Vertex Falls on Cystic Fibrosis Drug Study

Another small study of Vertex Pharmaceuticals' (VRTX Quote) experimental cystic fibrosis drug released Monday showed that the drug, VX-770, improved lung function and was safe.

Shares of Vertex fell 3% to $24.91, however, because results from the latest VX-770 study were not entirely consistent with the previous study released last March.

Despite some questions raised about the latest VX-770 study, Vertex said Monday that it intends to work with U.S. and European regulators to design a pivotal phase III study of VX-770 to begin in 2009.

VX-770 works by improving the function of a particular gene that is known to cause cystic fibrosis when defective. This is game-changing territory in cystic fibrosis research because there are no drugs currently that address the underlying causes of the disease, only those that can treat the symptoms.

The downside to VX-770 is that it may only work for a very small percentage of cystic fibrosis patients who have this specific gene mutation.

The phase II study detailed Monday enrolled 19 patients and randomized them to one of two doses of VX-770 (150 mg or 250 mg) or a placebo. Patients were treated with VX-770 or a placebo twice a day for 28 days, after which their lung function was measured and compared to baseline scores.

Patients treated with 150 mg of VX-770 reported an 11.6% improvement in lung function after 28 days, while patients on the higher 250 mg dose reported a 7.4% improvement in lung function. Placebo patients, meantime, also reported a 7% improvement in lung function, essentially equivalent to patients treated with high-dose VX-770.