Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare blood disease where red blood cells are destroyed too soon, causing problems like tiredness and other health issues. This study is testing a drug called pegcetacoplan on kids aged 12-17 with PNH. Pegcetacoplan is a medicine that will be given as a subcutaneous infusion, meaning it goes under the skin using two small needles. This study lasts for about 20 weeks, plus a possible long-term follow-up. All participants will receive the medicine and be trained to take it at home.

• The study involves a 4-week screening, a 16-week treatment, and a follow-up period.
• Participants need two needles for the medicine, but they can do it at home with help.
• Participants must be 12-17, weigh at least 44 lbs, and have PNH to join.

Kids 18 or older, or those with certain conditions like hereditary fructose intolerance, can't join. Pregnant or breastfeeding girls are also excluded. This study aims to see if the medicine is safe and effective for young people with PNH.