That in turn results in respiratory and digestive problems, and exposes patients to complications such as infections and diabetes, with average life expectancy in the 30s and 40s - and historically even lower before advances in drugs that alleviate symptoms. The new therapy targets the most common mutation of the CFTR gene, the Phe508del mutation, which represents around 90 percent of cases. "The results of a pair of phase 3 clinical trials in the Journal and in a simultaneous publication in the Lancet document impressive benefits," Collins wrote in an editorial for the New England Journal of Medicine on Thursday.