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April 19 (Bloomberg) -- Vertex Pharmaceuticals Inc., maker of the cystic fibrosis drug Kalydeco, rose the most ever after the company said the medicine combined with another eased patients’ breathing in a clinical trial.

Vertex surged 62 percent to $85.60 at the close in New York, its biggest one-day increase since the stock begin trading publicly in July 1991. The shares of the Cambridge, Massachusetts-based company have doubled this year.

A combination of Kalydeco, also known as ivacaftor, with the experimental VX-661 improved patients’ lung function by 9 percent and 7.5 percent in the two highest dose groups compared with placebo after 28 days, Vertex said in a statement yesterday. Improvements in breathing were measured by a metric called forced expiratory volume, or FEV-1. It’s a gauge of how much air a patient can exhale in one second.

“The data demonstrate robust, statistically significant” improvements in lung function, Brian Abrahams, an analyst with Wells Fargo, wrote yesterday in a note to clients. “The significant share upside post-market is warranted.”

The study, from the second of three phases of testing generally required for regulatory approval, was done in patients with two copies of a gene mutation known as F508del, the most common form of cystic fibrosis. There is no cure for cystic fibrosis, an inherited disease that causes mucus to form, blocking the airways of the lungs. It affects about 30,000 people in the U.S. and 70,000 worldwide, Vertex said.

Underlying Cause

Kalydeco, approved last year, is the first medicine to target the underlying cause of the disease: a faulty or absent gene called CFTR, for cystic fibrosis transmembrane conductance regulator. Kalydeco alone is approved for patients with a mutation known as G551D, which account for about 4 percent of CF patients.

The use of VX-661, or a more advanced drug, VX-809, in combination with Kalydeco may open up a broader population of patients to be treated, those with the F508del mutation. Half of cystic fibrosis patients worldwide have two copies of that mutation, and an additional one-third have one copy, according to Vertex.

Kalydeco and VX-809 were granted “breakthrough therapy designations” by the U.S. Food and Drug Administration earlier this year, part of the agency’s goal to speed development and regulatory review of potential new medicines for serious diseases.

The 128-patient trial reported yesterday showed that VX-661 was “generally well-tolerated” alone and in combination. Vertex said it plans to do more studies of the drug.

To contact the reporter on this story: Meg Tirrell in New York at

To contact the editor responsible for this story: Reg Gale at

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