Vertex Falls on Cystic Fibrosis Drug Study

The lack of a dose response in this study (i.e. the low dose performed better than the high dose) plus the fact that placebo patients' lung function also improved, isn't entirely consistent with the VX-770 study from last March in which there was a clearer dose response amongst cystic fibrosis patients and the lung function deteriorated for those patients given a placebo.

Vertex spokesman Zach Barber says the small number of patients in the study -- just 15 patients on VX-770 and another 4 patients treated with placebo -- make any comparisons between groups difficult and help explain a lack of a dose response.

VX-770 is designed to improve the function of a gene that in turn, controls a protein called Cystic Fibrosis Transmembrane Conductance Regulator, or CFTR. Significant reductions in sweat chloride levels, a biomarker for improved CFTR function, were observed in the study by patients treated with both doses of VX-770. By comparison, placebo patients showed no such CFTR improvement.

Investors follow Vertex primarily for its work in hepatitis C treatments. The company's valuation hinges almost solely on the phase III hepatitus C drug telaprevir, which is partnered with Johnson & Johnson (JNJ Quote).

VX-770 is still a relatively low-profile piece of the Vertex story, but Monday's data, plus plans to move the drug into a phase III study, will raise the drug's visibility. VX-770 has the potential to reverse or modify the underlying causes of cystic fibrosis for some patients. Current cystic fibrosis drugs from Genentech (DNA Quote), Novartis (NVS Quote) and Gilead Sciences (GILD Quote) can only treat the symptoms of the disease.