A Study to Investigate the Efficacy and Safety of Anifrolumab Administered as Subcutaneous Injection and Added to Standard of Care Compared With Placebo Added to Standard of Care in Adult Participants With Idiopathic Inflammatory Myopathies (Polymyositis and Dermatomyositis)

To join this study, you would generally need to be an adult between 18 and 75 years old and have a confirmed diagnosis of polymyositis or dermatomyositis that is causing moderate to severe symptoms. You should also be currently taking treatments for your condition, like oral steroids, at a stable dose. Your overall health would be assessed to make sure taking part is safe for you, and women of childbearing age would need to agree to use contraception.

There are certain reasons why someone might not be able to join. For example, if you have other specific types of muscle conditions (like inclusion body myositis or muscular dystrophy), or if you've had certain serious infections (like recent severe COVID-19, TB, or certain viral infections that haven't cleared up). A history of most cancers, serious lung disease, or conditions causing severe muscle damage not related to polymyositis or dermatomyositis would also prevent participation.

Additionally, if you are pregnant, breastfeeding, or planning to become pregnant or breastfeed, you would not be able to join. Your doctor would carefully review all your medical history to determine if this study is suitable for you.

If you decide to take part in this study, you would first have a full medical check-up to ensure you meet all the criteria. After that, you would be randomly assigned to either receive the study drug (anifrolumab) or a placebo, given as an injection under your skin. You and your study team wouldn't know which one you're receiving at the start.

Throughout the study, you would have regular visits to the clinic for assessments. These visits would involve physical examinations, blood tests, and other procedures to monitor your condition and check for any side effects. You would continue to take your usual prescribed medications for polymyositis or dermatomyositis alongside the study treatment. The total duration of your participation would involve a initial 'blinded' treatment period where you don't know what you're receiving, followed by an 'open-label' period where everyone receives anifrolumab, and then a follow-up period after treatment ends. The exact number of visits and the total length of the study would be fully explained to you.