VX770

Question

I know although VX770 is probably soon to be licensed it is still very early days. However, what I have read is that this should considerable help a CF patient with G551 gene. PRESUMING this medication opens the 'gate' it is said that although not a cure this should control CF in the same way that Insulin controls Diabetes. Again PRESUMING this works as hoped should this keep CF under control? I am also confused as if a person only has one CF gene then they do not have CF. Therefore if a person with for example the common gene and G551 should this still control the CF? Also if this medication works as forcast by Vertex and together with the combined medication for F508 Delta when eventually available are we hopefully looking at the majority of people with CF will live normal lives although not cured and in time require much less 'physio etc. as at present? I look forward to your reply. With thanks.

Answer

Thank you for your excellent question. The drug developed for the G551D mutation is called ivacaftor and it was previously called VX770. Full details are now available in a paper recently published in the New England Journal of Medicine. You are correct that the drug ivacaftor has now gone forward for approval. Ivacaftor has indeed shown benefit to patients with the G551D mutation, in outcome measures such as lung function and weight gain, however long-term effects of the drug are still to be established.

You ask in particular about the effect of ivacaftor on patients with the “common gene” (presumably delF508) and G551D. Indeed many patients in the ivacaftor trials have had this combination of mutations and have shown benefit. Ivacaftor has been shown to work only in G551D mutations with another disease causing mutation on the other chromosome. Additionally, there is no clinical benefit shown for people with other mutations and should not be used unless one mutation is G551D.

You also ask about the combination therapy that is currently being investigated (ivacaftor in combination with VX-809). Some results from a Phase II study (short term study assessing safety and efficacy) are now available which show some effect on sweat chloride. Further long term studies are required to ascertain if there is also an effect on symptoms and course of disease. We are optimistic that the further studies on this combination therapy will be undertaken in a timely manner.

NEJM 2011: 365; 18

Best wishes
Lisa Kent, Belfast
Stuart Elborn, Belfast

12.01.2012

The answer is edited by: PhD Lisa Kent