I'm still trying to find a list of mutations considered as "nonsense mutations". I believe 80% of all CF cases are due to dd508 (can't remember where I heard that...) so it would seem that the 10% mentioned in this article as "nonsense" may apply to many others that have alternate mutations, thus the drug may help. As noted, it's in phase 2 trials.
Here is an excerpt...
A No-Nonsense Cure for Cystic Fibrosis
Wednesday July 23, 2008
PTC Therapeutics, the pharmaceutical company that is in phase 2 testing of a promising new drug called PTC124, got a shot in the arm last week when Genzyme Corporation bought in to a deal to partner with PTC in marketing the drug once it receives FDA approval.
PTC124 targets a group of mutations known as nonsense mutations, in which a piece of code that appears in a gene stops the gene from performing its function. It is one of several drugs being studied that researchers hope will be able to do something that has yet to be accomplished by actually fixing the problem at its root rather than the current treatments that merely control symptoms and slow progression of the disease.
Nonsense mutations are responsible for about 10% of cystic fibrosis cases, and 13% of all cases of another devastating genetic disease, Duchenne muscular dystrophy. This may seem like a small number of people that stand to benefit from PTC124, but for those with nonsense mutations the potential is huge. For now, the only way to access the drug is by participating in the clinical trial but if all goes well the drug may be available to the general public in 2011.