Vertex already sells a drug called Kalydeco, which causes unprecedented improvements in the lung function of patients with cystic fibrosis if it is caused by a genetic mutation called G551D.

FORBES: Personalized Cystic Fibrosis Drugs Get A Booster Shot

But Vertex just announced that the second corrector drug, VX-661, also improved lung function at its two top doses when combined with Kalydeco.

FORBES: Personalized Cystic Fibrosis Drugs Get A Booster Shot