(Adds analyst forecast, comment; updates share price)
By Bill Berkrot
June 24 (Reuters) - A combination of Vertex Pharmaceuticals Inc's cystic fibrosis drugs succeeded in improving lung function in a pair of closely watched late-stage trials, likely offering a potential new treatment for thousands more patients with the rare lung disease and sending Vertex shares soaring.
The data announced by the company on Tuesday are seen as critically important to Vertex, which is virtually assured of a return to profitability following approval of the therapy.
"The data are good and will clearly support worldwide regulatory approval for this drug regimen," ISI Group analyst Mark Schoenebaum said in a research note. "Worldwide peak sales could exceed $3 billion."
Vertex shares were up 42.3 percent at $94.80 on Nasdaq after the company reported its CF drug Kalydeco in combination with its experimental lumacaftor achieved the main goals of the studies called Traffic and Transport in patients with the most common genetic mutation associated with the disease.
Based on the results, the company said it would file applications for U.S. and European approval for the combination in the fourth quarter.
In the two, 24-week studies of patients 12 years and older with two copies of F508del genetic mutation, the combination therapy led to mean absolute improvements in lung function of between 2.6 and 4 percentage points, which was deemed to be statistically significant.
"(The data) opens up 28,000 F508Delta patients, giving Vertex a multi-billion dollar franchise and essentially a monopoly for years," Maxim Group analyst Jason Kolbert said.
Kalydeco is approved to treat cystic fibrosis (CF) patients with a different genetic mutation that accounts for about 2,000 patients worldwide. It had sales of $371 million in 2013.
About 22,000 CF patients aged 12 and over have two copies of the F508del mutation. Once pediatric trials are completed another 6,000 patients under 12 could become eligible for the treatment.
Lung function improvement was measured by FEV1, or the amount of air a patient can exhale in one second.
The mean relative improvements in lung function seen for patients from baseline measurements was 4.3 percent to 6.7 percent, the company reported.
"On average, people with CF who have two copies of the F508del mutation lose nearly two percent of their lung function each year, underscoring the urgent need for new medicines," Dr. Bonnie Ramsey, lead investigator of one of the studies, said in a statement.
A pooled analysis of data from the two trials also showed significant reductions of between 30 and 39 percent in the rate of pulmonary exacerbations, or acute worsening of symptoms, for those who got the two drugs compared with the placebo groups.
The combination also led to small but statistically significant increases in body mass index. That is viewed as a beneficial as CF patients have trouble gaining weight.
Kalydeco (ivacaftor) and lumacaftor address the underlying cause of CF rather than just symptoms of the disease, in which a missing or defective protein called CFTR results in poor flow of salt and water into and out of cells in the lungs. That causes a buildup of thick, sticky mucus that can lead to chronic lung infections, progressive lung damage and death at an early age.
The two studies involved a total of about 1,100 patients with each trial having two active treatment dosing regimens and a placebo group.
Among those who received the combination, 4.2 percent dropped out due to adverse side effects compared with a 1.6 percent dropout rate in the placebo group. The most common adverse side effects were infective pulmonary exacerbation, cough, headache and increased sputum. (Reporting by Bill Berkrot; additional reporting by Esha Dey in Bangalore; Editing by Bernard Orr and Sofina Mirza-Reid)