Vertex Pharmaceuticals Inc. fell the most in more than four years after releasing combination data on its cystic fibrosis drug that analysts found difficult to compare.
One group of patients taking a combination of Vertex drugs, those with two copies of a gene, improved the most, the Cambridge, Massachusetts-based company said today in a statement. A second group with one copy of a gene mutation also had better lung function, though it was smaller.
Vertex released interim data of the combination treatment in May that it revised three weeks later, saying there was less benefit than initially thought. The revision in earlier data owed to a misinterpretation between Vertex and its statistical analysis vendor, the company said. Today’s announcement is the final data for the highest dose. That’s not quite comparable to the previous data, said analyst Mark Schoenebaum, an analyst with ISI Group in New York, in an e-mail.
“The company has declined to release the comparable data,” Schoenebaum said. “This non apples-to-apples disclosure has created investor doubt that the data are ‘real.”’
Shares of Vertex fell 16 percent to $51.18 at 4 p.m. in New York trading, the most since Nov. 5, 2007.
Data showed that 55 percent, or 11 of 20, patients given the combination of the medicines in the highest dose experienced improvement by at least 5 percentage points after 56 days. That compares with 9.5 percent, or 2 of 21 patients on placebo.
“This is consistent with the interim data provided in May,” said Geoff Meacham, an analyst with JPMorgan Chase & Co., in a note to investors today.
Patients with a homozygous mutation, or two copies of the most-common cystic fibrosis-related gene mutation, improved 8.6 percent compared with a placebo. About 70,000 people worldwide have CF, and almost half carry two copies of that mutation.
“The highest dose arm looks good,” wrote Schoenebaum, in a note released today. He reiterated his “buy” rating on the stock.
The medicine, dubbed VX-809, was studied in combination with Kalydeco, Vertex’s approved treatment for cystic fibrosis patients with a specific gene mutation. Results were from the second of three stages of human tests generally required for U.S. regulatory approval.