trials designed to test the effects of what are called “modulator therapies”. These are a class of drugs (others include Kalydeco, Orkambi and Symdeko) that can assist the CF ion channels to function correctly. Unlike Kalydeco, which works for about 10 per cent of the Australian CF population, this new combination of drugs should be applicable to 90 per cent of the CF population.

The improvements they saw in these clinical trials were impressive, even more so considering a group of patients were already receiving an existing modulator therapy. While it’s great to see lung function improvements, importantly the patients on the new drug also recorded improvements in their quality of life, suggesting these therapies can have a huge impact for patients.

This phase II trial was designed to assess safety, so it will be interesting to see how people with CF go in phase III trials. Some patients did have adverse events, highlighting that these therapies are not suitable for all CF patients. Ensuring that the final 10 per cent of patients are not left behind is also important, so approaches such as gene and cell therapies are still really important areas of CF research.

The cost of these pharmaceutical therapies remains an important consideration, and this will need to be assessed in the future by the PBAC.