Positive trial results boost Vertex

Shares of Vertex Pharmaceuticals Inc. soared more than 55.5 percent in after-hours trading on the Nasdaq stock market Thursday after the Cambridge biotechnology company released positive clinical data on an experimental cystic fibrosis treatment.

Vertex said a midstage study of its VX-661 drug candidate in combination with its approved cystic fibrosis drug Kalydeco “showed statistically significant improvements in lung function” in adult patients.

“These new results provide further validation of our strategy” of combining therapies to develop a portfolio of treatments for patients with different forms of cystic fibrosis, Vertex chief executive Jeffrey Leiden said in a conference call with investors.


The life-threatening disease, passed down through families, causes mucus to build up in the lungs and digestive tract.

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Vertex stock closed down 2.2 percent at $52.87 in Thursday trading. But when Vertex released its clinical data after the market closed, the share price quickly vaulted more than $29.

Robert Weisman

Robert Weisman can be reached at Follow him on Twitter @GlobeRobW.