A Study to Evaluate How Safe Pozelimab + Cemdisiran Combination Therapy is and How Well it Works in Adult Patients With Paroxysmal Nocturnal Hemoglobinuria (PNH) Who Have Not Recently Received or Have Not Received Complement Inhibitor Treatment

To join this study, you must be an adult (18 years or older) with PNH that has been officially diagnosed through special blood tests. Your PNH needs to be 'active,' meaning you're currently experiencing symptoms or signs of the condition, and certain blood levels (LDH level) must be above a specific point.

You also need to be able to attend all the study appointments, whether they are in person or online. It's very important that you are willing and able to get specific meningitis vaccinations, if you haven't had them already, as required by the study plan.

There are also reasons why you might not be able to join. For instance, if you've recently had certain PNH treatments (like eculizumab within the last 3 months, or ravulizumab within the last 6 months), or if you've had an organ or bone marrow transplant. You also can't participate if you weigh less than 40 kilograms, plan to use other PNH treatments not part of the study, or have certain infections.

If you decide to take part in this study, you will likely receive either the new drug combination (pozelimab + cemdisiran) or one of the existing PNH treatments (ravulizumab or eculizumab). These will be given over a period of time as determined by the study. You will have regular visits, which might be in person at a clinic or sometimes done remotely. During these visits, the study team will carry out health checks, take blood samples to see how the treatment is working, and ask about any side effects you might be experiencing. They will also look at how much medication is in your blood and if your body is making antibodies against the study drugs. The total duration of your participation in the study, including follow-up, will be explained in detail by the study team.