CAMBRIDGE, Mass. ( TheStreet) -- Vertex Pharmaceuticals' ( VRTX) two-drug therapy significantly improved lung function in patients with the most common genetic mutation causing cystic fibrosis, according to final results from a mid-stage study announced Thursday. The new data on the combination of Vertex's experimental VX-809 and currently marketed Kalydeco are culled from all 109 cystic fibrosis patients in the phase II study and build upon interim results from about half the study's patients released in May.
Based on these results, a pivotal phase III study utilizing the highest, 600 mg dose of VX-809 and Kalydeco in cystic fibrosis patients with two copies (homozygous) of the F508del gene will begin in early 2013, Vertex said. Vertex also said it would conduct "additional studies" of the VX-809-Kalydeco combination therapy in cystic fibrosis patients with a single copy (heterozygous) of the F508del gene based on improvements in lung function seen in the phase II study. Vertex shares are up 65% since the interim results from the VX-809-Kalydeco study were announced, in large part because projected peak sales from the company's cystic fibrosis drug business could reach $4-6 billion. Vertex closed Wednesday at $61.11. From the start of the study through day 56, patients treated with high dose (600 mg) of VX-809 and Kalydeco experienced a 6.7% improvement in lung function compared to placebo and a 3.4% improvement within the drug treatment group. Both results were statistically significant. Over the same time period, placebo-treated patients saw their lung function fall by 3.3%. At the interim analysis announced in May, which encompassed half the patients in the VX-809-Kalydeco study, the placebo-adjusted and within-group improvements in lung function were 8.6% and 4%, respectively. These interim results combined patients treated with three different doses of VX-809. Vertex did not disclose final lung function results from the phase II study Thursday for all patients across the three different doses of VX-809. The company did say that patients treated with the low- and mid-doses of VX-809 plus Kalydeco also experienced statistically significant improvements in lung function compared to placebo although the improvements were lower than what was seen with the highest dose of VX-809.