A combination of a cystic fibrosis drug and an experimental treatment for the disease, both developed by Vertex Pharmaceuticals, led to significantly improved breathing ability in a midstage study, the company said on Monday.

The data suggested that Vertex could have a multibillion-dollar franchise in treating cystic fibrosis, a life-threatening genetic disorder that affects about 70,000 people worldwide.

Stock in Vertex jumped 55 percent on Monday after the announcement, to $58.12 a share.

“This is very exciting data,” said Dr. Joseph Pilewski, adult cystic fibrosis physician at the University of Pittsburgh Medical Center.

“If this were to bear out in a Phase III pivotal trial it will dramatically impact the treatment options we have for patients with cystic fibrosis,” Dr. Pilewski said, cautioning that the data was preliminary and had not yet been fully analyzed. (Phase III pivotal trials are the last step before seeking approval.)