Vertex Pharmaceuticals Inc. sank the most in three years after the company revised results reported three weeks ago from a study of two cystic fibrosis drugs, saying the combination showed less of a benefit.
A misinterpretation between Vertex and an outside data-analysis firm led to the revision, the Cambridge, Massachusetts-based biotechnology company said today. It doesn’t affect Vertex’s plans to start final-stage trials for U.S. marketing approval, Chief Executive Officer Jeffrey Leiden said on a conference call.
The revised data show the drugs improved lung function by at least 5 percentage points in 35 percent of patients after 56 days, and by at least 10 percentage points in 19 percent of people, Vertex said. Previously, the company said 46 percent of patients gained at least 5 percentage points, and 30 percent improved at least 10 percentage points.
“This is a downward revision, but is still good data, in our opinion,” Mark Schoenebaum, an analyst with ISI Group, wrote in a note to clients today.
Vertex fell 11 percent to $57.80 at 4 p.m. New York time for the biggest decline since December 2008. The shares had risen the most in their history after the earlier results were reported on May 7, and are up 8 percent in the last 12 months.
The medicines studied were Kalydeco, which received U.S. marketing approval in January, and the experimental drug VX-809.
Patients on the combination therapy had an average improvement of 4 percentage points, while those taking a placebo worsened by 4.6 percentage points, the company said today.
The decline in breathing ability for those taking a placebo was greater than in other trials, raising the question of whether the medicines will show as great a comparative benefit in the next phase of studies, Schoenebaum said.
The revision was due to a misinterpretation between Vertex and a third-party statistical analysis vendor over whether the data showed an absolute change in lung function or a relative one, Vertex said.
“This is an unacceptable error and we’re taking steps to fix it and make sure it doesn’t happen again,” Leiden told analysts and investors on a conference call today. The company is still confident “we have an active drug here, and therefore we are continuing to plan movement to phase 3.”
Vertex originally told analysts not to expect a benefit for lung function in the trial, Schoenebaum wrote in a May 7 note to investors. The company indicated it would decide whether to proceed to the next phase of trials based on sweat chloride levels, a different metric, said Jason Kantor, an analyst with RBC Capital Markets, in an April 26 note.
Vertex said earlier this month the sweat chloride results weren’t statistically significant for the combination therapy at this stage in the trial. Improvements in breathing in the study were measured by a metric called forced expiratory volume, or FEV-1. It’s a gauge of how much air a patient can exhale in one second.
The results were from an interim review of 48 patients, and showed safety of the combined medicines was similar for those receiving the treatment and those on a placebo, Vertex said. Full results from the study are expected mid-year.