A Study to Investigate the Efficacy and Safety of Anifrolumab in Adult Participants with Polymyositis/Dermatomyositis .

Summary

This study is conducted to learn more about anifrolumab in patients with polymyositis/Dermatomyositis and also to better understand the studied disease and associated health problems. It is believed that an excess of certain immune system proteins (so-called type I interferons) play an important role in this disease. Anifrolumab is a man-made antibody that blocks type I interferons. Blocking type I interferons with anifrolumab may reduce polymyositis disease activity. Anifrolumab is being tested in this research study as a new treatment for polymyositis/Dermatomyositis.
To learn more about anifrolumab in patients with polymyositis/Dermatomyositis, it will be compared with a placebo. A placebo looks like anifrolumab but does not contain the active ingredient found in anifrolumab. You will receive anifrolumab or placebo during the double-blind part of the study, and you will receive anifrolumab during the open-label part of the study. The study drug will be given by injection under the skin (subcutaneous) every week in addition to your standard therapy for polymyositis.
The main purpose of this study is to see if anifrolumab added to your standard therapy works to improve polymyositis/Dermatomyositis disease symptoms compared with placebo added to standard therapy.
All parts of this study are experimental, which means that anifrolumab has not been fully tested and approved for the treatment of polymyositis/Dermatomyositis by health authorities in any country except for use in research studies like this. Anifrolumab has not been approved by health authorities in any country to be given by injection under the skin (subcutaneous).