Why wasn’t the Delta F508 mutation chosen for the Phase 2 VX-770 clinical trials?
Because G551D is already located at the cell surface, these patients have the greatest potential to benefit from treatment with VX-770. Most Delta F508 protein is not at the cell surface and therefore it is unclear whether the patients with this mutation will benefit. The Phase 3 registration program of VX-770 will help determine if it is effective in this patient population. It is possible that Delta F508 patients may need to have the location of their CFTR protein corrected to achieve the most benefit from VX-770. Vertex is developing another compound, VX-809, which is currently being studied in patients homozygous for the Delta F508 mutation. VX-809 is designed to increase the concentration of CFTR proteins at the cell surface.
