The cystic fibrosis gene was found 25 years ago and while scientists hoped to develop new treatments for it, novel drugs are difficult to design and do not work as expected. Two studies now suggest why two therapies might not help patients as expected.

According to the research, the Vertex drug is a combination of two compound types into one. In the two studies of human cells, these two compounds counteracted one another which likely diminished the benefits on lung function. However, the study findings are not conclusive and there remains hope for medications called lumacaftor and ivacaftor (Kalydeco).

"The development of drugs like ivacaftor and lumacaftor is undoubtedly a step forward, but our study suggests that more work will need to be done before we can realize the full potential of these drugs," University of North Carolina assistant professor Martina Gentzsch said.

The data were presented at a 2013 conference where it was a disappointment and surprise to the scientists. Vertex expressed its plans to file the combination therapy for the U.S. Food and Drug Administration's approval before 2014 ends.

Vertex announced two experimental combination drug studies in its late stages which combined an experimental compound lumacaftor and the existing medicine Kalydeco. It reportedly improved lung function by about 2.2 percent to 3.6 percent after six months of treatment, compared with a 0.15 percent to 0.44 percent decline in patients receiving placebos.

The two studies observed patients aged 12 years old and older with a genetic mutation type that causes cystic fibrosis called F508del. The subjects represented around 22,000 people or around one third of all patients around the world. The studies raised doubts when the team tested the medications on epithelial cells and found that Kalydeco reverses some effects of lumacaftor.

"This is consistent with results reported from recent clinical trials that showed meaningful but modest improvements in lung function in patients treated with this drug combination," Gentzsch said. Researchers believe Kalydeco makes water escape the cells to moisten the mucus as lumacaftor helps the liquid get to where it is headed.

The researchers said that other drugs and treatment combinations could benefit patients but future investigation on how these affect different patients could result to more realization as to which treatments are worthwhile.