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what patients reported in the placebo group. Vertex plans to discuss the results with regulators, and consider its strategy for verifying the results in the third and final phase of clinical trials normally required for FDA approval of a new drug.
OK, whew, you’re probably thinking that’s a lot of information to process already. But there’s even more context to consider. This new drug candidate, VX-661, is really just one of three different compounds Vertex has designed as a “corrector” of CFTR gene mutations. Last year, Vertex reported similarly encouraging results from a mid-stage clinical trial of another “corrector”—VX-809—in combination with ivacaftor. Those results were compelling enough—showing an improvement in lung function for patients with two copies of the F508del mutation—that Vertex is currently testing the combo in a pivotal clinical trial program that’s recruiting 1,000 patients. Vertex’s scientific hypothesis is that it should be able to help the most patients by pairing a genetic “corrector” drug with a “potentiator” like ivacaftor (Kalydeco), that props open the ion channels on the cell surface, to let water and salts pass through.
Put simply, one drug is supposed to correct the CFTR protein pathway, allowing water and salts to traffic to the cell surface, while another drug props open a channel that enables the stuff to pass through. While Vertex has pushed VX-809 as its most advanced “corrector” drug for cystic fibrosis, VX-661 is next in line, and there’s one more back in the pipeline called VX-983.
VX-661 is from the same chemical class as VX-809, and Vertex’s data says it acts at the same step in the CFTR correction pathway, according to company spokesman Zach Barber. While each drug is different in a chemical sense, they are all striving to reach the same goal, treating patients with F508del mutations.
“Our goal in CF is to help as many patients as possible with combinations of different medicines that act on CFTR,” Barber says. “This could be a dual regimen, like VX-809+ivacaftor, or potentially a future triple regimen, such as two correctors + ivacaftor. Having multiple correctors in development gives us a greater flexibility with how we might be able to combine these compounds to address certain patient populations.”
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