Lung damage used to be thought of as irreversible and if this drug does indeed repair damaged lung tissue then it will be a massive breakthrough and a real beacon of hope to CF sufferers. No mention in the article of whether the tests were on human subjects or laboratory animals - mice are usually used for testing lung treatments. Whatever the outcome, it's nice to know that somewhere behind the scenes there are researchers trying to beat CF - more power, and funding, to their elbows!