Vertex Pharmaceuticals ( VRTX) has pushed its second new cystic fibrosis drug into human clinical trials, the company announced Wednesday.

The drug, which Vertex is calling VX-809, aims to improve lung function in cystic fibrosis patients by increasing the number of defective proteins on the surface of cells in the lungs.

Biotech Select

With VX-809 and Vertex's first cystic fibrosis drug, VX-770, the company is attempting to develop drugs that address the underlying causes of the disease. All drugs used currently in cystic fibrosis only treat the disease's symptoms.

Vertex said Wednesday that it will begin a phase IIa study of VX-809 in patients who have the most common genetic mutation found in the disease. The study will enroll 90 patients and will be designed mainly to assess VX-809's safety, although lung function will also be measured.

Earlier this year, Vertex announced that VX-770 was moving into a phase III study.

VX-809 was discovered as part of a collaboration with Cystic Fibrosis Foundation Therapeutics Inc. (CFFT) to develop novel drugs that aim to correct the genetic mutations that cause the disease. CFFT is a nonprofit drug discovery arm of the Cystic Fibrosis Foundation. Vertex retains worldwide rights to develop and commercialize VX-809 and VX-770.

Cystic fibrosis is a life-threatening genetic disease that affects about 30,000 people in the U.S. and approximately 70,000 people worldwide. The disease is caused by a genetic mutation that results in malfunctioning or reduced levels of a protein on cell surfaces, which results in an imbalance of salt and water. This fluid imbalance in the lungs causes an excess production of lung-clogging mucus, infection and inflammation.

Current drugs to treat cystic fibrosis only manage the symptoms of the disease. The current median predicted age of survival for people with CF is 37 years.

Vertex shares closed Tuesday at $29.32.

Other companies developing cystic fibrosis drugs include Gilead Sciences ( GILD), Inspire Pharmaceuticals ( ISPH)and Novartis ( NVS), according to BioMedTracker.
At the time of publication, Feuerstein's Biotech Select model portfolio was long Vertex and Gilead.

Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.