The effectiveness of plasminogen was demonstrated by at least 50% improvement of their lesions in all 11 participants who had lesions at baseline, and absence of recurrent or new lesions in any of the 15 participants through the 48 weeks of treatment.The U.S. Food and Drug Administration (FDA) granted the application for plasminogen  orphan drug designation, fast track designation, priority review, and a rare pediatric disease priority review voucher. The FDA granted approval of Ryplazim to ProMetic Biotherapeutics Inc.

References
This article incorporates public domain material from the United States Department of Health and Human Services. External links
"Plasminogen". Drug Information Portal. U.S. National Library of Medicine.
If it is caused by a bacterial infection, antibiotics can be used. If myositis is being caused by a medication, it is important to stop that medication.There are a variety of treatment options available if myositis is caused by an autoimmune disease. Glucocorticoids are often the first choice for treatment. This drug works to weaken your immune system so that your immune system is not able to attack your muscles. This is a type of steroid and can cause a wide array of side effects such as mood changes, increased hunger, trouble sleeping, etc. Another treatment option is a steroid-sparing immunosuppressive agent. This works to also weaken your immune system, but does not cause the side effects that the steroids do. Yet another treatment option is a class of drugs called biologics. Also, intravenous immunoglobulins (IVIg) has also been shown to be effective in the treatment of myositis caused by an autoimmune disease. See also
Myopathy (muscle disease)
Myalgia (muscle pain)
Masticatory muscle myositis (a disease in dogs)
Perimyositis

References
External links
Myositis: NIH

Myositis Association https://www.myositis.org