The studies, which ran for 24 weeks, also met secondary goals, including reducing pulmonary exacerbations—or signs of the disease worsening and requiring treatment with antibiotics—and helping patients gain weight, Vertex said. The trials were conducted in more than 1,100 patients ages 12 and older with two copies of a mutation known as F508del.
"On average, people with cystic fibrosis who have two copies of the F508del mutation lose nearly 2 percent of their lung function each year, underscoring the urgent need for new medicines that address the underlying cause of this disease," Dr. Bonnie Ramsey, professor of pediatrics at the University of Washington School of Medicine and a lead investigator on one of the trials, said in Vertex's statement.
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The improvements in pulmonary exacerbations were especially notable, "given the potential for these events to result in hospitalizations, permanent lung damage, and the need for additional treatment with antibiotics and other medicines," she said.
The combination regimens were generally well tolerated, Vertex said. Slightly more than 4 percent of patients on the combination stopped treatment because of side effects, compared with 1.6 percent of those taking placebo.
More than 1,000 patients opted to take the combination regimen after the study ended, Vertex said, underscoring the need for medical options that analysts also noted leading up to the data's release.
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"We can debate what difference each endpoints make on reimbursement/price/uptake, etc.," RBC Capital Markets' Michael Yee wrote in a June 17 research note, "but based on our recent discussion with key opinion leaders, as long as primary hits and the drug is approved, they intend to put all patients on drug."
—By CNBC's Meg Tirrell