patients with one bad copy of the F508del gene, meaning they are in the heterozygous group. Results from 21 heterozygous patients on the combo therapies are being evaluated, but Vertex said it doesn’t yet have enough data to draw any conclusions.
About half of all cystic fibrosis patients have two faulty copies of the F508del gene while about 87 percent are thought to have at least one bad copy of the F508del gene, Boyle says. So if Vertex can show the two drugs benefit larger numbers of patients in the ongoing trial, and reproduce the findings in another trial, it could potentially benefit the vast majority of the 30,000 patients in the U.S. with the disease. “That’s why this trial is the one we are focused on and a lot of people in the CF community are so focused on,” Boyle says.
Researchers were surprised to see a benefit on lung function from a small study that was designed to primarily assess safety and the amount of sweat chloride ions on the skin—which can be an early sign of a CF drug that’s working. But questions remain. Researchers haven’t yet determined the ideal dosing regimen, Boyle says. And the average absolute improvement in lung function isn’t being released yet, because the study is still preliminary, and researchers don’t want patients to fixate on a number that can’t yet be entirely established.
If Vertex can show that the two drugs can consistently deliver around a 10 percent absolute improvement in lung function—which ivacaftor did—then Boyle says he’ll be “ecstatic.” While a 10 percent absolute improvement might not sound like much, it can make a big difference. As examples, Boyle said 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, Boyle says. 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 says.
Now that ivacaftor has shown that kind of improvement in lung function, the next major question for researchers is what difference it makes in long-term quality of life and survival times. The same would be true for a two-drug combo. And if the two-drug combo passes all its clinical trials, there will have to be a lot of thought given to prices. Ivacaftor, a chronic therapy taken twice a day, costs $294,000 per year per patient, for a disease that young people can live with for many years. Any new agent that extends ivacaftor-like improvement to a much larger population of CF patients is also bound to add significant cost.
But those questions will surely be dealt with in more depth another day. For today, the focus will be on what the interim data says about a promising new treatment approach for CF, and the next steps in development. The company is planning to host a conference call at 8:30 am ET today with analysts and media to discuss the data in more detail.
