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physicians in cystic fibrosis also want to know how many patients are getting to the standard benchmarks of improvement in lung function. In this study—again among the F508del patients with two mutant copies, and those getting the highest dose—the two-drug combo excelled. Eleven of 20 patients in that group (55 percent) reached a threshold in which they had at least a five percentage point improvement in lung function, compared with just two of the 21 placebo patients (9.5 percent). Five of the 20 patients (25 percent) reported a 10 percentage point gain in lung function, while none of the placebo patients did that well.
“Five percent is the magic number, that’s what everybody wants to get to. But 10 percent is a huge effect,” Boyle says. When I interviewed Boyle last month about what those numbers mean, he said the outcome can vary depending on how sick a patient is, but it always counts for something important. A person who improves from 20 percent lung function to 30 percent goes from the verge of a lung transplant to having a longer life expectancy. An improvement from 40 percent lung function to 50 percent clearly enables a patient to exercise more. A person going from 50 percent to 60 percent can feel a significant difference when climbing stairs, he said.
Vertex’s stock soared in May when it reported the first interim results from the first 48 patients. It lost some of those gains—and some credibility—a few weeks later when it had to correct its earlier press release. The company said it had mistakenly reported on relative improvements in patients when it had meant to report on absolute improvement.
It was a significant error, and although it made Vertex’s combo drug benefit appear more modest, Boyle says it didn’t change his conclusion about the drug combo. The benefit is still strong, and it was reinforced in this final analysis, which he says clears the way for a pivotal study. He says there is still enthusiasm in the CF community, which should help researchers recruit patients for the Phase III trial coming up in 2013.
The biggest fallout from last month’s correction was some even more thorough than usual double-checking of the final numbers this week.
“It wasn’t just me, but everybody wanted absolutely no chance of a repeat correction,” Boyle says. “We looked at the data upside down, back and forth, sideways, you name it.” While he says investors will focus on the magnitude of benefit in this study, he said it’s probably best not to read too much into the data at this stage. “This is still Phase II, so what we’re trying to do is decide if we are confident that we have a clinical effect at a dose and a level of safety that allows us to move to Phase III,” Boyle says. “The answer to that is yes.”