Vertex slumps as firm revises Kalydeco data

The USA’s Vertex Pharmaceuticals (Nasdaq: VRTX) saw its shares plunge 19% to $52.85 in early trading yesterday, after the company announced a correction to the previously reported responder analysis, as well as additional data from  the recent interim analysis of an ongoing Phase II study of two cystic fibrosis drugs - VX-809 and Kalydeco (ivacaftor) – which showed less benefit than previously reported, due to a “misinterpretation” of interim data reported to Vertex by its outside data analysis provider.

The results showed significant improvements in lung function (forced expiratory volume in one second, FEV1) among adults with cystic fibrosis (CF) who have two copies (homozygous) of the most common mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, F508del. As previously announced, there was a statistically significant improvement in lung function (absolute change in percent predicted FEV1) across the combined treatment groups relative to baseline compared to placebo (p=0.002).

Yesterday's announcement provides a correction to the responder analysis (n=37) for the absolute improvement in lung function compared to baseline and, for the first time, provides the mean absolute improvement in lung function compared to placebo observed among patients who received VX-809 (200mg, 400mg, 600mg; QD) and Kalydeco (250mg; q12h). The data reported yesterday and earlier this month are based on 37 patients who completed 56 days of treatment with VX-809 and KALYDECO and 11 patients with one or two copies of the F508del mutation who received placebo.