Paroxysmal Nocturnal Hemoglobinuria (PNH) is a rare blood disorder where red blood cells break down too early. This study is for kids aged 12-17 with PNH. The medicine being tested is called pegcetacoplan. It will be given through a small needle under the skin twice a week at home. The medicine helps to see if it can safely help with PNH.

• The study lasts around 20 weeks, plus extra time if continuing treatment.
• You will be trained to give the medicine at home.
• This study is only for youth not treated with certain other medicines, or those still having symptoms with them.

To join, participants must weigh over 44 pounds and not have certain health issues, like hereditary fructose intolerance or a history of certain diseases. Pregnant or breastfeeding teens cannot join.