This is a multiple-region, randomized, double-blind, placebo controlled, multiple-dose, study in participants with PNH who have clinically evident EVH on a C5 inhibitor (eculizumab or ravulizumab).~Participants will be randomized to receive danicopan or placebo, in a 2:1 ratio for 12 weeks (Treatment Period 1) in addition to their C5 inhibitor (eculizumab or ravulizumab) therapy. At Week 12, participants randomized to receive placebo will be switched to danicopan in addition to their C5 inhibitor for an additional 12 weeks (Treatment Period 2) and participants randomized to danicopan will continue on danicopan for an additional 12 weeks, while remaining on their ongoing C5 inhibitor therapy.~At the end of the 2 treatment periods (Week 24), participants may enter a Long-Term Extension (LTE) Period and continue to receive danicopan in addition to their C5 inhibitor therapy. The Long-Term Extension period will consist of a first year of LTE(Year1) and a second year of optional LTE(Year2).All patients will complete 72 weeks of LTE(Year 1) assessments. After Week 72 (at the end of the first year of LTE), patients have the choice to complete participation in this study or continue to the optional second year (Year2) of LTE.
The main objective of this study is to evaluate the efficacy of danicopan as add-on therapy to a complement component 5 (C5) inhibitor (eculizumab or ravulizumab) in participants with PNH who have clinically evident EVH.