This is a dose finding study designed to evaluate the efficacy, safety, and pharmacokinetics of danicopan in participants with GA secondary to AMD. The study consists of a Screening Period of up to 4 weeks, a 104-week masked Treatment Period, followed by an Open-label Extension (OLE) Period starting at Week 104 and lasting for up to 1 year. This study will have 4 treatments arms: 100 milligrams (mg) twice daily (bid), 200 mg bid, 400 mg once daily (qd), and matching placebo.